Battery Help

[Ed Blough]

I have a Makita 14.4 Ni MH 2.6 amp system. On one battery if I put it in the charger it will be there about 5 minutes and the charger signals it is finished and goes into top off mode. If I use the battery it is fully charged but will drain in about 3 minutes.

I have measured the battery after charging and it reads 14.4+ volts. So I think that is saying all cells work. Since it reaches full charge and seems to have good amperage for a minute or two I'm confused with what could be wrong. The battery can sit on my bench for about week and still have a charge so I don't see a short anywhere.

I would think if a there was a bad cell the charger would tell me yet the charger seems to think everything is great. I have tried to cycle the battery with little change in charge or discharge rate. I tried to put them in the freezer, but chickened out after about 30 minutes. I even tried to reverse charge it but all that did was make the battery hot.

Other than getting a new battery anyone have any idea what could be wrong and or how to fix it?
Thanks so much

[Steve Clardy]

I'll send this link to Jason the battery man. Maybe he can help you.

[Jason Abel]

Your batteries are not dead they just lost the ability to hold the charge. Consequently, they will still read approx 1.2V per cell thereby tricking your charger into thinking everything is ok. I haven't found the freezer trick to work to well during any of my testing. In order for the cycling trick to help you need to be able to effectively discharge your battery at a high yet stable rate. When I cycle packs to try to bring a little more life into them I do a peak charge on my charger and then discharge them at 6A until the battery pack reaches a voltage that is equal to .9V per cell. (9.6V=8cells, 12V=10cells, 14.4V=12cells, 18V=15cells) Taking the battery lower than this voltage will run the risk of polarity reversal. This occurs when the batteries are drained to far by (hooking a small light bulb up to it, taping the trigger on your drill, etc...) All of these are bad habits and are not good for your cells.

Hopefully this helps you out. I can rebuild it for you if your interested. I just got a new spot welder in my shop so I'm like a kid with a new toy!!!

Jason
"The Battery Man"

[Jason Abel]

Oh yeah, when I cycle the batteries I let them come back to room temperature prior to charging/discharging each time. I generally cycle the pack 4-5 times.

[Reg Mitchell]

batterybuilders@verizon.net (batterybuilders@verizon.net)

[Steve Clardy]

batterybuilders@verizon.net (batterybuilders@verizon.net)


Thats jason above, from batterybuilders, post 3 and 4.
Does terrific work

[Reg Mitchell]

didn't even look...hes a knowledgable guy and just thought i would get his name in here...

[Steve Clardy]

didn't even look...hes a knowledgable guy and just thought i would get his name in here...

Very. Did 5 batteries for me. Great Service.:D

[Jason Abel]

Thanks guys. I try to help whenever possible. I would love to post more often. I have been trying to get ahead before the holidays. If there is anything else I can help with please let me know.