One very common question I get about portable Amateur Radio operation is what do I use as a battery? I have answered this question individually more times than I can mention so I thought I’d write it up as a post to help others.
I’ve used everything from car batteries, Sealed Lead Acid Batteries (SLAB), standard AA’s, Lithium Polymer (LiPo) and Lithium Iron Phosphate Batteries (LiFePo). These all work, but all have disadvantages, just some for my type of operation are much larger than others.
My portable operation tends to take two forms:
- QRP Operation (10w or less) from a hilltop/SOTA summit for 4 hours of less. This could be a casual SOTA activation or it could be a contest.
- QRO Operation (50w-100w) for a short amount of time (2 hours or less), maybe to dip into a major contest to make some DX contacts
My initial SOTA activations used a SLAB battery. These are very common batteries and you can pick them up very cheaply at radio rally’s. The downsides for me were twofold and pretty major. First of all the weight is substantial even for a low capacity battery and secondly it only supplies 12v out which drops off pretty rapidly with discharge. This meant I could only ever run a maximum of 5 watts out from my Elecraft KX3, which under tough conditions is, well, tough!
LiFePo batteries are my chosen battery based on the current technology available. They hit the sweet spot of lightness vs performance. For the same capacity they are half the weight of SLAB batteries which is pretty significant if you have to walk any distance to your operating location.
LiPo batteries offer similar performance, but with quite a major drawback, they’re quite prone to catching fire while charging! LiFePo batteries are a lot safer in this regard while offering the same level of performance.
Here are the advantages I’ve found:
- Light – Half the weight of SLAB batteries of the same capacity
- Supply 13.2v – This is enough to power my rigs at their full output where a 12v battery wouldn’t be man enough
- Slow Discharge Curve – The high voltage is maintained almost until the battery is depleted, certainly not the case for SLAB’s!
- Fast Charge – My 4200mAh LifePo4 battery takes less than 1 hour to charge
- Stamina – I’ve yet to deplete one of these batteries in one session, indeed I ran a pileup for 4 hours on one EA8 SOTA summit and it was still fine running my KX3 at 10 watts.
I own two of these LiFePo batteries:
- Zippy 4200mAh LiFePo4 4S2P (around £35 from hobbyking.co.uk)
- Zippy 8400mAh LiFePo4 4S2P (around £63 from hobbyking.co.uk)
The 4200mAh battery is the one I use most often for SOTA activations and any QRP operation. This must have had over 75 outings to date and is holding up well with no discernible decrease in performance.
I use the 8400mAh battery less often for shorter QRO operations with my Yaesu 897, once again I haven’t had any issues with this battery:
Note: The connectors you get by default on the batteries are meant for radio controlled cars. I replace these straight away for Anderson PowerPole connectors (which I also fit to the charger). Be very careful not to let the exposed positive and negative wires touch when doing this, I did and thankfully still have a working battery, others have not been so lucky!
I made a video explaining the two and comparing them for YouTube if you want to find out more:
A quick word on charging these LiFePo batteries. You will require a special balanced charger for these batteries. I use the Turnigy Accucell 6 Charger/Balancer (around £25 from hobbyking.co.uk) which can charge a multitude of battery types including Lead Acid, NiCD, NiMH, LiPo and of course LiFePo.
Balance charging is important to keep each cell healthy and evenly charged. LiFePo batteries have a separate balancing cable which you connect to the charger to help with this. Here’s my charging setup:
LiFePo batteries are justifiably popular with a lot of serious portable operators and seem to be the defacto choice by a lot of SOTA operators. From my point of view their weight to performance ratio is fantastic compared to the other options currently available. They do cost more but this is repaid by better performance.
Can you use a cheaper SLAB for portable use? Sure you can. But when you walk up a mountain for 3 hours you will pay that little bit more for something half the weight!
Got any further questions? Let me know in the comments below and I’ll try and answer.