The house batteries in your campervan’s house power system are separate from the Sprinter chassis starter battery. This includes Revels with RoamRig power systems. While we aren’t chassis battery specialists, we get a lot of questions about them. Here are some common questions and our answers.
Does your van start reliably? If so, then the chassis battery is probably fine. We don’t think that chassis batteries need to be replaced if there isn’t a problem. If you cannot start your van after two weeks of being parked, you should have someone investigate if the battery is bad and/or if you have any parasitic loads on the battery (Mercedes systems not shutting down, accessories installed like lights or winch, etc).
We do NOT recommend installing a trickle charger if your chassis battery is not holding a start. Always address this problem by having someone assess whether the battery is actually bad or if you have a parasitic load that’s draining the battery.
Any lead-based battery that fits your van will work. Look for a battery at a good price with a good warranty. Most car batteries are made by the same few factories and just branded differently.
If you are considering a lithium/antigravity starter battery, see the next question. There are important considerations here as it may affect your house power system.
Lithium-based batteries have a higher resting voltage compared to traditional lead-based batteries (like the stock battery in Mercedes vans). Specifically, the full resting voltage of lithium batteries may be above 13V, and they may maintain a voltage which is significantly higher than that of the stock chassis battery until they are nearly empty.
Potential Interaction with the RoamRig DC-DC converter: RoamRig uses a Kisae DMT1250 DC-DC converter to charge your house batteries from the chassis battery and chassis alternator. With the high resting voltage of a lithium chassis battery, the DC-DC converter may determine that the engine is running long after you have shut the engine off, in which case it will continue to charge the house batteries from the chassis battery. If this happens, it may completely deplete your chassis battery and your van will not start.
No Detailed Guidance Available: We strive to support all facets of your RoamRig experience in applications in which we have tested and designed the system for, which is using the stock Mercedes chassis battery. At this time, we cannot provide detailed guidance on how to use a lithium chassis battery with a RoamRig power system.
NEVER ground anything directly to the chassis battery. This can create a ground loop through the connected device when you disconnect the chassis battery via the quick connect terminal, triggering an SRS code or causing other issues.
If you power an accessory directly from the chassis battery, be aware that it can potentially drain your battery by continuing to consume power after the van has been turned off. For both power and ground, the Sprinter has multiple connections to tap, many of which are under the driver’s seat. If you’re unsure about how to connect an accessory, consult the upfitter/dealer for help.
Trickle chargers can mask problems, such as a bad battery or a chassis electrical issue that needs to be corrected. A maintainer (aka trickle charger) should not be relied upon to mask issues with the van and/or battery. This is the same as if you have a health issue. You should always try to address the cause of the health issue and not just mask the symptom with medicine.
If you use a trickle charger that has a high voltage, it might trigger the DC-DC converter into thinking that the engine is running similar to the lithium chassis battery example above.
Visit our Chassis Trickle Charger guide for more information.
While trickle chargers can be a convenient option if you won’t be using your van, we (and Mercedes) recommend powering everything off and disconnecting the chassis battery ground for storage. See our guides for storing your 1st Generation and storing your 2nd/3rd Generation RoamRig systems.
RoamRig power systems are only connected to the chassis battery via the DC-DC converter so the house batteries can charge when the van is running. If your van is not on, there is no connection between the chassis battery and the house batteries.
To isolate the RoamRig system from the chassis battery entirely, shut off the DC-DC breaker (this will also disconnect solar charging). The breaker is on the front of the bench seat for 1st generation Revels and above the batteries in the garage for 2nd and 3rd generation Revels. Doing this can be helpful if you suspect something is draining your chassis battery. By isolating the RoamRig system and monitoring your chassis battery, you can determine if there is a parasitic draw on the chassis battery from something that is not installed by RoamRig.
Some very early RoamRig systems included trickle chargers. We discontinued this addition for many reasons.
Yes. You can still use your power system as you normally would if the chassis battery is disconnected.
No, the RoamRig power systems are not configured with any connections that allow for charging or jumping the chassis battery from the house batteries.
