Fully charged battery discharged with solar battery maintainer plugged in


I had this http://www.amazon.com/gp/product/B004ZC3TFC/ref=oh_details_o09_s00_i00?ie=UTF8&psc=1 plugged in to the dashboard cigarette lighter port on a 2009 Nissan Altima SE with a fully charged battery for 2 weeks facing the California sun for at least 8 hours a day. Came back from vacation after 2 weeks and found battery was dead.

One odd thing that happened when I plugged it in is that the radio automatically started playing even though the car was not started. So, had to turn off the radio before locking the doors.

Trying to understand:

  1. Why did the car battery discharge so it wouldn’t even start with this solar battery maintainer plugged in?
  2. Why does the radio start playing whenever I plug this in?



I suspect that solar charger actually cooked your battery over that 2 week period

The reason I suspect this is that the solar charger can’t regulate its output

I once measured the ouput of one of these solar chargers, and it was putting out 16 volts

The cigarette lighter and the radio are almost certainly on the circuit. That would explain why the radio was on. The sun was “providing” power for the radio . . . LOL

IMO . . . those devices aren’t all they’re cracked up to be

But look on the bright side, you’ve now got a new battery, right?

Battery life is typically 4 - 5 years.

I advise you to NOT use that device again.

1 Like

Does the cigarette lighter port on your car normally operate when the key is off and out of the ignition? I suspect it doesn’t. If it doesn’t, then by plugging in your device you actually actuated a number of circuits that shouldn’t be on when the key is off, like the radio.

There’s no need to do anything for a car that’s sitting for 2 weeks.

@db4690, I’ve used a good-quality solar battery maintainer over a period of months and it has worked well. If the OP’s maintaner was functioning normally I doubt it cooked the battery. More likely asemaster is correct.

Yes, @asemaster. I feel sure that the device had an instruction manual that mentioned connecting directly to the battery if the power outlet was operated through the ignition switch.

In older cars the lighter connects right to the battery, through a fuse, and the power to it is always hot, irrespective of the key position. So you can torch up even if you forgot your key. In modern cars, esp those w/body control modules, there may be a diode or relay in between the battery and the lighter. This is done in part to offer some protection to the very expensive to replace body control module (& ECM) if somebody accidentally installs the battery backwards, reversing the polarity. I don’t have a wiring diagram of your car, but if you can find one, you’ll probably see that what you are trying to do can’t be done. When you connect voltage to the lighter, you are powering up the BCM circuitry, allowing you to run the radio, but the voltage isn’t making it to the battery. If you want to do this, and you’ve confirmed what I’m saying here about the way your car is wired, you’ll have to bypass the diode and/or relay, and hook the charger directly to the battery. If it is something you do all the time, an auto-electric expert could provide a special under dash connector for this. You probably want to consult w/Nissan on this too, as there may be a reason why even hooking a charger directly to the battery isn’t recommended, as doing so could damage some other component, like the voltage regulator or alternator.

The “Battery Maintainer” solar chargers that I have seen are usually limited to just a few watts, 1/2 amp maybe… That’s not enough to overcharge a car battery. Sounds like your car will not tolerate being back-fed through the lighter socket as asemaster said…It’s either that or the battery simply failed…

Interesting that @asemaster is getting credit for suggesting that the solar charger is actually back-feeding the car

If you’ll look at this thread, you’ll notice that I mentioned it first

Nothing against you, @asemaster

Thanks everyone for helping me understand what’s going on here. I jumped the car today and everything works fine.

My car has two 12v ports, 1 in the dashboard that is controlled by the key and the other in the center console that is always hot. I had used the one in the dashboard previously. Seems now that using the one in the center console should work on my car. I will try that out tomorrow. If the radio stays off after plugging it in, I will try that port next time I am going out of town for while.

Whoever flagged me “off topic” displayed some cold hearted behavior

If you’re going to credit someone with the solution, make sure the right person gets the credit

I have nothing against @asemaster

It’s just that I beat him to the punch this time

Now flag me again

Thank you, sir! May I have another?!

@db4690, Oh man, I wasn’t trying to steal your thunder… :slight_smile: Just said the same thing you did in different terms. I guess we must think alike sometimes. What’s with the flagging?

@bangali, why? Unless your trips are a couple of months or more I can’t see the need to do anything to charge or maintain the battery. Have you had issues with the battery going dead before?


You just explained it more intelligibly than I did

Guess I’ll have to bone up on my writing skills


Like I said, I don’t have any problems with you at all. And I know you’re not trying “to steal my thunder”

“I guess we must think alike sometimes”

I would hope so, considering we’re in the same business.

“What’s with the flagging?”

A very good question . . . perhaps my combative nature brings out “the best” in others

@asemaster yes, i have. almost guaranteed that if i leave that car sitting for 4 weeks it will not start after that.

Disconnecting the battery should prevent discharging for up to 4 weeks. All things considered disconnecting it results in less grief than the problem discussed here.


I also live in southern California. I have a car that sits for months at a time, on the street, in the hot sun. It always starts up, and the battery’s already a few years old.

Has anyone verified that you don’t have any parasitic draw?

Has anyone tested your charging system?

Do you drive long enough to keep the battery charged?

What I mean is . . . is your driving mostly down to the corner grocery store and back?

You may want to consider the idea that @RodKnox had . . . or install a battery cutoff switch

Just throwing some ideas out there . . .

This board is not the place for ego tripping…Nobody is keeping score…The OP does not care who is on base at first…


It was me

I just disagreed with you

Unlike some others, I admitted it

@db4690 the battery is about 4 years old. since we have an extra car in the family this one does not get driven often enough. but, when it does it’s mostly highway miles about 25 to the office and back.

plugged the charger in to the center console today, radio did not go on. i will take that as a good sign and try to start the car in about 4 weeks. let’s see.


I’ll give you a heads up about the battery

It is on the downslope, due to its age. Battery life is typically 4 - 5 years. Heat kills just as many marginal batteries as cold weather. Something to keep in mind

I’m glad to hear you drive it far enough to keep the battery charged . . . assuming the charging system is working properly

I believe a parts store will test your battery for free. They can take the hand-held tester (if they have one) out to your car, so you shouldn’t have to remove the battery

If you have it tested, don’t be surprised if it tests bad, or if its current capacity is only mediocre

One more thing, if the battery has removable caps, make sure the electrolyte level is correct

Quote from GeorgeSanJose: “even hooking a charger directly to the battery isn’t recommended, as doing so could damage some other component, like the voltage regulator or alternator” Unquote

Good insight IMO regarding the rest of your post but I seriously doubt that using a battery charger connected to the battery is now a bad thing to do. That is a reasonably anticipated activity; has been since the beginning and it would be reasonable to expect that it will be done sooner or later during the life of a battery.

Beyond that, I am a little irked that our new car has dead power outlets when the car is stopped. I wanted to use them to keep my wife cool on hot summer days with a small 0.6 amp 12 volt fan to keep her comfortable if she chooses to wait in the car while I do a quick errand.

It is entirely possible that vehicles have a variety of parasitic battery drain values when the vehicle is parked so some batteries will go flat during storage while others, such as my old VW is good from November to April with no charging and an immediate start in April. If the OP is handy, it is possible to wire a power outlet directly to the battery, fused close to the battery, to make use of the solar charger possible. The typically difficult part is finding a way to safely route the wiring (use a grommet) through the firewall. The solar charger current output is naturally limited by its size and so the voltage will be regulated by the battery. 16 volts open circuit will be brought down to a normal level by the battery charging load. I have found that in one instance, a vehicle alternator is pushing two amps through the battery under a steady state condition so a half amp or so from a solar charger should not be a problem.