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Date:         Sun, 6 Sep 2009 11:44:02 -0700
Reply-To:     Keith Hughes <keithahughes@Q.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Keith Hughes <keithahughes@Q.COM>
Subject:      Re: vanagon Digest - 5 Sep 2009 - Special issue (#2009-747)
In-Reply-To:  <BAY0-PAMC1-F5rDxSiz00036efb@bay0-pamc1-f5.bay0.hotmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

> Date: Sat, 5 Sep 2009 15:42:28 -0700 > From: Rocket J Squirrel <camping.elliott@GMAIL.COM> > Subject: Re: Run time to charge Aux battery > > Here ya go: > > http://www.sterling-power.com/products-altbatt.htm > > They promise: > > * Charge your batteries over 5 times faster > * Input an extra 50% extra power into them plus de-sulphate the batteries > * Make them last longer > > That there puppy takes the output of your alternator and splits it into > two outputs: the first is designed to charge the starter battery, the > second is a multi-stage deep-cycle charger with equalization stage. > > The 80 Amp model is a mere £290.99 > > Connect it up to your alternator and your deep cycle and up the rpm's a > bit and that thing will suck on the alternator as hard as it can to pump > power into your deep-cycle batteries. > > If ANYONE tries this thing, I'd like to hear about it. Interesting. I have my doubts about their claims, however. I can believe that it's effective for de-sulphating, but am really suspect about their claims relative to bulk charge rates. Irrespective of the output voltage, the unit is limited by the power (amperage essentially, since they load adjust to keep the voltage constant) supplied to it from the alternator. For a heavily sulphated battery (high internal resistance), the increased voltage is going to really jump up the charge rate, but on the flip side, for moderate discharge/recharge cycles, I'd suspect that the losses from the conversion process would cost more (alternator load and thus fuel usage) than you could gain, unless absolute minimum recharge time is of the essence. With a stated duty cycle of 86%, and likely no higher than 80% conversion efficiency (on a good day) the actual system efficiency is likely in the range of ~69%. That 30+% loss of efficiency has to be overcome by more burned gasoline, idling or not. And it will put a much higher load on the alternator at low speeds than it is designed to handle.

Now, if you have a 200A or 300A Balmar-type large frame alternator (what these things are designed for), mounted on a rev-limited low speed diesel (where the alternator spins *much* faster at idle than your Vanagon alternator will), probably works very well. You notice how they don't show engine/alternator RPM in their charts? And they specifically state that the system forces the alternator operate under Full current output conditions, so maximum heat is generated under minimum (idle) cooling conditions. Recipe for bar-b-que'd alternator IMO if you want an "idle charger".

But if someone's got $560 burning a hole in your pocket and wants to try it, I'm all ears about the results!

Keith Hughes '86 Westy Tiico (Marvin)


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