800Ah FLA to Lithium

[Alloy]

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.

I build the system with 8-6V that are spit into 4 sets of 2-6V with a disconnect, 200A fuse and 4/0 identical length cables to each bank.


Componets are:
1.3Kw (panels in parallel) roof top solar Victron 250/100
1.3Kw portable solar Victron 150/100
Midnight Solar breakers/disconnect for roof top solar
3000W Victron Multiplus (110V pass thru) Inverter
600W Xantrex Inverter
Victron BMV-712
Victron Color Control GX
Pronautic 50A programmable (back up) charger
Honda 2000w Generator




The RV is used in temperatures down to 0F. At that temperature the battery box will be +/-15F. Probably get warmer since venting will not longer be needed and there's room for insulation.

Easiest route would be to buy 4 - heated 100Ah Lithium. I'm thinking BB for the warranty and heating when there is no charging.

What are the options (cells and BMS) if I build a 5kw lithium bank(s) myself? One of Two banks or split it into four banks?

 

[Rocketman]

Here is the battery I made and my RV setup:

Batrium Watchmon Install

Hello everyone, I have a 2000 Monaco MotorHome, I will be installing eight 272ah Lishen LiFePo4 cells making a 2p4s 12v 500Ah (useable) battery. My two largest loads are a Victron MultiPlus 12/3000 inverter/charger and the engine "Boost" if my chassis battery gets low. For the BMS I chose a...

diysolarforum.com

I liked the experience of making my own battery.

A couple of items: you need to make sure no charging lithium’s when they are too cold. The Victron mppt’s have a low temperature cutoff. The Multiplus does in the Victron connect app but not through the computer program with the MK3. I just ordered the VE.BUS dongle (it should arrive today), so I can set the low temperature cutoff on the Multiplus.

Bms’s: I choose to go with the Batrium BMS, and I like it a lot. Costs a little more, but if you make a large battery it won’t be that much more than a bunch of other bms’s. Look at the Batrium core with a K9.

 

[Alloy]

Here is the battery I made and my RV setup:

Batrium Watchmon Install

Hello everyone, I have a 2000 Monaco MotorHome, I will be installing eight 272ah Lishen LiFePo4 cells making a 2p4s 12v 500Ah (useable) battery. My two largest loads are a Victron MultiPlus 12/3000 inverter/charger and the engine "Boost" if my chassis battery gets low. For the BMS I chose a...

diysolarforum.com

I liked the experience of making my own battery.

A couple of items: you need to make sure no charging lithium’s when they are too cold. The Victron mppt’s have a low temperature cutoff. The Multiplus does in the Victron connect app but not through the computer program with the MK3. I just ordered the VE.BUS dongle (it should arrive today), so I can set the low temperature cutoff on the Multiplus.

Bms’s: I choose to go with the Batrium BMS, and I like it a lot. Costs a little more, but if you make a large battery it won’t be that much more than a bunch of other bms’s. Look at the Batrium core with a K9.

Thank you

Batrium has 4 temp sensors ?

I had the factory VE. Bus dongle but found it didn't provide enough range so I picked up a Gembird P/N WNP-UA-002

 

[HRTKD]

Many off-the-shelf LiFePO4 batteries with "Low Temperature Protection" will warm the battery only when a charge source is applied. What this means is that your batteries could be sitting at 20° F at 8 am (winter) when the solar panels start to get enough sunlight to generate amps. It could take 2 hours for the batteries to come up to an acceptable temperature before the BMS allows them to be charged. You've lost 2 hours of charging time.

The solution I chose to implement is to keep the batteries always above 35° F so that charging can start as soon as the solar charge controller has enough juice from the solar panels.

Batteries are very dense and tend to retain heat fairly well. A well insulated battery can do even better. I have mine insulated with 1" and 2" of rigid foam on the sides and top, respectively. I don't log how often my warmers come on, but my guess is that it may happen no more than a couple of times overnight, if that.

More details of my install here:

LiFePO4 Battery Warmer Install

This is my install of a custom set of battery warmers from Ultra Heat. I had contacted them through email asking about a warming profile for LiFePO4 batteries. They responded with a design to my specifications, including warming pads that fit my batteries exactly. While I initiated the...

diysolarforum.com

 

[Alloy]

Many off-the-shelf LiFePO4 batteries with "Low Temperature Protection" will warm the battery only when a charge source is applied. What this means is that your batteries could be sitting at 20° F at 8 am (winter) when the solar panels start to get enough sunlight to generate amps. It could take 2 hours for the batteries to come up to an acceptable temperature before the BMS allows them to be charged. You've lost 2 hours of charging time.

The solution I chose to implement is to keep the batteries always above 35° F so that charging can start as soon as the solar charge controller has enough juice from the solar panels.

Batteries are very dense and tend to retain heat fairly well. A well insulated battery can do even better. I have mine insulated with 1" and 2" of rigid foam on the sides and top, respectively. I don't log how often my warmers come on, but my guess is that it may happen no more than a couple of times overnight, if that.

More details of my install here:

LiFePO4 Battery Warmer Install

This is my install of a custom set of battery warmers from Ultra Heat. I had contacted them through email asking about a warming profile for LiFePO4 batteries. They responded with a design to my specifications, including warming pads that fit my batteries exactly. While I initiated the...

diysolarforum.com

Thanks
Five years ago heating and temp disconnect is why I didn't go with Lithium. Lithium has come along ways in 5 years.

What is the temperature differential of the controller you're using?

Our Fall, Winter temperature hover around 32F so I like being able to save power by bring "on" temp for the heating pads down to 35F. The heating pads don't draw much but small current draws add up.

 

[boondox]

That doesn't appear to be a 12kWh system. If those batteries are 120aH and you have them in a 2s4p configuration then:

12V * 120aH = 1440 Wh.
1440 * 4 = 5760Wh.

If that is all true then you probably have been beating on the batteries pretty hard as at 50% SOC you had an effective 2,880wH bank. Nonetheless, you will be able to fit more lithium for less weight and space. If you get 4 * 12V, 100Ah batteries you will have a 4.8kWh bank. If you want to go no lower than 20% SOC that gives you an effective 3,840Wh bank.

 

[HRTKD]

Thanks
Five years ago heating and temp disconnect is why I didn't go with Lithium. Lithium has come along ways in 5 years.

What is the temperature differential of the controller you're using?

Our Fall, Winter temperature hover around 32F so I like being able to save power by bring "on" temp for the heating pads down to 35F. The heating pads don't draw much but small current draws add up.

Are you in the RV full time?
Is the front compartment heated?

If the answer to both of those is yes then you probably don't need any supplemental warming system for the batteries.

I use a programmable thermostat. I currently have it turning on at 35° F and off at 45° F.

 

[Alloy]

Are you in the RV full time?
Is the front compartment heated?

If the answer to both of those is yes then you probably don't need any supplemental warming system for the batteries.

I use a programmable thermostat. I currently have it turning on at 35° F and off at 45° F.

Not in it full time.....it would be easier if I was. I'd want a controller with a smaller differential. I'll do 2 independent systems because I don't want to cut a trip short due to saving a few $$.

 

[Alloy]

That doesn't appear to be a 12kWh system. If those batteries are 120aH and you have them in a 2s4p configuration then:

12V * 120aH = 1440 Wh.
1440 * 4 = 5760Wh.

If that is all true then you probably have been beating on the batteries pretty hard as at 50% SOC you had an effective 2,880wH bank. Nonetheless, you will be able to fit more lithium for less weight and space. If you get 4 * 12V, 100Ah batteries you will have a 4.8kWh bank. If you want to go no lower than 20% SOC that gives you an effective 3,840Wh bank.

Good you're checking up on me?

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

 

[Sojourner1]

Wouldn't the Crown bank be 940ah with 8 6v batteries at 235ah not 800ah?

Alloy there are many option that can be had but I would seriously look at HRTKD setup he attached for cold weather and it seems to be working nicely in Denver cold temperatures.

Losing 300-350# in battery weight won't hurt either going with 4-500ah lfp.

Can't the Crowns be rejuvenated some?

 

[Supervstech]

Wouldn't the Crown bank be 940ah with 8 6v batteries at 235ah not 800ah?

Alloy there are many option that can be had but I would seriously look at HRTKD setup he attached for cold weather and it seems to be working nicely in Denver cold temperatures.

Losing 300-350# in battery weight won't hurt either going with 4-500ah lfp.

Can't the Crowns be rejuvenated some?

Where did he say 800Ah? His math shows 940Ah 11938Wh

 

[Sojourner1]

The title of the thread.

 

[Supervstech]

Good you're checking up on me?

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

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.

 

[HRTKD]

Not in it full time.....it would be easier if I was. I'd want a controller with a smaller differential. I'll do 2 independent systems because I don't want to cut a trip short due to saving a few $$.

Mine is programmable. Set the range and lower temperature to whatever you want.

 

[Sojourner1]

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'll bet he wouldn't need the same size if going with lfp. Heck, I fulltime in my 5th wheel with only 500ah & 1,280w solar and live as hooked up to a power pole everyday not conserving power. But all our needs are different.

 

[time2roll]

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.

 

[HRTKD]

PV and LiFePO4 are a lot like ammunition. You can never have too much.

 

[corn18]

PV and LiFePO4 are a lot like ammunition. You can never have too much.

I need more PV, LiFePO4, guns and ammo.

 

[Supervstech]

I'll bet he wouldn't need the same size if going with lfp. Heck, I fulltime in my 5th wheel with only 500ah & 1,280w solar and live as hooked up to a power pole everyday not conserving power. But all our needs are different.

Idk… KWh, is KWh… sure, lithium is more efficient than Fla, but if that is what he was using, that is what he will need…

 

[Sojourner1]

Idk… KWh, is KWh… sure, lithium is more efficient than Fla, but if that is what he was using, that is what he will need…

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.