40 W solar panel

Rerail · October 2019

Folks,
We took delivery of our 2020 T@B 400 yesterday after trading the T@B 320. The new trailer does not have a solar panel but does have a plug on the side of the unit. My question is will a 40W panel be sufficient to charge the batteries. Its rated at 7 amp. The 400 has two 6 V batteries mounted beneath the bed and not up front like the earlier models. Not that should make any difference. However, the fridge is 12V only and I am wondering how much current it will draw.
Thanks,
Keith

JEB · October 2019

Rerail said:

Folks,
We took delivery of our 2020 T@B 400 yesterday after trading the T@B 320. The new trailer does not have a solar panel but does have a plug on the side of the unit. My question is will a 40W panel be sufficient to charge the batteries. Its rated at 7 amp. The 400 has two 6 V batteries mounted beneath the bed and not up front like the earlier models. Not that should make any difference. However, the fridge is 12V only and I am wondering how much current it will draw.
Thanks,
Keith

40W isn’t much. Under ideal conditions, you’re likely to see less than 3 amps, accounting for conversion inefficiencies and line loss. That panel is little more than a trickle charger. I’m not sure where you’re getting 7 amps, but the rough formula for a panel’s theoretical maximum, and I stress theoretical here, is watts divided by volts. 40 divided by 12 is just over 3, which you’ll never see in the real world.

pthomas745 · October 2019

As Jeb says, that 40 amp is too small. If the trailer battery switch is on, for example, the parasitic drain will be more than that panel could produce even under perfect sun.

"Generally", you should match the solar panel wattage to the battery capacity to ensure a good charging rate over time. You should, at least, look at a panel of 100 watts, 200 would be even better.

ScottG · October 2019

And since most panels put out closer to 18V in full sun, that means under ideal conditions your theoretical maximum charge current is closer to 2 amps. As JEB says, little more than a trickle charge, especially for such a big battery bank. Some of the calculators I've seen suggest even 100W would be on the small side.

Rerail · October 2019

Hello Folks,
I really appreciate the feedback and yes, it did not take me long to realize that this solar panel is not more than a trickle charger. I wondered why it was on sale and now realize its not going to work. I think we will purchase a solar panel of at least 200 watts.
I am curious as to whether leaving the solar panel out while away from the trailer presents an opportunity for thieves. Do you have to attach the panel to the trailer with a secure cable etc? My previous trailer had the solar panel mounted on the roof.
Thanks again.
Keith Stamper

Cbusguy · October 2019

Any gear out is an opportunity for thieves. I have a heavier aircraft cable as a theft deterrent. If they want it a hack saw or bolt cutters will have no issue cutting it. It is slowing them down just a bit so they can't just pick them up and walk away with them.
I hinges my large ridge 100 watt panels together to make a sort of 200 watt suitcase. That should slow them down as well

Estancio · October 2019

No 40W will not be enough. I run a 100W solar panel and it keeps my size 27 battery charged on sunny days. Panel is permanently mounted to a rear rack, so it is not easily stolen. Been wishing I had originally installed 150W or 200W panels.

40 W solar panel

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