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Discussion Starter #1
I've had a very troublesome 2012 MDX, and the latest was the sudden dead battery. Got a jump to get to the dealership and they diagnosed both a faulty A/C clutch relay and failed HFL module. Unfortunately they wanted nearly $1000 for the repairs.

I did a bit of research and figured out that these were typical issues. I let them replace the A/C clutch relay and charge the battery for me. That plus the initial troubleshooting was $135.. fine. Unfortunately when I went to pick it up, the battery was totally dead so they didn't honor part of the deal. They jumped me to get home.

Got home, pulled the HFL module and attempted to charge the battery. The manual recommends to unhook the battery from the vehicle, but I've been down that road and all the reprogramming and codes scares me off. Plan B was to 2 amp trickle charge the unit while still attached. Unfortunately when doing this, my (fairly old) Die Hard charger immediately started flashing the "Full Charge" indicator on and off.

Crossroads now and would appreciate any thoughts. The battery and alternator are both less than a year old and by all accounts good. I might go buy a new charger, and one that is portable. But again, any wisdom would be appreciated. I'd note that I did struggle to find a good spot to attach the negative clamp for the charger.
 

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Try this: Turn on the parking lights for a few minutes to bring the battery voltage down a bit, then attach your charger. That may allow it to "Kick in".
 

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If the problem is resolved by replacing the faulty ac/relay and pulling the HFL unit, Both of which will be the cause of a battery drain then just take your vehicle for a drive and allow the alternator to charge the battery! This will be more than sufficient especially if you drive daily. As far as disconnecting your battery what is the big deal? the likely hood of losing programing is frankly almost nill. Programing loss is from bad HD or memory chips.


Keep in mind whether your battery is disconnected or if it dies from battery drain there is no difference , dead is dead.



Test your charger with your multimeter connect it to the charger leads and see what it is putting out in amps, and you will find your answer. If you want to believe the flashing lights on your charger than fine but i have found that is not a great indicator. The check above is simple and will tell you. The main concern is weather the battery is still good and holds a charge for any length of time, or if it needs replacing? Get it tested or you may find yourself stranded in Winter!(Cheap insurance this time of year)
 

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The battery was replaced in February 2018 and the alternator in June. I mean it could be a bad battery, but I wouldn't expect it. At that time the car lost all the settings and I was charged a couple hundred dollars for reprogramming stuff and arguing with them got me nowhere.

So update, and I'll admit that it's been ages since I charged a battery. I picked up a new charger and I can set it for 3A. I did this and it read 0% for charge initially, then jumped to 64% within an hour and stuck there.. doesn't seem to move. When I was checking on it, I could hear a bubbling or sizzling sound. I would imagine that this is not normal.
 

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When I was checking on it, I could hear a bubbling or sizzling sound. I would imagine that this is not normal.
If that noise is coming from the battery, either the battery is bad or the charger is putting out too much voltage. At 3 amps. setting, the charger should not go above 14.6 volts. If it is higher, test your new charger on another battery and confirm that the voltage stays below 14.6. If it goes higher, you have a defective charger. I had a brand new charger from Walmart go over 16 volts on known good batteries. Took it back, and got a decent charger from Amazon that worked fine.
 

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Bubbling during a charge isn't a sign of it being toast. Not saying it isn't toast, just that isn't the way to tell.
You want to put a load tester on the battery and see if it bubbles then. If it boils pretty good in a cell or two.....then toast. A load tester is a glorified heavy duty toaster element. (Not something most of us have or want to buy) Have a service station test for you.



That being said the 3 amp charge should take a day maybe two depending on battery. Your charger claims 64% after an hour so as stated you cannot reply on the cheap meters installed in these chargers, period. Do do a multi meter test on the voltage of your battery now with car not running everything off and one with it running everything off.



The new battery you had replaced could have 1 or possibly 2 bad cells ,the battery load test from a garage will tell you.

As Blue Pill and I have already suggested test your battery charger output!!
 

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Discussion Starter #7
Thanks, appreciated. If I had a load tester than I'd have already done this.

AAA told me the battery was good. The dealer told me the battery was good. I realize that neither of these means the battery is good, but it led me down this path.
 

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Dealer said to get the thing started and head that way.. they're going to replace the battery free, then do some additional diagnostics.

I will stop saying and thinking negative things about them for a brief time.
 
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