Voltage and battery question

Hi,
I am working on building a portable 18 volt DC power supply for my LX200 (classic). My question is this: If I have a 12 volt battery that is rated at 12 amps and if I put it in series with a 6 volt battery that is rated at 4 amps, will the extra draw \ capacity of the 12 volt battery cause any problems for the 6 volt battery?

Thanks in advance for any help or suggestions you are able to provide.

Regards, Paul G.
Wisconsin

You could always get 3 identical 6 volt batteries and hook them together! ;^)
Floyd

Hi Paul,

I just checked the LX200 manual, it says the average current draw is about 1 amp with much higher draw during slewing. When you say the 6 volt is rated at 4 amps, I'm guessing you read 4 ampere/hour, which would give around 4 hours at 1 amp. The 12 volt then giving 12 hours. But since the weakest link is the 4 amp, that is your limit. I can't comment on exploding batteries, but I know the parts inside the LX200 get hot if the voltage gets a lttle low (ie. don't run your scope with 12V alone), which can burn out the internal circuit board.

Bottom line, 4 hours seems a little short, but if you just do a quick observing session, probably OK. Factor in cold conditions, and that battery will go down fast, possibly leaving the heavy duty 12V all by itself, either causing the hot circuit board, or as others suggest, heating up/damaging the 6 volt also!

A somewhat innefficient, but maybe cheap way to go is use your big 12 volt, run it into a 120VAC converter (these are cheap these days), then use your standard equipment AC to 18V supply.

David Simons