The instructions for the PT charge controller also say that you must always connect its red and black leads to the PV panel before connecting its blue and white leads to the battery. I had imagined using ring terminals to (semi)-permanently attach the charge controller to the battery, and securing the controller somewhere inside the battery cave, so this dictate is rather inconvenient. Further, I have disposed of the original Interstate battery and am about to have a 65# AGM battery installed, which I will be unable to move because of its weight.
John Drake at solarsellers.com has suggested attaching leads to the battery as I had planned, but then using a flat 2 pronged SAE connector to hook up the charge controller to those leads each time after establishing the connection between it and the PV panel. This probably means the charge controller would not be permanently attached to the trailer, and thus more susceptible to theft.
The instructions go on to say: "Ensure the battery is disconnected and/or safe operating procedures are follwed when making battery connections. Extreme care must be taken to ensure the battery is not shorted. BE SAFE....Qualified personnel only to connect and operate this unit."
I gather the concern here is that you could get an electrical shock if you touched any part of the circuitry once everything is hooked up, or more likely, in the process of hooking up the circuit. At this point I don't have a way to disconnect the battery, and I don't know what the standard safe operating procedures are. I can imagine that handling SAE connectors could even be somewhat risky, while screwing ring terminals onto the battery posts with the PV panel putting out voltage would be even moreso.
I gather some people have some sort of battery disconnect switch. Would that be installed inside the battery cave or near the converter? Neither location sounds particularly conveneint.
It occurs to me that possibly you could easily circumvent this entire issue by placing the PV panel face down on the ground before hooking things up, and the hooking up could then be done in no particular order. Am I right?
Well, I'm glad you brought this up. I hadn't noticed the part of the instructions saying that you must connect the battery first. My intention was simply to unhook the panel without worrying about disconnecting the charge controller from the battery! We'll have to let the experts who have already done their hookups tell us about this one. That would be very inconvenient if we had to disconnect the charge controller each time we unhooked the panel. If we have to, we can install a switch, I suppose, that is accessible from the interior of the trailer.
On the issue of battery protection, you always get a lot of warnings about safety relative to batteries. The big thing is to not short the positive terminal to the negative terminal at any time. If you do, sparks will fly and things can be damaged (including you!). But I don't think you have to be too concerned when you are doing things like attaching ring terminals. A good procedure if you are attaching connections to any part of the dc circuit in your trailer is to simply remove the battery connectors while doing the work, do it, and then reattach them. I usually disconnect the negative terminal, then the positive terminal. After finishing the work, I connect them in the reverse order. This is because the negative post of the battery is connected to the frame of the trailer. This way, if you accidentally short the positive to the frame, no problem. If you accidently touch the negative to the frame, no harm done because you are going to connect it that way anyway.
I'll be monitoring to see what our experts have to say about your sequencing issue. Thanks for bringing it up.
P.S. Don't worry too much about shock hazard. 12 volts is simply not enough to do any damage to human beings except in very, very rare circumstances. You can just put one finger on the positive terminal and another on the negative terminal if you like without any fear. (Unless, of course, you have gotten some battery acid on those terminals!) It akes maybe twenty or thirty volts before you will even begin to feel anything.
Later P.S. I just sent an e-mail to the guy at solarconverters.com asking him this question. I'll let you know what he says.
Edited by Art Davis, 04 May 2009 - 10:19 AM.