12 volt 20ah lithium battery ?

eHomer

Esteemed Pedelecer
Aug 20, 2012
635
163
High amperage lithium battery packs seem to be readily available now in 24, 36, and 48v.

I'm looking for a 12v one, with a capacity of 30ah

I'm theorizing that it should weigh and cost about the same as a 36v 10ah pack, with BMS and charger, but with the cells connected more in parallel than series ?

Does anyone know where I could get one with that spec, either Lipo or Lithium Ion ?

My interest is twofold. One would be to occasionally supplement my 36v 10ah lithium bike batteries to give 48v.

The other main reason though, would be to power my 12v mini electric outboard on my kayak. I currently use a pair of 12v 14ah SLA batteries in a bag wired in parallel, to give 28ah, though that ends up as about 15ah because of the 50% discharge cycle.

It strikes me that the big lithium advantage with ebike technology would be just as useful with the kayak motor. Lighter, longer cycle life, and a full 30ah instead of 15ah.

Of course, compared with padding, it is "cheating" !! :)

mini electric outboard.jpg
 

eHomer

Esteemed Pedelecer
Aug 20, 2012
635
163
I forgot to post the links to the ones I'd found so far:

The cost seems exponential as the ah goes up !

"KDQ7 EU plug 9800mAh DC 12V Super Rechargeable Lithium-ion Battery SPC-2261"
£17.18 from China
http://www.ebay.co.uk/itm/KDQ7-EU-plug-9800mAh-DC-12V-Super-Rechargeable-Lithium-ion-Battery-SPC-2261-/400584675790?pt=UK_ConsumerElectronics_Batteries_SM&hash=item5d44b511ce

"Deben Tracer 12v 10Ah Lithium Polymer Battery Pack - Ideal For Telescopes"
£132 from Sheffield
http://www.ebay.co.uk/itm/Deben-Tracer-12v-10Ah-Lithium-Polymer-Battery-Pack-Ideal-For-Telescopes-/191026949139?pt=UK_Photography_Telescopes&hash=item2c7a17ec13

"TRACER 12v 22Ah Lithium Polymer Battery Pack"
£185 from Swindon
http://www.ebay.co.uk/itm/TRACER-12v-22Ah-Lithium-Polymer-Battery-Pack-/390744870179?pt=UK_SportingGoods_Hunting_ShootingSports_ET&hash=item5afa358d23

Looking at the last one (the 22ah one), the maximum continuous current draw is shown as 10amps, which is below my bike's 15 amps, so I guess that's going to be a factor why a 30ah will be needed, to get it up to 15 amps continuous ?
 
D

Deleted member 4366

Guest
The top one on Ebay is not 9800maH. It'll be about 2aH, and ale to give about 2 amps.

I think your only real chance is a motorbike one, but they're very expensive.

http://www.lithiumion-batteries.com/products/12v-20ah-lithium-ion-battery/

For my electric outboard, I nicked the 18650 cells from an ebike battery and reconfigured them from 10S4P to 3S13P. Then I added 3S balance leads so that I can use a standard imax lipo charger to charge and balance them. I use a lipo alarm to monitor it in use.
 

Geebee

Esteemed Pedelecer
Mar 26, 2010
1,256
227
Australia
If it's a standard 18 lb thrust current draw will be 15 amp'ish, most misc. packs wont deliver enough current.
I have comptemplated doing it with the electric outboard I have but I would just use Hobby King LiPo's.
 

eHomer

Esteemed Pedelecer
Aug 20, 2012
635
163
Thanks for the replies.

Yes Geebee, it is the Rhino 18lbs thrust, so that makes the continuous amp draw standard with the bike then, at 15 amps.

Dave, yes the 12v 20ah motorcycle lithium battery in your link does sound expensive at $289.

I started looking at lithium motorbike batteries on ebay though, and found a very attractive spec one, "Shorai Lithium Iron Extreme-Rate Battery LFX36L3-BS12" on ebay at http://www.ebay.co.uk/itm/like/390723288643?hlpht=true&ops=true&viphx=1&lpid=95&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=95&ff19=0

Once again though, here in the UK we get the worst deal. In the US it's the equivalent of £196.84, and the postage is very reasonable at £15 from the US, but then we get that dammed import duty of £58, bringing it up to £270.

The cheapest UK price I could find for it is £315 !! from http://www.carrotcycles.co.uk/index.php?_a=product&product_id=1648

Price hikes like that aren't helping the UK ebike sales either...
 

eHomer

Esteemed Pedelecer
Aug 20, 2012
635
163
Thanks for the links Frank.

On a scale of one to ten, my Lifepo battery building knowledge is currently at about "A"... :)

The ready made battery "A123 ANR26650" is 6.9ah, so too low a capacity for what I had in mind, unfortunately.

The individual cells "Headway LifePO4 40152S 15Ah" look much more promising, I think, if I understand it correctly.

So to make up a 12v 15a/hr battery using 4 , would give a volt range of 8 volts discharged to 12.8v nominal ?

Would the majority of the usable 15ah capacity be 12v minimum, like an SLA battery ? Or would it be steadily going down to the 8 volts ?

So would the "12V LifePO4 BMS (14.4V) 4 Cell 50A/120A" then control them for discharging and charging, just requiring a case for it and the 4 cells ?

So, that would be £40 for the BMS plus 4 x £20.48 = £82 for the cell ?

So the totals would be either £130 for a ready made 7.5 ah battery,

or £122 for the 4 cells and BMS to make a 15 ah one ?

Please excuse my ignorance on this...
 
D

Deleted member 4366

Guest
3S lithium-ion (not LiFePO4) is 12.6 fully charged and 9v empty. You could probably use 4S for 16.8v charged and 12v empty.

4S LiFePO4 is 14.4 fully charged and about 9v empty, which is closer to lead-acid.

I think 4S lipo looks attractive. I just ordered three more of these for £50 including postage:
http://www.hobbyking.co.uk/hobbyking/store/__26801__Turnigy_5000mAh_4S1P_14_8v_20C_hardcase_pack_UK_Warehouse_.html

one of these might be useful too so you can have up to six in parallel:
http://www.hobbyking.co.uk/hobbyking/store/__45752__JST_XH_Parallel_Balance_Lead_4S_250mm_6xJST_XH_UK_Warehouse_.html
 

eHomer

Esteemed Pedelecer
Aug 20, 2012
635
163
I had a look at the Hobbyking website when Geebee mentioned it, but I couldn't understand the individual bits and pieces. My grasp of battery technology is still at integrated pack level, with bms inside etc.. I can understand the complication with lithium to monitor and charge cells individually, even though the output is with them in series to reach the required voltage.

Dave, the links you gave took me to a parallel balance lead and a 14.4v 5ah "hard case" pack for £18.25, weighing 598 gms.

Do you mean they can be externally connected in parallel, to boost the Amp/h ?

So 4 would give 20 a/h ? How does the balance lead work ?

can they be fastened together as a 12v pack with permanent connections, just like a ready made 36v ebike battery with integrated BMS, and permanent outlet and charging sockets ?

Apologies for the basic questions, but I've been reading the expressions like "10S4P and 3S13P" without really understanding them yet.
 
D

Deleted member 4366

Guest
10s4p means 4 cells side by side, 1o in an array, so 10 x 3.6v = 36v; 4 x 2.5 aH = 10aH, so 40 cells in 10s4p = 36v 10aH. 3S13P means 3 x 3.6V and 13 x 2.5 aH, so 10.8v and 32.5aH.

Those hard packs are 4S1P. Each cell is 5aH and 3.6v, which makes a 14,4v 5aH pack. 4 packs side by side would give 4S4P so 14.4v and 20aH.

to wire 4 packs up, you need to join the balance leads from each pack plus all the lack power wires together and all the red power wires together. I can give you a schematic if you want to have a go. Once the four bricks have been joined, they behave as a 20aH single 4-cell brick, so you can charge them all together. You need a lipo balance charger (about £20) and a lipo alarm (about £3), which will beep when they get too discharged, and it'll also show pack and cell voltages so that you can see how they're going. It's not nearly as difficult as it all sounds. The charger becomes the BMS for charging, and you become the BMS for discharging.
 

banbury frank

Banned
Jan 13, 2011
1,565
5
Hi you need

1 X Bms

1 x Charger

and 4 X cells to make a 15AH pack or 8 to make 30AH pack or 16 to make a 60Ah pack the headway cells have screw ends so no soldering onto the batteries for a small charge Eclipse may make it for you try them

Frank
 

eHomer

Esteemed Pedelecer
Aug 20, 2012
635
163
Thanks chaps, the mist is clearing a little. :)

So the "S" and the "P" are abbreviations for series and parallel connection, to add the cells for either voltage or current.

So the thin ribbon connectors allow the BMS to monitor each individual cell (whether connected in parallel or series) for safe charging individually, even though the complete pack is permanently wired up for a given Voltage and A/H output ?

I like the idea of the screw connections on the cells, avoiding spot welding etc..

Is there a simple Internet page anywhere with clear pictures using proprietary parts showing typical setups ?
 
D

Deleted member 4366

Guest
I don't know whether this helps:
how to make a 44v 10aH battery from four 6S1P bricks. The principle is the same for other battery/rick combinations:



This shows how to wire up a 10S4P battery out of 40 3.6v 2.5 aH cells. It would be the same for a 10S1P battery from ten 3.6v10aH cells:

 

eHomer

Esteemed Pedelecer
Aug 20, 2012
635
163
Thanks for sorting out those diagrams Dave, it's much easy to understand graphically.

I've also just bought this book, which covers a lot more gaps in my knowledge:

I would image many people on this forum will know about it, and I'm interested to know what the opinions are on it.

ebike book.jpg
 
D

Deleted member 4366

Guest
I've never read it, but I can't see how a book can be relevant in a fast moving technology. Some important info must be out of date. Is there a section that explains the advantages of cassette motors?
 

eHomer

Esteemed Pedelecer
Aug 20, 2012
635
163
I've never read it, but I can't see how a book can be relevant in a fast moving technology. Some important info must be out of date. Is there a section that explains the advantages of cassette motors?
I quite agree Dave, that ebike and battery technology is going to quickly outdate any books on the subject, but it's not too outdated yet, (IMHO).

True, I can't find anything about cassette hub motors, but it's making quite a few things much clearer to me, at my (hopefully) medium level of knowledge on the subject.

Here's the Amazon page on it, where you can view some of the pages, including the very detailed contents pages:

http://www.amazon.co.uk/Build-Electric-Bicycle-Green-Guides/dp/0071606211/ref=sr_1_1?ie=UTF8&qid=1390343723&sr=8-1&keywords=build your own electric bicycle
 
D

Deleted member 4366

Guest
If it gives some people the confidence and knowledge to fit even an out-of-date kit, it could justify itself.
 

neptune

Esteemed Pedelecer
Jan 30, 2012
1,743
353
Boston lincs
Can someone please explain what a casette motor is, how it differs from other motors, and what are its advantages and disadvantages?
 
D

Deleted member 4366

Guest
Simple. It has the spline for cassette gears, so if you have a nice bike with cassette (free-hub) gears already, you can use your existing gearing whatever it is. The non-cassette rear motors have a thread for free-wheel gears, which is what they put on cheaper bikes. There is normally only enough room for 7 speeds, and it's not easy to find one with a top gear less than 14 teeth, which means that you can't pedal fast enough to keep up with the motor. Those in the know. know where to get a DNP free-wheel gear-set, that has 11 teeth on the top gear, which is much better, but costs at least £25 on top of the price of the motor, and they're nowhere near the quality of a decent Shimano Cassette. If you have a 9 or 10 speed bike and you go down to seven speed ecause of the free-wheel, it'll mess up your gear changers. The indexing will be wrong, so you might have to buy new changers and derailleur. You can usually make your present ones work, but smooth accurate gear-changing will be a fond memory. The only downside of the cassette motors is that you have to dish the wheel a bit more to get the rim central, which is not a big deal.

In summary, if you have a cheap bike with seven-speed or less, there's no point in having a cassette motor unless you want better gear-changing and you want to upgrade it all. If you have a nine or 10-speed bike, a non-cassette motor will downgrade your gearing.