Now that I have my SOTA radio and portable antenna setup working. Portable power options were the next item on my list. The 817nd has internal rechargable batteries, and can use AA batteries also, i have 2 battery trays for AA rechargeable batteries and the internal Ni-Mh pack, but for extended 5w operation portable, an external 12v+ source provides the best experience.
The remote control car/helicopter/aeroplane hobby scene has been a boon for hams. Modern high capacity batteries are both light and powerful, and this is the path I have gone down. a little more expensive than GelCel batteries, but much lighter for the power density. For a little more technical detail, visit VK1OD‘s explanation.
The most common type of RC battery pack these days is the Lithium Polymer (Li-Po) pack, these can be a little unstable and even dangerous, often catching on fire just because they can, especially when being charged. The Li-Fe pack is a little more stable, but still needs some care when charging and in transport. The Li-Po packs have a higher cell voltage and are less suited to portable ham use, but can still happily drive the 817nd.
I ended up with a LiFePo4 4 cell 8400mAh battery with a nominal voltage of 13.2v. The battery weights just over 1kg. I ordered the battery and charger on sunday, and it arrived from sydney via HobbyKing wednesday morning. There have been comments on a number of forums that this supplier can be a bit slow in delivery (and most times thats related to using the international warehouse), in my one experience, the australian warehouse and time taken was good.
The items came packed in a small box and well wrapped/protected, I got the special Li-Po/Li-Fe charger to allow mw to correctly charge this battery, a fire proof pouch for charging and transport (just to be safe). I also got some small plug in battery monitors, One has a low voltage alarm notification, the other is a digital Volt meter device that plugs into the monitor port of the Li-Fe battery and shows single cell voltages and the total device voltage in a cycle. These batteries can also fail if the cell voltage falls below a critical value.
A list of the items I purchased
My next tasks involve modifying the connector’s on the different items, replacing the RC car connectors with Anderson power pole connectors and some fuse protection to match my other equipment, and of course, a test operation, most likely this coming weekend 😀 – with the hamfest in ballarat, i hope to visit the two local mountains while I have day release.
Now that the cables are modified up, I set about charging the battery. I used the balance charge feature, and its taken around 2hrs to bring the 4 cells up-to the 3.6v full value from the shop (they arrived at 3.3v, that is the storage voltage. The charger was initially a little flakey and kept telling me the input voltage was too low (its connected to my big ham 13.8v supply) i suspect the device was suffering for getting hot rather than not having enough power, I lowered the selected charge current (from 3amps to 2amps, i was a little impatient) and it has been fine since, the current drops off as the voltage nears the full value. Below shows the setup, and the voltage monitor.