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Posted by: Mike KW1ND Posted On: 12/31/03 Subject: Re: Connecting Solar Panels Message Posted: In Reply to: Connecting Solar Panels posted by Steve / W9HC on 12/31/03 If a battery is going to be left connected to a photovoltaic (PV) module without any type of controller, a common rule of thumb is to use a module rated at no more than 1% of the battery's amp-hour capacity; e.g. use up to a 1 amp (peak) output panel on a 100 AH battery. This is a pain, and rarely done. For your case, always use a battery - it will, as you mentioned, act as a big "capacitor," allowing the rig to operate at a fairly constant voltage level, or at least at a slowly changing one. I have read of hams using zener diodes and PV modules directly connected to rigs (to clamp off any high voltages), but this is full of potential problems. (What if it gets cloudy? The panel also has to be carefully matched to the rig as well). Easiest & safest route: hook the module (parallel if multiple modules and the extra current is really needed - I don't know the rating on the Volkswagen modules) directly to the battery, and the rig directly to the same terminals on the battery. Or something similar with pigtails, etc. True, the module(s) are directly connected to the rig, but also to the battery which will load the module(s) down, reducing their output voltage, and smoothing the power flow to the rig. If the module(s) are putting out more 'trons than you're burning up with rig operation, monitor the battery voltage (either with a DMM or some rigs have internal meters, like the K2). If you're using an SLA (gell cell), keep it below 14 - 14.4 volts (check the specs on your battery to be sure). If your module(s) don't keep up, monitoring battery voltage isn't necessary - the sun is just prolonging your operating time. For a nice, small, no RFI charge controller to eliminate all worries (or leaving the battery connected to the module for long periods of time), check out the Micro M+ at http://www.seslogic.com/sunlogic.html I have an older version and it works great. No connection, just a happy customer (and the owner is a ham, and has had several articles in QST & the Handbook over the years). And there's a long-winded answer to your short question ;-) 73 Mike KW1ND |
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