Toy Hauler Lithium vs Generator: What Lithium Replaces and Whether It Starts the Onan

The dunes boards ask it every fall when the generator comes out of storage: can I go lithium and leave the generator at home, and will the lithium even start the Onan. The answers are "for most things, yes", "for the air conditioner, no", and "usually, but check one number first".

What a lithium bank replaces

A toy hauler's generator does three jobs: it runs the roof air conditioner, it recharges the house battery, and it powers the 120 volt outlets. A lithium bank with an inverter takes over the second and third completely. Lights, water pump, fans, the fridge on 12 volts, the television, charging phones and radios, and the microwave through the inverter all run from a 280 amp-hour lithium for a weekend without the generator ever starting. That is the quiet camp everyone at Glamis wants, and it is real.

What it does not replace: the air conditioner

A 13,500 BTU roof air conditioner draws roughly 1,300 to 1,500 watts running. At 12 volts that is around 110 to 130 amps. Divide a bank's capacity by that:

A September afternoon in Imperial County needs the air conditioner for eight hours. No bank a toy hauler can carry does that, and a bank big enough to try would cost more than the generator it replaces. The honest design is lithium for everything except the air conditioner, and the generator for the air conditioner and for fast recharging.

Will lithium start the Onan

In most toy haulers the generator cranks from the house battery, and a lithium bank cranks it fine provided the battery's management system allows the starter's inrush. Every lithium battery has a peak discharge rating, usually several hundred amps for a second or two, and a starter draws a large current for exactly that long. Check the battery's peak discharge rating before buying; a battery rated for a modest continuous current with a low peak can cut out mid-crank and reset, which reads as a dead generator. Owners on the boards run Onan 4000s from lithium banks routinely, with a converter set to a lithium profile, and the ones with trouble are usually running a battery with a low peak rating or a corroded starter connection that was marginal on lead-acid too.

Test it once at home: converter off, generator cold, crank. If it starts, it will start at the dunes. If you want belt and braces, keep a small lead-acid for generator starting and let the lithium run the house, with a DC-DC charger between them.

Recharging fast, because generator hours are the cost

Lithium takes charge as fast as you can supply it, which is where the generator earns its keep on the trips it does come along. The factory converter charges at 45 to 60 amps, so a flat 280 amp-hour bank is four to six hours of generator noise. A MultiPlus inverter-charger charges at up to 120 amps and halves that, and it doubles as the inverter for the outlets. Solar on the roof, through a SmartSolar MPPT, covers the daily draw in dune sun so the generator only runs for the air conditioner. On the drive out, an Orion XS fed from the truck puts 50 amps into the bank so you arrive full.

Whatever mix you run, a SmartShunt on the battery negative is the gauge that tells the truth. Lithium sits at the same voltage from full to nearly empty; without a shunt you find out it was empty when the fridge stops.

The battery

A 280 amp-hour lithium in a metal case is the size that fits most toy-hauler battery compartments and is the one to build around; two in parallel if the compartment allows. Our guides to shore power versus generator versus solar and to installing a 280 Ah battery cover the fusing, which on lithium needs an interrupt rating the old fuse did not have, and the converter profile.

The short version

Lithium for the camp, generator for the air conditioner, a MultiPlus to make the generator hours short, a shunt so you know. Send us the compartment dimensions and the generator model and we will spec the bank. We are in Upland, on the way to Glamis, if you would rather collect it.