Wednesday, Apr 21, 2004 at 19:44
William, yes, yes, yes, etc
I was half-expecting to get howled down on this one.
If the solar system has the battery already charged at (say) 14.2v, then the electronics of the alternator stops the alternator charging. So what? It stops charging coz the battery is already high enough in voltage, just what it's supposed to do. When the volts drop below the alternator threhshold, the alternator just starts charging again. Easy as that.
Re the risk battery volts going to 15v, I could not believe that an automotive electronics designer would create a system, including the ECU, which could not take 0.5v above its normal max of 14.5v. I quote 15v, since some intelligent solar chargers do take the battery briefly up to 15.0v before dropping back to about 14.2v, otherwise the simpler regulators run at 14.0-14.5v. Some automotive alternators (esp on diesels) run at 15v anyway. It's just not a problem.
Do not be put off by the fact that the solar panels put out about 22v open-circuit. This voltage drops right back to the battery voltage due to the low internal resistance of the battery and the high internal resistance fo the solar panels. If the battery has a high internal resistance, such as when it's flat, then the solar regulator immediately cuts off the panel the moment the volts reach 15v max. Having said that, I would never connect a solar panel directly to a vehicle battery without a solar regulator.
Re running batteries flat, the regulator _Affordable_Storage_Drawers.aspx minimal power from the battery, like a few milliamps. This just could not run a battery down even if left with total darkness for weeks. I mean, these things are fitted to battery banks on unmanned radio sites for years on end without a problem.
Gerry
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