Date: Mon, 6 Sep 2004 20:37:05 -0700
Reply-To: Vince S <gipsyflies@COMCAST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Vince S <gipsyflies@COMCAST.NET>
Subject: Re: 12v Aftermarket Coolers ? Any Good?
In-Reply-To: <001101c4945e$bb999de0$c200a8c0@vsovaio>
Content-Type: text/plain; charset="us-ascii"
Simplistically 52AH battery means you can draw 1A for 52 hours or 5.2A
for 10 hours. However the characteristic of lead acid battery is much
more complex than that as it depends on the temperature, load current
etc. The rating is performed under some standard test criteria which I
am unfamilar with and too lazy to look up. In pratice I will take this
number with just as a guide and discount it a bit and further as the
battery wears.
Your calculation of the Coolmatic cooler are correct. Note that all
these coolers uses the same Danfoss DB35F compressor but they have
different wattage. This compressor RPM is set with a series resistance
with the thermostate and hence the current consumption.
I'd really like to get one of these and try them out. They claim to be
extremely quiet.
- Vince
http://gipsyflies.home.comcast.net
1989 Vanagon GL Camper
1993 Mazda Miata (for sale)
1996 Land Rover Discovery
2005 Mini Cooper S
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Vince S
Sent: Monday, September 06, 2004 3:13 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: 12v Aftermarket Coolers ? Any Good?
Mike,
Though not an answer to your question. The Blue Water Sailing review on
the Coolmatic cooler says that it cycled only 12 to 15 minutes per hours
when operating in the sun. That means it only need 45W/4. Just over 11W
because the insulation is so good. Note that Coolmatic also have a
thermo blanket option.
The key is good insulation, in addition to very good/efficient
compressor technology.
- Vince
http://gipsyflies.home.comcast.net
1989 Vanagon GL Camper
1993 Mazda Miata (for sale)
1996 Land Rover Discovery
2005 Mini Cooper S
-----Original Message-----
From: Rocket J Squirrel [mailto:j.michael.elliott@adelphia.net]
Sent: Monday, September 06, 2004 3:04 PM
To: Vince S
Cc: vanagon@GERRY.VANAGON.COM
Subject: Re: 12v Aftermarket Coolers ? Any Good?
Vince S wrote:
>Sorry I meant Danfoss from Denmark. Coolmatic is one cooler with these
>compressor. There may be other cooler with other compressors that may
>be cheaper.
>
>http://www.waeco.com/pages/products/mk/cmkbov_truck_d.htm
>
>
>
Hmmm . . . I'm wanting to learn how to translate deep cycle battery
ampere-hour ratings into real world performance, and these reefers seem
like a good exercise.
Assume we are using a fully-charged deep-cycle battery, like an Optima,
rated at 52Ah (C/2) / 65Ah (C/20) to run the reefer. Also assume its a
hot day, 32C. Finally, assume that there is some nicely chilled lager in
the reefer that we would hate to see get warm. Here are the data for two
of the Danfoss reefers:
Danfoss CDF-35 "incredibly inexpensive" 31 liter model. It is rated at
45 watts, and has an average running time: of 30% at 32C ambient
temperature. Its rated power consumption is defined as power input x
average running time. For this model, then, we are talking 30% of 45W,
or 13.5W ~ 1Ah.
Danfoss CF-25 (not-so-incredibly-inexpensive) -- their smallest model.
25 liters, average power consumption: 35 watts, average running time:
19% at 32C ambient temperature. This translates to 6.7W, ~560mA.
For these two models, then, how long before the compressor stops
chugging?
--
Mike "Rocket J Squirrel" Elliott
71 VW Type 2 / 84 Westy: A poor but proud race.
KG6RCR
