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Help! Recommissioning Kilovault 1800 HLX batteries with a new MidNite Solar Classic 150

Hi all,

I've got two Kilovault 1800s in series (24V bank) with a new MidNite Solar Classic 150. I've had the batteries for years and they've been working great, using a Blue Sky 3024i charge controller.

Before recommissioning the batteries with the new Classic 150, I individually charged each battery up to 14.1 volts so they were of equal charge and put them back in series.

When they are connected to the MidNite Classic 150, one of the batteries (067)   is fine for about 20 or 30 seconds, then briefly drops down to anywhere from 5 to 8 volts. Then it jumps back up to full voltage. The Classic 150 then restarts and the cycle repeats after about 20 or 30 seconds. The other battery – (075) stays solid at full charge. The 067 battery that is dropping down is on the positive side of the battery bank. The 075 battery is on the negative side. I’ve repeatedly checked the wiring between the batteries and the classic and all is well with the wiring and fuses.
Note - This is happening without connecting the PV array or connecting the inverter.
I’m trying to determine if the problem is with the battery or if the Classic 150 is somehow causing the drop.
I’ve been on the phone with Midnite solar tech support and they are telling me it’s very likely something that the BMS is doing.
If the batteries are slightly imbalanced, would this be happening? Nothing is showing up in the log and the batteries are of equal charge.
Any ideas?
thank you!



Hello Mark,

When we answered your question a while ago through our HelpDesk, I forgot to answer here also.

The first thing to check will be the charging parameters programmed into your Classic. For example, if either Bulk or Absorb are too high, the battery could go into high voltage protection and briefly shut down, which shuts down your inverter.
Because of minor differences between batteries, it is very easy for one battery to hit high voltage protection before the other.

Bulk and Absorb should be 14.1V.
Absorb time (if programmable) should be 2 minutes or less.
Float should be ≈13.6V or lower. Low enough so it will not trigger float when the battery relaxes after charging stops.

Thank you again for being a KiloVault customer!