Solar charged second battery
 

Hi,

We are going though Africa in a Land Rover shortly, and are trying to set up a cheap, effective separate battery system to run various bits and pieces. Current thinking is per the attached wiring diagram (apols for it’s amateur, unconventional nature – complete beginners, clueless about electrics).

THE THEORY:

· A solar trickle charger permanently connected to the leisure battery keeps it continuously topped up (we will be in the sun continuously).
· A cigarette lighter socket is connect to the battery with crocodile clips, with a 30 amp inline fuse on the positive wire.
· A multiple socket lighter adapter for the cigarette lighter socket allow us to hook up various bits and pieces – in particular an inverter for running a laptop, and an electric coolerbox to provide a cold beer at the end of each day’s driving.
· Made from CHEAP components, and kept VERY basic.

QUESTIONS:
· Will this work / are there any glaring flaws / minor adjustments that would make it work?
· Is the size of the Solar Trickle Charger sufficient to keep this running pretty much ad infinitum?
· What type/thickness should the wire from the battery to the Cigarette Lighter Socket be?

Would appreciate any insight you could provide.

Many thanks
Brett

I had a similar plan - I was running an Engel fridge so bought one of those 18 x 6 inch approx solar trickle charge panels to keep the battery topped up when stationary for a day or two in Morocco. It didn't seem to make any significant difference - still had a flat battery.

That was my experience !

Andrew.

With a 1 W charger it will take more then 900 hours to recharge the battery (from empty).

It’s not wise to run 30 A through a cig light socket. 30 A is 50% more then the stove in my kitchen….

The 'glaring flaw' is that you'll be taking out of the battery a hell of a lot more than you'll be putting back in. It depends on the figures of what you are using.
The trickle chargers are more practical for keeping a battery charged up over a time, when you leave the vehicle or such like, rather than for keeping one charged up that you are using constantly.

think more of 100watts of solar panel to do what you need

the little panels are just that, trickle charge, think of filling a bucket with a thimble

i use a 100w panel that keeps my battery topped up even when running a 74 litre fridge,

i know that doesn't fit your cheap criteria but it will work

I have a 90W panel and a 60l Fridge. In theory I need 6 hours of sunlight per day to put into the battery what the fridge takes out in 24 hours.

I'd be very interested to see how you guys travel with your big solar panels. I have not made that plan yet....

Ok thanks guys. I've had some really good advice; looks like:

• it's back to the drawing board
• there is no cheap way to do this

Will probably look into a proper voltage sensitive dual battery set up as a result - expect more questions as this stuff is pretty confusing one so mechanicially disinclined. Part of the point tho I guess.

Thanks again
Brett

permanently fitted to the roof of the vehicle for mine

And mine too!

..bit late on this one, but one thing that will work 'on the cheap' is a smartcom split charge device - they sell them at Towsure for about £12.
Once the main battery has reached a certain voltage it will start charging your leisure battery and will top it up at a decent rate. This is ok for something like a Morocco trip where you tend to be driving loads anyway.

Leccy coolboxes draw quite a lot of power, so turn off when you can, especially over night.
Rather than using one of those multi adaptors from a ciggy lighter, which are awful things, it is pretty straightforward and cheap to buy a small 4 way fusebox from somewhere like autosparks or maplins, wire in a good connection to the battery (30A wire) and then you have individual fused connections to each bit of kit with the correct fuse rating. Saves you getting warm beer when your invertor has just popped the fuse on your cigarette lighter for the fourth time and you only took 3 fuses...

fridge/solar panel
 

I have an 80W panel, mounted on roof at 45 deg to act like wind deflector. The panel is rated at 4.5A peak. My bro and me both went for same set up with solar panel controller (£50, ebay) The controller is essential as cuts off charging, shows current draw and charge rates.) Panel was about £250. This setup worked fine until we were stationary for more than, say 3 days, the battery was losing power. However, in its defence, we were in the shade quite a bit (in spain). When we trekked to Morocco, the results were outstanding. The engel fridge worked flawlessly, the charge rate was never less than 3-4A. It was 55 deg cel in Erg Chebbi region and we still enjoyed ice cold corona, had frozen meat still etc. Heaven. If you are going to be stationary for more than few days think either bigger panel or more batteries! I have red and yellow Optima.

the other benefit of having a panel is that if the worse comes to the worse and your main battery drains for some reason in the middle of nowhere you have a method of recharging it.

while a solar panel will provide adequate charge for lighting on it's own, as above, it won't be adequate for powering bigger items. to calculate what you have and what you need look at the current draw in amp hours of the equipment you will be using. then look at the AH of your proposed leisure battery and see if it will maintain those items for as long as you are likely to need them (say overnight for a fridge) you then need to consider the output of your panels during both optimum and shade conditions and see if that will provide adequate charge. If necesary, if you have space and weight available you may need to connect two batteries to give the Ah you need.

You will also need a charge controler or you will potentially fry your battery, although you may be ok on a small set up.

Personally I would go for a split charge system for when the vehicle is running (as described above) with a facility to plug a solar panel into the fag lighter (or simlar suitable connection) when you are parked up to top up. make sure though that the wiring is man enough for the job (i.e can handle the output of the accessories and the leccie produced by the panels).

my expertise is on solar systems in buildings, not vehicles, but this is a complex business. there are a number of good books on the subject though. I would recommend 'solar electricity handbook' by michael boxwell.
maplins, amongst others do suitable kits.

on the subject of fuses. the idea is not to fit a fuse so big it won't blow, it's to fit a fuse that will blow before your wiring melts! make sure the fuse is suitable (i.e. rated lower) than the capacity of your wiring, otherwise you'll have an impromtu barbeque on your hands.

the fuse doesn't help in the event of a short in the panel or it's wiring as the fault current is only marginally higher than the DC operating current. it's there in the event of overload or fault in your accessories. we don't even fit fuses on the dc side of domestic systems generating kW of power. they are only fitted on the AC side to protect the wiring from the demand side.

do check the output of what you buy. if you get a panel for charging a mobile you will have died of old age by the time it charges your battery!!
hope that helps
Andy
Sparking Moggy Solar
Dorset Solar Photovoltaic Energy UK | Dorset Solar Power