Model Boat Mayhem
Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: bbdave on October 19, 2011, 10:18:03 pm
-
I have noticed on some model subs the battery teminals are just brass bolts through the WTC why do the batteries not just short out?
Dave
-
I use an electronic total dissolved solids meter for testing swimming pool water quality.
It reads the TDS by measuring the conductivity in the water sample. So the higher the dissolved solids, the more conductivity in the water.
This means that your battery terminals will leak voltage according to how much TDS level is in the water.
Pool water can be very high in solids ( minerals ) because the pool does not get drained out often enough.
Salt water is very high in solids. A digital TDS meter is affordable and every sailing club should own one.
Regards,
Giovanni
-
the system that is used on my Sheerline Akula is a bolt through the end plate which is the -ve pole which has a nut to keep the connection tight, with a push fit rubber insulated female socket/ plug affair which is +ve the battery +ve post being sealed with silicon prevents shorting of the battery I find the system easy to use and maintain.
Regards Mark
-
In its most simpest form, the circuit is already closed as the electronics inside the tank are drawing current. So it does not matter if they are shorted, so long as you remember to turn the thing on ;)
That should answer your question.....
Andy :-)
-
In its most simpest form, the circuit is already closed as the electronics inside the tank are drawing current. So it does not matter if they are shorted, so long as you remember to turn the thing on ;)
That should answer your question.....
Andy :-)
Not quite, Andy - you want the electric going through the electronics, rather than the outside of the WTC. If the sub is in fresh water (the usual condition, since radio signals soon vanish in salt water) then said water will have fairly low conductivity. The only problem on the way would be early corrosion due to electrolysis.
Many things dissolve in water, not just solids. The vast majority, not just common salt, will turn the water into some sort of electrolyte. Again, some are more active than others and all will have their own characteristics regarding their level of activity regarding both corrosion and absorption of radio waves. Dunking a 5 cell stick of AAA cells in real salt water has resulted the end of the positive-most cell being blown out, so sea water is very conductive.
-
Yes as Malcolm says.
but most of the time, you'll get away with it as our boats / subs are only in the water for a matter of minutes or hours and are usually
allowed to thoroughly dry out in a centrally heated house afterwards...
-
so are we saying as long as the circuit is complete the path of least resistance is the copper wire rather than the water? there must be some current drain on the exposed terminals or is there a minimal distance between them?
Dave
-
I expect there will be a little loss, but then running your batteries in the drink chills them, and that leads to loss of capacity too- probably far more than any current lost due to mild conduction in fresh(ish) water.
You can apply a little waterproof grease to the terminals to keep the terminals nice and shiny.
-
I was thinking more of the batteries in one wtc and running power to another via bolts through encaps
Dave
-
In that case you have the option of running the cables through hosing (e.g. silicone tubing) between the two cylinders.
-
Covering the terminals with tubing loaded with silicone grease should work fine. That sort of thing used to work fine with underwater cables, or at least, cables underground where the water table came up for a look. As long as there is unbroken insulation, be it the plastic cable sheath or non conducting, water repellent grease between metal carrying electricity and water, no problem.
-
AAHHH didn't think of running tube DOH! over thinking the problem again
Dave
-
those of use that use this methodology to transfer electricity from an external battery into the WTC will generally smear a dielectric grease over the connections to keep water from corroding the contacts.