Battery Maintenance

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fschrope
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Battery Maintenance

Post by fschrope » Tue Jan 25, 2022 9:46 pm

This may be considered "Off Topic" by some, but I'm posting it here as the knowledge can be used on Model T's or any vehicle that sits around a lot.

I'm getting into solar energy as a way to keep the batteries charged on vehicles that just sit most of the time. In my case, they are 12 volt, but there should be some way to convert it to 6 volt.

I have one 100 Watt solar panel leaning up against the south side of my pole barn. The T's and my motor home are inside - along with several other vehicles. The little controller allows me to set the charging/maintaining voltage.

My question is:
What is the best voltage to set the controller to maintain the batteries? I have it set at 12.8 volts but it seems like the battery voltage drops to 12.0 volt with very little draw. In this case, there are three group 31? Deep Cycle batteries.If I hook a "One Amp Battery Maintainer" up, the voltage goes up to almost 14 volts and it seems like I can put a load on it and the voltage will stay up to the mid 12's for a while. Is that to high?

If this is something interesting to folks here, I'll elaborate on how I have it set ups. It works great.


Art M
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Re: Battery Maintenance

Post by Art M » Tue Jan 25, 2022 11:21 pm

This is the place for battery maintenance information. Most of us have to put our cars away for the winter and consequently have to deal with our batteries.
I have no experience with solar battery chargers, but they seem to make sense for winter storage.

Art Mirtes

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Craig Leach
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Re: Battery Maintenance

Post by Craig Leach » Tue Jan 25, 2022 11:54 pm

Hi Fred,
I have been using solar to provide lighting & maintain my T batteries for 20 years. 5 watts will maintain a 12 battery if the rated voltage is not to high with out a charge controler I have two systems running that way. I have a 75 watt with a charge controler for lighting & charge backup batteries. a 25 watt with a charge controler ( real cheap one) for lighting & to maintain the battery in another T. a 300 watt system with a inverter for lights & 115VAC
and a 75 watt to run a condenser fan to circulate air in one building to keep the temp. down in the summer time (with no battery ) All of my charge controlers & non controled systems run up to 14 VDC in peak sun light. then drop to 12.5 or so at night. I have found this voltage cycling seems to ward off sulfating of the batteries I get 3 to 5 years out of my batteries on average for marine & truck batteries ( not batteries designed for this ) You might need to adjust your controler up some? I have never tried chargeig 6 VDC batteries but you may try a EMPI #9384 12v to 6v voltage reducer it is 50W - 4 ohms for running a heater & wiper motor in a VW they are only about $15 on ebay but it may not give you the Amps you want. There are some voltage drops that are more expensive. Like I said have never tried to charge 6 VDC. I'm not super big on solar as far as alterative solution to power but it works for me where I'm unable to have regular power supplied. Also I run a fuse on all my systems so if anything has a large amp draw the system is shut down. Hope this helps alittle.
Craig

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TRDxB2
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Re: Battery Maintenance

Post by TRDxB2 » Wed Jan 26, 2022 12:32 am

Buy one of these and you can take it with you (on tour). Some have over/under charging protection. They make them for 12 volts too.
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Re: Battery Maintenance

Post by TonyB » Wed Jan 26, 2022 12:37 am

Questions have been asked about charging lead acid batteries. Those of us working on the six volt regulator have been pondering the same problem. Here what I have found to date.

Fully charged single cells are discharged when the cell voltage drops to 1.96 volts and is considered fully charged when at 2.11 volts.

Translated into 6 volt battery is 5.95 and 6.33 volts
For a 12 volt battery the corresponding values are 11.90 and 12.66 volts.

Next problem is how high the maximum voltage should be to force charge into the battery. Here we ran into problems as there are different types of lead acid batteries. Some have additional chemicals which increase the maximum allowed charging voltage. So I checked my Chevy truck and the batteries appear to have about 14 volts maximum when they are being charged on a long run. The corresponding value for a 6 volt battery would be 7 volts.

I hope this info will help folks who are planning on using solar charging schemes.
Tony Bowker
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1914 Touring, 1915 Speedster, 1924 Coupe.

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Re: Battery Maintenance

Post by Novice » Wed Jan 26, 2022 1:41 am

62813_W3.jpg
I use a harbor freight battery maintainer float charger to keep my 12 volt auto batteries from discharging during long periods of non use. 10 bucks or less on sale. They make my old car. moped and generator batteries last 2 to 3 times longer. They don't charge Your battery just keep a float voltage on it to counter self discharge in the battery. I wire the float charger directly to the battery using quick disconnect plug and socket so the only thing in the car when driving is the small plug You can hide under the floor boards or floor mat. Your 12 volt solar charger should work just fine charging a six volt battery without a voltage controller. put a 1156 12.8 volt auto bulb in series with the solar cell and the six volt battery and a blocking diode to keep battery from discharging through solar cell at night. solar charger will only be charging during daylight or about 40% of the time or much less on cloudy days so overcharging should not be a problem. photos show cheaper charger with only alligator clips. and deluxe model 20 bucks which is already set up for quick disconnect and battery connect options.
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Re: Battery Maintenance

Post by JohnH » Wed Jan 26, 2022 6:10 am

I've been using a solar powered battery maintainer for about the last 17 years. It runs off my 12V DC solar supply which is reticulated around the house and garage. The circuit is essentially a 78HO5 three terminal regulator adjusted to provide 6.9V. A light bulb limits the input current to the regulator. There's also a bit more to it in terms of reverse polarity protection, etc. Since it's only intended for maintaining and not charging, the low current allows an otherwise inefficient circuit to be used.


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Re: Battery Maintenance

Post by Russ T Fender » Wed Jan 26, 2022 9:22 am

I have had a small solar panel on the roof of my trailer for years to keep the battery for the winch charged. I may be jinxing myself but that battery is now over 5 years old. It's a simple trickle charge device with over charge protection.


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Re: Battery Maintenance

Post by John Codman » Wed Jan 26, 2022 10:02 am

I have had a small solar battery charger/maintainer for years; it is 12 volts, but would charge two six volt batteries connected in series just as well. It is Volkswagen part # ICO 915 687. It is designed to plug into the car's cigarette lighter (remember them?) but the plug could easily be removed and replaced with a couple of alligator clips. I think that it is still available. I'm not sure of the price, but as I recall, it wasn't very expensive.


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Re: Battery Maintenance

Post by TXGOAT2 » Wed Jan 26, 2022 10:33 am

Any load applied to a DC system will cause some voltage drop. If you apply any significant load to a battery that is attached to a charger/maintainer, indicated voltage will drop. How much it will drop depends on the degree of loading and the capability of the charger/maintainer to supply current to meet the load demand, or some portion of it. When the load is removed, the indicated voltage will rise. If the load has exceeded the ability of the charger/maintainer to deliver current, the battery will discharge to some degree, and the voltage may remain at a lower indicated level for some time, as the battery will absorb current as it comes back up to full charge, or the charger/maintainer may cycle off and on for a while after the load is removed until the battery recovers charge and its current absorbtion diminishes. Low current trickle charger/maintainer devices are not intended to supply any significant load. They can meet the kind of very low current demand that many modern computerized vehicles impose on a battery during storage, but that's about all. Float voltage for various kinds of batteries varies. Battery condition will affect readings.


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Re: Battery Maintenance

Post by speedytinc » Wed Jan 26, 2022 11:50 am

Excuse my electrical ignorance, but wont a "12V" solar charger charge a 6V battery also without modification? Doesnt the battery, itself, regulate the amount of voltage it will take?
Like a diode cutout will charge any battery 6, 8, or 12V?.

Do I need to do some experimenting to confirm?


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Re: Battery Maintenance

Post by John Codman » Wed Jan 26, 2022 11:54 am

speedytinc wrote:
Wed Jan 26, 2022 11:50 am
Excuse my electrical ignorance, but wont a "12V" solar charger charge a 6V battery also without modification? Doesnt the battery, itself, regulate the amount of voltage it will take?
Like a diode cutout will charge any battery 6, 8, or 12V?.

Do I need to do some experimenting to confirm?
An excellent question. I don't know the answer, but if someone on this forum knows the answer for certain, I hope that he or she will enlighten us.

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Re: Battery Maintenance

Post by TRDxB2 » Wed Jan 26, 2022 12:30 pm

John Codman wrote:
Wed Jan 26, 2022 11:54 am
speedytinc wrote:
Wed Jan 26, 2022 11:50 am
Excuse my electrical ignorance, but wont a "12V" solar charger charge a 6V battery also without modification? Doesnt the battery, itself, regulate the amount of voltage it will take?
Like a diode cutout will charge any battery 6, 8, or 12V?.

Do I need to do some experimenting to confirm?
An excellent question. I don't know the answer, but if someone on this forum knows the answer for certain, I hope that he or she will enlighten us.
Yes BUT not like a cut-out and adjustments need to be made.
The main purpose of a cut-out is to prevent running the generator as a motor when the engine is shut-off. Its secondary purpose is to connect to the battery when its voltage threshold setting is reached (example 7v for 6v) to charge the battery without being able to regulate when enough is enough (that's what a voltage regulator does).
Trying to keep it simple: A 12 volt charger/maintainer would over heat a 6v battery at some point in time and then explode. No point in describing the work around, in case you miss a step. Many of Today's chargers and maintainers have circuity to prevent over charging a battery (reverse current etc) and are designed for the respective battery voltage size and to recognize when enough is enough, so they also have voltage regulation matching their advertised voltage.
Last edited by TRDxB2 on Wed Jan 26, 2022 5:09 pm, edited 1 time in total.
The past is a great place and I don't want to erase it or to regret it, but I don't want to be its prisoner either.
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Re: Battery Maintenance

Post by TXGOAT2 » Wed Jan 26, 2022 1:28 pm

A solar panel that supplied 7.0 to 7.2 volts at no load (full sun) would be very unlikely to ever overcharge a 6 volt lead-acid battery. Indicated voltage would drop to near the indicated battery voltage when the panel connected to a discharged battery, and indicated voltage would slowly rise to near the no-load voltage of the panel as the battery charged. Time to charge would depend on current capability of the panel, degree of battery discharge, battery condition, and availability and quality of solar insolation. Given the fact that solar panels automatically turn themselves off for more than half the time, I doubt if any regulation would be required other than a diode to prevent any back flow of power from the battery to the panel.

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