What battery capacity (Ah) actually means
When you’re looking at caravan leisure batteries, one of the first numbers you’ll see is capacity, measured in amp-hours (Ah).
A 100Ah battery.
A 110Ah battery.
A 200Ah battery.
On the surface, it sounds simple — bigger number = more power.
But what does Ah actually mean in real-world caravan use?
Let’s break it down without the electrical jargon.
What does “Ah” stand for?
Ah means amp-hours.
It’s a measure of how much electrical energy a battery can supply over time, not how powerful it is at any one moment.
In simple terms:
Amp-hours tell you how long a battery can supply electricity, not how strong that electricity is.
The bucket analogy (the easiest way to think about it)
Imagine your battery as a bucket of electricity:
Ah rating = how big the bucket is
Your appliances = how fast you’re pouring electricity out
Time = how long the bucket lasts before it’s empty
So:
A 100Ah battery is a smaller bucket
A 200Ah battery is a bigger bucket
Running more things empties the bucket faster
What does a 100Ah battery actually give you?
In theory:
100Ah = 100 amps for 1 hour
Or 10 amps for 10 hours
Or 1 amp for 100 hours
But caravanning isn’t theory — and this is where people get caught out.
The usable capacity trap (very important)
Most lead-acid, AGM and gel batteries should not be fully drained.
As a rule of thumb:
You should only use about 50% of a lead-based battery’s capacity
Going lower regularly shortens battery life dramatically
So in reality:
Battery sizeUsable capacity100Ah~50Ah usable110Ah~55Ah usable200Ah~100Ah usable
This is why people say:
“My 100Ah battery didn’t last the weekend.”
It probably did exactly what it was designed to do.
Why Ah doesn’t tell the whole story
Two caravans with the same battery can have very different experiences.
Because Ah doesn’t account for:
How efficient your appliances are
Whether you’re running a mover, inverter, TV, heating fan, or compressor fridge
How cold it is (cold reduces capacity)
How old the battery is
Whether solar is topping it up during the day
So Ah is capacity, not a promise.
Common Ah misunderstandings
“A bigger Ah battery gives more power”
Not exactly — voltage (12V) stays the same. You just get power for longer.
“I only need a small battery because I’m on hook-up most of the time”
True — until you stop overnight, lose hook-up, or need the mover.
“My caravan came with a 100Ah battery so that must be enough”
Enough for basic use — lighting, water pump, control panel — not heavy off-grid use.
Ah vs real caravanning use
Think in time, not numbers:
How many nights without hook-up?
Do you watch TV or use an inverter?
Do you rely on solar?
Do you use a mover often?
Winter touring or summer only?
Ah helps you estimate, but usage decides the outcome.
The takeaway
Ah = how long your battery can supply power
You only get about half of a lead-based battery’s rated capacity
Bigger Ah means longer runtime, not stronger electricity
Your usage matters more than the number on the label
Understanding Ah won’t magically make your battery last longer —
but it will stop you expecting miracles from it.