Power Tank help

[simondodd]

Long shot I know but does anyone have either a picture or circuit diagram for either the Celestron 18774/Skywatcher power tank? My dad just replaced the battery on it and managed to wire it up in the wrong polarity and has blown a couple of resistors and a diode. We are looking to find the right values for these to get replacements and wire them up. Thanks in advance :)

[SimM]

Unlikely to get a circuit diagram. If you can ask someone to take a colour photo of a working circuit board then the resistor values can be worked out. There are 3/4/5 color bands. Ordinary diodes are not too critical, they have a marking for the cathode. You could just take out the charging (or that part of the) board and use an external semi-intelligent charger - about £10 from Aldi/Lidl.

It’s probably the wrong thing to say, but you could guess the wattage (not too big they burnt out) and not too big a resistance (sufficient current to burn them out). The charging circuits are not that sophisticated e.g. the “Designer” has to solve the “problem” for only a few Cents. I noticed they leave a high voltage across the lead acid battery when it’s charged. This quickly wrecks the battery.

Really nasty chargers have a half wave (2 diodes) or full wave (4 diodes) circuit - nothing else. Even a limiting resistor e.g. 1 ohm 2W or 0.47 ohm 2W is seen as too luxurious.

So, any semi-intelligent charger will cut the voltage when it’s charged and is a good “investment” considering the cost of the battery.

Simon

Edited June 1, 2020 by SimM

[simondodd]

Yeah, I'm hoping for a picture of a working one that someone has taken when they replaced their battery Nothing so far though. Fingers crossed I studied electronics at A-levels but my dad never did although he understands a fair amount as he had to for his job before he retired, just never did circuit boards like this, he was more on the consumer and industrial electronics rather than these sorts of things.

 

Thanks