Small solar panel for Tab 400 battery charging while in storage yard

ccrider098 · October 2018

Hi guys. I am storing my Tab 400 in a storage lot that doesn't have electric. I was thinking of hooking up a solar panel and charge controller for the winter instead of taking the two heavy batteries out and keeping them in my garage. I will be going on a couple of trips over the winter so taking them out and putting them back for each trip sounds like a pain in the neck.
Anyone use a solar panel to keep their batteries charged? How many watts would I need to maintain the charge? Any help would be appreciated. Not too familiar with solar as of now. Thanks!

pthomas745 · October 2018

If you just want to do a trickle charger, then one of the small solar panels for trickle charging can be used without a controller:

Do I always need a charge controller?

Not always, but usually. Generally, there is no need for a charge controller with the small maintenance, or trickle charge panels, such as the 1 to 5-watt panels. A rough rule is that if the panel puts out about 2 watts or less for each 50 battery amp-hours, then you don't need one.

For example, a standard flooded golf car battery is around 210 amp-hours. So to keep up a series pair of them (12 volts) just for maintenance or storage, you would want a panel that is around 4.2 watts. The popular 5-watt panels are close enough, and will not need a controller. If you are maintaining AGM deep cycle batteries, such as the Concorde Sun Xtender then you can use a smaller 2 to 2-watt panel.

Taken from here: https://www.solar-electric.com/learning-center/batteries-and-charging/solar-charge-controller-basics.html

Amazon has many to choose from: https://www.amazon.com/Sunway-Solar-Maintainer-Motorcycle-Snowmobile/dp/B06WP95W51/ref=sr_1_3?ie=UTF8&qid=1540324112&sr=8-3&keywords=solar+trickle+charger&dpID=41-Qsjmd8-L&preST=_SY300_QL70_&dpSrc=srch

ccrider098 · October 2018

Thanks for the quick response. That is similar to what I was thinking except I thought I needed a charge controller. I think that will work for me. My Tab is only a couple of blocks from my house so I could always stop by and check on it to make sure it is not overcharging/undercharging. Thanks for the links, it is greatly appreciated.

ColoradoJon · October 2018

If it were me I would definitely use a 3 stage charge controller to protect your batteries. Just my humble opinion

pthomas745 · October 2018

For less than 4 or 5 amps? Why?

cafyrman · October 2018

Shouldn't be a big deal with a small panel. But you could always buy a decent sized controller now with plans to upgrade to solar in your rig and run the small panel through that.

Marceline · October 2018

I've been using this 10w Coleman panel that doesn't require a separate controller for my T@B CS-S. It seems to work fine. But I know that the 400 has bigger batteries.
https://www.homedepot.com/p/Coleman-10-Watt-12-Volt-Solar-Trickle-Battery-Charger-58025/300435903

ccrider098 · October 2018

If I use one of these smaller panels can I just plug it in to the cigarette lighter plug inside the rv instead of running it to the battery?

ColoradoJon · October 2018

@pthomas745 - as I said, my humble opinion. An uncontrolled, unmonitored charging source is just that - uncontrolled and unmonitored. 1 amp is enough to kill a person and if the voltage is high enough you can overheat your batteries. Batteries can get expensive. A charge controller is cheap insurance. Again, my humble opinion.

Sharon_is_SAM · October 2018

@ccrider098, I suspect that, with a trickle-type solar panel and very limited wattage, voltage loss would be too great going through additional wiring from the 12 v outlet and battery charger circuitry. A low wattage panel close to and connected directly to the battery is typical.

ScottG · October 2018

ccrider098 said:

If I use one of these smaller panels can I just plug it in to the cigarette lighter plug inside the rv instead of running it to the battery?

In theory this would work so long as the 12V side of the converter was a just a simple distribution panel, but I'm not sure if that is the case. The circuits may be wired in a manner that prevents back feeding through the fuse block.

Depending on how far the plug is from the battery--and how heavy the feed wire is--there's also the potential issue of voltage drop.

My personal $0.02 is that if you are going to do something, do it correctly. Use a suitable charge controller and connect it directly to the battery with as short a wire as possible.

ccrider098 · October 2018

Thanks for all the feedback. I think I will do a panel and charge controller wired directly to the battery. That sounds like the best bet.

Marceline · October 2018

ccrider098 said:

If I use one of these smaller panels can I just plug it in to the cigarette lighter plug inside the rv instead of running it to the battery?

I connect directly to the battery via a SAE connection wired to the battery (be sure you have the polarity correct) and I remove the fuse from the battery line to the trailer as I still haven't gotten around to installing a battery cut-off switch. I think that the cigarette lighter port might work in theory, but you would have to leave the battery cut-off switch open and/or the fuse in place, so you would be working against the trailer's parasitic drain. I think that it would be better to connect it straight to the battery.

TwoOwlsTalking · October 2018

Hi ccrider098,

I have a 400 too and use a small solar charger to keep the battery topped off. I use a small 50w panel and a decent 3-stage Renogy PWM charging controller. I added a small power center that goes directly to the battery (bypassing the master cutoff switch) under the TV at the end of the bed. This allows me to lay the solar panel on the bed, picking up the sunlight through the back window. Works great out here is sunny/foggy central California.

see T@b 400 Power Center Addition

hope this helps!
Billy
T@b Majal

OpenSky · October 2018

I use an 18W panel to trickle charge my battery, and it holds up against the parasitic loads. Worked fine without a charge controller, although I ultimately installed a charge controller for my campsite panel (100W), and now plug the trickle-panel into the charge controller when storing.

gspdx · May 2019

I have a T@B 400 BDL with the factory solar panel and the Victron 75/15 MPPT charge controller. It is great but would like to add a trickle charger when the T@B is covered. So the questions:

Does anyone know if I can wire another panel into the charge controller?
Could I use a switch to toggle between the factory panel and a portable panel and if so does anyone have a recommendation?

Any advice would be appreciated.

Cbusguy · May 2019

The controler is rated for 15 amps.......Not sure which panels are on your trailer. But if the trailer is covered and you have something smaller than 50 watts, you are probably fine. I wouldn't bother with a switch between the two and it might end up being a good addition if you are camping in the shade to chase the sun a bit to charge your batterys.

gspdx · May 2019

That is a good point. I will consider that rather than a small trickle charger.

Small solar panel for Tab 400 battery charging while in storage yard

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Do I always need a charge controller?

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