How long will my battery last?

[Mr Meenah]

Am I right in thinking Amps = watts ÷ volts
Therefore if I plug into my UK inverter I'll use 0.22amps per hour?
It's on a cool box. I'm a bit surprised it uses so little.

 

[DavidG58]

I looks to have a 12V input option, I would suggest using that, not going through a transformer

 

[chaser]

I looks to have a 12V input option, I would suggest using that, not going through a transformer

dont see why you would need to use an inverter at all, either 240 on hookup or 12 v if not

 

[Zigisla]

Unfortunately not so little. Although you are using 240V from the inverter, it is still drawing from the 12V battery therefore closer to 5 amps. Use the 12v option

Edit. Beaten to it as above

 

[scotjimland]

and used on 12v option it will be using 42watt / 12 = 3.5A

an 85 ah battery will be effectively flat (down to 50%) in about 12 hrs

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[pappajohn]

View attachment 242635
Am I right in thinking Amps = watts ÷ volts
Therefore if I plug into my UK inverter I'll use 0.22amps per hour?
It's on a cool box. I'm a bit surprised it uses so little.

Correct, but in this case the original supply voltage is 12v, not 230v, so you'll use 3.5 amps/hour plus inverter losses which may bump it up to 4.5 to 5 amps/hr.

But as already said, just use it on 12v.
No point inverting 12v to 230v only to convert it back to 12v via the cool box's inbuilt transformer.
The cool box working voltage is 12v regardless of input voltage.

 

[Mr Meenah]

Thanks guys. The reason I was thinking of using the inverter is that the inverter is in the back of the van whereas the 12v supply is in the cockpit where the lead will not reach from where's best to locate the cool-box. I could move the cool-box closer to the cockpit (not ideal) or get a plug-in 12v extension if there is such a thing.
Also to save draining the battery I could unplug the cool-box overnight. I suppose if I don't open it it will still keep stored items cool for a certain period of time..right?

 

[irnbru]

Probably best to get a 12v socket installed in the habitation area. It’s uses are endless.

 

[Langtoftlad]

or get a plug-in 12v extension if there is such a thing.

Yes there is...


...but my concern now is that it doesn't sound like you have a separate 'leisure' battery from the vehicle battery - I would be very wary of using your vehicle battery to power a cooler with the engine off.
- would the 12v socket on the dash even be live with the ignition off?

 

[Mr Meenah]

I have 2 12v sockets in my Sprinter of which 1 is always live. I installed a second battery under the passenger seat at the weekend using a T-max split charge system. It isn't a dedicated leisure-battery though just a spare a Bosch 88ah battery out of a Jag which I thought would be ok until funds permit the purchase of a deep-cycle gel battery.
So yes, a second battery is there and I would need a 12v cig-lighter extension that I can direct wire to said battery.

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[Geo]

If the invertor option was because of location of invertor to cool box why not pick up from the inverters
12v supply and fit a socket there

 

[DavidG58]

I have 2 12v sockets in my Sprinter of which 1 is always live. I installed a second battery under the passenger seat at the weekend using a T-max split charge system. It isn't a dedicated leisure-battery though just a spare a Bosch 88ah battery out of a Jag which I thought would be ok until funds permit the purchase of a deep-cycle gel battery.
So yes, a second battery is there and I would need a 12v cig-lighter extension that I can direct wire to said battery.

Be very careful, my base vehicle is a Merc and it took me three flat cab batteries / jump starts to learn that both of those sockets are wired to the cab battery

you are right that one is on ignition and one permanently live but both if over used will leave you needing a jump start

 

[Mr Meenah]

Be very careful, my base vehicle is a Merc and it took me three flat cab batteries / jump starts to learn that both of those sockets are wired to the cab battery

you are right that one is on ignition and one permanently live but both if over used will leave you needing a jump start

I realise this hence the second battery..

I've now bought this to extend into the 'cargo' part of the van. Can anyone tell me which of the terminals is positive?

 

[Mr Meenah]

I can't upload a photo atm so does anyone know what polarity the centre-pin and body of the female 12v socket have?

 

[Mr Meenah]

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[pappajohn]

I realise this hence the second battery..

I've now bought this to extend into the 'cargo' part of the van. Can anyone tell me which of the terminals is positive?

Oh dear ... Please get somebody with the knowledge to do the work.

 

[DBK]

I can't upload a photo atm so does anyone know what polarity the centre-pin and body of the female 12v socket have?

Centre should be positive. But if you are planning any electrical work you really need a multimeter and you can get a good one for about a tenner. You can then double check the polarity of the existing sockets.

We have a coolbox but it is a compressor one and uses less power than the type I think you have. To keep it running we need a reasonable amount of solar panels. We had 90W originally but that wasn't enough during a cloudy September in France so I added a second panel of 100W and this combination is generally enough.

My point is you won't be able to run a coolbox for very long unless you have reasonable solar power available.

Which you may well have of course.

 

[Mr Meenah]

Oh dear ... Please get somebody with the knowledge to do the work.

Thank you that's very helpful.