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Date:         Fri, 6 May 2005 11:05:37 -0700
Reply-To:     Alistair Bell <albell@UVIC.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Alistair Bell <albell@UVIC.CA>
Subject:      Re: Adjustable voltage regulator
Comments: To: jbange <hfinn@INGRATES.NET>
In-Reply-To:  <6.2.1.2.2.20050506101135.04356a00@66.51.205.14>
Content-Type: text/plain; charset=US-ASCII; format=flowed

I would add that if the stock charger is putting out less than 13.8 volts (at source) then the battery *may* not be becoming fully charged. This would be even more of an issue for gel cell batteries as they like a higher charging voltage.

Alistair

On 6-May-05, at 10:29 AM, jbange wrote:

> Isn't the amperage output of the alternator just as important or more > important than the output voltage, as long as the voltage is higher > than the > battery voltage would be at full charge? If you've got quite a load on > the > battery, i.e. lights, heater or a/c, trying to charge an aux. battery, > even > if your voltage is close to 15 from the alternator, if your alternator > amperage capacity is not enough, will an adjustable regulator really > help? > On my battery charger at home, it is adjustable between 10 and 30 > amps, and > the voltage fluctuates up to a little over 14. What's the real story > with > amperage versus voltage?

Well, the short answer is that volts should remain about the same all the time. A good beginning analogy is to think of it as plumbing. Voltage is like water pressure. Too much voltage will burn up sensitive electronic devices just as too much pressure will bust fitting in the faucets and valves. Your alternator needs to put out electricity at a higher voltage in order to overcome the internal voltage of the battery. Amperage is analogous to flow rate (e.g. gallons-per-minute). All the stuff hooked up to the alternator will draw a certain amount of amperage. Just like having too many showers running will cause your water pressure to drop, if that total amperage draw is higher than your alternator can supply, the voltage will drop. Of course, no amount of money will get you a voltage regulator that'll prevent this drop. The "ampacity" of your alternator is the deciding factor. Now as far as fancy voltage regulators, it might be worthwhile if you've had trouble with the stock one built into the alternator, but if you haven't had any trouble, why bother? Unless you're seeing a big voltage drop between the alternator and the battery due to resistance (analogous to water pressure loss due to friction in the pipe), I can't imagine why you'd NEED to adjust your regulator. Even then, I'd put in thicker gauge wire (bigger pipe) and check my return paths before I'd go and crank up the voltage...


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