So I put in a 16V Rock Battery and was just curious. It says 17.2V but with all accessories on and car not running it drops to 15.6V, is this normal?

Yes there will be a draw when running accessories. I run an alternator and with everything going and engine running im at 17.5V

quote:

Originally posted by Bob Payton:
Yes there will be a draw when running accessories. I run an alternator and with everything going and engine running im at 17.5V

But with everything on and the car not running should it be as low as 15.6V? That seems low to me and almost like the battery is shot.

Is this a new battery? I’ve only used one rock and I didn’t have good luck with it at all… but maybe that was me

it all seems low to me.the ign will drop it even more.

In 10 years I have only had one 16V battery fail and it was a Rock battery. Your results may vary

Thanks everyone, yea anything below 16.0 worries me so im gonna yank it. Its only a few months old.

I would say that you should do the same test with a known good 12 volt battery and see what result you get. I think you'll be surprised.

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Originally posted by Wild Wild West 2:
I would say that you should do the same test with a known good 12 volt battery and see what result you get. I think you'll be surprised.

Surprised in what way?

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Originally posted by Bob Payton:

quote:

Originally posted by SmokinChicken:

quote:

Originally posted by Bob Payton:
Yes there will be a draw when running accessories. I run an alternator and with everything going and engine running im at 17.5V

But with everything on and the car not running should it be as low as 15.6V? That seems low to me and almost like the battery is shot.

Do you have an alternator?

Yes, it starts to put out around 1800 RPM. at idle it does not.

If its over 17V at while running i Wouldnt worry about it. You can always change the pulleys on the alternator or crank to charge more. I had to do that with my nova cuz i run more electronics.

quote:

Originally posted by Bob Payton:
If its over 17V at while running i Wouldnt worry about it. You can always change the pulleys on the alternator or crank to charge more. I had to do that with my nova cuz i run more electronics.

Yea I agree but I'm mainly concerned that it may be bad. I let it sit overnight last night and it dropped from 17.2 to 16.7 with nothing on it.

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it starts to put out around 1800 RPM. at idle it does not.

Before you blame the battery, consider getting the charging system in order. If I were 16v, I’d want my charging system very close to 18v at 1200 rpm with ignition, pump, fan, lights and trans brake energized.

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Originally posted by markemark:

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it starts to put out around 1800 RPM. at idle it does not.

Before you blame the battery, consider getting the charging system in order. If I were 16v, I’d want my charging system very close to 18v at 1200 rpm with ignition, pump, fan, lights and trans brake energized.

So your saying on idle I should be charging 18V? If so them what pully do you run?

quote:

Originally posted by SmokinChicken:
Yes, it starts to put out around 1800 RPM. at idle it does not.

If you give it a 'blip' to 2,000 RPM or so to excite the alternator, it should remain charging once the engine goes back to idle, right?

quote:

Originally posted by SmokinChicken:So your saying on idle I should be charging 18V? If so them what pully do you run?

2 to 1 pulley ratio is what I use, and a PowerMaster 150 amp GM type alternator rated to 18,000 rpm with 2 gauge wire. I’m on 12v, but my charging system maintains 14+v at idle in gear which is 1200 -1300 rpm.

If I were 16v I’d have 140 amp that outputs 90 amp at idle. That 90 amp output is achieved at 2200 to 2400 rpm alternator speed by Powermaster.

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Originally posted by Lenny5160:

quote:

Originally posted by SmokinChicken:
Yes, it starts to put out around 1800 RPM. at idle it does not.

If you give it a 'blip' to 2,000 RPM or so to excite the alternator, it should remain charging once the engine goes back to idle, right?

If you are running a Ultra Mini Alternator for 16V its probably 55 amps (Most run these) then when you blip the throttle it will not stay charging. It should only charge once its at the desired RPM range. This 55 amp charger is perfectly fine for maintaining a battery during a run. many will still put a charger on the car in between rounds as well. So if you go changing pulleys to get it to charge at 1200RPM you may have some issues when at WOT.

2 gauge wire on an alternator that's a mini is way way overkill. 12V system is not the same as a 16v system. When a 12v system gets below 12v stuff stops working and car wont start. When a 16V battery gets below 16v things will still work and car will still start.

The 16v battery when fully charged should be between 17.1 and 17.5v. If you let it sit over night it should not drop out of that range in that short of a time. Also when everything is on and engine not running it should drop but then when everything is off it should return well above 16v and probably almost back to 17.1 ish.

This message has been edited. Last edited by: Da Shoe,

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