Chassis Battery Charging

jb1911 · 11-05-2021, 02:10 PM

Does running the generator charge the chassis battery? We have a 2017 Vegas.

Beau388 · 11-05-2021, 02:24 PM

Quote:

Originally Posted by jb1911

Does running the generator charge the chassis battery? We have a 2017 Vegas.

Yes, if the charger circuit breaker in the power center is on and the use/store switch is in use (master power-on).

DavidEM · 11-05-2021, 03:22 PM

Yes, but it will charge slowly with the POS WFCO 8955 converter/charger. I replaced mine with a Progressive Dynamics charger and it charges much faster as it is a three step charger. This is the one I used: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

David

**16ACE27** · 11-05-2021, 05:03 PM

Quote:

Originally Posted by DavidEM

Yes, but it will charge slowly with the POS WFCO 8955 converter/charger. I replaced mine with a Progressive Dynamics charger and it charges much faster as it is a three step charger. This is the one I used: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

David

So is the WFCO 8955:

Quote:

The WF-8900 Series has revolutionized RV power centers with its lighter weight, decorative doors and superior features. The WF-8955 model provides 55 Amps and a clean, constant 13.6 VDC nominal output, for reliable operation of electronics and appliances. Automatic three-stage charging extends the life of your battery with output voltage modes of 13.2 VDC range “float” mode, 13.6 VDC range “absorption” mode, and a 14.4 VDC range “bulk” charge mode. The 8900 Series also maintains peace and quiet, as the cooling fan runs only when needed.

https://wfcoelectronics.com/product/wf-8955-55-amp/

DavidEM · 11-05-2021, 06:31 PM

I guess I had a bad one on my new 2021 Axis. I never saw anything but 13.5 volts and a few amps from mine. And the partially charged current jumped 20 amps with the PD charger.

David

OldWEB · 11-05-2021, 07:46 PM

Quote:

Originally Posted by jb1911

Does running the generator charge the chassis battery? We have a 2017 Vegas.

Yes. Following from the Thor's Owners Manual (go figure)

But bear in mind YMMV as Thor (or previous owners) have done strange things.

When the motorhome engine is not running, the chassis and house battery(ies) are electrically isolated by the use of a battery isolation manager. This controller prevents house power consumption from discharging the chassis battery while the motorhome is parked.

Some additional characteristics of the battery isolation manager include:
1. The isolator electrically delays connecting the house batteries to the vehicle charging system for approximately 15 seconds, to allow the alternator time to reach full charging ability.
2. After this initial time delay, the isolator senses the voltage of the vehicle charging system. The isolator connects the house battery to the vehicle’s charging system only when the chassis charging system reaches the correct voltage.
3. If the vehicle’s charging voltage drops below 13.2 volts for a period of 4 seconds, due to low idle speed and/or excessive load, the isolator will disconnect the house batteries until the vehicle’s charging voltage returns to a level of 13.2 volts or above. For this feature, there is a built-in delay period of approximately 10 seconds.
4. The isolator allows the chassis battery to be charged by the house charging device (usually the converter or inverter) when 120 VAC is in use (shore power or generator power).
5. The isolator allows vehicle starting from the house battery(ies) via the Emergency
(Auxiliary) Start Switch.

Happy Hunting!

**16ACE27** · 11-05-2021, 08:46 PM

Quote:

Originally Posted by DavidEM

I guess I had a bad one on my new 2021 Axis. I never saw anything but 13.5 volts and a few amps from mine. And the partially charged current jumped 20 amps with the PD charger.

David

I rarely see the 14.4 VDC on ours unless I have done a deep discharge. And running a few lights will keep it at 13.6 VDC. It generally doesn't shift to 13.1 VDC until the current has been under 2 amps for 15 minutes or more, but once there, it stays in float until quite a bit of current shifts it back to absorption mode. The batteries have to be so low as to drag absorption voltage under 13.2 VDC for it to shift into bulk mode.

Pillbox · 11-05-2021, 09:59 PM

Ace,
I do not have a bim. According to thor i didn’t get one.
I have a trombetta switch, using aux start button I here it click.
What charges my chassis batts when on shore?
I see 12.6 plugged in at chassis. Never more.
Terry

**16ACE27** · 11-06-2021, 12:06 AM

Quote:

Originally Posted by Pillbox

Ace,
I do not have a bim. According to thor i didn’t get one.
I have a trombetta switch, using aux start button I here it click.
What charges my chassis batts when on shore?
I see 12.6 plugged in at chassis. Never more.
Terry

The Tombetta is the brand name of a simple continuous use rated relay that connects the house and chassis batteries together when it is told to. It can be told to do that by the Emergency Start switch (momentary connection), or by another device like a BIRD that monitors the chassis and house batteries for charging and tells the relay to connect in that situation, and disconnect when no charging is occurring to isolate the battery banks. This serves the same function as a BIM but in two discrete components.

If the chassis battery is only at 12.6 VDC when plugged into SP then the battery banks are not connected. Have someone hold the emergency start switch and measure it as well. If still just 12.6 VDC then maybe the Trombetta relay is bad. You can also unplug from SP, drain the surface charge off the house batteries (get below 13 VDC) then start the MH engine and measure the voltage at the house batteries - it should be the same as the chassis battery, likely 13.5 to 14.5 VDC. If it is still below 13 VDC then that also points to a bad relay.

Pillbox · 11-06-2021, 01:24 AM

Ace,
Thanks,
No bird no other device according to thor.
The trombetta does click and the chassis batteries go to 13.2.
So, no switch to charge on shore power?
Can I install a BIM to make it work?
Terry

**16ACE27** · 11-06-2021, 02:14 AM

Quote:

Originally Posted by Pillbox

Ace,
Thanks,
No bird no other device according to thor.
The trombetta does click and the chassis batteries go to 13.2.
So, no switch to charge on shore power?
Can I install a BIM to make it work?
Terry

Click and go to 13.2 when?
Something has to control the relay. It doesn't "click"/actuate by itself.

Yes, a BIM can be installed in place of the Trombetta relay but you may need to run some wires to it.

DavidEM · 11-06-2021, 12:01 PM

I would recommend to anyone who has a bad or questionable BIRD/Trombetta to replace both with the Precision Circuits BIM 160 if no lithium batteries or the Li-BIM 225 with lithium batteries.

As noted above this single device replaces two separate components of the BIRD/Trombetta. I have never seen reported failures of the PC BIM. It is also more sophisticated than the BIRD/Trombetta and avoids the continuous clicking you hear from the Trombetta relay in certain conditions. Also I believe all newer MHs use the PC BIM.

David

Pillbox · 11-06-2021, 06:16 PM

Ted,
When I push the assist or batt aux switch, I here the trombetta click.
I have not found any bird or bim, thors says I have neither one so I must just excite the trombetta with the aux switch to energize the battery assist. Therefore I conclude I have no chassis battery charging when on shore power unless my trombetta is a normally open /pass through device and closes upon a voltage drop.
David,
Can I just put the 225 bim in place of the trombetta? No I don’t have li batteries but I feel that would not make a difference, plus if I decide to go li I will have the proper bim in place.
Thanks for all the advice,
Terry
Ps my holiday rambler was way easier to deal with, love the old school stuff.

**16ACE27** · 11-07-2021, 04:27 AM

The BIM 160 and 225 are the same except for current capacity and both are meant for LA batteries.

For Lithium batteries you need the Li-BIM 225. It has a different connection profile than the regular BIMs.

jb1911 · 11-08-2021, 04:38 PM

People here sure get complicated. All I wanted to know is does running the generator charge the chassis battery.

**16ACE27** · 11-08-2021, 04:48 PM

Quote:

Originally Posted by jb1911

People here sure get complicated. All I wanted to know is does running the generator charge the chassis battery.

It's a complicated system and not all RVs are designed to charge the chassis battery from the HOUSE electrical system.

Short answer for your RV - Yes, it IS designed to charge the chassis battery if the generator is running.

OldWEB · 11-08-2021, 06:04 PM

Quote:

Originally Posted by jb1911

People here sure get complicated. All I wanted to know is does running the generator charge the chassis battery.

And I gave you the answer in post #6, right from a Thor Vegas owners manual. Now why would you go and read any other post then?

heh-heh.....

**16ACE27** · 11-08-2021, 10:49 PM

Quote:

Originally Posted by OldWEB

And I gave you the answer in post #6, right from a Thor Vegas owners manual. Now why would you go and read any other post then?

heh-heh.....

Actually, he had the answer in post #2.

All the rest is just free extra knowledge.

sip · 11-11-2021, 05:26 PM

My 2016 Vegas 24.1 does not charge the chassis battery when plugged in all the time. What is worse is that for some time after turning off the engine (alternator charging) they are still.combined (house and chassis) so if you test right after a trip, it does seem to charge the chassis battery but I had to live and learn with 2 dead chassis batteries that either something.is wrong in mine or Thor has made a real complicated mess here.

Long story short, I got sick of it all and out a giant hard disconnect switch on the chassis battery. I turn it off manually when not in use and use a separate charger plugged into AC to keep it maintained when the RV is parked.

sip · 11-11-2021, 05:27 PM

My 2016 Vegas 24.1 does not charge the chassis battery when plugged in all the time. What is worse is that for some time after turning off the engine (alternator charging) they are still combined (house and chassis) so if you test right after a trip, it does seem to charge the chassis battery but I had to live and learn with 2 dead chassis batteries that either something.is wrong in mine or Thor has made a real complicated mess here.

Long story short, I got sick of it all and put a giant hard disconnect switch on the chassis battery. I turn it off manually when not in use and use a separate charger plugged into AC to keep it maintained when the RV is parked.

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