Connecting A Solar Panel Directly To A Car Battery | Will It Damage The Battery?
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- Опубліковано 29 чер 2024
- 7.5 Watt Solar Battery Trickle Charger: amzn.to/3SarpPK
1.8 Watt Solar Battery Trickle Charger: amzn.to/3vUZb4p
Do you have a car, lawnmower, 4-wheeler, dump trailer, or any other application where you have a battery that sits for long periods and always goes dead just when you need it? A Simple $20-$30 solar trickle charger might be a way to avoid these inevitable headaches. I will test out a 7-watt panel to see if this will actually work without the need for a charge controller between the panel and the battery.
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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)
Nice, thanks for the feedback and that is a perfect example of where these small units are handy 👍
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!
Thanks for the feedback James. Good point on the windows. That 7 Watt would probably max out around 4-5 Watts behind the windshield.
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.
Thanks for the feedback 👍
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?
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!!!!)
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 👍
Why not use a small charge controller just to be safe? The are dirt cheap.
you are best . thank you
You bet!
To maintain a 36 or 48 volt golfcart battery bank you will need a boost converter. About $35.00.
or get 3 to 4 pannels and wire them in series 😄
I do this on My Bunkhouse Battery Bank with a RENOGY 10amp panel
Nice, thanks for the feedback!
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?
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.
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
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?
@@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
@@junkerzn7312 oh no I am speaking of a lead acid battery. I agree with you on the unregulated lithium charging being a no go.
@@TheFreak111 Ah, lead-acid is definitely easier to to charge unregulated with. Though I personally would still use a charger controller.
I have to disagree with you on this one. Few hours of testing is not enough, you need to wait over a longer testing period and see what happens when the battery is full, and it is full sun
Wouldnt the battery overcharge without a controller?
Make sure it has reverse current protection otherwise you'll drain the battery when the sun goes down.
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.
Agreed, I used the second panel as this video and left it overnight and for days and it drained the battery at night!
Diode. Costs 1 dollar. Thats all you need
@@davidstevens7809 or they could build it in for $.30 more and charge you an extra $.50 😁
Car cover with integrated solar battery charger 😛
Next level 🤯
That does not look like a Cybertruck 🤔
Hahaha, exactly on the other end of the spectrum to the Cybertruck. Hopefully be switching over soon 🤞
My energy monitor lasted 4 tries and died.
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.
Burnt Hair?...lol
😂