800Ah FLA to Lithium

[Alloy]

Until the OP responds we'll know for sure.

Here he says "It's time to replace the 12Kw (never really was) FLA system in my RV that I built 5 years ago. All I'm getting is 2Kw before the voltage is 12.1V. I used to be able to go 2-3 days using 1kw/day when there was no sun but now the system needs to be charged everyday with a generator."

1kw/ day is not that much at all and with FLA it's all about having the multiple day reserve to ride the storm out and not "having" to run the generator. I believe lfp can eliminate the need for multiple day reserve if one doesn't want to drop excessive amount of cash on batteries. The OP has a fair amount of solar and with the inverter/ charger he can charge off of the generator for an hour or two to give a "boost" to his SOC to hold over for a better solar day charge instead of the marathon charge cycles for dead lead. Using the lfp for long periods of partial SOC isn't going to hurt them like FLA as we can see/ know.

The purpose of the 800Ah (940Ah) FLA bank was to able to go 5-6 days and still be above +/-50% but in real life it was only 2-3 days.

Crown has a 2 year warranty so after a year of being at +/- 50% after using 2-3Kw I took 2 back to the dealer. They used a starting battery load tester and said the batteries are 100%. Since then I've installed a few more FLA brands and never had any meet the 20Ah load rating.

For the FLA to match the usable capacity of Lithium I'd need add 40% more capacity so the weight saving vs. Lithium would be closer to 400-500lbs.

With Lithium I won't have to check the BMS to see if the batteries are 100% because it doesn't matter. No more running the generator for hours and hours in float hoping to extend the life of the FLA.

 

[wiseacre]

With Lithuim I won't have to check the BMS to see if the batteries are 100% because it doesn't matter. No more running the generator for hours and hours in float hoping to extend the life of the FLA.

and that is a great point. I have a grid down, backup system I tied an Moes ATS to so I could use some power. With AGMs and typical sunless days on end during the winter I had to either shut down the system or constantly hook up a charger to keep the batteries from sitting at harmful low charge levels. Going to LFE took the hassle out of the set up, the batteries actually like not being fully charged.

I don't have to worry about space or weight but can see how it can be a major factor in a RV.

 

[Alloy]

Hard to assume this is a low budget build with Crown batteries and a Multiplus inverter. I would about fill that compartment with LFP cells.
Too much is barely enough.

You're correct. My method has always been to spend $$$ on materials then learn and save money on labor. Spending more makes it durable and building it means I can repair it.

 

[Alloy]

Of course with FLA, dropping below 50% is bad, so 5969Wh maximum draw… recommended. If you’ve been drawing 12KWh out, you’ve been destroying the poor babies…

To match what you’ve been using, I’d get five 200Ah sok which would get you a usable 12,800Wh and cost less than the battleborn, and have low temp protection enabled on your cc… along with sealing up the bay, and insulating.

I never liked to go below 12.1V. The Victron BMV was set at 11.8V but in the last year if the batteries weren't 100% the load from the microwave tiggerd the alarm so the BMV is at 11.0V now.

 

[Alloy]

Can't the Crowns be rejuvenated some?

Probably but not to the point that they'll do what I want. Each bank can be equalized separately but it takes a day for each bank. Last time I did it was a year ago.

 

[Sojourner1]

When you make the switch over and get some time with them you should be a happy camper. Not to even mention the ability to run high draw items at low SOC without the inverter shutting down. My inverter is set at 12.0 lvd and never have had it shutdown even at 25% SOC using the 12c coffee maker or large microwave.

 

[boondox]

Good you're checking up on me?

6v are Crown CR-235 so 235Ah x 4 x 12.7v = 11,938w

Hehe! oops. Never mind.... ?

 

[Alloy]

Of course with FLA, dropping below 50% is bad, so 5969Wh maximum draw… recommended. If you’ve been drawing 12KWh out, you’ve been destroying the poor babies…

To match what you’ve been using, I’d get five 200Ah sok which would get you a usable 12,800Wh and cost less than the battleborn, and have low temp protection enabled on your cc… along with sealing up the bay, and insulating.

Why SOK?
Not including shipping.... . . .
4 x 200Ah SOK is $4,100.00US for a total of +/-10Kw
16 x 280Ah EVE cells is $1,900US for a total of +/-14Kw + I'd need a BMS

For heating Lithium below 35F the SOK case is more of a hindrance than a help.

 

[HRTKD]

Why SOK?
Not including shipping.... . . .
4 x 200Ah SOK is $4,100.00US for a total of +/-10Kw
16 x 280Ah EVE cells is $1,900US for a total of +/-14Kw + I'd need a BMS

For heating Lithium below 35F the SOK case is more of a hindrance than a help.

SOK for those that don't have the patience of LiFePO4 cells coming on a slow boat from China.

I don't disagree with your heating argument against SOK. Heating a battery case isn't as efficient as heating the cells directly.