Multiplus 3k charging at 16v?

[JDoench]

Issue: fluctuating charging voltage from multiplus 3k 12v - swings from low around 13.5 up to over 16 volts as reported on the Victron Connect app. This is a new system (latest firmware on all components), I have the programming dongle and have set the charging parameters as per instructions from LiTime (400ah batt). We can see the 16v flash by in the Victron Connect app on the programming PC and from the shunt readout on my phone, but it does not show in the Trends report or the History report on the Smart Shunt so far as I can see.

Has anyone seen this before? I had assumed the charging voltage would be relatively steady.

System:
Litime 400ah battery fully charged with Litime charger before use
Multiplus 3k 12v with bluetooth dongle

also
SmartSolar MPPT 100/50, not yet hooked up to any solar
Lynx Distributor

 

[sunshine_eggo]

Mind bogglingly common. So common.

LiTime battery cells are imbalanced and engaging protection blocking incoming charge current. Charger can't cut current quickly enough to prevent a spike.

The solution is to hold at 13.8V for at least 24 hours so the BMS can balance the cells and try again.

 

[JDoench]

Mind bogglingly common. So common.

LiTime battery cells are imbalanced and engaging protection blocking incoming charge current. Charger can't cut current quickly enough to prevent a spike.

The solution is to hold at 13.8V for at least 24 hours so the BMS can balance the cells and try again.

Thank you for the advice. I initially charged it to 100%, but took it off the charger once the light turned green. It was 13.8 at that time. I'll hook it back up and see how it does tomorrow night.

 

[JDoench]

Testing again this morning. Battery voltage reads 13.6 as it did all day yesterday. We turned on the multiplus, then plugged in to shore power.

At first, all seemed good. The battery should be at 100%, so we didn't expect much of anything to be coming in from the MP. It sat steady for a few seconds then began to climb. Once it got above 14.11v, it shot up over 15v, so we unplugged and shut it down again.

I have sent an email to LiTime for support.

 

[Supervstech]

Testing again this morning. Battery voltage reads 13.6 as it did all day yesterday. We turned on the multiplus, then plugged in to shore power.

At first, all seemed good. The battery should be at 100%, so we didn't expect much of anything to be coming in from the MP. It sat steady for a few seconds then began to climb. Once it got above 14.11v, it shot up over 15v, so we unplugged and shut it down again.

I have sent an email to LiTime for support.

14.11 is average 3.5275V per cell.
If ANY cells are out of balance, some will hit 3.65, max cell voltage, and the bms will go into high voltage safety disconnect.

Don't charge that high.
13.7 is 3.42V per cell, and is a far better charge voltage limit.

Lower your charger settings. Prevent the bms interaction.

 

[JDoench]

14.11 is average 3.5275V per cell.
If ANY cells are out of balance, some will hit 3.65, max cell voltage, and the bms will go into high voltage safety disconnect.

Don't charge that high.
13.7 is 3.42V per cell, and is a far better charge voltage limit.

Lower your charger settings. Prevent the bms interaction.

Thank you. I have changed my MP charger settings to:
Charge current: 90a
Absorption V: 13.7V
Float V: 13.55V
Rep.Abs.Int.: 7d
Rep.Abs.Time: 1h
Abs.Time: 2h

I just wanted to confirm that this is what you meant, as opposed to trying to change the settings on my standalone charger.

I appreciate your help.

 

[Supervstech]

Yup, 13.7V will be an average of 3.45/cell, and allow the balancing circuit to bring all cells up to 100% without triggering the overvoltage alarm.
After all cells are equally reaching 3.45V, the voltage can be raised to 13.8 or 13.9...

But I would set the float to the same voltage.
Unless you don't use the system regularly.

 

[Dooug]

Mind bogglingly common. So common.

LiTime battery cells are imbalanced and engaging protection blocking incoming charge current. Charger can't cut current quickly enough to prevent a spike.

The solution is to hold at 13.8V for at least 24 hours so the BMS can balance the cells and try again.

Is this an initial charge issue or a long term challenge with the balancing circuit?

 

[sunshine_eggo]

Is this an initial charge issue or a long term challenge with the balancing circuit?

Typically just initial. Even if a builder does a perfect top balance, it can be lost to the point that it can generate a cell runner in a matter of just a week or two. Generally speaking the balance is good enough such that it doesn't impact total capacity by much, but it may prevent charge to 14.4-14.6V due to a cell runner that triggers protection.

The BMS will eventually top balance the cells with regular charges to full and regular cycling.