Battery light on at idle, off at 1,100 RPMs- a first for me

[Kioti Paul]

Reading 12.8 volts at the battery at 2000 ERPM is absolutely abnormal and a clear indication that something is wrong with the charging system or the wiring for that system.

No one said 12.8 volts is normal!

Several people (including myself) did say that it is not uncommon for a "new" battery to be in a "not fully charged" state when you purchase it, and that it can take an hour or more (at 2,000 RPM) to bring it up to full voltage. I stand behind that assertion. Are there any deniers of that assertion?? Seriously, I would welcome a civil, respectful, discussion with people of differing views.

The only point I was trying (poorly) to make was that before spending a lot of effort, and / or money chasing gremlins that may / or may not exist, make sure the "new" battery is fully charged.

Also, (I forgot to make this suggestion on my first post) measure the battery voltage before starting the engine, then measure it again after the engine has been running (about 2,000 RPM) for 30 seconds (or so). If the battery voltage remains unchanged - you have problems! If the battery voltage is 1 - 2 volts higher - give the alternator a chance to bring the battery up to voltage. If the voltage is "a little higher" (1/2 volt or so), probably would be wise to take the alternator to an Auto Parts store to be checked. This would be a good time to make sure the belt is "good and tight".

These are just my opinions,,,, seriously, I have no dog in this fight!

 

[RickB]

No one said 12.8 volts is normal!

Several people (including myself) did say that it is not uncommon for a "new" battery to be in a "not fully charged" state when you purchase it, and that it can take an hour or more (at 2,000 RPM) to bring it up to full voltage. I stand behind that assertion. Are there any deniers of that assertion?? Seriously, I would welcome a civil, respectful, discussion with people of differing views.

The only point I was trying (poorly) to make was that before spending a lot of effort, and / or money chasing gremlins that may / or may not exist, make sure the "new" battery is fully charged.

Also, (I forgot to make this suggestion on my first post) measure the battery voltage before starting the engine, then measure it again after the engine has been running (about 2,000 RPM) for 30 seconds (or so). If the battery voltage remains unchanged - you have problems! If the battery voltage is 1 - 2 volts higher - give the alternator a chance to bring the battery up to voltage. If the voltage is "a little higher" (1/2 volt or so), probably would be wise to take the alternator to an Auto Parts store to be checked. This would be a good time to make sure the belt is "good and tight".

These are just my opinions,,,, seriously, I have no dog in this fight!

Yes, I disagree. If the alternator is not supplying somewhere in the range of 13.5-14.5 volts or so as measured at the battery, the battery will never achieve a full charge, and the charging system is at fault. I am not trying to convince you of anything. But I absolutely stand by my statement. The only qualifier would be that the battery is in a condition that enables it to take a charge.

 

[Kioti Paul]

Yes, I disagree. If the alternator is not supplying somewhere in the range of 13.5-14.5 volts or so as measured at the battery, the battery will never achieve a full charge, and the charging system is at fault. I am not trying to convince you of anything. But I absolutely stand by my statement. The only qualifier would be that the battery is in a condition that enables it to take a charge.

I feel like our positions are really not in contradiction. I agree that the alternator must supply voltage in the range you say to fully charge a battery. My point (opinion, view) is that when you measure voltage at the battery, you are measuring battery voltage (not alternator output voltage).

Just as an example... if the voltage regulator is set for 14 volts, and the battery has been discharged so that the resting voltage is 11 volts (but otherwise is in good condition), immediately upon starting, the voltage at the battery will increase, but not to 14 volts, the voltage measured will depend on the size of the alternator and the battery (and any other load). As the battery charge increases, the voltage will increase, and the (charging) amperage will decrease. As a matter of practicality, you will never actually see the full 14 volts at the battery - probably 13.8 to 13.9 will be as high as you see. To actually 'see' what voltage the regulator is set at, you need specialized equipment, which in effect, 'removes the battery' from the circuit.

As the alternator for a LB1914 is listed as 14 amps, and the battery is listed as a 24F, I feel it is very plausible that (a good) 24F battery could crank the 19 HP tractor easily with as little as 9 volts (resting). Once running, it would be realistic to assume the 75+ amp/hour battery will be (initially) charged with less than 12 amps, and as the battery voltage increases towards 13+ volts, the amperage will be down to basically a trickle charge.

Anyway, (right or wrong) that is my understanding of the charging circuit. I am always eager ( and open) to hear differing views,, it's how I learn.

 

[RickB]

I feel like our positions are really not in contradiction. I agree that the alternator must supply voltage in the range you say to fully charge a battery. My point (opinion, view) is that when you measure voltage at the battery, you are measuring battery voltage (not alternator output voltage).


.

Our disagreement stems from my experience indicating that this statement is false. The only times true battery voltage is measured is when the engine is off, or when the charging system is inoperative. With a functioning charging system and engine running, the system will show charging voltage, not actual battery voltage. That is simply the way it is.
I emphasize this point only so others trying to learn are not misled by incorrect information.

 

[MinnesotaEric]

Bad alternator.

If you want, an alternator from an 87' Mazda B2000 pops right in and is a 10 amp upgrade opver stock.

https://www.oreillyauto.com/detail/...mp-alternator-remanufactured/r111480b/4546449

 

[DK35vince]

I feel like our positions are really not in contradiction. I agree that the alternator must supply voltage in the range you say to fully charge a battery. My point (opinion, view) is that when you measure voltage at the battery, you are measuring battery voltage (not alternator output voltage).

Just as an example... if the voltage regulator is set for 14 volts, and the battery has been discharged so that the resting voltage is 11 volts (but otherwise is in good condition), immediately upon starting, the voltage at the battery will increase, but not to 14 volts, the voltage measured will depend on the size of the alternator and the battery (and any other load). As the battery charge increases, the voltage will increase, and the (charging) amperage will decrease. As a matter of practicality, you will never actually see the full 14 volts at the battery - probably 13.8 to 13.9 will be as high as you see.

When running my tractor generally runs around 14.2 volts . As does my side by side, pickup truck, Etc.

 

[DieselBound]

New battery might have been compromised by a bad alternator. Don't assume that the battery is [still] good. Disconnected from tractor, charge and then check voltages AFTER the battery has allowed to rest (12 hrs is sufficient). AND, don't assume that a "new" alternator is good. ONLY way to deal with electrical issues is to TEST/MEASURE. (also, any idiot charging light might have its own issues- flaky ground or such)

 

[BleedingOrange]

Any chance your belt that turns the alternator needs to be re-tightened to spec ?

 

[casey lb1914]

My problem has been solved this is what I found was a bad battery 0 volts dead that I had jump started which I think caused the alternator to fry I bought and aftermarket alternator that lasted one week and light came back on, so I had my original alternator rebuilt but the charge light was still on so now i'm looking at my regulator so I ordered from a dealer but the dealers website was hacked, waited 3 weeks Kioti sent me the wrong regulator reordered and a week later received correct regulator and I'm happy to say after 2 1/2 months I'm back up and running, thanks to all for your suggestions.