Frag

I've got a Kokam 11.1v 1500mah Lipo pack that I use on a geared speed 400 with FMA 20A ESC (can use Nimh, nicd, or lipo) on a little Fundango. A while back the esc began to shut the motor off early. It seemed the low voltage cut-off was kicking in too early. I discharged the battery with the Triton and then gave it a full charge. It only took in about 1000 ma. I then discharged it again and got the same 1000 ma out of it. The pack could be swollen. Maybe a little. I could be just reading that into it though. So, is my pack dead?

DHG

My Feedback: (7)

Frag,

Did you take any measurements before? That is, do you have a baseline for comparison?

I have a Triton and am finishing up my first season playing with lipos. I'm using Thunder Power 3s 1320 packs. I've never seen more than about 1150 mAh on a cycle, and most of my flights now use between 650 and 900 mAh of juice. The packs are probably out of balance, and one of them has swelled a little. I'm thinking that they (and most likely any brand of lipos) suffer more than we realize from the combination of haphazard cooling, long flights, and the lack of balance taps.

If yours still works but is losing its zip, all I can suggest is to treat it gently, let it cool thoroughly before charging, and stop the charge when the Triton reduces the current to 0.1A or less. Then save up for a balancer and some balanced packs to replace it next season. FWIW, that's my plan.

We're all still beta-testing this stuff.

Duane Gall
RCPRO

Frag

I didn't ever write anything down as far as baseline charging when the pack was new, but I am sure that it used to take at least 1300 ma on a charge before. I guess something is out of balance or just plain out toasted with the pack. I suppose a new pack would be the easiest fix....

Trogdor the Burninator

Frag, I've had a number of those old Kokam packs and, like DHG says, many packs never really get "full" capacity even when new. I have two year old 1500 packs that are really down from where they started something like 1100 mah and they still work fine, they just dont put out the amps they used to and have less capacity but they work fine.. I'd keep using them til the amp output drops to where they're really not any fun to use anymore.

DHG

My Feedback: (7)

As it was explained to me (by the retailer, but I consider him trustworthy) the rating of the packs is done using a VERY optimistic testing method -- that is, discharging at a much slower rate than we fly at, and taking them down to a much lower voltage than would be safe for regular use. So, although you may think you've got 1500 mAh on board, the actual usable capacity is about 1/2 to 3/4 of that. And that's still 2 or 3 times the usable capacity of a Nicad pack of the same weight, so it's worth the tradeoff. Just an expensive lesson to learn.

Panzlflyer

My Feedback: (15)

I just had a conversation with a battery supplier about this and the manufacture gets their stats from a 500ma discharge to 3v per cell, not something we do!! They were appalled by what we do to them.
Kokam/ FMA show that the earlier packs at 10C get hammered pretty quick so it may be that the pack is on its way out. I believe they have the info on their site.
I just got a CBA battery analiser and it confirms the poor performance as you jack up the amp even on a so called 20c pack.