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Discussion Starter #21
I keep getting different readings, because I keep hooking up my trickle charger to keep the batteries fully charged after I start the truck and it drains them.
 

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He'll get a high reading just as the charger comes off.

When you say gauge voltage vs voltmeter, what gauge are you talking about?

Some of the inconsistencies you are giving can be a cable issue, again I need to see what the cables on the terminals look like.
 

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Oh, and I'd like to see the battery voltage readings with the negative cable terminal off both batteries.
 

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After the batteries are fully charged with your charger
check each battery
what is the voltage at the battery posts when you first turn the key on?
what is the voltage when cranking? -- leave the key off and use the starter jumper wire on the passenger fender

next testing voltage drop on the cables with a load would be good
 

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Discussion Starter #25
So I've been using a multimeter to take readings, plus going off what my Edge says that is plugged into the OBD.
767902
767903
 

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Discussion Starter #26
Picture with negative cables removed. I left the charger on last night then turned it off this morning. So the truck has been sitting all day, if that matters.
767904
767905
 

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Have you load tested them individually?
 

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Mark's question is the one not asked yet. Since the two still are showing the float charge value after a day of disconnect they don't indicate a bad cell. Mark is looking for a lowered capacity, and it's still a valid question. The one repair connection on the positive driver's battery could use some maintenance. They are not the best as a repair, but I've bought farm equipment that has them and they have been OK.

I was hoping to see the battery to battery positive connection on the passenger side as sometimes those get separated and what you are reporting has had that as the cause. The alternator charges the pass batt, and the driver's battery pulls down with lowering voltage working the electronics but never recharges. You could check if the battery to battery connection is good after 5 minutes of running by connecting your negative lead to a motor ground, then check each positive battery terminal. Things can also get really weird if one of the negative cables for the batteries is hurt.
 

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Discussion Starter #29
I had pulled out both batteries and had them tested at Autozone. They said they passed.

I turned on the truck and let the glow plugs warm up, volts were at 13.04 on the driver's side. Then I started it volts went down to 12.25 and stayed there. I checked the passenger side and it's 14.36. I am guessing the alternator is working on that side.
 

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The glow plugs pull current from the passenger positive terminal through this cable.

20200619_180526.jpg

With the cable that goes between the batteries, both batts should be drawn from and voltage equal. As I mentioned earlier if volts keep dropping when running and the alternator is working (as you note with 14.36 pass side), The cable between the batteries is at fault. You keep driving, the driver's battery depletes, but the passenger battery gets charged, but it's isolated from the rest of the vehicle.

Again, with the truck running, the check is negative lead at the passenger negative terminal, positive lead to the pass batt positive should be 14+, but the positive lead to the driver batt would diminish. But if the cable was good, both batteries would be equal.
 

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Here's a problem child.

767908


But the issue can be within the cable, or at the drivers terminal with that clamp-on terminal.
 

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The positive side cables are shot, looking at those pictures
replace them -- the factory ones are expensive

Most big truck stores, farm stores, and some auto parts stores can make up cables with ring terminals on each end
then use the battery clamp to stud post type ends on the battery to finish the job
 

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Those battery cables seem awful small to me, the clamps look like **** too.
You can build your own cables. I used welding cable to build mine. I used 2/0 for positive, 1/0 for grounds, added a ground from drivers battery to the block and a cable from the alternator to the driver's battery. Seems like over kill, but man, what a difference starting the truck.
Due to the cost, I started with the grounds, then did the positive cables next. Since your cables seem to small and you're having battery issues, you should replace the positive side, then grounds. ***If you use welding cable, you'll need to shrink wrap the cable with marine grade shrink wrap since welding cable doesn't like grease, oil or fuel. Also, load test the batteries while hooked up and see what happens.
 

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Discussion Starter #34
Thank you guys. You were right the cable that connects the batteries was bad. I ended up taking off the positive on the driver's side and it was corroded solid. I soaked it in some baking soda, water, and coke for about 15 minutes and let all the corrosion bubble off. Then I scrubbed it with a brush, put it back together, and I got 14.46 on the passenger side and 14.42 on the driver's side, when the alternator kicked on 🙌
767915
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So that tells me the wiring is good. Keep in mind, a multimeter and resistance drops are not the best way to test these wires, but the best way I can. You could have some fraying in the cables somewhere that is not effecting the multimeter, but would a page current. I don’t mean to send you down a rabbit hole with this checking grounds.

I really don’t understand why you’re getting all these different readings on the batteries with them off. 12.4 to 12.9 is a big difference. My guess is still a battery alternator combo.
He'll get a high reading just as the charger comes off.

When you say gauge voltage vs voltmeter, what gauge are you talking about?

Some of the inconsistencies you are giving can be a cable issue, again I need to see what the cables on the terminals look like.
Well said Chris and Jack! Took awhile but the issue was identified.
 

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Thanks Mark. Twice this was the case over at FTE, and why I asked to take pictures. Those were confusing at first too.

Good job All2. Next time try vinegar with a baking soda neutralizing rinse. No matter, you got it cleaned. I dislike those clamps due to they always seem to develop corrosion, but also the clamping pressure can never achieve ideal. Even with the crimped fittings, anytime you see green or white, it’s game over.

You still were reading a 0.04v difference and I’ll assume that was with just running loads. You should check that under load, with everything in the cab turned on. That’s when resistance will show a drop.
 
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