The cost of this high capacity pack is ~$190 with a MAHA charger and it requires some soldering skills. I've been using three of these packs with several recorders for over two years including the Sound Devices 722 and 744. They'll run the SD decks for 12-15 hours continuously. Additional packs are ~$85 each, which is considerably cheaper than ready-made packs you can buy commercially.

HiRose #HR10-7P-4P Digikey #HR100-ND

12 volt DIY Battery Pack using 10,000 mAh D Size Batteries

for use with Sound Devices 722 & 744 Recorders. Rob Danielson. 9-5-05











(1) Batteries

You'll need ten cells, I recommend the10,000 mAh, D size NiMH, rechargeable cells
1- 8 pack
2 - singles
~$65 total

(2) Battery Sleds

You can mount the 10- D cells in 2- four-slot and 1- two-slot battery sleds:

2- Four Slot "D" Sled Catalog #: 270-396

1- Two- Slot "D" Sled Catalog #: 270-386

After wiring the sleds in series, you can strap them together with strong tape and slip them into the cardboard box the batteries are shipped in.

(3) 722/744 HiRose Connector

The external power connector to the 722 or 744 is a 4 pin HiRose Connector: #HR10-7P-4P. The Digikey part# is HR100-ND. You can order them, online, by inserting, "HR100-ND" under parts search on the Digikey website: They're about $12 each and with an order of two to meet the minimum + Shipping comes to ~$30.

(4) Wiring the HiRose Connector

Pin 1 is negative and Pin 4 is positive.Should you wire the polarity backwards by mistake, the 722 and 744 decks ignore the pack altogether, The 722 and 744 will run on 10-18 volts DC, but the MAHA charger I recommend is designed to charge battery packs no greater than 12 volts. .

For the cable between the battery pack and the HiRose connector, I recommend a length of round rubber jacketed cable 3/16" diameter. The pins in the connector are very small so take your time. The weight of the 722/744 can end-up resting on this plug/cable, so make sure that HiRose's compression fit squzzes firnly around the rubber jacket.

(5) In-Line TAMIYA Connectors for the Charger and Quick Field Disassembly

The MAHA charger I recommend has a femaleTAMIYA ouput connector on the back, so I suggest adding a male/female pair of these TAMIYA connectors about 18-36" from the HiRose connector so you can remove the battery pack from your rig and slip on another battery and have the right connector on the battery pack for your charger. The TAMIYA connectors are popular among RC folks so RadioShack usually has them in stock:

Attach the male TAMIYA connector to the cable that goes to the battery pack and the female TAMIYA connector to the cable with the HiRose connector. In the below picture, the male is the one on top. (sigh).

(6) The Charger

High Capacity NiMHBattery packs are tricky to charge. I've played with three DIY designs that didn't work very well, so I finally spent $95 on a MAHA MH-C777Plus-II Analyzer/Charger which was well worth it.

This charger can charge almost any battery or battery pack be it nicad, nimh, or lion and very quickly and reliably. It will also test and recondition single cells and packs to extend their life.

I usually charge the packs two complete times before using them the first time. The MAHA charger will indicate that the charge is complete at about 1/2 capacity. There's a magnetic heat sensor that comes with the charger that can be attached to a battery, but I haven't found it necessary as the MAHA monitors the charge and changes to a trickle charge before over-charging, at least so far! These are large capacity batteries. Even after they have been charged once, I add another "quick charge" before I head into the field which can take from 4--8 hours.