Solar panels and battery maintenance
Discussion
Two things.
1 . Due to where I park my car there is no electric socket/power source near by
2. Sometimes I am abroad for months at a time
I want to maintain my battery. In an older car I would disconnect the positive or simply bring it indoors and connect it to a battery tender.
The car has a tracker and dash cam. The dash cam timer is set to 48 hours.
I want to keep the battery topped up in some way so that I can unlock the car upon my return and drive off without having to try a jump start. I even purchased a jump starter (rechargeable one) but it was no use as the battery was so low the doors kept unlocking and locking.
Would a solar panel cut it?
What kind of ratings (wattage) should I look at? 12v 6w?
Should I opt for a more powerful one with a voltage cut off to avoid overcharging? Do such fancy regulators exist?
My thinking is that the 6w variant will be enough to provide the trickle required for the electrics. It would be enough in the daylight and evening wouldn’t make a difference.
If all I need is a solar panel then it would be an investment.
Thank you
1 . Due to where I park my car there is no electric socket/power source near by
2. Sometimes I am abroad for months at a time
I want to maintain my battery. In an older car I would disconnect the positive or simply bring it indoors and connect it to a battery tender.
The car has a tracker and dash cam. The dash cam timer is set to 48 hours.
I want to keep the battery topped up in some way so that I can unlock the car upon my return and drive off without having to try a jump start. I even purchased a jump starter (rechargeable one) but it was no use as the battery was so low the doors kept unlocking and locking.
Would a solar panel cut it?
What kind of ratings (wattage) should I look at? 12v 6w?
Should I opt for a more powerful one with a voltage cut off to avoid overcharging? Do such fancy regulators exist?
My thinking is that the 6w variant will be enough to provide the trickle required for the electrics. It would be enough in the daylight and evening wouldn’t make a difference.
If all I need is a solar panel then it would be an investment.
Thank you
Buy a panel around 40w - this will fit on your dash/rear deck. Then use an MPPT solar regulator - this will charge your batter, and provide a top-up/conditioning charge - i.e. keeps your battery tip top and doesn't overcharge it. MPPT tech gives you a minimum 20% more power form the same panel.
40w is around the sweet spot for size. The MPPT regulator connects between the panel and the battery.
Lots of "fake" MPPT regulators on ebay.
This is not:
https://www.ebay.co.uk/itm/EPEVER-Tracer-MPPT-12-2...
Most regulators under £50 are not really MPPT. Be aware.
40w is around the sweet spot for size. The MPPT regulator connects between the panel and the battery.
Lots of "fake" MPPT regulators on ebay.
This is not:
https://www.ebay.co.uk/itm/EPEVER-Tracer-MPPT-12-2...
Most regulators under £50 are not really MPPT. Be aware.
Thank you everyone for your input. My bad. I should checked back here rather than creating another thread (apologies admin).
I went for a 40w set up. The kit comes with two 20w panels so I can play around and see if I need the extra panel. The panels are thin and one would fit the rear deck. I wanted a fit and forget type solution so the regulator I purchased has an automatic cut off with engine on.
Current draw is around 370 mA (not 250) for the 2 channel dash cam. The tracker and alarm draw 230 mA. A 20w panel should be able to cope with the loss and add a little back to the battery. I don’t want to put too much back in one go. Apparently high wattage charging approaching a full charge is not good for the battery.
I have some MC4 connectors and will make it a clean and safe set up.
I have decided to buy a more expensive regulator. The cheap one I had read 11.8v and an analogue meter read 12.2v. I don’t want to undercharge.
See how she goes!
Appreciate all your thoughts.
I went for a 40w set up. The kit comes with two 20w panels so I can play around and see if I need the extra panel. The panels are thin and one would fit the rear deck. I wanted a fit and forget type solution so the regulator I purchased has an automatic cut off with engine on.
Current draw is around 370 mA (not 250) for the 2 channel dash cam. The tracker and alarm draw 230 mA. A 20w panel should be able to cope with the loss and add a little back to the battery. I don’t want to put too much back in one go. Apparently high wattage charging approaching a full charge is not good for the battery.
I have some MC4 connectors and will make it a clean and safe set up.
I have decided to buy a more expensive regulator. The cheap one I had read 11.8v and an analogue meter read 12.2v. I don’t want to undercharge.
See how she goes!
Appreciate all your thoughts.
You did the right thing with 20/40w. 6w is paultry and won't even keep up with a lot of car alarms. Bear in mind the 6w is rated in ideal sunny conditions , and not through a car window and not layed flat ( they perform around 25% better when angled directly at the sun). Most of the time you'll be lucky to get 1-2 w average on a parcel shelf / dashboard from a 6 w panel.
Also, wherever you heard "Apparently high wattage charging approaching a full charge is not good for the battery. " is not relevant as any half decent regulator will drop the charge down to a few 100 ma once the battery is full, and this actually prolongs the battery life as it counters natural discharge that lead acid batteries exhibit.
To be totally sure, use a decent regulator, not a £10 one, though they mostly work fine.
Also, wherever you heard "Apparently high wattage charging approaching a full charge is not good for the battery. " is not relevant as any half decent regulator will drop the charge down to a few 100 ma once the battery is full, and this actually prolongs the battery life as it counters natural discharge that lead acid batteries exhibit.
To be totally sure, use a decent regulator, not a £10 one, though they mostly work fine.
Dr Doofenshmirtz said:
Hmm...your combined current draw is 600mA - that's actually quite a lot. Are you sure that's right?
If your car battery is 50Ah (50'000mAh), then / 600mAh = 58 hours run time until the battery is flat.
You'll get 'up to' 3.3 amps charge rate with a 40w panel, but this is only for a couple of hours around midday in summer, on a clear day, with a ~38 degree incline facing directly south. After which the charge rate will drop off considerably.
A flat 50Ah battery will take around 11 hours to fully charge at 3.3 amps continuous.
In a nutshell - your battery will drain after a few days (I predict 4 days) and the solar panel isn't big enough to keep it charged.
A couple of things.If your car battery is 50Ah (50'000mAh), then / 600mAh = 58 hours run time until the battery is flat.
You'll get 'up to' 3.3 amps charge rate with a 40w panel, but this is only for a couple of hours around midday in summer, on a clear day, with a ~38 degree incline facing directly south. After which the charge rate will drop off considerably.
A flat 50Ah battery will take around 11 hours to fully charge at 3.3 amps continuous.
In a nutshell - your battery will drain after a few days (I predict 4 days) and the solar panel isn't big enough to keep it charged.
Edited by anonymous-user on Tuesday 4th September 21:59
You dont get the full rated AH out of a lead acid battery, more like half, as the AH is rated to zero volts, but LA batteries are effectively flat at 10.8v .
a 40W panel will give around 2.4 Amps in good sun, from about 7am until around 6pm in the summer. Not the tight hours you suggest. This is as long as it is facing the sun. Halve that if it is not. Even badly positioned you will get a reasonable charge all day. In the winter this drops drastically.
600ma is not unusual for a tracker, alarm, and dashcam. Most people with trackers need a charging solution for long term parking. My Porsche would not get past 10 days without a 12w panel on the parcel shelf.
40W should happily keep on top of things in the summer, and get by well enough in the winter.
To put things into perspective (I run a solar panel company for campers) an 80w panel in a camper roof, with a 75Ah battery , will run a compressor fridge (4amps draw when on (thermostatic control so depends on where you set the temperature)) indefinitely in an English summer. The battery gets you through the night, and then it is full by around 8-10am. That's a lot of work for an 80w panel, so you can now imagine that a badly placed 40w panel is still going to be impressively helpful.
I'd link my company (with data logs from tests) but I really don't want to be associated with this forum as the general chat and legal sections are pretty nasty places! :-)
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