CCrane charger anomaly

[FalconFX]

Okay, here's the scenario...

I put 4 batteries (actually 8, 2 sets of 4) I got from OnlyBatteries.com, 4 C sized NiMH 4500mah batts, into the CCrane charger around 8:30am yesterday morning.

The batteries, as measured by the CCrane, had 1.28V left in all of them; quite uniformed. I then put them into the charger, and it has been charging them ever since.

Today, at 3:50pm, after over 31 hours of charging those SAME 4 C cells, I'm getting 1.40V and it's still charging. I took the batteries out, and found out that one of them has overheated so much that the green shrinkwrap on the battery has been torn at the bottom of the battery base...

What's going on here? The other batch of 4 batts went right into the Vanson yesterday evening and came out today morning fully charged. Am I missing something about the CCrane and these particular batteries? I haven't had this problem with the 8Ah-9Ah D cells...

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[Brock]

Not to knock the charger, but that is the reason I like the vanson, or any charger that has independent charging circuits. The one cell you have might be bad and since it isn't coming up to voltage all the power from the charger was going in to it, as you can see, this is not a good thing.

I would let them all cool down and pop them in the vanson and see what happens. I bet that cell is bad though.

 

[FalconFX]

Yeah, I'm starting to think that way as well... It's wierd, because all 8 cells tested 1.28V across initially, so it's kind'a puzzling. Maybe one of them's just not accepting current or something.

I've gone through and started charging in pairs of 2 now. So far, so good with the first 2.

It's too bad you have to have the lid closed for charging the batteries. Logic will tell you the lid being closed just adds on to a pressure cooker type atmosphere. I'd always leave my Vanson lid open or my Maha 401 lid open, but this guy's a no go...

 

[vcal]

Falcon-you have pointed out one of the few weakneses of the Crane unit.

Only thing to recommend...-especially with New or Untested cells is to charge em one at a time, on the first cycle..-kinda obvious solution I guess..../ubbthreads/images/graemlins/icon3.gif

 

[FalconFX]

Thanks guys... I'll go 1 at a time... Try to isolate the problem...

 

[Sigman]

Yep, happened to me = bad cell!

 

[Floating Spots]

While the CCrane charger does charger in parallel (which personally I don't think is bad), it does have thermal sense. When I took mine apart, I discovered thermistors attached to the metal negative contacts just below the plate on every battery post. This should have limited the charger. My guess is that you had a bad battery, it heated up, the charger stoppped and the other batteries dumped energy into it. Normally this wouldn't happen, unless there is a large delta-v (no I don't consider 0.1v a large delta-v), or the internal resistance drops, or the cell is really freakin hot while the others are not.

 

[SilverFox]

Hello FalconFX,

Help me understand this.

I was under the impression that you closed the lid on the battery charger for two reasons:
1. so that the contents are contained if the battery blows up, and
2. so that the thermal protection works properly.

I don't worry too much about batteries blowing up, but is it better to compromise the thermal shut off of the battery charger?

Tom

 

[FalconFX]

SilverFox,

I usually leave the lid open on my Maha or my Vanson to allow for airflow. The Rayovac PS3 actually SPECIFICALLY warns its customers against closing the lid on its charger when charging NiMHs. Sometimes, like on the Maha in its 100 minute charge mode, I'd put a soft fan on top of it to blow air onto it.

I wasn't aware that the lid needed to be closed for thermal protection. If that was the case, then differences in ambient room temperature would cause a tremendous difference in charge capabilities and compromise your batteries and the charger.

Plus, if that was the case, I would hope CCrane would warn its customers that ideal thermal protection of the charger not be compromised by not placing it in very hot or very cool areas.

In any case, I'd hope the thermal protection is independant of the need to keep the lid close, because it should be monitoring the temperature change AT the battery ITSELF, not the ambient air temperature inside the charger...

 

[highlandsun]

The docs for the Maha 401 say to always leave it open for charging.

 

[eluminator]

If you're clever you can get the C Crane charger to work with the lid open. I whittled down part of the handle of a plastic spoon from Wendy's. When I stick it in the slot in front of the battery compartment, it closes the switch and the charger thinks the lid is closed.

This smart charger isn't so smart after all.

 

[Quickbeam]

Rather than charging the cells individually, test them. Place one in with the lid open, press the "battery analyzer" button and see what happens. Keep the lid open. If one is bad, it should show up if you test them individually. Cycle each one through the test a couple of times. This is how I found a bad cell in my batch with the CCrane.