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Stoped · 04-21-2025, 06:45 AM

I found my Interstate with a dead chassis battery after two months in mothballs. Managed to get it jump started, but decided to replace the chassis battery with a new OEM. Chassis is making 14.5 volts with engine running.

As expected, the house batteries (2 X 100 amp lithium) where drained during storage with no chassis power. I did expect it to begin to charge after replacing the chassis battery, and after 12 hours connected to shore power (15A), but the only indication that the house system is getting power is an error message on the inverter screen - 'No Inverter Comm' DC 0.0V 0A.

Does anyone have any insights as to what my next steps might be?

SunchaserV · 04-21-2025, 07:43 AM

Questions
- Is it an inverter charger combo?
- If not, what charger?
- Was all the power off, inverter and master switch off to isolate batteries
during layup?
-What brand of LFPs?
-Is this a new to you rig?

I've had several Magnum inverter/charger combos and found them, like all inverter/charger combos, to be a battery drain as the original setups assumed a shore power on situation. One nicety was an inverter bypass which allowed easy trouble shooting.

vanderwielen · 04-21-2025, 08:08 AM

Check the breaker on the top of the Magnum under the jump seat. If that is not the issue...

Drop shore power and measure the voltage of the lithiums. Odds are they are 'asleep', which the way the BMS protects the cells from a complete discharge. If 0 volts are present, place a 12V power source across them momentarily to wake them up. Then reconnect AC and see if charging begins. (use a simple battery old school battery charger to wake up them up).

JimMartin · 04-21-2025, 08:12 AM

Based on the error, I'd start by checking to see if the breaker tripped on your inverter (our Magnum inverter has a reset button that is accessible via a panel under the passenger seat.

Edit: vanderwielen and I were posting at the same time

. Hope it's just the breaker!

PaulBristol · 04-21-2025, 08:45 AM

The Magnum requires 12 volts to operate. Voltage on the Magnum 12 volt connectors must be brought up to the "restart" voltage to restart the Magnum.

See instructions for the Magnum. Note: The Magnum model number is on the inverter/charger unit it self. The remote shown has its own model number.

Start the RV engine. Run it for a while. Leave the RV engine running and try to restart the Magnum. Look on the unit itself. The remote connecting wire may be disconnected. Hopefully the alternator will bring the voltage up and the Magnum will restart.

Lithium batteries will usually restart the same way.

If the alternator will not charge the house batteries, you can use jumper cables to any 12 volt automotive battery or a portable battery charger to get the voltage up.

The Magnum probably has circuit breakers on the unit itself and a high capacity circuit breaker or fuse in the inverter 12 volt cables. There is also a 120 volt circuit breaker feeding the Magnum from the main RV house circuit breaker panel.

uncle_bob · 04-21-2025, 10:54 AM

Hi

You *may* want to dig a bit deeper.

The Wonderfull folks at MB sometimes have *two* chassis batteries. I spent a fine morning last week listening to the service folks explain this to multiple customers. If by some odd chance your van got done up that way (I have no idea if any ever did), it would be worth sorting out where that battery is and replacing it.

Again, I only know that MB does this on some vehicles. It may never ever have been done on a Sprinter.

Bob

Boxster1971 · 04-21-2025, 05:12 PM

Quote:

Originally Posted by uncle_bob

Hi

You *may* want to dig a bit deeper.

The Wonderfull folks at MB sometimes have *two* chassis batteries. I spent a fine morning last week listening to the service folks explain this to multiple customers. If by some odd chance your van got done up that way (I have no idea if any ever did), it would be worth sorting out where that battery is and replacing it.

Again, I only know that MB does this on some vehicles. It may never ever have been done on a Sprinter.

Bob

Yes - the Sprinter does have a second “Auxiliary” battery option and Airstream built many Interstates with the second chassis battery. The main one is under the driver seat floor and th Escondido is typically in the driver side of engine compartment.