Solar panel to keep 12v starter battery charged

[leec]

I currently own a VW Jetta TDI and keep a solar panel plugged into the accessory socket whenever I'm not driving the car to ensure my battery stays charged. Given that the MiEV relies on a 12v starter battery, wouldn't it make sense to do the same thing for it?

I'll be keeping my MiEV parked on the street and charging it whenever I venture in to work where they have level-2 chargers freely available, so I want to make sure I don't strand myself by draining the starter battery through my excessive accessory use (car computer, security systems, etc.)

 

[Don]

Unless it stays parked for a month or two without being driven, I doubt you'll ever have a problem

Don

 

[dsmall24us]

I would like to trickle charge the 12v battery as well as I will be parking in a sunny spot all day but I don't think the 12v socket is hot when the car is off so I don't think you can do that without some modifications. Anyone know of any easy way to do that?

 

[Don]

The 12 volt battery is full each time you shut the car off - Unless it sits for some time, it wouldn't even accept a charge . . . . unless your trickle charger is unregulated and it's capable of overcharging it

I wouldn't look for a solution when there's no problem - That is, unless the car is going to be left sitting for an extended time. My first ptiority would be to find some way to park it in the shade (portable carport?) or in a garage. It's a shame to leave $30K sitting out on the curb

Don

 

[merlino]

Mixed reviews. I'd prefer to park it under the Sun and share some energy with it. And your doing the right thing. Renewable energy is extremely needed. So, if you are using it even by a bit, then you are taking part the Energy Saving venture. Attaching it with the 12v Starer battery is also a well thought output. Just don't go by others opinion.

 

[JoeS]

Have to chime in here.

leec, dsmall24us, and merlino: do try to go back and understand what Don wrote. There is no problem here - do the math first before trying to find a "solution", as the amount of energy you're talking about feeding back into the 12v battery is miniscule.

leec - what sort of accessory use are you talking about that you think will drain the 12v battery? When you leave the car locked then the alarm system current drain is minimal - certainly nothing that needs replenishing when the vehicle is used on a daily basis.

merlino - uncalled-for comment, as, if you research Don's posts, you will find his many well-thought-out technically-savvy contributions to this forum. Many of us make extensive use of solar where it makes technical sense - solar charging the very-lightly-loaded iMiEV 12v battery is not one of them, unless you're talking about longer-term storage. BTW, I have a number of cars in storage on my property that do, indeed, have tiny solar panels feeding 12v batteries through smart regulators.

To focus this discussion, perhaps one of you would like to measure the current draw on the 12v battery when the car is parked and locked and then calculate how long it will take to deplete it to, say, 60% SOC? That would give us all a good idea how long we can leave the car unattended before bothering to float-charge (NOT trickle-charge) that 12v battery.

BTW, I'm with Don and avoid parking out in the sun if at all possible!

 

[oahumiev]

BTW, I'm with Don and avoid parking out in the sun if at all possible!

I'm surprised at how many EV charging stations here in Hawaii are located in direct sunlight and all the other elements as well. Not only would a charging station located out of the elements require less maintenance, but my Miev wouldn't be parked in the hot sun for hours at a time while charging when there is covered parking just a few stalls away :? Guess I should just be happy that we have an abundance of charge points, wish they would think beyond just where is the closest stall to their power source.

 

[merlino]

Is there any bad effect to the car whenever it is parked under the heat of the sun for hours? I don't think it is a good idea but is it possible if only the solar panel is being expose to the sun and the car is still on the safe zone ( not directed to the heat) ? :?

 

[nsdivene]

I'm considering adding a solar panel to keep two 12V batteries charged on a 33' cutter that leaks a little - a Rule 500 gph pump cycles on for perhaps 30 sec. every 30 min. Hopefully I'll be able to diminish that, but I often can't get to the boat for a week at a time. I'm concerned that there have been times when this has run the batteries down, and, at a low charge, sulphation increases.

We use electric power minimally - engine starting, bilge pumps, running lights, and a little occasional lighting. No refrigeration, etc. We primarily use kerosene and candle lanterns for interior lighting at anchor.

electrical service sydney

 

[iMiEVNZ7]

Hi,
I have the same problem on my boat, it comes from the prop gland.

I have a 100 Amp AGM battery, Lifeline brand, that I charge with a 20 watt I think, Solar Panel, and feed this via the !2 volt Socket in the Accessories circuit. the battery seems ok even in winter.

It seems to do a good job and I have Two other 80 Amp hour AGm Lifelines on board as spares that we charge up now and then.

THe boat has one for starting, one for house and one for the Winch, and I am wiring in a Ring Feed Circuit with welding thickness cables, to feed high current to the bow where the battery for the anchor winch underdeck.motor .

That way I can take a feed circuit off the main ring feed anywhere along the ring with minimal voltage drop.

I think with solar panels now only about 3$ Aus per watt, and a good solar controller about $ 200 at 30 amps with a cool readout guage, A few 80 watt or higher panels would allow easy recharging without worrying about over charging and would allow bigger batteries if you wanted later, for things like lighting and a TV. http://www.trademe.co.nz/Trade-Me-Motors/Caravans-motorhomes/Parts-accessories/Solar-panels-accessories/photos/a-498089826/p-202641772.htm

Has a picture of a neat looking controller.Another brand Morning Star ones are supposed to be the best ones though I think.

When sizing battery capacity and panels always go for as much as you can afford and add as you can, it makes not worrying about leaving gear on long great.

I leave the radar on all the whole trip for fun and training. It helps to take a few photos of the radar display at differing settings, while in the mooring, and print them and laminate the photos to place beside the radar for handy referance in fog or dark to know what it should look like, A few all around photos on a clear day printed and laminated are also great for bearings and matching to the radar.

Having a remote activated solar powered light on your own mooring is neat too !.

 

[MLucas]

How did we go from cars to boats?

I'm with Don and Joe on this one, leaving the car out in the hot sun will cause more of a strain on your main battery than trying to recover a couple of cycles on your starter battery. The drain will come from trying to cool the car down after you get back in. There also have been reports of Leafs in the southwest with degraded batteries from sitting out in the hot sun.

The starter battery is a 33ah hour battery which is recharged from your main bat pack. I wouldn't worry about it.

 

[Don]

The starter battery is a 33ah hour battery which is recharged from your main bat pack. I wouldn't worry about it.

Plus, it's got a pretty easy life - It's not stuffed into a hot engine compartment and it never has a starter motor sucking 100 amps from it everytime you start the car. The 'ding-ding' on our car means the DC to DC converter has come on and it's being recharged even before you can move the car

Don

 

[leec]

My use case is running a small computer server (a Raspberry Pi) in the space behind the stereo. The lighter plug disconnects when the car is "off". The 12v system is on when the starting switch is in accessory mode (with the DC-DC converter off). At this point I'm planning to have a separate battery with the server and a circuit to keep it charged from the solar cell. It will be supplemented by the stereo USB power whenever that's powered on so it won't need to run on solar power exclusively.

The power draw of this server is minimal but I'd rather not risk having a dead 12v battery if it misbehaves.