Switching Toy Hauler FLA's to building a Lifepo4 12v 4s and upgrading Solar

notTobyG

New Member
Joined
Mar 2, 2021
Messages
5
I figure the beginners corner is the best place for these questions and my 1st post.

I've kick the idea around for a while but, I think I'm ready to make the jump to building my own Lifepo4 4s 12v battery for our toy hauler. Currently the trailer is running two FLA 12v's

The trailer is currently set up with a OEM 300w solar panel flat on the roof and a 30A MPPT controller with a 1000 watt PSW inverter that only controls the outlets on the trailer. The plan is to keep the existing solar set up and add another portable 315w solar panel (off old trailer). I don't see the flat panel producing any where close to it potential which is why I think I should be fine not upgrading the solar charge controller but, if needed would it be acceptable to just add another 30a charge controller (I already have)?

Next I will take the existing PSW inverter and swap it for my 3000 MSW inverter I was using in a previous trailer. (I will upgrade the wires accordingly) Reason being in the old trailer we ran the entire trailer off the inverter enabling us to use the Keurig, microwave and TV etc. Family likes the amenities minus the noise from the Gene.

Finally the battery, I plan on using the EVE 304Ah cells 4s paired with a 200a BMS. They would be located less than 3 feet from the inverter and charge controller. I'm considering this 200a BMS by JBD. I'm skeptical of the source (no reviews) but, didn't really want to wait for a slow boat to deliver it. Open to suggestions or substitutes on BMS's.
Obviously I would have the necessary fuse's and breakers for the portable solar panel I was adding to the system.
My questions are:
1. Are there any Items I missed?
2. The EVE cells have a .5c discharge rate. Is that going to be a problem for my 3k inverter? I can't think of a time when we would be using more than 2000w through the inverter at one time.
3. Always open to suggestions of a better way to set up the system.
4. any issues running a MSW inverter for the microwave, TV or Keurig? It worked on the old trailer for 3 year no issues.

Thank you
 

notTobyG

New Member
Joined
Mar 2, 2021
Messages
5
Just thought of another question. Will starting my 4k Onan generator be an issue with a .5c discharge rate? Thank you in advance
 

notTobyG

New Member
Joined
Mar 2, 2021
Messages
5
34 views and no responses.... Did I do something wrong? Do I need to move this to another section?
 

WoodsieLord

Solar Enthusiast
Joined
Oct 4, 2019
Messages
141
Hello there,

but, if needed would it be acceptable to just add another 30a charge controller (I already have)?
If I recall correctly you should have no problems. Each MPPT should have it's own panel(s).
Regarding DIY LFPs and BMS I don't have the knowledge.
Noting that my limitied experience is with a stationary project, consider the following:

a. Regarding chargers...
I recently went the LiFePO4 way (prebuilt rackable batteries, not DIY as I said) replacing lead acid. In my case, my inverter-charger does not "support" lithium so I configured the parameters manually to match as good as possible what the battery requires.
I can configure the low voltage limit in 0,5V steps. This is AWFUL. When testing, I tried setting to 25.0V and after discharging the BMS shut off first due to low voltage. So I set the low limit to 25.5V and the inverter switches back to grid leaving a 10 - 15% unused.
b. Regarding the C rating, the maths as I understand them is that you have 304Ah * 0.5C = ~150A. This means the pack would theoretically be able to deliver 150A max. 150A * 13V =~ 2340W ...and you should consider the equipment efficiency is not perfect. So If I'm not dumb and got the maths right you should be able to pull (continuously) around 2000W max.
c. If your charger doesn't support lithium, the voltage can drop a significant amount when pulling lot of power. My 25.5V low voltage setting is triggered when I turn on my small A/C at night. I tested lowering the low voltage setting to 25.0 and the A/C runs fine, the load does not exceed the battery specifications. So it could be a problem? I guess it depends on your charger... ?

b. State of charge. You didn't mention this. I would add any kind of shunt solution to have an idea of the battery status. You can't rely on voltages so if the inverter has a battery indicator, it won't work as you expect.


Please note that I'm still a newbie.
PS: I usually get lured by posts with pictures of people's solar equipment. Maybe you can try that to get more replies
 
Top