Solar trickle charger through power socket

[L777JDP]

Hello,

First post as I can't find an answer to these questions. I'm trying to determine whether the battery on a 2013 Roadsport 140 can be trickle charged with a solar panel through the power socket? This is for when it is laid up over the winter, so not urgent, but may take some time to research. Its a lockup garage in a block and there is no power and no prospect of getting power. I've seen people say to isolate the battery, but the only thing that would be pulling power would be the immobilizer so presumably this would be very low.

If the weather is good it would be great to take it out, so I don't want to have to reconnect the battery and put the bonnet back on. Just unplug and go.

Thanks for any comments, suggestions, thoughts would be appreciated.

John.

[Jonathan Kay]

Factory fitted? And do you know how it is wired?

Battery master switch?

I wired my socket directly to the battery and would be happy to connect a solar panel with an appropriate control system.

... but the only thing that would be pulling power would be the immobilizer so presumably this would be very low.

That's come up a lot in relation to intermittent use and smart chargers etc. I've come to the conclusion that it varies between cars. I'd probably measure the current and compare that with the output of the solar panel.

The other thought is that we once had a discussion about solar power to isolated garages. That would allow lighting as well as charging...

Jonathan

[JNC]

Beware the solar panel I bought for my mums car boiled the battery dry it cost me a new battery , I don't think it had a  regulator to control the output voltage. 

[Sussex Mid AR]

i have heard of the problem John [JNC] had before so beware, his problem is not a one off. As he says get one with a regulator built in. In your situation fitting a battery master switch is a good idea. 

This type are available for fitting underbonnet if you don't want to fit yhe Caterham external one. You would still need to remove the bonnet but no spanners required to reconnect each time.

Julian

[AdamQ]

I've just got a cheap and cheerful non-FIA battery master switch out of sight under the dashboard - one of the best modifications I've ever made as it pretty much removes the ? over whether or not the car will start after a lay-up of a few weeks (ISTR it took about three weeks on my car for the immobiliser light (and whatever else might have been sapping charge) to drain the battery just enough to cause starting problems).

[Delbert]

Having recently invested in significant solar on my NB I would advise walking away based on cost 

the panels that do not need a controller cannot even charge an iPhone 

so a controller is needed between the panel and the battery 

additionally winter solar is almost insignificant and at the best in consistent 

[Wodybode]

I have an old (very) Toyota Rav that has an alarm and immobiliser that drains the battery over a couple of weeks. As it only get's infrequent use I wired a cig lighter socket direct to the battery with an inline fuse and I plug in a £15 solar panel with inbuilt regulator and it maintains the battery perfectly. I've been doing it for years. The panel just gets left on the dash and works fine winter and summer (though the car is outside all the time) and gets slung in the door pocket when the car is in use.

[mike150]

I'd avoid a solar charger as you will not know if it's over or under charging the battery.

 

Get a Ctek MX5.0 and charge any car or motorcycle with it with no fear of damaging a battery. You can buy a 12v lighter socket lead for one and it saves you opening the bonnet.

[John Vine]

Get a Ctek MX5.0...

The snag is the OP doesn't have a power supply in his garage.

JV

[mike150]

My bad. Excuse me, I'm on the drink in Spain right now.

[mike150]

Get a generator too!

[RogerB]

I have just fitted one to my boat which although I,m pleased with doesn't put out as much current as I had anticipated for the wattage of the panel. You definitely  require a voltage regulator to prevent overcharging. I found my supplier was helpful with advice on what was required. Your charging requirement will obviously be much less than mine and charging through the lighter socket is a convenient solution providing that remains live when the ignition is switched off.

[Jonathan Kay]

Its a lockup garage in a block and there is no power and no prospect of getting power.

Other variations include an additional battery that charges when the sun shines and can be used to charge the 7 and help start after hibernation. And can light the space, preferably with LEDs, and might just power other things.

And another battery on wheels or similar that can be charged elsewhere and taken to the garage, perhaps once a week.

Jonathan

[L777JDP]

All,

Thank you so much for your comments on this. There is a factory fitted 12V power socket at the back of the car (it's a 2013 Roadsport 140). I'm going to see if I can find out how that is wired in to the battery as simply pushing a small amount of power into that would be the easiest.

So, my plan is a solar panel around 20W I guess, and push the output through an Anself 10A 12V LCD Solar Charge Controller with Current Display Function Auto Regulator for Solar Panel Battery Lamp Overload Protection.

As pointed out in the thread, the only thing likely to be draining the battery is the immobilizer, and being relatively recent I suspect that its power drain is likely to be quite low anyway.

Best wishes, John.

[revilla]

On a K Series car, there can be a lot more than the immobiliser draining current from the battery when the car is standing. There can be enough current leakage through the ECU drivers for things like the injectors and ignition coils to flatten the battery in a week. Some cars were wired with a Master Relay in the MFRU which shuts off the supply side of this leakage, other cars were wired without using this relay. Not sure why the difference; given that the relay is identical to the one implicated in some K Click problems they may have decided to omit it on reliability grounds. You can tell if your car is wired to use the Master Relay by looking for a thick Brown/Blue wire on the larger of the two MFRU connectors (from memory I think bottom right hand terminal as viewed from the wiring side). Cars without the Master Relay (such as mine!) tend to drain their batteries at a very much higher rate than those with. @Jonathan this may explain at least some of the variation you describe.

[Jonathan Kay]

Hope it goes well.

If it doesn't just work out of the box it would be interesting to measure the leakage current and what the panel supplies and what that control system does.

Jonathan

[revilla]

Jus to add some numbers to my previous comment; based on a not-necessarily-representative sample of one:

Test Engine Rig (Standard Immobiliser, Identical to Car Except Uses Master Relay)

• Immobiliser: 9.0mA
• ECU & Engine Loom: 0.2mA
• Total: 9.2mA

Car (Standard Immobiliser, No Master Relay)

• Immobiliser: 9.0mA
• ECU & Engine Loom: 13.0mA
• Total: 22.0mA

​So parked-up current drain is nearly two and half times higher without the master relay due to leakage through the ECU.

[Jonathan Kay]

Mmmmm... data.

Usual bizarre unit of stored energy* for car batteries is Ah. Typical small batteries in Sevens might be 20 odd Ah.

22 mA ≈ 0.5 Ah per day.  So about 20 d to run a good battery down to half capacity.

(Please could someone check that arithmetic?)

Jonathan

* Just to preempt the SACP...  at the known voltage.

[John Vine]

Please could someone check that arithmetic?

Looks OK to me.  Of course, the typical 7 battery (Banner 53034) is rated at 30Ah, so would last 30 days to reach half capacity.

Usual bizarre unit of stored energy*

A units pedant would say that Ah is a unit of electric charge, and that energy would be kWh.

JV

[aerobod - near CYYC]

Or a standardised units pedant would use Joules for stored energy :)

[Jonathan Kay]

Thanks for checking.

Yes, joules, please. But lower case. And how do you pronounce it... and how did he? ;-)

Jonathan, standing in for the SACP

[L777JDP]

Thanks everyone for your help with this. Just to recap, it's a 2013 Roadsport 140 and its in a lockup garage with no power, and no prospect of getting any.

According to Caterham, the Toad / Stirling Excel immobilizer which is what, from independent research, is fitted I believe draws about 0.5A to 0.6A when it is on. This seems huge to me, but does seem to be consistent with what people have reported above and elsewhere about the immobilizer draining the battery enough to cause starting problems in 2-3 weeks.

12V * 0.6A = 7.2W. Not much, but given that there can be only 1 hour of useful sunlight in the winter, I've been advised I would need a system that can supply 24 times this amount, so a 100W system as an absolute minimum (fed through a good quality battery conditioner). That would be a panel around 0.5m x 1m. This is at variance with Wodybode's experience with his Toyota, where a much smaller system (about 20W I would guess) seems to do the job.

I'm looking into fitting a Caterham battery master switch, and noticed on the parts website that it has 4 spade terminals coming out of it, so I'm wondering if when the battery is isolated the immobilizer is still on. If anyone knows the answer to that I'd appreciate it.

Thanks and best regards, John.

[Jonathan Kay]

What's the rough cost of the emerging solution: panel + control system + bits?

Jonathan

[L777JDP]

Hi Jonathan,

It looks to be about £150 for a 100W solution all in. The snag is that it will be about 0.5m x 1m in size to go on the flat roof of a garage, and so not so easy to prevent blowing off in high winds, especially as ideally it will need to be angled and not laid flat, so it will catch the wind. It's also wouldn't be too discreet and I don't really want to attract attention to the garage.

I am still struggling to convince myself this is the right way to go. If its a nice crisp winter's day with dry roads then I'd like to just be able to start it and drive off, hence not wanting to reconnect the battery or even take the bonnet off.

I have an email in to Caterham to ask if the battery master switch truly isolates the battery from everything that draws power then I think I might just go down that route. Ideally I'd like to have that be the case, but still have the 12V socket connected so I can attach a small solar charger.

I wonder how the immobilizer deals with having its power cut off and turned back on again. Anyway, I'll see what they say.

Cheers,

John.

[Jonathan Kay]

I'm looking into fitting a Caterham battery master switch, and noticed on the parts website that it has 4 spade terminals coming out of it, so I'm wondering if when the battery is isolated the immobilizer is still on.

I've had a quick look in the archives and found:

1. The factory switch and wiring immobilises everything, probably because...
2. ... it's aimed at compliance with racing regulations. Hazard warning lights might be an exception.
3. A Guide.
4. There's a safety issue with requires a resistor to protect the alternator.

But if you're fitting and wiring one and don't need to meet those regulations then you can take the feed to the immobiliser from where you choose. Ditto accessory socket.

Jonathan