Charge car battery with solar cell

Hey guys. Thought I would ask some of you guys here who are smarter than me a question.

I live in an apartment with a parking garage so I dont have access to power outlets. I have 2 vehicles and I decided to park the Accord for the winter and drive the AWD Acura RDX in the snow. The Accord is just sitting and the battery is getting weak. The question is, if I buy a battery tender and a solar panel will the flouresent lights in the parking garage be enough to keep the battery from dying? Or is there some other way to periodically top off the battery without having to constantly take it out and bring it to my room to charge it?

If it were me, I would just bring it up, charge it, and return it to your car. Once in your car simply hook up only the positive terminal and leave the negative off. Should be good to go in the spring by just attaching the negative terminal and off you go.

The problem is — Even with a 12v solar panel designed to tend a battery — the car parasitic drain is probably more than what the solar provides —— I had a 94 chevy PU and in direct sunlight it wouldn’t keep up the battery —— Either get a battery jump charger or just take the battery out and charge it for when you need it —If anything just disconnect one post and it will last longer that way

Get one of these —- I have one and it starts a Big V8 easily

That answered my question perfectly. If the sun can’t do it there’s no way these dinky flouresent lights will be able to. Thanks!

No “convenience outlets” in the garage?

I gotta park curbside, so I hook up my “battery tender” directly to the battery, run a 50’ extension cord (big-ass outdoor-rated orange ones), feed the cord up between radiator and grille or just behind the radiator, then connect the tender to that.

I have just enough clearance between the hood and crossbeam that the cord fits but not the head, so if some jackass tries to be funny by yanking on it, he won’t pull the whole mess outta there. I don’t even bother to unfurl the power cord on the tender and leave the wire-tie on it. And I can keep the hood closed/locked the entire time, even overnight. (I’ll sleep on the couch just in case I’d hear anything outside, though.)

Scope it out first and see how you’d route everything.

Then if you can get to an outlet, just plug it in and babysit it a few hours while reading or whatever. Lots will crank out 10A, so if you’re just topping up, just a few hours should be necessary.

Funny story — I had my Nocco battery tender on my old truck— i decide to go take a ride in it —I forget all about unplugging it , not to mention maybe wires were in the fan some how — About the time I noticed the extension cord tightening up it unplugged from the truck — All was OK ( for a change)

Idle your stored car for 10 minutes once a month.

You’d be surprised that doesn’t work — before I put a tender on my old truck I’d do that —then every once in a while I’d drive it to town ( about 4 miles ) —lots of times I’d go to leave the store etc it wouldn’t start back up —something about I wasn’t running it long enough to charge the battery for what the truck was using

I’m going to generalize a little bit here. Some alternators don’t put out a lot of power at idle. You might need 5 minutes of running the engine just to put back the power that you use to crank the vehicle over to start it. So with a relatively new battery in good shape, 10 minutes of running every month might get you through 3 months of winter with some vehicles. 15 minutes of driving would be better. Some vehicles aren’t going to go a month with the battery connected. Disconnect the negative cable terminal. Test the voltage before you reconnect and start it up every time to see how low you are getting and modify your procedure based on the results. If you get down below 12.2 you have to do more to keep it up.

I think your best bet would be to either bring the battery inside for the winter, or make sure it’s topped off and disconnect the battery negative until you want to drive it again. Idling a few minutes every few days will probably do more harm than good, if you’re going to start it you should actually drive it for a little while.

A sitting lead+sulfuric acid battery will suffer a daily voltage drop of 1 to 5% depending upon temperature, grid material, age, parasitic drain, etc.

These factors are technically examined and explained in an easy to read paper here:
Daily loss factors

This site has a chart to give expected days-till-empty due to parasitic drain from the car’s electronics:
loss chart site

If you are in a cold climate then i would recommend to just remove the battery and keep it fully charged all the time on a trickle charger at 12.8 to 13.8 max holding voltage. Lead sulfate will plate out onto the electrodes and can cause permanent damage in less than a week if the battery is not kept fully charged.

Be sure to inspect, check and verify the holding voltage that it is not too high or too low. i have tested about a dozen different trickle chargers (the little cheap ones from various vendors) and dismantled them to examine the circuits and controllers. There was a wide range of inadequate holding voltages and one even caused the battery to boil out the acid as its circuit was holding at 15.56VDC due to an improper smd resistor value. Most folks wouldn’t be able to change these out to make the correction.

Then i started testing higher priced versions (if you pay more then it has to be better—right?) and found similar variation in the holding voltages. But the best test results were from a Yuasa 1A Smart Charger sold in motorcycle shops. It will fully charge at 14.4 to desulfate the plates, then back off the voltage to hold at 12.8VDC; it takes a day or two to charge a car battery and won’t revive one that is dead or totally depleted. i tested several others but was not impressed by performance or circuit details, e.g. the so-called “battery tender”. This is not an ad or review, just my results from testing and reverse engineering circuit boards, ymmv.

You need to drive it once a month for about 10 mins to get the battery charged back up.

This is from a garage blog on car storage.

8. Disconnect your car battery or use a trickle charger

Unless you’re planning on occasionally starting your stored car during the winter, it’s a good idea to remove the vehicle’s battery. If a car battery loses its charge it may freeze, at which point it becomes useless.

Store it in your heated living space and the battery should be good to go when it’s hooked back up in the spring. Be aware that battery removal isn’t recommended if the car being stored is newer and has engine computers.

Your other option is to hook your car battery up to a trickle charger or battery maintainer. Ensure the model you purchase has an auto shut-off feature to prevent overcharging. As an added dose of preventative maintenance, you can also coat the battery terminals with petroleum jelly.
9. Occasionally start your car…or not

One long-running debate concerning winter car storage is whether or not you should start it every few weeks. Those who don’t think this is necessary believe that if you’ve taken the proper steps to store your car properly, there’s no need to run it during the winter.

There seems to be a more widely-held belief, however, that it is a good idea to start your stored car every 3-4 weeks. Those in favor believe this keeps the cylinders lubricated and removes moisture from operating components. If you’re able to move your car (even just back and forth a few feet), this also prevents brakes and clutches from sticking.

If you do decide to start your vehicle during winter car storage, just remember to do these four things:

always remove your car cover when it’s running
remember to remove (and put back) anything you were using to keep critters out of your car
run your car for about 10-15 minutes until it reaches its optimal operating temperature
leave your garage door open while your car is running

For the rest Winter Car Storage: 11 Tips to Help Preserve Your Prized Ride

Sell it ——- LOL

Naw, doesn’t work, especially once the engine goes closed-loop and down to a slow idle. Alternators don’t put out much current at idle.

Better to just take it for a spin, preferably a long easy highway trip. Works the engine, boils off any accumulated moisture once it’s up to temp, keeps everything lubed, even works the suspension to keep things flexible.

I once had my car croke on me, jumped it, let it run (all accs off, even the radio) for about 2hrs, being that I knew the battery was so low. Dead again the next day! Didn’t charge much if at all.

Different time, similar sitch, dead from standing too long, jumped it, took it to go food-shopping, maybe 5min away, bringing my jumper with me. Came back, half expecting to have to jump it again just to go home, but it started right up.

Also, a quick back’n’forth on the highway works well.

the lights will not be enough

idling prob will not work either

you do need a ‘battery tender’ thingy

or = maybe = one of those li ion jumper starter things

you could plug into a 12v socket and charge it backwards through the lighter port

will that work, anyone?

[socket has to work without ignition key though]

then you could take that in and out of the house to charge from AC

LESS THAN 1A, you can charge it 24/7 through the always-live OBD port.

Lots of lighter-sockets cut out after, eg, 10min of the car being turned off.

Make sure the solar panel has its own blocking diode so your car doesn’t try to back-feed the panel.