When I bought my M20, it came with lots of extra goodies, including a new, never used and still dry, lead acid battery. Now that I am getting to the point of hooking up the electricals, I noticed that the polarity markings are opposite between what is marked on the terminal and what is marked on the case. I’m thinking that I can just go with the case marking and obscure the ones on the terminals to eliminate confusion. However, that is making the assumption that the polarity can be either way, depending on how it is charged. Are the internals neutral until charged, or does it have to be charged in a specific direction? If the latter, how can I tell which is the correct polarity?
Check to see whether the battery is dry charged. If no charge is showing then you can charge it the other way round just remember to mark the terminals.
When I bought my M20, it came with lots of extra goodies, including a new, never used and still dry, lead acid battery. Now that I am getting to the point of hooking up the electricals, I noticed that the polarity markings are opposite between what is marked on the terminal and what is marked on the case. I’m thinking that I can just go with the case marking and obscure the ones on the terminals to eliminate confusion. However, that is making the assumption that the polarity can be either way, depending on how it is charged. Are the internals neutral until charged, or does it have to be charged in a specific direction? If the latter, how can I tell which is the correct polarity?
NO the battery can not be charged in either direction.
The + plates & the - plates are made from a different alloy and the paste on the + & - plates are different.
When filled with acid you should be able to get a voltage reading.
Let it sit overnight if not longer.
Then stick your voltmeter on it to determine the polarity.
You can not get any voltage reading without any acid in there because there is no circuit and no electrons free to move from one plate to the other.
Now that is very strange, because when I was an AA patrol man I came across many instances of people jump starting flat batteries the wrong way round. I can assure you that they had reversed polarity. It was a devil of a job trying to flatten the battery and recharging the correct way round. Of cause in some instances they had attempted to start and blew the ecu.
Bearing in mind how messy and damaging a failed battery case can be and how annoying a flat battery is, I don't think I'd use the battery you have received, even if it didn't cost anything. There is clearly a quality control aspect here !
