Lithium house battery in a Mercedes Sprinter

Mercedes-Benz and Sprinter are trademarks of their owner. Amp Hour Supply isn’t affiliated with Mercedes-Benz.

Short answer: Mercedes settles this one for you. Its Sprinter body builder guide says any added battery of a different technology must sit behind a DC/DC converter or charger, wired after the E36 cutoff relay, with charging current limited to 80 A at most. A 30 A DC-DC charger fits well inside that.

The Sprinter’s numbers

All from Mercedes-Benz’s Body and Equipment Guideline for the Sprinter (model series 907), edition 2025-06.

What Mercedes’ figure
Alternator (OM654) 250 A standard (M60), 280 A optional (M61)
Main battery AGM. 70 Ah H6 standard (ED1), 92 Ah H8 optional (ED4)
Factory aux battery 92 Ah H8 under the front passenger seat (E2I) or 70 Ah H6 in the engine bay (E2M), joined by cutoff relay E36
Current across the cutoff relay 80 A total, charging current included
Added battery of another type Only behind a DC/DC converter or charger at E36 fuse connection A4; charge limit 80 A max
Batteries over 100 Ah Must not connect directly to the vehicle system
Aux battery fuse box (driver seat frame) A1 up to 100 A, A2 up to 250 A, A4 125 A/150 A for E36, A5 and A6 up to 80 A
Upfitter strip EK1 (driver seat base) D+ 10 A, 30T 25 A, terminal 15 15 A

Does a Sprinter need a DC-DC charger for a lithium battery?

Yes, and here it’s the maker’s rule, not just good practice. Mercedes says to use only AGM for the van’s own batteries. Anything else, lithium included, goes behind a current limiter that tops out at 80 A.

The Victron Orion-Tr Smart 12/12-30 isolated DC-DC delivers 30 A, so it sits well under that limit. It charges the lithium bank with its own profile, so the van’s AGM batteries keep the charge Mercedes intended.

The isolated version also fits Mercedes’ thinking on separation. The guide says not to tie added alternators into the van’s system and to keep systems galvanically isolated. That rule is about alternators, not chargers, but if you want the house side fully separate, the isolated Orion keeps input and output apart.

Mercedes adds two rules people miss:

  • Nothing on the main battery’s negative terminal. No extra wires there at all, and the positive terminal isn’t for added loads either. Use the fuse box and upfitter points instead.
  • Outside charging only with the engine off. If you charge the aux battery from a separate charger or a solar controller, the guide says to do it only while the engine is stopped (relay open, terminal 15 or D+ off).

The longer comparison of combiners vs DC-DC chargers is in Charging lithium from a boat alternator: 3 ways compared. It’s written for boats; the charger logic carries over.

You’ll need

Steps

  1. Confirm E36. The guide’s DC/DC rule hangs off the cutoff relay’s fuse connection A4. No E36 means you should read the guide again for your van’s setup before going further.
  2. Pick your feed point at A4, as Mercedes describes. Don’t reuse a fuse that’s already assigned. The guide says to add separate fuses.
  3. Fuse the charger input at 60 A and keep the run short.
  4. Ground where the BEG tells you to, never on the main battery’s negative terminal.
  5. Wire the charger output to the lithium bank, fused at the battery.
  6. Use D+ for engine-running. EK1 has a D+ terminal (10 A) that Mercedes lists alongside the ignition and battery feeds. Wire it to the charger’s remote input as the Orion manual shows, so charging follows the engine, not just the voltage.
  7. Set the lithium profile, add the SmartShunt, then drive and check that charge current matches what you set.
  8. Add solar last. Mercedes’ engine-off rule covers outside charging of the aux battery, so read section 8.3.2 and plan how your solar fits before you wire it.

Shore power and any 120 V inverter wiring: that’s for a licensed electrician.

Does this page fit your van?

It fits a Sprinter in model series 907 with the OM654 engine, as covered by Mercedes’ BEG edition 2025-06, with or planning the E36 relay.

It doesn’t fit the older 906 Sprinter (different guide and a separate 2017 bulletin), the eSprinter, or a van where an upfitter has already rewired the aux battery side. For those, start from the guide edition for your van.

Products for this setup

Product Why it’s here
Victron Orion-Tr Smart 12/12-30 isolated DC-DC The DC/DC charger Mercedes’ rule calls for; 30 A output.
Victron SmartShunt 500A Counts every amp in and out of the house bank.
Victron SmartSolar MPPT 100/30 Roof solar, up to 100 V of panels, 30 A of charge.
Victron Smart BatteryProtect 100A Shuts house loads off before the bank goes too low.

Prices show live from the store.

Bundles for this job: Dual-battery DC-DC charging kit, Van solar starter kit

Quick answers

What alternator does a Sprinter 907 have? Mercedes lists 250 A as standard on the OM654 and 280 A as an option.

Can I connect a lithium battery straight to the Sprinter’s aux battery circuit? Not per Mercedes. A battery of a different technology needs a DC/DC converter or charger between it and the E36 relay connection, limited to 80 A.

Where can I ground my house system in a Sprinter? Not on the main battery’s negative terminal; Mercedes forbids extra lines there. Follow the BEG’s grounding notes for your van.

Sources

  • Mercedes-Benz Body and Equipment Guideline, Sprinter BM907, Edition 2025-06: https://www.mbvans.com/content/dam/mb-vans/us/upfitter/06062025_BEG_Sprinter_907.pdf
  • Victron Orion-Tr Smart DC-DC Charger Isolated manual (Rev 14, 02/2026): https://www.victronenergy.com/upload/documents/Orion-Tr_Smart_DC-DC_Charger_-_Isolated/34439-Orion-Tr_Smart_DC-DC_Charger-pdf-en.pdf
  • Victron SmartSolar MPPT 100/30 & 100/50 datasheet: https://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-100-30-&-100-50-EN.pdf
Amp Hour Supply

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