Low Battery Warning: ESS wont' discharge below 51-52v

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slartybart asked May 14, '24

Low Battery Warning: ESS wont' discharge below 51-52v

My ESS system isn't working properly. Firstly the SOC readings are all over the place, at the moment the voltage (from the BMS says 51.8v and it displays as 99%). When it charges the SOC leaps from wherever it is immediately to 100% and then doesn't display properly. It will never discharge below 70-75% despite the limit being set for 20. The problem then is as soon as the LOW BATTERY alarm goes if forces a charge, usually when the electricity prices are high, which negates the point of having the system entirely. I'm not at home so I can't interrogate the BMS (Pace, I think, on a Fogstar 15.4kWh battery) but from what I can see it's the Multiplus forcing the charge not the BMS as the BMS isn't showing any alarms. Thanks.

PS. It's a Multiplus 8000 on v5.10. We have a small amount of solar which produces around 5kWh a day, the battery has a BMS with a 'Victron' setting, and the Multiplus is wired in 'single leg' to the grid. Cerbos S is up-to-date. We are on a dynamic tariff (Octopus Agile Roll on DESS support!) and so far I've ben manually setting charge periods. Mode: Optimised WITHOUT battery life.

ESS

screenshot-2024-05-14-at-092533.jpg (43.6 KiB)

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Modifications Space

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Answer 1 · 2024-05-14T08:10:19Z

Matthias Lange - DE answered · May 14 at 08:10 AM

Sounds more like a battery/BMS problem and/or a few settings are wrong not a problem with the Victron system.

If there is a low battery alarm the system forces a charging to the configured sustain voltage to protect the battery.

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Answer 2 · 2024-05-14T08:31:44Z

slartybart answered · May 14 at 08:31 AM

Thanks Mattias yes, unfortunately being away from home I'm unable to connect to the BMS to see what it's doing or how it's set. The behaviour certainly is as you describe. Now, for example it's using the grid (at high prices) when it should be using the battery, the battery is slowly being charged by solar, but ESS charge schedule is 'inactive'. The thing is, the low battery alarm is coming from the Multiplus not the BMS as far as I can see..... there are certainly no alarms shown in the BMS section of the 'Devices' menu, only the Multiplus. What I can do remotely (with a little help from a friend) is change the battery BMS protocol setting from 'Victron' to Pylontech. I might see if that syncs a bit better.

screenshot-2024-05-14-at-102313.jpg (190.9 KiB)

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Answer 3 · 2024-05-14T08:45:55Z

slartybart answered · May 14 at 08:45 AM

These are the Cerbo settings:

screenshot-2024-05-14-at-103459.jpg (93.4 KiB)

screenshot-2024-05-14-at-103534.jpg (92.9 KiB)

screenshot-2024-05-14-at-103638.jpg (108.7 KiB)

screenshot-2024-05-14-at-103832.jpg (98.9 KiB)

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Answer 4 · 2024-05-14T08:54:02Z

slartybart answered · May 14 at 08:54 AM

And these are the Ve.Config settings:

screenshot-2024-05-14-at-105209.jpg (192.8 KiB)

screenshot-2024-05-14-at-105116.jpg (201.1 KiB)

screenshot-2024-05-14-at-104926.jpg (167.9 KiB)

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Answer 5 · 2024-05-14T09:38:07Z

jeanmarie answered · May 14 at 09:38 AM

Hi Slartybart

as said by Matthias, first of all there is a problem with displayed SOC as with LFP cells at 3.27V you are more likely around 40% but certainly far from 100%.

BMS has been calibrated? parameterized?

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slartybart commented · May 14 at 10:09 AM

I thought as much.... unfortunately as I'm away from home I can't access the BMS... it probably needs its software updating and if the supplier had sent the lead I needed it's one of the first things I'd have done. For now however, telling ESS to charge to 100% merely stops and starts charging at around the 53v mark... the battery float voltage is 54.7, so there's certainly a problem somewhere there as it wont let the multiplus charge the battery to where it needs to be. I guess I'm going to have to park this until I can access the battery in person. Thank for your input, it's reassuring to have someone else confirm there is a problem other than my ineptitude.

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jeanmarie slartybart commented · May 14 at 10:49 AM

But SOC should not be an issue if DVCC is activated as this will tell your multiplus to consider the CVL/CCL to charge the battery.

Your battery is communicating as the display shows it,

is DVCC activated?

and what are the values in "Battery Parameter" tab for CVL / CCL / DCL?

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slartybart jeanmarie commented · May 14 at 11:20 AM

Yes DVCC is activated... but having changed the Battery protocol to Pylontech I see the options have now changed (see screenshot). Prior to that everything else was off.

As for parameters: se below.... but the Multiplus clearly isn't observing them.

Thanks again!

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screenshot-2024-05-14-at-131842.jpg (125.4 KiB)

screenshot-2024-05-14-at-131738.jpg (83.9 KiB)

slartybart slartybart commented · May 14 at 11:22 AM

Oh.... the rest of the DVCC settings:

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screenshot-2024-05-14-at-132114.jpg (121.2 KiB)

Answer 6 · 2024-05-14T13:58:27Z

jeanmarie answered · May 14 at 01:58 PM

Strange your "forced off" status

I don't have such option (only have the slider button to toggle between ON and OFF)

but SCS should also be off

Also strange that it doesn't follow the BMS informations?

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Answer 7 · 2024-05-14T15:41:10Z

zonnigbreda answered · May 14 at 03:41 PM

In the ESS assistant in your ve.config there is a dynamic voltage. If your defaults are like mine, they are too high. Lower these as they seem to override the ones in all the screenshots in the above answers

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Answer 8 · 2024-05-14T16:05:27Z

slartybart answered · May 14 at 04:05 PM

Thanks all. I reverted the BMS Protocol setting back to Victron, so the DVCC settings are normal again, and everything is off. Ironically the Pylontech setting started flagging High Voltage warnings! Having played a bit more…. I think the issue is simply this: for some reason the charge voltage is never allowed to get above 53.8. When it reaches this the multiplus ramps down to zero, then moments later back up to trying to inject 5000w etc. so while it’s almost certainly a BMS issue, as jeanmarie pointed out, the issue isn’t that the multiplus isn’t decharging to its limit, it is in fact it’s never filling up in the first place, so the sustain mode cut off kicks in. I’ve emailed the battery supplier and shall see what they say. Thanks again for everyone’s help.

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Answer 9 · 2024-05-14T16:38:23Z

jalle19 answered · May 14 at 04:38 PM

In addition to whatever BMS issues you may be having, verify what the ESS assistant dynamic cutoff values are. Those are very often preventing people from discharging to close to 0% while using ESS.

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Answer 10 · 2024-05-14T17:28:00Z

slartybart answered · May 14 at 05:28 PM

Thanks all. I thought the charge parameters in VE.Config were overridden by the BMS, but in case I'm wrong on that I've upped the float voltage to 55.2 as per battery instructions. It was previously set to 54... which is roundabout where, when charging, it keeps cutting out. The battery manual doesn't have an absorption setting so I've left the default 56.8 (it never reached anything like that voltage either!). While I'd have expected the Multiplus to continue charging until the BMS tells it the battery is full, if this setting is what the issue is, then at least now it shouldn't stop charging until it reaches 55.2v, which has got to be closer to full than 53.8 where it was stopping thus far...... It'll potentially need as much as 7kWh's so I'll wait until the price drops later on (saving me a potential 70p!) Let's hope it doesn't explode when I give it a go later on....

Jalle19.... I've actually upped the cut-off level from 37.2 to the manual's 43.2. I'm confident it's not reached either of those limits, but time will tell.

Thanks all for your help.

screenshot-2024-05-14-at-192626.jpg (134.4 KiB)

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slartybart commented · May 14 at 08:11 PM

Nope that didn’t work either.

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slartybart slartybart commented · May 15 at 08:36 AM

After an overnight charge at 1500w, controlled by limiting charger output in DVCC settings, the battery and individual cell levels seem to be looking healthier. The battery voltage was 53.5, or thereabouts, when I checked first thing. Now the sun is shining the voltage has risen to 54.3 and the individual cells are sitting at 3.4v, so it's still charging, but now at a slower rate but from the sun. Maybe there isn't a fault after all and I've just now been treating the battery badly.

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jeanmarie slartybart commented · May 15 at 09:12 AM

could be, yes

remember that Pylontech is one of the "tested" environment and it is well known that special parameters are considered when Pylontech batteries are detected, what exactly I don't know but certainly a reason detected by Victron during their tests

Also remember that Pylontech are 15S batteries with the consequence that the charging voltage must be limited to 53V, could be that this limitation is hard coded in GX software

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Answer 11 · 2024-06-17T11:09:57Z

slartybart answered · Jun 17 at 11:09 AM

Turns out the battery was faulty, or at least one of the cells. Everything working now as it should, finally! Phew!

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