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muddy1 asked

ESS bulk restart voltage causing stuck in float

I try not to be too hard on my Lifepo4 batteries so I charge to 56v and float at 53.6v. This worked fine with the MPPT charge controllers, but once I added ESS the problems began. The issue is the bulk reset voltage. On the charge controllers this is float -0.4v so bulk restarted at 53.2v, or around 80% battery capacity which was fine.

With the ESS system, Victron in their wisdom have chosen to set the bulk reset at float -0.8v

Why different ?

This means bulk does not restart until 52.8v. With the flat profile of Lifepo4 this is around 63% battery capacity, which is way too low. Until this point it just sits in float. If you heavily load the system to drop the voltage then it changes over to bulk without any problems, but sitting with a low load you lose a lot of charge time.

Does anyone know a way to adjust this bulk reset voltage ? I know I could float at a higher voltage but this seems a poor solution to the problem.

ESSfloat
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Alexandra avatar image Alexandra ♦ commented ·

@Muddy1

With ess assistant programmed the mppts go into bulk during the day as they are not dependant on your battery to trigger production? At least all the systems i have do.

So I would say your system is not set up correctly. Do you have a gx device in the system? It is one of the requirements.

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muddy1 avatar image muddy1 Alexandra ♦ commented ·

Hi Alexandra

Thanks for your comments. I have Venus 2.80 on my system.

Can you confirm you have ESS installed ?

The ESS manual says the bulk reset is based purely on the voltage.

"Note that these charge-cycle restart-mechanisms differ from the stand-alone MPPT Solar Charger algorithm: they restart the charge cycle every day."

Currently my battery is at 78%, it is early morning, the solar is just starting and I am still in float. I will leave it discharging and see exactly when something changes.
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Leslieanne avatar image Leslieanne commented ·

Hi there,

Perhaps I can offer some perspective. Our system comprises multi 11 48/5000, 4kW of solar AC coupled via a Goodwe inverter on AC1 out, and 1.5 kW solar DC on mppt 150/35, venus GX and BMV 702. Battery is 160Ah 16S Winston LFP cells with zeva BMS using 2-signal communication within ESS, exporting to grid from both AC and DC. Absorb set to 55.2 V, float at 53.6. Optimised without battery life, and 20% SOC floor.

In normal use, it will return to bulk in early evening or occasionally first thing in morning (cooking loads), all exactly as expected. BUT....when we are away from home on holiday and just baseloads running (including refrigerator, small irrigation pump), it will remain in float for a day or two, indeed until voltage falls to 52.8 V. This is usually around 70-80% SOC. Exactly as expected if you think about it, (but I was surprised the first time we were away and noticed it still in float the next day!) Cycling once every 2 or 3 days instead of once (or more) daily. Much easier on the batteries, and still plenty in reserve in case of blackouts. Plus we export all the excess to the grid.

Cheers, Leslie


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muddy1 avatar image muddy1 Leslieanne commented ·
Hi @Leslieanne

Thanks for your comments. Your observations are absolutely correct.

My system finally went to bulk at 52.7v and 65% state of charge. Pretty much as the manual says it will.

However 65% is a little lower than I am happy with. It is probably fine in summer when a reasonable amount of daily sunshine can be expected, but in the British winter I want to be able to have every minute of full power charging possible. Several dull days may follow when no energy is available. All my heavy loads are at night so I need to end the day with a good charged.

I think @victron could improve on the ESS software very easily. Clearly no one size fits all. By letting the user set the rebulk voltage, the system would be much more adaptable. Even better would be to allow the rebulk to be set on state of charge. This could be done in parallel with the voltage setting so either triggered bulk.


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