[hugh m]

I didn't see anyone ask if you were using the the original chargers for your new packs. If so your charge times will increase significantly.

Your wall wart chargers are set to charge at about a C10 rate for a 600 mah pack or 60 ma.

Charging a 1500 mah will take nearly 3 times as long with the same charger.

That means 36 hrs or so min.

My Evo 9 has been updated to an extra capacity battery 2000mah and the original charger (60 ma) is useless for the most part. I use my accu cycle elite to charge it at about 1a.

Hugh

[Dennis 9412]

Originally Posted by chuebner

Well, I think I am gaining ground on these packs. I slow charged them both for 24 hours and cycled them both twice at 400 mah discharge and 150-200 mah charge. I am using my Hanger 9 Accu Cycle and my Triton 2. I have the one pack discharging 1390mah of the 1500rated capacity and the 2nd pack discharging 1430 mah. I will cycle them once more on the weekend and hopefully that will do.
Thanks guys
One more question. I understand that Nimh packs self discharge sitting idle much quicker than Nicads. Does anyone know approx how much quicker??

Thanks
Curt

Hi Curtis,

Glad to see you're getting some results.

As far as self discharge, if you have good quality packs, don't worry about it.

I have 2 2000 ma 6 volt NiMh NOBS packs in my 50cc Aeroworks Extra 260.

I keep my airplanes in an enclosed trailer year round. I put my trailer into my unheated garage (just to keep the snow off of it) last November and forgot about it until I brought the trailer out last week to get my planes ready for this summer. I charged up both batteries, and one took 130 ma and the other took 165ma.

This is after sitting in that cold trailer (up to -30C at times) for 4 months.

Self discharge is a non issue with quality packs.

Regards,

Dennis

[chuebner]

Originally Posted by Dennis 9412

Hi Curtis,

Glad to see you're getting some results.

As far as self discharge, if you have good quality packs, don't worry about it.

I have 2 2000 ma 6 volt NiMh NOBS packs in my 50cc Aeroworks Extra 260.

I keep my airplanes in an enclosed trailer year round. I put my trailer into my unheated garage (just to keep the snow off of it) last November and forgot about it until I brought the trailer out last week to get my planes ready for this summer. I charged up both batteries, and one took 130 ma and the other took 165ma.

This is after sitting in that cold trailer (up to -30C at times) for 4 months.

Self discharge is a non issue with quality packs.

Regards,

Dennis

Thanks for all the info, Dennis. I gather I just wasn't giving them a long enough charge stint on the charger, thus the poor results. They do seem to be coming into their own now.
I also believe that keeping batteries in the cold doesn't harm them. After all, people keep batteries in their refrigerator to keep them fresh all the time.
I am not sure if these Spectrum packs are top quality packs. Time will tell, I guess.
Max, who posted early in this thread, stated that his Nimh packs drop voltage rapidly to 4.8v, then hold steady for a long time at 4.6-4.7v. I have always stopped and recharged at 4.8v. Is using these packs at 4.6-4.7 safe??


Curt

[Dennis 9412]

Originally Posted by chuebner

Thanks for all the info, Dennis. I gather I just wasn't giving them a long enough charge stint on the charger, thus the poor results. They do seem to be coming into their own now.
I also believe that keeping batteries in the cold doesn't harm them. After all, people keep batteries in their refrigerator to keep them fresh all the time.
I am not sure if these Spectrum packs are top quality packs. Time will tell, I guess.
Max, who posted early in this thread, stated that his Nimh packs drop voltage rapidly to 4.8v, then hold steady for a long time at 4.6-4.7v. I have always stopped and recharged at 4.8v. Is using these packs at 4.6-4.7 safe??


Curt

Hi Curt:

Depending on the radio you're using, they MIGHT be OK, but when I was using 4.8 batteries, 4.7 was the low end for me.

If your radio is a 2.4 gig system, you might be skirting the brownout area, depending on the servos you are using etc...

2.4 gig receivers are very sensitive to low voltage and if the draw from your servos, combined with an already low battery voltage reaches the brown out area, the receiver could reboot, giving you a loss of control. These low voltage incidents show up in a 72 mhz system as a "glitch" and normally are momentary, but the 2.4 system might reboot, causing you tons of grief if you're close to the ground.

If you're in doubt, change out your batteries for 6 volt 5 cell packs and you'll have no more problems.

Regards,

Dennis

[Max]

Originally Posted by chuebner

Max, who posted early in this thread, stated that his Nimh packs drop voltage rapidly to 4.8v, then hold steady for a long time at 4.6-4.7v. I have always stopped and recharged at 4.8v. Is using these packs at 4.6-4.7 safe??
Curt

Hi Curt.

Yes, you should be OK down to 4.6

Spektrum lists thier minimum safe voltage at 3.5 V. Thats a far cry from 4.6 or even 4.4 for that matter. Users have tested to below that and still not had any brownouts until 3.0V

Remember that your batteries are 4.8V NOMINAL. If you stop flying when you get to nominal voltage, you are cutting out a lot of useable (and perfectly safe IMO) operation.

But hey, to each his own. If it comforts you to stop at 4.8- go right ahead. Remember- its your airplane, not ours. So do whats best for you.

BTW, I dont have the exact figures in front of me (I have them at home and can look them up later) my onboard voltage indicator shows green to 4.7V, Yellow at 4.6V and red at 4.5.
I have flown my helis into the red many times and never had an incident. FWIW
Cheers

[chuebner]

Originally Posted by Max

Hi Curt.

Yes, you should be OK down to 4.6

Spektrum lists thier minimum safe voltage at 3.5 V. Thats a far cry from 4.6 or even 4.4 for that matter. Users have tested to below that and still not had any brownouts until 3.0V

Remember that your batteries are 4.8V NOMINAL. If you stop flying when you get to nominal voltage, you are cutting out a lot of useable (and perfectly safe IMO) operation.

But hey, to each his own. If it comforts you to stop at 4.8- go right ahead. Remember- its your airplane, not ours. So do whats best for you.

BTW, I dont have the exact figures in front of me (I have them at home and can look them up later) my onboard voltage indicator shows green to 4.7V, Yellow at 4.6V and red at 4.5.
I have flown my helis into the red many times and never had an incident. FWIW
Cheers

I am still using the old reliable 72mhz radio gear and all standard servos. So you say that the Nimh batteries hold quite a while at 4.6v-4.8v? I may have to give this a try. I was always on the understanding that the safe cutoff point of RX battery voltage was at 4.8v.

Curt

[Max]

Curt- Like you I have learned about batteries from experence and reading from those that know thier stuff. IMO- the most authoritave Battery expert I trust is Red Schofield.

Check out his web page: Red's Battery Clininc:
http://www.rcbatteryclinic.com

on the left you see all kinds if interesting battery articles.
On the main page there is a link called "Basic NiCad Stuff"
http://www.rcbatteryclinic.com/seminar.htm Its mostly about nicads but NiMh follows most of this theory as well. Check it out- its an interesting read!

You will be particulary interestd in the discharging section. In that graph shown there, the "DeltaV" is that .1 volt I have been talking about (ie- going from 1.2V per cell to 1.1V per cell, or for an airborne pack 4.8V to 4.4V) notice that the "Knee" of the dicharge curve occurs below the 4.4 volt cutoff.

Notice that the midpoint voltage (4.6 in this case) give you plenty of room for error.
Also notice that the curve falls off quickly from the beginning (above 4.8V) to the nominal voltage of 4.8V. I feel that this is why you were concerned at the beginning (of this thread)when you stated that you felt your batteries didnt have capacity because you were considering them "discharged" at 4.8V.
If you run them down to the midpoint voltage (4.6V in this case) when you fly, then you will still have a HUGE safety margin

I know that all cyclers that were made before the fancy "programmable" cyclers available today (ie ones that only cycled a 4 cell airborne pack and/or an 8 cell TX pack like the ace Digipace and so forth) have the cutoff voltage set to 4.4 for the RX and 8.6 on the TX.

[Max]

Oh- I forgot to mention 2 things
The UBA Red mentions on his page is the battery clycle that I mentioned I have. Its top of the line and gives you great graphs so that you can "see" the discharge curve. But its $$ and IMO most people dont need the fancy graphs and fancy features that it comes with. For "Joe Average" , any kind of cycler is better than none.

The second and more important thing I wanted to mention is that it is SO IMORTANT that you cycle your batteries to know where that "knee" in the discharge curve appears.
In Red's article under the "MEMORY OR VOLTAGE DEPRESSION" section, he shows this graph:
Notice that the "knee" moves to the left as your battery gets a "memory". Most imortantly, the TIME for the battery to reach its "midpoint voltage" also shrinks.

You need to know what your capacity is (ie where the "knee occurs") so you will have the confidence in knowing how long it takes your battery to reach the "midpoint voltage" when you fly.

Case in point:

I have a 600mah rated battery that was fast charged all last season. This routine would cause the battery to have a "memory" that was below its rated output. When I finally got a chance to cycle the pack, it yeilded 300mah, or 1hr to discharge to 4.4V. That means midpoint voltage of 4.6V occured at 30 minutes.
If I were flying, that means that after 30 minutes of flight time, I would be below the midrange voltage.

HOWEVER, after I cycled the pack a few times, I got it back to 600mah or 2hrs to 4.4v. Now my midpoint voltage occurs at 60 minutes.


THIS IS THE MOST IMPORTANT REASON WHY YOU MUST CYCLE YOUR BATTERIES.

WHY? because lets say you fly with a 600mah battery and you assume your pack is in good shape, you would GUESS that the midpoint votage would occur at 1hr (If your plane drew current at 300mah) but as the pack degrades over time (say to a capcity of 300mah) then your pack reaches its midpoint voltage at 30 minutes and the knee occurs at 1 hour. So now you are flying to what you assume is a 600mahpack (and feel you can fly safely for an hour) but in reality, if you flew that pack (which has degraded to 300mah capacity) for an hour- your battery would die at the end of that hour and your plane would be toast.
So CYCLE those batteries!!!

[spitrc]

It is important to note here that Nicad and Ni-Mh are two different battery types with different characteristics. What was true for nicad is not true for ni-mh.

[Max]

Originally Posted by spitrc

It is important to note here that Nicad and Ni-Mh are two different battery types with different characteristics. What was true for nicad is not true for ni-mh.

DUDE! how can you say that? According to Red Scholefield, they are IDENTICAL in performance and characteristics EXCEPT for the DeltaV used when charging. THATS IT! everything else is the same. (Id post the link that proves that but the site is down temproarily)

If you are aware of some other differentiating performance characteristics that we should know about, please post them here.
EDIT- Here is the link http://www.rcbatteryclinic.com/ni-mh.html