The B6AC said 2055mA to recharge, so plenty of capacity in hand. That’s 48 QSOs, several unsuccessful calls and quite a bit of listening around. The rig runs 5W, but is probably somewhat more efficient on receive than the 817. Unfortunately space was at a premium and I only took 2 lengths of wire to make a 20m dipole / vertical. I deployed the lengths joined as an inverted L without any more than a tent peg for an earth and the rig only gave 1 watt out on 40m, Nevertheless that secured me some excellent QSOs including a pleasant chat with Iain GM4HBG in Forth, Lanarkshire who was running a massive 3W. I also bagged a couple of summits on the band. 
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Yes, I was convinced my first LiFePO4 was faulty when i first tried it - voltage dropped from 14.4 to 13.4 in literally seconds when I used in on an '857 on receive… a bit of research then showed that the initial voltage drop actually only represented using a few milliamp hours of the total capacity, they go on for ages with very little further drop in voltage. Wondrous things 
To quote Top Gun really badly, ‘they don’t teach you that in flight school, do they?’
I just kind of relaxed into the batteries, regardless of the final charge voltage, because when you use them they just keep going.
I found with the FT-857 that when the voltage finally sags, when using 100w it could sag to below 10v, that the radio seemed to automatically throttle back the power draw on the finals, so it still functions and you appear to be transmitting, but the station being worked starts complaining about your signal strength.
Regards, Mark.
Yes and 20C is conservative, many LiFePO4 batteries are rated at 30C and will actually give a lot more than that if the resistance in the external circuit is low enough, even if only for seconds. We’re talking the possibility of molten metal projectiles here…
I go for belt and braces - not only do I put a fuse in the battery lead between the wire coming out of the battery and the power poles for onward connection, I also put a fuse in the lead to the rig…
73 de Paul G4MD
With great power comes great responsibility…
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