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Battery Discharge problem


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For over 12 mths the boot will not close properly so when engine is stopped I have to ensure the "open door" light is not showing on the dashboard, or Battery goes flat.  Managed with that so far.  Past 3/4 months the heating system which is usually on lo, air conditioning on, fan on at various speeds,  used to be the same when I turned the engine back on.  Now it's gone to temp of 22, and the front widscreen defogger is flashing.  I have to change it back to the way I want it.  Now the Battery is flat.  So has the heating system caused that?  How when engine is off?

Sorry if following questions are daft:


1.  To recharge Battery with Battery on car do I just need to detach the negative terminal, then attach Battery charger?

2.  In the book it says only do a slow charge, (5A or less) or Battery may explode.  What does slow charge mean.  With my lawn mower and cars in the past, have just put the Battery charger on, gone away, come back hours latter, all well.

3.  I take it the car, windows doors etc will work after disconnecting and then connecting Battery?  Or is that complicated as well?


Thanks in advance.

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It's not really necessary to disconnect the Battery as long as you're using a modern, intelligent charger with a clean regulated output.

They have to put that warning in the manual just in case someone is going to use an old transformer-based charger that would have a dirty output, which could indeed damage the car's electronics.

An example of a modern intelligent charger is the CTEK MXS 5 here, but others are available.

As for the charging current, a charger like the CTEK will take care of that for you. Usually, the device being charged will determine the current draw but this is one reason why these are called 'intelligent' chargers.

If you do disconnect the Battery to charge it then yes, the windows and sunroof if there is one will probably need to be reset but you'll probably be able to find instructions on how to do that either in the owners manual if you have one, or a video on YouTube, or just a general googling.

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