As readers of the reflector and active users of SOTA Watch are aware I was let down by my two brand new LiPo batteries when I had set myself up for an HF activation of Birks Fell G/NP-031 on Tuesday.
The two EC Power 14.8v 5000 mAH batteries were purchased from bulk-verhauf in Hong Kong on e-bay at Xmas. I also purchased the Imax B6AC unit to charge them with, these were Xmas presents from my XYL.
On Birks Fell on Tuesday in lying snow at an air temp of -3c the LiPo’s would not even turn on my FT-857. The LiPo’s were outside my rucksack and lying on a nylon bag.
I did not have a multimeter to check the LiPo’s voltage and the rig would not turn on to provide a readout of the supply voltage on the display. After packing up and returning to the car near Redmire Farm at 10.45am, the temperature was 0c and the LiPo cells would still not do the job intended. My 7 AH SLAB in the car proved that it was indeed the LiPo’s that had failed and not the radio.
When I returned home the LiPo’s worked fine in the warmth of my shack.
Testing has been minimal so far. I left one of the LiPo batteries outside for two nights in a plastic bag. It has now warmed up so the minimum temperature was 1.7c overnight. The LiPo worked fine when I brought it in after lying in a temperature of 3c. I need more cold weather before further testing can be conducted.
What I am also going to do today is determine how much time I can get out of these batteries by cycling them with the FT-857 set up at 50w as a CW beacon transmitting for 15 seconds TX and 15 seconds RX whilst monitoring the battery voltage until the rig refuses to function on transmit. I will measure this with a fully charged LiPo that has been in the warmth of the shack (approx 16c) and then I will compare this will a fully charged LiPo that has been left outside in overnight temperatures and compare performance. I also want to determine at what temperature the LiPo cells stop working, so it may take some time to determine that whilst I wait for outside temperature variations.