T i m

Excellent. ;-) Yes, agreed and whilst I don't disagree with that in general, it doesn't tally with science and the concept of parallel resistance bridges / potential dividers that these cell combinations could be compared with as I would know it? e.g. Let's say the first R(esistor)4 string is made up of 1.2 ohm in series with .9 ohm, 1.1 ohm and say 1 ohm and that is paralleled up with a similar network at all joints with a *different combination* but identical total resistance, the current (pre bonding the joints) will be *identical* in each leg but the voltages would not be the same at each joint. Therefore, when you also bond the joints (as with paralleling balance leads) whilst the primary current will still run though each leg, other currents *will* flow though the cross bonds as well. I agree with that 100%. ;-) Carrying on being pedantic here (because I think it's important to my POV and hopefully your understand of what I'm on about), I would be happy to concede there would be no current in an ideal world but there would inevitably be some current ITRW and the level of that current down to the power of whatever was managing that 'control'. e.g. What if you had a balancer that had the ability to balance at 10A, then wouldn't that 10A be passing though the balance leads? 'If connected once balanced and only when no other activity was taking place' ... yes. ;-) Yeahbut isn't that assuming that all cells are created and stay equal and therefore the reaction to load will be identical on each and every cell? Don't we accept that ITRW that is rarely the case (even with 'matched cells') so *even* if the balance wires are left connected all the time, some current will flow in the balance leads all the time the packs are charging or discharging? . Even when working with say a 16Ah pack that may have done some work (but still considered 'ok' as a pack)? Wouldn't that mean that it could take *ages* to balance charge a 16Ah pack at 10A and how then would it 'control' the charge into different cells and still charge at anything like that rate, without reasonable levels of current passing down the balance leads? I get the 10A would be passing through the discharge leads but to have any influence on that per cell, wouldn't it have to boost or buck the voltages across each cell and so 'divert' some of that current around the highest cell(s)? Understood 100% again. ;-) Or if you were new to the game and were interested to see what was going on across 3 or 6 packs paralleled up etc? ;-) Hey, I didn't think there was any current flow in the balance wires!! <ducks> ;-) Just for the S&G's I'm going to rig up a bunch of ammeters in the paralleled balance leads and see what I get when I put the packs under some load / charge. ;-) I'll be very happy to report back that I saw nothing (of note) under any charge or discharge condition. ;-) Cheers, T i m p.s. I'm firmly from the 'What you hear you forget, what you see you remember and what you do you understand' camp. Keep an eye out for the smoke mate! ;-)

Excellent. ;-) Yes, agreed and whilst I don't disagree with that in general, it't doesn't tally with science and the concept of parallel resistance bridges / potential dividers that these cell combinations could be compared with. e.g. Let's say the first R(esistor)4 string is made up of 1.2 ohm in series with .9 ohm, 1.1 ohm and say 1 ohm and that is parallel up with a similar network at all joints with a *different combination* but identical total resistance, the current (pre bonding the joints) will be *identical* in each leg but the voltages will not be the same at each joint. Therefore, when you also bond the joints (as with paralleling balance leads) whilst the primary current will still run though each leg, other currents *will* flow though the bonds as well. I agree with that 100%. ;-) Carrying on being pedantic here (because I think it's important to my POV and hopefully your understand of what I'm on about), I would be happy to concede there would be no current in an ideal world but would inevitably be some current ITRW and the level of that current down to the power of whatever was managing that 'control'. e.g. What if you had a balancer that had the ability to balance at 10A, then wouldn't that 10A be passing though the balance leads? 'If connected once balanced and only when no other activity was taking place'? Butbut isn't that assuming that 1) all cells are created and stay equal and therfore the reaction to load will be identical on each and every cell? Don't we accept that ITRW that is rarely the case (even with 'matched cells') so *even* if the balance wires are left connected all the time, some current will flow in tyhe balance leads all the time the packs are charging or discharging? . Even when working with say a 16Ah pack that may have done some work (but still considered 'ok' as a pack)? Wouldn't that mean that it could take *ages* to balance charge a 16Ah pack at 10A and how then would it 'control' the charge into different cells and still charge at anything like that rate, without reasonable levels of current passing down the balance leads? I get the 10A would be passing through the discharge leads but to have any influence on that per cell, wouldn't it have to boost or buck the voltages across each cell and so 'divert' some of that current around the highest cell(s)? Understood 100% again. ;-) Or if you were new to the game and were interested to see what was going on across 3 or 6 packs paralleled up etc? ;-) Hey, I didn't think there was any current flow in the balance wires!! ;-) Just for the S&G's I'm going to rig up a bunch of ammeters in the paralleled balance leads and see what I get when I put the packs under some load. ;-) I'll be very happy to report back that I saw nothing (of note) under any charge or discharge condition. ;-) Keep an eye out for the smoke mate! ;-) Cheers, T i m

Nothing to do with winning or losing mate, it's just this tekky guy trying to get to grips with it all and make what you say fit with what others say, what I have experienced myself over 50 years playing with 'electricity' and what I read on the subject elsewhere? <shrug> It's also a slightly different role to that on say an electric cycle. Like, at 4 knots I have all the time in the world to keep an eye on say 6 battery monitors but may not have the time to get to somewhere safe should the worst happen. Someone running an eBike daily, especially as a primary form of transport may not have the same requirements as someone using them in a boat .. and as part of a hobby rather than just 'transport' as such. Especially so if there are others sharing the same battery carrier (even compared to an eTandem). ;-) They also say the value of advice is what you pay for it ... yet purely from taking advice from and listening to you (and others here) I have already invested a considerable amount of time and money in a energy technology that seems, compared to older solutions (like Lead Acid, Nicad or NiMh) to be quite 'needy' in both cost, time and equipment? That said, I'm still very much looking forward to getting it all setup and running some tests and then seeing if those test make all the money and effort worth it when I'm on the water. I'm very hopeful that it will be the case. ;-) Thanks again for all your help. Cheers, T i m

Playing devils advocate for a sec, how do you know ... have you actually monitored it in practice? Or maybe it's just because you have never melted any balance leads whilst doing so yourself (it may not be they that you 'vaporised'). ;-) Background thoughts ... I believe I have read that you should get all series cells of a battery pretty close to that of another before you join them in parallel 'or excessive currents can flow'? AFAICS, there is little difference between the voltage (and therefore subsequent current) across the main terminals and the voltage difference between cells when brought together in parallel? Now, I understand that once a pair of cells have been paralleled they will balance but those currents can be high? Observation ... if the current between cells wired in parallel are never 'significant' why are they typically wired together using substantial sized conductors when assembled in the factory? After all, if they could get away with lighter conductors they would as they would be cheaper? Question: If you were going to build a permanent 4S12P 96Ah pack from 6 x 4S2P smaller 16Ah packs, would you use the sort of gauge wire you typically see on balance leads used to join the parallel cells together to form each parallel group? Interested minds etc ... ;-) Cheers, T i m

Yes, you seem to differ with AK on that. Understood ... however, what are your thoughts re the potential of some fairly high balancing currents being carried over the often fairly thin balance wires, especially when high loads may be being drawn? I understand this may not be an issues in most cases and ITRW but my question still remains unanswered (e.g. That a parallel cell group would *normally* be joined using fairly heavy duty conductors)? Understood, but if say you did have 6 x 4S2P running in parallel via their main cables, wouldn't you get a more granular monitoring if you had a monitor on each (empty) balance connector (and ignoring any perceived 'complexity' etc)? I know the 'All' value will be the same on all 6 monitors but the sub values might show / protect (alarm) any cell going high or low amongst the others? <shrug> Understood. It's just that (again, ignoring the complexity and only thinking out loud etc ...) the little monitor alarm modules are so cheap ... ? My thought may be that I would prefer to over than under-monitor, especially as I'm testing / learning etc? I ran a storage charge on one pack last night (1.6A) and logged it on LogView. A couple of cells (pairs) were very close and the other two (pairs) were both down (and different). It looked like all the cells had levelled off (after about an hour) and the gap had closed but I don't think the balance function is in action on a storage charge (1010B+)? Cheers and thanks also for the ongoing thoughts, advice and feedback. ;-) T i m p.s. I 'question' things, not because I don't trust or believe what you / people say, but because I want to better understand the subject in general (both theoretical and in practice etc). ;-)

Yes, once they have balanced and assuming there is no charge or discharge activity going on etc. Because I understand that no two cells will ever have the exact same characteristics, there will always be *some* balancing current going on (however small etc). Understood. I didn't want to scrimp on such so bought 6 alarms for my 6 packs. ;-) So how do you monitor for low voltage on the other packs (or do you mean when using it in parallel with other packs)? That's interesting. If you don't run the packs with the balance leads connected I wonder if it is better behaved because of the reduced load (load sharing)? Ok. ;-) Are you saying that's the *best* charge rate for a LiPo (generally) or that's the lowest starting point (up to maximum) simply to save charge time? That brings me back to my question. Whilst I understand they 'can be' charged at 5C, is that better (for reliability, safety, cycle count) than say 1C? On my 1010B+, I think you are right. In the manual it mentions: "Note: The maximum charge power capacity is also limited by input current. The maximum input current of 1010B+ is about 24A," It also shows an optional PSU that is '15V 23A 350W'. https://www.progressiverc.com/media/P350%20Manual.pdf I have generally only charged batteries at a 'moderate' rate, other when racing 12th scale electric cars in the very beginning and using the same 4 x SubC 1.2Ah Nicads that were built into the car! ;-) I think I understand with some chemistries that charging slower creates a finer chemical formation that gives a higher energy density but a lower discharge rate (smaller crystals equal lower surface area). So do you charge that hard simply to give a shorter charge time? I was considering the use of a PC PSU but I might just buy a dedicated one. I only have a 12V 4A laptop style 'brick' on there ATM but do have a 15A 'hobby' adjustable PSU somehere. Ah, this may answer my previous questions then ... Do you have them in any form of fireproof container when you are doing this? That sort of strategy would be fine for me as I generally know in advance when I / we might be going boating. So, as long as I have the time from when I know and when we leave that should be time (keeping in mind the need to keep the batteries attended whilst charging etc). [1] Quite! Hmm, it looks like I'm going to have to get myself at least one more and potentially 'high power' charger. Funds permitting ... a single or dual (with dual you have all yours eggs in one basket)? I guess much of the above could highlight another advantage (for me and this scenario) of lead acid ... as you can generally charge it unattended and it can be left with a maintaining charger connected 24/7 so it's always ready to go? Thanks again for all your thoughts and feedback ... the 'bigger picture' is slowly emerging. ;-) Cheers, T i m [1] Because of the capacity of my LiPo packs I was just thinking of building a charge bunker / box and / or putting a steel charging garden store thing outside so I could leave it all running unattended. (I was also thinking of suspending a large bag of sand in the ceiling so that any excessive heat / flame would melt the bag and have it automatically dump the sand over everything. ;-)

Erm yes, I think you have misunderstood my question. ;-) I was saying if you had say a pack that was (internally, like mine) 4S2P, the P's would be connected together by substantial capacity wires, certainly MUCH more substantial than the conventional balance leads you find hanging out of a battery pack. In fact, I'm not sure the balance leads on my 16Ah packs are any bigger than those I have seen on 1A packs? So, if you make a 4S4P by doing what has been suggested here by paralleling both the power and balance leads, in the case of a large load placed on a big pack, the imbalance between the cells could be significant and so possibly overwhelm the capacity of the balance wires? I noticed with your twin parallel pack, you *didn't* parallel the balance wires and had two monitors etc? Ok. You mean for the same weight presumably? Millions of Milk floats, fork lift trucks and many submarines did / do very well with Lead Acid batteries for many years and a lot cheaper than Lithium (especially then)? ;-) My 'expensive' traction LA is 60 Ah and assuming a 50% DOD gives me 30Ah over 1000 cycles for £200. 3 x 16Ah LiPo cost me about the same (more with p&p etc) and assuming a 'safe' DOD of 80% gives me 38 Ah. http://www.phillipsmobility.co.uk/mk-gel-mobility-scooter-battery-m34-sldg-60ah-576-p.asp The LA is pretty bomb proof and from what I've been reading here about the potential consequences of a single instance of user error on LiPo being 'bad' ... (ignoring the weight advantage of LiPo over LA), is that so great a revolution (for use in a boat specifically)? Don't get me wrong here, I wouldn't have spent what I just have on 6 x 16Ah LiPos if I didn't hope it was to be a good solution ... but I'm yet to be convinced how good it will all pan out ITRW etc. Agreed and I have already played with that whilst testing these 18650 LiIon cells. Yup, then that's fair enough (you potentially treating them as consumables) and sounds a good compromise (lifespan / safety over capacity etc). ;-) Given that I have at the smallest, 38 Ah's worth of LiPo in one pack (3 x 16Ah), would you consider the 1010B+ 'man' enough to manage such a capacity efficiently? Would charging said battery at .1C (3.8Ah) for ~10 hours be considered 'good practice' or should I go .2C or the full 10A (~.3C)? https://hobbyking.com/en_us/multistar-high-capacity-4s-16000mah-multi-rotor-lipo-pack.html I guess the question may be seen in two halves.One being the use of the charger for testing (charge / discharge logging and analysis) and a straight charger for use one I have used the batteries and just need to charge them up again (store or use etc). Cheers, T i m

Ah, 'magic', (as some would see it) like WiFi or Bluetooth. ;-) Noted. Looking as a range of (random) discharge graphs on the net it looks like at 1C, 3.5V could also be considered? True. If cutting off slightly early would be considered 'a good thing' then I'm happy to do it. ;-) Hmmm. ;-( Understood and agreed. Do you think though that if I'm only discharging each pack at ~.3C (15A across 3 x 16A packs) that even 3.5V could be a little low? Whilst waiting for the bits to do some experiments with these packs I've been testing some LiIon cells from an old Toshiba battery pack. Thy were wired 3S2P and the terminal voltages were all over the place and one below 1V. All seem to have recovered (all be it only giving ~1250 mAh down to 3V) and now I'm just doing a self discharge test. Is LiIon just more durable than LiPo? Cheers, T i m

So, more of my bits have come though in the post and I've just soldered some XT90's on my power monitor (like yours). I've also found that there is probably a technique for soldering AWG12 cable into the XT90's to make a general purpose charge / discharge / test cable and practice for making a harness (getting all the strands into the receptacle). I notice you have two monitor / alarms on your (parallel) setup and I thought I remember it being suggested that having a monitor on each pack to be an overkill and that the balance leads should also be paralleled and one monitor applied to that? The only thing that still troubles me with that is then you are trying to use the 2 x 4S as a 4S2P, rather than hefty bus bars forming the 2P part, you just have skinny balance wires? Now, I realise that if all cells are of the exact same capacity and performance, discharging them from the ends of the 4S should see all intermediate voltages of all cells decrease identically but I'm guessing that ITRW that's rarely the case (and hence why parallel cell groups are generally constructed with substantial bus bars)? What I am thinking out loud is that whist I'm guessing I would be advised by some here that say 30A being drawn from across 3 x 4S 16000 mAh packs isn't likely to cause particularly high balancing currents within the balance leads ... but if that's an ideal situation I guess that's how they would wire all parallel LiPo packs of this size and I don't think they do? Anyroadup ... I am still playing with the idea of going 2 x 3 packs over 1 x 6 (depending on the RW capacity of the packs etc) and have ordered 6 x fireproof pouches that should take one pack in each (so IF one goes up it might not take out the other 2 / 5) and it will also help me protect each pack physically as well. Reading around further on Lithium chemistry batteries in general it seems that if you want to prolong the cycle life then restricting the maximum depths of charge and discharge can make a big difference. Now I can't see the number of cycles being an issue in my current application (electric outboard on a boat) so what voltage limits would the panel suggest would be a good compromise between (in order of importance to me) 1) safety 2) best capacity and 3) cycle life on these 16A LiPo packs please? Cheers, T i m p.s. Do I understand correctly that EV car battery packs (like say the Tesla) only give long cycle lives when running the cells between 20 and 80% charge? Take that to 25-75% and you are on the same range as a LA battery (100 - 50%)? However, with a LA it's called DOD but is it called something different when you don't start from 100% charge?

Ok. ;-) Yes, I know, but I'm trying to see how it makes it any 'easier' than using two harnesses mate? After all, electrically they are identical and with harness I don't have to find anywhere to stick the board? Well, assuming 32Ah (2x16) with 25Ah useable then just on speed 3 (without a PWM controller so 15A) would give me a run time of just over 1.5 hours. Now, that could be ok ... but on it's own it's less than we currently get with the single 60Ah LA. Being able to swap out to the next battery (of 3 total) could be a viable solution (compared with just one big one) or more logically with 6 packs, to have the 2 x 3 pack combo so I could use one battery 'out' and the other 'back' and giving me nearly 2.5 hours each way (5 hours run time total). We are getting there. ;-) A disadvantage of not having one big battery is you would probably have to re-charge each 'battery' (say 3 x 16A) separately as it would probably take too long to equalise to charge in parallel and I think I understand that partial discharges are 'better' on the battery than full (for safety and lifespan)? Subject to the maximum weight for any single 'battery' not wanting to exceed say 10kgs (inc any container be it a lunch bag or an ammo box <g>), the ultimate solution would be to have enough battery power in two batteries to be able to cruise all day (as we know we should be able to get back as long as we turn round as soon as the first battery is exhausted). ;-) Don't forget, that is out or goal, We aren't into fishing or the sea (we like to go boating when we want, not when the water happens to be there) and 'spending a day on the water' means exactly that! ;-) Now, it's very possible we might supplement the outboarding with rowing (as the eBikers would with straight pedalling) and possibly, with the outboard and battery stashed away in waterproof bags, some sailing. The last trip we did like that was in the 14' sailing dinghy with a 2hp Yamaha 2/ outboard. We sailed for about 6 hours (Norfolk Broads) but were then becalmed and outboarded back. ;-) Cheers, T i m

. So, if that's where I *will* go wrong (especially at the beginning), why would it be unreasonable for me to try to make things safer if if I choose to? That would be a nice thought. ;-) Ok, just OOI, why would I *need* a balance board for say £25 (for XT90) when a balance harness is £1.65 and the XT90 plugs and some wire just a few quid? I mean what does a balance board give me that a couple of harnesses (where all the battery power leads join in a bigger plug) don't? So why only 4 of my 6 cells OOI? No, no (big) sparks, resettable fuses mate. ;-) Yes, I know how I could do it ... but have you read how I suggested I could do it and ignoring the perceived 'complexity' (that is my problem not yours <g>), what have I suggested that is going to make anything worse or less safe? If this 96Ah solution works as well as you suggest it might I may go for another. ;-) Except ... what sort of power do I assume to have left when the pack suddenly alarms and I'm halfway under a tunnel or passing a weir etc? Why wouldn't I have all 6 packs in parallel, after all, you can easily get Balance Boards, BMS's and power harnesses in combinations of 6, why wouldn't I have them all in place at one time? Ok, the bottom line for me is to have a solution, however 'complicated' it may seem to those who may be more familiar with such things that gives me the most protection, the most feedback and the biggest capacity I can get for say 10kgs. I like designing technical solutions ... I like wiring and soldering ... I like having the most feedback possible and all I'm asking from you guys (with respect) is to qualify if what I'm proposing to do (that will be good for me and part of the interest for me) won't make matters (in a functional sense) worse or less safe? I don't care how complex or complicated it may seem to others, it's what I want to do as part of my learning and fun and none of it is written in stone. ;-) See, I didn't win a IEEE award for 'Technical Innovation' on my home made electric racing bike because I made it simple. What I did was used some new / innovative ideas to make a system that was considered 'good' by some independent observers and that made the system better / easier to monitor using simple stuff in a technical way (in comparison with the other competitors anyway). ;-) [1] Cheers, T i m [1] It was interesting walking round the pits and seeing the vehicles designed and built by others. The carpenters had beautifully crafted wooden machines but the wiring, transmission and steering often left a lot to be desired. Those who worked for high tech materials suppliers used some exotic and expensive materials for the body but often with huge compromises in the rest of the design. The engineering on the engineers machines was often exotic and precise but the wiring was a mess. The electrical engineers had lovely wiring but the (spoked) wheels collapsed on the first corner (etc etc). ;-) I was a motorcyclist and so by running a two wheeler I didn't stress the wheels (spokes) on the corners like the three and four wheelers did. Cycle transmission parts were cheap, light and strong enough without me needing to do any complex engineering (although I did have to make a large sprocket (by hand) for the primary reduction stage). As an electronics support tech I was able to design and build all the telemetry gear using cheap and readily available parts (and ended up with a digital speedo that had a greater accuracy and resolution than a RADAR gun <g>). The lower half of the nose fairing was moulded by me in fibreglass using a bubble windscreen (used on the top half) as the mould. The steel (triangulated) frame with rear swinging arm suspension was once my old bench when I worked at BT, welded up by me in our spare (undecorated at the time) bedroom. ;-) It all took a long time but it never let me down on any race and I enjoyed the building and fettling of it as much as I enjoyed the racing. ;-) p.p.s And I could use my Sinclair C5 as a 'pit trike' for running about between the races. ;-)

Thinking again and please bear with my 'outsider' thoughts on all this (someone who has never played with LiPo or multiple packs in parallel but has been using rechargeable batteries of all sorts for over 40 years etc). On my LA battery I have a 50A resettable fuse on the cable as it leaves the +ve battery terminal. Having a controlled 'weak link' is normally considered a 'good thing' in such situations, especially where the is the potential of very large currents, should a mistake be made or something go wrong. So, I'm replacing a single (as in presentation) 12V monoblock (that I know is made up of 6 x 2V cells in series) with 6 x 16000mAh LiPo packs in parallel that are each made up of 4 cells in series but where the voltage / charge on each cell (< ideally), needs close attention. It has been suggested that I run this new 'battery' with all the power leads connected in parallel (XT90, 6 > 1 harness or XT90 balance board etc) *and* the balance leads in parallel (harness or balance board). Now, I would feel safer adding a resettable fuse in each battery leg [1] (say 30A each) and possibly a 50A jobby in the main output lead (as per the lead acid battery). This would protect both us and the boat and potentially one LiPo pack from the others, should something go wrong. However, if I also have all the balance leads connected in parallel all the time, even if one trip trips, the balance leads may still try to supply fault current and potentially cause other issues (melted balance wires being the least dramatic). So, my (possibly OTT / outsider idea) would be to not run the balance wires in parallel all the time but (as touched upon elsewhere) have them brought out individually to say a DB25F on the outside of whatever container I put the packs in and then I could have different DB25M plug / leads plugged into it, depending on what I'm doing ... 1) Would be a cable connected to a remote box containing 6 x voltage monitor / alarms so I can monitor the performance of each cell as (sort of*) a subset of the entire pack (* all the packs would still be connected in parallel by their main terminals). 2) A 'balance plug' that could contain suitable resistors to allow me to balance the parallel cell groups pre re-charging (as they will all be re-charged in parallel anyway). 3) A charging / balance plug / lead that connects all the balance wires back in parallel and connects to the balance port on my 1010B+ charger. So, once charged I could either disconnect the plug and allow the cells to do their own thing (within the constraints of them still being connected in parallel by the main terminals etc) or leave it plugged in and just disconnect it from the charger (whatever the panel deem the best). I appreciate much of this may be considered OTT by some of the 'old skool' here but I am actually as interested in the monitoring, management and safety of this as a solution as I am it being a solution etc. I feel I would both lean more about how this solution behaves in the real world and maybe prevent some bad situation before it becomes an issue. So, what I would like is confirmation that what I outlined above is in itself not making matters worse (battery function or lifetime) or more dangerous please? I actually *like* wiring stuff up and having flexibility so none of what I have suggested would be a chore to me. ;-) Cheers, T i m [1] As you get on some of the 'better' balance boards?

Qualification: 'When balance wires are interconnected'. ;-) As you might! ;-) Cheers, T i m

'In an ideal world' I'm guessing or I'm not sure what the point of the balance leads would be? e.g. If all cells always charged and discharged equally ... ? Understood. Understood. I've not ordered the balance board yet but did order a balance harness (JST-XH Parallel Balance Lead 4S 250mm (6xJST-XH)) but will order the board soon. Understood If the recommendation was not to leave all the balance leads hooked up when not being charged I was considering presenting all the ends (so 6 x 3 + the pos and neg = 20) on a DB25F and then 'remote' 6 monitor / alarms in a small enclosure that I could keep in front of me. Not because I thought it was needed, just that it might be interesting (to me anyway) and could highlight a weak cell? Cheers, T i m

I guess the problem could exist then if a cell starts to go bad / weak and surrounding cells try to pick up the slack via the balance lead wiring? It might therefore be more sophisticated (for those reasons at least) to have individual monitors, assuming they will alarm for both over and under voltage on each cell? ie. (Without the balancing leads all paralleled up via a balancing board or harness) ... If one cell in one series string starts to go lower voltage, the voltage from the other packs will try to lift it though the good cells in the same string and may over charge them? <shrug> Cheers, T i m

In an ideal world (with all cells identical and all wiring paths equal resistance), I'm not sure you should see anything flowing though the balance leads should you? Ok. That was my thought. The more balanced everything is, (by definition) the less current will be flowing within the balance leads and (again, by definition), the voltage across each parallel link will be the same? Without the balance leads keeping everything in balance, the more chances there are for different cells in each (now isolated, all but the terminal voltage) pack to drift out of line and therefore the greater need for multiple pack and cell voltage monitoring? If the balance leads were of the same capacity as the main output leads you would have a straight S/P pack. So, rather than 6x 4S in parallel, you would have a single 4S6P solution. Well, that's if I've understood it all correctly! ;-) Cheers, T i m p.s. I intend to make up a harness where the harness cable gauge was at least as large as the individual battery leads and all 6 cables would join where it goes off to the load. The load cable would be at least 6x the CSA of the singles (probably a lot lot more). ;-)

;-) I was just thinking the current though each leg of the harness (between each battery and the output Y connector) would be limited by the harness, rather than the battery lead (therefore the harness wiring would be the weakest link, all be it only by a tiny amount)? eg.(and this is just for S&G's etc) Let's say the harness wiring is 12 AWG and that is rated at 10A and the battery leads (between the battery and harness) are 10 AWG (rated at 15A) then you will drop more volts between the harness and the Y joint than the battery and the harness? I think the bit you were talking about was from there to the load (serial bit) so that would, to get the best out of the batteries need to be able to support at least 30A and so 6 AWG? However, in your case the total load would be limited by 2 x the harness so 2 x 10 = 20A (8 AWG). We are probably just at cross purposes though ... ;-) Cheers, T i m

Thanks for that. The idea was to have as large a capacity battery as would still be an advantage weight wise (so ~10kg V 17.5 kg of the LA). The positive spin off was the (as you say) the overall current per pack would be reduced so in my case with the outboard at max speed would be 30/6= 5A / battery? I'm not sure how (or if) you could predict the current between the cells / batteries via the balance leads ... only if you assume a worst case low / high voltage condition on series groups ... ? On speed 3 of 5 the outboard draws 15A and for the same speed I'm hoping to improve that with PWM speed controller (so let's hope 10A). 6 x 16Ah packs in parallel = 96Ah, at 80% DOD gives me ~75Ah and so potentially nearly 7.5 hours continuous running (if my math(s) and understanding are correct)? ;-) So, given that (low) load, would just one voltage monitor be ok (I've ordered 6 as part of the experiment)? Cheers, T i m

Neat. Observation though if I may. The gauge of the (XT90?) plugged harness wire looks smaller than that of the batteries (one especially, although it could just be thicker insulation)? Is this intentional so that the harness melts before the battery wiring? I ask because I need to make my own 6 x 16000mAh 4S harness (from 6 x XT90 to 50A PowerPoles probably because that's what I've already got on the LA battery and outboard) so need to gauge the harness wire appropriately. FWIW, because I am only running 12V and aware that resistance can waste a load of power (even at only ~15A) ... and because I wanted the heavy (17.5kg) LA battery up the bow of the boat ... I wired my LA battery with *very* substantial (200A?) and reasonably long cable so I effectively see the full battery terminal voltage in the stern of the boat, even under full load. [1] Depending on how I use my packs ... 2 x 3 or 1 x 6, I might just have the battery in the stern near the outboard and the spare up the bow or if all one one box, keep it up the bow (as it's still going to be around 10kg (cased)). If it works as hoped (as a 1 x 6) I might invest in a duplicate and then with a PWM controller we may be able to cruise all day. ;-) Cheers, T i m [1] When I designed my electric racing (endurance) 'motorbike' it ran from 25kg (max) and in my case, 2 x 12V SLI lead acid batteries. I had a small DVM acting as my 'dash' and via a couple of toggle switches could display battery A volts, battery B volts, total volts, speed and total current. The speed was a magnetic transducer set over the final drive gear that was coupled to a F to V converter and to the dash (calibrated to MPH using an oscillator and wheel circumference calculations). The current was measured via the voltage drop over the main battery cable so that saved adding a shunt. ;-) My basic efforts one an IEEE award for 'Technical Innovation' but it was a long time ago. ;-) p.s. You may have heard of Cedric Lynch of the 'Lynch motor' fame? I was one of the few to beat him but that wasn't because my machine was better or faster (far from it), I just caught him on the hop. ;-)

Hmm, there are quite as few provisos there in comparison with a lead acid and in general though eh (well, two more than lead acid). ;-) I think you might find that was just condensation on very thin Italian car metal mate. <ducks> ;-) But charge risks aren't something you typically experience at point of use though in an electric boat are they (same with LiPo charging risks of course)? That said ... it sounds like *you* might get some regen charging with your electric outboard when surfing ...! . By 'many' you mean (re using a gel LA traction battery in a boat for an electric outboard) none (as in if you over-discharge a LA battery ... 'nothing bad happens' for example) ;-) The only real risk I see re using my MK LA battery in the boat is getting a hernia carrying it or dropping it though the boat! ;-( Yup, we do that also. ;-) I bet (for a particular meaning of the word 'fun'). ;-) Don't you just love the general public. Why are there never sharks about when you want them ... ;-( Cheers, T i m

LOL! Yes, we have seen the picture of your hand! ;-) Another tech paralleling question if I may ... I'm guessing you shouldn't really leave the balance wires connected (in parallel) when running (S4) batteries in parallel? The reason why I am thinking you shouldn't (but again could be wrong etc) is that the balance wires aren't typically 'man' enough to carry any current that could exist between cells in different packs when under load? <shrug> If they were man enough you would just affectively be running a S/P battery? (Without anything in the balance connector you could also have a cell monitor / alarm on each pack, rather than the battery as a whole (so greater granularity to the monitoring)?) Cheers, T i m

I'm sure you are right, but keeping it in context (and comparing apples with apples), would you say Lithium batteries are *as safe* as Lead Acid (in general)? Yes/No ;-) Again, I'm sure you are right but this really isn't about questioning all the risks but just the comparison between what I already have / do and an alternative. I'm considering any potential *increase* in risk whilst still propelling my boat electrically. Well (and playing devils advocate again here), it (and other things, like tides etc) do stop me from going on such waters and that's why I don't. So, to fully understand my POV (re the risk analysis) you would have to know the environment of how 'we' (because there are generally others in my boat who would have a different POV on what could be considered 'risky' to me) do what we do. Like, if rowing along a slow moving river we wouldn't generally wear buoyancy aids because: 1) We are unlikely to fall in for any reason (we don't stand up or jump around) 2) could stand on the bottom in most places and 3) we can swim. We might however wear them when rowing across a deep lake because of the depth or when sailing when there are real risks of capsize. Anyway and whilst talking of safety and with battery packs that have very low internal resistance and so potentially very high currents available ... if running multiple packs in parallel (where they are connected together all the time), is it common practice to protect each battery leg with a fuse or trip of some sort please (and if not why not)? Cheers, T i m p.s. I've ordered some LiPos, monitors and some more foil to make a hat. ;-)

With respect, I'm not 'getting worked up' about anything, this is a new field for me, we are talking a lot of money and it's not just me on a bicycle on the road (when talking about the on-topic use of LiPo's here) but potentially my family, in a small wooden boat, some distance from the land (in time if not actual distance etc). So, part of my questioning here is playing devils advocate and testing for the 'worst case'. Once I know that I can then work back to a more 'real world' usage but whilst accepting there are (extra, over say lead acid) risks. ;-) Understood. Understood. Depending on the size of the box of course. ;-) Whilst I get your point, I'm pretty sure 4 x 4s 16000mA LiPo packs, even in a small ammo box aren't going to be anywhere near the weight and size of my existing battery! ;-) Understood. That said, I am an electronics / field support tech (BT, Kodak, Datacomms Co) and have been soldering since I was about 7 and pride myself in both the care and neatness of my work. However, I have no issues re using a balance board either. I'm assuming that if I went with 4 x 4S, 16A LiPos ... and was drawing a continuous 15A for 3 hours, the batteries wouldn't suffer from lack of ventilation (cooling)? . That's the sort of practical / real-world advice that I like. ;-) I guess that is like the 'what would I grab first when running away from your burning house'. Ignoring the idea that any reaction could make matters worse, I think once I saw smoke coming from my battery box I wouldn't be worrying about potentially throwing good packs away! <burnt hand picture> Ouch. ;-( Trust me, with 48V (8 x 6V X 200Ah LA monoblocks) and a potentially massive short circuit current available in the EV I've had for over 30 years now, I treat all these things with a high level of caution and respect. ;-) Quite, as I'm sure I will be, once I have some usage under my belt. Until then, I'll be proceeding with caution! ;-) Thanks very much for your help and advice. It's all filed away and fully considered I promise. ;-) Cheers, T i m

Thanks for that mate. ;-) https://endless-sphere.com/forums/viewtopic.php?f=39&t=68245 Cheers, T i m

Or setting fire to your wooden boat / leg / coat / picnic in our case. ;-) Yes, the videos seem to show a rapid expulsion or flame / gas and if allowed to vent away from anything combustible, are fairly short lived and so should be safe. Trap that pressure in a metal container with a rubber seal ... ? I'm not saying it wouldn't be fine or better than having them in a plastic box, just that when you see the HobbyKing 'Batbox', that seems to be more of what I would imagine would be a 'good solution' to the problem. And that brings me back to the safety thing ... it's obvious that LiPo (or lithium in general) seem to be more dangerous and I don't *remember* seeing so many charging / safety products surrounding most other rechargeable chemistries prior to Li? Lead acid batteries have been known to explode but that doesn't seem to be that common from simple overcharging? 'The nature of the beast' I guess and a 'cost' of having so much energy in such a small space? Agreed ... it's a little pocket sized flamethrower. ;-) Yes, you are probably right. ;-) Hey, that's about the only good thing I've got by the sounds of it. ;-( Cool. ;-) Yes, I was amazing at that ... Makes sense. However, we are looking for longer than 400 yard trips <g> and a goal of being able to electric outboard all day. So that would be the likes of the HobbyKing 16A 4S's? Should I get several of those while I can and how sure that I'll not regret it (as it's going to be quite a financial commitment for us)? Another thought that came to mind ... I see they (HK) do a 40A brushed esc for less than 10 quid ... if I stuck a servo tester on the front of it, (or I'd make my own using an Arduino) would I get a cheap PWM speed controller for my Minn Kota / Yamaha? Cheers, T i m