Battery & electrical questions

[coolmom42]

I have a 2014 Coachmen 21QB on a Chevy 4500 chassis, with an Onan 4KW generator.

*Does the generator have its own starting battery? If so, how is this battery charged? Or does the generator crank off the chassis battery? (I'm assuming it doesn't crank off the house battery, as that would kind of defeat the point of having a generator.)

*Does the generator charge the chassis battery?

*Does the chassis alternator charge the house battery? If so, how well?

*Does the battery isolator switch completely isolate the house battery and chassis battery from each other?

*Does the converter charge the chassis battery when the RV is plugged into shore power?

*On the side of the engine compartment, there is a 200 amp fuse. What is this for?

[time2roll]

bobndot wrote:
At a dealer ? Why can't dealer answer your questions ?

Even if they do answer some questions... nothing wrong with verifying here. Dealer is not always correct or complete.

If you have an issue to address there is often a fairly simple solution to get the electrical system to operate better or to what your needs are. Check in here with these questions too.

[CharlesinGA]

Generally the MH manufacturers will not take power from the chassis/engine battery for generator starting as they do not want to risk running down the battery and leaving you stranded.

The manufacturers do however take power from the chassis/engine battery for the slide system and the retractable steps, as they do not want to risk you being stranded by not being able to retract either of these. If you have a slide, it is a very good idea to run the engine while you are operating the slide so you have higher voltage and additional amperage available to operate it. My Winnebago View recommended this in the manual.

Charles

[CharlesinGA]

Links to various models of the Trik L Start. These products allow the coach/house batteries to maintain a charge on the chassis/engine battery. It will not allow current to flow from the chassis to the coach, only from the coach to the chassis, it limits the amount of current to a max of 5 or 10 amps depending on the model, and has low voltage cutoffs that will prevent the coach batteries from getting low if they are not being recharged by the converter (via generator or shore power) or by solar.

If you have a bus or large diesel pusher type MH that has a large battery bank, then the 15 amp Amp-L-Start would be the best choice.

If you have a Class C and want a little more power output than the standard 5 amp "Ultra" Trik-L-Start, then the 10 amp "Mega" would be a good choice.

For a typical Class C the 5 amp "Ultra" version would be a good choice if you want the Chassis battery to remain topped off in storage and have shore power in storage or solar.

By using the Trik L Start, the chassis/engine battery will be fully charged while you are parked and receiving solar or shore/generator power.

None of these will overcharge the chassis/engine battery, they will only provide whatever current is needed to keep the battery topped off.

https://www.rvupgradestore.com/Ultra-Trik-L-Start-p/tls-oem.htm

10 amp Mega Trik L Start info flyer

Excellent flyer with FAQ and diagrams and such, intended for the Mega but the info is the same for a...

Home page for LSL Products which also lists the Amp-L-Start which is 15 amps.

Charles

[DrewE]

Based on my 1998 Coachmen Santara...I'm guessing your motorhome is similar.

coolmom42 wrote:
*Does the generator have its own starting battery? If so, how is this battery charged? Or does the generator crank off the chassis battery? (I'm assuming it doesn't crank off the house battery, as that would kind of defeat the point of having a generator.)

The generator starts off the house battery in my motorhome. It's not as silly as it sounds because the generator requires some 12V power while it's running, and if that's from the house system it comes from the converter rather than running down the chassis battery. The generator doesn't have any 12V charger built-in to it directly. (I think a 12V charger is an option that can be had with the Onan generator, but it's very rare in RV applications since you need the converter anyway.)

coolmom42 wrote:
*Does the generator charge the chassis battery?

No, not as from the factory; neither does the converter when plugged into shore power, since it's the same thing. A Trik-L-Start is one way to get this, or you can just connect up and plug in a small battery charger.

coolmom42 wrote:
*Does the chassis alternator charge the house battery? If so, how well?

Yes, and on mine pretty well--at least well enough to have a nicely recharged house battery after a day of driving.

coolmom42 wrote:
*Does the battery isolator switch completely isolate the house battery and chassis battery from each other?

The battery isolator is likely a solenoid, which is active whenever the engine is running or the emergency start switch is pressed. When not active, the two batteries are entirely separated and isolated. When active, they're tied together.

Do not confuse this with the house battery disconnect switch, which is a separate thing that disconnects most of the house circuits from the house battery. Exactly what is disconnected varies from RV to RV; on mine, as built by the factory, the disconnect is between the house battery and the 12V distribution panel, and the only things that are not disconnected are the generator (presumably because the current required when starting is more than is wise to put through the disconnect switch), the connection to the battery isolator, the converter, the dash radio memory line, and the power for the (manually-controlled) entry step.

coolmom42 wrote:
*Does the converter charge the chassis battery when the RV is plugged into shore power?

No

coolmom42 wrote:
*On the side of the engine compartment, there is a 200 amp fuse. What is this for?

If it's connected to the chassis battery more or less directly, it's probably to protect the wire used for charging the house battery and for the emergency start. The other end of the wire connects to the battery isolator solenoid, which in my case is next to the house battery, along with it's main fuse and a few self-resetting circuit breakers and so forth.

[houstonstroker]

Most of the Dynamax rigs on Freightliner M2 chassis, do allow for chassis batteries to be charged by the converter. It is done through a BIRD and relay. If you are plugged into shore power then coach batteries are priority until they are charged. At this point the relay will close and allow the chassis batteries to be charged. It works in reverse when the engine is running.

[enblethen]

Large fuses like the 200 amp could feed a large inverter if equipped.
Others answers sound good!

[SJ-Chris]

coolmom42 wrote:

*Does the chassis alternator charge the house battery? If so, how well?

Almost every RV is set up to allow the chassis alternator to charge the house battery. (it's a beautiful thing that comes almost for free).

I have a 2015 Thor Majestic 28a...In my experience, the chassis alternator does a great job charging the house batteries. I have a battery monitor on my house battery bank. When the house batteries are at ~50%, I have seen my chassis alternator pumping 50+ amps into my house batteries when the engine is running (even just idling).

-Chris

[bobndot]

coolmom42 wrote:

wopachop wrote:
She probably meant a 20a fuse?

The RV is at a dealer right now, or I would go check. But I am 99% sure it said 200.


I'm wondering if it has something to do with the chassis battery starting the generator.

At a dealer ? Why can't dealer answer your questions ?

[CharlesinGA]

Odds are, the connection between the chassis and coach systems is made with a electric solenoid/relay. Sometimes diodes are used but I do know Winnebago uses relays, and so do some other manufacturers. It is open, separating the systems until you start the engine, then a special key on circuit energizes the solenoid. If you have a "boost" switch that allows you to jump start the chassis engine from the house/coach batteries, you can depress it and listen for the solenoid. That is the reason for using the solenoid, it can carry the heavy starting loads that a diode would not be able to, and its probably cheaper also.

Charles

[coolmom42]

wopachop wrote:
She probably meant a 20a fuse?

The RV is at a dealer right now, or I would go check. But I am 99% sure it said 200.


I'm wondering if it has something to do with the chassis battery starting the generator.

[wopachop]

She probably meant a 20a fuse?

[pianotuna]

coolmom42 wrote:
I have a 2014 Coachmen 21QB on a Chevy 4500 chassis, with an Onan 4KW generator.

*Does the generator have its own starting battery? If so, how is this battery charged? Or does the generator crank off the chassis battery? (I'm assuming it doesn't crank off the house battery, as that would kind of defeat the point of having a generator.)

The genny rarely has its own starting battery. Stand alone generators such as the Champion 3400 do. But not the Onan.

coolmom42 wrote:
*Does the generator charge the chassis battery

Sometimes. Some designs are powered from the chassis battery for starting, others may use the house batteries. If it is does not, it is easy to add a Trik-L-Start.

coolmom42 wrote:

*Does the chassis alternator charge the house battery? If so, how well?

Yes, but not very well. A great upgrade is a dc to DC charger.

coolmom42 wrote:
*Does the battery isolator switch completely isolate the house battery and chassis battery from each other?

Usually.

coolmom42 wrote:
*Does the converter charge the chassis battery when the RV is plugged into shore power?

Not usually. There are several many solutions to this, such as the Trik-L-Start.

coolmom42 wrote:
*On the side of the engine compartment, there is a 200 amp fuse. What is this for?

Here are the three words men don't like to say.

I don't know

[MDKMDK]

Matt_Colie wrote:
Coolmom,

Mike had good answers, except for one. That one is easily checked.

I have seen very few (like 2) coaches without modification, that charged the chassis battery from shore power.

This can be added if you find you need it.

Matt

You're right. My bad, on charging chassis battery.
As I said, "if I understand your questions".
Missed one. :B

[Matt_Colie]

Coolmom,

Mike had good answers, except for one. That one is easily checked.

I have seen very few (like 2) coaches without modification, that charged the chassis battery from shore power.

This can be added if you find you need it.

Matt

[MDKMDK]

coolmom42 wrote:
I have a 2014 Coachmen 21QB on a Chevy 4500 chassis, with an Onan 4KW generator.

*Does the generator have its own starting battery? If so, how is this battery charged? Or does the generator crank off the chassis battery? (I'm assuming it doesn't crank off the house battery, as that would kind of defeat the point of having a generator.)

Most generators do use the coach batteries for their starting power, at least in my limited experience. Disable your coach batteries, and try to start the generator, as a test.

coolmom42 wrote:
*Does the generator charge the chassis battery?

No, usually.

coolmom42 wrote:
*Does the chassis alternator charge the house battery? If so, how well?

Yes, usually. Depends on the alternator amperage, ambient temperature, and size of the bettery bank to be charged. In general, I've always found it decent, if you drive enough between coach battery usage.

coolmom42 wrote:
*Does the battery isolator switch completely isolate the house battery and chassis battery from each other?

It's usually a diode (one way only) switch that allows simmultanoeus charging of all batteries, but that won't allow the coach battery system to borrow power from the chassis battery, so you (in theory) won't kill your starting battery by drawing power fromm it to run the coach 12V DC loads.

coolmom42 wrote:
*Does the converter charge the chassis battery when the RV is plugged into shore power?

Usually, yes.
EDIT: As per Matt, usually no. My bad.

coolmom42 wrote:
*On the side of the engine compartment, there is a 200 amp fuse. What is this for?

No idea. Sorry.

This is anecdotal info based on motorhomes I've owned, and my experience and understanding of their power systems, and your questions.