Battery life

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by Martin Field 1 on 27/04/2016 21:00:52:

"Nice big high wattage resistor". Seems a major component in your armory, Malcolm, but what does it do?

Martin

It restricts the current going into the battery. While doing this it dissipates unwanted energy by getting hot and redistributing the unwanted heat into whatever is near to it.

There is some ciphering to do figuring out the voltage that is started with (output from power unit) the voltage that is wanted (battery voltage) and thus the difference is what is dropped across the resistor. Knowing the required current, Ohms law tells the required resistor value, a bit of further ciphering tells what the minimum power rating of the resistor should be. My tendency at times like that is to go for the first available higher resistance, then a much higher wattage figure, then look for a physically big version. Physically bigger ones run cooler because the increased surface area radiates heat better and are less likely to melt their surroundings.

Hopefully a commercial product which has selectable outputs will do this for you, and, is probably te best choice if you are having to approach the subject as a consumer. Home made electric devices (especially ones concerning power) have plenty of potential for harm.

[Martin Field 1Participant @martinfield1]

A pat on the head and a ,"Don't ask, Martin" would probably have been better, but thanks, Malcolm.

<G>

Martin

[Dave MilbournParticipant @davemilbourn48782]

Martin

I'm sure that Malcolm's posting was intended for the benefit of any and all interested parties (as are mine). As I pointed out earlier, that's why this is called a forum.

Dave M

[Martin Field 1Participant @martinfield1]

Of course, but it was in answer to a specific question I maybe shouldn't have asked. But I can 't help being curious.

Martin

[Author]

Posts