The Battery Thread (Solar / Inverter)

[RonSwanson]

Would switching-off both battery and inverter during non-loadshedding periods be fine in terms of maintenance/care or should the entire system be left alone and switched-on 24/7?

It depends. What batteries?

 

[wingnut771]

It depends. What batteries?

Very true, I assumed it would be dead acid. If it's lithium then yes, you can turn it off and leave it, preferably at 50% SOC.

 

[SHL]

It depends. What batteries?

 

[Sayf777]

Would switching-off both battery and inverter during non-loadshedding periods be fine in terms of maintenance/care or should the entire system be left alone and switched-on 24/7?

Take advantage of the battery you have and use it as cost saving during non lol shedding periods.
Do you have 1 only?

 

[RonSwanson]

View attachment 1197484
View attachment 1197486

If you read the warranty on those, one of the (many) conditions is that it needs to be cycled on a daily basis.

 

[B-1]

Would switching-off both battery and inverter during non-loadshedding periods be fine in terms of maintenance/care or should the entire system be left alone and switched-on 24/7?

If its installed with a bypass then its not a problem but there are a few ways to get better life out of the batteries. Lipos are better to store at 50-60% charge rate vs Lead Acid which are better stored at 100%.
I don't think most installers will add the bypass unless you ask.

 

[maxxis]

Final update.

Decided on the 5kw Sunsynk with 2 x Hubble AM-2s.

Will stop feeding back into the grid to prevent a possible ****off big fine if council finds my meter spinning in reverse.

House will be powered from batteries during the night and grid if really needed during prolonged lack of sun.

Install happening first week in December when Hubbles are back in stock.

 

[SHL]

Take advantage of the battery you have and use it as cost saving during non lol shedding periods.
Do you have 1 only?

Yup only one.

 

[SHL]

If its installed with a bypass then its not a problem but there are a few ways to get better life out of the batteries. Lipos are better to store at 50-60% charge rate vs Lead Acid which are better stored at 100%.
I don't think most installers will add the bypass unless you ask.

There is a bypass.

 

[SHL]

If you read the warranty on those, one of the (many) conditions is that it needs to be cycled on a daily basis.

How do I ensure that this happens daily?

 

[JamesBoy]

Quick question for anyone that can answer please. On my 24V system (two 12V batteries in series) - if I swop my AGM batteries out for drop in replacement Lithium batteries would I match these voltage specs (listed below here for a single battery) by just doubling them up when I configure my inverter? This is of course after changing my battery type from AGM to User:

• Bulk voltage: 14.4 V (so 28.8 V?)
• Float voltage: 14 V (28 V?)
• Under-voltage cut out: 11.2 V (22.4 V?). Maybe I should up this to get to my preferred depth of discharge?

 

[RonSwanson]

How do I ensure that this happens daily?

Run them down in the evening, charge them in the morning.

 

[RonSwanson]

Quick question for anyone that can answer please. On my 24V system (two 12V batteries in series) - if I swop my AGM batteries out for drop in replacement Lithium batteries would I match these voltage specs (listed below here for a single battery) by just doubling them up when I configure my inverter? This is of course after changing my battery type from AGM to User:

• Bulk voltage: 14.4 V (so 28.8 V?)
• Float voltage: 14 V (28 V?)
• Under-voltage cut out: 11.2 V (22.4 V?). Maybe I should up this to get to my preferred depth of discharge?

It depends on the battery. A good Lithium replacement battery will have a BMS that is far smarter than the charger, has visibility of the state of the individual cells. and will have protection against excessively high temperatures, undervoltage, overvoltage, over-charge and over-current discharge. You set your charger to AGM / VRLA and the battery's BMS will look after it. There is no need to fiddle with manual settings.

 

[TheChamp]

Quick question for anyone that can answer please. On my 24V system (two 12V batteries in series) - if I swop my AGM batteries out for drop in replacement Lithium batteries would I match these voltage specs (listed below here for a single battery) by just doubling them up when I configure my inverter? This is of course after changing my battery type from AGM to User:

• Bulk voltage: 14.4 V (so 28.8 V?)
• Float voltage: 14 V (28 V?)
• Under-voltage cut out: 11.2 V (22.4 V?). Maybe I should up this to get to my preferred depth of discharge?

If it is a 24V system then you were already at double the voltage even with the AGM's, by selecting user you can match the inverter to the correct voltages as specified by the batteries.

 

[wingnut771]

It depends on the battery. A good Lithium replacement battery will have a BMS that is far smarter than the charger, has visibility of the state of the individual cells. and will have protection against excessively high temperatures, undervoltage, overvoltage, over-charge and over-current discharge. You set your charger to AGM / VRLA and the battery's BMS will look after it. There is no need to fiddle with manual settings.

That's because usually you can't set these values on the entry level inverters. If you can set them then do it and follow the values on the spec sheet.

 

[RonSwanson]

That's because usually you can't set these values on the entry level inverters. If you can set them then do it and follow the values on the spec sheet.

Even on more fisisticated inverters / chargers it's a lottery. Apart from the fact that lithium batteries do not adhere to Peukert's law, differing cable diameters and lengths make it almost impossible for the inverter / charger to accurately determine SoC, 0.25V difference could mean anything from 75-25%. That is why it's best left to the BMS.

 

[Tinuva]

Even on more fisisticated inverters / chargers it's a lottery. Apart from the fact that lithium batteries do not adhere to Peukert's law, differing cable diameters and lengths make it almost impossible for the inverter / charger to accurately determine SoC, 0.25V difference could mean anything from 75-25%. That is why it's best left to the BMS.

100000%

If my bms communication is down the inverter estimate the soc or charge level completely wrong.

 

[wingnut771]

Even on more fisisticated inverters / chargers it's a lottery. Apart from the fact that lithium batteries do not adhere to Peukert's law, differing cable diameters and lengths make it almost impossible for the inverter / charger to accurately determine SoC, 0.25V difference could mean anything from 75-25%. That is why it's best left to the BMS.

Sure I agree, but in a case where there is no comms to the BMS, then we have to rely on voltage and if one can set it manually using "user" then go for it, its better than using "agm" setting.

Look, I'm talking about these batteries:

 

[RonSwanson]

Sure I agree, but in a case where there is no comms to the BMS, then we have to rely on voltage and if one can set it manually using "user" then go for it, its better than using "agm" setting.

Look, I'm talking about these batteries:
View attachment 1197650 View attachment 1197654
View attachment 1197656 View attachment 1197658

Yes, Lithium lead replacement batteries typically have a BMS (and at the risk of getting off-track, not all BMSs are equal) and are typically without inverter/charger comms.
My point is that the BMS is (typically) in the best position to make key decisions, and not the inverter. This is so even in cases where the batteries do have inverter / charger comms. An example of this is the Pylontech US3000 which issues a mandatory charge command to the inverter when the battery SoC gets dangerously low.
Inverters can like to be clever, but battery BMSs are more clever.

 

[wingnut771]

Yes, Lithium lead replacement batteries typically have a BMS (and at the risk of getting off-track, not all BMSs are equal) and are typically without inverter/charger comms.
My point is that the BMS is (typically) in the best position to make key decisions, and not the inverter. This is so even in cases where the batteries do have inverter / charger comms. An example of this is the Pylontech US3000 which issues a mandatory charge command to the inverter when the battery SoC gets dangerously low.
Inverters can like to be clever, but battery BMSs are more clever.

All the BMS is doing in these battery's is cutting off if the cell voltage is too high or too low and if the load is too high and maybe a bit of top balancing when at absorption voltage.

I was responding to the question of "what do I do now if I change my AGM's for LFP, do I use "user" or leave it "AGM"".

I say, use USER setting because you can set the voltage to 14.4V instead of AGM setting of 14.1V, and can also set a less drastic low cut off off like 12V or something. Maybe even turn FLOAT off if possible.