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Old Oct 29, 2001, 08:11 PM
DLC
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Houston, TX USA
Joined Jun 2001
357 Posts
Sears/Ray O Vac 9v Life Time

My Sears/Ray O Vac 9v batteries start dieing after 15 - 20 recharges. Is that normal or am I killing them somehow? I charge them with a Dymond Delta Peak Mini Charger at a charge rate of 300 mah. They get a little warm while they are charging, but not hot.
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Old Oct 29, 2001, 08:22 PM
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mattk17's Avatar
Dallas,TX
Joined Jul 2001
1,656 Posts
DLC,
I have lots of the rayovac 9volts and my oldest 2 have well over 50 charges and they still work great. I'm also charging at 300ma but I currently use a cheapie manual fixed rate charger with a timer.

I can't explain why but I have a hunch that the sears die hards are somehow different than the actual rayovac labeled 9volts like they sell at wallmart. If you have the sears die hards and they are crapping out, it would support my theory.

If you have the actual rayovac brand and they are craping out, I'm nervous since I just today ordered one of the Dymond micro-peak chargers! They had a great write up in the rc magazine and the price was right but if they kill my little rayovacs prematurely, I guess I'll have to only use it on my bigger battery packs.
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Old Oct 29, 2001, 08:40 PM
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Gerry Markgraf's Avatar
S. Calif
Joined Mar 2000
1,409 Posts
I was planning on starting a thread on this very subject. I bought 4 of the Ray-O-Vac 9v MiMH batteries plus the wall charger at Wal-Mart. They seemed to work fine for a while but 1 went dead suddenly. Later, 2 more were gone. I doubt I got more than 4-5 charges each and they were well and truly dead. The 4th is fine. I bought 2 others and was flying my TigerMoth on them on Sunday, but I will stop buying them if the life is the same on these next 2. Any suggestions? I do recall that I forgot and I left them in the charger for a few days. Also, they were charged a few times and not used for several weeks.
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Old Oct 29, 2001, 09:34 PM
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Walled Lake, MI, USA
Joined Feb 2000
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I didn't have very good luck with the Rayovac NiMH 9Vs. First, they seemed to vary in performance even when brand new. Second, they seemed fragile and easily damaged unless the charge rate and timing was flawless. Out of 6 batteries, I really had only one that I thought gave consistently good performance. Since some people have had really good success with them and some haven't, I'd say they require special care and attention at the very least. But they are inexpensive!
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Old Oct 29, 2001, 09:51 PM
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North Jersey, USA
Joined Oct 2001
735 Posts
I have 3 Rayovac 8.4V (9V package) 150mA NiMH purchased at WallMart & 1 purchased at Radio Shack (too expensive). In use on Mini IFO w/ GWS DC-A & 10z4.7 prop, with somewhat "bursty" throttle use. Each pack charged maybe 40-50 times on an FMA SuperNova, anywhere from 100mA to 300mA, depending on my mood (typically 200mA). All have been consistently reliable with cases removed. I'll report on the DieHards when I pick up a couple.

-chris
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Old Oct 29, 2001, 10:30 PM
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Brentwood,TN
Joined Mar 2001
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I have bought both Sears and Walmart batteries and under skin is exactly the same. I suspect they are from same manufacture. I agree with Dave that the problem with these batteries is the variability. Some cells stink. I have 4 cells with 20 + charges and two of them are about ready to be tossed because they just don't perform well. I must admit that these cells are great in the indoor arena. Will probably purchase few more for super slow flying.
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Old Oct 30, 2001, 02:12 AM
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Victoria, BC, Canada
Joined Apr 2001
3,397 Posts
I have some Rayovacs, Radio Shack and an actual branded Gold Peak 9V. They are identical in construction and electrical characteristics. The Sears are identical in construction as well. I have probably 200 cycles on the batteries in total.
I charge them at 300 mA on a sensitive peak. It seems that only a couple of excessive charges or discharges that causes them to get too hot will permanently damage them. One lost 30% of its capacity when I accidentally charged at 1 amp and it overheated. Otherwise, they are all doing fine at over 90% of original capacity.

I do take care to make sure they don't exceed 40oC on a charge or discharge. That means not using them on a hot summer day. I have NiCd that can take a lot more abuse that I use if the temperature is above 30oC/85oF. That's only a couple of days a year in Mediterranean Victoria

Rick.
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Old Oct 30, 2001, 11:24 AM
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Dallas,TX
Joined Jul 2001
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This has always been a mystery to me. I have had great luck with the rayovacs and yet many others have problems. For those that have problems, all I can say is I'm not just making it up. I have lots of videos and pictures on my website of me flying lite stik, lite stik full fuse and tigermoth with the rayovacs and they fly great. Here is a recent shot of a lite stik full fuse and as you can see it is having no problem climbing with the rayovac.

I charge the cells at a constant 300ma using a cheap fixed rate charger from Fry's Electronics and a timer. I think the charger cost me a whopping $15.00. It doesn't do any peak sensing, pulsed charging or any of that so I have to use a timer to gaurd against overcharging.

I just ordered the Dymond micro-peak charger which does up to 8 cells and has an adjustable charge rate of 300/500/1000ma. I wonder if it will do a good job or just end up frying my batteries. I'll be sure to post my findings.
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Old Oct 30, 2001, 12:11 PM
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Agra, Oklahoma
Joined Feb 2000
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Same here - 3 different 9V batteries (8.4) and all three are simply not lasting more than a dozen or so flights in litestiks or tiger moths.

I'll switch to a different cell for sure.

Steve
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Old Oct 30, 2001, 12:58 PM
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Walled Lake, MI, USA
Joined Feb 2000
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The bottom line to me is that most NiMH 9V batteries are not suitable for e-flight applications. The Rayovac design, which is also available under several different brand names including Sears DieHard, is the exception. But I think that it just barely works if conditions are optimum. As with any marginal product, some people are really good at coaxing the maximum performance out of them, while others aren't. Also, due to manufacturing variations, some people are lucky to get mostly "good" ones out of the box, while others aren't.

The main benefit of the Rayovac 9V is cost. At as little as $4 apiece on sale, it is very tempting. But factor in a few non-performers or accidently smoked units, and the average cost starts rising. There are many options available that may cost a little more up front, but offer better performance with fewer reported problems. There is even a lower-cost option in the form of surplus Li-ion cell phone packs that offer far greater duration at less than $2 per pack.

I don't regret having tried the Rayovac 9V, and I can understand why some people who have had good luck with them may still prefer them. But I am already having a much greater success rate with the Qualcomm 830mAh Li-ion packs.
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