Leisure Travel Vans Unity – 12V Lithium Battery Bank & Solar Upgrade

Staring at a battery monitor that won’t stop flashing warnings? Wondering if you can actually trust what it’s telling you anymore, or if you’re one dead night away from being stuck in the dark with a fridge that won’t run? That’s the call I get, and it usually means the same thing: the original battery pack is finally giving up, and the owner’s been watching the signs for weeks without pulling the trigger on a fix. A weak battery doesn’t improve on its own—it just gets worse, slower, until one morning you wake up and there’s nothing left. The Leisure Travel Vans Unity’s 12V lithium battery bank and solar system swap solves this permanently, but only if you move on it before you’re stranded two states from a service center. What follows is exactly how I approach this job: the tests I run first, the parts I verify, the install sequence that keeps you from creating new problems while fixing the old one. You can follow along and do this yourself, or at least walk into a conversation with a tech knowing what actually needs to happen instead of what they’re hoping to upsell you on.

The Battery That Finally Stopped My “Low Power” Panic at 2 AM

Most van owners don’t realize their lead-acid battery is already dying the moment they buy it used—they just don’t know it yet. A lithium drop-in swap gives you the actual amp-hours you paid for, plus the peace of mind that you won’t be stranded at a boondocking spot because your battery monitor was optimistic about your reserves.

What works

• You actually get the full 100Ah usable capacity—no mystery voltage sag that makes your fridge cut out when you’re halfway through dinner.
• Charges 3-4x faster than lead-acid, so a solar day actually replenishes your bank instead of just trickling juice back in.
• Works with your existing 12V system without rewiring—bolt it in where the old battery was and move on with your trip.

What doesn’t

• The upfront cost stings—you’re looking at 2-3x the price of a decent lead-acid, which is a real pause when you’re already deep into van upgrades.
• If your charging system is sketchy or your voltage regulator is old, you need to fix that first—lithium won’t tolerate the overcharge voltages that lead-acid puts up with.

I almost chickened out on the swap after seeing the invoice, convinced the battery I had would limp along for one more season. Three weeks into my next road trip with lithium installed, I realized I’d actually gained back my evenings—no more rationing power or killing the fridge to save amp-hours. If you’re tired of planning your day around your battery, grab a 12V 100Ah LiFePO4 Lithium Battery and stop waiting for the breakdown.

Part-Level Diagnostics

This guide covers the install on this coach. These go deeper on the sizing and wiring decisions behind it:

• Sizing a Victron SmartSolar MPPT: what the 100/30 numbers limit
• DC-DC charger vs. alternator: why your alternator won’t charge LiFePO4
• Battery cable and ANL fuse sizing for a lithium bank
• BMV-712: the shunt wiring mistake that ruins state of charge

What Battery Group Size Does the LTV Unity Use?

The first question most people ask when planning a Leisure Travel Vans Unity house battery swap is simple: what size battery fits in there? The answer requires understanding what “group size” actually means, because it’s not a capacity rating—it’s a standardized case footprint and terminal layout set by the Battery Council International. Group 31, for instance, tells you the physical tray dimensions and where the positive and negative posts sit, but it doesn’t tell you whether you’re getting 100Ah or 200Ah inside that footprint.

The factory AGM house banks in most Leisure Travel Vans Unity builds—whether you have the Murphy Bed, Corner Bed, Island Bed, Twin Bed, or Rear Lounge floorplan—are typically sized as Group 31 batteries. That’s a case measuring roughly 13 inches long by 6.8 inches wide by 9.4 inches tall, with terminals on one of the short faces. The good news is that Group 31 is also the most common drop-in replacement footprint for 12V LiFePO4 lithium batteries, which means most Unity lithium conversions are mechanically straightforward: the new battery sits in the same tray, uses the same hold-down strap, and bolts to the same cable lugs.

But year-to-year and floorplan-to-floorplan, LTV changed battery compartment layouts and cable routing. A Sprinter-chassis Unity has tighter compartment clearances than an older model on a different platform. Some model years have the tray positioned with terminals facing forward; others have them facing sideways. The only authority on what actually fits in your rig is your own battery compartment, not a spec sheet I found online.

Measuring Your Tray Before You Order

Before you add a lithium battery to your cart, spend fifteen minutes measuring your existing battery tray and compartment. This takes the guesswork out of whether a drop-in swap will actually work.

1. Measure the inside length, width, and height of the battery compartment with a tape measure. Include the space consumed by any hold-down hardware or restraint straps.
2. Note whether the existing battery terminals are on the long face (side-by-side posts) or the short face (posts facing forward or back). Check which terminal is positive and which is negative, and note the post diameter.
3. Look at your positive and negative battery cables. Measure how far they reach and confirm that a drop-in replacement won’t put the terminals on the opposite side—if it does, you’ll need longer cables or a relocation of the tray itself.
4. Check clearance above the battery. Many LiFePO4 batteries have slightly different height profiles than the OEM AGM. Make sure the compartment lid, vent ducts, or converter still fit after the swap.
5. Test the hold-down strap or frame with the new battery in place (dry run, no power connected) to ensure it still seats and tightens without binding.

Once you have those numbers, compare them against the lithium battery spec sheet before you order. A Group 31 LiFePO4 should fit, but there’s no such thing as a guarantee until you’ve verified against your own rig.

Group 31 vs. Other Footprints

Not every Unity uses a Group 31 tray. Depending on model year and configuration, you might see a Group 24, Group 27, or even a pair of GC2 golf-cart batteries. Here’s how the common options stack up:

Group Size	Typical Dimensions	Typical Capacity (AGM)	Fits Unity Tray?
Group 24	10.2 x 6.7 x 8.3 inches	70–85Ah	Older models only; verify your tray
Group 27	12.1 x 6.8 x 8.8 inches	85–105Ah	Possible on some builds; measure to confirm
Group 31	13.0 x 6.8 x 9.4 inches	100–120Ah	Most common in LTV Unity; most lithium drop-ins match this
GC2 pair	Two units at 8.3 x 7.0 x 10.5 inches each	200–220Ah combined	Rare in recent Unity models; requires dual battery management

The table above is a guide, not gospel. Check your own battery compartment before ordering, because LTV sourced batteries from different suppliers over the years and compartment layouts vary.

What Else Has to Change With the Battery

Dropping a 12V lithium battery into your Unity’s existing tray is only half the job. The charging and protection systems have to change too, or you’ll end up with a battery that never fully charges and a charger that ages ten years in one season.

Your converter/charger—the device that charges the house battery from 120V AC when you’re plugged in—has to be set to a lithium profile or configured with the correct bulk and float voltages. Most factory Unity converters are programmed for AGM lead-acid, which uses different charge curves. If you leave it on AGM mode, your lithium bank will float at a voltage that keeps it in a partial state of charge and never tops out. Some converters can be reprogrammed via a control panel or app; others require a firmware update or a replacement unit.

The alternator charging path also matters. On a Sprinter-chassis Unity, your alternator’s high-current output may cause voltage spikes or overcharging scenarios that lithium won’t tolerate. Many Sprinter builds benefit from a DC-DC charger, which sits between the alternator and the lithium bank and regulates the input voltage and current. It’s not always mandatory—some setups work fine without it—but it’s a safety margin I’d rather have than not.

Battery cable and ANL fuse sizing must match the higher current capability of lithium. A 100Ah LiFePO4 can accept and deliver 100+ amps, whereas your original lead-acid cables might have been sized for half that. Undersized cables and fuses create heat and fire risk. If you’re moving from a Group 31 lead-acid to a Group 31 lithium with the same physical footprint, assume you need to upsize your cable gauge and fuse rating.

Finally, LiFePO4 chemistry cannot be charged below freezing without an internal battery heater. If you boondock in winter or travel through cold climates, you need either a heated battery or a low-temperature charging cutoff in your charger or BMS. Without it, you’ll damage the battery if you try to charge it when the cell temperature is below 32 degrees Fahrenheit. This is a real limitation, not marketing hype.

House Battery Sizing for a Leisure Travel Vans Unity: Frequently Asked Questions

What size house battery is in a Leisure Travel Vans Unity?

The factory Leisure Travel Vans Unity comes with an AGM lead-acid house battery that is typically Group 31 sized with a nominal capacity of 100–120Ah. The exact amp-hour rating depends on the battery manufacturer and model year. Some older or base-model Unity builds may have had Group 24 or Group 27 batteries instead. The only way to know what’s in your rig is to open the battery compartment and read the label on the existing battery, or check your build spec sheet from LTV.

Can I put a lithium battery in my Unity without other changes?

Physically, you can bolt in a Group 31 LiFePO4 battery in place of your factory AGM and it will work. The 12V connections are the same, and the footprint fits the tray. But “without other changes” stops there. Your converter/charger settings must be updated to lithium, your alternator charging path may need regulation via a DC-DC charger, your cable and fuse sizes should match the higher current lithium can deliver, and you need a low-temperature charging cutoff if you’re in freezing climates. If you skip those steps, you’ll get poor charge performance, shorter battery life, or safety hazards. Don’t treat it as a true plug-and-play swap.

How many amp hours do I need for boondocking in a Unity?

That depends on how you use the rig. A couple camping four nights with a fridge, fan, and lights might draw 20–30Ah per day and get by on a 100Ah battery if the sun cooperates. A full-timer running a heater, water pump, and charging devices in cloudy weather might need 200Ah or more. The real answer is to track your own amp-hour consumption over a week of normal use, compare it to your solar recharge rate in your typical climate, and size the battery to handle three to five days without sun. A 100Ah LiFePO4 gives you far more usable capacity than the original lead-acid because you’re not losing voltage sag and can safely discharge to 20 percent. Most Unity owners find that 100Ah lithium is a genuine upgrade, even though it’s the same nominal capacity as the factory battery it replaces.