Mini Lipo Regulator

[Update 01 July 2011 - PLD-BAC-55 (5.5V), and 5.5V PLD-ESJ6 are subject to a recall notice - the low voltage alarm does not work correctly. I cannot give it my whole hearted recommendation until this is fixed.]

Finding reliable NiMH battteries for DLG models is not easy. Eneloop type (low self discharge) batteries are not available in the small sizes we use, and the regular NiMH cells are not always very reliable. I've purchased a number of packs with open-circuit cell voltages below 0.8V, indicating that they've been stuck on the shelf for months if not years. Packs delivered in this condition will never reach anything like their rated capacity so the kindest thing you can do for your model is to bin them.

One notable exception has been Kan cells. I've had a couple of their 350 and 400 mAh packs and they've lasted a couple of years each. (Incidentally, Kan are the only manufacturer I know who print the manufacturing date on the sleeve, making it more difficult for dealers to pass off stale stock.)

Unfortunately the supply of small-capacity Kan cells appear to have dried up here in the  UK, so when my last pack finally gave up the ghost, I decided to forego NiMH cells, and look for a Lipo + regulator solution.

After a bit of reseach on the net, I alighted on the Hyperflight web site which specialises in DLG and electric items. Twenty-four hours later I found myself in possession of:

• Lipo battery: Rhino 360 mAH 2S
• Regulator: 5.5 V Lipo linear regulator + LED flashing meter + low voltage alarm.

The old: Kan 400
The new: Rhino 360 Lipo + 5.5V regulator

Installation
The combination of battery + regulator take up a little more space compared with the old Kan pack. However the new combo is actually a little lighter at 27 g (21g for the battery, 6g for the regulator) compared with 33 g.

LED voltage readout
The regulator incorporates a high power LED which flashes the battery voltage. Long flashes for the number before the decimal point, then short flashes. So for example 8.1 volts is: FEEP FEEP FEEP FEEP FEEP FEEP FEEP FEEP... FIP. It's an easy way of checking the state of the battery both before and during a flying session (the flashes are easily visible through the slightly translucent fuselage of the Longshot). [Note: with units affected by the firmware bug, it's the only - albeit perfectly satisfactory - way to check the battery voltage].

Audio alarm
An audio alarm sounds is supposed to sound when the battery voltage dips below  7V. Unfortunately the firmware on my unit has a bug, and the alarm does not work as it should (it only sounds when powering up with an already depleted battery). I will update this section once the unit is fixed.

Goodbye Nims
Firmware bug aside, the lipo battery + regulator has worked very well for me. It's a little more awkward to install, but (a) no need to scrabble around for small NiMH packs, and (b) the low voltage alarm (with newer firmware) will be a useful safety feature. The regulator is of the 'linear' type, and I have had no Rf  issues using my 35 MHz Cockpit SX.

And of course Lipo cells have a low self-discharge rate, so you can carry a spare pack without worring about constant topping up.

Finally, Hyperflight have been pretty good at getting stuff to me quickly on the two occasions I've ordered, and their tech support is good too. I place a high value on good support when it comes to stuff which keeps my models flying safely.