how does boost float recharge works on SRNE?

I got settings set at 56.4v boost for 10 minutes 54v float and 43.6v on setting #37 Battery fullycharged recoverypoint.


What my inverter does is it charges up to 56.4 then instantly stops charging battery and all load is via pv only. A small discharge of 35w is drawn of batteries.

After 10 minutes nothing changes.

At 54v nothing changes

at 53.6 it starts to charge and goes up to boost value of 56.4 and repeats.

Why wont it stay at float and why wont it hold boost voltage value for 10 minutes.. isnt that indented behavior?

If I understand it correctly there is no float (#11) when operating with lithium battery selected. You have boost/bulk (Constant current) until you sustain voltage and than (Constant voltage) for the time duration in setting #10. As you note if loads bring down battery voltage to your recovery setpoint you go back into Boost charging.

is the timer seconds or minutes? It says Minutes but those 10 minutes was over in 10 seconds lol. And the max value 900 seem dumb if it was minutes... that is 15 hours. Gonna try the value 600 see if if behaves better

Reason you need boost time is to allow BMS to balance cells. BMS's typically do not balance unless an LFP cell is above 3.4v.

Some hybrid inverters and PV charge controllers have a timed boost phase, some use charge current taper down level to exit boost phase.

Check if boost timer is set to zero. Setting #10 is boost timer. Recommend setting it to 120 minutes to give some balancing time, longer if you do not boost more than once month or so, depending on your BMS balancing current and battery AH size. If you don't allow balancing for several months you may need longer boost timer to get cells back in balance.

Many hybrid inverters regulate the battery voltage to the charger voltage set level. When they drop from absorb (boost) phase to float phase they will try pull the battery down to float voltage if they can. 'If they can' means if grid back feed is allowed, or AC output load is available to dump the battery power to drop it to float voltage.

I don't see any setting to manage boost phase retrigger battery voltage. This is often non-user setting at some voltage level below float voltage or minimum timer period of several hours. If you have too much voltage drop in battery cabling, with high load current, it can retrigger a boost phase.

If you want to manually balance battery you can set boost to same voltage as float and use the manual equalize mode settings, set to your desired boost voltage and time length for battery balancing. Then you manually trigger an 'equalize' cycle to balance battery.

Scph9002 said:

is the timer seconds or minutes? It says Minutes but those 10 minutes was over in 10 seconds lol. And the max value 900 seem dumb if it was minutes... that is 15 hours. Gonna try the value 600 see if if behaves better

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It is minutes but you have to understand that it can cut off based on how the logic in your controller thinks the batteries state of charge is. I run two AIO's off one battery bank and the one is set for a lower boost voltage. Once it hits it and keeps rising it does not time out but simply stops charging altogether (the charge light goes out) while the other AIO continues to its Boost voltage setting to begin the timer. I have mine set to 120 minutes (default).

Mattb4 said:

It is minutes but you have to understand that it can cut off based on how the logic in your controller thinks the batteries state of charge is. I run two AIO's off one battery bank and the one is set for a lower boost voltage. Once it hits it and keeps rising it does not time out but simply stops charging altogether (the charge light goes out) while the other AIO continues to its Boost voltage setting to begin the timer. I have mine set to 120 minutes (default).

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ah i see thanks

A setting of 3.525 voltage per cell as boost for 10 minutes and 3.25volt as rebulk/reboost seem like a good set and forget value? My JKbms is set to balance cells who get past 3.53v. @Mattb4

Scph9002 said:

A setting of 3.525 voltage per cell as boost for 10 minutes and 3.25volt as rebulk/reboost seem like a good set and forget value? My JKbms is set to balance cells who get past 3.53v. @Mattb4

Click to expand...

That setting is no balancing.

RCinFLA said:

That setting is no balancing.

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does it need balancing if no single cell go above 3.53v with a current of 0.01c ?

Scph9002, did you solve this charging problem? I have the same problem

Same problem here. It ignores float all together and just keeps draining the battery till it hits the set recharge point. Its like float does nothing.
Battery is set to use which should honor the float setting.

Open or closed loop?

What are you using for setting 8? If set to User you should be able to control your boost and float voltage and times. You will also have to coordinate those with setting 37 for recharging. 43.6 is really low. I would recommend setting it closer to your float voltage in order to initiate a full charge cycle each day. Change your boost time to 60 to 90 minutes and then see how the system behaves.