Solar Battery Charger/Maintainer

[fschrope]

I've been playing around with using solar to maintain the batteries on my motor home - starter and house batteries.

I have a 100 watt solar panel and a control unit. The unit is variable in voltage although to Model T folks, I don't think you could set it to 6 volts.

Question: If I leave it hooked up 24/7 and very seldom use it, what voltage should I set it at. I was told 13.2 volts. Is that to high? Before I hooked this system up, I don't know what it was charge to as I just put one of those 1 amp maintainers on it and it boiled a considerable amount of water out of the house batteries.

What thinks ya?

If this "trips anyone's trigger", I'll give more details on how I built it.

[Scott_Conger]

I think 13.2 is probably OK

while moving to WY I hooked up a tiny, unregulated solar charger on my jeep's battery. When we got back here for the last time 18 months later, the jeep started, and ran fine for about a week. Then while shopping in town one day: *POP*

I very quickly learned where the nearest Auto Parts store was from the Ace Hardware that I was stranded at. That battery was DEAD!! Had 2 shorted cells. So, not a fan of the cheapy solar chargers, but if yours is regulated to a very low amperage, I still would not want to run it without some sort of a voltage/current regulator in the system.

Just my $.02

I will be interested in seeing what other responses you get as I am interested in a QUALITY setup, too.

[Norman Kling]

Ten or 15 years ago we had someone in the San Diego club who had a depot hack with a solar collector on top of it. It worked to charge his battery. I don't remember who it was and haven't seen his car. It might have been someone who moved away or someone who came from somewhere else on one of our tours. Seems we saw it in Jamul at Simpson's Nursery where they had a barn full of old cars. They are no longer there because it was right next to Jamul Casino and I think the tribe bought the property.
Norm

[fschrope]

Scott - My setup is just a panel with the controller and a voltmeter and ampmeter. I couldn't find an ampmeter with less than 30 amps, but that one works OK. My motor home is a home made one on an '87 Freightliner conventional. Basically a 24 foot sleeper box. It has 4 group 31 deep cycle house batteries. I check the gauges often and the voltmeter stays at about 13 volts. It is one out of another Freightliner. The ampmeter shows a very very slight charge - within the width of the hand. If I turn on both furnaces and a bunch of lights, it will show a slight charge with the sun shining.
I was/am more worried about over charging the house batteries than anything. I used to have it set a 12.6 volts and it definitely didn't keep them charged as when I turned on the light and furnace, the voltage would drop to about 12 very quickly. 13.2 seems to correct that and hopefully doesn't boil the water out of them. I don't like the thought of having to buy new ones. Lotsa bucks.
If you're interested, just google ebay solar and you'll find all this stuff. The panels are about $100/100 watt. I forget what the controller costs, but it's not much.

[Craig Leach]

Twenty years ago or so I started experimenting with solar to have lights in my tach room. Didn't need anything more than lights because I
often got off work very late and needed to feed the horses in the dark. Used a 5 watt HF panel and a used group 24 car battery. Now I have
5 out buildings with solar on them. 3 of them also are used to maintain batteries in & out of my T's. 6 VDC charge controllers are hard to
find ( one of the reasons I went with 12 volts in my T's ) The charge rate & voltage will depend on the batteries you are charging. See MFGs
recommendations on this. 5 watts on a car battery will pretty much regulate itself, but will not charge a dead battery. I have setups from
5 watt to 150 watt with charge controllers on any with over a 5 watt panel depending on what the battery & load demands are. The best
results I have had involve monitoring & testing on a regular basis. I like to see 12.4 to 12.8 when I check at night.
Fred even a 1 amp trickle charger can boil a battery. I have found through testing that putting a 1 amp charger on a timer can prevent that.
A motorcycle battery will work very good on for 2 hours a day and not boil. I'm thinking that if your coach batteries boiled at 1 amp there
may have been something else going on. Digital battery analyzers are worth the cost and can be had for $30-$200 both of the ones I have
where under $150 and have worked great for years. One of the reasons that 6 vdc charge controllers are hard to find I think is most solar
panels 12vdc & up I have had to change 72vdc series wired panels to 24vdc parallel to reduce the controller costs. Look on some of the
prepper off grid YouTube videos, they have some real good info once you get past the ego parts.
Good luck.
Craig.

[TXGOAT2]

Perhaps a solar panel could be used operate a quality DC/AC inverter which could operate a quality, well regulated 120 volt AC charger/maintainer. A marine battery/electronics supplier might have what you need. For accurate current and voltage measurements, you need quality meters with the expected voltage and current draw near the middle of the meters' ranges. For a smaller setup to maintain a 6 volt T battery, putting a low watt "pea bulb" in series with the battery & charger would reduce the charge rate to a minimum as the battery came up to full charge.

[Craig Leach]

I stand corrected I googled 6 vdc solar chargers and found some 6volt/12 volt self sensing charge controllers they are only 3 amp. They sell
for under $20. I don't know if they are something new or I just missed them back when I was looking for them before. I would think a 5-10
watt solar panel would do a good job of keeping a 6 vdc model T battery up and ready.
Craig.

[TXGOAT2]

Concerning a Model T 6 volt battery, the Optima type batteries do a very good job of holding a charge in vehicles that are not driven regularly, provided there are no parasitic drains.