Is this a good setup for small DIY battery bank?

andruby

New Member
Hi,

I'm new to this forum. I recently bought a small trailer to go on short (1~3 day) weekend trips.

I'm thinking of buying the following components for a DIY battery bank:
I want to run some low-power LED lights, a 100W fridge (can run on 220V/12V/Propane), and an 800W water kettle for tea :)

I'm planning on doing a basic setup without solar first, but want to be able to extend it later with solar and a couple of 12V loads.

basic and later.jpg

Questions:
  1. I haven't seen Will talk much about inverter/chargers, nor have I found much on this forum. Are they a good idea? From the website of the manufacturer, it seems like they should be ok to charge Lifepo4 batteries at a 140W rate. Or am I better off getting a separate (and cheaper) inverter and charger?
  2. Do the components and combination make sense? Am I missing anything?
  3. If the inverter comes with a fuse, does that mean I do not need to add a fuse between the battery and the inverter?
  4. Should I connect 12V loads to a fuse box connected to the battery or should I connect them to solar controller DC load connection?
  5. Most pure sine-wave inverters are expensive. Which appliances are fine to run on a modified sine-wave inverter? Is there a way to find out without buying and trying?
  6. (crazy thought) Is it possible to charge the batteries by connecting the car's 12V output to the (cheap PWM) solar controller solar-input?
Thanks!
 

Kcp

Solar Enthusiast
Just my thought on your fridge, it's a 3 way which means it's absorption which means it's a power hog on electric so keep it on propane.

Also 800w ac for tea is about 80ish amps dc.

So rundown:
1. dunno.
2. Basic and Later mean you're learning and heading to v3. I'd just recommend a Battleborn or Lion Energy battery with BMS to cut off the fluff while learning.
3. Depends. Inside cheaper inverters are a few fuses so one more from inv to batt won't hurt.
4. Solar load connection are OUTPUT not INPUT so ignore they exist for now.
5. Anything with motors with a mod-sign is bad- if you have a Dremel plug it into a mod-sign and your hand will burn up in 15 secs. These days pure sign is the way to go.
6. The alternator wires directly to the aux. battery via a battery isolator.
 

Dzl

Unofficial Forum Librarian
Staff member
Moderator
View attachment 8096

Questions:
  1. I haven't seen Will talk much about inverter/chargers, nor have I found much on this forum. Are they a good idea? From the website of the manufacturer, it seems like they should be ok to charge Lifepo4 batteries at a 140W rate. Or am I better off getting a separate (and cheaper) inverter and charger?
  2. Do the components and combination make sense? Am I missing anything?
  3. If the inverter comes with a fuse, does that mean I do not need to add a fuse between the battery and the inverter?
  4. Should I connect 12V loads to a fuse box connected to the battery or should I connect them to solar controller DC load connection?
  5. Most pure sine-wave inverters are expensive. Which appliances are fine to run on a modified sine-wave inverter? Is there a way to find out without buying and trying?
  6. (crazy thought) Is it possible to charge the batteries by connecting the car's 12V output to the (cheap PWM) solar controller solar-input?
Thanks!

  1. Inverter-Chargers are fine. The Victron Multiplus is a popular option, but $$$$. Will has made a few videos on the MPP Inverter/charger/solar charge controller all in one (video here).
  2. Can you link to the fuse box you had in mind, most people use individual breakers or fuses for the major components, and use a fuse box for 12v and/or 120v loads
  3. Remember, the primary role of a fuse/breaker is to protect the wire not the device. So yes, I think it is important to still fuse between the battery and the inverter (though i'm unfamiliar with how to fuse an inverter/charger combo). Check your product manual it will have specific guidelines.
  4. Check your charge controllers documentation, there will be a diagram.
  5. This is not a super straightforward question, the simple rule of thumb I have heard is some appliances with motors (like tools and fridges) and sensitive electronics require pure sine. But its somewhat more complicated than that. Here are a couple (one, two) partial lists of devices that should use pure sine.
  6. Not sure, probably not safely, maybe not at all (voltage might be too low). There are better ways to accomplish this, DC-DC chargers, Victron makes one and Renogy makes one, and Sterling power makes one.
 
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