AGM vs Lithium Battery Calculator: Is the Upgrade Worth It?
AGM vs Lithium Off-Grid Battery Simulator
If you are designing a 12V electrical system for your campervan, boat, or off-grid cabin, you will inevitably face the big question: Is it worth upgrading from AGM to Lithium (LiFePO4)? While deep-cycle AGM batteries are cheaper upfront, that initial price tag hides a massive weight penalty, severe voltage drops, and a surprisingly short lifespan. Lithium batteries offer 100% usable capacity, weigh a fraction of the size, and last ten times longer—meaning they are actually cheaper in the long run. To see exactly what you are getting for your money, use our AGM vs. Lithium Simulator below. Select your target battery size to instantly compare the real-world usable power, weight, and lifespan of both chemistries side-by-side.
⚖️ AGM vs. Lithium Calculator
See the true cost and weight impact of your battery choice.
GVM (Gross Vehicle Mass) is the absolute legal maximum weight your van can carry. Most empty cargo vans only give you about 1,000kg (2,200 lbs) of payload for your bed, timber, water, gear, and passengers. If you choose the AGM route above, those heavy lead plates eat massively into your legal weight limit before you even start building!
People Also Asked: AGM vs. Lithium Batteries
How does my battery choice affect my van’s GVM (Gross Vehicle Mass)?
Your van’s GVM is the legal maximum weight it can carry on the road. Most empty vans only offer 1,000kg to 1,500kg of payload. If you try to achieve 200Ah of usable power using heavy AGM lead-acid batteries, you will add roughly 120kg (265 lbs) to your build. That weight eats directly into your allowance for timber, water tanks, and gear. A 200Ah Lithium battery provides the exact same usable power but weighs only 22kg (48 lbs), saving a massive amount of your legal payload.
Is a Lithium campervan battery really worth the extra money?
Yes, without a doubt. While AGM batteries appear cheaper at checkout, they hide a fatal flaw: you can only safely discharge an AGM battery to 50% capacity before causing permanent damage. A Lithium (LiFePO4) battery can be drained down to 0%, giving you 100% of the power you paid for. To get 100Ah of usable power from an AGM setup, you have to buy (and carry) 200Ah worth of batteries.
Can I just drop a Lithium battery in to replace my old AGM?
Usually, no. Lithium batteries require a very specific, higher charging voltage profile than AGM batteries. If you connect a Lithium battery to an old solar controller or a standard vehicle alternator designed for lead-acid, it will never fully charge and could easily burn out your van’s alternator. You must upgrade to a Lithium-compatible DC-DC charger to safely make the switch.
Which battery is safer to sleep next to in a van?
Lithium iron phosphate (LiFePO4) is the clear winner for interior safety. Traditional flooded lead-acid and some AGM batteries can off-gas toxic and explosive hydrogen fumes while charging, meaning they must be stored in a sealed, externally vented battery box. LiFePO4 batteries are completely sealed, do not off-gas, and are chemically stable, meaning you can safely mount them under your bed or inside an enclosed bench seat without risking your health.
How long do Lithium batteries last compared to AGM?
An average AGM battery is rated for about 500 charge cycles before it dies. If you live in your van full-time, you might destroy an AGM bank in just 2 years. A modern Lithium battery is rated for 3,000 to 5,000+ cycles. Even with heavy daily use, a quality Lithium battery will easily last 10 to 15 years, making it significantly cheaper over the lifespan of your campervan.
Do Lithium batteries work in freezing winter temperatures?
You can safely *discharge* power from a Lithium battery in freezing weather, but you cannot charge a standard Lithium battery if its internal core is below 32°F (0°C). Doing so will instantly ruin the battery.
❄️ Winter Van Life Hack: If you plan to camp in the snow, you don’t have to settle for the extreme weight of AGM. Simply buy a Self-Heating Lithium Battery. These brilliant batteries use incoming solar or alternator power to warm up an internal heat mat first. Once the core is safely above freezing, they automatically allow the charge to flow.