So I've noticed my voltage being lower than it was this time last year when I replaced both batteries and the alternator so looking to fix any issue here. Alternator is a Bosch 135a and batteries are Motomaster 850cca.

This time last year battery voltage via SCT or Forscan always hovered around 14.2 and FICM ignition and logic stayed at 14v when idling or driving and FICM MIIV was always 50 and dipped to 49.50 for a second every so often. Now battery voltage when at idle is hovering between 13.4-13.75 and when on the highway around 13.56-13.87 and FICM logic is at 13.50 more than 14.

Should also mention I have a tender hooked up and used it quite frequently over the past year. Should also point out that I'm running the smaller alternator pulley wheel FWIW.

Both batteries show 12.47v cold and I believe under 12.6v is not good? Below are some videos taken at full operating temp after a short jaunt.








Passenger side:


Drivers side:


Passenger side with positive lead on alternator:


Hot idle:


Here's some videos from a year ago when batteries and alternator were put in.


So is this the batteries getting weak or the alternator?

Thanks

 

BTW if more info/data is required please let me know and I will post it up. Also I have a spare battery that's still good and planning to do the 3rd battery mod sometime soon along with cleaning/replacing all grounds.

 

I would charge the batteries up separately with a good charger. Wait a few hours for the batteries to settle and then do a load test on each. What are your f.i.c.m. voltages while cranking?

 

Will do and will report back soon.

Thanks 👍

 

12.47-12.48v are batteries at about 80% charge. They can be there if there have been shorter run times between engine starts. It takes some time to fully recharge batteries. Or it can be there because they’ve aged more from the depth of discharge and not being fully recharged. The lead oxidizes.

14.27 Alternator
14.21 Pass
14.16 Driver

It is about the resistance at the wires and connections. Pass Batt lowers from the alternator, and Driver Batt lowers from Pass Batt. The resistance in the cables and connections is summed from the Alternator to the Pass Batt to the Driver Batt.

A little cleaning and silicone grease on the connections may improve that somewhat.

Any readings off the OBD2 are going to be up to 0.5v lower. Some read in 0.5v increments, which can confuse you and make it look lower than it is. A 13.9 actual shows 13.5.

Unless you have done reconditioning or de-sulphation on the batteries on a somewhat regular basis, they degrade in their storage capability. They still will even with the reconditioning, but not as deep. Your cold climate puts a higher demand on them and depth of discharge when starting, so degradation can be faster. All batteries have a life span, what they are made from (recycled lead), complete charging (hours), and reconditioning makes a difference.

I'd clean the connections, put a charger on each one overnight, and see how it is.

 

Here you go Sir 🙂

 

Those look good to me. Was worried they were going to be dipping into the 9’s with battery voltage that low.

 

I believe it's the AirDog unit that's sucking so much juice till glow plugs kick off and batteries are both over 14.2v so that would mean the alternator isn't as good as it was when I put it on last year correct? FICM is also solid from everything I see.

I'm thinking of upgrading to a 180a and keep the current 135a as a backup behind the rear seats and also add a third battery and beef up all the ground wires.

Thoughts?

 

Put a clamp-on ammeter set to DC current on the alternator output and see what it reads.

 

I don't know about the Airdog. I have a 180 amp and the extra ground from the drivers battery to the firewall. I do not have enough big draws for a third battery and my system is fine for me. I get a little over 3 years battery life with a good battery charge done on occasion. No battery maintainer as I drive it pretty frequently. I did freshen up all the grounds.

 

@TooManyToys.

Can I do this with my multimeter or do I need to buy a clamp on ammeter now?

Also is this with engine running or off?

 

I believe the purpose of the 3rd battery is to lessen the depth of draw on the 2 batteries thus allowing them to last longer than 2-3 years. So 3 batteries maybe 5-6 years instead of 2 batteries only lasting 2-3 years. I still have some electrical that needs to be removed and connections to clean before I go replacing the alternator, but bumping up to a 180a just seems like a good idea.

Thanks

 

Well.... guess I'll just buy a 180a alternator and see how my numbers look and go from there.

 

I don’t know what temps you’re operating in, or equipment/accessories you’re running.

I was just speaking with Ed at FICM Repair yesterday - operating in cold climates, he highly recommend a 240a alternator. His prices are reasonable and has appropriate cable kits, it would be worth a call there to see what he recommends for your set up. He will explain it all better than I.

Good luck with it.

 

Yeah might as well spend a few bucks more eh!