At 12:05 PM +0000 5/18/08, tempjez wrote
>'When its crucial to record for more than 20 minutes, I power my
>744T on an external battery pack and use the internal battery as
>back-up. My 744T runs much longer on 15 volts than 12. You can also
>set the "shut-off" voltage lower, like 10 volts when you use the
>external DC input. I hate to keep buying those $70 batteries and
>watch them become unpredictable. Personally, I think NiMH batteries
>have more consistent output after 30 cycles up to around 100. They
>are heavier, though. Rob D'
>
>I'd really appreciate some basic advice on the powering of SD
>recorders (please keep it very simple & make it readable for folks
>who have no previous experience with anything other than standard AA
>batteries - I ask this because i'm finding that different people on
>here mean different things when refering to 'external batteries' &
>some have mentioned non-Li-ion batteries but don't provide info on
>the exact battery needed & possible links to web pages that feature
>these / where they can be purchased etc.)
>
>Also, it seems that lots of folks hardly ever record by using the
>mains power & I wondered if anyone had any experience with this -
>any problems etc ?
>
>ta,
>Jez
>
Hi Jez--
Until you have a good understanding of external powering, its
probably wise to stick with the batteries SD recommends. Most
recordists do.
Maybe someone knows of a commercial battery pack with the correct
connector for a SD 702? A company like Location Sound Recording might
make one for you for,... ~$400? There are probably several list
readers who will order the parts and solder on the connector for a
labor charge too, if you want. :-)
For folks who have a multimeter and can solder, there are quite a few
battery specialist vendors on line who can help you make a 12 volt
battery pack. The bottom seven on this dealer's page (4500 mAH or
larger) look fine:
http://www.onlybatterypacks.com/items.asp?db=3D37
You also need to buy correct power connector for your 702 (check the
SD manual for type and pins to use) from an electronic parts supplier
like http://www.digikey.com/ The pins are small and take some
soldering skill.
You need a battery pack charger too, like
http://www.onlybatterypacks.com/showitem.asp?ItemID=3D11115.12 or
http://www.onlybatterypacks.com/showitem.asp?ItemID=3D11502.12
Here's a page describing my DIY external battery pack/sled and
connecting it to a 744T.
http://www.uwm.edu/~type/audio-reports/BatteryPack_NiMH_722/Battery10KaHr_7=
Message: 22_744.
Subject: htm
The page needs updating and elaborating. I now use 11 or 12 X 1.2
volt NiMH cells. Its advisable to wire the Hirose connector so the
external battery will not charge the internal battery.
You can use C or D size cells-- rated 3500 mAH or higher. Ask the
battery supplier about the correct charger to use rather than buy a
MaHa charger unless you have a lot of specialized batteries you need
to maintain.
There's much more discussion on this topic in the list archives too
http://bioacoustics.cse.unsw.edu.au/archives/cgi-bin/namazu.cgi?query=3DSD+=
external+battery+pack&submit=3DSearch%21&idxname=3Dnaturerecordists&max=3D2=
0&result=3Dnormal&sort=3Dscore
Rob D.
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