Coach vs. Chassis batteries

[YC1]

About 97residency
City
west hollywood
State or Province
ca
Country
us
RV Manufacturer
ford
RV Model
residency
RV Length
35

Take some pictures of your battery compartment and wiring. You have a bit of an intermittent and it could be as simple as a loose cable or a bad solenoid/relay.

It is apparent the path from the batteries is not making its way to the proper place. Your engine voltage makes its way via that emergency start solenoid.

Your house batteries can pass through mechanical switches, solenoids, and lots of cables and connections.

And if you have bad batteries it can cause the same symptoms.

You need to check your batteries with a hydrometer and a load tester if possible. I found one bad one in my 6 volt bank the other day. The hydrometer said things were ok but the load tester on one of the 6 volters showed me the problem instantly.
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[YC1]

http://www.metrotrekkers.org/utility/electrical.htm

This is a fun site to experiment with and get to know a bit of how rv electrical systems work.

Do your best to find a schematic for the coach. If you can find one there are lots of folks here that can walk you right through the problem.

[twinboat]

Originally Posted by Hwy Junky

What is the Salesman Switch ??

There is none !!!!!

Look for a battery disconnect switch or use/store switch.

[Persistent]

There is a lot of good advice above. So, how to put it all together?

The easiest recommendation from above is to make sure you are operating your system correctly: Switches, circuit breakers, fuses.

Boost switch is for emergencies. As pointed out above it is probably not designed for continuous use. Leave it off for testing.

There may be several disconnect switches and devices. There may be two house battery (coach) disconnect switches. One installed by the coach manufacturer. It is frequently near the entry door and is sometimes called a "Salesmen" switch because it is often the first thing a salesmen operates when showing the new coach. The "Salesmen" switch turns off most 12 volt appliances to prevent fast battery drain while coach is not occupied. It does not disconnect safety devices and certain other devices. It often disconnects the built in battery charger. It usually must be "on" to charge and use the battery bank.

There may be a chassis disconnect switch near the entry door. This is less common. It should probably "on" for the following purposes.

The other house battery disconnect may have been installed by a previous owner. It is usually near the battery bank and it usually disconnects the battery bank entirely for long term storage (greater than a week). This switch must be on to charge and use the battery bank.

Charger circuit breaker must be “on” to charge from shore power or generator. Engine power charging frequently works regardless. Chargers in high end coaches are often an integrated system. It may include converter, inverter, charger, transfer switch, and energy management systems. Some people call this kind of charger an “inverter”. So in that case “inverter” circuit breaker may need to be “on” although the inverter itself is not necessary. The actual inverter function may have its own “on” switch. Set it to "off". It is not needed.

Make sure any high current 12 volt devices are “off”. The inverter itself should be off, or all 120 volt devices that may be powered by the inverter must be “off”.

Now that the charging system is turned “on”, let’s begin testing. You need a digital voltmeter. A suitable one costs about $15 at many hardware stores.

Measure the battery bank output voltage. You may have multiple 6 volt batteries or you may have multiple 12 volt batteries. If you read 5.0 to 7.0 volts, you probably have 6 volt batteries and you have found terminals for one 6 volt battery. Find the terminals that read more than 8 volts (hopefully above 11 volts). The 12 volt pair of termials will not be on the same battery for 6 volt battery banks. The nominal 12 volt battery bank output terminals are the pair you want.

If you have not been charging or drawing from battery bank, the battery voltage will tell you the state of charge (SOC). Below 11.2 volts is flat out discharged. 12.2 volts are about half charged. 12.7 volts or above are fully charged. If you have been charging or significantly discharging, wait a while until voltage stabilizes.

Start the generator. Measure the voltage at the battery 12 volt terminals again. The voltage should start at the previous measured voltage and slowly rise. You should notice an increase in a few minutes. After an hour it should be up substantially, maybe an increase of 1 volt or more. From below 11.2 volts it should rise to near 13 volts in 4 hours. If so, everything is working normally. It will take at least 4 hours to put in 80 – 90% of charge. It will take 14 to 18 hours fully charge and clean the sulfate off the plates. This is not a charger issue. This is the ways all lead acid batteries work. It is in the chemistry.

If the voltage follows the above charge profile, everything is charging as expected. If the voltage does not rise, the system is not charging. If it only rises a little in 4 hours, the battery bank may be defective and new batteries are required. If it does not rise at all, the EMS (energy management system) may have shut off charging do to extremely low voltage. Not all EMS’s do this.

In this case you can probably boost the voltage by running the vehicle engine and possibly pressing the “boost” switch. If so, the EMS may be the cause. An external charge is required to get voltage up above the EMS cut off voltage.

You can continue to use the engine and it may even charge without the “boost” switch. Engine charging of house batteries may not start until chassis batteries are fully charged. Or you can use an external battery charger. You can plug the external charger into any generator powered outlet.

Once battery bank voltage is high (13.0 volts) or more, discontinue charging. Wait for an hour and re-measure voltage. Voltage should have dropped after charging stops. This is the “surface charge” dissipating. The voltage should stay well above 12.0 volts. If it drops below 12 volts and/or continues rapid drop, one or more batteries are probably defective and are pulling any good batteries down.

There are a lot more possibilities. The more complex your system is, the more possibilities there are.

I wish you good luck and happy trials ahead!

[flyboy013]

As twinboat stated,

the salesman switch ... is typically a wall mounted switch that operates a solenoid to shut off the house battery.

On my coach its located just inside the entrance door. Some folks use it more often than others. My switch typically only gets turned off when the DW accidentally presses it while sitting in the passenger seat. Thus it's referred to by many as the salesman switch as thats the only time its used.

[Ray Lenning]

Are the house batteries 6 volt or 12 volt ? If they are 6 volt maybe they were wire parallel rather than series ?