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nickdb asked

ESS multi/mppt staying in float

I have a multi/mppt ESS setup that runs on a schedule with a 75% hard SOC limit and a stop at 80% SOC in the schedule.

Due to load the SOC hit 75% within a couple of hours during the night and reverted to grid as expected.

The inverter state was "float".

The inverter at no stage changed from float to bulk/absorption so when charging started it worked it's way to 80% and stopped.

Despite tons of PV available it trickle charged all day to a rather miserable SOC.

Any insight into why the inverter did not change to bulk/absorb?

We have identical installs and they all behaved correctly.

Multiplus-IIMPPT ControllersESS
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nickdb avatar image nickdb ♦♦ commented ·

Having the same issue today. Inverter will not change from float. The other two systems operating fine, the only difference being this system having hit the hard SOC limit.

Remote console displays ESS #1 #2 - state is discharge disable.

These inverters have the same batteries, same float voltage settings but only 2 are changing to bulk/absorb.

Any pointers appreciated.

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nickdb answered ·

It seems the SOC and the actual battery charge got properly out of sync.

Doing a remote multi reset forced a short bulk/absorption cycle and after a few minutes the inverter decided the SOC was in fact 100%.

Under-reading would have triggered all the failsafes early and resulted in a bit of a mess.


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Vangelis Beligiannis avatar image Vangelis Beligiannis commented ·

Resetting always leads to bulk-absorbtion. Try to discharge the batery more than usual and see what happens the next day without reseting.

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Vangelis Beligiannis answered ·

There is a minimum voltage that the battery must fall below, in order to trigger a new charge cycle, after an initial charge cycle has been completed.

For a 12V system the restart bulk voltage is Vfloat-1,6V.

So try to discharge your battery lower than you normally do to see if this will change.

Note that the restart voltage mentioned above cannot be changed by the user.


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nickdb avatar image nickdb ♦♦ commented ·

I am aware of this and what is confusing is that identical systems with a higher state of charge are happily bulking/absorbing and rarely actually float.

I did a side by side comparison on configs and found this multis float voltage was 0.2V lower than the others and the absorb voltage 1.2V higher, so I have amended the config but I am not 100% convinced yet.

I got to the bottom of the PV usage issue. When batterylife kicks in battery discharge is disabled and this prevents PV from being used for AC loads.

With the inverter in float it is drawing a miserly 180W from PV to charge, compared to 1300W of an identical system.

Changing modes to exclude battery life at least prevented it from going to grid for the AC loads.

ESS is quite frustrating at times, it is quite slow. An option to force a bulk charge would be helpful now.

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