Vehicle battery advice

[07Quoia]

All, I am looking to provide continuous battery power (on 1-2d camping trips) to a Dometic CFX3-75 fridge through a Blue Sea 12V panel in back of SUV that I would direct-wire to battery. Current 12V cigarette plug turns off when ignition is off. This would be mostly parked at one location so may not start up vehicle during this time; really no additional power draws during this time.... what recommendations would you have for long-lasting, deep cycle AGM batteries? A Northstar AGM 27M has been suggested but they are quite expensive.. Thx

 

[spressomon]

You want to add an auxiliary battery into the engine compartment right? I've not used Northstar but have been using Odyssey for both starting (Group 31) and auxiliary (Group 34, PC1500) battery locations in my UZJ100 for over 14 years and IMHO they are worth the $$; good value and payback IMHO. I have been getting 10-years out of them typically).

If you sit for more than 36-ish hours without alternator charging you're going to want to think about alternate charging for the aux battery. Not sure what the CFX-3-75 draws but I'll bet its 4Ah +/- (many factors to consider including electrical cable loss, ambient temperature, internal compartment temperature, etc.). So very 24-hours it may consume 80 amps-ish...figure that into your calc.

I assume you have an isolator picked out to electrically separate the two batteries? And be sure to run decent size copper (ground and positive) from front to back...to allow future expansion)...6AWG would be good if going internal routing.

 

[07Quoia]

You want to add an auxiliary battery into the engine compartment right? I've not used Northstar but have been using Odyssey for both starting (Group 31) and auxiliary (Group 34, PC1500) battery locations in my UZJ100 for over 14 years and IMHO they are worth the $$; good value and payback IMHO. I have been getting 10-years out of them typically).

If you sit for more than 36-ish hours without alternator charging you're going to want to think about alternate charging for the aux battery. Not sure what the CFX-3-75 draws but I'll bet its 4Ah +/- (many factors to consider including electrical cable loss, ambient temperature, internal compartment temperature, etc.). So very 24-hours it may consume 80 amps-ish...figure that into your calc.

I assume you have an isolator picked out to electrically separate the two batteries? And be sure to run decent size copper (ground and positive) from front to back...to allow future expansion)...6AWG would be good if going internal routing.

Spressomon - I have a 1st Gen Sequoia, so running second battery would require quite a bit of engine compartment rework.. Want to use a primary battery only (the starting battery) to power fridge even if vehicle is off. The 75 DZ energy consumption is rated at 1.43 Ah/h @ 90F ambient temp. I am considering a Goal-Zero and solar panel in the future. Agreed on your suggested 6AWG for internal routing.

 

[spressomon]

Can you retrofit a Group 31 into main battery slot? Slee makes a kit for the UZJ100 that may fit (or not). That would provide a little extra insurance.

Are you mainly overnight camping?

Also, I carry a 12v lithium battery pack system for emergency jump starting, powering LED lights, charging phones, pads, laptops, etc. You will definitely want one in your one battery does it all strategy...in addition to being able to easily bridge my 2nd and 3rd batteries on my rigs; good insurance.

The other strategy, would be to think about incorporating a LFP (LiFePO4) 75-100A battery in the back as your rear side electrical source then feed it with a DC-DC charger with specific LFP charge/maintain profile and/or solar.

Many, many different tools to slay this animal...just have to think it all through.

 

[07Quoia]

Can you retrofit a Group 31 into main battery slot? Slee makes a kit for the UZJ100 that may fit (or not). That would provide a little extra insurance.

Are you mainly overnight camping?

Also, I carry a 12v lithium battery pack system for emergency jump starting, powering LED lights, charging phones, pads, laptops, etc. You will definitely want one in your one battery does it all strategy...in addition to being able to easily bridge my 2nd and 3rd batteries on my rigs; good insurance.

The other strategy, would be to think about incorporating a LFP (LiFePO4) 75-100A battery in the back as your rear side electrical source then feed it with a DC-DC charger with specific LFP charge/maintain profile and/or solar.

Many, many different tools to slay this animal...just have to think it all through.

Thanks - I'd have to look into the Group 31 retrofit... I don't have an extra 12v lithium battery pack system but do have an always-charged NOCO system for emergency self jump-starts.. I'll have to give this all some more thought.

 

[e9999]

Your basic problem is that I don't think that a typical 100Ah battery would last 2 days with a typical fridge. So just the one starting battery may not cut it, you'd need a much bigger one, but it may not fit easily under the hood. Enter the second battery and/or solar system approach...
An iffy cheap approach would be to let the fridge empty the battery and use your jump starter for the engine. That's fine -hopefully- for the engine in an emergency but your fridge may still end up dead with food issues. This could be mitigated somewhat by starting with a bunch of frozen water bottles in the fridge. Or frozen food. It may then last long enough. But still not a reliable approach. Basically you need to have enough energy for the fridge stored someplace, or replenish it. Of course, the easiest may be to run the engine for a bit if that's possible.

 

[sdnative]

I think you should be ok with a single larger group 31 battery if you are just running just the fridge for 1-2 days if:

you can supplement with solar
and have a portable jump pack just in case.

You may be able to get away with the factory group 27 if you want to add more solar and you get enough sun daily. Maybe a 100-200W panel with built in controller that has a kick stand so that you can place in direct sun. Pop the hood and connect directly to the battery.

Also good insulation on the fridge to keep it from cycling as much as possible will help a lot as well.

I would just use a high quality FLA not AGM but that's another discussion.

 

[07Quoia]

I think you should be ok with a single larger group 31 battery if you are just running just the fridge for 1-2 days if:

you can supplement with solar
and have a portable jump pack just in case.

You may be able to get away with the factory group 27 if you want to add more solar and you get enough sun daily. Maybe a 100-200W panel with built in controller that has a kick stand so that you can place in direct sun. Pop the hood and connect directly to the battery.

Also good insulation on the fridge to keep it from cycling as much as possible will help a lot as well.

I would just use a high quality FLA not AGM but that's another discussion.

Thanks - was considering the Northstar 27M but will see if I actually have room for a Group 31.

 

[ducktapeguy]

For 1-2 days you won't have a problem. Just fit the largest capacity battery you can in the engine compartment, then jumper the relay to keep the rear outlet powered at all times.

The important thing to do is add a few layers of water bottles, pre-freeze as much as you can before the trip, and don't put warm items in the fridge to cool them down. This will drastically reduce your power consumption. Basically treat the fridge like an ice chest and you can probably handle up to 3 days. A fridge full of frozen water, set to maintain a temperature just above freezing, will last 4-5 days with minimal power. If you do drive during the trip, set fridge to run at 100% while the engine is running to take advantage of the alternator power. I ran on the stock battery for a couple years this way, it works fine but it will shorten the life of your starter battery.

 

[4x4tripping]

This is my current setup: an Ecoflow River Pro Battery Box - and 50w EFTE Solarpanel

Overlanding offgrid power solution with solar - https://vanlife.4x4tripping.com/2021/06/vanlife-offgrid-power-solution-solar.html

It is strong enough to run the fridge extended just with solar.

That means - you can even go with a less strong battery. But this ecoflow device will keep everything cool too, if there is a week of rain.

Small, just 8.5kg - and powerful!

trippin

 

[07Quoia]

For 1-2 days you won't have a problem. Just fit the largest capacity battery you can in the engine compartment, then jumper the relay to keep the rear outlet powered at all times.

The important thing to do is add a few layers of water bottles, pre-freeze as much as you can before the trip, and don't put warm items in the fridge to cool them down. This will drastically reduce your power consumption. Basically treat the fridge like an ice chest and you can probably handle up to 3 days. A fridge full of frozen water, set to maintain a temperature just above freezing, will last 4-5 days with minimal power. If you do drive during the trip, set fridge to run at 100% while the engine is running to take advantage of the alternator power. I ran on the stock battery for a couple years this way, it works fine but it will shorten the life of your starter battery.

Good advice, appreciate it !

 

[07Quoia]

This is my current setup: an Ecoflow River Pro Battery Box - and 50w EFTE Solarpanel

Overlanding offgrid power solution with solar - https://vanlife.4x4tripping.com/2021/06/vanlife-offgrid-power-solution-solar.html

It is strong enough to run the fridge extended just with solar.

That means - you can even go with a less strong battery. But this ecoflow device will keep everything cool too, if there is a week of rain.

Small, just 8.5kg - and powerful!

trippin

Thanks Trippin !

 

[FJ Silver]

This is the most bang for $...

I build this is in the back of my FJ62, wiring is tidier now...

100 Ah in LifePo (4 cells x 25ah) - $100 + $50 in shipping
BMS (Manages the charging, load balancing, temperature control etc.) - $120
Not so smart Shunt to keep track of in and out coming current - $40

The Redarc BCDC I already owned,its about $350... I highly recommend getting one of those. My alternator only puts out 50 amps and I don't want to put any load on my main battery outside of starting/running the car.

And then I have an pure sign wave invertor hooked up to it all as well as my Twin ARB compressor + Fridge.

Its working so well...100AH with lithium goes a long way...

 

[sdnative]

100 Ah in LifePo (4 cells x 25ah)

Do you mean 4x 100Ah cells (in series for a 12.8V nominal battery)?

 

[FJ Silver]

Do you mean 4x 100Ah cells (in series for a 12.8V nominal battery)?

No they're actually 3.28 Volts per cell. X4.
All sorts of ways you can set this up depending on the amount of AH or voltage you'd like. 100 Ah is enough for my needs right now. But you can buy 4 100 ah cells @ 3.28 Volts each, they're only like $125 per cell. I buy them here in Utah.

 

[sdnative]

You need 4x 3.2V 100Ah cells in series for a 12.8V 100Ah battery. If your cells are 25Ah and you connect 4 of them in series you have a 12.8V 25Ah battery.

 

[FJ Silver]

Ah you're right... I'm conflating with an old set up. I did end up spending around $700 on getting to a 100 ah.