Lithium batteries

[KEN OPENSHAW]

Hi
Have been offered A ebike with a 575 ah battery but it’s been left discharged for just over 12 months, will it be recoverable?

 

[tommie]

I would check the spec of that battery again for a bit more detail.

What`s the ebike model?

 

[KEN OPENSHAW]

Wisper 705 se LS

 

[wheeliepete]

Very difficult to say, lots of variables, age, state of charge when left, type of cells it's built from and quality. Best thing is take a volt meter with you and measure voltage of battery. If it's under 30v, I would deff. allow for a new one even if it takes a charge.

 

[wheeliepete]

I think it is sometimes better to value the battery on a bike like that as scrap. If you get a bit of life from it great, but otherwise you have a large outlay for a new battery on top of any other money a second hand bike may need spending on it.

By the way I think the battery is 16 Ah, 575 Wh.

 

[Nealh]

As last post regard battery as useless pay what you think the bike is worth, entirely up to you.

 

[flecc]

Wisper recommend their batteries out of use should be topped up monthly. At a year neglected it's unlikely to be satisfactory.
.

 

[KEN OPENSHAW]

Thanks all

 

[Wisper Bikes]

Hi Ken, if the battery is a 575Wh it is likely that the battery is in hibernation mode. If the battery was fully charged when stored the battery is probably OK. If you take the battery to a decent ebike shop preferably a Wisper dealer. They will fully charge the battery and test the Voltage. If the Voltage is above 41V you are probably OK. You should expect to be charged for the battery test though.

All the best, David

 

[KEN OPENSHAW]

Hi David.....41v thought the batteries where 36v

 

[flecc]

Hi David.....41v thought the batteries where 36v

The 36 volt is nominal, based on the nominal cell voltages within. When fully charged each cell is just over 4.1 volts, so 10 in series are just over 41 volts.

That's the start voltage when fully charged, cut off needing recharge occurs at 32 volts. The nominal 36 or 37 volts quoted is roughly a midway point.
.

 

[KEN OPENSHAW]

Hi David
So the batteries where probably 50% charged when left for over 12months, if they now show less than 41v after 24 hrs charge what’s the prognosis ?

 

[Nealh]

Hi David
So the batteries where probably 50% charged when left for over 12months, if they now show less than 41v after 24 hrs charge what’s the prognosis ?

If the battery is less then 41v, it means the battery is out of balance or voltage is waning which means end of life.
An unbalanced battery is recoverable and it may recover it self over a charge or three. When charging the balancing of the cells happens towards the very end of the charge so even if the charge light turns green leave all alone for another hour or even two to allow the balance procedure to continue often this corrects the in balance.
The voltage can be simply checked with a mutli meter on the battery connection.

A battery out of balance means a cell string (parallel cells) has a lower voltage then the others. 36 volt battery will have 10 parallel cell strings, each sting of cells will have 4,5 or 6 single cells welded in parallel to construct a string, there will be 10 such strings connected in series to achieve a 36v battery build. 41.5 or higher is a sign of good balance.

 

[KEN OPENSHAW]

Thanks David....So to sum up.( It is a 575 battery ) If this battery has gone past its hibernation stage, and after 2/3/4 charges and left alone (as your comments) and when checked with a voltmeter the voltage is less than 41v it has reached the end of its life and should be replaced.

 

[Nealh]

I'm not David or have any connection to Wisper bikes.
I just used your quote to David in my post, maybe I should have omitted it to prevent confusion.

 

[KEN OPENSHAW]

Hi Nealh Ah...right never bothered to check the...just thought I was talking to David ! ....So what do you think re my summary ?
Cheers
Ken

 

[Nealh]

Batteries can be daunting however if you know your way around one or if you are hands on practically they can often be remedied, though time and patience is needed.

Sometimes if they don't balance via charging you
have to open the battery up and manually balance the low string to match the other string voltages. After this the battery should remain balanced if it is used often/regularly and the cells are in good order.
Most shops or ebike sellers don't have this knowhow/knowledge to perform this work and would not guarantee success in the event they could , for
most it isn't a cost effective way to do business so often will not entertain the idea and just insist on selling a new battery.

 

[Nealh]

Hi Nealh Ah...right never bothered to check the...just thought I was talking to David ! ....So what do you think re my summary ?
Cheers
Ken

The seller should ideally have the battery checked out by a dealer to see check if it is ok, however if not willing to do so you need to take in account that if thinking of buying the bike.
Do you know if it has been charged fully and the voltage is under 41v ?

A new battery is circa £300+ though David will be able to tell you exactly how much.

 

[Nealh]

Ebike batteries are a little more complex and expensive then other power sources which is why a lot of dealers don't touch them or more to the point manufacturers don't allow them to.

Which is why we always say to people you have to make an allowance when buying used often knocking the price of a new battery form the asked sale price or just walk away.
You are allowed and maybe able to remedy a faulty battery with our help but a bike brand seller isn't able to.

 

[KEN OPENSHAW]

Thank Nealh.....so are you saying that lithium batteries can ALWAYS be recovered by this method of balancing ?
In reply to your latest post ....I informed the seller of my concerns re the battery and made him an offer on the basis of myself replacing the battery....he hasn’t replied !