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Date:         Sun, 4 Mar 2012 23:02:11 -0500
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: Second battery in Westy
Comments: To: The Bus Depot <vanagon@BUSDEPOT.COM>
In-Reply-To:  <0d1d01ccfa62$421c6d40$c65547c0$@com>
Content-Type: text/plain; charset="UTF-8"

A relay is usually the best solution. But the relay and related wiring needs to be sized for the job. If a load is connected to the circuit during charging the circuit has to carry that load with minimal voltage drop. Using 12 gauge wiring to charge a battery while a 30+ amp load such as stereo, inverters, etc. are also connected you can end up with all sorts of problems.

Dennis

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of The Bus Depot Sent: Sunday, March 04, 2012 6:55 PM To: vanagon@GERRY.VANAGON.COM Subject: Re: Second battery in Westy

> Again this kit is limited in supporting loads connected to the aux battery.

The issue isn't actually the load per se, as that's a function of the battery that is attached to it. More accurately, it is the recharge rate once the camping battery is depleted. (Put differently, high load is fine, as long as you allow enough recharging time between uses.)

A relay solution has several inherent advantages over a diode based isolator system, which is probably why VW/Westfalia opted for that approach:

1) There is no voltage loss, as opposed to a diode based battery isolator, so the battery always charges at full voltage

2) In the event of a failure, this type of setup will typically fail in the "open" position, meaning that while the camping battery will not recharge, the starting battery will not be drained. In such a scenario, the fuse may pop and your auxiliary items will still work, but once the camping battery dies the aux battery won't charge until you replace the fuse. By comparison, a diode-based isolator system will typically fail in the "closed" position, meaning while you are camping, unbeknownst to you your starting battery is draining. You learn this the hard way when you can't start your Vanagon at the end of the weekend.

3) Cost/Complexity

The downside is that a relay setup recharges the camping battery slowly, not quickly. For most Westy owners (who largely use the battery for intermittent lighting, moderate volume music playing, etc. over a weekend followed by a bit of driving before the next use), it is more than sufficient. But if you are using high-drain devices (such as a monster sound system at high volume for long periods of time), followed only by short drives before you begin draining the battery again, then your camping battery may not fully recharge between uses and a more aggressive solution will better suit your needs.

- Ron Salmon The Bus Depot, Inc. www.busdepot.com (215) 234-VWVW

_____________________________________________ Toll-Free for Orders by PART # : 1-866-BUS-DEPOT


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