4
Yes, with the caveat that for a 500A/50mV shunt, the output will drop 50mV only with 500A flowing.
For 250A, the drop will be less, i.e. 25mV.
2
A puffed up battery is a hazard and a punctured battery is a hazard. The battery was already damaged and you damaged it more by puncturing it. It can still explode or start a fire, damaging your phone and contents in it, or it might stop working at any moment, also preventing the use of phone until the battery is replaced.
2
No.
4.2V for a lithium cell is not a lower limit, it is the upper limit. For increased cell life, a lot of products will only charge to 4-4.1V and not discharge fully either.
A battery charger does not just apply voltage to a Lithium battery. There has to be some form of current limiting implemented. Different batteries will have a maximum charge rate listed,...
2
Resistance is simply a measure of how much voltage is developed across a resistor when 1A of current flows through it.
Current measurements that use shunt resistances measure voltage directly, not current. They use the shunt resistance as a transducer to convert current into that voltage. The voltage appears directly across the shunt resistance, and thus ...
1
If there is current flowing through the contact, there is arcing potential. It is a well known cause of battery explosions when disconnecting batteries. Unless you have a zero-impedance battery bank, and zero-inductance battery connections, sparking will occur.
In practice, charge and discharge currents are large, battery connection paths are inductive, and ...
1
does the other contact take away the arcing potential
If both batteries have the same terminal voltage then, when the unreliable contact goes open circuit there should, ideally, be no voltage across that broken contact. If both batteries don't have the same terminal voltage then you should never consider paralleling them without very good technical reasons.
...
1
What is the battery nominal voltage rating? Does 12V comes from nearly discharged battery?
Most likely it's 4 cells in series (4S), Li-Ion, so it's nominal voltage should be 4 * 3.7V = 14.8V. While fully charged are 4 * 4.2V = 16.8V.
If your dead battery last readings was 12V, it was connected via 2 wires only, and now you've connected 12V power supply and ...
1
The chances of you getting in the loop of the electrical path are slim unless you are really careless with wiring the controls.
But the chances that the design will fail from seepage, corrosion etc are pretty high unless you have submarine design experience and use lubricated oil / water seals on every interface to exposed water including motor shaft.
Most ...
1
The current will find its lowest impedance path. If that happens to be your body (a good possibility, considering salt water) then it could pose a hazard.
As a reference, body salinity is about 0.4%. Seawater is about 3.5%. So saltwater is a much better conductor than the human body.
One thought would be to have a grounding area adjacent to the battery. Then ...
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