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CL7: Charging voltage

dandreye

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Hi All,

Could anyone please share the right procedure to measure the charging voltage generated by the alternator of a 2005 Honda Accord Gen7 type CG7 (2L petrol manual) and what that voltage should measure? Mine measures just under 14.1V when idling, wondering if it's high enough - but perhaps I should just be measuring it at higher rpms? Got flat battery overnight with a 5yo Ca/Ca Yuasa HSB053 battery that gave the signs of struggling lately, so just trying to make sure the charging voltage is fine and check for any leaks (alarm etc) before I buy a new one.

Many thanks in advance!
 

F6HAD

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That’s a healthy alternator. Most likely just a knackered battery. Also if your car has factory Bluetooth hands free, there is a known issue with these causing a parasitic battery drain so if the new battery does the same thing just locate and unplug your Bluetooth module.
 

dandreye

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That’s a healthy alternator. Most likely just a knackered battery. Also if your car has factory Bluetooth hands free, there is a known issue with these causing a parasitic battery drain so if the new battery does the same thing just locate and unplug your Bluetooth module.
I thought Yuasa batteries never die :) No stock BT handsfree in mine. I've just also measured the current when the car is locked and unlocked and got ~30mA in both cases to my surprise. Wondering what else besides the stereo might be contributing to that 30mA draw while it's unlocked although that's a minor concern as the car is always left locked when engine is not running. I think 30mA draw is also fine for the alarm, isn't it? If so then I can't see any faults at all, so it's time to order a new one.
Also a 2005 k20 is a cl7 not a cg7
Sorry, my bad: my previous Honda was CG9 and I confused the letters - it's CL7 indeed.
 

Channel Hopper

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Is there something in the boot (light ?) or in the front seat compartment connected to the ciggy socket ?

The glove compartment light should be out when car is locked.

Water/damp in bonnet fusebox ?
 

dandreye

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Is there something in the boot (light ?) or in the front seat compartment connected to the ciggy socket ?

The glove compartment light should be out when car is locked.

Water/damp in bonnet fusebox ?
Thanks for the hints: I'll have to check all of those. The ~30mA draw didn't look abnormal to me while the car was locked, so I didn't check for leaks any further so far. Right upon locking it the draw spikes to ~1-2A for 10-15s and then returns to 30mA and settles there, oscillating around 0.03A within the 0.02-0.04A range as per my MM, so at those modest milliamps it should drain the battery just by ~300mAh overnight. I only monitored it for a few minutes though: perhaps some much higher consumption kicks in at some point afterwards. This very battery lasted 3 weeks on alarm last summer while I was away on holiday, and still started the engine despite struggling to crank it - and now it won't even crank it once right after unlocking the car. The voltage is quite depressed right upon unlocking it indeed and keeps going up for the first few minutes, but how can it possibly get so depressed with just ~30mA draw in the first place?.. Hard to believe although not impossible that there's hardly any capacity left.
 
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smokingman

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My old battery had similar issues, left for a week while on holiday came home unlocked OK but only turned over once before it died. Final straw when it did not start on a car ferry and had to get jump started by one of the tugs used to drive trailers off ferry's. New battery problems solved.

It had one of those battery condition windows that was green even on a dead battery-what a waste of space.
 

dandreye

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It had one of those battery condition windows that was green even on a dead battery-what a waste of space.
Mine was also showing green :) Meanwhile I think I know what caused flat battery in my case: mostly very short trips averaging just 1 mile over the last 2 years, so it hardly ever got a chance to fully charge as I never cared to take it home for a proper charge until now. Besides that, being a Ca/Ca battery it ideally needs (AFAIK) a somewhat higher charging voltage to reach the 100% charge level, something closer to 15.4V while it only gets "standard" ~14.4V from the car. Anyway, I fully charged it at home and put it back in yesterday to monitor the drain over the next few days. Today morning it measured 12.6V right upon unlocking the car, which rose to 12.7V within a minute of being watched, i.e. 100% charge ***uming Ca/Ca type also falls under wet.
 
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