That deep dark hole called QRP, Part 2

Alan VK2MG Antennas Hobby Projects Radio 04/07/2021 | 0

Chapter 2!

In the last chapter I spoke about exploring the concept of portable operations, taking delivery of a Yaesu FT-818, Making use of the 7M Sotabeams mast with a linked Dipole.

Natively the FT-818 comes with a 1900mAh Ni-MH internal battery and while you can still run 6 watts, it will run out of puff rather fast.

With OEM battery packs fetching $95 a pop there had to be a better solution.

After trawling the internet and having discussions with other club members about their portable power situation, I placed my focus on Lipo and Lifepo4 battery packs. Lipos, also known as lithium polymer are incredibly cheap and incredibly volatile, don’t keep them at maximum charge, don’t let them get too warm, don’t let them get too cold. It felt as though it was more challenging to take care of a set of batteries than it was a 6-month-old puppy.

Lifepo4 (Lithium iron phosphate) are a more gentle and more forgiving version. also, significantly more expensive.

I was recommended to look into the Turnigy 5000mAh LiPo 3S1P 11.1V series. The reasoning for this is all the research on the web (so it must be true) indicates the FT-818 achieves full 6W power output at approximately 9.6 volts, and anything higher simply creates extra heat dissipation.

My Intentions were to look into purchasing a single battery and balanced charger to keep everything in check and the purchase was going to be under $100.

Great right?

The Batteries were out of stock for nearly 2 months.

What if they are out of stock for longer again? What if I wanted to take a different radio out to the

field? The 5000mAH units won’t cut it.

Cue to what I translate as ‘buy all the things”

1x IMAX B6-AC charger

1 planned battery purchase turned into 2x 5000mAh 3S1P 11.1v, 1x 4200mAh 4S2P 13.2v unit and 2x 2500mAh 3S1P. There were stories of these units turning into balls of fire and “they should always be charged in a fireproof bag” – Good Idea, I’ll take 3.

Then the thought of “How will I check how they are performing out on the field?” I can check via the voltage indicator on my radio, but is that good enough? How accurate is it? What if 1 cell is draining more than the others? To be on the safe side I’d better add a small unit that allows me to monitor individual cells and have a proper visual guide via the balance charge port. I was tossing up between just an audible unit or something with additional features.

So why not both and experience the best of both worlds. It’s all about buying things and then realising 6 months later you didn’t really need it.

1x Lipoly Low Voltage Alarm (2s-6s) and 1x ISDT BattGo BG-8S Smart Battery Checker now added to the cart.

I also wanted a means to view my current draw and how much power I had consumed during my time out; this meant the procurement of a Turnigy 180A Watt Meter and Power Analyzer.

I clicked “Submit” in the check out and held back the tears when the final value was debited.

A few days later the local courier arrived with a comment of “geez you’ve been buying a lot of stuff lately!”

With a sheepish grin I signed for the package and ran into my office with the great haul of stuff.

Now this was quite a busy day already with quite a high workload.

I’m positive this won’t distract me… right? Nope. “Brad will you have that report ready by 1pm?” Sure! I said, I’ll get right onto it.

So, all at the same time – crimping, soldering, heat shrinking and placing some protective sheathing on the cables.

As with any new toys – I absolutely had to get this done right now, this very second. This was probably not the brightest idea for the day, but I have no regrets.

The task of putting Anderson plugs on everything.

First Lipo is up for charge!

This charger was only just powered on, when I read on a random web page to charge no higher than 0.75C for best lifespan. Whether this true I am unsure.

This IMAX charger is at the lower end of the price scale but has a large number of features including Wireless capability and full PC logging and control.

Charging capabilities are great; discharge is limited to 0.4A which takes an incredible amount of time to discharge a 5000mAh unit.

Here is the log of charging one of the near flat 5000 mAh units – 66 Minutes from zero to full. As you can see the last part is really the balance and float charge.

I really am a sucker for data, and having the ability to view the charge rate and overall capacity is quite good to see.

I would like the BG-8S to have logging capabilities, but that feature is well above this price point. (would be nice though!)

Now remember how I was adding Anderson connectors to all the things a little earlier? I still had 3 more batteries to do as I had run out of time earlier in the week.

Queue me bundling up all my equipment and making my way to the clubrooms to make use of bright lights, actually building things and the curious glances of an “ooh what have you got!”

I do have a hot tip for you, be careful of the side cutters when trimming back the silicone sheath, and don’t do it whilst having a conversation with someone, you may accidently cut into the second wire.

Those Lipos sure do pack a wallop when shorted out briefly!

I managed to do it on 2 batteries! The new Lifepo4 4200 mAh and my tiny 2500mAh which due to this had successfully melted the small gauge wire into a near solid piece of metal thanks to self- fusing properties of having the positive and negative wires make contact with each other.

Luckily there was no fire or anything dramatic as seen on multiple YouTube videos. If you have never watched a video of a Lipo self-destruct, I would highly advice you do so, It’s rather fascinating.

Now that all of this done, I now have several batteries with Anderson connections crimped and mounted, sheathed, shrink wrapped and ready for service.

A quick check on the balance charger shows them in very good shape. I put some of it down to the units not holding a full charge (they were at about 20%) with only a couple of mA difference between the cells, but will give you that they haven’t really been fully broken in yet either.

Lessons learnt here is to only slice off on wire at a time, lots of tape and don’t let them touch.

But, after all the whoopsies, I now have 19.2Ah worth of power tipping the scales at just over 1 kilogram. I am very happy with this and trumps my 25kg 75Ah AGM and the 12Ah AGM.

This will last me pretty much a full day of operation.

(This picture was straight after making a contact with a VK3 on 6w within the CCARC radio room, returned a smooth 5/9 which I was very happy with)

The bonus is that in one single bag I now have the FT-818, 5 AH of battery power (10Ah if I get greedy) and 3 different antennas. All of this in a 30cm x 25cm x 15cm bag and weighing about 2kg with everything I need in it.