Choice of electric wheelchair - dual battery vs single battery
Choosing an Electric Wheelchair - Dual Battery vs Single Battery
It is feasible for electric wheelchairs to use two independent batteries (dual batteries), but there are important considerations in practical application; otherwise, the consequences could be serious. This article will explain these points to you.
First - Is one battery or two batteries better? We first need to look at capacity and power.
To calculate battery capacity, we don't look at the number of batteries (one/two). The most practical way is to look at Voltage (V) x Amp-hours (Ah) = Watt-hours (Wh), which refers to power output. A higher Wh number means the battery contains more energy and can travel further.
- The formula for calculating Watt-hours (Wh) is:
- Power Watt-Hours (Wh) = Voltage (V) × Amp-Hours (Ah)
- For example, if a lithium battery is labeled as 24V and 10Ah, its capacity is 240Wh.
- For example, 1 x 24V 20Ah = 480Wh is greater than > 2 x 24V 6Ah = 288Wh
Advantages of a single large battery:
Advantages of a dual-battery design:
Dual batteries sound good and theoretically feasible, but what are the actual drawbacks and what should be noted? And why are most products not dual-battery?
If dual batteries are necessary, practical considerations:
First, in practical application, if both batteries are quick-release, both batteries should preferably have the same voltage. Otherwise, there will be a potential difference (i.e., a voltage difference). If both batteries are in the same circuit, current from the higher-voltage battery will flow to the lower-voltage battery, charging it. Because they are in the same circuit, the current will flow directly to the other battery at the fastest rate, generating heat in the process, accelerating battery wear, and shortening the lifespan of both batteries.
Solution: It is best for both batteries to be fully charged before being used together. Ideally, they should be from the same batch and manufacturer. Avoid charging one at a time and then connecting them for simultaneous use.
Second, pay attention to the thickness of the wires and the connection method. Thinner wires have higher resistance. Even if two batteries are from the same production batch, one battery will always age first, which means the potential difference situation mentioned above will occur. Especially when one battery is depleted and the other is still operating, a strong current will be generated, causing the wires to heat up. Thin wires will not be able to handle this, leading to a short circuit and potentially a fire.
Solution: The wires connecting the two batteries must be thick enough, and the wiring should ideally not be exposed or easily damaged.
Examples and Risks of Poor Dual Battery Systems
Recently, a customer sought our help, stating that the wiring of their wheelchair (not our product) short-circuited, showing sparks and burning out. They hoped we could provide repair services. After inspection, it was found that the wheelchair had a dual-battery design. To save cost, the manufacturer used thin wires to connect the batteries, which resulted in the wires burning out, almost causing an accident. Click here for details
FAQ (Frequently Asked Questions)
Q: Will dual batteries last longer than a single battery?
A: You need to look at the individual capacity of each dual battery. For example, two 9Ah batteries compared to one 20Ah battery, the 20Ah single battery will last longer than the two 9Ah dual batteries.
Looking at the batteries above, can you guess which one is the largest and has the most capacity?
To calculate capacity, we don't look at the number of batteries (one/two). The most practical way is to look at Voltage (V) x Amp-hours (Ah), which gives you Watt-hours (Wh), referring to power output. The larger the Wh number, the more energy the battery contains, and the further it can travel.
Note: For electric wheelchair batteries on airplanes, a single battery can only contain a maximum of 300Wh output.
Considerations when choosing:
Q: Will dual batteries last longer than a single battery?
A: You need to look at the individual capacity of each dual battery. For example, two 9Ah batteries compared to one 20Ah battery, the 20Ah single battery will last longer than the two 9A dual batteries.
Q: How thick should the wires be?
A: Since electric wheelchair motors typically have a rated current of 5A, and considering a safety factor, it is recommended to use wires of 2x2.5mm or thicker.
Q: What if I'm using a single large battery but want to increase its capacity?
A: It's best to connect two batteries in parallel. When connecting in parallel, first fully charge both batteries with a charging cable to avoid potential differences.
We would like to remind everyone to carefully choose their wheelchair. Pay extra attention to the wheelchair's hardware, such as wire thickness and connections, or directly opt for a single-battery wheelchair to prevent issues with overly thin wires or improper modifications. If users have any questions regarding electric wheelchairs, please feel free to call us at +852 35680755.
