Best discharge level?

[pda1]

My system is a 1.5 kW array feeding into 2 series BB LifePo batteries as a 24v system.

The batteries, because of the way I use them rarely get below 98% state of charge (hope that's the correct term).

Question; am I harming the batteries by not reducing their state of charge to a very low level?

Is there something I should do that will extend the life of the batteries?

Thanks,

Peter

 

[740GLE]

Battle Born? Or Big Battery? Big big difference in manufactures.

What voltages are you running with your SCC?

1.5kw PV for 100ah 24v system is very PV heavy, but if the SCC settings are conservative you’ll be fine.

 

[HRTKD]

It depends on what a 100% state of charge means to you. If you're charging to 29.2 volts then yes, that's not good for your batteries. Maintaining the cells at such a high state of charge will reduce their life cycle. If you're charging to only 28 volts (or so) then that's not too bad. My batteries in my RV trailer sit at 100% for a couple months at a time, but 100% for my system is 14.1 volts in the off-season and 14.2 volts when the trailer is actively being used.

See this thread for suggested charge settings.

Recommended Charge Profile for DIY LiFePO4 Batteries *Sticky Post*

12V 4S LiFePO4 Battery w/ BMS: Absorption: 14.5V Float: 13.6V Inverter Cut-off: 10.7V-12V (depending on size of load and voltage drop etc) 24V 8S LiFePO4 Battery w/ BMS Absorption: 29V Float: 27.2V Inverter Cut-off: 21.4V-24V 48V 16S LiFePO4 Battery w/ BMS Absorption: 58V Float: 54.4V...

diysolarforum.com

 

[Any name you wish]

I have a similar setup. You can drop your boost charge to 60 min and charge at 3.45/cell, then float at 3.35/cell. High charge rate will heat up the cells so be cautious.

 

[pda1]

Battle Born? Or Big Battery? Big big difference in manufactures.

What voltages are you running with your SCC?

1.5kw PV for 100ah 24v system is very PV heavy, but if the SCC settings are conservative you’ll be fine.

Battle Born.

I just looked at the settings on my Victron 150/60- Absorption is 28.4v for 40 minutes. Float is 27v

These figures I got directly from Battle Born concerning my system.

 

[pda1]

I have a similar setup. You can drop your boost charge to 60 min and charge at 3.45/cell, then float at 3.35/cell. High charge rate will heat up the cells so be cautious.

Do you mean HRTKD's system? Don't know what "Boost" is.

 

[Any name you wish]

Do you mean HRTKD's system? Don't know what "Boost" is.

I have an array about the same size, using a 24V 100Ah battery. Boost is what my SCC charge at until they reach float.

 

[HRTKD]

My Victron Energy 100/50 solar charge controller defines three charge phases in the manual (plus equalization, but that's for flooded lead acid) and there are three LED's for these phases on the device.

Bulk
During the bulk stage the solar charger delivers the maximum charge current, to rapidly charge the batteries. During this stage the battery voltage will slowly increase. Once the battery voltage has reached the set absorption voltage, the bulk stage stops and the absorption stage will commence.
The above phase does not show up in my VictronConnect app.

Absorption
During the absorption stage the solar charger has switched to constant voltage mode. The current flowing to the battery will gradually decrease. Once the current has dropped below 2A (tail current), the absorption stage stops and the float stage will commence. When only shallow discharges occur the absorption time is kept short. This to prevent overcharging of the battery. But if the battery was deeply discharged, the absorption time is automatically increased, to make sure that the battery is fully recharged.

Float
During the float stage the voltage is reduced and batteries full charged state is maintained.

 

[Danke]

If one has excess battery capacity, will batteries last longer is only charging to a certain SOC, say 90%?

 

[HRTKD]

Both are beneficial. The extra capacity means that you don't have to draw down as far and there is less stress on each battery (assuming multiple batteries) when the draw uses high amps.

 

[740GLE]

Only down side to more battery capacity is a lighter wallet ?

 

[brb58]

If one has excess battery capacity, will batteries last longer is only charging to a certain SOC, say 90%?

yes but you need to occasionally fully charge to balance the battery cells...occasionally could be as often as once a month.