NiMHs + BC 900 = dead batts, What did I do wrong?

[jchock]

I've had a BC 900 (v. 32) for over a year or so now as it replaced my Maha C401FS (that fried batteries when the power supply started making whining noises) and my older Ray-o-vac PS4B 1hr house burner.

The Maha killed all of my 2100 Sanyos (16 of them), my Nexcell 2100 set (4 of them), the ROV PS4B killed all my 1800 GPs (16 of them). By killed, I mean either they wouldn't hold a charge, or they wouldnt' charge on the chargers at all (blinking red lights).

So I started off with (new) 16 Duracell 2650s and four Sanyo 2700s in the BC-900 last May (Sanyo)/June (Duracells). Somewhere I lost 4 Duracells, but I still have the other 16 batts.

In the past two months, I've noticed that the batteries just don't hold a charge. As in, if I take it off the charger, and let them rest, the next day, they're not 1.4V (as it said on the charger when I took them off) but 0.88-0.95V. If I take them off the charger, "fresh" they won't power my lights or camera flash. The lights won't turn on (where they're bright if I use AA alkalines or lithiums) and the flash (if it powers) just whines, but never seems to charge the flash circuit. Sometimes they won't power my portable CD player.

The readings on capacity have changed as well. When I first get the batteries, I write their charging capacity (to match them) after I cycle them a few times. The Sanyo 2700s for instance read about 2750-2790 mAH on the BC900 when I first used them. More recently, one won't charge at all (null) and the other three, when charged at 200 mA and at 1000mA will read about 3300-3400mAH. That would be a great amount, except I think either the charger is broken, the charger has killed the batts, or the batteries are somehow discharging over the 18 hours on the charger and that's why they end up with such "fabulous" readings.

I have generally charged the batts at 700mA to 1000mA if only because I would really need all 16 batts charged for the weekend to power the camera flash and that was the fastest way to go... More recently I've tried the 200 mA setting, but I haven't seen any revivals or improvements...

I doubt I've charged each battery 100 times, let alone "thousands" in the past 9 months, so what have I done wrong to make these batts the way they are? Is it me or the charger? If one kills $50 in batteries every 6-8 months, is it really worth the infrastructure in chargers and batteries?

Any suggestions on where to go now?

Thanks!

 

[ginaz]

i would look to the batteries more so than the charger. higher capacities seem to go hand in hand with higher discharge rates. i've only had troubles with energizers though, and have found the hybrids with their "meager" 2100mah to be just fine for me.

 

[jchock]

So I can look forward to only 6mo of use from my batts in the future because the expensive high-capacity, high-drain ones will only last a few weeks at peak use?

 

[elgarak]

What was the status of the batteries when you charged them?

Did you ever used the discharge mode after the initial break-in?

Did you try refresh/discharge mode of the BC-900 to recover them?

EDIT: Let me elaborate. Way back when I started with rechargeables, no one believed the "NiMH have no memory effect". So I bough a simple, $20ish charger with a discharge function (timer controlled). I used the discharge every time, and had no problems.

Switched to a AccuManager20, which, according to the manufacturer, charges so intelligently that you don't need discharge. However, I never got the runtimes I should with Ansmann 2400 mAh; waaay shorter runtimes, in fact.

Bought the BC-900, use the discharge options always, and charge @ moderate currents (700 mA max), and have no problems, and finally get the Ansmann 2400 mAh FULL.

Personally, I believe that all Ni chemistries DO have memory effect, need relatively far discharging that is never reached in the application, and that high charge currents kill them (high current: >1000 mA for AAs, regardless of capacity; actually, I think it's the slight overheating that kills them).

 

[oldvultureface]

I too have had issues with "high capacity" cells over the past few years. Like getting 15 shots with freshly charged batteries and the camera does a low voltage shutdown on a scenic helicopter flight in Hawaii.

For the last three months I've been using LSD (low self-discharge) cells (Sanyo eneloop and Rayovac Hybrid) and have been pleasantly surprised by their performance in my photography equipment.

I've been using a BC-900 with good results.

 

[jchock]

elgarak,

Status: discharged. They would not operate any equipment. BC-900 said they were .9V.

Yes, I use the discharge and test cycles of the BC-900.

In fact, I used the discharge system on all of the batteries over a couple days and by the time I was done, the first couple of sets were already dead. For a bit I thought that the discharge/refresh mode didn't charge the batteries when they were done, but it does and the batteries simply self-discharged at an extremely rapid rate (1-2days).

 

[SilverFox]

Hello Jchock,

Interesting problem...

When you use your cells, how low do you discharge them?

Did your 3300 mAh number refer to a charge capacity, or a discharge capacity?

Have your cells been exposed to temperature extremes (high temperatures more than low temperatures)?

Did you happen to get angry and throw your cells on the ground, or did you happen to drop them out of your car window when traveling down the road?

Well, that's about it for dumb questions, but I am looking for outside sources of damage as a possible cause.

On the other hand, if you charger was showing 3300 mAh during a charge, something is wrong. I believe V32 has a 2700 mAh limit. With V33, they bumped that up to 3000 mAh, but that is still below your 3300 mAh observation.

Now I feel we are getting somewhere... We have narrowed it down to either cells going bad, or a bad charger. Oops, that's where we started...

Put your discharged cells in the charger and select a 1000 mA charge rate. Set a timer for 2.25 hours. You should be near the end of the charge, and can watch the last 15-20 minutes. The cells should heat up toward the end of the charge, and the termination voltage should be around 1.48 volts.

If all goes well with the charge, you now need to pick a light to put the cells in for a runtime test. If you have a direct drive light, that would be best. If the light runs for the correct length of time, but is dimmer, your cells have developed higher internal resistance. This would also account for your flash recycling problems. If they show a reduced runtime, they may be at the end of their life.

If you have, or can borrow, another charger, you could also try that and see if that makes any difference. The other option is to get some new cells and see if the charger works properly with them.

Let us know what you find out.

Tom

 

[jchock]

Tom,

how low: Until the electronic device quits working. I don't know what charge was left. It may be days until I get around to charging them even after they're "dead."

3300 mAH: that was during charging. Discharging is sometimes 1700, sometimes 2000, whatever the cell happened to be at when put in the charger. I don't recall the results from the discharge test on the BC900

No extreme temps, no damage from deliberately dropping them, running over them with a car, etc.

I've harbored a theory that my power lines are noisy or have loops and have damaged the wall warts for my chargers, but that's only because I don't like the whine my MH-C401FS wall wart makes (and that all the batteries charged in it are all dead).

Termination voltage in my charges changes from 1.31V to 1.46V. The 1.31V ranges seem to be the ones that charge to 3300 mAH. I've seen voltages near end at 1.29V after I let the cells settle in the charger ("FULL") for a couple hours.

I'm inclined to think all my batts are about dead, but I'm trying to figure out if I've done something to prematurely kill them (as all my other NIMHs have died) or if the charger(s) are simply killing them over time for some reason.

As for available chargers, I have:
- a PS4B 1hr house burner (batts aren't as hot as the older PS4), I just don't use it because of the the hot batteries. It replaced a PS4 that caused some 1800GPs to burst.
- a PS4 on a shelf that I don't use after it's twin blew up batteries.
- a Lenmar Gamma 1 (at least one channel won't shut down properly and it kills batteries)
- a Maha C401FS that has a whiny wall wart (I think it kills batteries with inconsistent current)
- a LaCrosse BC-900 (the charger in question)

I forgot about my LenMar 2300s (all dead) killed in my maha after about 3 months of use and the first set of ROV 1600s (PS4B heated)...

I just don't seem to get these things to last very long whatever I do...

 

[SilverFox]

Hello Jchock,

My gut instinct is that there is a problem with your charger. V32 should not charge above 2700 mAh, the ending voltages should be above 1.29 - 1.31 volts, and your concern with the quality of your power all factor into this.

If you really think your power is dirty, you should get a surge suppressor and plug your charger into that. This may not help your current chargers, if they have been damaged, but will help protect a new charger.

It is possible that your batteries are used up, but it doesn't seem that they should be.

You need to evaluate your charger and your cells. One thought is to hook up with a local RC flying club. They should have advanced chargers that would tell you if your cells are "crap." I don't know where you are, but a quick Google search shows clubs in Harrisonburg and Vienna (first two hits). Another option is to contact your local RC hobby supplier.

If you don't mind waiting a little, you could send me your cells and I would be happy to do a quick check on them. If they are "crap," I would recycle them for you, but if they are good, I would be happy to ship them back to you. If you want to go this route, PM me for my shipping address.

Another option is to purchase another charger. I see that you have no other chargers available, at least that I would recommend using to evaluate this problem, so you would need to get one, or maybe you could borrow one from a friend.

Tom