Battery charging question...

[WOODMAN]

I use Nimh AA batteries in my C5050, and use a MAHA Powerex MH-C204W charger for them. These batteries are Powerex 2700 mAh, and are about a year old. They seem to lose charge fairly fast, and I usually have to charge them within 48 hours of using them to maintain full power capacity. The charger says that if the batteries are in extended storage (not used or charged for 30 days or more) to run them through the provided rejuvenation cycle, where it completely drains them and then recharges them. You first charge them, and then start the 'conditioning' cycle, which takes about 5 hours and which tends to heat up the batteries a fair amount. I am kind of wondering about this. Has anyone here any experience with this sort of thing? Any insights would be appreciated. Woody

 

[markr]

Nimh batteries discharge even when not in use. This is normal for this type of battery, although they normally hold a charge longer then 48 hours.

You can buy Nimh batteries with a low self discharge rate. I know the "Thomas Distributing" website has them.

 

[Larry C]

I use the same batteries. I've also found the little portable battery tester from Thomas to be handy for checking their charge state and viability. I've had one failure during a dive due to a bad battery. Generally, I keep enough charged to cover my weekend or trip. I try to charge them the day before I leave and rotate them on a weekly basis from my backup set to my in use set. I find that with a quick charge the night before leaving for the dive site, all my batteries for camera and strobes will last two dives. I swap them after the second dive, and if I have more than 4 dives on a trip, I go to my backup set and recharge the used ones in the motel room. I don't have the fancy rejuvenating charger so I can't comment on that, but I've been using the same batteries for two years excluding the couple of bad ones and a couple of sets I flooded. Recently, I bought some eneloops at Costco. They're supposed to go a full year with only a 15% loss of charge, so I can worry less about charging the backups at the last minute. Even though they're not rated as strong as the 2700's, they seem to last fine through two dives and I've had the confidence to just throw them in after leaving them a couple of weeks without charging. No problems so far.

 

[skywalk]

woodman, you said you need to charge them after 48hours of using. What do you use them for? if you use up a lot of charge, then you'd obviously have to recharge them, be it 4 hours, or 48 hours later.

On the other hand, if you've been using it for mabe 2 dives, and suddenly find that it only lasts 1dive before dying, then it's probably time to condition them like you said, or just buy a new set.

Incidentally, the new imedion by powerex, and the eneloops are great.

 

[mkutyna]

Rayovac Hybrids are supposed to be on par with the Sanyo Eneloops. I've only had a set of Hybrids for a month so I can't say for sure but my year and a half old Eneloops are still running strong on less than ideal charge cycles.

 

[livewire]

Woody, I have felt your pain and found the solution.

I'm also using a 5050. Was formerly using Energizer 2500mAh NiMH rechargeables. These "high capacity" batteries that are rated at 2500-2700mAh are crap. I've had the exact issue you're having... Leave them on the shelf for a few days, come back and they're dead. They've traded high capacity for some internal impedances that cause self-discharge.

I also fooled around with Rechargeable Li-Ion CRV-3's. These stink in the 5050. They worked pretty well in the C-4000 I used to have, but for whatever reason, no go in the 5050. Don't use these in your 5050 for sure.

The Best: I am now using Duracell Pre-Charged which are IDENTICAL in performance to the Sanyo Eneloops, possibly the same battery just under a different brand. These hold charge MUCH longer and are better priced than the Sanyo. I've bought several 8-packs on eBay and I'm now using them in my strobes as well. Some people prefer the Eneloops because they are white in color and easy to identify as rechargeables while the Duracells have a similar copper-top look and you might easily mistake them for regular batteries and throw them away. I'm not worried about this, but your situation may be different.

Keep your charger, but don't use the "speed charge" or "quick charge" method of charging if you have a choice. Trickle charge is much better for the life of the battery. As for what to do with the 2700mAh batteries? Use them in your remote controls, wireless game controllers, or something else. These tolerate a lower voltage output and draw less power, so you'll actually get better life out of them in these types of applications.

Hope this helps!

 

[markr]

Woody, I have felt your pain and found the solution.

I'm also using a 5050. Was formerly using Energizer 2500mAh NiMH rechargeables. These "high capacity" batteries that are rated at 2500-2700mAh are crap. I've had the exact issue you're having... Leave them on the shelf for a few days, come back and they're dead. They've traded high capacity for some internal impedances that cause self-discharge. ...

All NiMH batteries self discarge. The standard variety loose 5-10% the first day and usually less then 1% after that. The higher capacity versions usually have the worst discharge rates. The low discharge models can maintain their charge at around 75% for up to a year but they normally have a lower capacity.

While the self discharge rate is usually viewed as a short coming of these batteries, one of their strong points is the ability to discharge to a load at a high rate. This makes them charge a flash faster then most other battery types, but makes them unsuitable for slow discharge long term usage like clocks and emergency flashlights.

 

[livewire]

Here's more info on the subject, only posted for posterity, the sharing of knowledge, and for the future person who searches Scubaboard with the same issue. First a link with added battery research and information on the topic:

Coding Horror: Adventures in Rechargeable Batteries

Next, a review of the Sanyo Eneloop battery from Amazon.com by NLee the Engineer of Nashua, NH. Again, these are the exact same as the Duracell Pre-Charged. The link also gives a good product description from Sanyo which is interesting.

Amazon.com: GE/SANYO eneloop 4 Pack AA NiMH Pre-Charged Rechargeable Batteries: Electronics

According to Sanyo, the new eneloop LSD (low self-discharge) NiMH batteries can maintain 85% of its original charge after 1 year of storage. This claim is slightly misleading, because it is based on simulation test at 20 degree C. At higher temperature, the self-discharge rate is likely to be much higher.

I have tested five of those AA cells (details are given in my review for the eneloop 4-pack). The average energy loss is about 26% after less than 6 months of storage. This self-discharge rate is about 3 times higher than what Sanyo claimed. However, it is still 6 times lower than that of ordinary NiMH batteries. Therefore I'm in the process of replacing most of my existing rechargeable cells to the Sanyo eneloop.

This 8-pack Sanyo eneloop LSD batteries is a better value than two 4-pack. Thanks to lower self-discharge rate, you'll discover a lot more applications for eneloop cells in your house, such as in clocks, remote controls and smoke detectors.

But please, don't use them as emergency flash lights batteries in your car, because the higher temperature during summer time will probably nullify the advantage of LSD.

[Update on Jan 13, 2007]
I have tested six new eneloop AAA cells, dated "2006-06'. The average residue charge is 589mAh, and the freshly charged capacity is 827mAh. This implies a self-discharge rate of 29% in 7 months, which is consistent with the rate for AA cells (26% loss in 6 months).

[Update on Jan 29, 2007]
The Rayovac "Hybrid" rechargeable NiMH batteries are now available at Walmart, priced at only $[...] for 4-pack of AA or AAA cells. It is also advertised to have low self-discharge rate, but not as low as that for eneloop. The eneloop is supposed to retain 85% charge in 12 months (when stored at 20 degree C), whereas Hybrid is supposed to retain 80% charge in 6 months (no mention of temperature).

[Update on June 3, 2007]
In my 2-month self-discharge test using four different brands of NiMH cells. Hybrid and eneloop came up neck-and-neck!

Room temperature: 60-62 degree F (16-17 degree C). All capacities measured are average of 2-cells.

- Sanyo eneloop 2000, purchased Jan 2007.
Initial capacity measured: 2070mAh
Capacity after 62 days: 1796mAh (-13.2%)
(Note: my previous result for eneloop showed -18%, but I repeated the test and it did better this time)

- Rayovac Hybrid 2100, purchased Jan 2007.
Initial capacity measured: 2155mAh
Capacity after 62 days: 1859mAh (-13.8%)

- LaCrosse 2000, purchased Jan 2006.
Initial capacity measured: 1902mAh
Capacity after 62 days: 1417mAh (-26%)

- SONY 2300, purchased Sep 2004.
Initial capacity measured: 2210mAh
Capacity after 62 days: 1309mAh (-41%)

So neither eneloop nor Hybrid did as well as advertised, but they are still significantly better than previous generation of NiMH cells. So you can't go wrong with either brand.

 

[Puffer Fish]

I used to feel the same way... as all the high ones discharge very quickly and are easy to damage (drop on and it may never work again)

But recently I have found some 2900 that are great.. yes they loose power, but as primary's, they work faster and last longer.

I use Rayovac's for backup, but carry several chargers with me.

Woody, I have felt your pain and found the solution.

I'm also using a 5050. Was formerly using Energizer 2500mAh NiMH rechargeables. These "high capacity" batteries that are rated at 2500-2700mAh are crap. I've had the exact issue you're having... Leave them on the shelf for a few days, come back and they're dead. They've traded high capacity for some internal impedances that cause self-discharge.

I also fooled around with Rechargeable Li-Ion CRV-3's. These stink in the 5050. They worked pretty well in the C-4000 I used to have, but for whatever reason, no go in the 5050. Don't use these in your 5050 for sure.

The Best: I am now using Duracell Pre-Charged which are IDENTICAL in performance to the Sanyo Eneloops, possibly the same battery just under a different brand. These hold charge MUCH longer and are better priced than the Sanyo. I've bought several 8-packs on eBay and I'm now using them in my strobes as well. Some people prefer the Eneloops because they are white in color and easy to identify as rechargeables while the Duracells have a similar copper-top look and you might easily mistake them for regular batteries and throw them away. I'm not worried about this, but your situation may be different.

Keep your charger, but don't use the "speed charge" or "quick charge" method of charging if you have a choice. Trickle charge is much better for the life of the battery. As for what to do with the 2700mAh batteries? Use them in your remote controls, wireless game controllers, or something else. These tolerate a lower voltage output and draw less power, so you'll actually get better life out of them in these types of applications.

Hope this helps!

 

[WOODMAN]

Well, I am using my Powerex 2700 mAh AA's for primary use, and Energizer 2500's for backup at this time. I have heard the siren call of the Eneloops and all the rest, but then I got to thinking... These all seem to have a lower capacity, which means less usable time underwater. And, the Powerex cells do deliver the juice at high rate when needed, and always last me for at least 2 dives. They go on the charger after that, and then back in the camera within a matter of hours. So why am I whining about poor shelf life? (I usually use these in situations where power for the charger is readily available, and if I had to charge them and then hold them for several days before use, this would be a considerably different issue.) I have only the fast charge option with the Powerex charger, (other than that conditioning cycle I mentioned earlier)so putting the cells on a trickle charger is not a real option. Although...it does appear to go to a trickle charge after the charge cycle is finished, and recommends that new cells be left on charge at least overnight to maximize capacity, so... Oh well, you can make yourself crazy (crazier?:439 obsessing over details like this. I am still curious about that conditioning cycle, however, and wonder if anyone has experience with it and can tell if it does any real good? Woody