150lt Fridge Run Time on 12 volt 100AH battery...

[ROnEM]

Hi,

Was wondering what sort of "run-time" you would expect to get from the 150lt fridge when it is running 12v from a secondary 100AH battery in the car when the engine is not running, perhaps because we have stopped for a cafe lunch or off doing a little shopping. This is assuming everything has been in the fridge and is at a normal cooled/frozen temperature, so the fridge is maintaining temperature only.

The van will be connected via Anderson plug to the car, and the 2nd battery will be isolated from the car's main cranking battery.

I don't want to always have to jump out and make sure the Anderson plug is disconnected every time we stop.

Cheers,

Ro

 

[Big Gee]

Hi Ro,

I have never timed how long ours runs for but I know the 150ltr fridge draws 35 amps. This would flatten a 100ah battery very quickly. you could put a universal start solenoid for about $30 from Ashdown Ingrams in the line down to your anderson plug.

These are switched via ignition so that means power to the fridge would turn off when the engine is not running.

What you most need to be cautious of, is if you flatten your battery whilst at the shops & near your camp & if you run a car fridge which also stores your beer.............. the risk is that the next day the dual battery in your car might be flat and your beer might be hot :sorry:

 

[Burnsy]

That would be a total disaster!

 

[ROnEM]

Big Gee,

Have to agree with Burnsy. It would be devastating - having to drink warm beer while contemplating what to do with two flat batteries! :frusty:

Would absolutely be putting a battery isolator/start solenoid into the Anderson line.

Cheers,

Ro

 

[Bank of Dad]

I run a 12 pin instead of a Anderson Plug, and have 2 relays to isolate the 150 ltr fridge and the van battery from the car when we stop.

Would'nt take long to flatten and quick 10 minute stops have a habit of taking 30 minutes before you realise!

 

[relgate]

I run a 12 pin instead of a Anderson Plug, and have 2 relays to isolate the 150 ltr fridge and the van battery from the car when we stop.

Would'nt take long to flatten and quick 10 minute stops have a habit of taking 30 minutes before you realise!

my 17 will have a 12 pin when we pick it up in August. can you give any more info on the relays? Where/what to place? thanks.

 

[ElectricGuru]

Hi Ro,

I have never timed how long ours runs for but I know the 150ltr fridge draws 35 amps. This would flatten a 100ah battery very quickly. you could put a universal start solenoid for about $30 from Ashdown Ingrams in the line down to your anderson plug.

These are switched via ignition so that means power to the fridge would turn off when the engine is not running.

What you most need to be cautious of, is if you flatten your battery whilst at the shops & near your camp & if you run a car fridge which also stores your beer.............. the risk is that the next day the dual battery in your car might be flat and your beer might be hot :sorry:

Hey Big Gee

We have the 150ltr fridge and it only draws 15A when on 12 Vdc.


Totally agree about the cutout switches and the warm beer, nothing worse. :doh: We have one on the anderson plug circuit and I have an additional undervoltage cutout purely for the fridge circuit so if there is an issue, I still have some lights to setup with.


Hey ROnEM

This is a discharge curve of the battery I have in the van (94Ah Gel). With the fridge running down to when my cutout switch opens at 11Vdc is just under 4 hours. Mind you that with an older battery, the ability to hold up for that time is reduced per year especially if it has been discharged a few times. So a rough guess of 2.5 hours would be about right from a full charge.


Regards

Gil

 

[Big Gee]

Hey Big Gee

We have the 150ltr fridge and it only draws 15A when on 12 Vdc.
View attachment 7743

Totally agree about the cutout switches and the warm beer, nothing worse. :doh: We have one on the anderson plug circuit and I have an additional undervoltage cutout purely for the fridge circuit so if there is an issue, I still have some lights to setup with.


Hey ROnEM

This is a discharge curve of the battery I have in the van (94Ah Gel). With the fridge running down to when my cutout switch opens at 11Vdc is just under 4 hours. Mind you that with an older battery, the ability to hold up for that time is reduced per year especially if it has been discharged a few times. So a rough guess of 2.5 hours would be about right from a full charge.
View attachment 7742

Regards

Gil

I just put my clamp meter on it when I was wiring up the Prado.

 

[ElectricGuru]

my 17 will have a 12 pin when we pick it up in August. can you give any more info on the relays? Where/what to place? thanks.

Hey Relgate

For the 12 pin setup, the relays dont have to be major heavy duty units but they would need to handle about 30-40 amps.

We have this unit on the rig protected by a 50A fuse that supplies the anderson plug. The fuse and the relay are mounted in the engine bay away from the engine heat but as close to the battery as possible.
Redarc SBI series dual battery isolator

We have this on the fridge circuit as backup protection on the caravan battery
Baintech low voltage cut out 40amp

There are many options for dual battery or main/caravan battery combinations but the main thing is, protect the cranking battery at all costs!

Cheers

Gil

 

[expanda]

There is a guide here , may help!

http://www.expandasdownunder.com/sh...-Hotwire-12-Volt-Hotwire-DIY?highlight=wiring

 

[ElectricGuru]

I just put my clamp meter on it when I was wiring up the Prado.

Wow, that is scary.

Thanks for the info. Might be indicating an issue with the fridge. (Not the beer!!!)

Also, what's the volts when it is running?

 

[Big Gee]

Hey ElectriGuru,

Im not sure about the volts, I just checked with the clamp meter as Jayco told me they were hard on the power...... I will check next time its hooked up and running.

 

[Ch00ka77]

Great comments I have installed the red-arc isolator for the exact reason if you stop for lunch there is no need to worry about flattening your start battery as prior to this I was disconnecting the Anderson plug when we stopped for what ever reason. I have recently added a second battery in the tow vehicle and was wondering through Super Cheap and found an identical Battery isolator the same as red-arc but this came with all the wiring & joiners needed and was only 80bucks.

 

[Burnsy]

My red-arc isolator cost me $85 delivered off eBay and came with two marine grade battery terminals, half the price of other retailers and didn't need to drive anywhere....gotta be happy with that!

 

[Big Gee]

Hey Big Gee

We have the 150ltr fridge and it only draws 15A when on 12 Vdc.
View attachment 7743

Totally agree about the cutout switches and the warm beer, nothing worse. :doh: We have one on the anderson plug circuit and I have an additional undervoltage cutout purely for the fridge circuit so if there is an issue, I still have some lights to setup with.


Hey ROnEM

This is a discharge curve of the battery I have in the van (94Ah Gel). With the fridge running down to when my cutout switch opens at 11Vdc is just under 4 hours. Mind you that with an older battery, the ability to hold up for that time is reduced per year especially if it has been discharged a few times. So a rough guess of 2.5 hours would be about right from a full charge.
View attachment 7742

Regards

Gil

Hey ElectricGuru,

I had the Ranger hooked up to the van tonight, 16 amps with the clamp meter at the rear of the fridge & 12.1 volts.

When i checked at the wiring off the battery in the car 13.2 volts & 17 amps.......

Two issues I can see, 1 I have a massive voltage drop that will need tending to & number 2 is perhaps I had about 6000 too many stubbles on the day I thought I measured 30 amps.

Sorry to everyone for mis information there :doh:

 

[Izzya123]

Hi ROnEM,

I'm no expert here, so I just had mine wired up by a local Auto Electrician....Adept Mobile Auto Elect in Mount Martha Vic - great job.

I've got a Ford Territory and the 12 pin plug was not wired for 12v, so the van when plugged in had no 12 volt from the car. So....

This is what I had done:
Auto elect rang Jayco to get approval to re-wire a few things....apparently Jayco wire larger items to the smaller pins which can burn out?? So he swapped them to the larger pins.
Added an isolator to the main battery so the car battery can never go flat.....engine goes off, nothing from the van can draw on it....good one.
Added an anderson plug from van to car for the van fridge to run off.
Added a second 100amp AGM battery to rear of car, in a battery box & wired in another anderson plug inside the car to run this aux battery from.
Added & wired in a plug for my 50 ltr waeco to plug into inside the car.
And re-wired the van fridge connection to draw from the second battery inside my car, not the car battery.
So now when I stop my car, instead of the van fridge being isolated from the car battery, it will continue to draw off my aux battery.

Now, my auto elect has told me I should get 5 - 6 hours from the 100amp aux battery supplying the van 150ltr fridge.

He said if I'm going to stay away from the car for a longer period with no power, then to turn the fridge from DC to off.

Both my Waeco & van fridge will be using the 100amp aux battery. So my car battery will always remain isolated.

He also gave me this small compact but expensive charger...plug in & forget type. It's great. Once at a powered site, just plug the battery in & it rapidly recharges.

All good, very happy. Given it all a test run and everything works great.

Izzy

PS: I can add some photos if you want them?? (When it stops raining)

 

[ROnEM]

Izzy - Sounds like a good set-up.

It's great to get an auto elec who knows what you are trying to achieve and does the job right first time.

Ro

 

[ah197331]

Hi Izzy,

I do exactly the same thing. I ran 13.5 mm2 wire up to the battery box in the boot which gives the battery a better chance of re-charging than if it were in the van (another 4 - 5 metres of voltage drop away). Also, if you're free camping for extended periods, by having the 'van' battery in the boot of the car, it gets a recharge if you go for a drive without the van. If you were in desparate need of a battery recharge, you can also just start the engine and let it idle for an hour or so. Much quiter than a gennie, if you don't have solar.

Andrew

 

[ElectricGuru]

I had the Ranger hooked up to the van tonight, 16 amps with the clamp meter at the rear of the fridge & 12.1 volts.

When i checked at the wiring off the battery in the car 13.2 volts & 17 amps.......

Two issues I can see, 1 I have a massive voltage drop that will need tending to & number 2 is perhaps I had about 6000 too many stubbles on the day I thought I measured 30 amps.

Hey Big Gee

No problems, I have similar experiences usually around the 4000 - 5000 beer mark too!!! :high5:

If the fridge is getting the 12 volts while running then that is ok. If it was lower than 12 V then it would be needing some work. Main thing is that the cable size and connectors are ok since at 16 amps, bad connections turn into really bad connections.

What is the cable size that you have running from car battery to the plug and from the plug to the fridge?

Cheers

Gil

 

[ElectricGuru]

Now, my auto elect has told me I should get 5 - 6 hours from the 100amp aux battery supplying the van 150ltr fridge.

Both my Waeco & van fridge will be using the 100amp aux battery. So my car battery will always remain isolated.

He also gave me this small compact but expensive charger...plug in & forget type. It's great. Once at a powered site, just plug the battery in & it rapidly recharges.

PS: I can add some photos if you want them??

Hey Izzy

Yes please, post some photos. Always good to see other's setups...

You may get the 5-6 hours on the aux battery but if you have both the fridge and the Waeco running of it, then that would be reduced down to about 2-3.

Can you let us know the make/model of the charger? Main reason I ask is that for battery charging, the golden rule from the people in the know is that you need at least 10% of the battery capacity in the charger output to really keep the battery fully charged, especially from more than average use. So if you have a 100 Ahr battery, get a charger with at least 10 A capacity to ensure that the full charge is delivered. The smaller ones are fine for maintenance charging, ie keeping the charge on them when lightly used or not in use.

Really good setup advice, great work!

Cheers

Gil