Charging A Deep Cycle Battery From Cigarette Lighter Socket – An Easy Simple Method

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charging a deep cycle battery from cigarette lighter socket

We have a look at Charging a Deep Cycle Battery from Cigarette Lighter Socket

The answer is yes, you can. But it is likely to be slow and could be dangerous if you are not careful.

For charging devices on the go, cigarette lighter sockets are a great option. Either with a direct plug-in or a USB splitter, we can ensure that we’re covered when our devices drain.

But do these magical 12 V sockets have other uses? You bet! In fact, they can be useful to charge 12 Volt batteries when you’re stuck without an AC power source.

Charging a Deep Cycle Battery from Cigarette Lighter Socket

Charging a 12 Volt battery from a cigarette lighter is a simple process. You need the correct devices to feed the power from the socket into the target battery in usable form.

Like any 12 Volt battery, you can charge a deep cycle battery in a variety of ways. The most common of these is to use a battery charger. This is usually a charger that will charge the deep cycle battery using AC power from your mains.

But what if your deep cycle requires a charge on the go? Luckily there are workarounds for this. These involve using the 12Volt cigarette lighter on your dash or in the trunk. The trick is to use equipment to convert the socket output into usable power to charge the battery.


As always with anything involving batteries, the main concern should always be safety. The battery will emit hydrogen during charging. This is explosive in certain concentrations of air. So, you should never attempt to charge the vehicle battery in the passenger area of your vehicle. This is because any rogue spark could cause an explosion. ALWAYS charge any battery in a well-ventilated area.[1]

Differences between Deep Cycle and Starter Batteries

Deep cycle batteries supply appliances with uninterruptible power for an extended period. This is usually in vehicles such as RVs, campers, or boats.  These include microwaves, freezers, and mini-fridges on RVs and campers. And, on boats, fish finders, radio, running lights and navigational aids.[2]

A cranking battery starts the vehicle and powers lights and accessories.  It is also known as an SLI (starting, lights and ignition) battery. So, its main function is to supply a lot of energy fast, to turn over the engine. 

Deep cycles are designed to be continuously discharged and recharged.  During its life, a lead acid deep cycle will provide around 200 cycles, with a depth of discharge of 80% to 100%.[3]

SLI batteries are not designed to do this. While one or two deep discharges won’t harm it, many more will degrade the battery and cause failure. They are designed for a quick, powerful burst of energy that will cause a shallow discharge. The battery will then charge again via the vehicle’s alternator. 

This means that the way that they are charged should be different also. This is because the deep cycle battery is not designed to withstand the heat and speed of a normal charge. So it is important that the charger that you use is suitable for charging a deep cycle battery.

Choose a smart charger designed for deep cycles or that at least has a setting for them.

Importance of the Alternator

The alternator is a very important part of a modern vehicle. It charges the battery, which powers everything from the headlights to the air con to the stereo. 

The alternator will be crucial for recharging the deep-cycle battery. This is because you cannot charge your deep-cycle using only power from the donor battery.

If you attempt to do that, you will charge the deep-cycle at the expense of the donor battery. When one battery charges another, the power passes between them until equilibrium. So you will have two batteries each with a partial charge. 

What you need to do is start the engine. This adds more power to your setup from the alternator. By burning gasoline, it converts chemical energy to electrical energy. You can then use it to charge your deep cycle battery.

Equipment to Use

There are two pieces of equipment that I use to charge my deep cycle from the 12V socket. These are

  • A power inverter
  • A suitable battery charger

Power inverter

A power inverter is a device that converts DC (direct current) to AC (alternating current). Plug one into your 12 Volt socket, and you can pass AC electricity to the battery charger.

A suitable inverter to plug into the cigarette lighter is under 450 Watts. Higher power inverters need to be wired directly into the battery. 

Battery Charger

This is crucial. You need a battery charger capable of charging a deep-cycle battery. I do not recommend using an old-style bulk charger for deep-cycles. It is best to go with a modern smart charger. This will detect the chemistry of your battery and tailor its charge to it. 

The size of the charger will depend on the battery chemistry. For flooded lead acid deep-cycles the largest charger size is 10% of the battery. Whereas for an AGM battery, the charge can be up to 30%.[4]

So it looks like this

  • Lead Acid Battery (100aH) can handle up to a 10 Amp charger
  • AGM Battery (100Ah) can handle up to a 30 Amp charger

You should not exceed these ratios, as it will risk overcharging and can damage the battery. 

Also, it is important to remember that you should not use any appliance on your inverter that will draw more Amps than the lighter fuse can cope with. For instance, most vehicle cigarette lighter fuses are 10 Amps. So, ensure that the smart charger that you use does not have an output higher than 10 Amps, or you’ll blow the fuse.

The above figures show the maximum speed of charge. This is determined by the Amp rating of the charger. So make sure you don’t use a charger with too low a rating, otherwise charging will be too slow or even negligible.

You should take the Amp hour rating of the deep cycle battery and divide it by the Amp rating of the charger. This will give you the approximate charge time. 

So, Battery capacity (Ah) / current (A) = Charge Time

For instance …

That 100Ah lead acid battery charged at 10 Amps will take 10 hours to charge from depleted. 

Also, ensure that the voltage rating of the charger you buy matches the battery. So a 12V charger for a 12V battery. That is very important.[5]

However, any good smart charger will:

  • Auto-detect the battery type (AGM, lead acid, gel, lithium)
  • Auto-detect the charge voltage to charge at the optimum speed
  • Switch to a maintenance charge when full

Charging a Deep Cycle Battery from Cigarette Lighter Socket – Conclusion

So, what does all this mean? The conclusion is that you can charge a deep-cycle battery with your cigarette lighter. You just need the correct kit to do a cracking job.


Here are some FAQs

Can I charge a deep cycle battery from a cigarette lighter?

Yes, you can. Use an inverter to convert the DC current to AC and then send it through a smart charger into the deep cycle battery. Make sure you run the engine intermittently so you don’t drain the vehicle’s own battery.

Can you use a cigarette lighter as a charging port?

Yes, you can. You can buy chargers that plug into the cigarette socket for most devices. You can also get a USB splitter so that you can charge many devices at the same time.

Can I charge a deep cycle battery with a car?

Yes. All you need to do is use jumper cables to connect the battery from your vehicle to the battery you want to charge. Start the engine to send power to the battery you are charging via your engine battery.

What is the largest inverter you can plug into a cigarette lighter?

A cigarette lighter inverter must be under 450 Watts to be suitable for that socket. Direct wiring into the battery is required for higher power inverters.

How many watts does a cigarette lighter put out?

The majority of cigarette lighters employ a 10-amp fuse with a maximum power output of 12 volts or 120 watts. If your vehicle has a 15A fuse it goes up to 180 Watts. Never put a larger fuse in the slot to circumvent this, or you can cause damage to your wiring.

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Steve Brown


Steve is a gadget enthusiast who's always been intrigued by batteries. The founder and editor of Battery Chargers Info, he's assembled a group of like-minded experts to cover every facet of portable power His aim is to help you learn more about your favorite gadgets and their batteries so you can maximize both their performance and their life. Follow him on Twitter: @batterycharge1

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