Charging rates

[Scuba Steve]

How 'bout this:
Different manufacturers use different systems, and trying to diagnose and repair said systems require a decent overview of function.
If you can't look over the spaghetti wiring like in the above pictures, identify the components and function of those components and troubleshoot what you're looking at... you're gonna have a bad time
IE: Steve: I'm pretty sure the black box with multiple wires in the foreground of the last pic is a charge controller, that will isolate the cabin batteries if the voltage drops... it might not be, but it sure looks like how I wire charge controllers. You want an "auto" isolator so the cabin batteries don't flatten your underhood battery... so the truck starts after a hard night of partying with the stereo on full blast and the beer fridge being opened every 35 seconds and you were too drunk to start the genny and you wake up, in a stupor, to 5 dead batteries... been there done that, fixed the isolators

No issues the batteries are disconnected from each other when the van isn't running. If you ram down the van battery there is a manual momentary switch to energize the solenoid and give a boost from the house batteries
No isolation one relay for charging and one to disconnect the house batteries for storage. To be clear when the engine is not running there is no connection between house and chassis battery. The relay is open and no discharging of the chassis is possible. The one in the foreground is the house battery disconnect for storage. It is a latching relay


Sent from the future

 

[timtune]

You said in your original post that you were considering running new wires to the cabin batteries... without knowing what's wrong... that's a bad omen

I see how that could have spooked you. What I meant was, laying under the van with a multimeter while the Squeeze randomly revs it was not the best. I was thinking gater clips and really long leads would let ME drive and see the meter.

 

[timtune]

The Squeeze is on a FB page for Vintage RTs. Like here, if you hang around a bit you learn there are folks who KNOW stuff . One has built a RT electrical simulator. Basically a animated wiring diagram where you can plug in make/year and then operate various options - 12v , shore power. I'll try and link to it as aid to this thread.
Thanks for the help so far.

 

[bitzz]

You don't have to"rev it up". That alternator is regulated out of the engine ECU, it should charge at idle.
One of the first things I would look at is the alt brushes, 25 years is enough for a set of brushes and a bad negative brush will lower the charge rate like you got and running it at low voltage wears/burns the neg brush AND they're cheap AND they're easy to fix. I don't remember if you have to remove the alternator... if you can remove the back cover of the alternator in situ, you can probably replace the brushes in situ... follow the two small leads on the back of the alternator to the brushes. Any auto electric shop will have brushes.
While you're in there, with the brushes disconnected, one of those small brush leads goes directly to negative, so will have ZERO potential to negative with the key off and the other should show between 1 to 5 volt potential to negative, with the key ON... 5v with the engine running... give it a minute if it's zero or 1 volt, some of the ECUs will turn off the alt when it first starts, and will give it minute to settle before it tries to charge... I don't know what ECU you have. If you have 5v on the POS brush with the engine running, the regulator works.
It's a Denso alternator with no regulator, it will last forever if you keep brushes in it and don't throw a stupid load at it... but if the regulator goes, you're replacing the computer

 

[timtune]

You don't have to"rev it up". That alternator is regulated out of the engine ECU, it should charge at idle.
One of the first things I would look at is the alt brushes, 25 years is enough for a set of brushes and a bad negative brush will lower the charge rate like you got and running it at low voltage wears/burns the neg brush AND they're cheap AND they're easy to fix. I don't remember if you have to remove the alternator... if you can remove the back cover of the alternator in situ, you can probably replace the brushes in situ... follow the two small leads on the back of the alternator to the brushes. Any auto electric shop will have brushes.
While you're in there, with the brushes disconnected, one of those small brush leads goes directly to negative, so will have ZERO potential to negative with the key off and the other should show between 1 to 5 volt potential to negative, with the key ON... 5v with the engine running... give it a minute if it's zero or 1 volt, some of the ECUs will turn off the alt when it first starts, and will give it minute to settle before it tries to charge... I don't know what ECU you have. If you have 5v on the POS brush with the engine running, the regulator works.
It's a Denso alternator with no regulator, it will last forever if you keep brushes in it and don't throw a stupid load at it... but if the regulator goes, you're replacing the computer

I have yet to check the voltage of the "truck" battery. If it's as low as the house voltage than yes I would agree the alternator needs work.

RT folks on FB have found that the fuses have been known to corrode on the inverter(??) causing weak charge. I've got some checking to do.

 

[timtune]

Just checked 12.5 at rest and 13.9 at idle. Is that a good reading? Certainly much better than the 13.1 at the house batteries.

 

[GreyGhost]

Just checked 12.5 at rest and 13.9 at idle. Is that a good reading? Certainly much better than the 13.1 at the house batteries.

Bitzz knows better than me but I would be happy enough with those readings. 12.5 is a little low but if we start talking about tenths of a volt, the accuracy of the measurement instrument comes into play.

 

[bitzz]

12.5v at rest is about 85-90% charged, you want minimum 12.7v.
How old are the batteries? Are they deep cycle? Can you charge them (at least the underhood) with a charger and get more than 12.7? What is voltage of the underhood battery while the starter is turning? (You want more than 10v across the battery while you load test it... with the starter)
13.9v at idle works... does it increase at 2000rpm? How much?

... and " at rest" means it has rested for an hour, NOT just shut off the truck. Does the voltage drop after resting for an hour or longer?

 

[timtune]

Yes deep cycle, not very old. Found and checked isolator. 14.7 at the alternator and 13.9 going to each truck and house batteries (house is 2 in parallel)
Cleaning the isolator connections got me to 13.2 at the batteries in the back. Turning off the cabin AC made it 13.3.

I can't explain the drop between the isolater and the reading in the back at the batteries. RT people speak of two "auto reset circuit breakers" in that line that get dirty/fail but I can't find them on the outside/underneath where they say I should so the bed 's coming apart.

 

[Scuba Steve]

Yes deep cycle, not very old. Found and checked isolator. 14.7 at the alternator and 13.9 going to each truck and house batteries (house is 2 in parallel)
Cleaning the isolator connections got me to 13.2 at the batteries in the back. Turning off the cabin AC made it 13.3.

I can't explain the drop between the isolater and the reading in the back at the batteries. RT people speak of two "auto reset circuit breakers" in that line that get dirty/fail but I can't find them on the outside/underneath where they say I should so the bed 's coming apart.

Isolator makes approximately .7 volt drop on its own so your numbers seem close I assume this is the reason isolators aren't used on newer units. What is the voltage at each battery when running and at rest.

Sent from the future

 

[ToSlow]

I would think most new units run canbus, not sure if that’s the reason they don’t run isolators

 

[timtune]

Isolator makes approximately .7 volt drop on its own so your numbers seem close I assume this is the reason isolators aren't used on newer units. What is the voltage at each battery when running and at rest.

Sent from the future

Running at the isolator (mounted on the firewall) I get 14.7 from the altenator lead. About 13.9 on each of the leads heading to the truck and house batteries.
For some reason the 13.9 to the house battery at the isolator turns into 13.2 in the back of the truck at the batteries.

The RT people say there should be 2 auto reset circuit breakers in that line that can corrode and reduce the power. I have yet to find them. Time to pull the bed apart - I think they're underneath.

 

[timtune]

Looks like I'm loosing about .5v as the power passes thru one of these circuit breakers. Is that a sign it needs replacing? The local crap tire doesn't have one in stock or I would have swapped it by now

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[GreyGhost]

Looks like I'm loosing about .5v as the power passes thru one of these circuit breakers. Is that a sign it needs replacing? The local crap tire doesn't have one in stock or I would have swapped it by now

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I haven't measured one to know if that's reasonable. Being somewhat of an idiot, if I didn't have a trip in the very near future, I would probably force it to blow/reset and see if the drop changes (and that also proves that it hasn't failed closed).

 

[Scuba Steve]

Looks like I'm loosing about .5v as the power passes thru one of these circuit breakers. Is that a sign it needs replacing? The local crap tire doesn't have one in stock or I would have swapped it by now

General PDP Template

www.canadiantire.ca

I don't think you should have a drop on that I would be tempted to replace with a fuse to eliminate the problem forever.

Sent from the future

 

[timtune]

I'll just replace it with same. For a fuse the location sucks.

 

[timtune]

Yup. New CB and I'm getting 13.6 at the house battery which is a nice improvement. Should a .3v drop in a length of wire from the isolator on the firewall and the house battery in back (19ft) be concernig? I'm told there's another CB somewhere but I can't find it.

Finally, this whole exercise was made quite easy with very simple tests from a multimeter. If it's not in your toolbox now get one.

 

[GreyGhost]

Yup. New CB and I'm getting 13.6 at the house battery which is a nice improvement. Should a .3v drop in a length of wire from the isolator on the firewall and the house battery in back (19ft) be concernig? I'm told there's another CB somewhere but I can't find it.

Finally, this whole exercise was made quite easy with very simple tests from a multimeter. If it's not in your toolbox now get one.

How many amps are flowing to get a 0.3V voltage drop? If that was at 0.1A, it would be concerning. If it was as 20A, I wouldn't say that is concerning. If you don't have an easy way to measure DC amps, charge the house batteries fully with the charger and then check voltage with engine running. They should be absorbing almost nothing at that point.

 

[timtune]

How many amps are flowing to get a 0.3V voltage drop? If that was at 0.1A, it would be concerning. If it was as 20A, I wouldn't say that is concerning. If you don't have an easy way to measure DC amps, charge the house batteries fully with the charger and then check voltage with engine running. They should be absorbing almost nothing at that point.

I don't think anything. The above readings were just with the truck idling and the house batteries turned off.