Date: Mon, 15 Oct 2012 01:29:30 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: doc wattson or watts up?
In-Reply-To: <EC6A626D-C70E-4C01-904E-E68EBC3F555F@shaw.ca>
Content-Type: text/plain; charset="iso-8859-1"
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
