I want to upgrade batteries to Lithium for off-grid cabin

[Chri5co63]

A solar array that i installed for another person consists of twelve 195w panels connected to a six-string PV Combiner Box, for a 24v system, to a 3000w PowMr solar charger inverter, currently with four 12v 100ah Sealed lead acid batteries (He would like to upgrade to Lithium batteries, to at least double, or triple, the storage capacity). Which is better, 12v batteries at 100 ah, hooked in the same manner my SLA batteries are configured, or would 24 v batteries be better? And if 12 v or 24 v batteries are recommended, which ah rating... 100, 200, 250? and which BMS rating...100, 200, 250? and How many? And connected in what array (series/parallel)?
Also, does the AH rating determine the discharge rate or would that be the watt hours? I want to upgrade to a battery bank that will take more time to discharge. But with that does it mean that it would also take longer to re-charge?
As soon as I think I've got it figured out, I watch another video that doesn't quite answer my question and I get confused all over again.
Not asking much, right?

 

[Mattb4]

Generally you are better with 24v batteries because than you only have one bms controlling 8 cells in series, versus 2 BMS controlling 4 cells each series connected together. However some BMS work just fine being hooked in series so you need to find out if the battery you are interested supports this.

AH rating is the batteries capacity based on the ability to sustain voltage above a minimum during an even loading over a period of time. Often that is a 20 hour period. Thus 100ah battery will run a 5a load for 20 hours. You may see different ah ratings depending of the hours of discharge such as C5=70ah for a C20=100ah battery. Look up Peukert effect. Although promulgated for lead acid much of it is true for all chemical batteries. Also wh is correlated to ah by multiplying ah by battery voltage. 100ah X 12vDC = 1200wh

If you discharge a battery you must recharge it and this rate of recharge should not exceed manufacturers recommendation. Most often this is expressed a some percent of C (C being amp-hr rating). So for a .1C of a 100ah battery you would want to keep it at 10 amps. .3C = 30a and so on. The higher the amperage rate you charge at the more you strain the battery and shorten its longevity.

There is some loss between discharging battery ah and recharging ah capacity. Say you discharge 50ah. It may take 55ah to recharge.

 

[Chri5co63]

Well, today is the day that I will be installing our new batteries and hoping all goes well. ?

The following are the steps I plan on doing for this install:

1. Turning off the Solar Panels at the Combiner Box, so no PV will be coming in to the PowMr
2. Turning off the PowMr Inverter Charger
3. Disconnecting + and - wiring of the old batteries from the PowMr
4. Turning on the PowMr to set all the parameters for the new batteries.
5. Turning off the PowMr (once all new parameters are set)
6. Removing the old batteries
7. Connecting the four new Chins 12v 200ah batteries together in 2S/2P array
8. Connecting + and - wire battery bank to PowMr
9. Turning on the Solar Panels at the Combiner Box
10. Turning on the PowMr Inverter Charger

If this seems to be correct, or if there is anything that I should doing differently... please let me know.

 

[Mattb4]

Well, today is the day that I will be installing our new batteries and hoping all goes well. ?

The following are the steps I plan on doing for this install:

1. Turning off the Solar Panels at the Combiner Box, so no PV will be coming in to the PowMr
2. Turning off the PowMr Inverter Charger
3. Disconnecting + and - wiring of the old batteries from the PowMr
4. Turning on the PowMr to set all the parameters for the new batteries.
5. Turning off the PowMr (once all new parameters are set)
6. Removing the old batteries
7. Connecting the four new Chins 12v 200ah batteries together in 2S/2P array
8. Connecting + and - wire battery bank to PowMr
9. Turning on the Solar Panels at the Combiner Box
10. Turning on the PowMr Inverter Charger

If this seems to be correct, or if there is anything that I should doing differently... please let me know.

Step 4 can only be done when connected up to the battery. No reason to set it until after you hookup the new batteries. But the rest of the sequence of disconnecting solar first and battery last followed by reconnecting battery first and solar last is the standard.
Thus step 1,2,3,6,7,8,4,9

 

[Chri5co63]

Step 4 can only be done when connected up to the battery. No reason to set it until after you hookup the new batteries. But the rest of the sequence of disconnecting solar first and battery last followed by reconnecting battery first and solar last is the standard.
Thus step 1,2,3,6,7,8,4,9

Thank you so much!

 

[Chri5co63]

Next question….
Can Chins 12v200ah batteries be stacked on top of each other?
When we ordered these batteries, we were not on location where they are to be installed (here now). The space of the old lead acid batteries is much less than the new batteries. (Didn’t EVEN consider the space dimension) ??
So am wondering if they can be stacked like in the pic (or I could build a shelf of sorts for the top two batteries to sit on, if that’s better).
The second photo is our current setup, with the old batteries still installed…

 

[Mattb4]

I would not want to stack one on top of another (as pictured) unless the manufacturer had stated it was a OK to do so. Even than it would bug me. It might be perfectly doable but it is one of those, "it don't look right to me", type of things.

 

[Chri5co63]

Well, there it is! All installed and setup. I set the parameters on the inverter as suggested (the 2nd suggested) parameters from Chins. The only variation was on Parameter #15… Chins suggested the Battery Discharge Limit Voltage to be set at 22.2 volts, however the Inverter would only allow it to be 21.0 v (I went through the parameters many times and tried re-setting #15 to 22.2v, but each time I followed up to check all settings, #15 would always read 21.0 v (hopefully, it’ll be ok that way (??)).

Also, for Parameter #7, is still a questionable setting for me as it refers to the “Maximum Charging Current “. Chins recommended 40A (which I did set it at), however with the old lead-acid batteries, it was set at 60A.
In the PowMr Manual it states under the description for this parameter, “Max. Charging current = utility charging current + solar charging current” (60A is Default). It goes on to read “The maximum solar charging is 60A, the maximum Grid/Utility charging is 40A (adjustable in Program 28), totaling the maximum current of 100A. The range can be between 0 - 100A).

I find this confusing.

P.S. the Parameter 28 (“Program 28” as the manual refers to it) is the “Maximum AC Charging Current”, with a setting of 40A (Default) and with adjustable between 0 - 40A