Looks like the 4200mAh 4S2P are available from Hong King. Bit more expensive postage ~£16 than EU.
I found that my local Conrad store stocks the Hacker LiFePos:
The link works, don’t know why it’s saying 404. They have the advantage that you can order online and pick-up in-store, saving you the shipping costs. If you collect points or vouchers, you might get 10% off. Can’t wait to try mine out, but the weather has been awful over the weekend. Fingers crossed for Wednesday.
73 de OE6FEG
Matt
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AliExpress, you can buy the individual cells much cheaper, make your own batteries.
China never seems to have an issue with the paperwork 
The price is a complete joke for only 2200mAh. Did you really order one?
I almost ordered a 1300mAh as well. Yes, it is eye-wateringly expensive, but I was rather disappointed with the Zippy Flightmax 4200: it doesn’t hold its peak voltage at all and falls back to 13.8v almost immediately without any load at all. So, for me it’s a choice between a battery that is twice as big and heavy as I need without the stated capacity, or one that is twice as expensive. If the quality is high I’ll call it a draw.
73 de OE6FEG
Matt
Please check LifePo4 issue - #10 by DK9JC
and then also LifePo4 issue - #37 by DK9JC
Could be interesting for you. I also had trouble with my Zippy LiFePo4.
Hi Matt,
I was similarly disappointed by my Zippy Flightmaxes when I first got them, but some research identified that this is typical of LiFePO4 chemistry. The energy stored between the full charge voltage (14.4 - 14.6V for a 4 cell battery) and 13.8V is tiny, and soon dissipated even by self discharge as you have found; and to the start of the discharge plateau voltage at around 13.2V generally only 5% of total capacity. It will be very interesting to compare total capacity and longevity of the more expensive batteries.
73 Paul G4MD
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Well, I should be able to give a better opinion soon. My alerts are in for Wednesday morning, although I’ll have to get up before I go to bed. I’ll take a cell checker so I can keep an eye on individual cell voltage. I have had a stuck cell in the past and it means the voltage in the remaining cells can drop dangerously close to minimums whilst the overall voltage looks OK. Lets hope the weather plays ball.
73 Matt
I took my new Hacker 2100mAh on a double activation today. I used my KX2 with the full 12w at all times, apart from on 10m. The logs are below:
When I got home, the voltage was at 13.18v or 33% capacity. I could tell the new battery was better than my Zippy 4200mAh last night as I was charging it: it took much longer charge basically. When I plugged in the battery this morning, it was still at 14.06v, whereas, I would expect the Zippy to be at 13.8v. I don’t want to be too negative about the Zippys, as it seems some batches are better than others. However, there’s no doubt in my mind, the Zippy I have is one of the duff ones, and the new Hacker is a big improvement. Yes, the Hacker was expensive, but at least I can say I’m happy with the quality.
73 de OE6FEG
Matt
I would guess that batteries like these follow a similar method as semiconductor manufacturing and sales. Semis are made from the same masks and when complete are tested. The ones that work fully and at high speed are selected out and sold as fully featured full speed at the highest prices. As performance fails or subparts don’t function, they sold as slower speed or less function chips (i.e. 3GHz vs 2.5GHz vs 2GHz etc. 32MB cache, 16 MB cache) This way the parts which you would discard can still be sold for a profit.
It will be similar for batteries. The fine details of the design and chemicals used (quantities included) will give a max expected performance and capacity. They get tested during manufacture and the top quality items are selected out and sold for the highest price. You can work down the yeilds and the reliability and performance will get worse and worse but they will be sold for cheaper prices.
Then finally you get to the complete tat and junk which gets sold on eBay “As genuine guaranteed Samsung 3800mAH 18650 cells”.
Some people have been very lucky with their Zippy and Turnigy cells. Others less so. Considering that my original LiPos are no name bought for pennies on eBay 10years back, I feel I have been exceptionally lucky as has Gerald G4OIG @G4OIG who bought similar. The capacity is down but still acceptable.
We get let out on July 3rd in Scotland… I was thinking I must get my new pack fitted with connectors and get out somewhere. Instead I have to take my car for its very 1st service. As I haven’t been anywhere for 14weeks what I have saved in fuel will pay for the service.
Hi Matt
Glad the new battery’s a keeper hope you have a long and fruitful relationship 
The discharge curve is pretty flat and the terminal voltage of LiFePO4’s is a notoriously unreliable indicator of state of charge. I’ve found once you start falling off the edge it accelerates very quickly and just one more QSO (admittedly ssb) can put you in worrying about how low you can go territory 
If you plan to use anywhere near it’s full capacity a low voltage alarm gives some comfort!
73 Paul G4MD
Aware I’m responding to this a year on, I’ve just received a 7Ah from Battery masters and it’s a lot less weight than my old lead acid sealed 5Ah battery. I’m not quite out of lockdown yet and I’ve been using the past few months making new antennas and supports. Operating BYOTA, Back Yards On The Air, to test my new setup including new batteries etc. Bought 4 off 18650 batteries + diodes to reduce the voltage plus a Hobby King 2200mA LiPO. LiPO wins hands down, so together with my Battery Masters SLAUMXLI7.5-12 for £69 including charger I’m ready willing and waiting. Battery Masters do not sell small compact size types as used in radio controlled models, so for those real lite weight packers that may not be for you, weighing run at 0.9Kg. Hope this is useful to you all. Regards Mike
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I received my one today after 15 days. I went for the cheap way and did not order registered. I saved 2 bucks with unregistered.
Just checked the cell voltages on delivery:
Cell 1 3,236V
Cell 2 3,236V
Cell 3 3,238V
Cell 4 3,236V
Total 12,94V
I wonder how it compares to the old blue Zippy LiFePo4 and my LiFePo4 32650 DIY pack: LifePo4 issue - #37 by DK9JC which was a few bucks cheaper and hast at least 1000mAh more.
Mine also arrived about the same charge (3.245v/cell), and the wires are bare no bullet connectors like hobby king site says.
It was at this point I discovered I had no 45A power pole contacts left and could not terminate it to charge it! Waiting for more PowerPole stock to arrive tomorrow, interested to charge it up and see how it does as it’s my first LifePo4.
Annoyingly the low battery warning I got from hobby king is preset for lips and has no options so wails on the lower voltage LifePo4.
My battery voltage warning device has a small button which when pressed for several seconds, displays a series of voltages like 3.2, 3.1, 3.0, 2.9, 2,8 etc and if I release the button when it says 2.8, that’s the alarm voltage. Yours may be different. HTH
Thanks VK1DA, that’s how I expected it to work, but I cannot find any button and also this one has no display to show the limit. I might order some more from the Far East, they are low cost - the reviews said the LED ones are hard to read in sunlight but maybe its the right one as you can program the alarm for LifePo4.
I may just take the iSDT BatteryGo with me, it has a nice display showing battery voltage and overall battery % capacity. I have not used it in anger yet, connectors coming later and will do some experiments. Its not too heavy, will weigh everything at some point.
Useful tool:
Hi Paul,
My battery monitor has a few LED digits on the display, it cycles around the cells and shows the voltage in each cell. I think Andrew vk1ad bought a few of these and gave me one of them, so I am not sure where they came from. Its pins plug directly into the balance plug of the batteries we buy from Hobbyking. But I now mainly use the voltage display on my radio, and it lasts so long I have very rarely found it below 12v total. Mostly it spends a lot of time on 13v or 12.9v, the key-down voltage does go down to 12.3 or 12.2. I’m a bit puzzled by that key-down voltage drop because when measured at the battery it isn’t going down by anywhere near that much. Loss in dc cable? Maybe. More investigation needed.
73 Andrew VK1DA/VK2UH
Snap. There was a note saying it was shipped at a lower level of charge and should be charged soon. Mine was missing bullet connectors. I have adapters from the T connector on the Imax B6 and 5.5mm connector to the Tyton T connectors I use. I couldn’t be bothered ordering 5.5mm and waiting for them to arrive so I fitted the Tyton straight to the cell. Bit of a squeeze to get the LiFePo cable with heatshrink in the plastic but a little bit of patience and it slotted in. So I think I’ll remove the 5.5mm connectors from my system now.
Ok, for future reference of anyone else buying these batteries, the 45A Anderson contacts are what you need, cable fits fine but once crimped the contact is a tight fit into the shell.
The APP and other guides say the contact must be 0.170” wide, and my callipers measured it at 0.174 (as I could not get it to fit and was confused).
It turns out that the crimp tool was not wide enough to crimp the whole length, you can see it in the first photo that the top and bottom of the contact are not crimped, after much measuring and jiggling I realised this and crimped the base and end separately, then the shell fitted just fine:
You can see here that the positive contact is crimped evenly along its length, note also I fitted the black housing completely on the negative before I started on the positive - less sparks and doom this way,
The crimp tool is from sotabeams, but before I put anyone off I would point out this is the older iwiss made tool, I think Richard sourced a new tool in recent years that is different, in any case it works once you know what to do. A slight tweak with pliers help hold the many strands in and the connector on for crimping.
Cables are very snug fit but all fine no modifications to shell or cable:
Nice and tidy once you fight the boot onto the connector:
Had to be very careful with the cables when fighting the connectors and boot as don’t seem to be held tight with the shrink wrap, I might think about taking the power cable back along he pack and taping it down to offer some strain relief. The balance lead is short but I bought an extension (maybe 30cm) that makes charging a lot easier on the bench.
Not tested the battery in action yet but so far so good, thought might help others to know the 45A contacts fit and learn from my errors.
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A flat bladed screwdriver makes life a lot easier. Trying to push the contact into the housing with the cable tends to bulge the cable, making it neigh on impossible. There is even a dedicated tool for inserting and extracting the contacts:
Not too expensive I suppose.
73 de OE6FEG
Matt