Originally Posted by bakerbuilttracks

Hey guys,
Last week my truck started to get kinda hard to start. Then one morning it was completely dead and did not even fire off.

I cleaned the terminals and tried again and still no result. So i checked the Batt Volts and both had about 12.5

Got out my load tester and the passenger side failed, Picked up a new motor craft battery from orilleys and all is good again.

The batteries i had or still have one in there were interstate 850cca 1000ca they are from Feb of 2014

Im Just curious if a week alternator could have been the culprit. Seems as I'm replacing my batteries every 2 to 3 years. Now i know how that goes but curious after watching my volt readings on my edge evolution monitor which is plugged into the obdll port. Just wondering if these are normal.

On start up i see 11.4v
after running for 5 min or so it creeps up to 12 or 12.5 and stays there for 10 min or so

Once i start driving it get up to 13 to 13.4

After driving for 30 or 35min to drop my son off hen i park or stop at a red light it drops to 12.4 12.6 volts.

So i started fooling around with a few things and heres what else i noticed

Driving @ 1500rpm with no ac and no lights i see 13.7 to 13.9
at idle no ac no lights 12.7

Driving with lights on and ac full blast 13.2 to 13.5
at idle with lights on and ac 12.2 to 12.4

This just dose not seem right. The alternator is pretty old but i don't want to replace it if its not broke kinda thing

So what do y'all think

Originally Posted by bakerbuilttracks

Agreed but my question was about the charging system not how to replace batteries. I normally do it that way and have my entire life. But the 900cca tractor battery plus my 2 woulda put me up to 400 bucks and i was not in a position to drop that kinda coin. Years past always bought 2 at the same time even try and get the same month if i can. Just like chain and sprockets on a motorcycle they wear together i get that. But the funds went there to spend

Originally Posted by Tedster9

It isn't "necessary" to do a whole bunch of things, but it's best practices and will save money in the long run. Ya do what ya gotta do, but people should be informed about what's likely to occur.

Originally Posted by Tedster9

Originally Posted by pirschwagon

What is likely to occur? I see this as mixing Apples and Oranges referring to the OP. Or, Battery replacement as a whole. The statement seems to indicates to me the other battery (referring to both batteries) being deficient rather than just one. There is no economic reason to replace a Battery that passes testing unless it is just over the acceptable limits of testing. And then, its always the customers choice when informed. By this standard, every time I replaced a Battery in early Cummins V8 the customer would have spent over $2,000 + Labor for two banks of parallel 6v batteries in a series configuration on a 12v System. I would have been asked to leave. Or, for that matter $400 + Labor on every Powerstroke I worked on. That's not accurate. Parallel Batteries achieve the same Volts while doubling the Ampere Hours (ah). For instance, our Trucks only require 12v and no more than 740 amps to start. But, the specification is for 2 (two) 800+ ah Batteries. By doing this, when the batteries fall below 50% amperage while cranking, the reserve 50% of each produce 800 ah (amps) (720 + 10% additional reserve). Series Battery configurations double the Voltage and maintain the same single rated ah capacity. This is seen on many OTRT from before the 50's thru the 80's. And, still used in several heavy-duty applications such as Back-Up Generators, Golf Carts, Hybrid, etc.. Reversing Polarity of a FLA / SLA Battery is a general myth. The only way for this to happen would be to completely discharge the battery, either by leaving the key on, or by an unnoticed dead short that completely dissipated the charge over a few days. After that happened it would appear to be a dead battery, nothing more. Cells is FLA / SLA Batteries must be within .50sg or 0.05v. during the testing process to pass. Any more and they would fail. Therefore, replacing the battery is a waste of dollar$. The regulator on our trucks (differ than todays PCM/ECM controlled units) is either open or closed, charging or not when operating properly. All FLA / SLA Batteries "Off-Gas", all the time, when being charged. But, more noticeable when voltage is in excess of 15v. Its a by-product of the cells chemical reaction when the ion process is occurring with two dissimilar metals. This is how Sulfation (the by-product) occurs which eventually leads to an exhausted battery life because the plate area is covered and electrolysis no longer occurs. The best way to prevent this is by for the average owner is to ensure the batteries have the correct level of denatured water and not lower than 55/45 Acid to Water Ratio. * On a side not, charging a battery intermittently at 16v helps reduce the process when done correctly over several hours. Many Battery Maintainers offer this function over the counter. Many, if not most of the OTRT and Hybrid Vehicles have them installed at the factory as a combination maintainer / conditioner to get maximum life. The problem with Alternators failing can be in correlation to batteries. Most fail because of cheap Rectifiers. Or, Rectifiers which aren't sufficient for the amperage they're outputting. Any Alternator above 120 amps will last twice as long, if not indefinitely, with one, or preferably two or more external rectifier in the system all dependent upon the ah the system requires. With the only special tool being a Paper Clip, and a Soldering Iron, they're rebuilt rater easily for about $20.