Lithium vs deep cell

[Missylab]

I have a midnight 150 charge controller, multiplus 3000w 24v inverter. This is a seasonal camp that freezes in the winter. I’m undecided on batteries. I’m having an argument with friends and I don’t understand. Lithium vs. deep cell. Power storage, and winter maintence.

I’m confused about power storage. You can discharge a deep cell 20% and lithium up to 80%/ is there really a difference since you need a certain ah to run the inverter? Which one has more available power or is it the same.

Winter storage. If I turn the inverter off and have the deep cell fully charged will it last for a few months in freezing temperatures? Lithium has the BMA so it should be all set?

Thanks!

 

[sunshine_eggo]

I have a midnight 150 charge controller, multiplus 3000w 24v inverter. This is a seasonal camp that freezes in the winter. I’m undecided on batteries. I’m having an argument with friends and I don’t understand. Lithium vs. deep cell. Power storage, and winter maintence.

I’m confused about power storage. You can discharge a deep cell 20% and lithium up to 80%/ is there really a difference since you need a certain ah to run the inverter? Which one has more available power or is it the same.

I don't know what a "deep cell" is. If you're referring to a deep cycle lead acid battery, you really don't want to go below 50% regularly.

Winter storage. If I turn the inverter off and have the deep cell fully charged will it last for a few months in freezing temperatures?

Again, if you're referring to a deep cycle lead-acid, specifically an AGM type, then yes. They are very tolerant of extremely low temperatures, and cold temps slow their rate of charge loss. A fully charged AGM stored at or below freezing will retain charge for a VERY long time. I would estimate no more than 10-15% loss per year.

Lithium has the BMA so it should be all set?

Lithium has a BMS, but not all BMS protect batteries from freezing.

How often to you utilize these systems - frequency, duration and seasons? If this system just sits there doing nothing most of the time, AGM is a far more reliable and cost-effective option than LFP.

 

[Missylab]

I was referring to lead acid. Let’s say I had (4) 6v 225ah deep cell lead acid for my 24v system or (2) 12v 225ah lithium batteries. Do they have the same usable power or does lithium have more because you can discharge it 80%.

 

[Missylab]

I don't know what a "deep cell" is. If you're referring to a deep cycle lead acid battery, you really don't want to go below 50% regularly.



Again, if you're referring to a deep cycle lead-acid, specifically an AGM type, then yes. They are very tolerant of extremely low temperatures, and cold temps slow their rate of charge loss. A fully charged AGM stored at or below freezing will retain charge for a VERY long time. I would estimate no more than 10-15% loss per year.



Lithium has a BMS, but not all BMS protect batteries from freezing.

How often to you utilize these systems - frequency, duration and seasons? If this system just sits there doing nothing most of the time, AGM is a far more reliable and cost-effective option than LFP.

I use them from may-October, mostly on weekends temps can get -20f. This is in western maine. I lead acid batteries crack, but I didn’t turn off the inverter and snow usually covers the solar panels.

 

[Ampster]

Do they have the same usable power or does lithium have more because you can discharge it 80%.

The Lithium has more usable power. When choosing between the two types it is imortant to take that into consideration. In summary one might not need the same number of Lithium Ahr capacity as one my need in lead acid batteries for the same use case.

 

[sunshine_eggo]

I was referring to lead acid. Let’s say I had (4) 6v 225ah deep cell lead acid for my 24v system or (2) 12v 225ah lithium batteries. Do they have the same usable power or does lithium have more because you can discharge it 80%.

Yep.

I use them from may-October, mostly on weekends temps can get -20f.

So, for 5 months out of the year, you use it every weekend. By my estimation that's about 40 cycles per year.

This is in western maine. I lead acid batteries crack, but I didn’t turn off the inverter and snow usually covers the solar panels.

If you allow lead acid to discharge, they can freeze, but they are good down to about -80°F when fully charged.

So the issue here is that you did not engage in best practices, and your battery suffered. Now you're considering spending MORE on batteries that are less suitable for your application and more sensitive to mistakes.

Simply put, LFP is cost effective due to the high cycle life. When you factor in the amount of energy they can deliver over their lives, they have a lower cost of ownership than AGM. LFP is NOT cost effective for infrequently cycled or standby (like a UPS) operations.

IMHO, given your situation - extreme cold and infrequent use, you will enjoy far fewer issues with quality AGM than you would with LFP.

Simply leave the AGM fully charged and COMPLETELY disconnected when you leave for the winter, and they will be nearly fully charged upon your return. By completely disconnected, I mean NOTHING AT ALL that can draw a current - including a battery monitor, or anything else. Literally completely disconnect them - remove all wires to them.

 

[Missylab]

Ok thank you!!!