Viking 4 x 4 powerchair batteries

[Presland123]

Hi all.

I was called to help a customer who recently brought a used Viking 4 x 4 powerchair. It was working, but didnt seem to be charging and now its stopped working due to low voltage.

Looking online its 48v (they were given a standard 24v mobility battery charger which explains the lack of charging). On removing the batteries, it looks like as standard it has 4 x 12v batteries but on this one, it has a metal case with what looks like lithium batteries.

I have attached some pics but has anyone come across these batteries before. I am thinkiong of converting ot 4 x 12v batteries as shown in the manual, but wanted to see first if anyone has any experience of this powerchair.

Thanks

[Burgerman]

Looks to me like it has 8 lithium ion phosphate cells. So a nominal 24v. And a BMS. And so if the battery is below 2.5V on any single cell then its probably destroyed. You can sometimes rescue a cell that is low. If extremely lucky. But not often.

You should charge it at between 3.5V and 3.65V per cell and definitely no more! A standard lead charger at 28.80V intended for a wheelchair should charge that at 3.6V X 8 or 28.8V and so the problem has nothing to do with it being 48V. Because its not.

Probably it has been allowed to sit and has discharged too low. Or the BMS has allowed the cells to become unbalanced and 1 cell has gone too low. Or it WILL charge but will need about a very long time due to cell imbalance and a weedy 100mA cell balancing capability of the BMS it has. This is why we tend to use hobby chargers with much greater balancing capability.

If you think its discharged because its super slow then get used to it. They are slow as hell. They have to be in order to have enough torque to tank/skid steer 4 wheels.

A better photo would help!

Measure the exact voltage of each individual cell.
And post them here?

If all are between 2.5V or more or 3.6V or less then theres a good chance to fix it with a little patience. Ideally no cell should go lower than 3.0V in daily use.
If it checks out then you may need a hobby charger or an adjustable power supply to fix things.

Which is easy enough.

[woodygb]

@David .

As B.M. has said it is not 48v.
The Viking appears to have been made originally with 4 off 12V 27AH batteries , arranged to give a 24v battery of 54 Ah.

Here is a pic that might help you understand that "24v" battery pack.

[Burgerman]

Or just count the number of small balance wires.

[Presland123]

thanks, all I will do some more testing but really appreciate your help