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Float charging

Featured Replies

Hi there, inverter recently got an firmware update, since then I have been losing +/- 15% of battery over night, check the float charge, and it is not disabled... will share some images

  • Author

Screen shots of charge loss was with system mode on 100% for all times and grid charge 1700 to 1800... was a week of rain... I use the posted system mode on sunny days/weeks

  • Author

Could only find this one example of the battery float charging and staying constant from earlier this month. Since grid charge was not selected in system mode, the battery was kept at currrent state of charge after power was restored.

Screenshot_20231020_190517_Sunsynk Connect.jpg

  • Author

Now the battery trickles 20w into the system instead of the grid trickling to the battery to keep constant charge

Screenshot_20231020_190855_Sunsynk Connect.jpg

Edited by ChrisDied

I see a lot of this inverters that can mix solar grid and battery (sub) do at times trickle at night around 20w from the battery . It's normal .

A friend  growatt can at times  consume  from his 5kw Hubble around 8% over the night when not charging from the grid 

  • Author
23 minutes ago, GMAC said:

I see a lot of this inverters that can mix solar grid and battery (sub) do at times trickle at night around 20w from the battery . It's normal .

A friend  growatt can at times  consume  from his 5kw Hubble around 8% over the night when not charging from the grid 

I get that, but it never did this before frimware upgrade, that is what float charging was for, to keep at a certain level for prolonged periods of time. If loadshedding would end at 20:00, and battery was at 60%, it would stay at 60% til pv became available

11 hours ago, ChrisDied said:

I get that, but it never did this before frimware upgrade, that is what float charging was for, to keep at a certain level for prolonged periods of time. If loadshedding would end at 20:00, and battery was at 60%, it would stay at 60% til pv became available

Litium batteries do not float. Once they reach 100% SOC no further current will make it into the cells. Even if your inveter is showing a (by example 60W) float charge being supplied to the batteries none of that will make it into the battery cells. Self discharge is almost non existent in these batteries.

In lead acid batteries, once fully charged Amps leak from positive to negative inside the cell, microscopically dropping the cell voltage over time. Big player in lead acid batteries but almost zero in a LFP cell.

The only accurate way to determine what is causing the "reported" gradual reduction in SOC is to see what is actually happening with the BMS and individual cells, using something like PBMS Tools.

This will likely be a communication issue causing incorrect SOC readings to be shown by the inverters. Have you tried the AGM setting to see if the same happens. Make sure your charge settings are correctly set in the inverter. 

Edited by I84RiS

@ChrisDied the Sunsynk 5kW seems to self consume between 70 and 100W, this usually, unless the battery is being charged, comes from the battery, so overnight, even if you run off the grid, the inverter will run its internal power usage from the battery, this may be to allow a quicker switch over to battery power, if the grid should fail, but this is only a theory and no actual valid data to back this up.

I don't know what the 8kW unit and the others self consume, I suspect a similar amount, which pretty much means that if you run two 5kW units instead of a 8kW unit, you are wasting a lot more energy on the inverters' self consumption end. Also if one does not know of this fairly high self consumption amount and you are budgeting tightly with battery capacity to keep things alive without the gird about, you may just come horribly short, since overnight the inverter will self-consume pretty much 1kWh from the battery. (assume 85W average and 12hours before more sunshine on panels and you are at 1020Wh for the night of purely keeping the inverter functioning)

  • Author

Got this screen shot from one of my friends with deye inverter, you can see the inverter feeding the battery 24w to keep it close to 100%, mine did exactly the same, but seems to have stopped after recent firmware update, now battery is either 0w or feeding the plant 20-30w constantly

IMG-20231020-WA0008.jpg

  • Author
10 hours ago, Chris_S said:

The discharge is a bit extreme. Can you post your battery settings and Libms screen. 

Sorry missed your post, i attached all of those.

20231021_152712.jpg

20231021_152732.jpg

20231021_152738.jpg

20231021_152745.jpg

  • Author

One thing i also noticed now is that the Run led on the battery keeps blinking, where as it was always solid for most of the time before, but could just be mistaken also

1 hour ago, ChrisDied said:

Got this screen shot from one of my friends with deye inverter, you can see the inverter feeding the battery 24w to keep it close to 100%, mine did exactly the same, but seems to have stopped after recent firmware update, now battery is either 0w or feeding the plant 20-30w constantly

IMG-20231020-WA0008.jpg

None of that 24w actually makes it into the cells, these are not LA batteries.

  • Author
55 minutes ago, I84RiS said:

None of that 24w actually makes it into the cells, these are not LA batteries.

Ok i get that, but is losing 17-20% charge overnight normal?

  • Author

Ok I redid all the settings to just the same, and something seems to have changed, atleast the battery isnt draining at 20w now... no idea what the issue was?

Screenshot_20231021_181746_Sunsynk Connect.jpg

22 hours ago, ChrisDied said:

I get that, but it never did this before frimware upgrade, that is what float charging was for, to keep at a certain level for prolonged periods of time. If loadshedding would end at 20:00, and battery was at 60%, it would stay at 60% til pv became available

In the new update they must have changed how the inverter works .but agree 15% used is a lot through the night .

First image is luxpower .

Second image is deye 

And lost is growatt and as you can see growatt has the highest consumption with about 6% battery used at night lithium is an Hubble am-2 5.5kw 

Screenshot_20231021-191010_1.jpg

Screenshot_20231021-190716_1.jpg

Screenshot_20231021-190630.jpg

Edited by GMAC

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