Double Battery Mod Failed, need help

[k107044]

Hello all
I followed this video to add a extra 36v battery for my 36v Himo Z16.
https://www.youtube.com/watch?v=0CrQ1FhGGhs&t=2s
I connected the new battery and the original battery together like the picture shown.

When I charge through the original battery, the voltage of two battery don't share. 
The voltage of the original battery keep increasing up to 37.9V while the new battery stay in 36.4V.
What is wrong? I thought both voltage would increase together. 

I used a voltmeter to check the xt60 connector of both side in picture and there are voltage in both connector.
Also, I try connecting both battery alone to the controler and it work for both of them.
So, I believe that the connection is fine.

Furthermore, I once shorted the charge port of the new battery, it create a spark and the charge port was damaged.
Hence, the only way for me the to charge the new battery is through the discharge port.
I dont know if it has any thing to do with the problem.
​​​​​​​

 

[calab]

The bms is whats wrong or could be you use anti-spark connector connecting both batteries in parallel?
There are so many different bms' out there, who really knows what you have because you did not state, so can assume low quality batteries from unknown shadowing sources?
The only thing you stated was you have a new battery and an old battery, so different bms'
You will have to charge each individually and when you reconnect make sure voltages are within 0.10v ideal or 0.05v is best.
Yes unplug batteries when charging.
You might have damaged something but do as I say and see what happens.

 

[E-HP]

Hello all
I followed this video to add a extra 36v battery for my 36v Himo Z16.
https://www.youtube.com/watch?v=0CrQ1FhGGhs&t=2s
I connected the new battery and the original battery together like the picture shown.
ebike.jpg
When I charge through the original battery, the voltage of two battery don't share. 
The voltage of the original battery keep increasing up to 37.9V while the new battery stay in 36.4V.
What is wrong? I thought both voltage would increase together. 

I used a voltmeter to check the xt60 connector of both side in picture and there are voltage in both connector.
Also, I try connecting both battery alone to the controler and it work for both of them.
So, I believe that the connection is fine.

Furthermore, I once shorted the charge port of the new battery, it create a spark and the charge port was damaged.
Hence, the only way for me the to charge the new battery is through the discharge port.
I dont know if it has any thing to do with the problem.
​​​​​​​

If your main battery has an on/off switch, then it should be set to on while charging, otherwise nothing is going to the second pack. Be careful not to turn it on if the voltage are not synched up though.

 

[k107044]

The bms is whats wrong or could be you use anti-spark connector connecting both batteries in parallel?
There are so many different bms' out there, who really knows what you have because you did not state, so can assume low quality batteries from unknown shadowing sources?
The only thing you stated was you have a new battery and an old battery, so different bms'
You will have to charge each individually and when you reconnect make sure voltages are within 0.10v ideal or 0.05v is best.
Yes unplug batteries when charging.
You might have damaged something but do as I say and see what happens.

Thank you for your help

I dont think my set up has an anti spark connector so it is likely to be a bms problem.
Yes, there are different bms'

I cannot charge the new battery individually as the charge port has been damaged and I already cut it.
Also, I think my battery only has one port to use as both charge port and discharge port. See the photo below

the two wires spilt from the xt60 connect are where the charge port connected originally.
So, if I cannot charge through the xt60 connect, I will not be able charge through the charge port, right?

Are replacing the BMS my only option now?

 

[E-HP]

So from your diagram above, you're saying the voltage on one XT60 connector is different from the other XT60? Both when connected and disconnected?

 

[k107044]

So from your diagram above, you're saying the voltage on one XT60 connector is different from the other XT60? Both when connected and disconnected?

Firstly, I charge both battery to 36.4V, then connected them together like the diagram.
Secondly, I charge through the orignial battery while they are connected.
Lastly, I disconnected them and check their voltage through the two XT60 connector, the orignial battery is at 37.9V and the new battery stay at 36.4V.

Deleted: I have no way to check their voltage when they are connected but I believe that the voltage are different even when two battery are connected.

 

[E-HP]

So from your diagram above, you're saying the voltage on one XT60 connector is different from the other XT60? Both when connected and disconnected?

Firstly, I charge both battery to 36.4V, then connected them together like the diagram.
Secondly, I charge through the orignial battery while they are connected.
Lastly, I disconnected them and check their voltage through the two XT60 connector, the orignial battery is at 37.9V and the new battery stay at 36.4V.

I have no way to check their voltage when they are connected.

Will they discharge together?

 

[k107044]

So from your diagram above, you're saying the voltage on one XT60 connector is different from the other XT60? Both when connected and disconnected?

Firstly, I charge both battery to 36.4V, then connected them together like the diagram.
Secondly, I charge through the orignial battery while they are connected.
Lastly, I disconnected them and check their voltage through the two XT60 connector, the orignial battery is at 37.9V and the new battery stay at 36.4V.

I have no way to check their voltage when they are connected.

Will they discharge together?

I am not sure, I haven't try it.
But they can discharge alone, I can connected the new battery alone to the bike and it can power the bike.

 

[neowizard]

Couple things.

1. since you have those cut wires coming out of the XT60, you can definitely test the voltage in the connection during charge - just probe those loose wires.

2. The BMS on the OLD battery might be screwing you. It's not unreasonable for it to refuse to discharge while charging. Not all BMS are like that, but some are.

I'd try to draw 1A from your old pack while it's charging, if you can't, that clearly indicates you can't charge the new battery from the output of the old one. The correct way to do this would be a load tester, but if you need to hack a solution you can also use any resistive load. If you have a cheap 120V 1000w electric kettle (a 500W would be better, but they're uncommon), that would likely use a resistive heat element and would draw 1-3A from your pack (try this at your own risk).

 

[k107044]

So from your diagram above, you're saying the voltage on one XT60 connector is different from the other XT60? Both when connected and disconnected?

Updated: When I connected both battery, the voltage will share
For example, when I connect the origial battery at 37V to the new battery at 36.4V, the voltage of the new battery will go up to 37V.
However, when I disconnected them, the new battery go back to 36.4V.

 

[k107044]

Couple things.

1. since you have those cut wires coming out of the XT60, you can definitely test the voltage in the connection during charge - just probe those loose wires.

2. The BMS on the OLD battery might be screwing you. It's not unreasonable for it to refuse to discharge while charging. Not all BMS are like that, but some are.

I'd try to draw 1A from your old pack while it's charging, if you can't, that clearly indicates you can't charge the new battery from the output of the old one. The correct way to do this would be a load tester, but if you need to hack a solution you can also use any resistive load. If you have a cheap 120V 1000w electric kettle (a 500W would be better, but they're uncommon), that would likely use a resistive heat element and would draw 1-3A from your pack (try this at your own risk).

I don't think it is the BMS on the OLD battery that cause the problem since even when it is not charing, the voltage of two battery still do not share. See my example above.

 

[E-HP]

So from your diagram above, you're saying the voltage on one XT60 connector is different from the other XT60? Both when connected and disconnected?

Updated: When I connected both battery, the voltage will share
For example, when I connect the origial battery at 37V to the new battery at 36.4V, the voltage of the new battery will go up to 37V.
However, when I disconnected them, the new battery go back to 36.4V.

If it's a lithium ion pack, then a 36V (10S) pack should fully charge to 42V. If the old pack can make it over 36.4V, then it could be a bad series group or two, which is why it could show the higher voltage immediately after disconnecting the packs, but drifts quickly lower.

 

[neowizard]

So from your diagram above, you're saying the voltage on one XT60 connector is different from the other XT60? Both when connected and disconnected?

Updated: When I connected both battery, the voltage will share
For example, when I connect the origial battery at 37V to the new battery at 36.4V, the voltage of the new battery will go up to 37V.
However, when I disconnected them, the new battery go back to 36.4V.

First off, are you absolutely sure both batteries are the same chemistry and cell-count?

When you charge only the old battery, what voltage does it charge to? Does it stay over 3.7*cell_count after 24h? If it charges to less than 4.2V*cell_count or can't stay over 3.7V*cell_count (better yet, test each cell to see that they're each above 3.7V AND ballanced) then the old battery might be frocked.

If the old battery is fine - do the same with the new one. Make sure that's healthy as well. I'd love to know what you find

 

[k107044]

So from your diagram above, you're saying the voltage on one XT60 connector is different from the other XT60? Both when connected and disconnected?

Updated: When I connected both battery, the voltage will share
For example, when I connect the origial battery at 37V to the new battery at 36.4V, the voltage of the new battery will go up to 37V.
However, when I disconnected them, the new battery go back to 36.4V.

If it's a lithium ion pack, then a 36V (10S) pack should fully charge to 42V. If the old pack can make it over 36.4V, then it could be a bad series group or two, which is why it could show the higher voltage immediately after disconnecting the packs, but drifts quickly lower.

How can I check if there are bad series or not?

 

[E-HP]

How can I check if there are bad series or not?

Unfortunately you will at least have to remove some of the shrink wrap in order to access the BMS and the connector for the balance wires. If you have access to the wires, you can test each of the 10 series groups to see how many are significantly lower/higher than the others, which should indicate if there's a problem.

 

[k107044]

How can I check if there are bad series or not?

Unfortunately you will at least have to remove some of the shrink wrap in order to access the BMS and the connector for the balance wires. If you have access to the wires, you can test each of the 10 series groups to see how many are significantly lower/higher than the others, which should indicate if there's a problem.

I have remove the shrink wrap and check the balance wire on the BMS. It seem to be fine, every connector have a voltage different of 3.7V.

 

[k107044]

Right now the problem is that I cannot charge the new battery.
The new batery only have a single port : the xt60
I try to connect it with a charger be it dont charge.
However, I can still read the voltage of the battery from the xt60 connector.

I have ordered a new BMS, let see if it fix the problem

 

[E-HP]

How can I check if there are bad series or not?

Unfortunately you will at least have to remove some of the shrink wrap in order to access the BMS and the connector for the balance wires. If you have access to the wires, you can test each of the 10 series groups to see how many are significantly lower/higher than the others, which should indicate if there's a problem.

I have remove the shrink wrap and check the balance wire on the BMS. It seem to be fine, every connector have a voltage different of 3.7V.

20220210_151750.jpg

3.7 x 10 would be 37V but you said you're getting less at the discharge connector, so what is the voltage reading between the first anf last pin of the balancing wires?