***** Hi SternWake. My reply is interspaced below.
So let me see if I have this right.
You have two 1 gauge welding wires from engine battery posts to house battery posts with a connector in between?
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**** Yes, 2 wires from house batts to the cab of truck and to truck battery with a welding cable connector in between as I don't use it much. Not my first choice of a way to do it but I made it with stuff I already had laying around. I took another look and noticed that the ground wire goes to metal on the body near the truck battery and not right to the neg. terminal on the truck battery. I could actually take that one out and ground it to the frame near the house batts. to shorten that run and tidy it up a bit.
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Or do you have one single wire from engine battery to house battery with a connector in between? This would require the house batteries grounded to frame.
First of all, it is better( for high amp delivery) to put big cables right to the alternator (+) stud and (-) stud or mounting bolt rather than take power from engine battery.
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******I can try that but it was working really well a while back, so I'm guessing that's not the issue
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This is beneficial as it bypasses the OEM alternator to engine battery wiring, which is just barely big enough in the first place. Secondly it will likely allow the vehicles voltage regulator to hold higher voltages for longer. Most like to revert back to 13.7ish range for fear of overcharging. they were not designed with a bank of thirsty batteries in mind tacked onto the engine battery through a longer circuit
Your 14.2v reading is likely only one data point. Actually driving at different speeds and engine alternator and perhaps battery temperature will have the voltage vary, and many systems when the alternator gets hot will reduce voltage.
If you are using the frame as a ground, then this ground cable needs to be thick and the connections pristinely clean and tight. Frame grounds passing alternator charging current are problematic. Fine at first, developing high resistance quickly as the mating surfaces oxidize and corrode due to the dissimilar metal tango.
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****I looked at my ground connections and they look ok, but what you wrote about that makes a lot of sense now that I really think about it. I soldered those fitting on and I know that's not the best but I don't have the proper tool to crimp them. I'm thinking maybe I'll start again on this by redoing the grounding side by cutting that long run back to the truck batt and buying a hammer on type of fitting for the end of that (now shorter) cable and cleaning off a spot on the frame right under the truck box to ground it to. Does that make sense?
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Generally disconnecting the house batteries while hey are accepting a large current, is not good for the Diodes, but as long as the engine battery is still accepting something it is not a total load dump situation.
but a dying engine battery or one that is fully charged is not accepting much current. The damage could be cumulative to the diodes with many separation during high loads where the alternator goes from making 2/3 of its rating to 1/8th instantly.
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**** Yes, I can understand that. After the problem started something in the back of my mind was bugging me about pulling that connector apart while the truck was running. And about plugging it in when the truck was running. So I looked it up on the internet and sure enough it seems to be dangerous to the alt. so I stopped. I must have read that some place a while back, but forgot.
The truck batt accepts charge but my son in law boiled it down below the top of the led at one point when he had my truck. When I got it back and started checking it over I noticed and put some distilled water in there. It seems to hold enough of a charge to still start the truck but it drops down to 11.5 after sitting for a while. So that's why I started disconnecting it from the house batts just before I shut down the engine as I didn't want the truck battery to pull from the house batts once it sat for a bit. Once it stops starting the truck I'll replace it.
I was going to put proper switch in but haven't gotten around to that yet. Anyway, I was thinking the alt is probably ok because it charges up the truck battery and that is obviously weak. The other thought I had was maybe the truck batt being weak now was all that the alt counld handle. Now that you wrote about those wires going to from alt to batt under the hood being just enough, you've got me thinking maybe that theory is right.
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Electrical connections are always the issue, it seems. Check connectors and ring terminals and get some Caig Deoxit d5 spray, sold at Frys electronics or amazon.
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***** This makes a lot of sense. Thanks. Since the alt is working properly it seems, it has to be the wiring.
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It is good to have a frame to alternator ground when using the frame as a house battery ground.
If you think the alternator might have blown a diode during your partial load dumps, put your digital multimeter on AC voltage and check for significant AC electricity on the battery terminals or back of alternator with engine running.
if so replace alternator. I am not sure what number represents 'significant'. will look into it
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****** I've never heard of this. So put meter on AC and touch the Pos and Neg on the truck battery. If it shows any AC then the alt is probably damaged? I should check that first, I think. thanks for your help with this.
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