Solar chargers for Two 12 volt batts

Cool thks guys for all the info

Rockinfigs wrote:
ok so from what i read i shouldnt use a solar panel charger/maintainer while iam using my hauler out in desert with the battery switch ON?

This is flat wrong. Multiple sources of charging will not hurt the battery or any of the charging systems. Very common to have multiple systems charging an RV battery.

Rbertalotto wrote:
35 amp draw for static loads????
BTW...static loads are co2 detectors, propane detectors, etc. Stuff left on when you think everything is shut down.

Less than 10Ah usually. Some propane detectors draw 8AH over 24 hours, and some - 2 AH. And when you think that everything is off, the radio on standby still draws something. IMO, rig in storage requires no radio on standby and hardly any detectors - nobody will even hear if it goes off. Lowly underpaid security guy will call the fire truck when he sees the smoke and flame, and this is if he is not sleeping.

Sometimes people forget that LP fridge draws 12V.

Just disconnect the batteries when in storage. Self-discharge for 2*100AH will be under 1 AH a day, and 15W charger will cover this. But if you have either detectors, or radio, or fridge on, then 15W is not enough.

Pianotuna knows what he is doing. If his rig that draws 35 AH with everything off, then there must be something that draws that much and can't be removed.

Hi,

The only way to balance an odd number of batteries is to use method #3 on the smartguage page. I don't think you could do that with only one extra foot of wire.

However method #2 is an improvement on #1 for sets over 3 jars.

RCtime wrote:

If you wish to understand the "why" surf here:

correctly interconnecting multiple twelve volt batteries

I rewired my 3 - 12V house batteries to the proper way. Winnebago had all the connections from the end + - battery posts on the slide out tray.
It took about 15 inches more wire. I guess saving a foot plus of wire for every coach they built with this battery arrangement was worth the savings to them.

Rockinfigs wrote:
ok so from what i read i shouldnt use a solar panel charger/maintainer while iam using my hauler out in desert with the battery switch ON?

Mex was talking about when the rig is not being used. (called "storage" --of the rig---not to be confused with "storage" meaning the batteries wrt solar systems)

Hi Rock,

My solar charger is wired directly to the battery bank with a separate disconnect switch for only solar. I regularly use it with the battery switch "on" and the solar system charging as much as it can.

The only time I turn the solar system off is if I plan on servicing the battery bank.

ok so from what i read i shouldnt use a solar panel charger/maintainer while iam using my hauler out in desert with the battery switch ON?

For battery maintenance I believe I would opt for a manageable size panel, a very reliable controller that is designed to last, and most importantly of all a good quality total battery disconnect switch. It is MOST important to eliminate the possibility of having something fail or forgetting to shut something off. When a good battery disconnect switch is selected to OFF, it doesn't mean ALMOST OFF or maybe sometimes OFF, it is a done deal.

But before going into storage with a maintenance style battery upkeep system the batteries must be totally and completely charged. No rush jobs, no deciding "Well shoot they must have been charged somewhere along the way" the batteries must enter storage with electrolyte in all cells at full specific gravity. How the batteries get recharged before storage is the owner's responsibility.

IMHO to repeat, neglecting to put a good battery disconnect switch in the system means the maintenance system may as well be tossed out the window. It would almost be a waste of time.

pianotuna wrote:
This is what is balanced and best for twin twelve volt batteries.



As it often doesn't cost a dime more to do this, I think it is worth the trouble.

If you wish to understand the "why" surf here:

correctly interconnecting multiple twelve volt batteries

Others may say it doesn't matter--but unless there is a compelling reason to not optimize charging and discharging why not do it the best possible way?

I rewired my 3 - 12V house batteries to the proper way. Winnebago had all the connections from the end + - battery posts on the slide out tray.
It took about 15 inches more wire. I guess saving a foot plus of wire for every coach they built with this battery arrangement was worth the savings to them.

RoyB- Charging your batteries to a good 90% charge state so you can use them again from a SOLAR SOURCE is the same as charging them from your on-board converter. Battery science is at work here. No short cuts

If you want to use your batteries right away after dropping them down to the 50% charge state then these are the basic rules you have to follow to get there.

"Progressive Dynamics ran this test on the amount of time it took a PD9155 (55-amp) converter/charger set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.

14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.

13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.

13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge."

The rule of thumb that has been established by all the good folks on here giving you info is that it works very well if you have enough DC CURRENT available from your DC Charging source to give you around 20AMPS of current for each battery in the setup being charged if you want to complete the charging in the above listed time frames.

Note that the solar controller will give you these same charging DC voltages just like your on-board smart mode controller/charger does. The problem with the solar panels is they only produce a small amount of available DC CURRENT. From what I read is the 120WATT SOLAR PANEL for instances only produce around 5-7AMPS usable DC CURRENT during the high sun period. To get to your 20AMPS per battery to be able to recharge in a short three hour time frame will require several 120WATT SOLAR PANELS if only one produces 5-7AMPS for 5-6 hours a day.

The other golden rule is what you take out you must put back in. If you are using a real low 15WATT solar panel it will work just fine but it will take "many many days" to put back several hundred watts if all you have to play with is 15WATTS for 5-6 hours a day with high sun....

Still yet another golden rule is the deep cycle batteries will not perform to their listed specs unless you start out using them with at least a 90% charge state. If you run a deep cycle down to lets say 50% over night and just recharge back up to lets say 60% charge using something small like a 15WATT solar panel for an hour or so when you start using the batteries again with your heavy load they will drop like a rock and you will be back to your 50% charge state in a "big" hurry... No battery power to use after that happens...

I do just fine running all my toys in the one day/night run off the batteries, then recharging the next morning day to at least their 90% charge state so that I can do all of this all over again the next day/night battery run. I live with one eye on my trusty ole homemade BATTERY MONITOR PANEL


These are just my observations from my past five years experience from camping off the power grid - listen to the experts here... NO SHORT CUTS ALLOWED... Plan to be successful first then it won't get dark on you around 10PM at night...

Roy Ken