Solar powered battery charger/maintainer for truck dash

[powerscol]

I have done a search and not found much on this here. My F350 sits for weeks to a month or more at a time without use, and it kills the battery's - especially in cold temps (teens and below 0). Batteries are good, but the parasitic loses do a number. I am looking for a roughly 3 to 5 watt unit, possibly more that has a regulator built in or included so as to not kill the batteries. I found one that plugs into the OBD-II. I assume it uses the car electronics to do the charging maintenance. http://www.northerntool.com/shop/tools/product_200620133_200620133 Neighbor tried one of the cheep HF units, 1.2W maintainer, and it would not work on his ATV so I will go a bit bigger

I would like it to sit on the dash and be stowed able behind the back seat if possible, otherwise water proof to store in the bed under the cap. I have been reading a lot of reviews, wit mixed results, but thought I would ask what brands are working for folks long term. Boss asked what Santa should bring so I though of this, but have no idea which one. I would like quality, but stay under $75 if possible.

Right now, once a month I throw my slow charger on and let it run overnight - a big pain with extension cables, etc.

Anny suggestions folks?

Thanks - Keith
Happy Holidays

 

[CurlyDave]

I have exactly the same problem with my F250.

The problem is compounded by the fact that in winter around here it is overcast a lot of the time and solar chargers just aren't going to work very well on cloudy days.

On a diesel, there is a fuel injection control module called a FICM. Well, low voltage at start up can cause this to slowly fail, and I got FICKed to the tune of $750 for a new part I replaced myself. About $1800 at the dealer.

Preventing this happening again is worth the effort to run electricity to the parking spot for the truck and install a real battery maintainer, which is on my project list for this winter.

 

[Garandman]

I believe if it's less than 15 W you don't need a controller.

If you call up AltE I bet they can help, or post in their forum. Solar Panels, Solar Power Systems, Off-Grid & DIY Solar | altE

Very common on boats and there are roll up panels available.

DIY Charging With Solar Panels - Solar Panels for Boats | West Marine

 

[John_Mc]

Batteryminder makes some very good smart chargers which also include a desulfation circuit. I've never used their solar chargers, but have heard good things about them. I do own 4 of their non-solar models (including one for my aircraft - aviation batteries are EXPENSIVE to replace: hundreds of $) and have been happy with all of them. They are not cheap, but they are good.

BatteryMinder 5 watt solar charger
BatteryMinder 15 watt solar charger

 

[dickfoster]

I believe if it's less than 15 W you don't need a controller.

If you call up AltE I bet they can help, or post in their forum. Solar Panels, Solar Power Systems, Off-Grid & DIY Solar | altE

Very common on boats and there are roll up panels available.

DIY Charging With Solar Panels - Solar Panels for Boats | West Marine

Not true. You can ruin a battery with any constant uncontrolled charger that puts out more change than there is drain. It's a penny wise and pound foolish approach. Spend the extra little bit of money up front to save a lot of money in the end. I put a larger solar panel in my truck up in the sun roof but I also installed a charge controller so it can't ruin my battery and I have two of em in the truck. When it's inside the garage I plug a wall powered unit into it. Those little cheapie dash panels don't put out much even when the sun is shining.
All modern EFI vehicles have some parasitic drain though the ECU then there's the other stuff like clocks and other accessories that often present a small drain. Leave a cell phone charger or a GPS plugged in for example and the LED on it is using 10 to 20 mA if it's on when the key if off even without a even without a cell phone plugged in. This is the leading cause of sulphation and premature battery failure today.

 

[k0ua]

Perhaps this article could help:

What is "normal" for a parasitic draw? | OPTIMA Batteries

Now lets do some math (and maybe a little algebra). I like math, don't you?

Lets take the reported output of the typical harbor freight 1.5 watt solar charger. If we take them for their word that it will actually put out 1.5 watts in full sunlight, and since P=EI or stated in words, the P power equals the E electromotive force measured in volts, times the I current measured in amperes.

So lets plug in the values we know and solve for the ones we don't know. We are going to either make some assumptions in these calculations, or we are going to actually break out the VOM (volt,ohm meter) and make actual current measurements. While the open circuit of those little panels may be around 17 volts or so, when you slap them onto a car battery they ain't gonna rise much above 12.8 volts. Lets see how that works out in our calculations.

P=1.5 watts. so they say in full sunlight. On average I think it will be less, what with dirty windows, clouds, and generally the fact that when things are rated, they are usually best case scenario.

E=12.8 volts.. this is the part I just told you about. It is an estimate, but it is pretty close.

I= the great unknown current. We will solve the equation for I. Or you could get off of your lazy arse and go out and measure it after you have bought this little dinky solar panel.

So here we go now, lets plug in the values and solve for the expected current flow from this little panel
P=EI So 1.5=12.8 (I). So lets divide through both sides of the equation to come up with 1.5/12.8=I 1.5/12.8 is 0.11718975 amperes

So now we know our I (current) is .117 amperes or stated in more convenient terms 117 milliamperes. Now according to the article, the guy measured his GM product to have a parasitic draw of 60 milliamperes. So we we slap on one of these little solar chargers, it would overcome the parasitic draw of 60 milliamperes quite nicely with about 57 milliamperes to spare.

OK, but the sun doesn't shine all the time. There is the nighttime thing. So now it is looking like maybe the little solar charger might just might barely keep up with the parasitic draw.. but there is the cloudy day, dirty windshield thing too.. So now it might be a little iffy.

BUT in any case the solar charger is for sure going to be better than doing nothing if you let your car sit for several days or worse weeks in a row. AND a small charger like this is sure in he77 NOT going to overcharge your battery. No way, no how, not even. It would be lucky to even keep up with the internal resistive losses inside the battery itself, and possibly the parasitic load draws, possibly. But it will be better than nothing. Not as good as a fully charge controlled trickle charger, for sure, but not a bad deal at all for the money.

So there you have it, and if you don't like my theoretical calculations, then go measure the current draws and the charging current provided by one of these little solar chargers yourself?

 

[Garandman]

Not true. You can ruin a battery with any constant uncontrolled charger that puts out more change than there is drain. It's a penny wise and pound foolish approach. Spend the extra little bit of money up front to save a lot of money in the end.//

From the West Marine FAQ:

As a general rule panels that produce less than 1.5% of a battery’s rated capacity in amp hours don’t require regulation. This means that a 1.5A [18W @ 12V] panel is the largest you should use without a regulator on a 100-amp-hour battery. Regulators should generally be used any time you have two or more large panels connected to your batteries.

If you’re concerned about damaging your new gel or AGM batteries due to overcharging, you can add a small, inexpensive charge controller.

 

[powerscol]

OK folks, this is what I am looking at. A 15 watt charger (can be used for camping too) with an OBD2 connector. In checking my truck, I find the power port/cig lighter to be dead when key is out so cant use to charge. This leaves the OBD 2 port. Will this work?

What I am considering - can be found cheaper
15-Watt Solar Panel by Battery Tender - Free Shipping: BatteryMart.com
SAE to OBD2 Connector Plug: BatteryMart.com

I believe the SAE connector is the typical 2 prong quick connect from what I found and is the connection off of the solar panel cable.

Thoughts?

On edit, I found a live power port, so which connection would be better - power port, or OBD2?

 

[1stDeuce]

Grandman, that's a much more realistic guideline for when a charge controller is necessary than I've seen on solar sites!
I suggested on another thread that for a tractor sized battery, 10W would be fine w/o controller, and got some flak...

Most solar sites I've checked suggest dividing Battery Capacity (Amp-hours)/Panel Max Power Current (Amps), and that 200 is the cutoff. Less than that and you need a charge controller. That equates to .5% by the West Marine method... (Hey, Solar places sell panels and controllers, why not sell more, right?)

I suggested that my experience is that between 80-100 is a more realistic cutoff, and that is nicely supported by West Marine's 1.5%, which would be about 67.

I think the problem still is that most solar places treat solar power like wall power, and it's not... As suggested above, it's part time only, and peak output is short lived...
Even though the theoretical output would cook a battery in short time if it was constant, it's intermittent at best, so it really is fine.

For the OP, I'd aim for a 10W panel for a single truck battery, and if it has dual batts, 10-20W would not be out of line. You could buy someone's pre-packaged setup for ~4x more than it's worth, or just get a nice panel and mount it. Personally, I'd use dual-lock to mount a real panel to the hood or roof, and wire it directly to the battery through a diode. The diode keeps the panel from being another current drain at night, and you won't have to plug it in, or stash it, or even think about it ever again.


There are some nice flexible panels available now that would work great if siliconed down... You'd never see one on the roof of the truck.

 

[1stDeuce]

OBDII is a more solid connection than a cigarette type port. Plus you almost never use it, so it wouldn't require plugging/unplugging. The power port of OBDII is usually fused at 15A, so that shouldn't be an issue. Actually, it's often the same fuse as a constant power port, now that I think about it.

I'd still go for a hard mounted panel, so you can't forget about it, or be annoyed by it, but that's just me.

$110 is a lot to pay for a $20 panel.... This is the style I mount with dual lock and leave alone: Ebay link