Can I Connect Two Batteries of Different Voltage in Parallel?

Connecting two batteries with the same voltage in parallel generates output. However, if you connect them at different voltages, you’ll create a complex short circuit. The battery with the higher voltage sends a charging current to the lower voltage until it’s equal. If this happens, you and your device will be severely harmed. If you want to learn more about connecting two batteries with different voltages in parallel and its possible harmful effects, continue reading.

Can you connect different amp-hour batteries in parallel?

Many have thought, what happens if you put two batteries in parallel? You should not connect two batteries of different voltages in parallel as this would damage them by reducing the battery’s charge to a lower voltage. If they are rechargeable, the impact might be less since the battery with a lower capacity will stop accepting a charge beyond a certain extent even though the current will keep flowing.

If the difference in voltage between the two batteries is minor, the current will pass from the higher to the lower voltage, leading to overheating and stopping the current flow. But, if the voltage difference is higher, the current flow causes the battery to leak, discharge, or even explode, leading to a hazardous situation.

Can You Connect Batteries in Parallel from Different Brands?

Ideally, you should not connect batteries in parallel from different brands, even if they have the same voltage or if the voltage difference is only 0.5 volts since it would cause the current to flow from a higher to a lower voltage.

Although this might not cause significant damage, like leakages or explosions, it might still cause the battery to overheat, leading to minor damage in terms of how long the battery can function well.

Can You Connect Discharged and Charged Batteries in Parallel?

You cannot connect discharged and charged batteries in parallel. With a higher voltage capacity, the current will flow from the charged to the discharged battery to bring the batteries to a balance.

However, instead of creating a balance, the charged and discharged batteries will only take more heat than they can handle, causing them to leak or explode.

Can You Connect New and Old Batteries?

Connecting new and old batteries will not be efficient. Since batteries tend to lose charge as time passes, the old batteries will reduce capacity and cannot create a balance with the new batteries.

Although the consequent impact of connecting new and old batteries in parallel might not be extreme, it could still lead to a lower output than required for your device. Additionally, the new battery’s lifespan is quickly reduced when combined with the older battery.

Things to consider

To ensure a balance between the batteries when they are connected in parallel, consider the following:

  • The batteries should belong to a single brand to maintain and match the voltage between both batteries.
  • They should have the exact manufacturing and expiry dates such that neither of them has lost any charge.
  • Both the batteries should carry the same charge so that there are no issues once you connect them in parallel.
  • You should ensure that you connect the batteries to their respective terminals to work well.
  • If you have any further doubts about connecting the two batteries, you can refer to user manuals to get a basic idea about the process and precautions.

Frequently Asked Questions

Can you connect batteries in parallel with different amp hours?

Yes, you can still connect them even if they have different amp hours. This won’t cause any problems with the batteries and will continue to provide efficiency. However, you should ensure that the voltage of both batteries is the same, as this could otherwise lead to issues like overheating, leakage, or explosions.

Can I mix batteries with different mAh?

You should not mix batteries with different mAh (milliamp hours) as this could result in one battery having a higher capacity than the other, causing a lack of balance and fluctuation in current.

This can further lead to the batteries losing out on their cells and capacities at different rates, leading to issues like overheating or over-discharging and reducing your battery’s lifespan.

What is the right way to connect batteries in parallel?

First, you must maintain the same voltage while trying to increase the amp-hour capacity. Then, you should use a jumper cable to attach the battery’s positive and negative terminals.

Is there a difference between connecting batteries in parallel and series?

Connecting a battery in parallel maintains a constant voltage while altering the amp hours. In contrast, connecting batteries in series involves keeping the same amp-hours while changing the voltage.

Remember, the positive and negative terminals must be connected when connecting in parallel. However, connecting batteries in series involves connecting the battery’s negative terminal with the positive one through a jumper cable.

What uses do batteries connected in parallel serve?

Connecting two batteries in parallel helps power the cells and batteries of multiple devices. A parallel circuit can be advantageous as it can supply power across various devices without reducing the voltage.

Will I have to replace the damaged battery?

It’s essential to replace the damaged battery to avoid problems like overheating, explosions, or leakage. Also, if you use two batteries of different voltages in parallel, you need to replace the battery with a lower and higher voltage.

Can overheated batteries damage the appliance or device?

Yes, it will damage your device or appliance because leakages or sparks burn its components and release harmful gases that can cause explosions, fires, or injury.


Remember not to connect batteries of various voltages or brands in parallel to ensure your safety. This will prevent the current from flowing from a higher voltage to a lower voltage, resulting in leakage, sparks, or explosions. Therefore, it is advisable to connect batteries according to the instructions in the handbook, including the amount of charge, appropriate terminals, and suitable brands.

About the author, Phil Borges

Phil Borges is a battery aficionado. He's written extensively about batteries, and he loves nothing more than discussing the latest innovations in the industry. He has a deep understanding of how batteries work, and he's always on the lookout for new ways to improve their performance.