is this a normal charge pattern?

[Gabriël]

hi!

after switching to grid this morning i had the following charge rate, note sudden jump from just over 80% to 100%; is this normal?

[Guest]

IF I understand, yes, the BMV does that. Also a bit about that on the forum way back.

BMV's need to be given some TLC now and then. Like a Zeroing and a manual set to 100% SOC.

I do it every while when the system is fully charged. I switch of all, ensure that no current is passing through the BMV, and if so, and all is off, I Zero the current.

Biding my time, seeing the batteries are fully charged, controllers are in float, yet SOC is not, I set the SOC to 100% manually.

[___]

17 minutes ago, gabriel said:

note sudden jump from just over 80% to 100%; is this normal?

You're using a BMV right?

Yes this is normal. But it might not be good.

Quick explanation how the BMV works.

A typical lead acid battery, while at absorption, will show 1) a voltage higher than 2.25V per cell, 2) current that's dropping off as the battery accepts less charge. So when the battery is 100% full it will typically accept only a few amps at most.

So what the BMV does is look for a condition where the voltage is high and the current is low. This condition has to hold for a certain period of time. You can configure all three these items on the BMV: the charged voltage (setting 02), the tail current (setting 03), and the charged detection time (setting 04).

What sometimes happens, under just the right conditions, your loads and the available PV balance such that the remaining charge current is below the tail current, the batteries are full enough to rise above the charged voltage, and this happens for long enough that the BMV detects it as full. The battery may however not be completely full.

The trick to get around it is to set the tail current nice and low (about 1% of the Ah capacity, maybe 2% for some flooded cells), and the detection time should be set to something like 15 minutes.

You will also have to manually charge the batteries fully now to resync the BMV.

[Gabriël]

thanks guys, i'll read your comments another half a dozen times until it sinks in and then i'll act upon it.

we have the bread baker on at present. it results in a very spiky chart - would it not be better to put it on a dedicated utility outlet?