Extatic sex and recharging our batteries--HeLp! [RE-wrenches]

[Gary Higbee]

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Wrenches,

OK, so the first part of the subject line can be a great way to recharge batteries. I don't need help with that. I would very much appreciate your help, though, on another sort of recharging system. 

Maybe my original subject line wasn't catchy enough. Sorry, I just really hoped to tap into the wisdom of the Wrenches, and was frustrated at the lack of response from my post of a couple days ago. I did receive one (personal) response. Thanks to Rick Cullen, of RV Power Products! Yes, I'll do away with the cheap/creative? subject line now (and won't go for a third post).

Maybe none of you know how to do this sort of thing, and maybe this is really new terrain, but I expect "the answer is out there." Well, I think we have the collective answer--which is, after all, the reason for the Wrenches! And you are a wonderful bunch of folks!!!

HERE'S THE PROJECT

I'm scoping a project for the Forest Service that is likely to fund a solar charging station for electric boat batteries--this to encourage the use of electric trolling motors rather than obnoxious and polluting gasoline engines on a pristine alpine lake. This project is particularly exciting, in that it would bring solar technology to a lot of people, as this is a highly-visible location. We're also looking at including enough capacity so that the local concessionaire could provide ice (hmm, for fish or for beer?). This is another opportunity to give PV visibility.

The idea is to provide around 6 money-operated lockers in which one places their deep cycle battery, hooks up terminals, and comes back so many hours later to collect the charged battery. Numerous challenges exist, including: 

1) Make the system safe and fool-proof. The battery clips need to be able to be shorted and reverse-polarity protected. If there are two possible ways to hook something up someone will figure out four! 

2) Have a clear indication that things are hooked up right and that charging has begun (red light, flashing green light or such). 

3) Have a clear indication that the battery is charged (green light or such). 

One aspect I'm scratching my head over is what the best charging method would be. I vastly prefer using off-the-shelf components than custom circuits, and DC-DC conversion where possible. I wonder whether it might make sense to use a small (reverse polarity protected, charge status indicating) PV charge controller for each battery to be charged--all supplied from a considerably larger PV-charged battery bank at a higher voltage. In this case the main battery bank might look like a PV array to the charge controller.

Do you know of a PV charge controller that:

1) Will accept a bit over 30 volts (i.e., 24-volt nominal main battery charging system, with room for EQ).
2) Has indicator lights as to when it is correctly connected--i.e., is charging.
3) Is reverse polarity protected.
4) Is short-circuit protected.
5) Indicates when it is fully charged.
5) Is very reliable.

It looks like the RV Power Products Solar Boost 2000E addresses the above, though this controller runs up to 25 amps, and is limited to 30 volts. We need way fewer amps (around 6-10 sounds good per trolling battery), and likely need a bit over 30 volts (EQ on a 24 volt battery bank). Too, the cost for six individual Solar Boost 2000E controllers is probably beyond what could work.

Does this system make sense? Any other ideas? 

I'd like to keep the main battery bank at a voltage that would still allow the connection of a grid-tied inverter, as we'd need to pull out the system before the winter snows, and would like to do a grid-tie at a Forest Service facility in the off-season. We're also looking at public service work with the trailer when it is "on vacation."

One other idea might be that folks buy two deep cycle batteries, and need to have one battery in the box and charging by morning so that it charges during the DAY, rather than the night (i.e., we lock out the system at night with a timer, and can reduce the battery bank size). Asking folks to change this much, this fast, might be a deterrent, though.

Your thoughts on this project would be greatly appreciated! 

Thanks, 

Gary

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                     ~ Windstream Solar ~
     Gary Higbee  (gary at windstreamsolar.com)
                     (541 ) 607-1818 (Eugene)
                        (541) 954-3881 (Cell)
Solar, wind, and hydro site analysis and system design
    Components dealer and installation assistance
 Energy Trust of Oregon contracted system inspector
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[Non-text portions of this message have been removed]

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