Question about Redarc 40A DC to DC charger wiring.

I ASSumed my 1991 C has an alternator that starts at about 14.6 and soon tapers to 13.8 like my 2003 truck has. Nope!

I was going to install a DC-DC charger to maintain the voltage at 14.6, but happened to put a voltmeter in the dash cig lighter socket for a two hour drive recently, and voltage stayed at 14.6ish the whole trip. Surprised me.

Since the alternator amps stay around 23 amps, (low amp 2G alternator) it would be a complete waste to install my 20 amp DC-DC now in the TC.

I suspect it would be the same for the OP with a higher amp alternator and his 40 amp DC-DC. Wasted effort!

Only excuse for the DC-DC would be for LFP house batts and that idea they might overload the alternator. Seems that idea is in dispute and I have no clue about that.

Well I suppose I should have just Google it first. I most certainly have a fixed voltage alternator.

t alternators vs fixed voltage alternators

 

Fixed voltage alternators are becoming less common on new vehicles as reduced fuel consumption targets and more stringent environmental and emissions standards are adopted by manufacturers. A fixed voltage alternator has a high enough voltage to charge a secondary battery in the vehicle to a usable level for leisure or auxiliary use.

The smart alternator system, also known as variable voltage alternators, allow the vehicle to control the output voltage and current from the alternator based on vehicle operating conditions. The idea behind this is to reduce electrical load and in turn mechanical load on the engine by the alternator. Unfortunately, this renders it unsuitable for charging a secondary battery system to a usable level.

 

How do I tell if I have a smart alternator?

 

Smart alternators are par for the course in most modern vehicles, but when measuring or monitoring output voltage from a vehicle with a variable voltage alternator you will find the voltage can range between 12.3V-15V. It’s not easy to tell if it’s a variable voltage alternator by only measuring voltage as sometimes the result may be deceiving or look similar to a standard alternator at time of testing. 

A good way to determine whether your vehicle has a variable voltage alternator is to look at the vehicle start battery. What you are looking for is a module mounted on or close to the battery terminal (usually the battery negative). This is the battery sensor, if it’s got one of these, you have a variable voltage alternator.

noteven wrote:
See if there is a tag or plate attached to the alternator frame somewhere. I would guess it is a Delco sumthin sumthin on your GM engine.

A good GM commercial vehicle dealership parts dept might be able to discover the original equipment alternator model from the engine number or chassis number build info.

Is there an original build line sheet deep in the file folder from Airstream?

I'll look through the paperwork. I need to know more about the two types of alrenators.

See if there is a tag or plate attached to the alternator frame somewhere. I would guess it is a Delco sumthin sumthin on your GM engine.

A good GM commercial vehicle dealership parts dept might be able to discover the original equipment alternator model from the engine number or chassis number build info.

Is there an original build line sheet deep in the file folder from Airstream?