Auto Electrician advice

[iowlee]

Guys I am just finishing converting a 7.5t daf 45 into a transporter/motorhome. It was an ex council mobile office so had 4 very large 12v batteries linked in parallel and in sequence (I think that is what it is called), in it to supply mobile 24v and 240v power via an inverter.

 

 

 

 

 

Looking through old docs it would seem they upgraded from a honda generator as a power source. Aparently they spent over £3K converting the power source!!

My issue is it had been sat for several months minimum, with no use so I have found it doesn't hold 24v charge very well. I have taken them out and charged them individually, 1 holds a constant 13+v after a week, 1 drops to just under 12v, 1 under 9v after about 24hrs, the other will not charge at all (literally 0.00V !!) So my thoughts are 2 dead 2ok. The local supplier wants £270 each battery!! I know I can get them slightly cheaper on the bay of E, however living on an island couriers are funny about bringing batteries over on the ferries.

I have a feeling they may be overkill for what I am going to need, but  want to check with a grown up.

Inside the van I have

 

Would  it be ok only running 2 rather than 4 batteries?

What sort of usage could i get out of them?

Inside the van i have a microwave/double hob/kettle/toaster that would need to draw 240V power from them through the evening. A 24v winch for getting the car in the garage area. I have a small generator that would be able to supply sufficient power during the day.

I am assuming that I will not be able to draw power from a lot of the circuits I visit.

 

I hope this makes sense. and someone can offer some assistance. My only other camper that i have owned with leisure batteries in it also had gas for cooking/heating water so batteries only had very little use.

Lee

[John (Kernow)]

Only 2 batteries running an inverter with those high current appliances are not going to last long. It also seems like it doesn't charge from the vehicle when running so I think a mains hook up at the circuits would be necessary especially for a weekend. Reading the instructions it would appear that it needed charging daily from the mains even with 4 batteries.

The best way is to connect the two good batteries that you have and give it a go at least then you will have a good idea what you can run and for how long before going on your first trip or buying new batteries.

Hope this is of some help. John 

[iowlee]

Thanks for the reply John, I did think about adding a split charge from the alternator as well.

Wasn't sure if there was a way to work out how long the batteries would last supplying 240v.

Suppose I will just give it a go and see how long it lasts. I take it the charger and inverter will be ok with just the 2 batteries, not really sure how they work regarding power supplies/draw etc.

Also considered solar power but never used it before.

[corsechris]

You can make a (very) rough estimate on what you might get out of just two battieries from the ratings. 240Ah x 2 @ 12V gives 5760Wh. Allowing for efficiencies and losses, I'd take a stab at best case 4kWh.

from your description, no problem running on just 2 batteries assuming you wire them in series. FWIW I never like to see batteries in parrallel, just feels wrong to me as they are never identical so one will always be propping the other one up to some extent. Same can be said for series as far as the current goes but a battery is just cells in series so you can't avoid that.

It's hard to argue with the energy density of petrol though. Depending on your intended use, might be cheaper to revert to a generator?

[Alan Cutler (Adge) - Dorset AO]

Might be worth considering converting your cooking facilities to gas, can sometimes find working cookers etc in old/scrap caravans. Have you got a fridge? If not they can be acquired from the same source, they are normally 3 way (240v/12v/gas).

Have had solar panels fitted on our last three motorhomes, good on long daylight days, bit more limited in winter. But wouldn't be without them now.

Quick "fix" may be a decent generator, beware of noise levels if you're looking at some of the cheaper versions. Not to say there aren't some reasonably priced generators out there!

[Alan Cutler (Adge) - Dorset AO]

Forgot to say always had 2x100Ah batteries in our motorhome. Don't forget, the more battery capacity you have, will obviously last longer, but will also take longer to charge!

[iowlee]

6 hours ago, corsechris said:

You can make a (very) rough estimate on what you might get out of just two battieries from the ratings. 240Ah x 2 @ 12V gives 5760Wh. Allowing for efficiencies and losses, I'd take a stab at best case 4kWh.

from your description, no problem running on just 2 batteries assuming you wire them in series. FWIW I never like to see batteries in parrallel, just feels wrong to me as they are never identical so one will always be propping the other one up to some extent. Same can be said for series as far as the current goes but a battery is just cells in series so you can't avoid that.

It's hard to argue with the energy density of petrol though. Depending on your intended use, might be cheaper to revert to a generator?

Thanks for this Chris, the reason they are in parallel is purely to provide the 24v I'm guessing. I think for the moment I will try running with the generator during the day, relying on the batteries purely for the noise curfew hours when generators are not allowed.

Once again thanks for the info re wh's that should be produced.

 

Lee

[iowlee]

3 hours ago, AdgeC said:

Might be worth considering converting your cooking facilities to gas, can sometimes find working cookers etc in old/scrap caravans. Have you got a fridge? If not they can be acquired from the same source, they are normally 3 way (240v/12v/gas).

Have had solar panels fitted on our last three motorhomes, good on long daylight days, bit more limited in winter. But wouldn't be without them now.

Quick "fix" may be a decent generator, beware of noise levels if you're looking at some of the cheaper versions. Not to say there aren't some reasonably priced generators out there!

Thanks for the reply AdgeC, Wanted to stay away from complexities of fitting gas for the little I will be planning on using. However original plans when thinking of the conversion was to buy a caravan and strip it out to use all of the gas/water bits. Don't really know why but deviated from that idea somewhere along the lines.

I will give the solar some consideration.

Lee

[Alan Cutler (Adge) - Dorset AO]

You might well have found them, but CAK Tanks supply most things for motorhome converting, link below if it helps:

http://www.caktanks.com/CAK - Products.htm

You could just go really simple and use a freestanding camping cooker for a late night fry up!

I believe you could probably buy four new 100Ah leisure batteries for £270, need to work out what you anticipate using power wise when you aren't allowed to run your generator. Unless your doing a lot of cooking, just lights I guess or have you got electric heating as well?

[iowlee]

1 hour ago, AdgeC said:

You might well have found them, but CAK Tanks supply most things for motorhome converting, link below if it helps:

http://www.caktanks.com/CAK - Products.htm

You could just go really simple and use a freestanding camping cooker for a late night fry up!

I believe you could probably buy four new 100Ah leisure batteries for £270, need to work out what you anticipate using power wise when you aren't allowed to run your generator. Unless your doing a lot of cooking, just lights I guess or have you got electric heating as well?

Thanks for the link, hadn't seen them before.

I have a small electric 2 'ring' hob. I do have a back up option of an old gas camping cooker if desperate. I don't anticipate loads of use at night and will typically only be away in it for 1 or 2 nights at most.  I don't plan on cooking much as I tend to eat in the cafe/restaurant at the circuit or live off of junk snacks.

Regarding heating, the truck is well insulated and I hope to not really need heating, my current option that I have used this year is the back of my vivaro van with no real insulation to talk of and I didn't get cold. I do have a portable small camping gas heater if power does become an option but was only really thinking of this for heating the awning/gazebo. I had planned to use a small oil filled electric radiator to take the chill of if needed.

Lee

[corsechris]

20 hours ago, iowlee said:

Thanks for this Chris, the reason they are in parallel is purely to provide the 24v I'm guessing. I think for the moment I will try running with the generator during the day, relying on the batteries purely for the noise curfew hours when generators are not allowed.

Once again thanks for the info re wh's that should be produced.

 

Lee

Hi Lee,

Just to avoid confusion, having the 12V batteries in series (+ve to -ve) adds their voltage giving you the 24V (say 100Ah @ 24V), by having them wired in parallel (+ve to +ve and -ve to -ve) you add their capacity (say 200ah @ 12V). By doing both with 4 batteries, you get a 24V battery with double the capacity of one battery. 200Ah @ 24V. The inverter is 24V so as a minimum, you need two 12V batteries connected in series to get you that. If it worked out cheaper, you could get 4 smaller capacity batteries and repeat the series/parallel configuration. Just because I don't like connecting them in parallel doesn't mean it isn't standard practice  

A hybrid solution is a good plan I think - saves all that 'range anxiety'   The setup you have in the wagon looks like its pretty high-end so it would be a shame to just junk it. As always, it's the batteries that let these things down. Deep discharge batteries like those tend to be pricey and if you try using 'ordinary' car batteries they won't like it.