On 7/12/2005 12:32 PM Otmar wrote:

> At 11:40 AM -0700 7/12/05, Michael Elliott wrote:
>
>> Thanks, Doug
>>
>> 2.5A in freezer mode running, like, 24 hours a day is 60 amp-hours. That
>> would quickly deplete my aux Optima 50Ah battery unless I added a lot of
>> supplementary recharging.
>>
>> But I know that these reefers do not run 100% of the time. Someplace,
>> somewhere, I saw a spec page which provided typical duty-cycles. Can't
>> find it now. And I don't plan to run freezer mode, just below 40F.
>
>
> I have a copy of one here:
> http://www.evcl.com/vw/Accessories/MT45F%20curve_jpg.pdf
> A bit fuzzy, but the data is there. Ambient temps across the top, and
> Cabinet temp on the left. The curves just show how long it takes to
> get to temperature.
> For instance, the top left one shown that at 25 deg outside air temp
> and +5 deg C cabinet temp (fridge mode) it draws and average of .54
> Amps. They show it as .54 amp hour per hour.

It is pretty fuzzy, but if I squint my eyes just right, I can make
believe I can read it! It appears that with outside ambient of 35C
(95F), and internal temp set to 5C  (41F) , the duty cycle settles to
47%, leading to an average draw of 1.14A.

So with a 50Ah battery (deep cycle, should not use more than 80% = 40Ah
max), this reefer will draw 27Ah over a 24-hour period. Of course,
nighttime temperatures are lower -- or will be any darn place /I/ ever
camp! -- so less current consumption can be expected. Maybe 20Ah . . . .

This tells me that I need to assure that the charging technology I
select (generator? solar? generator? solar? I go back and forth on this)
needs to be able to provide probably more than 20Ah a day for reefer use
only. Add on DVD and lighting and a couple other parasitic loads and I'm
looking at 30Ah.

Seems doable. I need to focus now on where the recharging comes from.

<snip>

>
> The only drawback I find is that I like it very quiet at night, this
> is not super quiet. Even putting it outside the van still makes
> noticeable noise, though not much. My opinion is that the
> "swingmotor" is no quieter than a normal compressor fridge. It's hard
> to beat the Vanagon Fridge for night time quiet.

Darn. I was hoping this design was quiet. Pity there isn't a propane
unit with backup swingmotor to take over during the day.

--

Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
Carlsbad, CA
KG6RCR