Charging question

[kai38]

I have a 100w panel mounted on my RTT.
I have it wired so when parked I can run the power cables from the panel to the controller and it has a male cigarette lighter plug on the end which I plug into an outlet in the bed . That runs to my 2nd battery to maintain it while parked.
My question is, can the controller and panel be plugged in to charge while I'm driving or should it be unplugged and put away.
Thanks

 

[GR8ADV]

Wow a cigarette lighter plug leading to the battery via the bed? Did I hear that right? What kind of amps do you see at the battery? I could be way off but I expect you could benefit from a more significant connection and wire from the controller to the battery. Also the run from the controller to the battery should be as short as reasonably possible.

 

[kai38]

Yes the 12v outlet is fused and runs to battery with heavy gauged wire.
I also have a battery clamp to use straight to battery if needed

 

[4x4junkie]

I completely agree with the above, that lighter connection is a huge bottleneck if you're using it to keep your battery charged while parked (such a connection would probably work fine for a simple 2-watt solar battery maintainer, but not for an actual 100W solar power system).
I would suggest installing a dedicated connector for that if you need to have your charging controller disconnected frequently.

But to answer your question, no, your controller should be fine if it's connected while the engine is running. It will simply shut off the charge current from the panel should it see the charging voltage coming from your alternator.

 

[jonyjoe101]

you can keep it connected 24/7 , actually its better that way. The controller has to always be connected to the battery first before the panel. Otherwise it might not function properly, so leaving it connected would avoid complications.

The 100 watt panel puts out about 5 amps, well within the limits of a cigarette plug (some rated up to 15 amps max), the only drawback they might make a loose connection/slip out when driving around.

 

[4x4junkie]

It being rated at a certain current doesn't mean it doesn't have a higher voltage drop than other types of connections having the same current rating... A typical cig-lighter connection creates about 0.3-0.4V drop @ 5 amps (and that's when the connection is perfectly clean, forget about when it invariably gets all dusty). That's enough to noticeably extend the amount of time it takes for the battery to reach full charge (there are only so many hours of sunlight in a day). Plus he didn't say if his controller is PWM or MPPT... If MPPT it might be 6½ to 7½ amps he's trying to push through that connection).

What I would suggest is hardwire the controller directly to the battery, and if you need to disconnect it for whatever reason, just install a high-current switch or circuit breaker inline with it (or have the fuse for it accessible so you can just pluck the fuse out when needed).
Or just use the battery clamps instead.

 

[1stDeuce]

Actually, the 12v of the cigarette lighter plug is no threat to shorting against the vehicle unless the grounds are connected. So it's relatively harmless unless you can somehow short the ground of the lighter plug against the same metal object that the positive on the plug is against. Otherwise it's the equivalent of hooking one end of the jumper cables up, and then touching the other + end to something on another car. Nothing happens until you ALSO connect the ground clamp...

I agree though that just hard wiring it would be a better option, and likely result in faster charging. There is a bit of loss through a cigarette lighter plug, even at only 5a of current, and when current is highest, loss is highest, so you're really holding your solar system back. No harm in connecting it directly, as it'll then just stop charging when the engine gets the voltage over 13.6 or so.
Chris