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454 posts

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  Reply # 1899990 13-Nov-2017 09:11
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geekIT:

 

Thanks guys.

 

OK, I've just checked my recently charged battery and it was, indeed, sitting at around 11v. 

 

This was the result of a 5-6 hour charge and a three km drive.

 

The charger, as predicted, is outputting just over 14v.

 

So I'll do a 24 hour charge. What battery voltage would you expect to see after that?

 

Grain of salt recommended, because I've done much worse to my batteries and still use them - but I've heard that if a car battery ever reports voltage below 12v for a sustained period of time, it's suffered permanent damage. Yours sitting at 11v AFTER a 6 hour charge suggests that it's probably a shadow of its former self in capacity terms and a new battery should probably be on your short to medium term shopping list.

 

Nominal voltage is 12.6v. A healthy battery should sit at that level not only when it's fresh off the charger, but after starting the car (and then immediately turning the engine off).

 

cadman:

 

allio:

 

I have a seldom-used car with a tiny battery that’s prone to going flat (Honda Jazz) so frequently have to deal with this.

 

 

Should just get a small, cheap charge-and-maintain charger and leave it connected to that battery when it's parked up. Lead-acid starting batteries don't like being slow discharged or kept at low voltages.

 

 

I do (the Ctek MXS 5.0 I mentioned in my post is a smart charger which reverts to a maintenance trickle once the battery is charged). Unfortunately I usually park on the road, so my usage isn't perfect and the battery still takes a bit of a beating.




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Ultimate Geek
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  Reply # 1900170 13-Nov-2017 12:35
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OK, the battery has been on charge for 22 hours.

 

I've temporarily disconnected the charger as I need the car briefly.

 

The battery, previously showing 11v has now reached 13.12v.

 

Should I resume charging for say, another 24 hours?


454 posts

Ultimate Geek
+1 received by user: 248


  Reply # 1900202 13-Nov-2017 13:11
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geekIT:

 

OK, the battery has been on charge for 22 hours.

 

I've temporarily disconnected the charger as I need the car briefly.

 

The battery, previously showing 11v has now reached 13.12v.

 

Should I resume charging for say, another 24 hours?

 

 

If it's still showing 12.6v or more after being disconnected from the charger for some time, you're good.


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  Reply # 1900239 13-Nov-2017 14:58
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Recently I saw a little lithium  jump starter bank advertised that was in the form of an LED torch with a USB outlet.  Would be handy to have in the car.  I can't remember where but it would have been some sort of boat/marine retailer.

 

Most of the jump starter banks are USB capable and the advertised A-hr capacity is at USB voltage (?5v?). At 12v the capacity is less than half the advertised figure.  Or worse the capacity may be at the voltage of individual cells,which is even lower.  I always try to find out the W-hr figure and divide by 12v.  Most manufacturers don't know or won't say.  In these cases I assume 3.6v





Mike

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Ultimate Geek
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  Reply # 1901194 15-Nov-2017 12:15
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geekIT:

 

OK, the battery has been on charge for 22 hours.

 

I've temporarily disconnected the charger as I need the car briefly.

 

The battery, previously showing 11v has now reached 13.12v.

 

Should I resume charging for say, another 24 hours?

 

 

Short story, yes it would be ideal to connect it longer however that battery is in a much happier place than it was earlier.

 

Ideally the battery should top out at 14.4 volts and stay there for a few hours.

 

What is the Amp output of your charger?

 

Long story: If your charger is a bit gutless, it may struggle to get the battery to 14.4 volts - this is normal, and quit once the battery voltage stops rising. If it is a grunty charger and it struggles to get the battery to 14.4 volts this can be a bad sign that one of the 6 cells has gone short circuit. Just monitor the battery and stop if it gets warm or starts excessively bubbling and spitting electrolyte out.


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  Reply # 1901429 15-Nov-2017 19:56
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interesting how you can get a 12 volt battery to 14 + volts, its a surface charge which can be taken off by putting a load on it like turning lights on or leaving over night.

 

Depending on your type of battery it may have higher specific gravity acid which will show a slightly higher voltage after surface charge is off but no higher than 13 volt.

 

If its a trickle charger then then its most likely around 1-1.5 amp's designed to top up or maintain not charge from flat. 

 

 

 

11 volts is flat

 

 

 

 





Galaxy S8

 

Garmin  Vivoactive 3






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Ultimate Geek
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  Reply # 1902674 16-Nov-2017 11:54
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You're right. This ancient charger outputs 2 amps. It's a Carlton, made in ChCh in the70's, I'd guess. Voltage just over 14.

 

And the battery is now sitting at 13-13.1v


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  Reply # 1902734 16-Nov-2017 14:11
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From a battery performance and health perspective, an old 2 amp charger being used is 100% better than no charger at all.

 

A typical diesel ute battery such as a N70 will have an amp hour rating of approximately 70 amp hours, so it will take your faithfull old 2 amp charger about 35 hours to recharge it back to 100%. Despite being slow, this is still better than relying solely on the alternator and running around for 2 - 4 weeks with a partially charged battery.


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