No DC Power after shutting down Generator

[bpep]

Hello all,
2023 Momentum 25G ,No DC power inside coach, electric jack has power. It started with my 12V Refrigerator chirping from low voltage 11.2 V. I started the

generator and ran for 45 minutes after bringing the voltage up to 12.7 or so. When the generator shut down I had no DC Power in the coach. On shore power

all DC works. 2000w inverter works regardless. Batteries have been plugged in and charging 12 plus hours; they're at 13.3V (lifepo4). And still no DC power.

I started testing from the battery back. Continuity was good on both inline 30A circuit breakers(frame mounted) and all fuses. Battery disconnect is on. I

tested the battery dc in both positions. Inside: Panel:110 side no circuit breakers were not tripped, all fuses on DC side are good.



2023 Momentum (less than a month old) 2- 100ahr 12V Battleborns, 660 W Solar Panels,50A mppt solar controller, WFCO WF8955 AD Converter. All factory or dealer install.

Any advice would be greatly appreciated,
Thanks in advance.

[howson]

bpep

Since you have 12VDC plugged into shore power, the converter is operating normally. Note on the drawing below how power gets to the camper from the WFCO converter on my 315RLTS.

The obvious component based on the failure mode described is the battery disconnect, but you've checked it. (Key will NOT come out, right?)

That leaves the possibility of a faulty self-resetting circuit breaker or connection between the battery and battery disconnect. See the circled portion of the diagram below. Note it's my 315RLTS--yours may be different, but it will be somewhat similar in concept. I've circled where I'd look on my rig for the problem.

You should find these components just behind the "A" frame, street side (follow the positive battery cable). Be aware there's live 12VDC voltage if hooked to the battery, so use appropriate electrical safety practices.



Howard

[bpep]

Thank You howson. That's the same 30A self resetting circuit breaker I have. Will a continuity test not show a fault ?

[howson]

Thank You howson. That's the same 30A self resetting circuit breaker I have. Will a continuity test not show a fault ?

A continuity test may reveal the problem if the breaker itself is bad. Power must be disconnected and the breaker isolated to get a good continuity test (I assume this is understood?).

Don't discount the possibility of corrosion on the wire contacts under the nuts. A quick voltage check may show good 12V on the breaker where it's tested, but the voltage could still not be getting past corroded connections. Again, remove all sources of 12vDC power and then (one at a time!) remove the wires from the breaker and ensure they are clean.

Mike Sokol recently posted a good article on contact cleaners ( see https://rvelectricity.substack.com/p...ntact-cleaners ). I'm a fan of Deoxit--I use it on electrical connections everywhere on the camper.

Howard

[Jlawles2]

Double check for a battery disconnect (they have been known to get knocked and turned off by accident) as you mention the jacks work and they are on the battery side of the disconnect along with the gas detector. As mentioned by Howard, trace wires and test connections along the way (if you are comfortable working around powered circuits). Don't forget to gently tug on the ring terminals to ensure the crimps are GOOD. Double check all ring terminal connections by trying to gently twist the terminal in a counter clockwise direction as this may indicate a loose connection.

[bpep]

Found the culprit. It was a 20A Fuse in the inverter compartment, one of the first places we checked. We assumed it was a fuse for the inverter and moved to the underside to test all breakers ,big fuses and battery disconnect switch. Oh well live and learn. The bottom line is I need to know where my battery Amps are before I run something like a Kuerig. (I hear Kuerig is german for Rig Killer). I will follow up and try to determine exactly what caused this and report back. Victron bmv712 and Progressive Dynamics Converter will be coming soon. Thanks for all your help.

[acoleman43]

Found the culprit. It was a 20A Fuse in the inverter compartment, one of the first places we checked. We assumed it was a fuse for the inverter and moved to the underside to test all breakers ,big fuses and battery disconnect switch. Oh well live and learn. The bottom line is I need to know where my battery Amps are before I run something like a Kuerig. (I hear Kuerig is german for Rig Killer). I will follow up and try to determine exactly what caused this and report back. Victron bmv712 and Progressive Dynamics Converter will be coming soon. Thanks for all your help.

20a fuse in the inverter compartment?? What was that fuse for? Strange place to put something like that.

[bpep]

Power From Battery to DC Panel

[acoleman43]

Power From Battery to DC Panel

Wow, just a 20a fuse? Should be more like 80a fuse. That fuse will blow a lot if it's just 20a.

[howson]

Power From Battery to DC Panel

I agree with acoleman43 -- something's not adding up at this point. The only device between your battery and the input of the Power Distribution Panel (on the DC side) should be a self-resetting circuit breaker as shown in the diagram from post 2...but obviously something else is going on.

What I'm wondering is if the 20A fuse is part of the Momentum's Energy Management System (EMS). Your coach is a 30A unit, right?

Is it possible to trace the wire? If you pull the fuse can you duplicate the initial problem of the battery not charging? What I'm guessing is that the EMS goes into a default mode (limited power) with the loss of 12VDC control power (the fuse blown or pulled). That could explain why the converter wasn't getting 120VAC and thus no battery charge.

Doesn't explain the lack of solar charging, though--I think that's a totally separate problem.

[bpep]

Wow, just a 20a fuse? Should be more like 80a fuse. That fuse will blow a lot if it's just 20a.

I agree, I just wonder if the wiring could handle that many Amps.

[bpep]

Yes, 30A service. I'm not familiar with Momentum's Emergency Management System.

WFCO Inverter is wired directly to the battery and it has its own battery disconnect switch. This explains why the inverter was still powered when there was

no DC power. With the main battery disconnect switch off the Inverter still has power.

Is this normal ?

[acoleman43]

Yes, 30A service. I'm not familiar with Momentum's Emergency Management System.

WFCO Inverter is wired directly to the battery and it has its own battery disconnect switch. This explains why the inverter was still powered when there was

no DC power. With the main battery disconnect switch off the Inverter still has power.

Is this normal ?

Yes this is normal because the inverter is normally connected directly (well, through an inverter disconnect switch) to the battery terminals (bypassing the main distribution panel disconnect).

If the inverter disconnect is off and the inverter still has power....that would be a problem.

I'm not familiar at all with the Momentum's new energy management system. Makes me very curious how it all works.

[howson]

I'm not familiar with Momentum's Emergency Management System.

Energy Management System which Grand Design calls a "Mini-EMS" or "Mini-Energy Management System" in the manual. Electronic version available here: https://www.granddesignrv.com/owners...3ab68e7b6a-tab

Very good explanation of how it works starting on page 92.

Howard

[bpep]

I talked with a tech at WFCO regarding this issue. He is 99% sure that the 20A inline fuse is to small. He recommends installing and testing a 50A in its place. The 8 awg wire is rated for 60A and goes from the battery to the Power Dist. Panel/55A converter. Can anybody with a 2022 Grand Design Momentum G classc or older check and confirm there DC fuse size and report back please ? Thanks