Lifepo alarm on summit (4200mAh KX3)

Hi all,
I wonder if I may ask for some advice regarding LifePo batteries?

I have a Zippy 4200mAh (

Now, I’ve fully charged it and used it on a summit today using one of these little battery warning modules:

The problem I faced was the alarm would sound on any key down (even 3w tuning on the KX3).

I wonder if I’m missing something here? I disconnected it and carried on monitoring the voltage on the KX3 and it stayed around 13v (didn’t spot anything less than 12.9v whilst transmitting 10w CW)

Am I being a bozo?

Thanks in advance,


Hi Carl

You’re using a “LiPo” voltage checker on LiFePO4 cells… Have you set it to the right trigger voltage?

Carl, there would be a setting to program the alarm voltage. It may need to be set at 12v but actually for that battery there should be a description of at what voltage it is considered discharged

John ve3ips

Ahh! that would explain that. Thank you.

It was recommended when buying the battery and I obviously didn’t check the specs. I assume there is such devices for LifePo batteries? I’ll get on the google and see what’s available (!)

Thanks for your help, Paul!

73 de Carl

Thank’s, John. I need to do some research as to what voltage one needs to go QRT. I understand it’s not great to run them down too low. I’d imagine with 4200mAh it will run the KX3 for quite some time.

73 de Carl

Hi Carl, if you’ve got the one you linked to it is adjustable :slight_smile: Recommended minimum voltage for LiFePO4 cells varies slightly by manufacturer, but you should be OK at 2.5V per cell.

73 de Paul G4MD

I was discharging a 4200mAh Zippy pack and one cell would not discharge properly, which meant the other 3 went just a wee bit below minimum before the Imax kicked in and stopped the discharge. I recharged it immediately and the pack seems to be ok at the moment, but it no longer holds a full charge at 14.4 volts. That said, we took it out on Saturday and it ran 50 watts no problem for a single activation. I never take Lipo packs anywhere near minimum voltage now. If I get a stuck cell I let the pack rest, then reduce the charge or discharge current. When I use my KX3 I never get so low on juice (even on a 1300 mAh pack) as to need an alarm, I just use the built in voltmeter. If you’re running your packs low, I would take a cell checker along and keep an eye out for stuck cells.

I have a very similar looking alarm. It is very very loud (something that should be in the gripes survey) but can be adjusted for voltage by holding down the button and waiting for the alarm voltage to cycle to your preferred alarm voltage. The displayed alarm voltage on mine is the voltage per cell, so I think mine is set to 2.8v. For a 4 cell battery, that means just under 12v, the IC703 happily cuts the power back to 5w when input voltage is below 12, but I tend not to let it go lower. Depends on whether I am just wanting a confirmation from an S2S and is my 4th contact for the summit.

The 817 happily operates down to 9.6v (8 x 1.2v nicad) but by then a 4S Lifepo4 battery is too low for healthy long life.

Could be RF getting into it?

Also does not the KX3 have a user definable low-voltage indication built-in? The KX2 does.

I set mine to 2.8v too (the default is 3.3v and meant for LiPos) … if you run the pack down to 2.5v per cell you may well have damaged it by then (if the battery pack starts to look puffed out that’s bad news). The discharge curve for these batteries is quite flat down to about 12v and then falls off sharply so you definitely want to catch it before then.

I also put a cheap watt meter in line … that way I can tell roughly how much I’ve got left, and when I’ve gone much past 3500 out of 4200mAh I’ll stop (unless I only have 3 in the log and I’m on a 10 pointer).

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I tend to use Nimh or an SLA on the 703 and 817 due to its ability to go under 12v easily or if i need a lighter battery my 11.1 volt lipo.

For my current hungry mobiles like the FT-891 the Bioenno 9A works well at 13.2v and I have the volt tattler alarm set at 12 volts.

I also use the power analyzer to get a volt reading but I also have a small $1 ebay panel meter in a key chain box


Thanks all for the input - lots to go with here. I’ve adjusted the cell voltage alarm on the monitor and also setup a low voltage indicator on the KX3!

Fingers crossed we’re back in business now :ok_hand:

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Neat :slight_smile:

I’ve not found any definitive resource that suggests LiFePO4 cell damage will occur at 2.5V

That comment was based on my own observations - I have had a battery puff out when run down to 2.5v per cell, but never at 2.8v. Yes, in theory it should have been able to survive down to 2.

I also found this graph helpful when deciding how far to run it down:


Good thing using the FT450 and 857D don’t need one the radio shuts off when voltage drops off below certain point but not enough to effect the Lifepo4 battery i use. I to have a LED warning bit but have set mine to an alarm voltage of 10v. But radio usually shuts down first

Seen the latest,s ones they have brought out 2.2Kg in weight 16A 12V by Relion be good for portable and mobile usages provided not being a real mountain goat to reach ya goal.

But its hard cased comes with Anderson outlets and charger off E bay for about £175
Will put this on me wish list LOL be great for what i want it for not too far walking etc and portable uses. as if in case need something lighter for the PPSU got me 8400MHA Lifepo4pack at 1kg and its not that big either as in compared to say a lead or the pack i have now :slight_smile: smaller ones like 5 10 and so forth are available.

Karl saving his pennies again :slight_smile:

Karl, youre wasting pennies.I have exactly the same 16aH battery without the green sticker. Mine is sold by Power House Golf in Manchester and is quite a bit cheaper. Ive had it 3 years now and never had a problem. I never bother monitoring cell voltages.

Other batteries are available.

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Looks great Steve that battery, if you have the strength to carry it - which I know you have. The charger is the same one as I got with the 7 Amp (900 grams) hard case LiFePo4s I bought from the firm in Edmonton, London. Good to see the LEDs on the charger so you know where you are with it capacity wise during the charging process.

Like Karl found, if I use the FT-857 the radio shuts off above 10 volts and before the battery is exhausted, so no need for a monitor. I just run until the radio shuts off when TXing. It recently happened to me on a summit in VK, end of the day, 5th summit from the same battery running 50 watts all day.

73 Phil

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Hi Phil, my 16aH battery weighs less than 2/3 the weight of a 7aH SLAB. After 3 years I haven’t noticed any tail off in fully charged capacity, whereas the SLAB would probably be down to less than 50%.

Hi All,
I do have a Tracer 12v 24Ah Weight 2.85kg had it 3yrs used to run FT857 in car and have used it on a SOTA never had any bother with it at all.