NiMh battery alert!

[Kmot]

http://www.horizonhobby.com/Explore/Article.aspx?ArticleID=1731

[Ghost 2501]

interesting, that may be why my ni-mh batteries aren't lasting sometimes. looks like its the slow charger then a burn to top off.

[der kapitan]

Thanks for the heads-up, Tom, nice to know.

[Aerominded]

I almost always slow charge my NiMhs... :)

[tim slocum]

Just great, I've been quick charging at 4amps with a charger that does not have a display. Darn, I knew I should have paid a little more and got the one with a display. I guess I should use a tester to check the batteries before I go to the lake.

[Hoghappy]

Just great, I've been quick charging at 4amps with a charger that does not have a display. Darn, I knew I should have paid a little more and got the one with a display. I guess I should use a tester to check the batteries before I go to the lake.

4 AMPS...dang and I thought the 2 amp fast charge was putting the juice to em! :eek:

I charge most of my NiMhs at the recommended .5 amp for longer life. They get warm enough doing that...I can't imagine how warm they get at 4 amps.

Commodore Slick

Thanks for the heads up Tom.

[CG Bob]

I've been very happy with the Dynamite Prophet Plus LCD (http://dynamiterc.com/Products/Default.aspx?ProdID=DYN4049#manuals) charger. It's an Ac/DC peak detection charger that will charge 4-7 cell NiCd & NiMh packs. It has a variable charge rate from 0.1 - 4 A. The LCD screen (http://dynamiterc.com/ProdInfo/Files/dyn4049-manual.pdf) has a switch that changes the display from Volts, to Amps for charge rate, and MAh for charge into the battery. I usually charge new packs at 3 Amps; older packs are charged at 1 Amp; I usually trickle charge my NiMhs monthly during the winter

[Brooks]

Dave at Radical RC is my battery guru. You will learn a lot from a pro if you go to his site and read his "Battery FAC" and "Which is better NiMH or NiCd....How do I charge it?" sections. Scroll down the url page to find these interesting sections.

I quote from his "Which is better....":

"First and foremost! NEVER NEVER put ANY new battery on a Peak Predictor / Delta Peak or any other type of fast charger without giving it a break-in charge at C/10. Capacity 10 is the overnight un-terminated safe charge rate for NiCad and NiMH cells. You can plug it in and forget it. If you have a 280mah pack of any cell count, the C/10 rate is 28mah. This rate or less is what you need to break in the pack. A 1400 mah pack needs a charge rate not over 140 mah for its first charge. The charge rate can be less than C/10 but should not be over. Your charge time will be (Capacity X 1.6) / charger output in MAH. This will give you the time to full in hours for a first charge.

If you take a new pack and put it on a Delta Peak or Peak detect charger or any other kind of NiMH rated fast charger it will not be filled up. I don't care what the instructions say. I'm sure they say to never charge a new un-conditioned battery on them. If they do not tell you not to charge new packs on them then they are wrong. The voltage curve is measured and calculated by these chargers in order to predict the peak. The voltage curve is not normal on a brand new pack. It needs one slow conditioning charge before the curve becomes stable. Try as you may, you can't fill up a new battery on one of these chargers. After it's first C/10 charge, it will work fine. "

Dave also says that you cannot judge the capacity of a new pack until it has undergone 5 or more discharge cycles. You can use it in your craft before then, in fact right from the first charge. But the pack won't "wake up" as he calls it, until it has been used several times. Until then, it will not hold the advertised full charge mah capacity.

http://www.radicalrc.com/shop/

[Kmot]

I think this alert is more concerned with NiMh batteries used in transmitters than vehicles. Because you would be in a world of trouble if you thought your Tx was fully charged and went out to fly your model or drive your boat and have your Tx go dead on you.

[Aerominded]

Great point! keep an eye on the voltage level indicated if you have a computer radio! :)

[Brooks]

I've labeled my Spektrum DX6 tx, with the volt converter and a 1650mah NiMH: "2 hours left at 9.8volts". Your mileage may vary.

[tim slocum]

I've got the Vision Peak 2...without display. Man, I cant believe Ive been doing it all wrong all these years!! I will cut back to a slower charge rate and when I get new batteries(sounds like soon) I will slow charge them the first time. Thanks for the info guys.

[meechingman]

So does that mean we've all got to buy new batteries, or can we re-condition the ones we've got with a few slow charge / discharge cycles?
Andy

[AndyKunz]

Sounds like time to put LiPo's in my transmitter.

Andy

[Kmot]

So does that mean we've all got to buy new batteries, or can we re-condition the ones we've got with a few slow charge / discharge cycles?
Andy
I condition my batteries. If you have a charger/discharger it is a good idea to do it once in a while.

I don't bother with the .5A charge on new NiMh batteries. I charge mine at 1C. Only after they seem to lose a bit of capacity do I give them a slow charge at .5A and I have not had a problem doing this. Everyone has an opinion on this but I am happy with my method.

[CG Bob]

The LHS where I work just got the Dynamite Sentry (http://dynamiterc.com/Products/Default.aspx?ProdID=DYN4062) units yesterday (Nov 6). The Sentry is a digital voltage monitor for NiCd, NiMh, & Lipo batteries. Dynamite is calling it a capacity gauge, so I assume it will also measure the MAh of the battery.

[lowdive]

wow, i've been charging my nimh packs at 5amps, or just short of... i simply don't have time to wait hours to charge one pack, then the next... by the time i'd get through charging my packs the first one would need to be charged again!

i can see this rule applying to tx packs, but packs for cars, boats, etc? on the other hand, i do have a friend who has had one cell in a couple of his packs "pop". his charger goes to 4 amps so less than mine... we figure he just got a couple of bad cells but hey, it could be the charge rate.

[CG Bob]

I'm on my dinner break at work, and just plugged the Dynamite Sentry into a couple of different batteries. It has scales for 4, 6, & 8 cell NiCd & NiMh; as well as 1, 2, 3, & 4 cell Lipos. It has a digital readout for the remaining Voltage in the battery. It uses a bar scale to indicate battery MAh capacity; a digital readout of the MAh capacity would have been nice. I won't get rid of that digital VOM meter just yet. You could always use a Watts Up or E-flite Power Meter to get a reading of the MAh capacity of the battery.

[Aerominded]

I have a Prodigy II charger which provides charge/discharge rate, amount added/subtracted and the duration of the cycle on an LCD display... gives a complete picture of what is going on in my opinion... easy to use... recommended... I also like to use the watts up meter in the boats as a tool to predict performace, etc... fun stuff! :)

[Brooks]

Re: new NiMH chemistry?‏
From: davthacker@aol.com
Sent: Fri 11/16/07 8:52 PM
To: bkmart@hotmail.com
You may link to anything in my site, no problem.

Horizon hasn't elaborated very much. There is no problem with NiMH in general and getting this from what they are saying would be a mistake. Note they say "new". Probably they could be more specific in their description of the problem. Maybe they've seen just a little bit of it and haven't figured out yet precisely what the issue is.

There is in fact a new generation of cell called "Super Lattice" that does not take fast charging well. They do indeed false peak but any serious testing shows they die after being fast charged, often the first time. We dropped the Sanyo 2700 AA for this reason. The 2500 is more robust and the 900AAA Super Lattice cells haven't shown the same problems. Ive found even though I sold these 2700AA cells (not the famous and very good 2700AU) saying to use wall wart factory type chargers only that people would use fast chargers on them anyway then expect replacement when they fried from doing what they were told not to do. It gets expensive so I gave up the battle of trying to educate the public on the different care of this new variety of NiMH cell. Lets call them NiMHSL. Regular ol NiMH is and has worked for for years. Other vendors are aware of this issue and also post special info about these cells.

There is huge market pressure to create higher and higher capacity AA cells for the consumer market. NONE of the AA cells I have tested over 1700mah have taken to fast charge very well. Many people look at that capacity number and when they see a bigger one available they immediately assume this is the new standard, the cells to use. This is totally incorrect. This is why you buy your packs from experienced RC suppliers and not from Johnny-Discount-Omatic where you get the bargain result to go with the ill chosen goods. Certainly there are many reputable suppliers of RC packs of which I am one. I think RC pilots should be looking for good much better than consumer quality. There is always a cheaper pack or product with a bigger claim. The professional weeds through all this commercially driven nonsense and offers the good products, the things you really should be spending your money on. We need very high quality goods in this hobby. One mistake often equals one $500 to $10k pile of busted components.

Every time there is a NiMH cell that has a problem it's not long before the problem is being described by vendors or users in forums in such a way as to encompass every NiMH cell made. Sometimes it is over generalizing, sometimes it's just the natural growth of information from the truth to the ridiculous. If somebody finds a bad cell or bad group of cells, if it's NiMH there are many who are quick to say NiMH does not work. I've seen this kind of story many times over the years. Yet when a poor quality NiCad is issued it's just a cell to be avoided. Don't fall into the trap of shallow prototype thinking. Yes there have been bad NiMH and bad NiCad's and bad Lipo's but we all know there are many great cells to used in each chemistry.

Feel free to add my letter to your thread. I've not read it but I'm thinking it might add some focus to what is being discussed. Hopefully nobody takes any offence to my directly spewed opinion on this subject.

Happy Flying All!
Dave
Radical RC



Hi Dave,

This was floating around the rcgroups boating forum:

http://www.horizonhobby.com/Explore/Article.aspx?ArticleID=1731

Basically, Horizon claims all NiMH are going to peak early with this new battery chemistry. Your thoughts?

btw, I copied and posted some of your Battery FAC and Which is better NiMH or NiCd for the forum, giving you credit and your url. If this is unacceptable, let me know and I'll remove it.

http://www.rcgroups.com/forums/showthread.php?t=767787

Sincerely,
Brooks Martin

[Prins Willem]

what our grandkids will be using:

http://www.betabatt.com/

[retoabcr]

You can email on nimh charging anytime. I never heard of problems with nimh but being retired and my 9 rc 22" electric boats economy of buying cells really is a real eye opener. Thanks and have a good Thanksgiving!

[Silent-AV8R]

One thing to keep in mind is that NiMH cells are best charged at, or below, a 1C rate. So I charge my 3800 mAh NiMH packs at around 4 amps. The worry noted by Horizon and others comes when you are really pushing your batteries, which is something that has become a bug thing for us in RC. We seem to want to charge any pack of any size in 15 minutes or less.

Oh well.

[tim slocum]

A couple of weeks ago I quick charged my two 3300nimh batteries on a Sat morning thinking I was going to the lake, then something came up and I had to postpone the boating till Sunday. Sunday, I decided to top off the batteries and when I put one on the charger I was surprised to see was far from fully charged. It took at least another 10 mins at 4amps to get a "full charge". The situation was the same in the second battery. Does a battery usually lose that much of a charge in 24 hours? Or is the charger not really fully charging the batteries? The batteries are Powerizer 7.2v 3300mah and the charger is a Vision Peak 2. Discuss.

[cyclops2]

My 6 & 8 cell + 3000's charge in the same time after sitting idle for 6 to 10 months.