Battery re-charge time?

[LagunaH1]

This is admittedly a bit of a theoretical question but still:

Does anyone have a good rule of thumb for battery re-charge time after a cold start?

I ask because the H1 very clearly uses a LOT of power when you do a cold start (cycle the glow plugs, crank the engine) and I've been wondering roughly how long I should run the engine to re-charge the batteries to make up for the drain on the batteries from a cold start.

 

[f5moab]

All depends on the amount of juice needed to start, the controlled output of the generator to charge and how much of the juice is being used to power the truck and accessories while the batteries are being charged.

 

[Hunner]

Here is my general take on that.
Most batteries accept a build up charge in a vehicle rather quickly, and like F5 said depending on other things using some of the juice. Then there is an absorption phase and then a slow float stage where the final voltage is reached again depending on draw and length of running time.
Most regulated alternators will show a higher voltage output while charging then come down as the battery reaches it's peak voltage acceptance for it's condition.
The gauge may show a higher voltage than the battery really is going to show when the engine is not running.
A digital gauge is a more accurate way to check the batteries actual voltage after sitting at rest for awhile after running the engine.
A 12v battery that reads 12v is not in too good a shape.
12.4 is fairly good so there is a fine line there between the two.
There maybe charts that show that a bit diffidently and deep cycle, gel and absorbed glass mat AGM all have different levels of charge. AGM seem to float a with a bit higher voltage. All this depends on you alternator and connections and temperature.
My dual AGM now sit at about 12.43 and have been in service since Feb 2010.
So running around the block after a really cold start may not completely bring them back to full charge.
I have dual batteries on my Cummins diesel and after sitting at freezing for several days without the block heater going it pulls some amps for that first start. I can run about 12 miles down to the fuel stop or Wally World, come out and it fires up without any problem.
I don't have glow plugs but a pre-air intake heater coil that dims any interior lights I have on during a cold start.

 

[LagunaH1]

Thanks for the input guys. Any of you H1 owners want to chime in? Do any of you have any experiences, good or bad, with this?

 

[3Hummers]

Never really thought about it.

 

[LagunaH1]

Hehe, might be another one of those things where I think too much.

 

[3Hummers]

You have two batteries. Basically one for starting the truck and one for the rest of the crap. Watch the little guage thing to the left of the steering wheel. As long as the needle stays close to 14 or gets back their quickly you are ok. If it goes higher than that for very long you probably have an alternator issue. As to how long it has to charge to recharge after a start there are too many variables to consider to come up with one answer...and yes, sometimes you think about the weirdest $hit.

 

[LagunaH1]

Well, the good news is everything is working exactly like it's supposed to: I hear the glow plug relay, see voltage drop to about 11 volts while the glow plugs are cycling, and then I crank the engine which starts right away. Once the engine is running I see about 14 volts both on the truck's own voltmeter and on the ScanGauge.

Maybe I should look into an on-board battery tender as a longer term thing.

 

[abearden]

I was always told "about 15 minutes" was a good rule of thumb. But, like 3Hummers said there are a lot of variables so it's almost impossible to say for certain (ambient temp alone will change how much current hits the glow plugs, how long the controller leaves them on, how much current the starter pulls, and how quickly the batteries recharge).

If you're worried about it, we live in SoCal. A dashboard solar panel with controller will keep the battery topped up year-round without a doubt.

 

[06 H3]

how high is too high? 14.5 volts?