4 Generations of FP 5s1p Evo 3700 packs - My Findings

[TomC]

I've been using FP 5s1p Evo20 packs since Dec/2005. I mainly have used them as 10s packs on my Ion, but have also used them on my 10s Trex600, 5s Swift, and a 5s E-plank (plane). Thought I'd summarise my findings with these and newer generation cells.

My original 8x 5s1p evo 20 3700 are now down to 7 packs due to a bad Trex600 crash ~4 months ago. All the remaining packs now have +200 cycles and still perform like new.

I have 6x 5s1p evo20 3700 new formula packs with ~50 cycles. These are performing well but do not deliver the same early punch as my older evo20's ands, in general, I get ~70-90 rpm less hs throughout a flight and ~100-150kw less power to the head. These packs also seem to take a little longer to balance. One of these packs is actually marked as 22c continuous (versus 20c) but it performs the same as the rest. These packs are still quite good, but not as good as my old/original formula packs.

I have 2x 5s1p Evolite 18c 4250 packs with only ~8 cycles (just about broken in). So far these packs seem to be performing as well as my 'old formula' 3700 packs. I have not stretched out the duration past 2500 mahr yet, but I should ultimately get ~15% more runtime than my evo20's.

I have 2x 5s1p Evo25 packs with only 5 cycles but so far these are going great. Slightly better early punch as the old formula evo20's and they seem to hold this power longer. It's early days, but I think I'm really going to love these cells.

I treat these cells pretty well. Charge-balance them at 1c max, discharge them to 75%. Also, I target my gearing to deliver peak amps to ~ the 20c rating and target average flight amps at ~1/2 this (10c). I also make sure that I get as much airflow over the cells as possible. Cell temps after each run are generaly 110-115 feg F, max 125 deg after a very long/hard run. Treat your cells like this and they will last a long time too.

Overall, I'm very happy with the performance of all these cells and have found FP customer service to be very good.

Cheers,
Tom C

[MrMel]

I hear you and agree,

I always stated that the NF packs wasnt as good as the "old formula", I got tons of better performance (volt under load, temp after use) of my old formula packs (actually my 2 year old old formula beats a new 20C), but now with the 25C packs, tide has changed.

So, all well!

[TomC]

Mel, I agree, my 1.5 year old, +200 cycle, old formula 5s-3700 Evo20's still beat the pants off my 50-70 cycle new formula ones! Although, the new formula ones still work pretty good. However, I sure wish I could trade-in the 6 x 5s NF packs I have for Evo25's!

Last week I had a problem with one of my old 5s Evo3700 packs. I was using it in series with another (that was within 0.01v) and got a sudden power drop. I landed and saw the my first ever puffed Evo20 pack. I let it cool down and the swelling went down. I thought I might have overdischarged things a bit but when I checked the other pack it was fine and put back 2800 mahr back into it (well within my 75-80% target). The voltage of the #1 cell was over 0.2 volts lower than the others, so this one is a goner.

To check the capacity of the 'good' pack I cycled it (2.6 amp discharge 3.7 amp charge) with my Hyperion 12s charger and lba10 balancers. I normally do not like to cycle lipos, but I thought it would be a useful thing to do in this case. By the way, I would only recommend doing this with a charger/balancer that stops things if 'one' cell gets below 3.0v. To my surprise, this pack took back 3400 mahrs, only ~10% below it's original rating. That's pretty good for +200 cycles! So, at this point I feel pretty confident in using this pack with my 75-80% discharge target (although I think I'll target 70-75% max with my older packs now).

Good news always seems to come in 3's;

- the old formula, +200 cycle packs still work great.
- the crash damaged pack (~4 months ago) was replaced with a new Evo25 pack at 50% discount (thanks to Will).
- I sent the failed, old pack back to our local FP supplier (ModelFlight) and it was replaced with a new Evo25, at no cost.

Man, it does not get much better than this. Imop, FlightPower Rules!

Cheers,
Tom C