12V vs 24V

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Michael
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12V vs 24V

Postby Michael » Thu May 10, 2018 9:57 pm

Ok, so I'm only really asking this because my brain really isn't working at it's best at the moment (due to it being slightly overwhelmed by stresses), so I apologise for that. But..

My query is. In the Sprinter we have two 12v 120ah batteries in parallel providing a total 12v, 240ah. As I am trying to spec the truck leisure batteries I am most likely going to need two 12v batteries wired in series to produce the 24v.
My question is with the capacity. Does 240ah at 12v still stand at 24v? I guess this is a tough one to actually explain. But for some reason I was thinking that 24v may have only required half the battery capacity. I know I haven't mentioned appliance demand, but I'm just trying to work this out in my head and it's not making sense! :?

I guess to simplify the question. If we have similar appliances in the truck as the Sprinter, but 24v instead of 12v, will we still need 220ah?

Sorry, but thanks! :shock:

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bromleyxphil
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Re: 12V vs 24V

Postby bromleyxphil » Fri May 11, 2018 5:27 am

Hi Michael you will still have more or less the same capacity to run equipment. If you look at the spec on my 24v / 12v fridge it draws 3amps at 24v and 6.2 amps at 12v I assume the discrepancy is due to some kind of step down unit inside. I tried to source as much 24v kit as possible then have a small 12v circuit driven through one of these https://www.durite.co.uk/itm/55501/24A-Continuous-30A-Intermittent-Load/24V-to-12V-Voltage-Converter-Non-Isolated-24A/057824
I am sure someone will come along with a more technical explanation but that’s my understanding.

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Re: 12V vs 24V

Postby Ivan C » Fri May 11, 2018 6:43 am

Phil is right, double the volts means half the amps,
Ivan C

crinklystarfish
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Re: 12V vs 24V

Postby crinklystarfish » Fri May 11, 2018 7:08 am

Appliances that run from 24V require about half the current that the equivalent 12V appliance needs so capacity remains much the same.

The easiest way to think of it is to work out the Ah at the 12V rate. In other words, just add up the nominal Ah capacity of each 12V battery - doing it that way allows direct comparison across all dual-voltage trucks.

So - I have 95Ah on the 24V side (2 x 95Ah batts in series) and 100Ah on the 12V side.

Or 95Ah@24V + 100Ah@12V

Or 290Ah@12V

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NeilandPat
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Re: 12V vs 24V

Postby NeilandPat » Fri May 11, 2018 11:27 am

Michael.

Others have explained your answer perfectly.
Just to add to it , because the current is halved at 24v you only need half the wire size which can have advantages.

I think we all started hoping to do everything in 24v but soon realised that this is impractical so most of us have ended up with both 24 and 12 v circuits in our trucks. Using a step down converter.

Good luck

Neil

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Re: 12V vs 24V

Postby NeilandPat » Fri May 11, 2018 11:28 am

Michael.

Others have explained your answer perfectly.
Just to add to it , because the current is halved at 24v you only need half the wire size which can have advantages.

I think we all started hoping to do everything in 24v but soon realised that this is impractical so most of us have ended up with both 24 and 12 v circuits in our trucks. Using a step down converter.

Good luck

Neil
Last edited by NeilandPat on Tue May 15, 2018 2:05 am, edited 1 time in total.

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Michael
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Re: 12V vs 24V

Postby Michael » Mon May 14, 2018 10:28 pm

Thanks for the help again guys. I needed the reassurance as I realised that was the case with regards to half the current rating, but must have been having a very long brain fart moment :lol:

We're going to try and keep as much as possible 24v, but obviously there will be 12v exceptions.


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