Jump Start, or restart 16S BMS

[TimC]

I have a 48v lifepo4 bank with two 75 aHr batteries wired parallel to a Growatt inverter (3000 ES). They each have a 60A Xiaoxiang BMS.

I mistakenly left my EV plugged in too long. I'm assuming the BMS shut down the system. The Growatt shut down and now the battery won't take a charge.

I disconnected solar and battery from the Growatt and then reconnected. I'm assuming since the battery bank now measures 38V I need to boost the BMS with a quick charge above 48V to wake it up. How can I do this without a 48V+ power supply? The Growatt, despite showing 235V will not start the BMS/battery.

My PS only goes to 30V

 

[fega72]

If you can remove the top of the battery, then you can measure and charge the cells on by one with your power supply.

 

[TimC]

Thanks fega72. I can access the battery, it is a DIY build from 75aHr cells (16 cells each). I'll look into that however I think I will try to disconnect the BMS from the battery and reconnect first. Charging all 32 cells that way could take weeks (again).

Edit... disconnecting the bms didn't do anything.

 

[fega72]

Measure the cells, find the weakest ones and charge only that few a bit to bring the pack voltage back above the BMS cut off voltage

 

[Samsonite801]

I have a 48v lifepo4 bank with two 75 aHr batteries wired parallel to a Growatt inverter (3000 ES). They each have a 60A Xiaoxiang BMS.

I mistakenly left my EV plugged in too long. I'm assuming the BMS shut down the system. The Growatt shut down and now the battery won't take a charge.

I disconnected solar and battery from the Growatt and then reconnected. I'm assuming since the battery bank now measures 38V I need to boost the BMS with a quick charge above 48V to wake it up. How can I do this without a 48V+ power supply? The Growatt, despite showing 235V will not start the BMS/battery.

My PS only goes to 30V

Don't forget to set your Growatt low-voltage inverter cutoff to a bit higher voltage than your BMS shutoff (BMS usually referred to as the 'last line of defense')... Then in future the Growatt will simply shut itself off before BMS ever does...

 

[TimC]

All cells on this battery are at 3.2xxV except one at 2.95 and one at 3.18. I can't find the docs on the bms. Batteryhookup no longer has that bms and they've dropped the item page from their website. Anybody care to guess what voltage will wake up a 16S xiaoxiang SP20S020A? Web search comes up empty.

I'll charge those two cells to 3.2xxV and then see if I get any reading through the BMS. I get no volts through the BMS before starting to charge the two low cells.

Thanks for the help...

Edit... after bringing the voltage on one low cell to 3.2xxV I get just 16v with meter on positive battery post and negative downstream of the BMS. Should I be getting close to the voltage I get when the meter is on the pos and neg battery posts?

 

[TimC]

Don't forget to set your Growatt low-voltage inverter cutoff to a bit higher voltage than your BMS shutoff (BMS usually referred to as the 'last line of defense')... Then in future the Growatt will simply shut itself off before BMS ever does...

Thanks. I just followed Will's video for settings for this inverter. I have a lot of reading to do as the owner's manual is written in Greek.

 

[TimC]

I've charged one 48V battery to 3.2xxV on each of 16 cells. I still only get 16V through the BMS. Is this normal? I'm getting nothing from the supplier as far as the low voltage cutoff level that I need to exceed to wake this BMS up. I'll hook it up to the Growatt and see if the battery will take a charge but I'm concerned I either have a faulty BMS or I need to start the balancing/charging task all over again to get this to work.

 

[TimC]

BMS is still not working so I am taking another approach. I've connected the Growatt to the battery pos and neg directly without the BMS. It's now charging. I'll keep an eye on it and when the Growatt says the battery is at 54V I will reconnect the BMS and see what happens.

I just can't believe both BMS quit working at the same time.

 

[fega72]

Can you connect to the BMS using the Xiaoxiang app? If you can, then you can check the settings. (and the charge / discharge buttons, make sure both in the on position)

 

[TimC]

Can you connect to the BMS using the Xiaoxiang app? If you can, then you can check the settings. (and the charge / discharge buttons, make sure both in the on position)

I did try that. Thanks.

I boosted the low voltage cells in each battery but the result didn't wake up the BMS in either. So I bypassed the BMS and charged directly with the Growatt to 54v on each battery. Interestingly, one BMS woke up, the other did not. So I then wired everything up 2P. At first with the Growatt isolated from the batteries the sleepy BMS measured 15.xxV and the "woke" BMS measured 54.xxV. Once I closed the breaker both measured 54.xxV through the BMS. That seems to be the fix. I don't know for sure that the second BMS is functioning yet. I am charging using the Growatt for the rest of today's sunshine. Then I'll try to figure out if both BMS are working.

As far as the Bluetooth app... I am useless at getting it to power up. Not only because it doesn't recognize my password but the help screens are Chinese charactors. When I choose "forgot password" (I didn't forget) it sends a text with all Chinese characters. I'd be really ticked about that if I'd spent more than $7.50 on the module. Frankly I don't care. As long as the BMSs both work I'm fine. I'm not a data geek so I'd rarely look at it anyway.

So I am going to charge the bank up. Then before putting a load on I have to determine how to set the Growatt so this won't happen again. When I went into the settings the low voltage cut off was 42v. For some reason the batteries were drained to what the Growatt says was 38v but it had an error (19) that said there was no battery detected. They actually measured at 48.xxV. so I'm lost as to why this happened. Obviously both BMS shut down. Why I don't understand.

I'll be more carefull settimg the EV for short charges that I know will not drain the battery. That's easy to figure out during the day when the sun is shining as the car is charged and the battery gets a few amps as well. When the sun sets is when I'll have problems charging the EV.