Kosmik Capacity Limit - Great Feature

[dl7uae]

And for those doubting the accuracy of JLog2.5, doesn't it just read the kosmik values and pass them on, so really it cant be any less accurate than the kosmik itself, since they are the same thing.

KOSMIK is calculating mAh by itself, JLog just use it - and puts mAh consumed by a HV²BEC on top if used and configured.

Completely different with JIVE: Everything has to be calculated by JLog, most complicated is the calculation on current value given by JIVE. The shunt in JIVE is neither calibrated nor temperature compensated, the shunt is just a trace on PCB. TC and "calibration" is done later by JLog, so we have an "ImotShunt" (software ->JLC) to "tune" the JIVE that the mAh fit to the recharged number.

[hemp]

Originally Posted by rebeltrousers

Is it unsafe for their voltage to be allowed to go below 22.2 under load?

No, it's not unsafe for the voltage to drop under load, it is damaging for them to be fully discharged. Resting voltage is just a convenient way to check remaining charge in a LiPo since we can quickly approximate mAh from voltage.

I don't worry about voltage under load, except to ensure that I have enough to power whatever it's powering, or to determine if a pack is dying or of poor quality (high IR.)

Most of us bring our LiPos down with far more charge left than is actually necessary. 20% leaves a huge safety net. It is a good idea with packs that have one or two weak cells, though, as the value we need to worry about is the charge left in each cell, not that of the overall pack.

[dl7uae]

true

[rebeltrousers]

Duplicate post.

[rebeltrousers]

Duplicate post.

[rebeltrousers]

Originally Posted by hemp

No, it's not unsafe for the voltage to drop under load, it is damaging for them to be fully discharged. Resting voltage is just a convenient way to check remaining charge in a LiPo since we can quickly approximate mAh from voltage.

I don't worry about voltage under load, except to ensure that I have enough to power whatever it's powering, or to determine if a pack is dying or of poor quality (high IR.)

Most of us bring our LiPos down with far more charge left than is actually necessary. 20% leaves a huge safety net. It is a good idea with packs that have one or two weak cells, though, as the value we need to worry about is the charge left in each cell, not that of the overall pack.

Thanks heaps for the reply. Lucky I'm mostly using revolectrix packs then haha!
So 22.2v is totally empty then right?
I'll just try and not load the packs up late in the flight and not sweat the little low-peaks.
Maybe 3500mah on the capacity limit might be better than my current 3000.

[hemp]

Originally Posted by rebeltrousers

Lucky I'm mostly using revolectrix packs then

You know that's right!

Originally Posted by rebeltrousers

So 22.2v is totally empty then right?

Uh, well no, but it's also not that simple. Remember, it's the per-cell charge that we're concerned with, not the overall pack charge. So 22.2v on the pack could mean one cell is at 3v, another is at 3.9v, and the rest are around 3.8v. Running that one cell down to 3v (essentially empty) would likely do serious damage to it. That would be a really bad pack - you won't see such high extremes with modern LiPos, but the point remains significant.

But if we assume that all the cells deplete at approximately the same rate, as they should with a quality pack that's been cared for, then you want to stay above a resting voltage in the area of 3.6v per cell, or a total pack voltage of 21.6v. At 3.6v those cells are no where near empty, they should have a solid 10-15% charge left in them and won't suffer any undo harm. To determine exactly how much was left in them, just charge them up full and look to see how many mAh your charger put back in. Personally I try to bring my packs down around 3.7v just because I like the extra safety margin and I don't find the extra few seconds of flight to be worth stressing over. I also tend to only charge my packs to 4.1v unless I'm looking to put on a good show.

Originally Posted by rebeltrousers

I'll just try and not load the packs up late in the flight and not sweat the lite low-peaks.

I don't worry about loading them up late in the flight. You can run full-out from start to finish, just make sure you're not pulling too many mAh from any individual cell.

[Chris.C]

So I guess the feature in my charger could handle this readily. I have been using it before and after charging my packs. It is to tell the voltage difference between the highest and the lowest cells.

When it comes back after a flight, this should read no more than 0.06V, same as after charge complete. I do set my charger to cut at 98%.

[rebeltrousers]

Hemp:
Thanks for all of your info. Really appreciate it!
I think I can probably go a bit lower because all of the cells across all of my packs are very even on charge and discharge.
At the 3AH setting they come down with 3.8V per cell so I could probably go a little further than that and still be safe?!

ALSO I tried doing an auto and bailing-out just after the capacity limit kicked in. The Kosmik bails-out back up to the normal headspeed, not sure what happens after that though.

[rebeltrousers]

Went to 3.5AH and got good long flights. Packs were all just over 20% when they came down so I'm pretty dam pleased!
The best was a 12-minute hover

[jamin_00]

Good thing is it works in the cold weather also.

I always get a minimum of 5:30 out of my packs and since I have only flown a dozen times since its got cold and only a few of them with a Kosmik fitted machine over the past couple of weeks I decided to fly until the capacity limit came in and it did on all occasions ranging from 4:20 - 4:40 and using the same 4000mah leaving the packs at around the 20% mark.

Happy days as now all my big helis have the Kosmik so I'll just set and fly knowing that I can't over discharge my packs in flight

[rebeltrousers]

Crazy 22-minute hover at 950rpm today.
For a while I was worried that the Capacity Limit wouldn't kick-in but it was a relief when it did!!

[Luisito]

Wow that's a long time. I would of worried too waiting that long.

So your RPM dropped to? Would be nice to see the logs.

Luis

[rebeltrousers]

Seriously I was just about to land and check the batteries, and kept hovering nice and close expecting to see a puffed battery pack.
Here's a screenshot of the log, I'll attach the full log too!

[rebeltrousers]

Ahh, just found that the full log is 8.59mb so PM me your email if you'd like a look!

[wadders248]

So when the capacity limit is reached what head speed does it drop-down to? Do you get 30 seconds and then the power is cut?

[smsodhi]

There is a "blip" where the RPM drop about 80-100 RPM when the limit is activated, it then slowly drops RPM over the 30 seconds. I am not sure if the power will be cut, but you will have a job flying at the low RPM's by then.
this graph illustrates it nicely

https://www.helifreak.com/showpost.p...9&postcount=15

[helicraze]

Does it actually cut to 0 rpm or only slow when cap cuts in??

I flew 2.5 min speed the other day and it cut in, then 6 mins soft moves and it cut! Sweet

[jamin_00]

The initial drop depends on the rpm and here its around 250rpm. It then continues to slowly decrease of a 30sec period by which at the end it will be not enough to hover.

No matter how far out or where I have been there is always enough time to get back and land

[wadders248]

Cheers smsodhi and Ben... can't wait to finish my build and try it!