Lithium Battery Upgrade: Cost, Hours and Process in Hacienda Heights

Lithium iron phosphate takes a different charge profile than lead acid, has a different voltage curve, tolerates deeper discharge, accepts far higher charge current, and carries an internal management board that will disconnect the bank to protect itself. Each one of those differences touches a component that was chosen for the old chemistry.

The converter is the first. A WFCO or Progressive Dynamics unit set for lead acid will either undercharge lithium forever or hold it at an absorption voltage it should not sit at. Either the unit supports a lithium profile or it gets replaced. There is no third option that ends well.

The second is protection thresholds. An inverter with a low voltage cutoff set for lead acid will shut down while a lithium bank still has meaningful capacity, which is the most common complaint we hear from owners who did the swap themselves and felt like they bought less battery than they paid for.

• Converter or inverter charger with a selectable lithium profile
• Solar charge controller reprogrammed to the lithium curve
• Inverter low voltage cutoff and alarm thresholds reset
• Interconnect and main cable sizing for the higher charge acceptance
• A shunt based monitor, because lithium voltage tells you almost nothing
• Compartment temperature consideration, since charging below freezing is restricted

Amp hour math is easy and usually beside the point. What matters is the largest sustained load and the overnight energy budget. A coach with a residential refrigerator, a residential microwave and a CPAP has a different requirement than a coach that runs lights, a pump and a television.

We build the number from measured draw rather than from a nameplate list. The residential refrigerator is usually the swing item, and the second is whether you intend to run air conditioning off the bank at all, which changes both the battery count and the inverter.

The honest answer for a lot of owners is that two lithium batteries with a good monitor and a correct charging profile solve the actual complaint, and four would be capacity nobody uses. We would rather scope it that way than sell the bigger bank and have you discover it later.

The band on this page runs from a two battery conversion with a compatible existing converter at the low end to a four or six battery bank with a new inverter charger, a solar controller, new cabling and a monitor at the top. Labor is the posted mechanical and electrical rate of $260 per hour across 4 to 20 hours, and battery lead time is 5 to 15 business days.

On pure cost per usable amp hour over service life, lithium generally comes out ahead of lead acid because you use a much larger share of the capacity and the cycle life is several times longer. Whether it pays back for you specifically depends on how often you are actually off shore power.

The two arguments that convince most owners are not financial. The first is weight, because a lithium bank is roughly a third of the mass of the lead acid bank it replaces and many coaches are close to their cargo limit. The second is that nobody has to reach into a hot compartment with distilled water again.