AFFORDABLE 15 Ah BATTERY

neptune

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I am re-posting this for those of you who may have overlooked it. Go on Ebay and search 40152 cells. These cells cost about £26 each delivered from conhismotor. You get a better price if you buy more cells. The beauty of these is that you can build a 15Ah battery with just one series string of cells . So 12 cells [ for a 36 volt battery] cost under £300. Add £25 for a balancer charger, which will balance 6 cells at a time . You could use your existing bulk charger, or aquire one with a higher charge rate. So for less than £350 you get a 15 Ah battery that you can repair yourself by changing individual cells, or replacing the balance charger. Its life will be long, because you will seldom use more than say, 80% of its charge . Weight is 480 grams /cell.
Obviously a 24 volt job will be cheaper. I would be interested in what JerrySimon thinks of this.
 

flecc

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Oct 25, 2006
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My reservation is that large capacity lithium cells have not been very successful, formerly common on the short lived batteries of yesteryear. The trend has been towards series/parallel arrays of smaller capacity cells and these have been longer lasting. Examples are:

Panasonic 10 Ah: 2 parallel series of 5 Ah cells.

eZee and Wisper 14 Ah: 2 parallel arrays of 7 Ah cells.

Kalkhoff-BMZ: Arrays of many cells, often around 50, each cell of 2.25 or 3 Ah.

The successful Tesla electric sports car: Over 6000 very small AA like cells.
 

neptune

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@Flecc. What you say is logical. But it does raise a couple of other questions. The first is, in view of the fact that batteries have improved in recent years, is it fair to compare these to yesteryears batteries. The most vital question is this. To develop a new, larger size of cell must involve R&D costs and tooling costs. So the why go to that trouble and expense unless these cells will do a job that can not be done by existing cells, in other words, just what application were these larger cells designed for. If we knew that, we might find some info on how they perform. It is interesting to note that more than 2000 charge/discharge cycles are claimed.
 

cwah

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I wouldn't trust what they say. Look at their ebay rating: 94.9%. It's very low for an ebay seller.

They claimed 1000 cycles on my LiMn2O4 36V10AH battery and I've lost 40% of the battery capacity in 6 months with 100 cycles... And I didn't get any replacement as it's supposed to be "normal"
 
C

Cyclezee

Guest
Hi Neptune,

I assume that this is the eBay seller to which you refer. 3.2V 15Ah Lithium Battery LiFePO4 40152 Cells (1 pc) | eBay

At todays exchange rate, the cost of 12 x 40152 cells delivered to the UK would be £299.30

In theory HMRC should add 20% VAT and 6% import duty taking the cost to £377.12.

I accept that this may slip through customs.

You would then have to build the battery and encase it. I also see no mention of warranty.

In comparison, an eZee 14 Ah battery delivered free within the UK and covered by a 2 year warranty costs £400. http://www.cyclezee.com/shop.html

Personally, I can't see that it is worth the hassle unless someone gets a great deal of pleasure and satisfaction from building their own battery.
 
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funkylyn

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I am re-posting this for those of you who may have overlooked it. Go on Ebay and search 40152 cells. These cells cost about £26 each delivered from conhismotor. You get a better price if you buy more cells. The beauty of these is that you can build a 15Ah battery with just one series string of cells . So 12 cells [ for a 36 volt battery] cost under £300. Add £25 for a balancer charger, which will balance 6 cells at a time . You could use your existing bulk charger, or aquire one with a higher charge rate. So for less than £350 you get a 15 Ah battery that you can repair yourself by changing individual cells, or replacing the balance charger. Its life will be long, because you will seldom use more than say, 80% of its charge . Weight is 480 grams /cell.
Obviously a 24 volt job will be cheaper. I would be interested in what JerrySimon thinks of this.

Neptune....as I have said before.....buying from someone called 'conhismotor' ??
I dont think so......
I think Cwah can confirm the problems he had with this 'firm'.

Surely better to buy in the uk and get a warranty that can be trusted and if it costs a few quid more, so what...... surely peace of mind is worth that ?

And the time you save from not having to 'build your own battery' can be used cycling :D

Simples.....

Lynda :)
 

neptune

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Thanks for the feedback on this. The only other advantage I see in self-built batteries, is the ability to service/repair them. And this is only really feasible if you use a separate balance charger, as per radio control hobby practise. I would be interested to know what percentage of battery failures are due to duff cells, and what percentage is due to BMS failure. I would guess that it is usually duff cells. Replacing individual cells would probably cause problems with cell matching and balance. So given a source of good cells, how feasible is recelling a LiFePo4 Battery?
I know that my area, South Lincs, is not typical, but I would say that more than 80% of the bikes I see are Lead Acid, and are used for utility rather than recreation.
 
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vhfman

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Oct 5, 2008
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Hi Neptune

The Headway LiFePO4 cells are good, but I am not sure I would buy them on ebay. I think you can probably get them cheaper from BMSBattery but that depends on getting through customs without duty being added, as John said.

You can get the 16Ah version in the UK from eclipsebikes @ £22.40 each plus postage. More expensive than China, but easier to get help in the UK rather than returns to China which is out of the question in reality.


in the last few years I have built two 39v batteries with Headway LiFePO4 cells. Both were using the slightly smaller 38120S 10Ah cells. The first set of 12 cells were originally in a battery pack I got from Cyclone TW about 4 years ago. I decided to dismantle the battery which had a built in BMS, as it was unreliable. So I did as you are suggesting, use an external balance charger or a bulk charge method and monitor cell voltage manually. This has worked well and the cells are still working although a couple are beginning to show signs of ageing, possibly the ones that had received an over voltage when the BMS that failed was in use.
The other battery is about 3 years old and I got the cells from EV Assemble. Never used a BMS with these cells and they are still working well. The batteries are used on a system that peaks 2.5-3C(25-30A), but these cells are rated at 10C so can take this current peak with ease.

I have also used the same system as Jerry, making packs with the A123 2.3Ah cells. The A123’s are good for small compact pack building. And again I have made the batteries with no BMS built in. The A123 cells are very well matched and hold up better than the Headway cells.
Building batteries with no BMS built in, does mean that you have to do all the monitoring of cell balance and state of charge. But if you are willing to do that, then the other option would be to use RC Lipo cells which are the most powerful and lightest option for batteries, but unfortunately are the least safe if mistreated and their recharge longevity possible less than half that of LiFePO4.

Chris
 
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jerrysimon

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Aug 27, 2009
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I am a big fan of DIY batteries primarily for the ease of repair as stated.

Not for everyone but certainly have their advantages. If I needed a larger battery I would certainly consider Chris's method detailed above. Use of a BMS can cause more complications than not using one, but as he states a closer eye needs to be kept on balance of the cells.

I am cautious about the use of lipos though I know many use them successfully in this application. I recharge my packs at work and would not be happy about keeping lipos in my house or at work. I have used lipos extensively in my RC hobby days.

PS Looking at that UK supplier if I needed the range I would seriously consider the 10Ah ones as the pricing makes those more attractive. My A123 12s1p packs cost me about £70 to make, so for about double that you could get a 10Ah pack of headways. Would make a very nice DIY pack and I would buy a few spare. Probably worth doing two 6s1p packs in series like the A123 packs to ease balancing ?

Just how much checking do these headway cells need Chris ?

Regards

Jerry
 
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vhfman

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Oct 5, 2008
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Hi Jerry

The Headway are about the same as A123's . I have noticed that a couple of Headway cells do seem to self discharge faster than the rest of the pack. The battery packs after use are pretty well matched cell to cell. I think that the A123 packs hold their voltage better even though they are smaller capacity cells. But that could be down to the fact that they are newer than the Headways.
This winter I have not used the packs for about 4 months but the voltage on the A123 cells was still well above 3.2v. with only occasional checks made by me. I had just got back to riding and using them, when the weather decided to revert back to winter. And now I have fallen down some steps giving me the biggest bruise on my bottom, so too sore to sit on a saddle!

*Warning uncensored BumShot*

Chris
 

Synthman

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Aug 31, 2010
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Neptune....as I have said before.....buying from someone called 'conhismotor' ??
I dont think so......
I think Cwah can confirm the problems he had with this 'firm'.

Surely better to buy in the uk and get a warranty that can be trusted and if it costs a few quid more, so what...... surely peace of mind is worth that ?

And the time you save from not having to 'build your own battery' can be used cycling :D

Simples.....

Lynda :)
Judging by the prices I saw on BMSbattery last night, £300-£350 seems a lot for a 36v 15ah battery. All depends on import duty but BMS might still be cheaper even with delivery.

Also conhismotor is a very funny name. Conhismotor, conmymotor, conyourmotor!
 

jerrysimon

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Aug 27, 2009
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And now I have fallen down some steps giving me the biggest bruise on my bottom, so too sore to sit on a saddle!
Yikes Chris I don't think I have seen a bruise that big before. I hope you recover soon :(

Thanks for the reply.

PS does that sound like I am saying your ass is big ?

Regards

Jerry
 

flecc

Member
Oct 25, 2006
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is it fair to compare these to yesteryears batteries.
The term was relative to the speed of recent battery development, yesteryear referring to as recent as 2007/8. The trend to series/parallel arrays is clearly favoured by the proven best battery manufacturers now. The cell performance seems to be related to the ratio of size and content density, the more density (capacity) packed in, the more difficult it is for charge to enter or leave, this exacerbated as a cell gets larger.
 

muckymits

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May 31, 2011
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I am so glad this thread has come up, as I was about to buy 2 zippy 5000mah. Might go the Headway now. Hobbyking is out of stock anyway :(
 

neptune

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Jan 30, 2012
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Boston lincs
I am glad I started this thread, even if my original idea turned out not to be the best idea. As Linda reminded us, Conhismotor may not be the best supplier. However, some of us boys like to tinker and experiment, it is in our nature. What is really great about the forum is that hopefully, we can learn from each others experience, be it bad or good. What is the general consensus on BMS Battery ?

Also has anyone had experience of replacing individual faulty cells, and how it effects subsequent balancing ?
It is encouraging to know that some people are using batteries with little or no balancing.

@Funklyn. I am sure you often buy a new jumper or sweater, but I bet your favourite ones are the ones you knitted yourself. Some of us boys like knitting batteries!
 
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jerrysimon

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Also has anyone had experience of replacing individual faulty cells, and how it effects subsequent balancing ?
Yep



I made a mistake of not matching the charged capacity of this cell with the others and destroyed it in the process. I then replaced it again and have been running it fine for about six months since I changed it. The pack is about 28 months old now with about 700 charge cycles on it.

PS If you want to get really geeky you can monitor the cells under load. This is how I dientified the dodgy cell. The green line is the dodgy cell seen clearly against the other cell voltages. The other line is the overall pack voltage which is on a different scale.



Regards

Jerry
 
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Synthman

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Aug 31, 2010
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With our talented engineers, power wheelchair experts, DC motor and electronics controller designers, experienced assembly workforce, we are cheap replica handbags confident to provide our valuable customers with top quality products and services at the lowest possible cost.

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I assume the first one wouldn't appeal to Lynda either!
 

flecc

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Oct 25, 2006
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So as well as any other faults, they forgot to pay their translator too. Always a mistake!
 

alban

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May 25, 2011
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I've read about BMS's being less than reliable and consequentl damaging cells. So with a BMS-less pack, say, 2X6s 10AH Headways, what would you need? How would you separate/connect the two packs for charging etc?
Need a LiFePO4-compatible RC Balance Charger that can cope with 6 cells plus Power Supply so you can charge to 3.6V each? How do you actually physically charge them? Photos would be good!
Then how do you ensure they don't get drained too low in use? A Volt &/or AH monitor obviously but is there some kind of simple pack LVC shut-off device or perhaps an alarm? (I think I've seen something on RC sites....)
If it came to replacing a cell would a new one cause problems in balancing even if charged to the same level as the others?
 

jerrysimon

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Aug 27, 2009
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Came across a very nice blog showing some construction details of these.

Regards

Jerry