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Chassis Battery FAQ

The house batteries in your RoamRig system are separate from the Sprinter chassis starter battery. While we aren’t chassis battery specialists, we get a lot of questions about them. Here are some common questions and our answers.


When is it time to replace my chassis battery?

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). 

It’s time to replace the chassis battery. What do you recommend? Will it work with my RoamRig power system?

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. Personally, we're fans of WalMart batteries. They are easy to come by, priced well, have a great warranty and are as good as what you'll find in big auto stores. 

If you are considering a lithium starter battery, please read our blog post first. The higher resting voltage of a lithium starter battery may trick the DC-to-DC converter into thinking the engine is on, causing it to continue charging the house batteries from the chassis battery long after the van is turned off. If this happens, it may completely deplete the chassis battery. 

Can I connect an accessory directly to the chassis battery?

First, do not 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. Watch our video for a detailed explanation.

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.

Should I use a trickle charger?

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. Note: 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. 

Storing Your Van

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. Also, see our guides for storing your 1st Generation and 2nd-3rd Generation RoamRig systems.

RoamRig’s Connection to the Chassis Battery

Your RoamRig power system is 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. 

Can I use my RoamRig system when the chassis battery is disconnected?
Yes. You can still use your power system as you normally would if the chassis battery is disconnected. 

Can I charge my chassis battery from the lithium house batteries in my RoamRig system?
No, the RoamRig power systems are not configured with any connections that allow for charging or jumping the chassis battery from the house batteries.