The lithium battery for your Hymer motorhome.
Hymer build some of the most sophisticated motorhomes in Europe, from the compact Grand Canyon campervan to the flagship B-Class MasterLine A-class, and most models leave the factory fitted with a sealed AGM leisure battery that limits you to roughly half its rated capacity. A UK-engineered TITAN lithium fits the same locker, gives you the full usable capacity, and on the premium SLC-chassis models complements the Hymer energy system or replaces a factory lead-acid bank without modifying the shell.
German engineering on two platforms - and why the base vehicle matters
Hymer, based in Bad Waldsee in southern Germany and part of the Erwin Hymer Group, has been building motorhomes since 1957. The range spans from compact panel-van campervans all the way to full A-class integrated coaches and splits across two base vehicles: Fiat Ducato on the more compact coachbuilts and campervans (the Exsis-t, Exsis-t Pure, and the Ducato campervan family including the Grand Canyon, Ayers Rock, Yosemite and Yellowstone), and Mercedes-Benz Sprinter on the larger and premium models (B-Class ModernComfort, B-Class MasterLine, ML-T, T-Class S, GT-S, Venture S and Grand Canyon S). Which base you have makes a direct difference to how the alternator charges the leisure battery - and whether you need additional hardware to do it reliably with lithium.
Most Hymers leave the factory with a sealed AGM leisure battery - 80Ah to 100Ah on smaller models, larger AGM banks on bigger coachbuilts. On the top-specification B-Class MasterLine and B-Class ModernComfort, Hymer offers their own Smart Battery System 2.0 using LFP cells as standard or an option. If your Hymer came specified with that factory lithium system, the charging infrastructure may already be appropriate for lithium. If you are upgrading from a factory AGM, the charging setup needs a closer look on both the Ducato and Sprinter platforms.
For the full picture on switching to lithium in a coachbuilt, the motorhome battery guide covers the fundamentals. To compare Hymer against other brands, the motorhome brands hub has the full picture.
Sizing a Hymer by model
A starting point by model family. Larger A-class integrateds have more locker and payload headroom; compact campervans have a tighter DIN tray. Measure your specific locker before ordering.
| Model | How it gets used | Good fit |
|---|---|---|
| Fiat Ducato campervan (Grand Canyon, Ayers Rock, Yosemite, Yellowstone)Panel-van base, 2-4 berth, compact, 3,500-4,250 kg | Weekend and touring, fridge, lights, devices, off-grid nights | 100Ah to 180Ah |
| Exsis-t / Exsis-t Pure (Fiat Ducato, semi-integrated coachbuilt)Lightweight coachbuilt, 4 berth, typically 3,500-3,850 kg | Touring with heating, water pump, fridge, multi-night stays | 150Ah to 230Ah |
| B-Class ModernComfort T / ML-T / T-Class S / GT-S (Sprinter, semi-integrated)Mid-to-premium coachbuilt, 4-6 berth, SLC chassis on some variants | Longer stays, inverter use, full heating, extended off-grid | 150Ah to 230Ah |
| B-Class MasterLine I / B-Class ModernComfort I (Sprinter, A-class integrated)Flagship integrateds, 4-6 berth, SLC double floor, maximum payload | Extended off-grid, high loads, inverter, air conditioning, full winter use | 230Ah to 330Ah |
These are starting points, not fixed rules. The honest figure comes from your own loads, not the model name, so total them in the battery size calculator. Battery lockers and trays vary by model year and Hymer specification level - measure your existing space, including terminal height, before ordering. For larger banks, matched packs can be run in parallel where the locker allows.
Where the leisure battery lives in a Hymer
Battery location in a Hymer varies significantly by model class and base vehicle. As a general guide:
- B-Class MasterLine and B-Class ModernComfort (SLC chassis). Hymer's SLC (Super Light Chassis) features a 36 cm high, heated and insulated double floor that integrates the tank system, heating and, on models specified with the Smart Battery System 2.0, the LFP battery modules. On models fitted with a conventional leisure battery instead, the battery typically sits in an external service locker accessed from outside the habitation section. Check your build specification carefully - the SLC double floor is not a simple open bay on all configurations.
- Exsis-t and Fiat-based semi-integrated coachbuilts. On these lighter coachbuilts, the leisure battery is usually in an external locker at the front nearside of the habitation section, alongside the fuse board and, on newer models, the solar controller. There is generally good clearance for a standard DIN case here, but measure including terminal height before ordering.
- Fiat Ducato campervans (Grand Canyon, Ayers Rock and others). Panel-van campervans generally locate the leisure battery under a cab seat or in a front locker behind the cab partition. Locker dimensions can be tight on short-wheelbase models, so confirm clearance for a DIN case including the terminal strip before buying.
- ML-T, T-Class S and GT-S (Sprinter semi-integrated). These models typically have the battery in an external service locker, though position varies by floorplan and model year. Consult your handbook and measure the tray.
Because the TITAN case is sealed to IP67, it handles damp and dust in any of these locations without issue. The RJ45 comms ports drop to IP32 while a cable is connected, so keep any plugged port clear of standing water. Battery positions and tray dimensions vary between Hymer model years and specification levels - always measure your space and include terminal clearance rather than relying on a brochure figure from a different build year.
Charging a Hymer from alternator, solar and mains
A Hymer charges its leisure battery from three sources: the engine alternator while driving, roof solar through an MPPT controller, and the on-board mains charger on hook-up. Lithium accepts all three more quickly than the AGM it replaces, so a decent drive or a bright afternoon puts real capacity back rather than a slow overnight trickle.
The alternator is where both Hymer base vehicles need careful thought. Current Fiat Ducato Euro 6eBis engines and the Mercedes-Benz Sprinter 315 CDI Euro VI-E (the VS30 platform introduced from 2019 onwards) both run variable-voltage smart alternators. These manage their output voltage dynamically to reduce fuel consumption and load during acceleration - which means they will not reliably fill a lithium battery on their own. Output can drop below the level lithium needs to charge properly, leaving you with a half-full bank even after a long motorway run.
The right fix is a DC-DC charger, also called a battery-to-battery charger, wired between the starter battery and the leisure bank. We would fit a Victron Orion every time - it takes whatever the smart alternator is providing at any point in the drive, regulates it into a clean controlled charge profile for lithium, and protects the starter battery from being drawn down. A standard split-charge relay is less reliable for lithium with a smart alternator: some relays cause a backfeed that quietly limits how much capacity you can access, and others simply cannot handle the dynamic voltage from a Euro 6-era engine. Feeding straight off the alternator with no relay and no DC-DC unit is not something we recommend.
One exception worth noting: B-Class MasterLine and B-Class ModernComfort models fitted with Hymer's Smart Battery System 2.0 include a factory charging booster (up to 70A) specifically designed to handle alternator charging for those LFP modules. If your Hymer was specified with Smart Battery System 2.0 from new, the charging infrastructure may already be in place for that system. If you are upgrading an AGM-fitted Hymer to a TITAN lithium, add the DC-DC charger as part of the installation regardless of which base vehicle you have.
Plan your roof array with the solar sizing guide, check your existing mains charger against the compatibility list, and size the battery around the gap your charging sources cannot cover overnight. Every TITAN carries a custom BMS with a built-in low-temperature heater so it charges safely down to -30C, and comes with a lifetime, fully transferable warranty.
