Freelander 1 Aux Power for Cool Box

Mr K · May 9, 2023

Hi
I'm looking for a easy way to be able to power a small 8L 12v cool box when parked up.
A full split charge seems a bit over kill & solar is crazy expensive
I'm thinking about fitting a small battery, (maybe a motorbike battery) and connecting that up to a switched 12v supply in the boot (maybe tapping into the towbar elecs) via a diode so it charges when the car is running and then doesn't feed back when not running.
I know the std charge rate is approx. 14v for the car battery but it can charge a caravan battery via the twin elecs.
Would this work, any other suggestions?
Thanks.

Nodge68 · May 9, 2023

Mr K said:
Would this work, any other suggestions?

First off you need to know the current draw of the cool box. Most use a peltier heat pump, which will be rated at about 50 Watts, with another 5 Watts for the fan.

So you need a battery that is able to supply 55 Watt hours of energy for the time you need between charges.
Now a 100 AH car battery has about 550 Watt hours of energy storage before it needs charging, so this is about 11 hours of cooling before it's flat.

A motorbike battery will probably give you 2 maybe 3 hours before it's flat, so not much use.

The best way is with a lithium battery, but those are more expensive, but also have a much longer service life.

Mr K · May 9, 2023

Thanks
The manual states 46 watts and 3.8A.
There's not a lot of room in the back of FL1 hence why I'm looking at small battery.

Nodge68 · May 9, 2023

Mr K said:
Thanks
The manual states 46 watts and 3.8A.
There's not a lot of room in the back of FL1 hence why I'm looking at small battery.

So how long do you want to power it for?

marjon · May 9, 2023

Buy a dual cool box, cool while you drive then cool on gas when stationary.

might be more money but will save extra batteries and/or wiring.

J

Dbest43 · May 9, 2023

The cheapest way is fit a second battery and use that for your fridge connect + to + and - to - then both batteries stay as 12v both batteries charge when driving

Mr K · May 10, 2023

Nodge68 said:
So how long do you want to power it for?

A couple of hours will be fine.

Mr K · May 10, 2023

Dbest43 said:
The cheapest way is fit a second battery and use that for your fridge connect + to + and - to - then both batteries stay as 12v both batteries charge when driving

thanks but that would also drain both batteries when parked up.

Nodge68 · May 10, 2023

Mr K said:
A couple of hours will be fine.

It's easy to work out the battery size needed. Multiplying the AH of the box by the run time required, will give you the minimum capacity battery needed.
Add a solar panel of decent size and a charge controller, and you'll be able to charge the battery without running the engine.

I use a home made solar generator when camping. Its got more than enough power for tent lights, phone charging and running a cool box, all charged by solar panels.

Mr K · May 12, 2023

Nodge68 said:
It's easy to work out the battery size needed. Multiplying the AH of the box by the run time required, will give you the minimum capacity battery needed.
Add a solar panel of decent size and a charge controller, and you'll be able to charge the battery without running the engine.

I use a home made solar generator when camping. Its got more than enough power for tent lights, phone charging and running a cool box, all charged by solar panels.

thanks.
How do I find the AH of the box? the manual only states 46 watts and 3.8A.
Do I multiply 3.8 x 60 = 228AH? So I for 2 hours I wuld need a 456AH battery? (seems very high)
So a battery rated at 2Ah (25Wh) would be useless??

This website states I need a 3.83AH battery (I'm rubbish at elecs) so is the 3.8A that's stated in the manual the AH?

Battery Capacity Calculator

Battery capacity calculator converts between amp-hours and watt-hours.

www.omnicalculator.com

Dbest43 · May 12, 2023

Just put an on/off switch in-between batteries if you think your going to use that much power back in the day we had lots of vans with auxiliary batteries with this configuration

Nodge68 · May 12, 2023

Mr K said:
thanks.
How do I find the AH of the box? the manual only states 46 watts and 3.8A.
Do I multiply 3.8 x 60 = 228AH? So I for 2 hours I wuld need a 456AH battery? (seems very high)
So a battery rated at 2Ah (25Wh) would be useless??

This website states I need a 3.83AH battery (I'm rubbish at elecs) so is the 3.8A that's stated in the manual the AH?

Battery Capacity Calculator

Battery capacity calculator converts between amp-hours and watt-hours.

www.omnicalculator.com

If it's 3.8 A, then it'll use 3.8 AH of electricity. So a 38 AH battery will give you 10 hours of running.

A 2AH battery would give about 30 minutes run time.

Mr K · May 12, 2023

This should work, https://uk.rs-online.com/web/p/lead...KCIN22eEijw_iQV-x2xoCmMgQAvD_BwE&gclsrc=aw.ds

Nodge68 · May 12, 2023

Mr K said:
This should work, https://uk.rs-online.com/web/p/lead-acid-batteries/6142475?cm_mmc=UK-PPC-DS3A-_-google-_-DSA_UK_EN_Batteries+&+Chargers_Index-_-Lead+Acid+Batteries|+Products-_-DYNAMIC+SEARCH+ADS&matchtype=&dsa-1592138853539&cq_src=google_ads&cq_cmp=15904458410&cq_term=&cq_plac=&cq_net=g&cq_plt=gp&gclid=CjwKCAjwx_eiBhBGEiwA15gLN8IbiRKpwP1h5DrFBaV8x2G4Js32Xsen8o1KCIN22eEijw_iQV-x2xoCmMgQAvD_BwE&gclsrc=aw.ds

This would give a longer life, and comes with a charger.

Pardon our interruption...

Freelander 1 Aux Power for Cool Box

Mr K

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Nodge68

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Mr K

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Nodge68

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marjon

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Dbest43

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Mr K

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Mr K

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Nodge68

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Mr K

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Battery Capacity Calculator

Dbest43

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Nodge68

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Battery Capacity Calculator

Mr K

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Nodge68

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