Thread: Charging with external battery - possible?
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Fontus is offline Fontus
2010-03-19 , 12:14
Posts: 34 | Thanked: 20 times | Joined on Jun 2009 @ Bulgaria
#23
Originally Posted by riderman View Post
I even could test it: 3:05 hours runtime with a completely empty internal battery, 4 external alcaline AA batteries, display and gps running. I noticed, that the internal battery doesn`t get charged - its power level is at about 0% all the time (read out with kcbatt).
I think the following are the formulas one can use to compare the energy a battery can hold: 4 external AA batteries of 2100 mAh can produce 4*1.22V*2100mAh/1000 = 10.3watt-hours while a 1500mAh Lithium battery can produce 3.7V*1500mAh/1000 = 5.5watt-hours. On the other hand the voltage of the alcaline batteries drops a lot so much of the energy can not be utulised.

Originally Posted by riderman View Post
Just ordered two verry cheap BP-4Ls from Hongkong (just for the connectors to build a dummy for the internal battery leading out the cables to power it external).
Notice that these connectors are often very bad - one have to use additional support for the battery to make the electrical connection stable. And I have had a cheap battery that I was unable to use even with support.