[Elecraft] NiMH batteries How do I test?

[Fred Townsend]

Jim I agree with Mark but would like to add one thing. Heat is the enemy of the battery. As Mark says the heat goes up sharply at end of charge. This is how the smart charger knows the battery is fully charged. If you attempt another charge when the battery is hot you may damage the cells. This is why the charger is programed to protect the batteries. The nominal cell voltage is 1.2vdc so for 8 cells it is 9.6vdc, for 9 cells 10.8vdc, or 12.0vdc for 10 cells. The float voltage is 1.25 so the numbers are 10, 11.25, and 12.5 respective. Do not confuse NiMH with SLA which have a nominal voltage of 12.6 and float of 13.85vdc.
73
Fred, AE6QL


-----Original Message-----
>From: "Mark,  KE6BB via Elecraft" <elecraft at mailman.qth.net>
>Sent: Aug 24, 2014 4:19 PM
>To: elecraft at mailman.qth.net
>Subject: Re: [Elecraft] NiMH batteries How do I test?
>
>Jim,
>
>Good descriptions from Ray and Bob.  You are also right in that the KXBC3 has some "smarts", but it is constant current temperature monitored charger.
>
>You may also see the display message "Not 0 to 40".  It means the cell temperatures are not within the temperature range of 0 to 40 deg. C.  If it occurs on a cold day at the beginning of a recharge cycle, the cells are probably too cold to be charged, but the most likely time you will see it is near the end of a recharge cycle on a warm day.  As the cells near full charge, they convert more and more of the 200 MA charge current to heat rather than into the chemical process of recharging.  That is how NiMH cells work when recharged with a constant current.  The KXBC3 will suspend charging until the temperature drops below 40 deg. C.  
>
>This is all normal operation, and is the most common method for recharging NiMH cells.
>
>Mark
>KE6BB
>
>
>
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