Unusual 36V Battery - any ideas

[gilbern]

Please can someone identify the battery cells. They are in 2 blocks of 5. One block gives 20v the other block gives 19.7. They are wired in series with connectors going to a 10S port. BMS ?.
What is the maximum charge these cells can take and where in the UK can you buy them.

The bike I have is a Powacycle Salisbury in VGC with a 180W rear motor. It probably should be powered by a 24V battery.

My problem is that after riding the bike for about 10minutes the power dies even though the battery shows plenty of charge.

Would it be the BMS on the bike that doesn't like the 36V or a problem with the BMS on the battery.

If I remove (temporary) the battery BMS should it still power the bike.

Sorry for all the questions - I am new to electric bikes and wanted to try one before buying a more decent one.

 

[Nealh]

They are either 10s Li-pol cells in which case voltage should be 41.5 - 42v in which case they have had it with your voltage readings.

OR

LifePo4 cells would seem more in keeping as they have a lower cell voltage and 24/26v is actually 10s in stead of 7s as with lion or lipo.
The cell voltage readings for this doesn't look right.

LifePo4 though only has a small voltage range typically 3.2v - 3.65v.

How much does each pack weigh ?

 

[wheeliepete]

Voltage on the 2 packs should be 21v fully charged, 5 x 4.2v, so the 10 together gives 42v, normal voltage for a 36v battery pack. They are pretty old cells, so could be suffering voltage sag when put under load when riding the bike, but showing OK voltage when tested. Does the bike have a battery level indicator on it? If it does, do all the lights go out when bike cuts out? The BMS looks right for a 36v battery (11 wires), but will cut power if the voltage drops below about 32v, which is what may be happening.

 

[gilbern]

They are either 10s Li-pol cells in which case voltage should be 41.5 - 42v in which case they have had it with your voltage readings.

OR

LifePo4 cells would seem more in keeping as they have a lower cell voltage and 24/26v is actually 10s in stead of 7s as with lion or lipo.
The cell voltage readings for this doesn't look right.

LifePo4 though only has a small voltage range typically 3.2v - 3.65v.

How much does each pack weigh ?

Thanks for the reply.

I'll weigh the batteries and also try to get more info.

 

[gilbern]

Voltage on the 2 packs should be 21v fully charged, 5 x 4.2v, so the 10 together gives 42v, normal voltage for a 36v battery pack. They are pretty old cells, so could be suffering voltage sag when put under load when riding the bike, but showing OK voltage when tested. Does the bike have a battery level indicator on it? If it does, do all the lights go out when bike cuts out? The BMS looks right for a 36v battery (11 wires), but will cut power if the voltage drops below about 32v, which is what may be happening.

Thanks for the reply.
The bike doesn't have a battery level indicator

I have checked the voltage on a multi-meter and also using a IMAX B6 on each bank of 5 cells.

I am going to rig the bike up to let it run down the battery to the point wher it cuts out and see whether there is any power left at that point.

Can you suggest any other test ?.

 

[gilbern]

Thanks for the reply.

I'll weigh the batteries and also try to get more info.

The batteries weigh 2kg each so 4kg for the 40V.

The batteries are out of an aluminum case that has a very faint label saying DC37.0V.

Hope the above helps.

 

[wheeliepete]

Can you suggest any other test ?.

If you can connect your multimeter while you run the bike you will be able to monitor the voltage drop.

 

[flecc]

The 180 watt Salisbury originally used a 24 volt 20 cell NiMh battery, later a 7 cell 26 volt Li-polymer.
.

 

[gilbern]

If you can connect your multimeter while you run the bike you will be able to monitor the voltage drop.

I'll need to reassemble the battery and then i'll try the multimeter.

 

[gilbern]

The 180 watt Salisbury originally used a 24 volt 20 cell NiMh battery, later a 7 cell 26 volt Li-polymer.
.

Thanks for the info.

 

[gilbern]

I'll need to reassemble the battery and then i'll try the multimeter.

Connected the MultiMeter and found the following.

At start 39.7V.

Five minutes riding and intermittently the motor will stall but battery still shows about 36V. Stop for a minute and bike will continue for another 5 minutes.
After 15minutes battery drops to 0.2V and bike will not continue.
After leaving bike for about 3hours battery then shows 37.9V (without charging) but immediately drops to 0.2V when tested again.

Any thoughts would be welcome.

 

[Nealh]

New battery needed ?
Though try without the BMS to rule out a BMS fault.

 

[gilbern]

New battery needed ?
Though try without the BMS to rule out a BMS fault.

Thanks Nealth

I have just read a post from 2013 (Thalmosy) and some of the suggestions there.
I have tested each cell and find that 4 of the 10 cells show zero charge,
I am currently seeing whether these individual 0 cells will take a charge using the BMAX charger. If they don't my next stage will be to use the good ? 6 cells to hopefully create a 24V battery. The bike is meant to have a 24V battery rather than the 36V battery.
Do you know if the 36V battery BMS which has a 10S lead will still work with only 6 leads active ?.
If this doesn't work then like you say it sounds like a new battery is in order.

 

[Nealh]

Any cell showing 0v is well and truly finished.
10s bms won't work for 6s as it will be expecting to see all 10s voltage readings, you will need a 6s bms or use it without a bms and manually keep an eye on charge/discharge voltage.
6S BMS with balancing < $14 delivered on Aliexpress.
Though true 24v is 7s.

 

[gilbern]

Any cell showing 0v is well and truly finished.
10s bms won't work for 6s as it will be expecting to see all 10s voltage readings, you will need a 6s bms or use it without a bms and manually keep an eye on charge/discharge voltage.
6S BMS with balancing < $14 delivered on Aliexpress.
Though true 24v is 7s.

Once again many thanks for your replies.

Much appreciated.