Trying to switch from flooded lead acid to lifepo4 batteries

carolinabigfoot

New Member
Joined
Sep 8, 2021
Messages
54
Location
Northwestern NC
My setup is as follows:
2 LG300N1K-G4 solar panels (Pmax 300W, Voc 39.7V, Isc 9.7A) connected parallel,
Morningstar ProStar-30 version ps-30m charge controller,
Samlexpower Pure Sine Wave inverter 24V, 1500W.

My 24V, 100Ah fla-battery bank died last week after 5 years of faithful service (R.I.P.).
I would like to replace it with a 24V, 200Ah lifepo4-battery bank, so I can possibly add a
DC freezer to my household appliances. Do I need to modify the rest of the setup to be
able to do that? If yes, in what way? The user hand book for the charge controller doesn't
mention lifepo4-batteries at all. I also think that Will suggested a 48V solar array to charge
a 24V bank (mine is 36V but has worked well with my 24V fla-battery bank). Any advice or
suggestions?
 

anadiner

Solar Enthusiast
Joined
Aug 10, 2021
Messages
300
2 things come to mind:
- when replacing batteries, u gotta put in same type and approximate age. So ouchie on ur wallet.
- make sure the new battery type is compatible with controller. Sounds like ur gonna need new controller. If not in manual, I wouldnt risk it.

Just replacing so of course dont change voltage. Sure u know that.

The 48v array... my advice is not to go messing with changing what works. Update batteries fine. New controller with same voltage, amps fine. Then leave it.

My 2 cents.
 
Last edited:

MisterSandals

Participation Medalist
Joined
Nov 5, 2019
Messages
4,800
Location
Silicon Valley
Morningstar ProStar-30 version ps-30m charge controller
You may be able to get a firmware update for this SCC.
I have a TriStar MPPT 45 and used the MSView application off their website to upload new firmware.
Even with that, my 10 year old SCC did not have an LiFePO4 setting, rather it had a user definable charge
profile that works with LiFePO4. Morningstar sent me a document with appropriate settings.
The settings are only configurable with the application which only runs on Windoze. But since updating firmware
and adding a new charge profile, its been a workhorse for well over a year now.

I cannot recall if the ProStar is updatable like the TriStar. Morningstar support is very responsive and helpful.
 

rmaddy

Full-time Solar-powered Trailer Life
Joined
Nov 16, 2019
Messages
1,222
Replacing your old FLA battery with LiFePO4 should only require updating the charge settings on your SCC. Your SCC seems to support a custom charge setup according to the user manual.

The only other change might be the main battery fuse. You might need a fuse that is bettered suited to LiFePO4 batteries such as a Class T.
 

chrisski

Photon Sorcerer
Joined
Aug 14, 2020
Messages
2,362
All I can think of is battery terminals, Housing, heating pads if temps drop below freezing are some of the things.

For the BMS, just needs to be sized for your loads. I don’t know about DC freezers, but I expect that to be a significant, but if the energy audit matches what your new battery and panels can handle then fine.

For the voltage, if you have been good the prior years, I don’t see why you would not be good now. I was watching my 66 volts of panels today, three in series, and when shade came across one panel there were significant voltage drops, low 40s, so that I see why Will would want to double panel charging voltage in a series. To be sure the SCC got enough voltage to charge, but this should not be a problem for your two panels in parallel.

I’ve just started charging my Lithium bank, and can’t help on settings. If there’s standard settings, equal to or less than what you want to charge at voltage wise for Bulk and float, but definitely equalization shut off completely.

I went with bulk of 27.5 and float of 27. I saw the charger go from bulk to absorption and then zerod out on amperage should have entered float, but did not.
 

carolinabigfoot

New Member
Joined
Sep 8, 2021
Messages
54
Location
Northwestern NC
Thanks for that info. I think I saw in the hand book online a custom charge profile, even though the charge controller that I have looks a little different from the one that is depicted in the hand book, although it has the exact same name (???). But there was another issue with the charge controller. On the day that I retired my battery bank the charge controller was charging it at bulk rate while the battery bank was literally boiling. It was a little scary when I opened up the box. It was very hot inside, there was a funny smell (presumably H2) and you could hear intense bubbling in the batteries. Now I wonder whether I can or should trust that cc at all. How can I figure out whether it is broken or not?
 

anadiner

Solar Enthusiast
Joined
Aug 10, 2021
Messages
300
All I can think of is battery terminals, Housing, heating pads if temps drop below freezing are some of the things.

For the BMS, just needs to be sized for your loads. I don’t know about DC freezers, but I expect that to be a significant, but if the energy audit matches what your new battery and panels can handle then fine.

For the voltage, if you have been good the prior years, I don’t see why you would not be good now. I was watching my 66 volts of panels today, three in series, and when shade came across one panel there were significant voltage drops, low 40s, so that I see why Will would want to double panel charging voltage in a series. To be sure the SCC got enough voltage to charge, but this should not be a problem for your two panels in parallel.

I’ve just started charging my Lithium bank, and can’t help on settings. If there’s standard settings, equal to or less than what you want to charge at voltage wise for Bulk and float, but definitely equalization shut off completely.
Thanks for that info. I think I saw in the hand book online a custom charge profile, even though the charge controller that I have looks a little different from the one that is depicted in the hand book, although it has the exact same name (???). But there was another issue with the charge controller. On the day that I retired my battery bank the charge controller was charging it at bulk rate while the battery bank was literally boiling. It was a little scary when I opened up the box. It was very hot inside, there was a funny smell (presumably H2) and you could hear intense bubbling in the batteries. Now I wonder whether I can or should trust that cc at all. How can I figure out whether it is broken or not?

I went with bulk of 27.5 and float of 27. I saw the charger go from bulk to absorption and then zerod out on amperage should have entered float, but did not.

Thanks for that info. I think I saw in the hand book online a custom charge profile, even though the charge controller that I have looks a little different from the one that is depicted in the hand book, although it has the exact same name (???). But there was another issue with the charge controller. On the day that I retired my battery bank the charge controller was charging it at bulk rate while the battery bank was literally boiling. It was a little scary when I opened up the box. It was very hot inside, there was a funny smell (presumably H2) and you could hear intense bubbling in the batteries. Now I wonder whether I can or should trust that cc at all. How can I figure out whether it is broken or not?
Ohhh, scarey cuz those batteries were sulfated and releasing gas= they're done.

Also, Im fan of series to parallel to keep amps low, in hand wiring cost down.

BUT remember, series is only as good as its worst performer. Like if 1 panel in shade, ur entire array performs badly. Circuitry 101.

Luckily, MPPT controllers now provide wiggle room on voltage. They tend to be lithium friendly so check compatible
 
Top