Battery Pack Building

[Storapa]

Hi Folks,

I have been offered a quantity of IFR26650E 3000mAh 3.2v cells FOC. They were used in project that was cancelled. They have only seen light use, and have been stored since.

Is it worth me considering building a battery pack for 36v motor with them?

Any advice or thoughts would be great.

 

[Deleted member 4366]

They should be OK. Use a 12S LiFePO4 BMS or build them into two 6S packs and use a lipo charger set to LiFePO4. If you do that you'll need a low voltage alarm or monitoring system.

 

[Storapa]

Thanks for the advice.

I think that I have found a BMS - from these guys.

http://eclipsebikes.com/lifepo4-576v-cell-30a60a-p-1042.html

 

[clanky]

Sounds like an interesting project, I'll be really interested to see how you get on because I'm looking at building a 5ah 48v "reserve" battery for my bike with 16 18650's in series complete with a BMS. Do you know how to tell the discharge rate of the cells is - I wasn't sure whether it's related to the ah? It looks like you can get 18650 cells quite cheaply with high ah but they all seem to be for flashlights so I assume they don't have the discharge rate capacity for a bike.

 

[Deleted member 4366]

For 48v, its 12 18650s in series. !6 is for LiFePO4 cells. With even the best 18650s, you'd need at least three in parallel, which would be 36 cells. If you want a small emergency battery, it's best to use lipos.

 

[clanky]

For 48v, its 12 18650s in series. !6 is for LiFePO4 cells. With even the best 18650s, you'd need at least three in parallel, which would be 36 cells. If you want a small emergency battery, it's best to use lipos.

Thanks d8veh, that's really useful advice. I'm just starting to get my head round all the battery technologies - batteries seem to be the key area to study. I'm going to go down the lipo route as it seems the best option. I'm planning to use two 6S 20C 5000mAh packs in series.

http://www.hobbyking.co.uk/hobbyking/store/__9176__Turnigy_5000mAh_6S_20C_Lipo_Pack.html

Is there anything I should look out for?

 

[danielrlee]

Is there anything I should look out for?

Lipo batteries use a fairly volatile chemistry and needs to be given respect, else in curtain circumstances can pose quite a danger. If you use them within certain operating parameters though, they are great little bundles of energy. Make sure you've done your research before going down that route.

 

[Deleted member 4366]

Is there anything I should look out for?

Yes, a lot of big sparks and plasma balls.

Before getting lipos, you need to read up on the dangers. There's loads of good info on Google. Once you understand what can go wrong, they're pretty safe. Basically, you have to manage the charging and discharging otherwise they can catch fire. You also have to handle them reasonably carefully. They can catch fire if you drop them or stab them. Naturally, any short circuit makes fireworks. Don't let all that put you off. Many of us use them without problems.

 

[clanky]

Yes, a lot of big sparks and plasma balls.

Before getting lipos, you need to read up on the dangers. There's loads of good info on Google. Once you understand what can go wrong, they're pretty safe. Basically, you have to manage the charging and discharging otherwise they can catch fire. You also have to handle them reasonably carefully. They can catch fire if you drop them or stab them. Naturally, any short circuit makes fireworks. Don't let all that put you off. Many of us use them without problems.

I've been reading up on various posts on google, here and endless sphere and it does seem that LiPo is the best bet for my reserve battery. My plan, so far, is to use two 6S 20C 5Ah Lipo packs each with a separate low voltage alarm, I'm fairly sure my controller shuts off at 37v but it's best to be safe. As it's only a reserve battery I'm planning to charge each pack separately with a Turnigy 6s Balancer / charger - I've got a steel cabinet to charge them in too.

 

[danielrlee]

My plan, so far, is to use two 6S 20C 5Ah Lipo packs each with a separate low voltage alarm.

Don't leave those voltage alarms plugged in over the long term. They'll drain your packs down before too long, but at least you'll know when they do.