Ford Truck Enthusiasts Forums - Batteries act dead, but show 12.2v, won't start?

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Quote:

Originally Posted by TC-PStroke (Post 11039712)

Thanks for the tip Les.

And charge black lead on one battery, positive lead on the other battery?

I have never charged my truck batteries that way. I charged them individually and rechecked each one. By unhooking it completely off the truck. If one is 'really' bad, I want to know about it. By charging them together, the 'weaker' of the two will pull the stronger one down to its' level. This is just the way I feel and the way I do it. I am not discouraging you from charging both at the same time and it will work the way just fine. but you will not really know the status of each battery when they are hooked up together.

:-hijacked Today while starting the volts dropped to 9.8 before it started, then after 3 mins of running the volts went to 14.1. So i'm thinking the starter is on its way out

Quote:

Originally Posted by Farmboypowerstroke (Post 11040923)

:-hijacked Today while starting the volts dropped to 9.8 before it started, then after 3 mins of running the volts went to 14.1. So i'm thinking the starter is on its way out

Alt looks good. Remember..... the large positive wire going down to the starter is always hot unless you disconnect the batts. It may just have a bolt backing out and you are not getting a good ground on the starter. After testing and you know that it has problems. Good starters are not cheap, if you can find someone, I would get it rebuilt.

Quote:

Originally Posted by SpringerPop (Post 11031861)

The confusion you experienced is common when using lead-acid "flooded" batteries.

There's more to the equation than just voltage, and that's available current.

Just as important as "charge-state" is "reserve capacity".

Reserve capacity diminishes over time, and at end-of-life, a battery may still be capable of producing its full 12.6 volts, but it's effectively the size of one of those small batteries you see as a back-up in alarm systems. At that point, it's not capable of producing the amperage necessary to start the truck.

The reduction in reserve capacity is caused by the battery's plates getting covered by sulphation. That forms on the plates anytime the battery gets below about eighty percent of fully-charged, and is only partially reversible. As a result, the battery will last the longest if you keep it as fully-charged as possible during its entire life.

But, there will always be an end-of-life. How far in the future depends on a few things, but charge-state is one of the biggies. If I were not driving mine daily, I would have a float-charger on it. Additionally, an "equalization charge" is desirable every six months or so to "top it off".

But good care only extends the time at which your batteries WILL die, and you found out when!

Then, there's only one fix, and you did it!

Pop

Just wanted to put in my experience with this issue. I was looking all over the forum for this exact issue and when I found @SpringerPop comments I decided to replace the batteries. Upon doing so, the truck started right up. Thanks for the valuable info, Pop!

Here's a chart that may help someone in the future.....for lead acid batteries
https://cimg3.ibsrv.net/gimg/www.for...f6cf50b578.jpg