macosx said:macosx said:I've been able to charge "dead" batteries, but they aren't really fully revived, and mostly underperform. The charger is good overall, but some low performing batteries still get good numbers. Then when you actually use the battery, it doesn't last very long or if it's stored a few days, it quickly self-drains...Yes, it does "renew" the battery, but doesn't make it new, just slightly or somewhat usable. It does a great job with some batteries, but bad or "dead" batteries will also get good numbers after a renew. It's only when you use them that you discover they don't have power capacity, voltage drops quickly, current is limited, or self-drains quickly even without usage. At best some of these brought to life batteries can be used in low drain devices immediately after being charged. It's a great charger, and I highly recommend it. However, it needs a better way to tell dead batteries and real capacity... My initial impression after reading both of your posts is:

1. Your expectations for *ANY* battery charger, not just the BC-900, are too high.
   
   
2. You don't have a thorough enough understanding of rechargeable battery chemistry to properly interpret what you're observing.

1. REFRESH your cells at less than 25% of their capacity and write down the final mAh and V numbers. I label all of my cells with a Sharpie and keep a history in Excel.
   
   
2. 24 hours later, load up your cells and set up a 1000 / 500 ma DISCHARGE cycle. Check the V numbers at the beginning of the cycle and then periodically through the discharge and write them down. Start out with checking every 10 minutes. If they're holding their voltage well, increase it to 20, 30, 60 until you get a 'feel' for when they're going to hit 1.0 VDC.
   Example: a 2000 mAh capacity NiMh cell should be able to supply 500 mA for 4 hours while maintaining V above 1.0 VDC.
   
   
3. After they've cooled back to room temperature, REFRESH your cells again at less than 25% of their capacity and write down the final mAh and V numbers.
   
   
4. 7 days later, load up your cells and set up a 1000 / 500 ma DISCHARGE cycle. Check the V numbers at the beginning of the cycle and then periodically throughout the discharge and write them down.

• above 95.0000: GREEN
  
• 85.0000 - 94.9999: ORANGE
  
• 75.0000 - 84.9999: YELLOW
  
• less than 75.0000: RED

TakeTheActive said:macosx said:...I've yet to find a good method of identifying bad cells that should pretty much be disposed...

...24 hours later, load up your cells and set up a 1000 / 500 ma DISCHARGE cycle. Check the V numbers at the beginning of the cycle and then periodically through the discharge and write them down. Start out with checking every 10 minutes. If they're holding their voltage well, increase it to 20, 30, 60 until you get a 'feel' for when they're going to hit 1.0 VDC.
Example: a 2000 mAh capacity NiMh cell should be able to supply 500 mA for 4 hours while maintaining V above 1.0 VDC.

Thanks TakeTheActive for sharing your method. I was hoping there was a simple (automatic) way to get the GREEN, YELLOW, RED status out of the machine, or a meaningful number on YELLOW/RED cells after a cycle. I was trying to avoid doing manual NiMH Battery Discharge Curves and Battery Retention Curves.

This discussion leads me to think I'll be using the discharge cycle (manually and monitoring it occasionally) as a load test for batteries that have sat around a bit for a more accurate reflection of capacity instead of the reported capacity after Charge/Discharge/Refresh/Test cycles, especially for "dead" batteries (RED). Please let us know if you have a simpler method, particularly one that doesn't rely on monitoring. Thanks!

stisev said:ATTENTION FOR PEOPLE HAVING PROBLEMS WITH EMPTY BATTERIES!!

SEE THIS PIC (JPG) for the solution on 100% drained bats

There's a fair amount of discussion of that picture earlier in the thread.

stisev said:ATTENTION FOR PEOPLE HAVING PROBLEMS WITH EMPTY BATTERIES!!

SEE THIS PIC (JPG) for the solution on 100% drained bats
Yes, that's been discussed here, and some people seem to be afraid of that procedure, but even as far back as the early 80's, that is in essence the method I used to jump-start shorted NiCad, and later NiMh rechargeables: Put a brief high current through the shorted cell to break the short. I do prefer to first try to get the battery above 1.Volt using a cheaper charger, but if that doesn't work, then the brief high current usually does the trick.

I recently got myself a BC-900, and so far, out of 24 older AA's, I've only had to jump-start one, and 3 others required a couple minutes in another charger first. Unfortunatey those 4 still test very low, and I have to run them through a refresh after the set currently under test is done.

I've been logging the test and refresh results of all my batteries, and maybe I'll post the spreadsheet here after they're all done, if anyone is interested. There are some interesting differences between sets.

- Eric

does anyone else know of a good charger like this cheaper at any other place?

You snooze you loose.

Kien said:Ok this is not hot. The price went to up $68.84 now. What's going on at Amazon ?

stevesomething said:It's back @ $39.38! Better hurry up!
Just placed one, thanks for alerting.

It was just droped from $59 to $48.69 yesterday! I hope it will not drop to $30 tomorrow

in41
Thanks for the update... missed the last one by less then 1 hour so been waiting...

$39.99 now

people just buy it....I have small kids and lots of batteries and my lacosse is used almost 24 hours a day every day. Works like a charm. Best "toy" I ever bought.