Solar trickle charge for car battery?

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Pavalijo

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We are setting off on an extended cruise from April (this year 4 months, in future could be up to 6). I am concerned that I do not want to run the batteries flat on the cars. One has a rather expensive gel battery.

I think I read, many years ago, advice to leave a small solar panel plugged into a 12v socket - any thoughts/advice? Do I need some form of regulator, or if the panel is small and correctly sized can I just plug in and forget?

Many thanks, Paul
 
We put a small charger on my wife's Polo last summer for three months. Providing it is small enough, you don't need to regulate it. Ours cost about about £15 in Halfords, though we had to get an adaptor for the car's diagnostic socket. Some modern cars can't be charged via the cigarette lighter socket when the ignition is switched off.
 
Disconnect the batteries. If they are good they will easily hold enough charge for at least 3 to 4 months. If left connected it will be the radio memory and security system that causes a gradual loss. When reconnecting the batteries you may have to re-code the radio if code protected. That is what I do with my car.
 
Unfortunately the battery on my car has to be coded to the car at a cost of £70 by BMW (only main dealers can do it, apparently). Plus I want the alarm to be active.

Hopefully Halfords can advise what wattage I need.
 
Up to about 5W are OK unregulated, any higher needs to be regulated. Do you have a 12v permanently live socket in the car? If not need to connect directly to battery terminals. 5W is unlikely to unlikely to keep battery topped up for 4-6 months.
 
I bought an AA one from Amazon a few weeks ago; recommended by forumite Sailorman. It cost around £23, I think. Seems to have solved the problem of a little used Skoda's battery going flat if the car was left unused for a couple of weeks.
 
I had a similar problem as the electronics for alarm, keyless entry etc. discharge the battery pretty quickly. I checked and all 3 12V outlets switch off after a short time and aren't suited to charging from a panel. Don't just assume that if a 12V socket provides power with ignition off that it will remain connected. Try plugging in something like a phone charger with an LED and leave it in a locked car for a while. You should be able to see the LED without unlocking the car and confirm it is getting power.

My next thought was to run a dedicated cable from the battery to an connector under the dashboard. However, my car is well sealed at the bulkhead and I couldn't find any easy way of running the wire without dismantling the dashboard and drilling a hole.

I finally ran a fused cable directly from the battery to a point behind the front grille. This was simple and allowed me to plug in my battery charger and leave that on a timer. That has worked well for past 3 years. The connector is sheltered from rain, coated with Contralube and disconnects if I forget to do it before reversing 2-3m.
 
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Many thanks for the advice. I have a charger with LED and will use it to check whether the 12v outlets stay live when ignition is off. I had a new battery on the BMW a year ago and with the coding cost it was over £300, so I want to keep that in good order at least.
That battery is in the boot of an estate so accessing that should be easy enough. Getting a cable to the battery in the Berlingo - might not be so easy!
 
Stork_III said:
Up to about 5W are OK unregulated, any higher needs to be regulated. Do you have a 12v permanently live socket in the car? If not need to connect directly to battery terminals. 5W is unlikely to unlikely to keep battery topped up for 4-6 months.
Click to expand...
Swmbo`s car is direct into the EOBD socket
http://shop.theaa.com/store/home/car-battery-solar-charger

 
I had a VW solar panel hooked into the cigar lighter on an old Porsche. The insurer would not tolerate the car without an active alarm... it was a 911 (993) RS :-) I see their point now!
 
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Mistroma said:
Good point, OBD is usually hidden away and I'd forgotten that the spec included 12V. I might just have connected a panel via OBD if I'd remembered. Filed for possible use in future
Click to expand...
The AA unit has a plug n socket in the lead, swmbo just pulls it apart,stows the panel on the sole out of the way & refits the panel with the suckers on to the screen & plugs the lead together. she parks the car facing south in the drive
 
I would go for a fused 10w panel connected directly to the battery terminals, left on the roof of the garage and angled to the south. 5w is probably ok also.
Have a look on ebay for Chinese panels cheap and oK by me. good luck olewill
 
sailorman said:
The AA unit has a plug n socket in the lead, swmbo just pulls it apart,stows the panel on the sole out of the way & refits the panel with the suckers on to the screen & plugs the lead together. she parks the car facing south in the drive
Click to expand...

I can't do that with the Skoda because the OBD socket is behind a pull down box (for coins etc) and when the OBD plug is in the box can't be closed and it's in the way of your leg.
 
As it happens I use one to trickle charge my 110 starter battery on my boat.It happily ticks over summer and winter so no problem on a car.
 
Visit your local caravan shop they will know the answer.

I usually remove the battery, fully charge it and put it somewhere warm. Added advantage is the car can't be hot wired.
 
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