Battery revival - how low is too low

[KirstinS]

I've just bought an synergy 36v bike for 50quid

Battery was dead hence the bloke sold - hadn't used in 2 years

With keys and charger

Took battery apart - it has 10 pouch cells of 10ah each at 3.7v they are hard pouches (metal)

Testing the balance lead shows each cell at about 0.75v

Is this too low for a safe revival ? I used a 12ah 3.7v pack to juice up one cell to 3v and then let the turnigy accucel charger take over at 0.5a charge

Seems ok but what are the experts thoughts ?

I'm feeling.cell and it did get a fraction warm when hookup to my battery direct but has cooled down under charge

And I do mean fractional - it was hardly warm at all but others felt cold

 

[Deleted member 4366]

Don't waste your time on it. Even if they charge up, you'll find that they sag something rotten, and they won't have much capacity either. They won't come back to life like 18650s do.

 

[KirstinS]

Well I'm about half way through now. Might as well see what happens !

Thanks though

Guess I can always use the BMS and canister and use a bunch of 18650 cells instead !

 

[Gringo]

My experience with RC & lipo's would suggest they are all but useless.
When they drop that low the chemistry changes, I believe crystals form inside the cell vastly reducing the capacity.
I've had a few packs drop below 2.5v per cell when my low volt alarm failed, like you I zapped them on a high amp Nimh charger 30 seconds at a time,Untill my lipo charger recognized them at the correct cell count.
After that the capacity was reduced and I only got a few more cycles out of them before they started to puff up in use.
If you sit with them whilst charging, you can keep an eye on them.
Should the recover enough to use on your bike it might be worth a go, personally I'd take a fire extinguisher with me, but I'm paranoid

 

[KirstinS]

Thanks gringo

I'm fully baby sitting in paranoid mode !

I want to get to a situation where all cells are up at a level where by I can let the BMS take over

At that point it's going to be charging in the middle of the lawn on a long extension lead !

 

[Deleted member 4366]

Different types of cells behave totally differently. What happens with lipos is not really relevant to your battery, but useful info anyway. I think you've described Phylion cells, which are about 15mm thick cuboid cells. Is that correct?

 

[KirstinS]

That's correct f8veh

I'm sure your right but I've not actually bought the bike yet

Guy gave me the battery and charger

If I can just make it work enough to test the bike that's enough before I part with cash

 

[Deleted member 4366]

I've had about four batteries to repair with those cells. I couldn't recover any of them. You can get them up to 4.2v,all beautifully balanced, but you get about 1aH from them before they sag to LVC. I guarantee that yours are knackered.

 

[KirstinS]

1ah is enough to test ! But yes it's taken hours . And only about 70% done

Clearly not going to be worth the effort

 

[pdarnett]

I got one good one out out my two momentum batteries, same sort of design. I charged to whole pack slowly going up the settings on my imax b6, 2s, 4s etc right up to 22v. then left it overnight, it was still somewhere near so charged each cell via the balance lead one by one. took ages but once done i left if for a few days , rechecked and it was still ok. Bought the proper charger for it and have been using it on my daily commute since!

 

[pdarnett]

The thread was here.. http://www.pedelecs.co.uk/forum/threads/need-some-advice-recovering-some-batteries.16514/

 

[KirstinS]

Thanks for the good news story !

Let's see - working from home today so can keep the recovery going

 

[KirstinS]

Ok all series are above 3v

I plugged BMS back in and put on main charger. Light indicates success in that it is charging so the BMS should have kicked in

I'll slightly terrified though and it really is on charge at the end of garden under an old ceramic planter

 

[pdarnett]

I have a metal bucket for charging suspect batteries in! Ceramic planter indeed, oooh get you !

 

[flecc]

If it's these Phylion cells, my experience is exactly the same as that of d8veh, when they die they stay dead:

 

[KirstinS]

I have a metal bucket for charging suspect batteries in! Ceramic planter indeed, oooh get you !

Hah ! If I eat some hummus with with a rosemary flatbread whilst I wait I suppose that could just about sound even more comically middle class

 

[KirstinS]

If it's these Phylion cells, my experience is exactly the same as that of d8veh, when they die they stay dead:

Thanks flecc

It's all good learning for me

Hopefully it cope just enough to test the motor

Anything else a bonus

 

[Deleted member 4366]

We wait with bated breath. i say that they'll charge up to 4.2v and all sit perfectly balanced, so you should be able to test the motor, but don't ride it to the shops unless you want to pedal it back.

 

[KirstinS]

Well so far you are spot on

I t up 4v per cell, perfectly balanced.

So it's all be stuffed back in the container and put back on charge .to 42.

Very tight on way in and out so may be some puffing of cells (not noticeable to the eye though)

 

[KirstinS]

flecc and d8veh have turned out to be spot on

Who'd have thunk it eh !

The pack held 41.5v and managed about 300 yards before going too low and LVC kicks in. Give it a few minutes rest and it bounces back to 40v

Guess some or all cells are knackered and cannot take any load

Maybe I can use the canister and BMS and build a new pack with 18650 inside

In the meantime I'll test again using 3x 11.1v and 7.4v pack series . Those slung in panniers should make it serviceable for the time being

Looks like these mistrals have a restrict/de restrict connection as well. Presumably leave unconnected for deresrict