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Lithium Ion Battery power 16-8 volts

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Good vid Dave, where can you get those batteries? how much do they cost and can they be charged with a normal battery charger?

oh and are you sure you are a farmer? I never heard a single oohh aaaarggggg, any talk of combined harvesters or drainage in the lower field :lol::lol::lol::lol:


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I can get them from RPM but they're dear. They HAVE to be charged with a SMART charger so cant be charged inflight (not an issue cos they stay up for weeks) Someone told me they look similar to a laptop battery and they peak at 16-8 volts.

I'd be interested if anyone can find something similar. There's NO markings and it feels like a lump of cardboard. Haven't used the spare yet, except for at Lambourn when my first ran down in three weeks. They go suddenly when they go. Then they show 15-2 volts and damage occurs if you strain them by letting the starter "bog down" (bug**rs your starter too, on the Simmo atleast)

Yes Dave. I really am a farmer. Got hedgerows you can sleep under if you're down this way. Show you all the good places to fly. When my back's had enough (soon) I want a cafe, on top of a hill, by the A30, with it's own landing field (and petrol) accommodation so the locals and XCer's have a place to land (and be relieved of money) legitimately. Semi retirement and part time flying guide. Really fancy it.

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The mini2 has no pull start facility. E-start or hand start, or sit watching a charger.

As Dave shows, when it's warm, it doesn't take much to get it ticking over.

Curious Dave, is this battery pack isolated by the starter relay from charging?

I've the same motor and mine is wired to charge the lead acid as soon as engine is running.

How have you isolated the battery pack? Blocking Diode?

You've saved at least 5lbs over my lead acid monster battery. I couldn't see your starter wire gauge, but it looks like it certainly adds to the starter spin speed as well, which is a huge factor in cold startup. My battery (from a car jumper pack) was rated at 300amp draw on jump and still doesn't spin her over that fast.

Aside from wire gauge to the starter motor, all other things should be the same between my WJ RR clone and the FT 200.

Don't Lithium Polymer Batteries discharge Lithium ions?

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I'll look at the wires next time I fly with my cousin. Bought him a 2003 RR Walkerjet 200 simo recently. He has an 8 litre tank on it giving an hour and a half. 2 blade wood prop on 2-6 / 1 reduction I think. The difference in power and consumption between his WJ and my FT is staggering. He's using 5 1/2 litres/hour to my 4 max (and I can get down to 3-3 l/h) He's 2 stone lighter than me and he was under my Atis whilst I used an old Grid 1-2. The balance of engine tune, reduction ratio 3-1 / 1 and that 51 inch prop works well on the FT 200. We're trying to copy it soon with his WJ. Changing to 37 carb first and step by step we'll see where the difference is. Biggest 3 blader we can get on his is 125 though. 130 would not give enough clearance to the frame. Pity, as those extra 5 cm outside of the persons body make such a difference.

BTW His cranks slower but it will start 6 times or so AND it does recharge in flight. I'll try to find out how the charge is kept away from the li-ion battery. I suspect it's ONLY connected to the starter circuit as the engine will run without it completely. Flick start. And yes there is no pull option. The motor is so close to the frame you wouldn't get one in there. Nor would you need it.

If you have any info that might help me to improve cousins WJ I'd certainly be glad of it. Thanks


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2003 one of the last years WJ offered the simonini RR (I think), and I understood the RR to have a 51" / 130cm three blade helix as part of what made it an RR.

Now, I built mine from the parts, and my motor shipped with a 2.3:1 redrive (not by request), and a bing 84 (by request). I could fly around all day full throttle wasting fuel because the engine wouldn't spin up into the revs to use it. Nice and cool mind you...

WJ RR reads very much like a FT 200 which is why I said once it looks like a natural evolution of the design.

simonini 202cc

3.1:1 redrive

Helix 3 blade 51" prop

are the defining characteristics

On My rig, this will allow 7400 rpm and cruising I can fly for 3.5ish hours (Epsilon 4 @ trim) on 14l (no fuel restrictions here) which works out to your 4lph - after that we'll need to compare wing loads and other same sames. Still, damn close and there's some playing in there (after a couple hours one gets bored).

If the prop and cage are smaller, he likely has a WJ XC which was propped smaller (49" / 125cm) for smaller pilots to manage on the ground, same engine, not sure if the redrive was different or not, I didn't think so. If it was the same then the prop pitch might/should be different. I thought they used a three blade as well however. Maybe re propped due to a strike?

Divide the diameter of his larger pulley by the smaller to make sure he's running a 3.1:1, it may be just his prop is the wrong pitch and he's wasting fuel above X rpm as the prop's holding the mini2 back.


@ 1:45

compared to

@ 5:40 (note my silencer was partially plugged here, rpm should be even higher)

for an audio reference of the difference - same engine 2.31 vs 3.1 same as FT.

All the thrust is in the top of the rpm range which I couldn't get to initially.

The WJs used NiCad D cells in series for electrics. Great for a quick spin up to start, but not made to repeat the process many times without interim in flight charges. A reasonable trade off for weight. I'm lugging lots of lead around because I planned to draw off it for gloves and other in flight gear. 7Ah of it.

It will be nice when I can swap out some lead for Lithiums and a charger, which is why this thread's so interesting.

Next thing you know it will spin off to a "hybrids?" thread where someone suggests a brushless DC motor be used as a starter/generator/motor in combination with a two stroke and some Li-Pos... All about getting a charge controller right, and light.

Do you know the energy storage total of your pack? Charge rate, other Specs?

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