Pylontech self discharge

EVandPV

My 2 Pylontech batteries haven't been charged since the 25th when we last had some decent pv generation (haven't started grid charging yet) and since then, the SOC has dropped from the 15% I set as the max DOD to 11%.
4% seems quite a bit to drop in less than 3 days. Is this normal ?

Exiled_Tyke

I'm wondering whether the BMS is cleverer than we suspect. My battery is a Solax. I find that once in a while it discharges to 5% and then immediately recharges from the mains. I'm wondering whether it needs to do this for some greater purpose (calibration?) that we don't know about.

EVandPV

Exiled_Tyke wrote: »

I'm wondering whether the BMS is cleverer than we suspect. My battery is a Solax. I find that once in a while it discharges to 5% and then immediately recharges from the mains. I'm wondering whether it needs to do this for some greater purpose (calibration?) that we don't know about.

In my case, the lost power hasn't been restored.
I guess it's possible the inverter is drawing this power from the batteries even though it isn't doing much. Would be less noticeable with a larger battery.

mmmmikey

EVandPV wrote: »

In my case, the lost power hasn't been restored.
I guess it's possible the inverter is drawing this power from the batteries even though it isn't doing much. Would be less noticeable with a larger battery.

A quick bit of mental arithmetic.....

If you assume you are "losing" 1% of the battery capacity per day that is 48Wh per day for a 4.8kWh battery or a continual power draw of 2W which doesn't sound like an unreasonable amount for the inverter to be using when idle.

1961Nick

mmmmikey wrote: »

A quick bit of mental arithmetic.....

If you assume you are "losing" 1% of the battery capacity per day that is 48Wh per day for a 4.8kWh battery or a continual power draw of 2W which doesn't sound like an unreasonable amount for the inverter to be using when idle.

The standby losses for the Sofar ME3000SP inverter are <5w.

EVandPV

mmmmikey wrote: »

A quick bit of mental arithmetic.....

If you assume you are "losing" 1% of the battery capacity per day that is 48Wh per day for a 4.8kWh battery or a continual power draw of 2W which doesn't sound like an unreasonable amount for the inverter to be using when idle.

Yeah, the manual for the Lux 3600 says <10watts in standby. Guess I had assumed it would power itself from the grid when the batteries dropped to the minimum soc.
Won't be an issue once we move to Octopus Go in a couple of weeks and start grid charging.

Solarchaser

I would say yes its normal.
And we may be fairly close, I'm east of Glasgow on a sofar with 3 pylontech and my soc has dropped from 19% on 25th to 16% now.
Truthfully I've never noticed it before and only checked mine because of this post.

But as Mmmmikey says, 1w constant per battery sounds about right, as its always running its leds and the bms, so its gotta use some power.

Solarchaser

I say we may be fairly close primarily because I last seen decent pv on the 25th also

EVandPV

Solarchaser wrote: »

I say we may be fairly close primarily because I last seen decent pv on the 25th also

I'm in Fife so yes, not that far. 👍
Had a red led (not flashing) on the master battery this morning which I'm guessing is low voltage alarm. A quick boost from the grid got rid of it.
The 2 Pylons seem to be out of balance now. The master has no green capacity leds lit while the slave has 2.
Should I disconnect the ac/dc to allow them to balance ?

Solarchaser

I wouldn't necessarily read it that way, some of the time, only one of the batteries will have leds lit up, I see that pretty often, even at 100%.

If you are unsure, switch them off and back on again, and when you press the run light you will see the actual charge.
I'd be surprised if you actually have 20% to 0%, as I've never personally seen that

EVandPV

Charging just started from pv and both batts have 2 capacity leds lit so all good.