[Elecraft] KBT2 charging

[Ron McDowell - W5RCM / ZS1MCD]

According to the builtin volt meter on my K2, my old Astron RS-20A is putting out 13.3V (which I understand to be really more like 13.5-13.6 because of voltage drop across the diode).  A couple questions regarding that and the KBT2:

1.  Is that adequate voltage for charging the KBT2?  The battery manual calls for 13.8V.

2.  Is it OK to leave the red battery switch on the back of the rig ON whenever I'm using the K2 on the power supply...in other words, am I running any risk of overcharging the battery?  Or should I switch the battery off unless I'm running from (or charging up) the battery?

Thanks for the input!
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72, Ron - W5RCM / ZS1MCD
Austin TX / Hermanus ZA