Battery charging through tow electrics

I used to charge the battery on my Discovery 3 through the tow electrics with a CTEK 3600. It was very easy, no messing about and neat.

Can it be done on the P38 or is there good reasons not to??

There seems to be a split view on whether the battery should be disconnected prior to charging on the forum.

pulsed charging can upset electronics and your split charge relay will stop it charging on caravan socket.

optimate and weather proof connector or if cig lighters constant live-through that

I have a permanent live on my caravan socket which is European standard 13 pin, so charging through that would be possible, but it's easier to pop the bonnet and clip on.

Datatek said:

I have a permanent live on my caravan socket which is European standard 13 pin, so charging through that would be possible, but it's easier to pop the bonnet and clip on.

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Yes but you've stumbled on a good workable solution for 'locked out due to battery drain' where you can't get into the car to open the bonnet.

Anyone checked the ETM to see if the trailer socket is definitely permanaently live and not relayed through BECM like everything else?

SpudH said:

Yes but you've stumbled on a good workable solution for 'locked out due to battery drain' where you can't get into the car to open the bonnet.

Anyone checked the ETM to see if the trailer socket is definitely permanaently live and not relayed through BECM like everything else?

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When I fitted mine I did not find a permanent live although I used all the correct connections, I reckon LR would be scared of battery problems. I put my own in useing 4mm direct from the battery

This is what i did to make it up.

Simply make up a cable to connect the green (pin4) +ve and White (pin3) -ve to the battery charger.

On a CTEK - cut the black/orange connector cable and hook up with the pins mentioned. No other wires needed... So it would be: CTEK orange/black connector -> wires -> towing electrics plug (at green and white pins on the latter)






Pin Cable Colour 12N Connector Function 12S Connector Function *

1 Yellow Left Indicator Reverse Lamps
2 Blue Fog Lamps (if fitted) Spare
3 White Ground Ground for pin 4
4 Green Right Indicator Permanent 12V power / charge
5 Brown Right Side / Taillamp Spare
6 Red Brake Lamps Fridge
7 Black Left Side / Taillamp Ground for pin 6

That sounds like a winning idea as my P38 often sits on my drive through winter, I've already had to have the battery off and recharged and was crapping myself about it causing problems. I did ask on this forum about using a CTEK charger, but didn't get an ideal solution.

What did worry me was a specific reference in the RR manual recommending not to leave a charger attached for long periods, although I'm assuming that technology has moved on from 1990.

Hanoverian said:

That sounds like a winning idea as my P38 often sits on my drive through winter, I've already had to have the battery off and recharged and was crapping myself about it causing problems. I did ask on this forum about using a CTEK charger, but didn't get an ideal solution.

What did worry me was a specific reference in the RR manual recommending not to leave a charger attached for long periods, although I'm assuming that technology has moved on from 1990.

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A smart charger can be left on, a cheapo basic charger will cook the battery. If I have to leave mine I use a solar panel with a charge regulator

Datatek said:

A smart charger can be left on, a cheapo basic charger will cook the battery. If I have to leave mine I use a solar panel with a charge regulator

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Same here, I'm a big believer in solar chargers.

Goodfella, I think the answer to your query is in how Datatek wired his trailer socket, direct from the battery. I'm pretty sure its the only way as most hard wired things go through the BECM, even some of the earths, so hard wire the earth too.

Datatek said:

A smart charger can be left on, a cheapo basic charger will cook the battery. If I have to leave mine I use a solar panel with a charge regulator

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I'd considered the solar charger, but when i spoke to thorn, they couldnt guarantee it would generate enough juice to do the job...then started looking at the CTEK chargers. As I have no garage, it would be good to be able to use a CTEK via an external power socket (on the house) and be able to leave the charger either suitably waterproofed under the car, or in the boot with just the leads protruding.

I bought a 12 volt 12 watt solar panel that's more than enough, needs a regulator to control it. A 6 watt would do the job, look at Maplins or CPC | CPC - Over 100, 000 products from one of the worlds leading distributors of electronic and related products.

I did this
http://www.landyzone.co.uk/lz/f10/battery-charging-socket-fitted-126628.html
Will fit one in the rear bumper as well

javars said:

I did this
http://www.landyzone.co.uk/lz/f10/battery-charging-socket-fitted-126628.html
Will fit one in the rear bumper as well

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The advantage of the solar panel is it can be left at the airport for a month and you know the battery will be good on your return

Will be picking up a tow electrics set soon and still want to explore charging the battery through it when it's fitted. Planned to do it sooner but had other things to sort out!

If a permanent live was fitted from the plug straight to the battery then in theory this would work and avoid any BECM problems if I understand the previous posts correctly. Could this permanent live also incorporate the rear 12v socket? so that like others on here i could leave a solar charger plugged in when it's parked up for holidays etc?

Goodfella said:

Will be picking up a tow electrics set soon and still want to explore charging the battery through it when it's fitted. Planned to do it sooner but had other things to sort out!

If a permanent live was fitted from the plug straight to the battery then in theory this would work and avoid any BECM problems if I understand the previous posts correctly. Could this permanent live also incorporate the rear 12v socket? so that like others on here i could leave a solar charger plugged in when it's parked up for holidays etc?

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Yes, that's what I did on mine. Make sure you fit a fuse at the battery end. Earth the the chassis on any convenient bolt. I ran my cable in a copex sleeve along the top of the offside chassis member hot glued in place plus the occasional cable tie for security

Hi Datatek, did you permanently fix your solar charger or just connect it when needed? Will it work through glass or does it need to be outside? I would be worried about leaving it at airport if outside but really like the idea and would like to adopt. Any other advice appreciated.

peejaybee said:

Hi Datatek, did you permanently fix your solar charger or just connect it when needed? Will it work through glass or does it need to be outside? I would be worried about leaving it at airport if outside but really like the idea and would like to adopt. Any other advice appreciated.

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When I leave it, the solar panel sits on the rear parcel shelf propped up at a slight angle, works fine through the glass. I leave it permanently connected only when needed, at other times it is on my caravan. It operates through a charge regulator so it will not over charge the battery. It's a big 12 watt panel.

Thanks Datatek, I didn't realise they would work through the glass. I will start looking around for one. It's obviously ideal when no power is available as on your airport scenario.

peejaybee said:

Thanks Datatek, I didn't realise they would work through the glass.

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Tinting will reduce effectiveness.

Pete

I've found a solar panel at Maplins that tops-up the battery via the ciggie lighter. But I seem to recall reading the ciggie lighter is useless when the ignition is off?