Auxiliary battery connection

[crdv6]

I need some advice on how to connect another battery to the car (Jeep of course).
I simply want to be able to run the car fridge for a while when stopped for a few hours, not indefinitely.
I was thinking of a light weight lithium battery, portable arrangement. My question is, how to use the battery in conjunction with the vehicle's power to run the fridge when the car's power supply switches off, and charging the second battery.
I see some lithium battery packs with a built-in DC-DC charger, but I don't understand exactly how this works.
I need a how-to for dummies on this!

Sent from my CPH1979 using Tapatalk

[Mace1]

The simple way is to fit a suitable battery isolator (directly connected to the main battery) somewhere in the engine bay (usually right next to the main battery)

Such as:

https://www.autobarn.com.au/smart-ba...YaAroIEALw_wcB

Then run suitable heavy duty wiring from the isolator to the second battery stored elsewhere in the rear of the vehicle, in something such as:

https://www.autobarn.com.au/powered-...QaAtvlEALw_wcB

The wiring to the second battery can either be run along/within the chassis rail and then taken inside the cab via a strategically drilled hole in the floor (thru a grommet or otherwise sealed with a suitable product), or taken thru the firewall along with any other wiring that enters the cab and run beneath the carpet to the battery box location.

Then connect fridge to battery box via an anderson plug (as shown as the grey plugs on the top of the battery box) or other 12V connecter.

The isolator allows the second battery to be charged via the vehicles main battery and alternator when the vehicle is going, but also prevents excessive charge drop in the main battery when the vehicle is stopped.

The second battery will most likely cover all the power requirements your fridge requires for the timeframe mentioned.

If you are handy with the tools a good project for a day to install. A good auto elec might charge $200 to $300 for the install, plus the cost of above mentioned goods, but I have heard of people being ripped off and charged much more...

Hope that helps.

[Mudgee hunter]

They are good prices for both units.
Tip...
If you have 12v accessories like a decent air pump say fitted with alligator clamps.
Cut the alligator clamps off about 300mm.
Fit a pair of Anderson plugs to each end. Then you have an adapter to easily run off your auxiliary battery, or leave connected etc.
Even off your main cranking battery, fit a fused Anderson plug. Lot less chance of wrong connecting etc.
Even one to your exterior/ bull bar ...
Top up easily with a solar panel, or hook your air pump up to, etc.
Deck all your 12v stuff via Anderson plugs.
Even put an Anderson plug on a decent cigarette socket. Lead.

[Cannabat]

Don't use a battery isolator if you are going to use a lithium (LiFePO4) battery.

Battery isolators do not moderate the current or voltage going to the battery. Lithium batteries can and will accept a very high current. This can fry your cabling (you should have fuses or breakers and so it will trip them before frying your cabling I hope!), and also your alternator!

Use a DC-DC charger if you will use a lithium battery. Renogy makes a foolproof and very affordable one. 20A version is $130: https://au.renogy.com/renogy-12v-dc-...ttery-charger/

It's a fraction of the price of most other brands. Renogy has good products but sometimes their customer support is lacking. However you get an Australian warranty on their stuff. I don't see much point in paying significantly more for redarc, enerdrive, or projecta.

[Deezelweazel]

Sorry Mate, you obviously have no idea what you're talkin' about.

A battery isolator(hence the name) operates with diodes being capable to handle way more current than your DC-DC charger. Common versions on the market handle around 80A to 200A.
Your DC to DC unit can handle only miserable 20A...

Lithium batteries do have their built-in battery management. So why moderating the current? Actually this is limiting the capabilities. So limiting the current with 20 amps from the DC/DC Unit or "moderating" makes no sense at all.

Any loss of voltage will be compensated since our Jeeps still work with external voltage regulators. So if you need some fancy DC/DC units something in your electrical system isn't up to speed anyway.

[layback40]

Originally Posted by Deezelweazel

Sorry Mate, you obviously have no idea what you're talkin' about.

A battery isolator(hence the name) operates with diodes being capable to handle way more current than your DC-DC charger. Common versions on the market handle around 80A to 200A.
Your DC to DC unit can handle only miserable 20A...

Lithium batteries do have their built-in battery management. So why moderating the current? Actually this is limiting the capabilities. So limiting the current with 20 amps from the DC/DC Unit or "moderating" makes no sense at all.

Any loss of voltage will be compensated since our Jeeps still work with external voltage regulators. So if you need some fancy DC/DC units something in your electrical system isn't up to speed anyway.

Hey DW!!
I thought you must have left the room.
Good to see you are still about.
Hope you are staying safe!
For everyine else, DW has been about a while & knows his stuff.
LB

[2bad4u]

Originally Posted by Deezelweazel

Sorry Mate, you obviously have no idea what you're talkin' about.

A battery isolator(hence the name) operates with diodes being capable to handle way more current than your DC-DC charger. Common versions on the market handle around 80A to 200A.
Your DC to DC unit can handle only miserable 20A...

Lithium batteries do have their built-in battery management. So why moderating the current? Actually this is limiting the capabilities. So limiting the current with 20 amps from the DC/DC Unit or "moderating" makes no sense at all.

Any loss of voltage will be compensated since our Jeeps still work with external voltage regulators. So if you need some fancy DC/DC units something in your electrical system isn't up to speed anyway.

That's all well and good for the Lithium battery, but what Cannabat is referring to is the alternator being fried. Hooking up a Lithium battery to an alternator without some form of regulator can cause the alternator to fail. The BMS in the battery will do nothing to protect the alternator. If your going to tell someone they don't know what they are talking about, then perhaps you should have all your facts correct too..

https://www.victronenergy.com/blog/2...rging-lithium/