ARB fridge with LiFePO4 in a dual battery setup

soul

Observer
The clear advantage I see are 1) Weight 25lb versus 70lb for 100AH capacity 2) 80% usable capacity, versus 50% 3) 3000 cycles, versus 300 so more battery life 4)Robust & leak proof 4) Higher charging current, shorter time to charge if we want to charge on using Main Supply. We should see the price going down in this year, as many folks are getting into manufacturing for the EV autos.
 

Xterabl

Adventurer
Great! Thanks for the follow up!
I think your first two links in your post are dead, though.
But, everything else seems really nice and detailed.
Thanks again for this effort!
 

dwh

Tail-End Charlie
(Just now catching up with this thread...)


2) 80% usable capacity, versus 50% 3) 3000 cycles, versus 300 so more battery life 4)Robust & leak proof 4) Higher charging current, shorter time to charge if we want to charge on using Main Supply.

Yes and no.

2) True.

3) True if discharging to 80%. However if you stick to the 50% rule, most deep cycle lead-acid have an expected lifespan of around 1000 cycles:
DOD-LIFECYCLES.jpg



4) AGMs are also robust and leak-proof as long as they are not overcharged.

4) (yes, two 4s - don't blame me :D ) Maybe, maybe not. Odyssey recommends C*4 max charge current - that would be 400 amps for a 100ah battery. Lifeline and Optima have no specified current limit - as long as the battery is not allowed to overheat. Those are of course AGMs. Typically open cell deep cycle lead-acid batteries will specify C/4 or 25a per 100ah.
 

soul

Observer
Update! I have now added 120 Watt Solar Panel to the dual battery setup. The fridge has been running over 2 months by itself.
The nightly drain on battery seems to be charged fully within first few hours of sun light.

WP_20150418_13_53_09_Pro-DreamW8 (1280x722).jpg

WP_20150418_13_54_22_Pro-DreamW8 (1280x722).jpg

WP_20150418_13_53_47_Pro-DreamW8 (1280x722).jpg
 

ash121

New member
Hi Soul
Thank you for an excellent post.
I also have the same ARB fridge and have followed your setup using Winston cells, and the same BMS, same DC-DC step-up set to 14volts output and the same Bioenno Solar controller.
I had 2 questions for which I thought you may have simple answers.

1). I am occasionally getting a burnt out fuse (30A) on the feed from my car's alternator into the solar controller.
Rather than directly wiring a feed from the battery with the isolator inline (as per your schematic), I was using the cigarette plug in my boot (wired for 30A) that is only live when the ignition is on. I thought this would serve the purpose to only charge the LifePO batteries when the car is running and then isolate the system when the car is switched off. Could this be the source of the fuse burnout, perhaps at engine start-up when Amps surge from the alternator?
I am getting a voltage reading of 2.35v at the solar panel terminals with no power feed from the alternator (and the cells fully charged signalling P2 from the controller) but I checked with Bioenno and they said that this was normal.

2). I was keen on any feedback on your choice of 120W solar panel. Which panel did you choose and would you still recommend this panel?

Many thanks for any advice
Cheers
Ash
 

ash121

New member
Thanks Verkstad. I am still learning about interactions at play here.....

I realise it might be difficult to comment without more input on peak Amps etc.
However, just to clarify in the schematic provided by Soul (see below), do you think that if I independently wired the feed from the alternator rather than use the car's boot wiring I would avoid the 30Amp burnouts?
Pictorial Schematic.jpg

I note that Soul uses a 30A fuse in his alternator feed without issue.

Perhaps my VW Touareg alternator puts out more than 30A at times or is it only the draw of the fridge that dictates the peak Amp draw?
 

Cefurod

New member
I'm new and just trying to learn all this stuff. After reading this thread and learning about the lifepo4 batteries for the first time, I would like to do a single 12v setup to power a 50 or 60L fridge. I want to recharge by solar only without connection to the car battery. What is my best way?
 

jonyjoe101

Adventurer
lifepo4 is a 4s 12.8 volt battery which is similar to lead acid voltage. Any charge controller mppt or pwm can charge that. As long as the lifeepo4 battery has a BMS, it will stop accepting charging when it reaches full charge, and it will also shutoff power when it reaches low voltage. The battery BMS will make sure it doesnt go out of balance when charging or discharging.

In my case I have a 94 amp hour 3s lithium battery (11.1 volt, fully charge 12.6 volts) and charge it using only my ecoworthy 20 amp mppt charge controller, no special lithium controller required. The bms on the battery always shuts off charging when full but i do have a relay that will disconnect the solar panel when battery reaches 12.6 volts.

You do need a relay, otherwise when the bms shutsoff, in my case it still shows battery voltage (11.7 volts) and the controller will still try to charge it. You need a small dc overvoltagerelay (about 8 dollars) and connect a bigger 30/40 amp relay (about 5 dollars) between solar panel and controller. The small relay will trigger the big relay. You set the max voltage you want not to be exceeded. You also set the lower voltage where you want the solar panel reconnected.

Even if the relay shutoff the charging before you are fully charge ,its not a big deal, lithiums dont required to be fully charge everytime like lead acid. They will last longer when not fully charged.

overvoltage relay
overvoltage relay.jpg

standard 12 volt relay
relay.jpg
 

sCir

New member
I've essentially duplicated this setup in my Defender 110. I used the same components OP used and followed his schematic. The batteries have worked flawlessly and provide days of power to my ARB fridge. I'm about to add a 100 watt solar panel to the mix and now I see in OP Soul's schematic a "Solar Protection Diode." My understanding is that most solar panels have a blocking diode built-in, so I wonder if he's just showing that, or if he added another diode for some reason. Soul - are you out there? Care to comment?
 

spikemd

Explorer
I am no electrical engineer but I do find it interesting that Goal Zero has come out with lithium ion power packs but they are not rechargeable through a 12v plug, only 120v or solar. Not sure of the electrical complications of why since the charge controllers and battery management systems are built in and the power packs range from $700 to $2000, but thy don;t. My buddy just bought a Yeti 1000 lithium so we will be testing it next week for 10 days on an expedition vs my yeti 400s. I am curious to see how it handle solar power and if it will hold up without powering while we are driving between destination.
 

Not-required

New member
Thanks Verkstad. I am still learning about interactions at play here.....

I realise it might be difficult to comment without more input on peak Amps etc.
However, just to clarify in the schematic provided by Soul (see below), do you think that if I independently wired the feed from the alternator rather than use the car's boot wiring I would avoid the 30Amp burnouts?
View attachment 340318

I note that Soul uses a 30A fuse in his alternator feed without issue.

Perhaps my VW Touareg alternator puts out more than 30A at times or is it only the draw of the fridge that dictates the peak Amp draw?
The alternator will only put out what the circuit demands.

Sent from my SM-G950U using Tapatalk
 

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