Solar n00b with question on keeping car battery topped off..

[v_man]

Apologies if this is the equivalent in the solar world of asking what size tires can I fit without a lift, but here goes...

I have a big 4runner that I only drive about once a week, and then short distances at that. I'm looking for a solar solution that will keep my one and only starting battery topped off, or at least from discharging as fast. I'm not trying to power a fridge out in the desert, just help my poor little starting battery fight the neglect of not being used much...

A couple caveats: I have to park out on the street in front of my house, so running a batt. tender from my garage across the sidewalk isn't really feasible. I want to mount a solar panel inside my truck window, for security reasons. I have about a 18"x24" large rear window to mount it in...

So my questions are : Any idea how many watts my panel should be to keep up with discharge from battery just sitting there? And secondly, does mounting a panel inside a clear window diminish the ability of the panel to charge properly?

And FWIW, the panel would only get about 5-6 hours of reliable light a day right now (winter)

Thanks... here's pics if that helps...

 

[Ducky's Dad]

A few years ago I tried some small solar panels sold to keep batteries topped off. These were maybe 10"x20", sit on the dash board, and plug into the cigarette lighter. I think they were Noco. Tried three different panels in three different vehicles in Southern California sunlight, and none would keep the battery up. Bottom line: They were a waste of money. Lesson learned: Get a bigger panel and wire it to the battery.

I recently installed a 2W Solargizer panel on the cowl of my truck to try to offset the parasitic drain from the computer and alarm. It has its own controller, includes pulsing to mitigate sulfation, and is wired directly to the battery. My calculations indicate that the panel should be putting out enough to offset the drain, but it does not seem to be working as planned. I'm still evaluating whether it was a waste of $100. Probably was. Get a bigger panel.

 

[Jason911]

Echoing the previous poster, but with positive results. Also a solarigizer, but one for 12v model. Are also made for 12v-24v switching, 12v marine and dedicated 24v as well as 24v military applications. Another option is getting/finding a 12v battery maintainer that comes on VW's shipped from overseas - these come either with a cig outlet or plug into the OBD port 9 designed to lay on the dash/front windshield suction cup. I've heard a few rumors that the solargizers were designed to work outside the vehicle for optimum results, where as the VW ones were designed for inside vehicle usage. Maybe try eBay.

 

[IdaSHO]

A few years ago I tried some small solar panels sold to keep batteries topped off. These were maybe 10"x20", sit on the dash board, and plug into the cigarette lighter. I think they were Noco. Tried three different panels in three different vehicles in Southern California sunlight, and none would keep the battery up. Bottom line: They were a waste of money. Lesson learned: Get a bigger panel and wire it to the battery.

You sure your cig-lighter was energized with the ignition OFF?

Unless you have a serious drain or a faulty battery (or a cig lighter that turns OFF when ignition is OFF), even a small 2 amp solar charger is plenty to keep a parked vehicle battery topped off.

All that said, a tinted side window is about as bad as it gets for solar production.

 

[jonyjoe101]

A 30 watt panel will give you about 1.5 amps of charge power, that would be the minimum you need to keep your battery topped off, 60 watt will give you about 3 amps. Thats in the best conditions with the panels outside. For these panels all you need is a 10 amp wincong pwm controller (about 15 dollars) and the wires (about 10 or 12 gauge wire) to run to your start battery. You can keep these panels connected 24/7 without damaging the battery.
The smaller panels you see at autozone provide only milliamps of charging power, it will even state on the box that it wont charge a completely dead battery. These larger panel will charge a dead battery but it might take several days to do it, but it will charge them eventually. A good rule is you get about 1 amp of power for every 20 watt of panel.

Your best bet is to bolt it to the roof of your vehicle and paint it to match your vehicle, I doubt anyone will mess with it, if the panel is inside the car and someone really wants it they will break the window and take it. Bolted on the roof they need tools and ladders to steal it. I've had both 120 and 240 watt panels bolted to the roof of my astrovan for the past 4 years and park in the street and no one has try to steal them. The tough decision is drilling 5 holes on the roof ( 4 for the panel and 1 for the wiring) as long as you use rv putty tape you shouldnt have any problems with leaks, I got holes all over my astrovan roof with fans and vents and never had any leaks.


Another option is to have a jumpstart pack and keep that always plugged in inside your house until you need it. Myself i have a small fullriver 28 ah agm battery. Its a small battery that I can swap out the start battery and use it until I recharge my main battery. Its a small battery but its a very powerful battery and can be used as a cranking battery for a fullsize vehicule.

 

[Ducky's Dad]

You sure your cig-lighter was energized with the ignition OFF?

They are all hot with the ignition off. No tinted window issues because the Noco panels were on top of the dash, so only whatever factory windshield tint that the vehicles came with. The Solargizer is mounted on the outside cowl of the truck, so always gets direct sunlight. No unusual parasitic drain, has been checked and rechecked and re-re-checked, all within spec and less than 50 milliamps.

 

[v_man]

Thanks for the info everyone...

 

[IdaSHO]

They are all hot with the ignition off. No tinted window issues because the Noco panels were on top of the dash, so only whatever factory windshield tint that the vehicles came with. The Solargizer is mounted on the outside cowl of the truck, so always gets direct sunlight. No unusual parasitic drain, has been checked and rechecked and re-re-checked, all within spec and less than 50 milliamps.

Then how were your batteries not staying charged? Eh?

No parasitic draw, and still not staying charged? Your math doesnt add up.

You dont need solar to keep things charged.

Unless the cheap panel you purchased allowed discharge as well.
Some do, when the sun goes down.

 

[IdaSHO]

A 30 watt panel will give you about 1.5 amps of charge power, that would be the minimum you need to keep your battery topped off

How do you figure?

Even at 1.5A for just 6 hours a day are you assuming the discharge rate of a battery with zero load is 10amps per day??

What are you saying here?

FYI, the average discharge rate of a lead acid car battery with zero load (self discharge) is roughly 5% per month, or less than 1 amp per week, depending upon temperature and (obviously) age and condition of battery.

 

[4x4junkie]

I've kept batteries topped up no problem using just a 5W solar panel and a little homebuilt charge regulator set to 13.8V. So yeah if a 10"x20" panel (at that size it should be about 15-20W) can't keep it up, then either there was a faulty connection, or you did have some really serious parasitic drain on it.

Clear window glass shouldn't appreciably lessen a solar panel's output, but I agree mounting it on the roof would be much better. That rig looks tall enough, most people walking by probably would never see it anyway (and if they did, would probably see only the edge of it and figure it's just part of the vehicle). A 5W panel these days is maybe 8-10" square so shouldn't attract much attention.

 

[Ducky's Dad]

Quote Originally Posted by Ducky's Dad View Post
They are all hot with the ignition off. No tinted window issues because the Noco panels were on top of the dash, so only whatever factory windshield tint that the vehicles came with. The Solargizer is mounted on the outside cowl of the truck, so always gets direct sunlight. No unusual parasitic drain, has been checked and rechecked and re-re-checked, all within spec and less than 50 milliamps.

Then how were your batteries not staying charged? Eh?

No parasitic draw, and still not staying charged? Your math doesnt add up.

You dont need solar to keep things charged.

Unless the cheap panel you purchased allowed discharge as well.
Some do, when the sun goes down.

You are starting to irritate me.

First, I did not say my batteries were not staying charged. I said my batteries were not being being successfully maintained by the small solar panels I have tried. I have not tried all the panels available and I have not tried large panels. The Noco panels were recommended and endorsed by the big battery distributor (not a retailer) from whom I normally get my Optima and Odyssey batteries. The Solargizer with its two watt (not two amp) panel was recommended by a friend who has the same year and model truck that I installed mine on, and he has had great success with his. The difference may be that he is running a Grp 65 flooded lead acid battery and I am running a Grp 31M Odyssey 2150, which is notoriously difficult to maintain. I have no trouble maintaining the batteries in those vehicles that are running single or dual Optima Red and Yellow, or single Odyssey 1500 Grp 34, or the dual Optima Blue Grp 34 DP house batteries in my main truck, or the Northstar 31M in my DD Tundra, or the old Grp 34 Odyssey 1500 that was my house battery for about seven years. The main issues I have are with the Odyssey 2150 in a truck that does not get driven regularly and with a BMW that does not get driven regularly. BMWs are also known somewhat for unusual battery protocols.

I never said there was no parasitic draw (drain). Read my post again and you will note that I stated it is within spec and is less than 50 milliamps, and has been checked multiple times by me and by professionals, and drain specs were confirmed with the service manager (not a service writer) at the biggest dealer in the area. My parasitic drain is just fine, thank you. And my math is just fine, as well. Three master's degrees including an MBA have given me some ability to run numbers.

I never said I or anyone else needs solar to keep things charged. This discussion is in the context of maintaining AGM batteries in vehicles that are not driven regularly. The solar panel is intended to be an alternative to a maintenance or trickle charger in my case. If you read the threads here on the Odyssey 2150, you will find my prior posts related to my multiple conversations with Odyssey tech support and Odyssey management in which they told me that a 2150 must be put on an approved charger/conditioner at certain intervals to keep that battery healthy. The solar (in my case) is intended to stretch those intervals.

Finally, I did not buy cheap panels. The Nocos and the Solargizer were just under $100 each, and I got the Nocos wholesale. They simply don't put out enough amperage in the light conditions I have to do the job I wanted them to do. And yes, I have tested them with a multimeter and they do work. And there is no indication that they are discharging the batteries at night.

IdaSHO, I'm not sure what your vehicle is, but note that modern vehicles have all kinds of electronic crap on them that constantly drains batteries while the vehicle is parked with everything shut off. The computer never sleeps.

 

[IdaSHO]

[Daddy's duck, please do not take any of my poss (or anybodys posts) personally.

My posts are never directed at an individual, personally, but at the posts at hand.

This is all in good fun and education. Its a public forum.

First, I did not say my batteries were not staying charged. I said my batteries were not being being successfully maintained by the small solar panels I have tried.

To be fair, THIS is what you said:

A few years ago I tried some small solar panels sold to keep batteries topped off. These were maybe 10"x20", sit on the dash board, and plug into the cigarette lighter. I think they were Noco. Tried three different panels in three different vehicles in Southern California sunlight, and none would keep the battery up.

Nowhere did you mention "maintaining". And IMO keeping batteries topped off = staying charged.

Battery maintenance is a completely different subject as true battery maintenance involves more than a trickle charger.

I never said there was no parasitic draw (drain). Read my post again and you will note that I stated it is within spec and is less than 50 milliamps, and has been checked multiple times by me and by professionals, and drain specs were confirmed with the service manager (not a service writer) at the biggest dealer in the area. My parasitic drain is just fine, thank you. And my math is just fine, as well. Three master's degrees including an MBA have given me some ability to run numbers.

yet a 50 milliamp drain is sufficient to overcome a small (even 20W solar panel?

They simply don't put out enough amperage in the light conditions I have to do the job I wanted them to do. And yes, I have tested them with a multimeter and they do work.

I thought this was in Southern Ca direct sunlight?

And what personal requirements did you apply to this job? What job exactly do you want these panels to perform? Specifically?

IdaSHO, I'm not sure what your vehicle is, but note that modern vehicles have all kinds of electronic crap on them that constantly drains batteries while the vehicle is parked with everything shut off. The computer never sleeps.

No worries, Im sure is only about 50milliamps. (tongue in cheek)



My truck is a '96 F350 diesel.

Two large 1000CA batteries, standard lead acid.
It as well is not driven for months on end.

Even with such massive batteries, and two of them, a cheap 1.5A trickle charger (Schumacher SE-1-12S) is enough to keep them topped off when parked long term.

This is why i have trouble believing even a small panel would have ANY trouble keeping your battery topped off.