UKC

Hi I was hoping someone may know if there are electric hobs which you can use off of a leisure battery? I have a 115amp leisure and will only be using it for charging phones and stuff so it won't be used too much.

In reply to samparsons:

Not that I know of. Electric hobs use a massive amount of power, would flatten a battery very quickly. Plus I doubt 12v versions exist so you would have to run a properly fat inverter

In reply to samparsons:

I know someone who has this to meet the needs of their vehicle being a camper van. The inverter powers a 2 plate hob.

It will heat for approx 15minutes. Enough to boil water a couple of times.

It is not used in anger this way, as it just isn't practical. Mains hookup or a gas stove...

In reply to Dave B:


Seems a bit odd. Surely a gas stove would be better?

In reply to samparsons:

I don't think it's practical. I only use electric kettle or slow cooker if there is an electric hook up on a campsite. Even then you need a low watt kettle or it trips on many sites.

In reply to samparsons:

No.

A cooker element is going to be about 3kW. At 12V, that's 250A. Not practical.

Then there's the energy capacity. A 115Ahr 12V battery is about 5MJ (115*12*3600). About enough to boil 15l of 20C water (5e6/(4.2*1000*80) at 100% efficiency). Actually, that's not too bad... Not that you'd get anywhere near the rated Ahr at 250A...

But a simple gas camping stove will manage 3kW, and butane, with an LHV of about 46MJ/kg, will have the same energy capacity with just 108g...

In reply to samparsons:

Chances are that if you try this you'll be able to fry eggs on the inverter needed to connect a hob. For about 15 minutes. (the capacity of your battery is only about 50% of the rated capacity when discharging at ~ 2 kw as per a hob).

I don't think your battery would last for very long if you abused it so, either.

What you need is to drop ~£4k on one of these... https://www.victronenergy.com/batteries/lithium-battery-24v-180ah

Or perhaps a gas hob and/or mains hookup...

In reply to captain paranoia:

Bit of a hijack here but I've built a cabin on wheels which I power using solar panels and leisure battery, though I'm clueless really as to electrical stuff. I'm interested in the calculations you use there as I'm finding that the battery I have in the hut doesn't last as long as I thought it should.

100W solar panel charges a 115Ah leisure battery via a charge controller. This then kicks out 12V to an 240V invertor which is connected to an RCB then into the circuit in the hut (twin sockets and a couple of 6W LED lamps). The charge controller will charge the battery up to ~14V and let it drop to ~10V to protect against it discharging to deeply. What calculations should I be doing to find the amount of time I can have the lights on for (and maybe charging a phone too)?

I understand there is google for stuff like this but when you know so little about it all it's nice to have it confirmed!

Thanks

In reply to samparsons:

The only reason I wanted to do it this way was to prevent a baked flame in my carpet covered van haha I'm not overly confident putting a gas hob in. I guess I will look for a little gas hob. Cheers

In reply to samparsons:

It's a bad idea. Your leisure battery isn't sized or designed to deliver the power required. Your starter battery would be better suited but still a poor choice. When you say 115A, I presume you mean 115AH.

It's doable witht he right parts which may or may not exist but that doesn't make it a good idea.
jk

In reply to Neil:

LEDs are 12v by nature from what I remember so you'll probably be using a couple of times more power than you need by using an inverter to go to 240v and then a second one back down to 12v.

Ditto if all you want is to charge a phone why not go straight from 12v to (from memory) 5v rather than adding in a conversion to 240v along the way?

In reply to Neil:

Look up Peukert effect. Leisure battery ratings assume about 0.1C discarge rate, if you draw more than that the capacity diminishes. Your solar panels (unless of course you have them metered and you're counting charge in) probably aren't delivering anything like the power on their rating plate for a variety of reasons.


2x6W =12W, at nominally 12V they therefore draw 1A (from P=IV)
Your 115AH battery can deliver 115A for 1H (except it can't, Peukert again)
Or: 1A for 115H

Your inverter is probably 95% efficient (I'm assuming they're 'mains' LEDs
Your LED power supply is probably 95% efficient
Your battery shouldn't routinely deliver more than say 70% of capacity to preserve its performance

From this we get 115H x 0.95 x 0.95* 0.70 = 72H of lighting between charges

Your phone assuming it's HUGE very roughly has a 3V, 4AH battery in it, assuming 100% conversion efficiency it will use 4 x (3/12) = 1AH of your leisure battery's capacity. Even at a pessimistic end to end conversion efficiency of 50% it uses essentially nothing.

HTH,
jk

In reply to samparsons:


We got a campingaz twin burner and built it into a unit. The flame is 300mm ish away (horizontally) from carpet etc and I've never had any concerns.

In reply to DaveHK:

Not really, because then you need to install vents etc in the bodywork. It's a camper in name, not in practicality.

In reply to Dave B:

The only vent you will need is a drop out vent for the gas bottle cupboard/locker in case of leakage.

Just buy a Smev 2 ring hob and have done with it, get it installed by a gas competent person and it wont be a concern

In reply to samparsons:

you need a small generator. Rather noisy and smelly compared with the simplicity of gas

In reply to Dave B:

Maybe we're talking at cross purposes but vents for a gas cooker are not a requirement for getting a self conversion classified as a camper.

In reply to DaveHK:

Maybe.

It was not the advice that I had heard, but its not my van, so I'm not really up with the regs.

It was, however, the justification for the 'not very effective' electric system. In summary on that part, don't do it if you want to actually use it.

As stated above any kind of electrical heating element consumes vast amounts of power. Electric hobs are also shit to cook on! Induction is better in terms of power consumption through increased efficiency but still drains more than a single 115ah battery will handle. I know people with 2kw+ panel arrays and massive battery banks (not in a van) who still shy away from any electrical heating device.

No vents are technically needed for gas except a drop vent below your bottle. However having a window/roof vent/extractor is pretty essential first so you don't die from carbon monoxide (a detector should also be fitted) and second so all the steam from cooking and gas burning doesn't turn your van into a moisture filled swamp.
I get by with a roof vent that is almost always open, cooking or not, and by opening a window as well whilst boiling pasta etc to create a through flow of air. After living full time with this system for 9 months I would fit an extractor fan if doing it again I think.

To protect a carpeted van look at one of the folding camping hobs. They have good ventilation underneath and a built in splashback.
They are also mainly underpowered and shit to cook on (but I am used to professional gas hobs at work) so I swapped mine out for a fixed unit. The smev ones look nice but insanely expensive. I got a two burner "domino" hob for £65 from ship it aplliances. The mains piezo ignition doesn't work (although could be rewired for 12v) but otherwise is great. My van is wood clad so I'm less worried about melting stuff but the hob really doesn't heat up the area around it too much.

If in doubt either get a proper gas engineer to help fit it all or do some interweb browsing! I don't want to encourage reckless behavior but I knew nothing about gas plumbing before I built my van and am now confident with copper compression fittings, isolation valves etc and probably saved myself a good bit of cash. Like many things it is mainly common sense.

In reply to samparsons:

I think I might go gas haha