24 volt engine and house: normal readings?

[Jim_Scoggins]

Need some of you smart electrical Guru's types to weigh in or refer me to some good links to send me to school.

My coach has 24 volt system for both the engine and the house batteries. Conveniently located on the dash are two combination gauges that show volts and amps for each circuit labeled: engine and house.

For a correctly functioning system:
Q1. What would be the nominal voltage engine voltage one should look for while underway? That is, being charged by the engine alternator/generator.
Q2. What would the normal voltage one should look for when the engine is off?
Q3. What would be the lowest voltage one should allow the voltage to drop to prior to charging?

Now, sorta the same questions for the house side:
Q4. Voltage while being charged?
Q5. Voltage while unplugged from shore power and not being charged?
Q6. Minimum voltage to drop to prior to charging?

One would sorta think reasonable voltages would be twice that of a 12 volt system but I am not sure. Also, one would think that the answers for questions 1,2, and 3 would be the same as questions 4, 5, and 6 but once again, I would be guessing.

Right now, I would like to know if what I am seeing is in the ball park:

Engine running:
engine and house gauges 27.5
engine off, ign on: 24.5V indicated on engine voltmeter
engine off, 26.5V indicated on the house gauge--plugged to shore power.


Once I break the code on this I will need to understand the whys and where fores of how and where 12 Volt sorces are picked from-radio, for instance.

Thanks in advance,

PS I also asked this question on another forum: rv.net

Wrong forum! Won't do that again. Some real butt holes on there besides me! But if you need a laugh or two:
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/19654608.cfm

[Joe Cannarozzi]

There is a pretty good disucussion on this topic in a previous thread.

AMG Batteries charge and discharge, check it out, but just looking at your #'s they are close to ours and if I had to guess I would say that 26.5 you get when plugged in is reflecting the charger on.

I try to not let them go below 24.5(resting) and the highest I've ever seen them go while charging is 29.5.

[garyde]

27.5 volts running is what I see on my guages while running. My Chasis batteries run at about 13.7 volts while running. POGIII Rally seminar discussed maintaining a charge of 12.5 volts on chasis maybe 12.25 but thats it. Liberty says 11.7 volts for chasis. I've never seen my House batteries lower than about 23 volts as I always keep the coach plugged in to shore or have my engine running.

[Joe Cannarozzi]

Garyde I think that the 11.7 number Liberty gave is while under load, not resting?

One of these days I,m gonna run some stuff off the batteries and get them down to about 11.9 under load, shut them down at that point and then recheck them in the morn., without a recharge, and see just where they come back to resting. I think that # is gonna be pretty close to 12.2.

[Loc]

Jim,

With engine running my chassis meter reads 27.7v without OTR air and 27.5v with OTR;

With engine off, ingnition on my chassis meter reads 24.7v

House meter reads 27.4v to 27.8v with engine running (difference depends on if the OTR air is running. I also have a switch were I can show the house side in 12 volt.

Plugged in the house meter will typically read around 13.0v to 13.2v (I usually keep the switch on the 12 volt side) if I have just shut down and I am not using a lot of 12v lighting.

Unplugged with the refrigerator running off the inverters, the house meter reads about 25.5v after 3 to 4 hours or 12.7v with the meter switch on 12 volts.

I have a vintage coach with the Driptroit 8v92 so the readings may be different for the Series 60 for which I lust.

I rarely charge the chassis batteries because we use the bus pretty regularly. I keep the battery charger on (older bus with a separate charger not built into the inverter) most of the time on the house batteries and it keeps them at about 13.3v with the switch on the 12 volt side.

[Joe Cannarozzi]

Jim there is also two great links on this subject in the-Where to find stuff, links and recources catigory.

They are listed in the thread-Tech artical on Bat. Gen. Alt. and Elec.

Enjoy

[Jim_Scoggins]

Thanks for the info and referral to other threads--search mode is now working!
At least I now know I am in the ball park.

Thanks

[Jon Wehrenberg]

Jim,

There are a few things to note that are not listed above. First, the charging voltages will vary depending on the type of batteries being used. Your inverter manuals discuss this and the dip switches on the back of the display panel should be set for the specific type of batteries and that will control the voltage so no battery damage will occur. It is typical for example for AGM batteries to have a lower charging voltage than wet cell for example.

The coach batteries are usually wet cell, and as such they may have a higher charging voltage, but since the house batteries are being charged when the engine is running the coach voltage regulator should be adjusted to reflect the charge limits for your house batteries.

Both house and coach battery voltages should be set OK unless someone has monkeyed with them. Just take the time to verify that. A meter on the fully charged batteries when the engine is running or you are on shore power will give you the verification.