“RTH” - Possibly Bad Alternator

[StaticTorque]

My 80 has been sitting a couple weeks as I was waiting on some parts and my “Big Socket” for my “big nuts” for an axle job. I had to jump start it, it was showing below 2v.

The first picture is taken with the rig running at operating temperature, no load or anything. Just the driver door open and the dome light on.

The second picture is after I put a load on the car. It has the heater turned on to “Two”, radio on, headlights on, and high beams on. Door is still open as well. The first time I did this before taking a photo it was around 13.8v.

I followed ChrisFix video on how to tell which is bad, alternator or battery. I think it seems like a bad alternator, but wanted another opinion. TIA!

 

[Roostre]

It takes a long time to bring a battery that dead back up.

The voltage being over 14v makes me think your alternator is doing the best it can with such a depleted battery.

Best thing would be to put a charger on the battery and see if it recovers.

 

[efjayatee]

I've been using an Ancel BS300 (capacitor) in my 80s. It helps with starting when it has been sitting around where I cant hook up a trickle tender.
Bit pricey but its a great peace of mind when your out in middle of no where.

 

[ppc]

A battery that has dropped to 2V has been permanently destroyed. Even if it can charged it's not going to be a reliable battery. Start with a new battery then test the alternator.

 

[jonheld]

^^^^^^this.
That battery is done. Move on.
Flooded cell batteries don't recover from deep discharges.

Alternator voltage will fluctuate with the state of charge of the battery along with the load on the system.

14.4 VDC is proper charge voltage for an alternator.

 

[alia176]

As stated already, i'd pony up for a new battery, install it, then go over to one of the Vatozones to have their fancy doodad electrical system checking thing check the overall condition of your electrical system. It shows all kinds of cool stuff if the operator is savvy enough to operate it properly.

 

[Kernal]

All the above.

FWIW

@StaticTorque

What is the fluid (acid) level in the battery, all cells equal?? (if you need to add water use distilled)

Is the second photo with the accessories on, was the engine running or engine off?

What is the charge of the battery after sitting overnight ie) ~8-12 hours engine not running, charger not hooked up, everything turned off?

What is the charge (after a full charging session) after turning the headlights on for 1 minute, 3 minutes, 5 minutes? (engine off, charger not hooked up)

Will the engine crank/start after sitting overnight off a charger?

You could drive to an autoparts store (or three because at least one won't do the test right) and ask them to do a load test.

IME a very low battery that's sat a long time might be brought back to a semi-usable condition with a smart battery charger that can run repair/desulfation cycles but it will be weaker than before ie: if you're lucky maybe good for Southern Florida but not for Michigan winters in February. IME if the voltage is too low many (smart) chargers won't even start a charge cycle but you can sometimes push it by selecting the Start/Run/Boost cycle to get some voltage inside the battery then switch to charge (which might take a day or longer) then after the charger completes a charging cycle switch to Repair mode for another day or until it stops charging again.

If you don't have a good/smart battery charger that can run Repair cycles (which doesn't always save the battery IME) you then would have to weigh the cost of the charger to the cost of a new battery IMHO.

Resting voltage / Approx. State of Charge (SOC)
12.73 V 100%
12.62 V 90%
12.50 V 80%
12.37 V 70%
12.24 V 60%
12.10 V 50%
11.95 V 40%
11.80 V 30%