Today I was supposed to be activating Gun, The Cloud and finally Shining Tor.
Starting off at Gun just over 20 contacts was made in 50 minutes.
I briskly made my way over to The Cloud where M1EYP was already activating.
After Socially distanced introductions and I must say it was a pleasure talking and learning so much in our short conversation. I quickly set up and managed to work 10 stations when my Icom handheld battery died on me. Not to worry I had the 857 in my bag.
Well how wrong could things go. I set up the 857 and connected the battery to no power at all. Everything I tried produced no results. I spent 25 minutes attempting to get on the air and then gave up.
I got home and checked the battery thinking it would be dead, to my surprise 100% in all 4 cells.
I tried to reconnect the battery to the rig and again no power. Strange. Ok so it must be the power lead. Wrong again, connected it to my power supply and the radio burst into life.
The only thing I can think of is the cable I am using to link the battery to the power cable is the same as the charging lead. The cables are thin though. I’m now thinking it may be this that is causing the issue. So I have ordered powerpole connectors all round, hopefully this will cure the issue.
I have also ordered another battery as this one had the rig at 16v in testing, maybe need some resistors to create the necessary volt drop for these batteries.
If anyone has any ideas please feel free to let me know.
I shall leave you with some photos of today’s activations.
On your question “If anyone has any ideas please feel free to let me know”. My thought as to why the rig failed to work on the peak but worked fine when connected to the mains PSU at home is that running an FT857D at 16.8V may trigger an over-voltage protection shut off or simply with out of range supply voltage the rigs “firmware” may simply not work as expected and hence the power-on button doesn’t!
To prove this put a load across the output of the 4S LIPO - make sure it’s a high enough power rating and resistance value resistor (CAREFUL! the LIPO can happily deliver over 50 AMPS!!!) and monitor the battery until it’s down to 13V - then disconnect the load and connect the FT857D again using the same leads that you used on the summit. If the rig then works - you’ve found the problem.
If you can’t find a large enough resistor, try a car headlight bulb 55w for example. Put the sun glasses on to start with, as it’ll be bright - and hot!
If that’s the case, for now simply never fully charge the LIPO - keep the combined cells voltage under 14v and then stop charging. You wont have the full battery capacity but you also wont be damaging your rig!
73 Ed
PS if considering one of the many Chinese “buck/boost” voltage convertors (invertors), my experience is that many can cause so much wide-band RF noise that it makes operation difficult. Others have found good ones that are RF quiet but there doesn’t seem to be any way to differentiate the good from the evil ones. I use a voltage regulator on a heatsink to reduce from 16+v to 13.8v but that voltage reduction is wasted in heat.
Finally getting to the issue with the battery just discharging them a little to test whether it’s the voltage. Seems the most likely thing at the moment though.
I hope you got plenty of more contacts today. The mini pileup from Japan was amazing to see.
Hi Ian,
When buying batteries for radios needing 12-14V the best option is the LiFePO4 chemistry. Their fully charged voltage is 3.6 per cell so 4 cells add up to 14.4. My radios happily run on that voltage. The availability varies though but you’ll find threads on this reflector discussing that. The search tool on the website is very good.
If you are stuck with the LIPO batteries there are several options used to drop the voltage to a safer level. Each radio has a rated safe voltage range, beyond which damage or self protective switchoff can occur. On most radios the final amplifier devices are connected to the input dc line at all times so even a momentary high voltage, if high enough, could damage those transistors. Fortunately modern power transistors are tolerant of 16 volts.
There have been many discussions on the reflector about voltage dropping techniques, some involve power diodes, others use inverters. Some loss of battery power occurs with all options as all have power loss or lower efficiencies than ideal. Beware cheap inverters, no over-voltage or failure protection.
Plain resistors have the disadvantage that the voltage dropped is proportional to the current through the resistor, as per ohms law. So the resistor that drops 2 volts when 1 amp is flowing will drop 20 times that amount with 20 amps, which is clearly impossible. The 857 may tolerate the voltage dropping to just under 12v but it will turn off when the voltage drops below a certain level. Even if you set the 857 to a low power level the current on transmit is over double the receive current and when you talk It increases and fluctuates. So a resistor is not the right solution.
There are lifepo4 batteries now being sold as replacements for the 7ah sealed lead acid battery, with internal battery management and cell balancing. They are a good option for the 857 as its higher standing current on receive and transmit will give limited operating time with the 4ah batteries. They are amazingly light.
Wish you well in resolving the battery issue. Powerpole connectors are highly recommended. Take care to adopt the standard polarisation. Readily available on powerwerx and other websites.
Hi Iain,
At least no permanent damage was done. I have operated an FT857 for many activations. My example will happily produce 100W with a supply voltage of 10.8 Volts, at which time the 3 cell LIPO battery is 80% discharged. To protect the cells this is my “drop down dead, stop transmitting” voltage.
If using LIPO’s, don’t over complicate things, use 3 cells not 4. The maximum voltage is then 12.6Volts, well in spec…
Lastly ALWAYS insert a suitably rated fuse in one of the supply lines. I use a 20A car-style spade fuse. In my case I operate with 2 X 5Ah batteries in parallel, 20A fuse in each line. Carry a couple of spare fuses just in case!
