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Date:         Mon, 15 Oct 2012 07:09:08 -0700
Reply-To:     Alistair Bell <albell@SHAW.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Alistair Bell <albell@SHAW.CA>
Subject:      Re: doc wattson or watts up?
Comments: To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
In-Reply-To:  <BAY152-ds779AD5154C827F5167E6FA0710@phx.gbl>
Content-Type: text/plain; charset=windows-1252

so dennis, to cut to the chase, with a 75A current going thru the meter there will be 28 W of heat produced?

The thing is, I am considering one of these meters to monitor the drain on my aux. battery which is only a 31 A/hr capacity unit. the meter would be located at the downstream side of the battery, at my aux fuse panel and would only see/read the loads on that aux battery. My aux battery is separated from the van's charging system when ign key is off by an ACR. During camping it would not see anything approaching 75 A, as there is nothing on the circuit that it supplies that comes any where near that kind of current demand. Nor would it see the charging current.

But back to my original question, I wonder if anyone has actually used one in their van and can tell me how it worked out?

alistair

On 2012-10-14, at 10:29 PM, Dennis Haynes wrote:

> 7.2 Maximum Current Capabilities > Current flowing through Watt's Up and its supplied wires generates heat due > to the > resistances of the wires and of the precision internal current shunt used > for current > measurements. Though very low ( ~ 0.004 Ohms in 14 gage wires and 0.001 Ohms > in > shunt), these resistances are finite and at high currents the heat generated > becomes > noticeable. This is because heat is created with the "square" of the > current. I.E.: > heating power (W) = current2 (A) ´ resistance (Ohms) > So doubling the current increases the heat produced four times. > At 75 Amps, approximately 28 Watts of heat is produced – mostly in the > Watt's Up's wires. > This doesn't only happen with Watt's Up. All wiring, connectors, etc have > resistance > subject to the same resistance based heating. > The high current handing capabilities of Watt's Up will be maximized when > the Watt's Up's > SOURCE and LOAD wires are kept short and cool. Cut the wires as short as is > convenient > for high current operation. A fan blowing over the wires will help their > cooling. At > moderate currents there is little heating. Using a "three-wire" connection > will also lower > heat generation. Please see our Internet website connection diagrams and FAQ > for more > information on connections. > > Keep in mind the charging current of the battery. Could be somewhere between > 15 and 30 amps assuming group 41. Larger batteries and AGM can absorb even > more if the wiring and alternator can support it. > > Dennis > > -----Original Message----- > From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of > Alistair Bell > Sent: Sunday, October 14, 2012 11:34 PM > To: vanagon@GERRY.VANAGON.COM > Subject: Re: doc wattson or watts up? > > I didn't see the voltage drop you mention, but did note that the unit's > current draw is 7mA (which is less than my stereo head unit even with face > plate off). > > I don't have any problems with the gauge of wire used, my westy does not > have a very demanding electrical power requirement when camping. Lights are > LEDs, back of fridge fan I have is less than 1A, the water pump is > intermittent 2.5A, I guess the stereo is the biggest constant draw, but I'm > guessing it is 5A or less most times. > > alistair > > > > > On 2012-10-14, at 7:05 PM, Dennis Haynes wrote: > >> http://www.powerwerx.com/techdata/Watts-UP-V2.pdf >> >> Note the voltage drop-power consumption of this device. >> >> This device is mostly designed for the Radio Control (RC) car, plane,

>> boat, helicopter hobbyist. While it can take 50 amps this is for a >> source that will be depleted in minutes, not hours. All the current

>> going in/out of this device is connected with those 14 gauge wires,

>> normally used for 15-20 A/H loads. This can be a good test device but

>> I would only for limited load/charging current currents. >> >> Dennis >> >> >> -----Original Message----- >> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On >> Behalf Of Alistair Bell >> Sent: Sunday, October 14, 2012 7:06 PM >> To: vanagon@GERRY.VANAGON.COM >> Subject: doc wattson or watts up? >> >> I think I might have posted about these meters some time ago, I'm sure >> I mentioned them to Mark D. I'm wondering if anyone has bought either

>> of them and if so what their thoughts are after some use. >> >> http://www.powerwerx.com/digital-meters/doc-wattson-meter-dc-inline.ht >> ml >> >> I'm leaning towards buying the doc wattson model. >> >> alistair >


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