Thanks Mark,
Much appreciated 
Are they all sold yet?
I’d expect 4.5hrs operation easily using mixed CW/SSB (with a speech processor) out of mine with an 817 on SOTA operations. In fact they last so long and have a flat discharge curve compared with LiPos that I forget to accurately observe how long I’ve been using one without charging it.
As Mark says for an 817, a 3S LiPo is just as good and now much cheaper. 817 will produce full output down to about 10.5V so they don’t need 13.8V the way some sets do. I used 3S LiPos for 9years and only bought 4S LiFePo as I could see my batteries were getting old and no longer olding up so well.
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I have two 4200 maH 4 cell LifePo4s in the PeliTRX and they outlast the laptop battery at around 2 hours of mixed sending SSB/CW, anything up to 200 watts 
The discharge profile is awesome for equipment that really likes to be at 13.8V. The RM Italy HLA-300V starts to complaint at any sag below 12V, these keep it up there at around 13V even under load.
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Hi Mark, what voltage do these exact batteries peak at when charged? Do they stay close to 13 under use, even in the cold of winter? My similar mAh LiPo’s drop down to ~10v after a few FM QSOs on the 818, so it cuts power to 2.5. Not an issue in the Lakes, but I want to give QRP SSB HF a go this year, especially if we go to Tenerife in September (I’m being optimistic!!!).
Cheers for the heads up about UK availability.
73, Simon
You need to define “few” and how long they last to decide whether your LiPos are working as expected and give the claimed capacity of the cells.
Hi Simon
Fully charged for the 4 cell 4200s is 14.2 volts. However, they very quickly drop to 13.7 volts and then it is a slow drop in voltage during discharge to around 13.2v. They stick at that until about 20% capacity remains, at which point it’s time to swap out for a new one as the voltage drop increases rapidly, certainly at 12.8 volts it is definitely time to cut and run.
I’ve used these batteries in -7 degC over the course of a few weekends this winter and honestly the temperature doesn’t seem to have any significant effect, certainly not that I’ve noticed on the voltage discharge profile, although maybe they run out a bit quicker. I think the LifePo4 chemistry is more tolerant of low temperatures. I’ve been pushing 180 watts CW RF out with the HLA-300 so a pretty good test!
The 3 cell 2100 mah LifePos I use specifically with the FT-817ND drop down below the voltage threshold where the rig indicates 5 watts with the flashing bars but honestly I’ve had no issues with the rig pushing 5 watts at lower voltages - the internal resistance is so low on these they have no problem taking the increased current draw with no additional sag in voltage.
Regards, Mark. M0NOM
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Mark, your link was for 3S LiFePO4 not LiPo, so isn’t that a bit low V?
I’ve used:
- 4S LiFePO4
- 3S LiPo
- 3S LiPo HV
- 3S Li ion
- 4S Li ion with buck converter
The Li ion have better energy density than the other chemistries, but don’t deliver such high current (but we’re talking only running an electric bike vs. turning over an engine!). Li ion light-weight pack (internally a bunch of 18650s) availability is improving as they are becoming popular for long-range FPV drones†. This link is not a UK supplier, but they’ll probably turn up somewhere:
Edit: Here’s one in the UK, but a bit dear:
† [ I have to add that FPV flight beyond line of sight is illegal in the UK (and EU) as is going over 25mW TX power, typically considered necessary for this application. ]
Hi Andy,
I have two Turnigy 3S 2650mAh Li-PO batteries paired (with a Hobbyking harness) so in theory I should have 5300mAh to play with (± a little).
On a fairly recent activation of Ben Macdui I started calling CQ on the FT-818 at 6w 2m FM at 08:45, made 2 contacts on FM, called CQ on SSB and made 2 contacts on 2m SSB. Activation was complete by 09:15 and the rig was showing approx 10v. The batteries had started at their usual ~13.3v and had been balance charged the night before.
I’ve had similar elsewhere, e.g. Muncaster fell. We (XYL & I) made contact with G4VFL for the WOTA. Walked over to the SOTA and had a chat to Andrew again, followed by Mark NOM on his SOTA. So a total of 6 contacts and maybe the same number of CQs. Batteries were down to about 11v and then by the time we did Irton Pike later that day (just two contacts for the WOTA) they were on 9.9v.
Maybe I’ve had bad luck with these Li-POs? Or am I expecting too much?
Thanks,
Simon
Thanks for the info Mark.
It sounds like these 4S2P will hold a higher voltage for longer than the Li-POs I have now, so hopefully will mean the 818 doesn’t keep dropping to low power. I’ll stick an order in for a couple and see what they are like.
I also think a couple of these will be easier to take as hand luggage between two people on flights; my big 16aH LiFePo4 is over the 160Wh capacity limit for EasyJet.
Speak soon hopefully - as soon as we can travel, we’ll be looking to activate some hills. Never thought I’d be so excited about being allowed to activate Billinge Hill!
Cheers,
Simon
That sounds high… 12.6V for 3S LiPo. Is this on the 818 display? They are often not well calibrated, my 817s both read under by about 0.5V.
I’d de-rate the capacity to 80% because of marketing/stuff 
So 4.2Ah
The 818 will be a bit more thirsty at 6W vs 817 at 5W, but 817 is c. 2A for 5W FM. So let’s say 2.5A TX current. If you were key down for 30mins that would be 2.5A * 0.5h = 1.25Ah. Not much really for a 4.2Ah capacity system. The voltage should start out around 12.6V and drop in use. With the specs they should be about 70% full still so I’d expect the voltage to be above 11.5-11.7 looking at typical discharge curves.
Sounds like there is a cell in there that is a bit goosed.
Try just one pack at a time and see if one pack is much better than the other.
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Thanks Andy,
I am just going by the voltage on the 818 screen; I do have one of the little LED/beeper voltage warning units to connect to the battery JST cable, but tend not to use them in the field much as it’s one more thing to remember to pack.
Fair enough on the 80% comment ha ha! With you on that for sure - I guess it’s as realistic as published MPG figures for cars 
I’ll carry on experimenting with the packs I have and will order a couple of the LifePo’s Mark has linked to, as I’ll need higher voltages available when I’m using my amplifiers.
Thanks again,
Simon
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You’ll have no complaints with the 4S LifePo4s. I’ve just ordered two more so I don’t have to keep taking the ones out of the PeliTRX if I want to use the FT-857. One will drive the FT-857 at 100w for an hour or so when I go out at lunchtime chasing SOTA, no problem. I don’t have an issue with the 3S LifePo4s I’m using, but 4S will obviously give you no issues tipping under the battery voltage sensor.
Regards, Mark. M0NOM
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Just to add from my experience today (when I was probably paying more attention) the most I saw after I plugged the battery into the FT-857 when switched was 13.7 volts, so I don’t think you’ll ever see over that in use - the charger is obviously driving up the voltage to 14.2 volts, but it looks like the voltage drops back down when charged.
The drop to 13.2v is quicker than I thought, so really as soon as I was setup and ready to go the voltage had dropped to 13.2v. Today I did some rag-chewing on 80m 100w and after about 45 minutes the RX load voltage had dropped to 13.0v. It stayed above 12v at all times under TX load, mostly only sagging to around 12.8 volts.
As the discharge profile is pretty flat it is difficult to conclude how much longer it might have lasted. I have driven them down to around 12 volts (as viewed on RX), but the rig at that point is cutting TX power significantly anyway as the sag under TX load was dropping the voltage below 12 volts.
Hope that helps. Mark.
Thanks Mark - I spotted them on Hobby King at about the same time that you posted - so the LiPo are going into retirement with the buck converter ( partly caused by me half killing one letting cells drop below 2v… ) and I’m ready for the next activation with LiFePO4 technology … and possibly a bit less weight in the pack. Reading about the discharge profile is very useful.
All we need now is the chance to get out when this virus has finally been beaten into at least a stalemate…
73 Paul
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Given that LiFePo availability is a continuously hot topic I thought I’d see if they were in stock or not at our favourite Hong Kong RC supplier.
The 4200mAh 4S2P is in stock in the UK/EU warehouses of HobbyKing for £36.28 + p&p.
To give some kind of idea of how much use you can expect, I used one of these to do 4 activations totalling just over 4hours in total with a barefoot 817 and the battery was reported at “54% full” when I put it on the charger.
Yes, I bought a 4200mAh 4S2P from them a couple of weeks ago, at the time they claimed to have 8 in stock, I think. Worth keeping an eye on them as they seem to arrive in small batches.
I updated my battery box with a second Powerpole connector. The battery is wrappped in a piece of old closed cell sleeping mat so it doesn’t rattle around in the box.
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I went to see the actual stock level and it said on backorder. I know I clicked the “in stock” only button and so it should have only showed real stock so it looks like I was somewhat fatfingered here. Having closed that browser window I cannot confirm it really was set. Sorry if this has got people all excited. They do have some 2S1P in stock if anyone should wish to make a pack out of 2 of those.
The Zippy 4200mAh batteries are back in stock. Or rather, they are at the time of writing… 
Just a quick heads up that the Zippy 4200mAh LiFePo4’s are back in stock in the EU warehouse, in case anyone is looking for them (see John’s link above).
73, Jonathan
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