Deep cycle batteries provide backup power for many applications – offgrid or even just as a backup power supply.
If your car battery is down and you have a deep cycle battery laying around or if you mistakenly purchased a deep cycle battery instead of a starter battery, you may be tempted to use it to start your car.
In this guide, I answer the question of whether you can use a deep cycle battery to start your car, the risks you expose it to if you use it to start a car, and lastly whether you can charge it using the car alternator.
Can a Deep-Cycle Battery be Used to Start a Car?
Yes, you can use a deep-cycle battery to start a car in an emergency provided it is able to supply the cranking amps that the car needs.
Keep in mind though that doing so can void its warranty so consider the pros and cons of doing so.
For long-term use, it is not recommended unless it is a starting battery.
Should You Use a Deep-cycle Battery to Start a Car?
Yes, if it is designed as a starting battery then you can use it to start a car. Starter batteries are designed to supply large bursts of current to enable the engine to start.
If it is simply a deep cycle but not designed for starting then it will possibly not be able to deliver the required number of amps to start the car unless it is oversized and that makes it more expensive compared to a normal starting battery.
Why can’t a deep cycle battery be used to start a car?
A deep cycle battery (none starter) should not be used to start a car as it is not designed to supply the high starting amps that vehicles need at startup.
While it may be able to work (in an emergency), you risk damage to it if you use it to start the car.
What Happens when You Use a Deep-Cycle Battery to Start a Car?
If it is a deep cycle starting battery then there is no danger posed to the battery provided it is designed to meet the cranking amps of the car.
If on the other hand, it is just a deep cycle battery then it is suited to supplying a steady current over time and its lifespan will be shortened if it is used to start a car.
Can You Charge a Deep-Cycle Battery with a Car Alternator?
While you may be able to charge a deep-cycle battery with a car alternator, it is generally not a good idea for all types of deep-cycle batteries because of the risk of damage they are exposed to when charged using higher than recommended currents.
Batteries also have a specific float and cycle voltage requirements that they should be charged to for them to last which a car alternator is not designed to provide.
For example, a deep cycle GEL battery should be charged to about 13.6 ~ 13.8V DC which is below the maximum voltage of many car alternators of 14.5V.
It is best that you use a car alternator to only charge deep cycle car batteries.
For other batteries, you can use a specific charger or normal charger with the voltage settings adjusted to suit the manufacturer’s recommendations for that battery type.
Can a Deep Cycle Battery Be Used for Car Audio?
Yes, you can use a deep cycle battery to power your car’s audio without the risk of damage to the battery regardless of whether it is a solar battery or a car starting battery. This is because the current draw of a car’s audio is generally steady and does not put any excessive demand like when a car is starting.
Take care not to discharge the battery below the recommended depth of charge by the manufacturer or else the battery will not last for the intended lifespan.
In addition, follow the recommended guidelines on how to make your battery last.
Final Word
In summary, a deep cycle battery can be used to start a car in an emergency (this may void the battery warranty) but for long-term use, this is not recommended unless it is as a starting battery.
Starting batteries can provide the high cranking amps that the car engine needs to start.
A deep cycle non-starting battery needs to be oversized to supply the required cranking amps which makes it expensive compared to using an ordinary starting battery.
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