small portable solar panel

For twenty bucks WindyNation sells a weather resistant PWM battery controller. I use it for a small panel to keep the batteries charged between trips when the TT is covered. It has lasted two years and is going strong.

https://www.windynation.com/Charge-Controllers/Windy-Nation-Inc/WindyNation-Waterproof-10A-12V-Solar-Charge-Controller-w-LED-Charging-and-Load-Indicators/-/1981?p=YzE9MTc=

Jebby14 wrote:
should a small portable panel be alligator clipped direct to the house battery or will it feet too much voltage and cook the battery? I don't think they have any logic or controller.

I checked on this with my TORKLIFT Battery box that houses two groups of two GC2 6V batteries wired in series giving me 12VDC at 215AHs Capacity out of each group. When I parallel these two groups then I have 430AH capacity.

The battery metal case came with a 10WATT Solar Panel on one end...

Google image

The comment was if you are connected to two or more batteries than NO BATTERY CONTROLLER will be necessary... You can connect the 10 WATT SOLAR PANEL cables directly to the battery group terminals for BANK1. If you connect the 10WATT Solar panel to a single battery then it may boil out fluids over time...

I am going to order a second 10WATT Solar Panel to connect directly to the two GC2 6V batteries wired in series in my BANK2. I am under the assumption I will not need a BATTERY CONTROLLER for either of these two GC 6V Battery groups wired in series.

Having the 10WATT Solar panel should only provide a trickle charge to each 12VDC Battery bank group when in HIGH SUN. Having the same setup for the second group will do the same. When I use these my BATTERY switch setup I will use NONE-BANK1-BOTH BANKS-BANK2 then back to NONE or OFF using he master rotary Blue Sea switch...

Playing with this solar panel setting in high sun I was able to see 14-15VDC being absorbed into the two GC2 6V BATTERIES wired in series... The current spec this solar panel will deliver 0.58AMPS in high sun...

This would take a very long time to charge any of the batteries but once the battery bank is charged up these should provide a trickle charge to keep them topped when not connected to any loads. To get one of the GC2 6V Battery group in series group from its 50% charge state to its 90% charge I estimate will take around 4 hours hitting the group with 60AMPs @ 14.4VDC from my smart mode converter charger PD9260C... I am hoping charging two of the GC2 6V Battery Groups in 'PARALLEL' will take around the same 4 hours to get from a 50% charge to a 90% charge state... Have not done either of the these two groups charging events yet. Some folks are telling I may have to get a different charger unit that has the BULK CHARGE mode at 14.8VDC for my GC2 6v batteries...

Roy Ken

How small?

“How small?”

30 watts, 2oldman.

The general rule of thumb is that you don't need a charge controller if the charge amps are 1% or less of the battery AH rating. If you have a "standard" group 27 battery that's about 100 AH then no more than a 1 amp panel output. This would be probably around a 15 or 20 watt.
However, a charge controller is never a bad thing. They are less expensive than cooked batteries.

This may help:

https://freecampsites.net/adding-solar/

Hi guys. Not sure the output of the panel. Came with the camper. I did find a quick connect for it in the battery box. The think is tiny (maybe 5"x 16") cant see the output being high. I'm going to use it as is this weekend. More battery and a controller is in the future but I'm going with what is there for now. We are in the final stages of leaving for her maiden voyage. As always, much thanks for all the advise.

My advice is to use a voltmeter on the batteries.

For that small of solar panel your parasitic drains will be more than what it puts out by a wide margin, no worries.

A 5" x 16" solar panel would be maybe 4-5 watts, so no worry of it boiling the battery.