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Old Jun 1, 2005, 5:37 PM   #1
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I bought an overnight AA Nimh 4 battery charger (Delkin) which came with 4 2300mah batteries. Their instructions were for 1500mah batteries to be charged 16 to 18.5 hours for four. I need to know how long to charge two 2300mah batteries and figured about 18 hours, but I'm not sure. It's supposed to turn off when it is done, but I let it go nearly 20 hours and it was still going so I unplugged it as I did not want to burn up the batteries. I know I should get a more expensive charger, but if I can't right now, does anyone have a good guess on length of time to charge two 2300mah. Thank you.
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Old Jun 1, 2005, 11:57 PM   #2
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1500 ma / 16 hr = 93.75 ma/hr
2300 ma / 93.75 ma/hr = 24.53 hr
roughly
1500 ma / 18.5 hr = 81.08 ma/hr
2300 ma/ 81.08 ma/hr = 28.37 hr

If my math is still any good.
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Old Jun 2, 2005, 3:26 AM   #3
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Chargers today cover such a wide field that its best too stick too a well known brand and use their batteries. I have quite a few modern chargers , those that discharge before charging.Not needed on NIMH batteries. these express chargers that go on too trickle charge when completed. There is one well known make that people complain about, that says fully charged, but they soon run out. Best too rig up a simple tester to see if the fully charged batteries supply the stated current for 1 hour.
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Old Jun 2, 2005, 5:25 AM   #4
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First you need to figure out what is the charge current. Look at the back of the charger or at the manual. Once you have this you can calculate the charging time as follows:

cell capacity (mAh)/charging current (mA) x 1.4

say if your charger charges at 100 mA 2300/100 x1.4= 32.2 hours

I should say that I wouldn't recommend such a charger for anything other than breaking-up new cells
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Old Jun 2, 2005, 10:05 AM   #5
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OK. The back of the charger says output 130ma. So using any available info above I come out with 24.7 hrs for 4 2300mah batteries. But if I only charge two at a time, is there another formula for figuring that, like how much timeto deduct. Thank you all so much for the info so far. And why does the last poster feel the batteries will be ruined. It seems to me that a very high voltage, fast charge would do more damage. Thanks again.
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Old Jun 2, 2005, 3:33 PM   #6
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In the days of yore when rechargables hit the market it was said too recharge at 1/10 of the batteries ma/hr. That is 45ma for 14 hours for 450 ma nicads. I still believe that a long shallow charge is the best. When batteries are in the charger sometimes they are in series parallel How they are wired up makes no difference whether you charge 2 or 4regarding time.
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Old Jun 3, 2005, 9:24 AM   #7
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mes444 wrote:
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OK. The back of the charger says output 130ma. So using any available info above I come out with 24.7 hrs for 4 2300mah batteries. But if I only charge two at a time, is there another formula for figuring that, like how much timeto deduct. Thank you all so much for the info so far. And why does the last poster feel the batteries will be ruined. It seems to me that a very high voltage, fast charge would do more damage. Thanks again.

It may seem counterintuitive but NiMH cells like to be fast charged at high currents, providing the fast charge is terminated when full charge is reached. Slow charging aids crystalline formation, which is the reason for voltage depression (misnamed memory effect). At currents lower than 1/10C or in your case 230 mA full charge is difficult to achieve due to low charge efficiency.

I don't think your cells will be ruined, just that you can get more out of them and save quite some time by getting a better charger.
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