Wanting to add a solar battery charger.I have searched and searched Google about this and didn’t find the answer to my dilemma.I found a couple of forums that mentioned a potential problem with the way a trailer is wired on the inside.In my toy hauler I have two 6V batteries wired in series to supply 12V to it. http://www.trojanbattery.com/pdf/datasheets/T105Plus_Trojan_Data_Sheets.pdf I wanted a solar charger to be hooked up to them to maintain the batteries when in storage and ALSO when in use camping. I thought (and what I found on Google confirmed) that all I had to do is connect the positive from the charger to the positive battery out to the trailer and the negative from the charger to the negative out to the trailers frame. Ignoring the + and – battery terminals that are connected together. With the solar panel hooked up the panels controller says it is charging but the battery monitor inside the trailer shows discharging and my gas alarm beeps. I am going to try the solar charger on the batteries with the batteries Disconnected from the trailer to see if this works but I really want to be able to have a solar charger connected when the trailer is in use camping. Any suggestions??????????My solar panel is up to 18 wattsload charge 8 amp max controler cut in at 13V cuts out at 14.2V Thanks in advance.

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It sounds like the solar panel may actually be wired backwards and is discharging the batteries rather than charging. Verify the positive wire is actually positive with a voltmeter and recheck your panel to battery connections for accuracy.

Hi,18 watts is really not enough to maintain a battery bank of that size.There may not be a diode in the panel or you may have the polarity reversed.

You have your device hooked up properly.It's only 18 watts which is barely anything. Your RV's propane leak detector, CO detector, stereo memory, and refrigerator circuit boards probably pull more power than it is producing, thus you're still discharging your batteries.If you want to use the solar power when camping you should be looking at something like a 100 or 200 watt panel.Here's a rough idea of your system. Your 2 6v batteries probably have a capacity of around 220 AH. If they are discharged 50% you need to put back in 110 AH. That little solar panel of yours is probably only capable of about 1 amp when in full bright sunlight. That type of condition only happens about 4 hours a day. So, it would take you around 27 bright sunny days to recharge your batteries from half way down. This is assuming you have absolutely no other draws on the system, which isn't the case.That panel is kind of like spitting in the ocean.

Ok thanks guys,My battery specs show 185 AH at a 5 hour rate and 250 AH at a 100 hour rate. Would this 18 watt charger be enough to maintain fully charged batteries when in storage?Maybe having to disconnect the batteries from the trailer eliminating any draw on them?Thanks again

Solar charging batterries | Good Sam Community

20 Replies

MC63
Explorer
Dec 29, 2014
ok yes I will do that hopefully tomorrow as I have my RV stored a ways away and cant get to it today. I do have the batteries at home though and series connected and on my 12 volt 110 powered home charger and they seem to be charging ok. While I have you if you are still there would it make any more sense to hook the solar charger to the correct terminals on the trailer light connection instead of directly to the batteries?
Thanks again.
time2roll
Nomad
Dec 29, 2014
Still 3 lights to 1 light does indicate a significant draw. As if the controller was connected in reverse or some lights etc. were turned on.

Just adding the solar should not cause the batteries to drop in voltage. Best to get an actual voltmeter out and post the readings. Do plug in soon as the batteries probably need significant charging.
MC63
Explorer
Dec 29, 2014
smkettner wrote:
Very simple.

Solar Panel --> Controller --> Battery

Now what battery monitor inside is saying discharge? Is that the four light idiot panel? It just reads voltage.

BTW with 18 watts even one light on will discharge the battery. OK for storage as a maintainer but it will never charge those batteries. You really need 100 to 300 watts of solar to recharge or provide power while camping.

You are not too far from www.solarblvd.com to get some real equipment.

Forum Members Solar Installations With Pics

HaHa yes its just the 4 idiot lights. When the charger is connected it dropped from 3 lights on to 1 light on and the gas detector begins to beep. Thanks for the link and reponse
pianotuna
Nomad III
Dec 29, 2014
Probably not. My real life experience says for maintenance 24 watts would be the minimum. 120 watts would be much better, and 280 would be wonderful.

MC63 wrote:
Ok thanks guys,
My battery specs show 185 AH at a 5 hour rate and 250 AH at a 100 hour rate. Would this 18 watt charger be enough to maintain fully charged batteries when in storage?
Thanks again
time2roll
Nomad
Dec 29, 2014
Very simple.

Solar Panel --> Controller --> Battery

Now what battery monitor inside is saying discharge? Is that the four light idiot panel? It just reads voltage.

BTW with 18 watts even one light on will discharge the battery. OK for storage as a maintainer but it will never charge those batteries. You really need 100 to 300 watts of solar to recharge or provide power while camping.

You are not too far from www.solarblvd.com to get some real equipment.

Forum Members Solar Installations With Pics
MC63
Explorer
Dec 29, 2014
Ok thanks guys,
My battery specs show 185 AH at a 5 hour rate and 250 AH at a 100 hour rate. Would this 18 watt charger be enough to maintain fully charged batteries when in storage?
Maybe having to disconnect the batteries from the trailer eliminating any draw on them?
Thanks again
KD4UPL
Explorer II
Dec 29, 2014
You have your device hooked up properly.
It's only 18 watts which is barely anything. Your RV's propane leak detector, CO detector, stereo memory, and refrigerator circuit boards probably pull more power than it is producing, thus you're still discharging your batteries.
If you want to use the solar power when camping you should be looking at something like a 100 or 200 watt panel.
Here's a rough idea of your system. Your 2 6v batteries probably have a capacity of around 220 AH. If they are discharged 50% you need to put back in 110 AH. That little solar panel of yours is probably only capable of about 1 amp when in full bright sunlight. That type of condition only happens about 4 hours a day. So, it would take you around 27 bright sunny days to recharge your batteries from half way down. This is assuming you have absolutely no other draws on the system, which isn't the case.
That panel is kind of like spitting in the ocean.
pianotuna
Nomad III
Dec 29, 2014
Hi,

18 watts is really not enough to maintain a battery bank of that size.

There may not be a diode in the panel or you may have the polarity reversed.
Sloop_Smitten
Explorer
Dec 29, 2014
It sounds like the solar panel may actually be wired backwards and is discharging the batteries rather than charging. Verify the positive wire is actually positive with a voltmeter and recheck your panel to battery connections for accuracy.
2oldman
Explorer II
Dec 29, 2014
Go to the Tech forum and search 'solar'. Thousands of posts.

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Solar charging batterries

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