Another thread on here about Time for Batteries got me to thinking about mine and whether I should change them based upon time.


They have been in the truck 4 years and 6 months or so. I was reading some older threads recommending changing around the 3 year mark to prevent damage to the FICM.


I don't drive the truck everyday and sometimes it sits for 3 weeks or so. I noticed 2 days ago when I took it to work, I got one of the slowest cranks I've ever gotten. But after it's started and the glow plugs turn off, I get ~ 14.1 - 13.4 or so volts.


FICM voltage never drops below 47 and usually runs between 47.5 and 48.5 volts.


I'm not sure what size alternator is on there. Plus it's a single. I also have the upgraded cables that Mr. Jack recommended for extra battery life.


I guess it's time for batteries though?

 

If you are monitoring the voltage and it doesn't drop far while cranking and is keeping while driving I don't see why you would replace them.

 

Because of parasitic current draws, I'd use a battery tender when sitting for more than a week. JMHO.

 

I also do this when my truck is sitting.

 

I wouldn't replace them until they were load tested and proven bad. I'm in the same situation. I try and drive mine weekly, but it often sits two weeks. I have a battery tender, but just don't have it installed. I'll need to change that.

I just replaced mine (the other thread you mentioned). My FICM never dropped below 48 volts during cranking, and my voltage is 13.5 while driving, but my battery voltage dropped to 10 volts during cranking. Thus, I know i'm charging, but wasn't sure if the batteries were bad or I had a parasitic drain. Only after load testing and confirming a bad cell did I replace the batteries. I hope i don't have both.

I'd recommend checking the voltage separately after sitting a few days. It should not be less than 12. A fully charged battery will show 12.5 after a week. If they hold a charge, don't replace.

 

Thanks for the responses guys. What voltage should be a good reading when running? Is the voltage I mentioned good (down to 13.4)?


What voltage should it not go below when cranking? I need to check that. I also need to check cold resting voltage. Should I disconnect the batteries from the truck before doing so?


What parasitic current draws are there on these trucks? I wasn't aware of any.

 

Modern sealed "maintenance free" batteries are fully charged at 12.8 volts. This is due to different plate materials used in construction compared with a standard lead-acid battery, the type that have caps for the addition of water. A tenth of a volt or two doesn't sound like much, but in a battery it is important.

 

Just about any device with memory. Radio, pcm etc. plus any AM equip. added.

 

Oh thanks, I was thinking it may be something abnormal. The only thing that I know of is the interior and bed light staying on a little after the door is shut.

 

Bingo! Where I park mine I'd have to run 200' of extension cord to, so I have my slick solar panel I hang in the back at front of the bed (rear faces south) and snake the wire through the drivers door with a PWM charge controller on the seat and plug a cigar lighter adapter into the dash socket. Works like a charm

Call it a mobile battery tender

 

I guess a single battery tender will charge both batteries? Any models recommended?

 

Yes, it will. I've used Battery Tender for years both at home and on the farm. On the trailers for the small trailer braking batteries I've used small solar chargers, but those just don't seem to last very well.

 

They will maintain a charged battery (that's what they are for) or maybe top them off if slightly discharged. But they are too small and choke on deep discharges, sulfation and mismatched battery banks. A real charger is what you want, needs to be properly sized to the AH rating of the battery. Probably around 20 amps for even a "slow" charge on a large capacity bank like that. Hook up the tender once they are charged.

 

That's a good point, my interpretation was not to recharge the batteries but just to longer term maintain batteries already in full charge. It's a distinction that definitely should be made.

 

I should have used different wording. I meant maintain. As I posted at the beginning of the thread, I got a really slow crank after sitting for about 3 weeks. I just figured I would purchase a tender to maintain them when I wasn't using the truck as Mike suggested.