Choosing battery size

[N3NEI]

I’m about to receive my first portable QRP rig—a QCX-mini—and am battery shopping. Specifically, I’m stuck between two Eremit LiFePo4 models (I live in Europe), 2 Ah or 4 Ah.

I’m drawn to the compactness of the smaller one, and it appears that it can power the QCX for several hours. But I’d like to buy once, cry once: if I were to at some point get another transceiver, can I count on 2 Ah being up to the task for a few hours of casual operating? Or would 4 Ah be the better investment?

This calculator would suggest 2 Ah would be ok, but I’m curious to see what people here recommend.
http://www.4sqrp.com/Battery_Capacity/index.php

[K1GC]

I think either would work if you are thinking for QRP. A 3Ah Bioenno will run my KX2 at 5W for 3-4 sessions of CW in the 60-90 minute range. It might handle a 5th session, but I have always recharged before then out of habit. For a single QRP session of 2-3 hours I think 2Ah would be more than adequate. If you want more sessions between charges or want to have flexibility to say run 10W SSB on occasion, the 4Ah would allow a little more flexibility.

The QCX-Mini kit with a 2Ah battery DL2COM shared on QRPer sure is an attractive setup: https://qrper.com/tag/eremit-lifepo-battery/

[Brian - K3ES]

I think either would work if you are thinking for QRP. A 3Ah Bioenno will run my KX2 at 5W for 3-4 sessions of CW in the 60-90 minute range. It might handle a 5th session, but I have always recharged before then out of habit. For a single QRP session of 2-3 hours I think 2Ah would be more than adequate. If you want more sessions between charges or want to have flexibility to say run 10W SSB on occasion, the 4Ah would allow a little more flexibility.

The QCX-Mini kit with a 2Ah battery DL2COM shared on QRPer sure is an attractive setup: https://qrper.com/tag/eremit-lifepo-battery/

My experience is similar with 3 Ah and 6 Ah x 12V (nominal) LiFePO4 batteries. I bought the 6 Ah first out of an abundance of caution, then bought the 3 Ah to lighten the load in my pack. I have TX-500, TR-35, and KX2 transceivers, and all work for several hours on a 3Ah battery while running 5W CW. All are very efficient in use of power, and I would expect the same from a QCX. Be sure to check both transmit and receive current draw for other transceivers before expecting similar performance.

Good luck! Honestly, I don't think you can go wrong with this choice.

[SkipRD]

I’m about to receive my first portable QRP rig—a QCX-mini—and am battery shopping. Specifically, I’m stuck between two Eremit LiFePo4 models (I live in Europe), 2 Ah or 4 Ah.

I’m drawn to the compactness of the smaller one, and it appears that it can power the QCX for several hours. But I’d like to buy once, cry once: if I were to at some point get another transceiver, can I count on 2 Ah being up to the task for a few hours of casual operating? Or would 4 Ah be the better investment?

This calculator would suggest 2 Ah would be ok, but I’m curious to see what people here recommend.
http://www.4sqrp.com/Battery_Capacity/index.php

I've tested my Venus SW-3B over the past dozen sessions or so and it draws an average of 300 mAh per hour of operating time. Of course, that's based on my operating style (a mix of calling CQ, search and pounce, and responding), with frequent breaks to chat with passers-by who are often interested in my setup, so more intense operations might yield a slightly higher number. Even still, a 2 Ah battery will give you HOURS of operating.

Hope that helps,
73 Skip K4EAK

[N3NEI]

Thanks for the helpful info, all. 2Ah it is!