Extra batteries for SP140?

Thanks for that, didn’t know. I think it is time to make an inquiry. A 6.6 kwh battery will give my x4 an hour of flight time. Bet you that will be some weight…

Indeed! Guessing about 60-70lbs. Probably I’d shoot for 4kwh max but that’s just my legs.

correct! connecting cells. solder the cable. install in a housing. there are certainly more than 50,000 people worldwide who build their own batteries for e-bikes etc. it makes no difference whether you use 10 cells or 600 cells. i think it’s like a gasoline engine. for some it is a matter of course to change the piston and ball bearing yourself and to adjust the motor perfectly. others have problems when changing the spark plug and air filter.


A spot welder seems to be essential.

Very true, I personally use a modified PCB spot welder that I sandwiched the mosfet’s between two heat sinks. On 4s the lightest setting is still more than enough for .010 nickel and I know I can go thicker than .015. My total cost including the battery was about $100 and so far it has lasted through over three hundred 21700 cells worth of battery packs and is still going strong.

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If you did that with molicel P42A cells a 6.55 kwh 14s31p battery would weigh 64lbs just in the cells. Or if you are feeling like you have a bit more pocket change, you could make it out of VTC6 cells in a 14s42p configuration for 6.56 kwh and it would weight about 60lbs just in cells.

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It’ll be 67.2 lbs in bonkas…

Yup, and the Li-Ion batteries still need a case and BMS which adds weight. In the end if the only factor was the gravimetric energy density we would probably all use LiPo’s, but its not. Additional factors such as ease of use, cost, longevity, and safety all give Li-Ion batteries a major advantage.


in the history of eppg it was initially like this:

many only had the option to use lipo because li-ion were not available.

The first thing that almost everyone has done is to build a housing that protects the lipo against damage in the event of a crash and in general during handling. made of sheet metal, fiberglass, converted tanks, etc. if i look at all the old pictures i always see a housing in 48 of 50 projects.
even with the yuneec, which is currently standing with me in the basement and is 12 years old, the lipos were already built into the glass fiber reinforced housing.

the x4 openppg was the first eppg sold as a series that did not have a safety concept for lipo for battery attachment and transport.
So to make it short: every battery needs a housing if the pilot wants safety.
if he does without it, it is ok for him. However, you shouldn’t advertise that it is lighter with weight than with others. it’s just different from the idea of security.

Of course there are also pilots with the x4 who have built good solutions for attaching the battery and some also use li-ion. this shows that people think about their safety.

the sp 140 has a specially designed housing as standard. good work and a step in the right direction.

hmm… I’m having a hard time imagining a crash that causes catastrophic damage to those Bonkas that does not also do the same to me. With myself and the frame between the batteries and a tree I don’t see the batteries getting damaged at all in a tree landing. If the batteries come loose in flight a prop strike could result. I’m very confident my own mounting system is quite failproof.

Of course I’d still not want to cause a fire on the ground even if I’m killed in a crash (I do have insurance for both). I think the risk of that isn’t really much higher than for a two stroke and a plastic tank full of a volatile liquid. Is it? Of course all practical measures should be taken. I just don’t see that there is much risk of the batteries being punctured in this application. Do LiPos burst spontaneously without warnings?

Mishandling could be an issue. I do a lot of plugging in and unplugging. Inadvertently shorting a battery even at partial charge would be - unpleasant indeed. Vigilance is my only safeguard here. Would the 8ga wires and XT150s melt apart before the battery ‘vented with flame’? Not gonna try it and see.

In no case do you have to justify yourself as you fly with your eppg yourself. if it’s ok for you. is all is well. if your insurance pays even if it is your fault, it is also very good.

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