Battery Charging

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Battery Charging

Postby Jim Mark » Sun Apr 16, 2017 10:26 pm


I read on Google that when battery charging a MX5 gel battery you should use a 'smart charger'. This is a charger that switches off when the battery is fully charged.

My question is what happens on the car when the battery is being charged by the alternator? The alternator goes not stop charging! Any thoughts
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Re: Battery Charging

Postby drumtochty » Sun Apr 16, 2017 11:42 pm

It's a lot more complicated than you are suggesting here.

Both the Mk1 and Mk2 and Mk2.5 cars have systems that reduce the charging current to the battery when certain battery voltages are reached as most cars do and those batteries can handle that.

The battery's used in the cars would be damaged by a normal charger putting in say 10 or more amps for hours on end. If you look at the Mazda workshop manual, techs are advised to sit the battery in cold water up to half it's height in order to prevent overheating of the battery if using a standard charger and that is time limited.

The batteries used in the original application prefer a lower charge rate over a longer term and that is one reason the original batteries last 10 to 12 years if treated properly.

Therefore it is too stop well meaning owners of powerful battery chargers damaging the battery.

In saying that for owners who do not clear the cabin drains on the Mk2 and Mk2,5 cars, the battery can be damaged if water that cannot escape down the cabin drains gets to the ECU or pcm in Mazda speak that sits on the cabin firewall and the voltage regulator for the alternator that sits in there gets confused by the water in the connectors and puts 20 volts into the battery.
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