Hello!

I built a loadshedding backup solution using a single Revov 200ah 12v 2nd life battery and a RCT 1KW 12v MPPT inverter. I configured the inverter to use a "custom" battery instead of AGM or lead acid, and set the bulk, float, and cut off voltage values as specified by Revov.

After charging (the inverter's charging light stays a solid green) the inverter shows the battery voltage to be 13.7v, but the BMS shows this as 13.6. When the mains power goes out, the inverter immediately shows the voltage drop from 13.7 to 13.5 (load is only about 200w).

Looking at the BMS app, it shows that the four cells aren't balanced.

Stats:

• TotalVolt: 13.60v.
• Balance: ON (apparently it's try to balance the cells but this never completes, even if left charging for days)
• Cell information:
  • Cell 1: 3.50v
  • Cell 2: 3.38v
  • Cell 3: 3.36v
  • Cell 4: 3.36v

My question is, do I try and make use of the cell balancing setting on the inverter by enabling it? If so, which values should I use? I think it needs to set a time to specify how long to run the balancing for.

One more question - do I increase the float charge to 13.8v seeing as it's sitting at 13.6v on the battery and drops immediately from 13.7v (as per the inverter's reading) to 13.5 when AC power goes?

Thanks so much!

 

On 2023/03/14 at 9:49 AM, min.emerg said:

My question is, do I try and make use of the cell balancing setting on the inverter by enabling it? If so, which values should I use? I think it needs to set a time to specify how long to run the balancing for.

Hi, yes this will be the best way to get the battery to charge fully. I would suggest setting the timed absorb to 14.1V for 30min and see how well that charges and increase the time if necessary to get to 100%. Keep an eye on the cell voltages and see that it is balancing nicely. Once you have the time worked out you can set it to repeat daily.

On 2023/03/14 at 9:49 AM, min.emerg said:

One more question - do I increase the float charge to 13.8v seeing as it's sitting at 13.6v on the battery and drops immediately from 13.7v (as per the inverter's reading) to 13.5 when AC power goes?

Your float setting should be fine at 13.7V even if the battery is at 13.6V, it is still above the settling voltage of 13.5V. The timed absorb stage should take care of charging to 100% and then it should just sit around at float voltage after that.

Great, thank you! I'll report back with my findings! 

Still struggling to get the cells to balance. I've tried a few different combinations of settings on the inverter but no luck. Will keep trying!

I have a friend who fixed this issue on the same battery . You have to disable charge balancing on the BMS app and check that the balancing is set to start at 3,4V and not lower.

I suggest you verify the voltages with a good multimeter. 
Is the builtin charger in your inverter really good enough for what you want from it.

I recently invested in a very expensive (for me) Victron ip22 30a 12v charger to do maintenance on all my batteries - it was an eye opener for me.

Its got a bluetooth app where you can see what it does.

Edited March 30, 20231 yr by Johandup

I have a simmilar problem. I have a Kodak 3kw inverter, a 24v system connected to two Revov 200ah batteries. The system was installed in my previous home. It was in storage for about 4 months, now installed in my new home. The BMS app shows that both my batteries only charges ip to 80% full. The inverter shows batteries are 100%. I rather believe the bms app that says 80%. Where must i start looking to fix my problem?

Sorry for highjacking your post.

18 hours ago, Kortsluiting said:

I have a simmilar problem. I have a Kodak 3kw inverter, a 24v system connected to two Revov 200ah batteries. The system was installed in my previous home. It was in storage for about 4 months, now installed in my new home. The BMS app shows that both my batteries only charges ip to 80% full. The inverter shows batteries are 100%. I rather believe the bms app that says 80%. Where must i start looking to fix my problem?

Sorry for highjacking your post.

You need to check your charge voltages and how long it stays there for the cells to balance and reach 100%. A 16S (51.2V) battery needs to charge to 56V and float at 54V.

Also make sure the inverter is actually reaching the bulk voltage and not stopping at float voltage as these inverters suffer from the premature float bug. If it doesn't reach bulk you will need to use the timed absorb or equalization settings to get the battery up there long enough.

Edit: apologies, it's early and before coffee... realised this is a 24V system so you should be able to just halve the voltages above.

Edited April 2, 20231 yr by jumper