Due to an Inverter / user problem I have two fully discharged AM2 5.5kWh Hubble batteries and one fully charged battery. Can I couple the flat batteries to the fully charged battery? If not how do i charge them as the Inverter is not hybrid and cannot start up with flat batteries?

Louwrens you need to be very careful how to approach this situation!!! You have 11kw of discharged lipo cells do not connect them to the fully charged battery as the discharged batteries could go into thermal runaway!!! You need a adjustable 60v power supply with current limiting feature. You need to wake up 1 at a time with current setting of 2.5 amps@ 50v. If you do not have the correct equipment rather contact Hubble technical support or your installer. Below link of power supply i use for battery build.

https://www.electromannsa.com/products/wanptek-adjustable-dc-power-supply-30v-10a-usb-digital-lab-bench-power-source-stabilized-power-supply-voltage-regulator-switch-1?variant=42493637165297&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&keyword=&utm_term=&utm_campaign=&utm_source=adwords&utm_medium=ppc&hsa_acc=3590323982&hsa_cam=16563535604&hsa_grp=&hsa_ad=&hsa_src=x&hsa_tgt=&hsa_kw=&hsa_mt=&hsa_net=adwords&hsa_ver=3&gclid=Cj0KCQiAic6eBhCoARIsANlox87m8rkbOde0jprLn-wQel6b-SJzlF205qkoOu3A-Uk1zDIDpjoC6QUaAiq6EALw_wcB

 

Thank you TaliaB, you confirm the concern I had. 

8 hours ago, Louwrens said:

Due to an Inverter / user problem I have two fully discharged AM2 5.5kWh Hubble batteries and one fully charged battery. Can I couple the flat batteries to the fully charged battery? If not how do i charge them as the Inverter is not hybrid and cannot start up with flat batteries?

I would 1st contact Hubble for guidance as the BMS will store this event. You don't want to go your own way and forgive the warranty. 

If no warranty I would take 2 pieces of 4sq mm wire 20m in length. Connect the neg from full battery to neg of discharged one. Cut the pos wire to create 2x10m long. Connect each piece at the pos of the full battery and discharged battery. Then after stripping about 20mm at the midpoint connect them in a brisk move for 15sec. and a quick disconnect for 15sec. Feel if the wires got hot. Then repeat if there is an increase in temp of wires. If they still feel below 60 deg C I will leave them connected but still monitor if the wires increase in temp. To play it save you can also have a midpoint break in the neg and connect a low voltage 50A between the ends. 

If one has a DC clamp meter one can also measure the current flowing between the 2.

Once the discharged has indeed taken charge you can connect it to the inverter for further full charge. 

Their might be a possibility that the BMS might not switch on and this method might not work. The previous post with a 60V Power supply might also be prevented from charging if this is the case 

The above values are just my estimated. The wire between then can also be 2.5mm and only serves as resistance to greatly reduce the current between the 2.

Edited January 28, 20233 yr by Scorp007

8 hours ago, Louwrens said:

Due to an Inverter / user problem I have two fully discharged AM2 5.5kWh Hubble batteries and one fully charged battery. Can I couple the flat batteries to the fully charged battery? If not how do i charge them as the Inverter is not hybrid and cannot start up with flat batteries?

You will need to wake up the BMS, a standard 9V battery or an alarm battery should supply sufficient power to do this. As soon as the battery wakes up it will start accepting current. 

You did not mention what inverter you have and if you have PV. Best would be to connect only one battery at a time to the inverter. Set the inverter to charge the batteries using PV only (assuming you have PV). Wake up the BMS using the 9v battery (connect in parallel to the flat battery). It takes a few seconds for the BMS to start up. It should start charging soon afterwards. You also want to set the inverter to use AGM setting without comms between battery and inverter

Some inverters won't start up without a (live) battery connected, so this might be an issue. 

I have done the above without issue a number of times, although never on NMC chemistry. It should however not cause a difference.

This is a 48v battery and the LVD is normally around 42v to my understanding the bms will only connect above 42v or am i missing something here. We need to give the correct advise to resolve this issue the safest way possible. I still feel to contact Hubble technical first would be the first step in the right direction 

https://www.sciencedirect.com/science/article/abs/pii/S2352152X20315516

If you have a SunSynk, there is an "Activate" option specifically to activate the BMS of a run down battery.

The Charge/Discharge are for my 4 x AM2 system, reduce as appropriate.

Edited January 28, 20233 yr by system32

On 2023/01/28 at 9:35 AM, TaliaB said:

This is a 48v battery and the LVD is normally around 42v to my understanding the bms will only connect above 42v or am i missing something here. We need to give the correct advise to resolve this issue the safest way possible. I still feel to contact Hubble technical first would be the first step in the right direction 

There are two LVD thresholds, one for the pack (the 42v by example mentioned in your post) and one for individual cells. Without seeing the BMS data you won't be able to quess which one was triggered. 

Cell voltages tend to differ a lot at both high voltages and low voltages, so it is more likely that the BMS disconnected the cells to protect them because the voltage of a single cell reached is protection voltage as opposed to the pack.

The BMS does not need to see 42v to start, it needs to see any voltage, but once it has gone into a state where it protected the cells that voltage needs to come from somewhere else (not from the internal cells but from an external source).  As mentioned in my earlier post 9v is enough to start up the BMS and turn on the battery. A decent inverter will then be able to charge the battery once it is turned on.

Hello everyone, thank you for your interest in this topic. I decided not to charge the batteries and the owner took them to Hubble in JHB. They found one dead cell in each battery and shipped them to CT for repairs. 

I believe it is critical to revive LiFe's correctly with controlled current levels and correct voltage levels and NOT to couple a flat battery to a fully charged battery.

On 2023/01/31 at 5:09 PM, Louwrens said:

Hello everyone, thank you for your interest in this topic. I decided not to charge the batteries and the owner took them to Hubble in JHB. They found one dead cell in each battery and shipped them to CT for repairs. 

I believe it is critical to revive LiFe's correctly with controlled current levels and correct voltage levels and NOT to couple a flat battery to a fully charged battery.

Was the dead cells the cause of the battery going flat or the result due to the battery being discharged to deep?

Do not know reason for dead cells - await the repair report