Stuck in Absorption and not Charging!

Q&A and troubleshooting
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1

Dear Community,

I have a 100Ah 48V Pack connected to a Victron 150V MPPT with two 600W solar panels. I also have a Victron MultiPlus II 5KVA 48V inverter.

I have the Absorption set at 58V (yes, high but you’ll see why now) and 1h absorption time. For some reason, the battery reaches absorption very fast and it stops charging, the battery clearly is not charged while there is sunlight. If I disconnect the charger the voltage does not exceed 51.1V and the battery never reaches it full voltage. The same behaviour occurs with the MultiPlus Charger.

I have a small breaker from AliExpress in series with the solar charger and I have a Shunt in series with the battery input. I have tested a direct cable avoiding both but the same behaviour occurrs.

Any ideas?

I have another 48V 100Ah pack to test which I intend to parallel at some point.

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2

You need to decrease the voltage back to ~54V, and increase the absorption time to 6hrs.
From the 2nd graph, the battery starts charging, but after ~1hr it stops - looks like the battery BMS disconnects due to over voltage at about that time, and the battery stops charging. This is probably as the battery is out of balance and one cell is high. Your float voltage should also be set to ~53.8V and allow the battery to balance itself. Cranking the charge voltage up with lithium’s is a bad idea.

1 Like
3

Agree with MikD.

4

Yep, me too. My understanding is you must have an occasional long absorption to balance the cells.

5

Thanks for the feedback. Looking at the resistance on the DC meter I have at the input it does seem clear to me that the BMS is disconnecting the battery as the resistance increases to open circuit.

I reduced the voltages to 54V and after a day it seems like a similar behaviour is occurring. I will leave the system as is for the next couple of days and report back! Here is the DC meter comparison at the battery input, it looks like the BMS Is still acting up.

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6

I would like to know more about the battery bank. Single battery, parallel, series, brand, “smart”, etc.

7

I seem to have found the issue, darn Aliexpress packs…

https://es.aliexpress.com/item/1005008665198128.html?spm=a2g0o.order_list.order_list_main.137.775e194dCH3NIN&gatewayAdapt=glo2esp

Quick read through the reviews would have should its a 15S pack marketed as a 16S and other people are experiencing the 52V cutoff…

Thanks for the help! Now I have mismatched 15S and 16S cells… DIY Relay or buying new pack.

Best regards,