Connecting A Solar Panel Directly To A Car Battery | Will It Damage The Battery?

[@everydaysolar]

7.5 Watt Solar Battery Trickle Charger: geni.us/8bDp 1.8 Watt Solar Battery Trickle Charger: geni.us/66BpM DISCLAIMER: This video and description contain affiliate links, which means that if you click on one of the product links, I’ll receive a small commission.

[@What1zTyme]

Using 1.5 watt panel, south facing, central KY, inside '98 Toyota RAV, connected to battery for 3 years. Drive car short distances once every 7-10 days. Diehard battery 3 years old was deemed healthy last service check. Initially installed to offset vampire drainage from clock. Car starts right up each time, strong cranking, even during recent cold spell (10° F)

[@everydaysolar]

Nice, thanks for the feedback and that is a perfect example of where these small units are handy 👍

[@Bowhunters6go8xz6x]

I bought a solar panel with car battery charger built in for about $20 a couple years ago and it will keep a car battery charged. I agree its not something you want to leave connected forever but I use one over the winter on a vehicle left outside and it works fine and keeps its battery fully charged providing I keep the leaves and stuff cleaned off the solar panel area of the windshield.

[@everydaysolar]

Thanks for the feedback 👍

[@jamesalles139]

I agree, no controller. particularly if there is a normal parasitic load, like a vehicle. And it depends on the climate. If it is a small tractor or dump trailer out in the AZ desert for a long period of time (months) I would err on the side of safety and add a cheap PWM inline. But if you are getting only 4-5 hours of direct sunlight a day, and there are clocks and ECUs, it will be a good ebb & flow. Do note that car windows are treated to reduce energy entering, so there will be a significant drop in performance inside the car. A charged battery is a happy battery!

[@everydaysolar]

Thanks for the feedback James. Good point on the windows. That 7 Watt would probably max out around 4-5 Watts behind the windshield.

[@asificam1]

On an amorphous panel like these, that window treatment wont make any different, least of all one that can be measured. Reason is they already make their max power in low light... but they make that same power in direct sunlight... so they have a slight bottleneck inside the cells. This is the trade off made so that they will actually generate something on very cloudy days... but the higher vampire resistance comes with a higher internal resistance which limits max current. Think of it like a series and parallel resistor that are series and parallel to the cells in the panel... higher parallel resistance is better, infinite would be ideal since then there would be no parasitic losses, and all electrons that get excited by light would be used to power the load. Lower series resistance is better since that means more current to the load... problem is they tend to be related to each other... hence the calculator type solar cells have VERY low power, but they can make some power even under really terrible conditions. Hence why this panel is so HUGE to make so little power. It'll get like 75% of its max power in the shade if its anything like the two I have. However, a more efficient technology like mono crystalline panels will make MUCH more power per unit area than these will... but they will lose a lot of that behind a windshield because they max out under blazing sun not under clouds.

[@MaxUgly]

​@@asificam1well said, thank you for making this clear!

[@asificam1]

@@MaxUgly As least it didn't make a difference for my panel. Made a super small difference for another panel (but only in low light, in direct light the panel was at max power). And keep in mind that the panel may not make max power if the battery is mostly charged... or the extra power will just go to splitting the water in the battery. Best way to know is to measure the current and see if it's satisfactory. Lots of factors impact performance, not worth worrying about if there is sufficient current for your application. But these are low current panels that are basically larger versions of what's in a calculator.

[@junkerzn7312]

At roughly 4:50 you saw an open-circuit voltage of 20V. 20V is probably way too high for a 12V battery. If the battery is full and stops pulling current, the voltage can conceivably rise to 20V. A second test you can perform, then, is to completely charge the battery and then connect up the panel to the battery, in full sun, and see what the voltage is... see if the battery's internal losses are sufficient to keep the voltage in check. In reality, a lead-acid battery might start pulling current at higher voltages when full anyway, possibly limiting the solar panel's voltage under these circumstances. So it could still be safe. And you can also see the danger in making assumptions regarding panels... someone deciding they want more power and connects up, say, a 100W panel, could see a very different result if the battery's internal losses are unable to compensate for that much wattage when full. Boom. Battery starts to boil. But as an electrical engineer I'll tell ya straight-out... without a charge controller, the solar panel MUST have a zener diode built-in to it to actually be a safe trickle-charger for a battery. A ZENER + NORMAL DIODE. No zener diode == not safe. No exceptions. The output voltage has to be regulated in some manner. So what kind of zener would be needed? It has to be beefy, so call it 50W. The voltage selection is minimal... basically 13.0V or 14.0V. So call it 50W @ 13V. And include a heat sink if need-be. That's probably good up to around a 15W solar panel, more with a good heat sink. The zener would go across the solar panel's + and - in the reverse direction for a diode (it works using reverse breakdown current, so the zener diode has to be reverse biased). Generally that means that stripe side is facing the "+" terminal. But test it. One direction will short the panel, the other direction will just limit the voltage. But you still need one more diode because you don't want the zener to short out the battery! That would be bad. In addition to the zener diode, there needs to be a forward diode so the zener doesn't short out the battery. A schottky diode is usually sufficient for that. The solar + zener arrangement, then the positive goes through the normal diode to the battery so the battery cannot discharge through the panel/zener arrangement. Since there is a voltage drop across the normal diode or the schottky diode, you might want to select a zener voltage of 14.0V instead of 13.0V. This forward diode might need a heat sink too but for a small panel... probably not. a 10A or 20A diode would be sufficient (those can dissipate roughly 4A without a heat sink). The forward diode goes from the panel+zener arrangement to the battery positive, with the stripe side facing the battery (forward biased). -Matt

[@TheFreak111]

What do you think about 5.5V 0.33W tiny panels in 3S2P arrangement, plus a 3W orange LED (+/-2V drop) in series with that. So making a 16.5V 2W solar panel plus a 2Vish drop by LED. LED drops less at low current, drops more at higher current, so balancing it a bit. Would that be ok for direct drive trickle charge?

[@junkerzn7312]

@@TheFreak111 Generally speaking I don't think unregulated charging of any lithium battery is a good idea. For very low-power charging (using small 5V panels), you could put a Zener diode of the desired voltage (roughly 14.0V) in series with a 1 ohm resistor and put that across the + and - to regulate the voltage. The zener has to be beefy enough to sink any excess power. Google up how zener diodes work. That said, honestly, I'd spend the small amount of money required to get even the cheapest possible PWM charge controller. They're like $20. A good cheap MPPT charge controller is more around $60-ish (A Victron SmartSolar 75/15). -Matt

[@TheFreak111]

@@junkerzn7312 oh no I am speaking of a lead acid battery. I agree with you on the unregulated lithium charging being a no go.

[@junkerzn7312]

@@TheFreak111 Ah, lead-acid is definitely easier to to charge unregulated with. Though I personally would still use a charger controller.

[@Ulbre]

This is a great idea and from the comments, already in use by quite a few. It's probably even a good idea for a daily commuter who parks the ride up at the train station or at work for most of the day (sorry night shift workers...this won't work for you!!!!)

[@everydaysolar]

Yeah, overall most of the reviews on these type of solar trickle charges are pretty solid. For the specific use of keeping the battery topped off when a vehicle sits for a long time I would say it works great 👍

[@DaveInBridport]

My concerns are 1. Overcharge. 2. At night, current flow will reverse causing discharge.

[@miansahib9590]

Sub 1 amp from 7 watt panel could 4 of those deliver 2 amps in Chicago

[@bertjesklotepino]

ok, so i bought this automatic light that turns on when it sees motion. And obviously only when its dark. It also came with a solar panel and a 6 volt battery. The light is a grid of leds, basically. From the LIDL. The solar panel puts out 12 volt in full sunlight. Perhaps a bit more, but around 12 volts. Inside the lamp is a circuit to charge the battery via solar panel. But you can also hook up an adapter to power the light. (and perhaps charge the battery. I am no wizzkid so i dont know if the circuit also charges the battery if you hook up the adapter but i assume it does) Anyways, the question is simple: Can i just hook up this simple small solar panel that puts out 12 volts to my car battery to keep it charged? Or does it require a small circuit in between? I have no clue how many watts this solar panel puts out. I am not an electrician, so hence this question. Thx in advance for any reply.

[@dans.5608]

I found this video just after I spoke with Renogy, specifically about the Wanderer 10. They advised me that none of their products are made for use with a standard automotive battery. They should be used only with deep cycle batteries. So, my search continues for a solar charge. Controller to use on an automotive battery.

[@MaxUgly]

They may just be saying that so you can't try to put it on them if you run down a normal car battery and degrade it. Don't take my word, though. I'd ask on some subreddits or eet forums or something. Get a few smarter opinions and maybe a recommendation for a product. Good luck!

[@emil.honganmaki5461]

When the panel is only a few watts of power..you don't need a regulator..the regulator taxes the power for nothing,

[@geofftubeyou]

Great video. Thank you

[@alansach8437]

Why not use a small charge controller just to be safe? The are dirt cheap.

[@asificam1]

Would lose most of your power to the controller, these panels make almost nothing, they're designed to have a low current so that they are not at a level where a battery would take damage from being connected 24/7. AGM cells for instance would be able to recombine the minuscule amount of water a panel like this would cause the battery to electrolyze into Hydrogen and Oxygen faster than the panel would be able to power the electrolysis, a flooded cell that is not connected to a load like a parasitic draw in a car may need to have water added like once a decade to replace the infinitesimally small overcharge (assuming no self discharge or parasitic loads so all panel power goes to overcharge). Lead acid cells can tolerate being connected to a very low charge current for long periods with minimal wear, literally just add water once in a while... or just forget it for AGM and Gel since they would be able to recombine the electrolysis gases faster than they are being produced... a controller would probably make the tiny 0.1 to 0.25 amp charge into a 0.001 amp charge because it would need some current to power itself and the panel voltage drops FAST with any sort of load. I tried to make an MPPT controller to just get to the maximum power point (not really to charge anything, that was for later) and was unable to make it worth powering the very efficient micro-controller chip.

[@ilcaips]

does anyone know if i can connect the - of the solar panel only on the - of the battery or i can also connect it to ground/mass?

[@TheFreak111]

In my car at least, - of battery is directly connected to ground/mass. So it should make no difference where you connect - of solar panel. May be different for some cars idk.

[@curtw8827]

To maintain a 36 or 48 volt golfcart battery bank you will need a boost converter. About $35.00.

[@Brandon-uy1uv]

or get 3 to 4 pannels and wire them in series 😄

[@asificam1]

Boost converter would consume too much of the current at these low currents... you'd be losing like 75% to 99.99% of your solar power in the converter if my best case tests are anything to go by, raising voltages is harder and harder to do efficiently as the voltage difference is greater, even trying to raise by 1 volt was pointless for a panel like this. Either use some hacky solution that floats the panel from battery to battery or uses capacitors like those LiPO balancer boards do, or just wire some of these in series or wire one to each battery...

[@curtw8827]

@@asificam1 when my 100 watt (rated) solar panel is delivering 80 watts to my boost converter I'm getting 72 watts into my 36 volt battery bank in the golf cart. Much better than your low efficiency claim.

[@jamescmarch]

I was cautioned to disconnect the solar panel when driving the car. Not sure what the reasoning was, but the panel could be damaged by the car generator power? My current need is to keep my Prius battery ready, since all the electronics in the Prius will drain the battery in 3 weeks if not driven! I've had to jump-start it twice at the airport after long trips 😞 Did you learn anything about what happens when the battery is fully charged and still connected to the solar panel? Any updated recommendations? Add the diode? Other?

[@1111boggy]

you are best . thank you

[@everydaysolar]

You bet!

[@1GREATDANE]

I do this on My Bunkhouse Battery Bank with a RENOGY 10amp panel

[@everydaysolar]

Nice, thanks for the feedback!

[@rcguymike]

Make sure it has reverse current protection otherwise you'll drain the battery when the sun goes down.

[@curtw8827]

Yes, this video is poor information, even a $0.99 solar yard light from Walmart has a series diode and charge controller to keep the solar panel from draining the battery when dark.

[@markberning9142]

Agreed, I used the second panel as this video and left it overnight and for days and it drained the battery at night!

[@davidstevens7809]

Diode. Costs 1 dollar. Thats all you need

[@rcguymike]

@@davidstevens7809 or they could build it in for $.30 more and charge you an extra $.50 😁

[@Pallidus_Rider]

Car cover with integrated solar battery charger 😛

[@everydaysolar]

Next level 🤯

[@bluemonster1877]

those 1.5 solorpanels are worthless and those 7 watt are the same

[@str8sr825]

The cigarette lighter on your dash will stay on the other 2 do not.

[@jameshigginbotham3639]

Burnt Hair?...lol

[@everydaysolar]

😂

[@TheKingOfInappropriateComments]

That does not look like a Cybertruck 🤔

[@everydaysolar]

Hahaha, exactly on the other end of the spectrum to the Cybertruck. Hopefully be switching over soon 🤞

[@2hotscottpro]

My energy monitor lasted 4 tries and died.

[@everydaysolar]

Don't let the smoke out 😂. I haven't killed any in a while but at the start smoked 2 units. Make sure the load is plugged in prior to connecting the panels.