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Posted: 4/21/2014 8:15:18 AM EDT
I have an old dodge SUV that sits in my front yard (hey...it's Tennessee, and the law states that everyone must have at least one semi-abandon vehicle on display somewhere on their property...
 ) Anyway, I start it up about 4 times a year and drive it around the farm to run over a few groundhogs. This time, when I went to start it..."CLICK-CLICK".... So, in typical ARFCOM fashion, I saw an opportunity for a test. Got the voltmeter and checked the battery...6.85 v. So I had a few of THESE solar trickle chargers laying around.... Got one and hooked it up. One week later, (mix of sun and rain) I took the voltmeter back....11.85 v... Still not enough though....waited another week...(mostly sunny) and again made the pilgrimage with the voltmeter...6.08 volts.... ...so....WTF.....Keep in mind, I am not advocating trying to bring back a 6.85 battery with a 7 watt trickle charger...just seeing IF it would work...but why the rise in the right direction followed by a crash to a lower voltage than when I started?
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Posted: 4/21/2014 8:38:29 AM EDT
[#1]
The plates in lead acid batteries constantly erode as electrons move from plate to plate. When they erode enough so that the accumulated gunk (tech term) in the bottom of the battery touches both positive and negative plates at the same time, the cell shorts out. Sounds like this is probably what happened in this battery. You can take a digital multimeter and measure from the negative post to the electrolyte in each cell looking for around 2 vdc, Getting the answer doesn't help a lot unless they are all consistently low. If so connecting to a real charger may save the battery.
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Posted: 4/21/2014 9:01:33 AM EDT
[#2]
It's toast.
Throw your trickle charger in the trash. Buy a Battery Tender Jr. on Amazon. These are used to sustain a battery that isn't used daily. BatteryMinder makes a good one too. It charges, desulfates, and has models for AGM batteries. It is a bit more money, but it is necessary if you need to charge a battery. I have 5 Battery Tenders and one BatteryMinder. I couldn't give them a higher recommendation. I got 14 years out of a Yellowtop Optima with the Battery Tender. 
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Posted: 4/21/2014 9:27:37 AM EDT
[#3]
Time to layout some dough on a battery. you could place the new one on the dialer driver and take that battery and place it in the mandatory redneck wheels
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Posted: 4/21/2014 10:05:27 AM EDT
[#4]
Quote HistoryQuoted:
It's toast. Throw your trickle charger in the trash. Buy a Battery Tender Jr. on Amazon. These are used to sustain a battery that isn't used daily. BatteryMinder makes a good one too. It charges, desulfates, and has models for AGM batteries. It is a bit more money, but it is necessary if you need to charge a battery. I have 5 Battery Tenders and one BatteryMinder. I couldn't give them a higher recommendation. I got 14 years out of a Yellowtop Optima with the Battery Tender. Wait...are you saying that solar trickle chargers are worthless for helping to keep a battery charged?...not calling you out here...(yet  ) but I'm trying to learn.
AND...I do run a battery tender on some other little used batteries....but the above mentioned dodge is parked (and will stay there...according to the wife) where there is no electricity....so I'm SOL there... |
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Posted: 4/22/2014 5:06:52 PM EDT
[#5]
Flooded cell (automotive type) batteries need more than just a trickle charge to keep them healthy. The "Battery Tender" brand chargers (and others, obviously) are actually battery maintainers, meaning that they have different stages of charging.
Google "3 stage battery charger" for more info. |
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Posted: 4/22/2014 6:01:26 PM EDT
[#6]
I've got a 1 watt $15 solar trickle charger on a 30kw diesel generator. We try to crank it once a month, but we've never had a dead battery since we put the solar trickle on it.
We never let it run dead though. It's basically a maintainer for the charged battery. |
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Posted: 4/22/2014 8:55:32 PM EDT
[#7]
6.85V on a 12V battery = dead forever. When you measured the higher voltage was the solar panel still hooked up and trying to charge the battery? That might explain why you saw a temporary increase in voltage.
If the solar trickle charger is just a panel hooked up directly to a battery, which is what your unit is, its usefulness is questionable. You need a charge controller to control the incoming voltage based on the state of charge of the battery (among other things). I'd just get something like this or this. It'd be easy enough to hook up to your little solar panel. |
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Posted: 4/23/2014 3:57:50 AM EDT
[#8]
I use a solar trickle charger when I go camping, and know I won't be cranking the old 4Runner for a week. Don't want to be way out in the woods, and go to crank and find the battery too low to start the truck. Also use the solar charger when I am down at my Miami place, and leave my truck in the Condo parking garage for more than a week.
I have been doing this for some time now, and have had no issues. |
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Posted: 4/23/2014 6:10:29 AM EDT
[#9]
Just a couple comments.
I lost a battery on a seldom used vehicle trying one of the cigarette plug solar cells. Due to the time, I don't really know what happened. I had to buy a new charger for my boat and bought a new marine smart charger. Impressed, I bought a home model to replace my old 2amp/10amp/50amp. I keep a lot of batteries around. Its saved three I thought were dead and gone so far. Though expensive for boats, the home models are very reasonably priced. $40-$100. They are digital, test batteries, and unlike old school go automatically into maintenance mode once a battery is charged. Like the expensive marine chargers, they react specifically to the voltage so can save a battery otherwise would be lost and have mode settings for the different types of batteries. Mine is a low cost Schumaker but its paid for its self ten times over already. Though its not a Battery Tender which I have those too. I really like the idea that I don't have to watch the clock and worry about overcharging. It has a fan motor so its not a replacement for the Battery Tender. On the subject of Battery Tender's, the cheap China knock off is piece of crap. I bought three and they've crapped out one three month winter season. The Battery Tender Junior so far has been a really nice charger/maintenance. In these days of batteries and vehicles that have a limited voltage requirement even if not running a simple trickle charge doesn't cut the mustard anymore. It needs a maintenance electronic feature. I'm sold on smart chargers. Tj |
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Posted: 4/23/2014 9:23:04 AM EDT
[#10]
Quote HistoryQuoted:
Wait...are you saying that solar trickle chargers are worthless for helping to keep a battery charged?...not calling you out here...(yet ) but I'm trying to learn.
AND...I do run a battery tender on some other little used batteries....but the above mentioned dodge is parked (and will stay there...according to the wife) where there is no electricity....so I'm SOL there... Quote HistoryQuoted:
Quoted:
It's toast. Throw your trickle charger in the trash. Buy a Battery Tender Jr. on Amazon. These are used to sustain a battery that isn't used daily. BatteryMinder makes a good one too. It charges, desulfates, and has models for AGM batteries. It is a bit more money, but it is necessary if you need to charge a battery. I have 5 Battery Tenders and one BatteryMinder. I couldn't give them a higher recommendation. I got 14 years out of a Yellowtop Optima with the Battery Tender. Wait...are you saying that solar trickle chargers are worthless for helping to keep a battery charged?...not calling you out here...(yet ) but I'm trying to learn.
AND...I do run a battery tender on some other little used batteries....but the above mentioned dodge is parked (and will stay there...according to the wife) where there is no electricity....so I'm SOL there... Your battery was toast after it sat at a reading of 6 volts for an extended time. Solar chargers are useful to maintain a battery, not 'fix' it. Replace the battery, add a solar charger, and check the battery voltage each month or two. If it isn't ~13.5 volts, there is an issue. Monitor the water level. Keep the battery disconnected except for the charger. There is no need to complicate things with charge controllers, etc, when an automotive type solar battery maintainer is used. There's really nothing to this...
Don't through your battery float charger away because someone has a love for their Battery Tender. Altho I use them, as well as others, there are plenty of others that will do what you want nowadays. |
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Posted: 4/23/2014 9:44:25 AM EDT
[#11]
I wouldn't think the solar charger can generate enough current to hurt a car battery, not try to revive it once it's dead. I would think it'd keep a battery that starts in good shape alive, though. |
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Posted: 4/23/2014 10:54:54 AM EDT
[#12]
Quote HistoryQuoted:
I wouldn't think the solar charger can generate enough current to hurt a car battery, not try to revive it once it's dead. I would think it'd keep a battery that starts in good shape alive, though. A 7W 12V panel produces ~0.6 amps. It could very easily overcharge a battery under the right conditions without a charge controller (e.g., leaving it on a fully charged battery for days at a time during full sun, especially in winter when the self-discharge is lower and the panel is operating at peak efficiency). |
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Posted: 4/23/2014 1:12:51 PM EDT
[#13]
Quote HistoryQuoted: A 7W 12V panel produces ~0.6 amps. It could very easily overcharge a battery under the right conditions without a charge controller (e.g., leaving it on a fully charged battery for days at a time during full sun, especially in winter when the self-discharge is lower and the panel is operating at peak efficiency). Quote HistoryQuoted: Quoted: I wouldn't think the solar charger can generate enough current to hurt a car battery, not try to revive it once it's dead. I would think it'd keep a battery that starts in good shape alive, though. A 7W 12V panel produces ~0.6 amps. It could very easily overcharge a battery under the right conditions without a charge controller (e.g., leaving it on a fully charged battery for days at a time during full sun, especially in winter when the self-discharge is lower and the panel is operating at peak efficiency). I'm skeptical, but stand corrected if you know this to be true. For most car batteries, 0.6A is going to be < 1% of their C20 rate. While colder temps might raise efficiency of the charging system, generally there's days w/o sun and not many hours of it on a good day. I would think that if one of those little panels could put the battery at risk, then your typical cal alternator would completely destroy the thing. This is all supposition on my part, however. |
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Posted: 4/23/2014 4:03:14 PM EDT
[#14]
If used intermittently on a battery that sees a regular load, a small panel with no charge controller probably wouldn't cause any problems. But the OP is saying he only starts the truck 4 times a year. Leaving a 7W panel connected directly to the battery that has no loads for months at a time could certainly cause issues without a charge controller.
This page has some good info: Flooded batteries lose about 8% of their capacity each month in winter and about 30% each month in summer. Sealed batteries lose about 1.5% of their capacity each month in winter and about 10% each month in summer. In summer, assuming a monthly loss of 30% capacity, a flooded 100 Ah battery would lose an average of 1.1 Ah of capacity per day.... The 7W panel the OP owns can produce 4-5 ah on a good sunny day (8 hours x 0.6 amps, minus inefficiencies). 3 months of that and the math is not good for the longevity of that battery. |
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Posted: 4/25/2014 3:57:56 AM EDT
[#15]
I'd try jump starting the dead Dodge battery with your other vehicle before calling it dead and replacing the battery.
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Posted: 4/25/2014 10:15:06 AM EDT
[#16]
Quote HistoryQuoted:
It's toast. +1. After a starting battery is allowed to become completely discharged (i.e., less than 10 volts), it's never the same again. The longer it sits in this discharged state, the more damage it sustains. Even if you manage to "recharge" it afterwards, it'll never have anywhere near its original capacity. |
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