How Long Does it Take to Charge a 72v Battery?

If you’ve read our Best Sur Ron Battery Charger Options article you’d have a pretty good idea which Sur Ron charger you want. But will it charge a 72v battery? How fast?

A bigger 72v battery means more fun on your Sur Ron. 

But how long does it take to charge a 72v Sur Ron battery? 

How long it takes to charge a 72V Sur Ron battery depends on your battery’s capacity. Not Voltage.

You can’t tell how long a Sur Ron battery will take to charge by looking at its voltage. We’d have to look at the amp hours or capacity to figure it out. Let’s do this.

Recap: How Do You Charge a 72V Battery?

Like we talked about in our How Do You Charge a Sur Ron Battery article, you can charge a 72V battery by taking it out of the bike’s battery compartment and directly plugging in the charger through the charging port.

Like all Sur Ron batteries, a 72v Sur Ron battery will have positive and negative connectors, as well as a charging port (though sometimes you’d need a different charger plug than the stock).

How long it will take to charge will depend on your battery capacity and charger current. Let’s get started.

How Do You Calculate How Long It Will Take to Charge a battery?

Here’s a simple formula for battery charging current and battery charging time with a solved example of a 120Ah battery.

This is how you figure out how long it takes to charge a lead acid battery.

Time it takes to charge a battery = Battery Ah / Charging Current

T = Ah / A


T = Time hrs.

Ah = Ampere Hour rating of battery

A = Current in Amperes


Let’s say you have a 120 Ah battery:

We’ll start by calculating the charging current for a 120 Ah battery. Generally, charging current should be 10% of the Ah rating.


For a 120Ah Battery, charging current is 120 Ah x (10/100) = 12 Amps.

However, due to some losses, we may take 12-14 Amperes instead of 12 Amperes when charging batteries.

Let’s say we take 13 Amps for charging,


Battery charging time for 120Ah is 120/13 = 9.23 hrs.

However, this was an ideal case.

In practice, 40% of losses occur when charging batteries.

(120Ah x 40% of losses) = 48 ..

As a result, 120 + 48 = 168 Ah (120 Ah + losses)

The charging time of the battery is now Ah / charging current

Setting the values;

It’s like 168 / 13 = 12.92 or 13 hours ( in real life)

So, a 120Ah battery would take 13 hours to charge up if the charging current is 13A.

Can you Overcharge a 72V Battery?

No, you cannot overcharge a 72V Sur Ron battery. 

Most batteries nowadays are equipped with an overcharge protection circuit. Overcharge protection circuits use Zener diodes to stop batteries from overcharging. 

When a battery is charged, the terminal voltage (the voltage between cathode and anode) increases. When it’s fully charged, the terminal voltage peaks. The battery or charger detects this and shuts off the energy distribution. 

As soon as that happens, the charger goes into standby with a green light in most cases.

Also read: Can I Leave My Ebike on Charge Overnight?

Nick Gutladera Bricks Mud Bike

Nick Ylac Gutladera — Lead Writer

Nick got his start by stealing his father’s dirt bike and riding it around the neighbourhood at the tender age of 11. These day’s he’s got a full license, so the cops mostly leave him alone. On weekends, he races pit bikes, enduro bikes, and anything else with a motor. Nick’s been a journalist and professional writer since 2017.

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