Auto Gen Start volt reading incorrect

[Boondocker]

2015 forza 34T AGS voltage shows lower then Magnum MR50 control panel ive also multi meter the batteries correct reading to the mr50. The onan auto gen start voltage reading on the chassis batteries is correct, house batteries incorrect 1.1 volt lower. Sent the AGS to onan for software update after I called with this problem. Came back same problem. Where is the lower reading coming from what sensor is sending the lower signal? A friend said it sounds like a diod thats bad in what and where? The pic is with the gen set running but the coach control panel shows not full, AGS shows 11.6, mr50 shows float charge @13.4. When gen is off its around 1.1 volt different house batteries. When the RV engine is running it reads a charge still not a correct voltage reading compared the the mr50 panel and voltage drops quickly when engine is shut off. At times had to run the RV eng to start the generator. Thanks

[Morich]

I'm not up on the panels at all but I sense a situation that we often get into that may be adding to your problem. One is how we look at voltage readings on batteries and get the wrong idea. When we read a voltage while the battery is connected to any form of charging and for several hours after, we do not get the true battery voltage but either the voltage from the charge system or when that stops we get a "surface charge" reading until the battery chemicals get time to full settle.
second is that there are drains on batteries that we don't always thing about, like CO detectors, radio presets and any little LED light or charger left in use. When we disconnect the house batteries,the start battery will often still have drains on it and that may explain why you see it lower???
So we really need to bear down and think heavy to get the true answer for what the batteries are doing.
Point to save grief later is to always start the engine before trying to start the genset as the engine running ties alternator, start battery, and coach batteries together. Turn off engine and the start battery does not get charged and may run down if the radio is not switched to the coach battery.
Small points can give big headaches to confuse us!

[jerichorick]

Originally Posted by Boondocker

2015 forza 34T AGS voltage shows lower then Magnum MR50 control panel ive also multi meter the batteries correct reading to the mr50. The onan auto gen start voltage reading on the chassis batteries is correct, house batteries incorrect 1.1 volt lower. Sent the AGS to onan for software update after I called with this problem. Came back same problem. Where is the lower reading coming from what sensor is sending the lower signal? A friend said it sounds like a diod thats bad in what and where? The pic is with the gen set running but the coach control panel shows not full, AGS shows 11.6, mr50 shows float charge @13.4. When gen is off its around 1.1 volt different house batteries. When the RV engine is running it reads a charge still not a correct voltage reading compared the the mr50 panel and voltage drops quickly when engine is shut off. At times had to run the RV eng to start the generator. Thanks

I am not certain you have a problem. None of my readings are the same from device to device. Wiring loss and meter tolerances will give unlike readings. If the batteries are charging correctly you don't have a "real" problem. You simple need to note the differences and live with them.

When I was new to RVing I tried to make sense of this phenomena and came to the conclusion that these instruments are built for ballpark references only. They are not procession instruments. A 10% variance is considered good.

Happy trails.
Rick Y