Those solar cell car battery maintainer devices ... look like they would be a good idea to use when you have a car parked without being driven for several weeks at a time ... is there any chance that those devices could cause any damage to a car battery? Or are they weak enough that it is nothing to be concerned about? And the other question is, do they actually help keep a battery charged? Looks like they plug into the cigarette lighter plug but not sure how that can charge the battery?
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Re: About Solar Chargers...
Some of the higher-end solar chargers claim to have "intelligent" charge circuitry so they should at least in theory work just like a plug-in "smart" charger and stop charging once the target voltage is reached. The cheaper ones don't claim this and are likely just a constant "float" charge with no intelligence, though since most of these chargers are 10W or less this isn't likely to be an issue on the average 50-60 Ah car battery, smaller batteries (like motorcycle or power equipment) may have issues with this though.
The Cigarette lighter chargers will only work if the lighter jack is always "hot" (even with the ignition off), and even then I'm not sure how well they'd work with modern can-bus equipped vehicles. If the lighter jacks in the vehicle aren't "hot" with the ignition off (or if back feeding the lighter doesn't play "nice" with the can-bus) the charger would need to be wired directly to the battery.
On my Mustang which doesn't get driven much in the winter I have an SAE quick disconnect (similar to this one: https://www.amazon.com/Battery-Tende...ps%2C55&sr=8-3) wired into the battery (I just use a plug-in battery maintainer since it is parked in a garage with plenty of electric outlets) which will work with most battery maintainers (both plug-in and solar) and allows quick connection without messing with alligator clips and risking shorts.
Last edited by dmill89; 12-21-2021, 10:53 PM.
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Re: About Solar Chargers...
Originally posted by dmill89 View PostSome of the higher-end solar chargers claim to have "intelligent" charge circuitry so they should at least in theory work just like a plug-in "smart" charger and stop charging once the target voltage is reached. The cheaper ones don't claim this and are likely just a constant "float" charge with no intelligence, though since most of these chargers are 10W or less this isn't likely to be an issue on the average 50-60 Ah car battery, smaller batteries (like motorcycle or power equipment) may have issues with this though.
The Cigarette lighter chargers will only work if the lighter jack is always "hot" (even with the ignition off), and even then I'm not sure how well they'd work with modern can-bus equipped vehicles. If the lighter jacks in the vehicle aren't "hot" with the ignition off (or if back feeding the lighter doesn't play "nice" with the can-bus) the charger would need to be wired directly to the battery.
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Re: About Solar Chargers...
Definitely depends on the size of the battery versus wattage of the panel, but I'd say that a "dumb" 10W into a 50Ah battery you will need to water the battery and it could eventually cause damage if you never use the battery. At 10W it's about C/60, which is not horrible but still will cause eventual dry out. If it were a sealed AGM battery with proper recombination, then you won't have to worry about electrolyte loss.
Ideally you don't go way too much over about 3x the parasitic draw of the battery (for most cars it's 1W or so tops) if you can't regulate the voltage. But a simple shunt or series regulator will be sufficient to deal with water loss, but do keep in mind it's temperature dependent.
oh btw, a $0 way to maintain your battery if you don't care about ECU settings and less than say 3 months of non-use: just disconnect the battery. If it discharges without it being connected, you need a new battery anyway...Last edited by eccerr0r; 12-21-2021, 11:05 PM.
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Re: About Solar Chargers...
Originally posted by eccerr0r View PostDefinitely depends on the size of the battery versus wattage of the panel, but I'd say that a "dumb" 10W into a 50Ah battery you will need to water the battery and it could eventually cause damage if you never use the battery. At 10W it's about C/60, which is not horrible but still will cause eventual dry out. If it were a sealed AGM battery with proper recombination, then you won't have to worry about electrolyte loss.
Ideally you don't go way too much over about 3x the parasitic draw of the battery (for most cars it's 1W or so tops) if you can't regulate the voltage. But a simple shunt or series regulator will be sufficient to deal with water loss, but do keep in mind it's temperature dependent.
oh btw, a $0 way to maintain your battery if you don't care about ECU settings and less than say 3 months of non-use: just disconnect the battery. If it discharges without it being connected, you need a new battery anyway...
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Re: About Solar Chargers...
Originally posted by eccerr0r View PostDefinitely depends on the size of the battery versus wattage of the panel, but I'd say that a "dumb" 10W into a 50Ah battery you will need to water the battery and it could eventually cause damage if you never use the battery. At 10W it's about C/60, which is not horrible but still will cause eventual dry out. If it were a sealed AGM battery with proper recombination, then you won't have to worry about electrolyte loss.
Ideally you don't go way too much over about 3x the parasitic draw of the battery (for most cars it's 1W or so tops) if you can't regulate the voltage. But a simple shunt or series regulator will be sufficient to deal with water loss, but do keep in mind it's temperature dependent.
oh btw, a $0 way to maintain your battery if you don't care about ECU settings and less than say 3 months of non-use: just disconnect the battery. If it discharges without it being connected, you need a new battery anyway...
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Re: About Solar Chargers...
A car battery wastes about 4mA just sitting there, due to impurities in the electrolyte. Solar chargers can use many mA as well. The car draws up to 100mA average for the remote RX, canister purge cycle and all that stuff the ECU does when the key is off.
Lots of outrage over Subaru ECU's pigging out and killing a battery in a couple weeks or less.
If you only can charge a few hours per sunny day, you'll find you need a fair bit of power to make up for all this load.
I''m using a mains-powered charge maintainer, it puts out about 14.6V 2A for a top up (equalization) charge then shifts down to float charge 13.8V at a few hundred mA, overnight down to 100mA.
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Re: About Solar Chargers...
Originally posted by dmill89 View PostSome of the higher-end solar chargers claim to have "intelligent" charge circuitry so they should at least in theory work just like a plug-in "smart" charger and stop charging once the target voltage is reached. The cheaper ones don't claim this and are likely just a constant "float" charge with no intelligence, though since most of these chargers are 10W or less this isn't likely to be an issue on the average 50-60 Ah car battery, smaller batteries (like motorcycle or power equipment) may have issues with this though.
The Cigarette lighter chargers will only work if the lighter jack is always "hot" (even with the ignition off), and even then I'm not sure how well they'd work with modern can-bus equipped vehicles. If the lighter jacks in the vehicle aren't "hot" with the ignition off (or if back feeding the lighter doesn't play "nice" with the can-bus) the charger would need to be wired directly to the battery.
On my Mustang which doesn't get driven much in the winter I have an SAE quick disconnect (similar to this one: https://www.amazon.com/Battery-Tende...ps%2C55&sr=8-3) wired into the battery (I just use a plug-in battery maintainer since it is parked in a garage with plenty of electric outlets) which will work with most battery maintainers (both plug-in and solar) and allows quick connection without messing with alligator clips and risking shorts.
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Re: About Solar Chargers...
Originally posted by redwire View PostA car battery wastes about 4mA just sitting there, due to impurities in the electrolyte. Solar chargers can use many mA as well. The car draws up to 100mA average for the remote RX, canister purge cycle and all that stuff the ECU does when the key is off.
Lots of outrage over Subaru ECU's pigging out and killing a battery in a couple weeks or less.
If you only can charge a few hours per sunny day, you'll find you need a fair bit of power to make up for all this load.
I''m using a mains-powered charge maintainer, it puts out about 14.6V 2A for a top up (equalization) charge then shifts down to float charge 13.8V at a few hundred mA, overnight down to 100mA.
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Re: About Solar Chargers...
Check out this gizmo ... only $18 and it looks like it will make sure the battery stays properly charged...
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Re: About Solar Chargers...
Do not count on indirect sunlight. Must be in full sun.
Sigh. Need to get started on my grid tie project for my solar panels - but that's where I found that indirect and cloud occluded light is almost useless light... Cirrus clouds also do a huge number on productivity too... In this case you may well need to overbuy solar cells to make up for the poor lighting.
Oh and another benefit of disconnecting batteries: it bewilders and/or annoys thieves, especially if you do it in a way such that they need to bring something else to the table to start the car...Last edited by eccerr0r; 12-22-2021, 02:35 AM.
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Re: About Solar Chargers...
Originally posted by EasyGoing1 View PostSadly, my 350z has to be parked in an outdoor covered parking stall at this apartment complex. Access to power is not an option but a disconnect seems like it might help ... though i would think the battery would still drain over time just perhaps not as quickly..?
Originally posted by eccerr0r View PostDo not count on indirect sunlight. Must be in full sun.
This was not a particularly expensive setup (specifically it is this: https://www.amazon.com/dp/B0956QFKVY...roduct_details), though probably still a little higher quality panel than the average "suction cup to the roof" or "throw on the dash" charger.
Originally posted by EasyGoing1 View PostCheck out this gizmo ... only $18 and it looks like it will make sure the battery stays properly charged...Last edited by dmill89; 12-22-2021, 09:33 AM.
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Re: About Solar Chargers...
Originally posted by eccerr0r View PostOh and another benefit of disconnecting batteries: it bewilders and/or annoys thieves, especially if you do it in a way such that they need to bring something else to the table to start the car...
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Re: About Solar Chargers...
Originally posted by dmill89 View PostIt depends on how good the panel is (which granted a cheap solar charger probably isn't going to have a great panel), I don't charge any car batteries with solar chargers, but I do have a solar system in my shed for lighting consisting of a 20w panel, a 12ah 12v lead-acid battery, and a charge controller, and this panel will still produce around 30-50% of its rated wattage on a cloudy day.
I'm wondering if there would be something I need to do so that when I'm using the car, would there be anything that should be done to protect the charging circuit? Because while the car is running, the alternator would be feeding voltage into the outputs of that charge monitor unit.Last edited by EasyGoing1; 12-22-2021, 11:53 AM.
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Re: About Solar Chargers...
Originally posted by eccerr0r View PostDo you have direct sunlight for a good portion of the day? Shadows of any kind really kills cell performance. Clouds are not as bad as buildings occluding sunlight even if it "seems" just as bright.Last edited by EasyGoing1; 12-22-2021, 12:16 PM.
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Re: About Solar Chargers...
I was thinking of using something like this and connect it to a wire that is energized when the ignition is turned on so that it would disconnect the charger while the car is running.
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Re: About Solar Chargers...
Originally posted by dmill89 View PostIt depends on how good the panel is (which granted a cheap solar charger probably isn't going to have a great panel), I don't charge any car batteries with solar chargers, but I do have a solar system in my shed for lighting consisting of a 20w panel, a 12ah 12v lead-acid battery, and a charge controller, and this panel will still produce around 30-50% of its rated wattage on a cloudy day.
So Im going to connect the solar panel to the SC ports, and the battery, I'm going to connect to the center ports but I'm going to connect the hot lead through a normally closed relay where the relay is actuated when the ignition key is in the on position. This should guarantee that the system is not connected when the alternator is running. And that last set of ports I'm going to just remove those wires since I wont be using them for any lighting of any kind... does that resonate with how you have yours hooked up in terms of properly identifying the ports?
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