Splitting a 36v 20ah Battery into 2?

[RayB]

Hi,

I am a beginner when it comes to being able to wire up a battery pack. Before I even rip the sucker open and experiment is it even possible to think of splitting a single 36v 20ah battery into 2 36v 10ah batteries? I no longer need the capacity and want to lighten up the pack and use the 2nd one on my wifes bike.

I am thinking all I would really need is a 2nd BMS and some knowledge to do this. Where could one start in order to understand how to wire up a lifepo4 pack in this manner. I have looked at some video tutorials on youtube but would like to find a good resource for it if anyone knows of one.

Many thanks,

Ray

 

[dogman dan]

You might be able to work a second job and buy a 10 ah battery in less time. It's possible with pouch cell packs that have 5 ah pouches. The chances of tearing a tab on some of the pouches in the dismantling is pretty high. If it's a round cell pack, your chances of sucess are about 1%.

Your battery might last at 20 ah, but be too small to last as long at 10 ah due to the higher c rate of the discharge anyway.

 

[RayB]

Ok Thanks,

I am not sure what a second job has to do with things But, as I mentioned one of the reasons is I want to make my pack a little less bulky so figured with my spare motor why not just split the battery into two separate units and throw one on my wifes bike.

I have no problem buying a second battery if I wanted. But the fact remains I still have this brick of a 20ah.

Given the time factor etc I dont really mind learning new things so was just looking for basic info on where people have learned to build their packs.

 

[dogman dan]

Just my way of saying that it could take a LOT of time to split the pack and the chances of ruining it is high. It's just about impossible to do with the spot welded packs with more than 100 cells. Lots of folks have damaged pouch cell packs unsoldering them. If money is not an issue, then buy a second pack.

Besides, 36v 20 ah is the right size in 2c cells. If you want another pack with the amps to do higher c rates in a smaller size, look at the headway packs at EV components. I have and will continue to advise running 20-25 amp controllers on a minimum of 15 ah of 2c rated cells. If you have a low wattage motor, then 10 ah is fine.

10 ah of inexpensive 2c rated cells is not going to last as long(with a 20+ amp controller) if you ride has lots of stop signs or any hills. So keep your 20 ah pack intact. If you want a tiny pack that can hack it, its the headways, A123's, or lipoly.

 

[docnjoj]

Hey RayB
I'm in the process of making a former 48 v 20 ah Ping into a 36 volt 20 ah due to some damage to 2 sets of cells that died. In the 48 volt V2.0 like mine it easily splits but into 2x24 volts. It is a lot easier to just cut the circuit board tabs than to try to get individual cells out and resoldered. If yours are actually 36 v 10 ah groups it is fairly straight forward but if it is like mine you could have 2X18v 20 ah sets and it makes it much more challanging. Also dogmans point about the 10 ah being much more stressed is quite valid. Have you opened your battery up yet? There is a thread on Ping surgery and a great .PDF file from biketrials on how to do it!
otherDoc

 

[dogman dan]

Much easier to make a 36v into two 18v packs, like to put in panniers to carry. He wants to split a 36v 20 into two 36v 10 ah packs. He'll just about have to completely unsolder all those cells without tearing a single tab. good luck buddy. I hate to be so harsh, but it's a stupid idea. Like a 15 pound battery is such a burden. Hey why not really lighten up, lose the motor, and ride a bike that's 30 pounds lighter.

If the pack was damaged, it would be a whole different story. Do whatver it takes to salvage some cells. But don't slice and dice a perfect good battery.

 

[RayB]

Well thanks guys. I will have a read of the ping thread.

As far as the idea being stupid, well, in all honesty that was what this thread was to determine. Not sure about the mention of so many cells to rip apart. I have not opened up the pack as of yet but it appears to have only 12 cells and I had thought they were of the type that you bolt together, I wasn't aware there was also welded tabs on these types to also deal with. i.e. its not a battery pack made up of the dozens of small cells you see sometimes. And as far as just dealing with the weight, well, I already have a road bike that I use for that purpose. My commute is 18 miles each way and the ebikes purpose is to faciliate those days when my health issues kick in. But thats besides the point. I was simply looking for a way to utilize one large battery as two smaller ones as I already have two motors etc.

Guess its not going to be possible.

 

[graemebc]

Maybe a picture of one of the batteries?

 

[MrKang]

Easiest and most affordable way to do this is to sell your 20Ah pack and buy 2 10Ah packs
as mentioned..you will probably kill your excisting ping pack if you decide to modify it into two 10Ah packs due to the soldered cell tabs which are
difficult to welt together again.

just play it safe before you decide to curgically disect your ping pack.

 

[dogman dan]

No doubt if you've digested the repair thread you understand now. Each cell is 4 pouches. the whole top of the pack is one big solder. So to split the pack into two seperate 36v packs, you have to break each cell into 2 pouch cells. It can be done, and maybe easy , by a person with some experience and a really good soldering set up. But I know if I tried it, I'd end up tearing the tabs off cells, ruining them for good. Between the bms and the soldering tools, you might spend hundreds on it.

Again, sorry to come on so harsh, but to tear into a good functional battery aint worth the time, money, or risk. A different story if you have the experience and tools already or the battery is damaged.

 

[docnjoj]

I agree that one should not do surgery on a working pack. I had no choice and will go with 2x18 volts since this was the easy way out. My V2.0 pack has 5 cells per 3.7 volt 20 Ah section, so it would be a true nightmare to unsolder and resolder them. Those little tabs are kinda fragile. I'd get new batteries and keep this one as a backup. JMHO
otherDoc

 

[dnmun]

it is not that hard to unsolder the old ones and resolder new ones. it is easiest to cut the subconnector pcb out and work separate from the pack and then you can cut the old tabs off with scissors, and while the pcb subconnector is hot from the soldering iron and the solder is liquid, you can whack it on the table and that knocks all the old solder out of the slots so you can then pull out the old tabs. then put the new tabs through the empty slots and resolder. then resolder the subconnector back in series with a short wire jumper across the section of the pcb subconnector you had to cut originally to get it out.

 

[Lyen]

Easiest and most affordable way to do this is to sell your 20Ah pack and buy 2 10Ah packs
as mentioned..you will probably kill your existing ping pack if you decide to modify it into two 10Ah packs due to the soldered cell tabs which are
difficult to welt together again.

just play it safe before you decide to surgically bisect your ping pack.

I second that it is much easier to sell than do the modification yourself. If you are interested to trade with someone just make another post under the item for sale. I have a 36V 10Ah, a 36V 5Ah, 2 x 48V 40Ah, a 48V 20Ah, and a 48V 10Ah Lifepo4, 3 x 36V 10Ah Nimh, tons of 12V 10Ah SLA, 9 x 36V DC9360 A123 packs. Maybe I can trade you with a 36V 10Ah or something.

 

[RayB]

I second that it is much easier to sell than do the modification yourself. If you are interested to trade with someone just make another post under the item for sale. I have a 36V 10Ah, a 36V 5Ah, 2 x 48V 40Ah, a 48V 20Ah, and a 48V 10Ah Lifepo4, 3 x 36V 10Ah Nimh, tons of 12V 10Ah SLA, 9 x 36V DC9360 A123 packs. Maybe I can trade you with a 36V 10Ah or something.

Yes, that is a great idea and I would be up for probably trading and or selling this. I had already thought of selling prior to posting this thread. Just that the consideration is I live in Tokyo and shipping 25lb batteries to North America is not the cheapest I have sold a few pieces of my previous ebike kits over the past year and I usually end up taking a hit on the shipping vs what I ask for in compensation from the buyer. Which is to be expected I guess considering where I live.

Perhaps I will just post a trade/sale thread prior to my next visit back to Canada around June. Probably the best approach. If your up for trading around that time frame we can certainly chat. With my luck though I would get thrown in the clink after getting off the plane with something like a lifepo4 battery that size.. mmmmm not sure if I can even take it... doh

 

[Lyen]

RayB, I think I have a more realistic solution for you if your intend is to split the pack so you can enjoy riding ebikes with your wife. You may want to consider using the Trial-Gator and attach both bikes and utilize the power from your first bike and pull your wife along on the second bike behind. This way, you can have both the capacity, range, and ability to ride together. I actually bought one myself and attach my wife behind me. LOL See below:

 

[kilowatt]

I have experience splitting a Cammy_CC 36 volt 20 amp cylindrical cell pack in two. It was actually Two 12S19P (18Volt) packs series connected and folder together into one big brick. I ruined the pack. End of that story. I asked Ping battery if they would split packs for all of us so we can use panniers and they said yes with an extra 10-15 dollars added shipping. Here is the email:

Hi Dave,

Thanks for your email.
Yes, we can make it into two equal parts.
Yes, battery and BMS leads will be a little longer. Usually, we don't recommend the leads between the two parts to be longer than 700mm.
Actually, we have made many such packs. We offer custom make services and can change the shape for you if the size of the cell allows.
We won't charge more if they're just two equal parts and shape is not very special. But there will be about 5-10usd extra shipping cost for the two parts configuration.
We're going to list the split option on our web site.

Best regards,
Ping

So, I'm going back to SLA for now until I can afford a new LifePo4 and will have Ping build it.

Kilowatt

 

[RayB]

RayB, I think I have a more realistic solution for you if your intend is to split the pack so you can enjoy riding ebikes with your wife. You may want to consider using the Trial-Gator and attach both bikes and utilize the power from your first bike and pull your wife along on the second bike behind. This way, you can have both the capacity, range, and ability to ride together. I actually bought one myself and attach my wife behind me. LOL See below:

Hi Lyen,

Interesting idea but not the way I probably would go about things. The whole reason for considering the lowering the capacity of my pack was I mostly peddle to work anyways and have previously been fine on a 10ah pack. When I ditched the cyclone kit and went with a hub motor I purchased the 20ah when my health went a bit funny. The ebike is only for the days I dont feel like riding the road bike. Keeps me off the trains

Anyways, since I had the extra capacity and a spare hub motor I figured I would just slap half of it on my wives bike for the sake of it. But that being said perhaps in the summer I will just buy a small 10ah pack for her bike and when we do ride together and I use the road bike she can have more fun keeping up lol.

I also like the idea of splitting the battery to hang over the rear rack. I have been stuck using a clunky rack for this thing just to hold it due to size. I would love to have it nicely mounted to my nitto rack but thats another thread.

Again thanks for all the suggestions I think the topic is closed.

Cheers