Why don't the charge terminals on these short out in water?

Thread Starter

Joe Stavitsky

Joined Apr 5, 2020
107
These are charged using a physical connection (_not_ inductive coil) in a case, but they have an IP rating (safe for use immersed in water). Why doesn't the water short the battery? Is there some kind of "proximity interlock" with the case (some kind of magnetic sensor, I guess?), or do that some other way?

Thanks so much

Joe
 

Papabravo

Joined Feb 24, 2006
19,592
Well, the kind of water the device is immersed in has a huge bearing on the conductivity. Distilled water (0.05 μS/cm) does not conduct so well. Seawater (50 mS/cm) is a different story, as is drinking water (200-800 μS/cm)
 

Papabravo

Joined Feb 24, 2006
19,592
No, I'm positive it's rated for seawater. I know it's rated for pool water.
Take the reciprocal of the conductivity to get the resistance.
0.05 μS/Cm is the equivalent of 20 MΩ/cm - not much current is going to flow there
800 μS/cm is the equivalent of 1.25 KΩ/cm - less resistance than distilled, but not as much as seawater
50 mS/cm is the equivalent 20 Ω/cm - low but not exactly a dead short

If there is no potential difference on the terminals there is nothing to short out when they are in the water. Why do you think either terminal is capable of sourcing current? A simple diode internally would prevent that.
 
Last edited:

Thread Starter

Joe Stavitsky

Joined Apr 5, 2020
107
Take the reciprocal of the conductivity to get the resistance.
0.05 μS/Cm is the equivalent of 20 MΩ/cm - not much current is going to flow there
800 μS/cm is the equivalent of 1.25 KΩ/cm - less resistance than distilled, but not as much as seawater
50 mS/cm is the equivalent 20 Ω/cm - low but not exactly a dead short

If there is no potential difference on the terminals there is nothing to short out when they are in the water. Why do you think either terminal is capable of sourcing current? A simple diode internally would prevent that.

Honestly I didn't even think of any internal circuitry before the battery. Guess I'm still coming off my health funsies.
 
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