connected a second 12v battery to a vehicle

[seamonkey]

Heya,
Hope someone can help me here, it's not very bushcrafty but it does enable me to live an easier life:-)
I have a second 12v battery which i use in my van, I use this with an small inverter and croc clips to power a laptop,charge phones etc and as as backup should i find the primary flat.
Now at the moment i just charge this up when i have the chance and am near a ac socket, not ideal. What i would like to do is have this connected in parallel so it charges from the alternator and perhaps have a cut off/isolator switch also to prevent me draining the primary bat and waking up in the **** end of nowhere unable to start the vehicle

The primary battery is in the rear of the van under a panel so cabling should be pretty easy (89 toyota hiace super custom for those wondering)
I may also install a solar panel to keep things topped up - if anyone has any options on what's good/bad/ace?

any thoughts on how i can achieve this safely and reliably (cheap would be nice :-)

Thanks in advance folks

Graham

[Wayland]

I've been looking at this too but havn't really worked it out myself yet.

There seem to be some bits of kit available for charging caravan leisure batteries but I'm not up on how the electronics / electrics work.

I hope someone out there can help us both.

[weekend_warrior]

To do this properly (you could just wire in another battery, but that would not be advisable!) you realy need a dual battery isolator. A good one will ensure that both batteries charge, and also that me main chassis one doesn't get discharged by the auxilary equipment. Have a look at this web page and the pdf doc on it - it's a starting point.

Battery Isolator

I'm not associated, affilated with these people in anyway etc...

[seamonkey]

Hi,
Initially ,my thinking is that I can earth them both and simply connect the positive, perhaps with a cut off switch in between. i have some old booster cables i can butcher for this purpose, but i can't afford to make an expensive mistake.

Then again I also thought it would be a good idea to jugle knives when i was around 14.
:-)

[wingstoo]

Hi Guys,


You need a split charger from a caravan shop...

http://www.nationalluna.com/battery.html

http://www.automotive-electrical.co....rgesystems.htm

http://www.antares.co.uk/glossary/split_charging.htm

http://www.landroverweb.com/Splitcha...ge-relay-1.htm

That should give you a few pointers.

LS

[weekend_warrior]

Hi,
Initially ,my thinking is that I can earth them both and simply connect the positive, perhaps with a cut off switch in between. i have some old booster cables i can butcher for this purpose, but i can't afford to make an expensive mistake.

Then again I also thought it would be a good idea to jugle knives when i was around 14.
:-)

I seriously wouldn't do this! Lead Acid batteries require some respect and you need to properly isolate them and still be able to charge and use them. You will need a dual battery isolator of one kind or another.

[anthonyyy]

I used to have a VW camper that had a second battery as you described. I'll see if I can find a wiring diagram somewhere. The second battery never gets charged up high enough that you can start your van on it though.

A simpler alternative is to simply get one of those 12 battery packs that you plug into your cigar lighter socket. These have the advantage that you can easily take them out and charge them up in the house before you take a trip or to start a car; and you can use them in camp.
You can fit a "cigar lighter" socket directly to your battery if it is more convenient, I would put in an inline switch and perhaps fuse.

[seamonkey]

Appreciate the help chaps, good jokers the lot of ya.
does this
solar charger look like a useful bit of kit or just a useless toy?

just having a look through those links at the moment i'm glad i asked

cheers


G

[swyn]

A good yacht chandler will have the correct switches for batterys. I have a good supplier of electrical bits and will PM the addy to you. Right at the minute I am a little fuzzy as the children are arguing and shouting!
With solar charging remember to fit a blocking diode in the +ve side, this will stop discharge during the hours of darkness.
Swyn.

[Glen]

Appreciate the help chaps, good jokers the lot of ya.
does this
solar charger look like a useful bit of kit or just a useless toy?

just having a look through those links at the moment i'm glad i asked

cheers


G

At 1.5W peak ( that's in best conditions ) it's really not going to make much difference as far as charging your setup is concerned. I think of these as just enough to stop things like a vehicle clock and alarm running the battery down over a matter of weeks. My opinion is there worth collecting form if you come across them for virtually free and wiring several together or there worth having if your going to park up and leave your vehicle unused for a month or so and are worried about the bettery going flat while not in use.

If your leaving the panel in a stationary position ( ie not moving it to track the sun ) I think you'll only average out about a third of the peak power rating during the hours it's in sunshine. so 0.5W average over over 12 hours is only going to give around 0.5Amps. Your car battery is probably aroud 50-60Amps so that's a 1% charge rate per day ( for the single battery )


A good cheap souce of split chargers ( If memory serves VW use a Zigg unit, which are well regarded ) is breakers yards. For new I'd look at yaching suppliers online, look at a few as some are very expensive ( catering to people who can afford big yatchs I guess ) and some pretty reasonable.

[Rebel]

My Transit van has two batteries in the engine compartment. They both charge from the alternator when the engine is running.

This is a fairly common set up in vans and you'd just need some information on the wiring. Once you've identified the parts you need you could get them from a breakers yard and install them.

The solar panel you are looking at is too small to be of much use. You need a big expensive one. This smaller one is okay for topping up a charge on slightly run down battery, they do work because I tried it. I left it plugged in for three days on an old diesel van that wouldn't start because the battery was low and after the three days were up I managed to turn the engine over and get it going.

[spamel]

I have a landrover mag somewhere with a tutorial on setting up a split charge system. I could dig it out and scan it for you if you like. Obviously, the bits like resiting the aircleaner to fit the second battery in may not apply to you, but the fundamental basics are there. I think it has info on where to get the bits from aswell.

I'll dig it out. Give me a PM with an email address if you want it.

[Gibbsy]

Have a look on this thread from another forum it may be of help.

http://www.hiluxsurf.co.uk/forums/sh...t=dual+battery

[Minotaur]

My Transit van has two batteries in the engine compartment. They both charge from the alternator when the engine is running.

Why would a standard transit have two batteries?

I know ambulances have it one does the normally stuff and one is for the kit in the back so if you see one in a breakers, might be worth checking.

[Buckshot]

I've put a second battery in my Landy.
I rigged it up with a split charger and I've had no problems at all with them.
I run the accessory stuff off the second.
If you go to a car parts shop or a caravan shop the split chargers you buy have a wiring diagram with them.
Just make sure you have heavy enough cable to take the charge.

Cheers

Mark

[FGYT]

Hi Guys,


You need a split charger from a caravan shop...

http://www.nationalluna.com/battery.html

http://www.automotive-electrical.co....rgesystems.htm

http://www.antares.co.uk/glossary/split_charging.htm

http://www.landroverweb.com/Splitcha...ge-relay-1.htm

That should give you a few pointers.

LS

Yep a split charger is the answer bout £15 from the caravan shop a few meters of wire job done in a hour or so depending on runs and how neat you wish to be
its basically a double relay that charges the second battry once you have started the engine and disconnects it if the engin isnt running other wize the lower charged battry ( normally the second one) will empty the higher charged one ( the one you want to start the car with )

ATb

Duncan

[Klenchblaize]

Yep a split charger is the answer bout £15 from the caravan shop a few meters of wire job done in a hour or so depending on runs and how neat you wish to be. Duncan

How long!!



Cheers

[twisted firestarter]

Hi Seamonkey
I would say that a solar panel is a great idea if you are planning on being parked up somewhere for more than a night or two, particularly off the beaten track. Try to get a crystaline panel. There are two types- monocrystaline and polycrystaline, mono pv's (photovoltaics) work better in ambient light and poly pv's are better in direct sun (so mono it is then if you are uk based!). I used panels made by Kyocera for all of my domestic electricity for 10 years and they rock . Try to get a panel with the biggest wattage output for your budget - I would say to try and budget around £200- £250, they are not exactly cheap. The upside is that they are generally guaranteed for 20 years so will be supplying you with electricity for the next 2 decades. I would suggest that you don't bother with anything less than about 30 watts unless you just want to charge your mobile phone, 80 watts would be almost overkill but it comes down to how much you will need the charge during the winter and what you are running. Another thing to bear in mind is that you will need a voltage regulator so that the battery doesn't boil in the summer (£25 ish for a basic one). About 7 years ago my girlfriend, kids and I took off to southern Europe in my Land Rover 110 to which I had fixed a 35 watt panel on the chunky roofrack. We spent nearly five months living in a big dome tent (not very bushcraft I know). I rigged up 12 volt sockets in the Landy and decent lenght of 10mm multistrand wire (home made wander lead) to lights, stereo, mobile, fan etc. in the tent. It enabled us to wild camp in real comfort without 240 hook-up or running the risk of draining the vehicle battery. The funniest incident was in southern Portugal when we decided to stay on a campsite for a couple of days to use the laundry and lord it up, the ground was so rock hard that there were no tents on site (nobody could get their pegs in) . We got the motorhome curtains twitching when I plugged in my adapted 12volt drill with a masonry bit and set it to 'hammer' setting - job done! Good luck and feel free to ask if I can help in any way.

[ja2495]

I have fitted split charge systems to all my land rovers (there has been several over the years!) and its easily done with a few pounds worth of realy and wire.

Have a look at this website it explains it all very well.

http://www.kampenwagen.co.uk/Split%20Charge.htm

Jon