Most electric scooters today run on lithium batteries, which is the same type of battery found in your laptop or cordless tools. Charging a scooter battery usually looks like this: you plug the charger in the power outlet, and then connect it to your scooter. Some scooters even allow for the battery to be taken off and charged separately. But what if your charger is broken, or you don’t have it on your hand, and you need to recharge your battery? Is there a way to charge a battery without a charger?
In theory, any power source can be used to charge a battery, but charging lithium batteries is in fact quite a complex process. A Li-Ion battery requires constant-current/constant-voltage (CC/CV) charging system. The battery is initially charged with a constant current, generally between 0.5C and 1C, where C is the battery capacity in amp-hours. As it is charged, the battery voltage increases until it approaches the full-charge float voltage. The charger then transitions into constant voltage operation as the charge current is slowly reduced.
Without a proper charger it can be very complicated to charge your battery in any alternative way, and you should only do it if you are absolutely know what you are doing.
DISCLAIMER: The following methods of charging a battery are not recommended or long-term solution. They are potentially unsafe, and you should only use them as a last resort if you have no alternative. These examples should only be considered a description and not a set of instructions.
Charging from a power supply
Even though we are scooter enthusiasts, none of us is a Lithium battery expert, so we will quote this answer from Quora by Advaith Madhavan:
Charging a Lithium Ion battery with a lab bench power supply is possible only under very controlled conditions. It is also possible only with a lab bench power supply that has both, constant current and constant voltage feature.
Firstly, get a lab bench power supply with a constant current and a constant voltage option. Set the voltage of the power supply to precisely 4.2V in case of a conventional Lithium Ion battery or precisely 3.6 Volts in case of a LiFePO4 battery. In terms of setting the current, set the current to approximately one-tenth the value of the capacity of the battery in Amp-hours.
Before connecting the leads of the power supply to the battery terminals, measure the voltage of the battery using a multimeter. If the Open Circuit Voltage of the battery is less than 3 Volts, do not attempt to charge the battery as it has a high chance of explosion.
Now connect the leads of the power supply to the battery after confirming that its voltage is above 3 Volts and let it charge. At this setup, the battery will take approximately 10 hours to charge completely from 0% to 100%.
Also note to always keep a tab on the temperature of the battery and stop the charging process immediately even if the battery becomes slightly hot to touch. It is not common for Lithium Ion batteries to heat up during charging. When they heat up, it implies that it is a faulty battery. Do not leave the charging setup unattended and always monitor the setup. Do not always trust the gauges of the power supply and always verify the output voltage with a multimeter. Remember than even if the voltage goes 0.1 Volts above the recommended voltage of 4.2 Volts or 3.6 Volts, it can result in a dangerous explosion.
SAFETY WARNINGS: Do not leave this unattended, and don’t attempt to fully charge the battery. If you charge for too long and your scooter battery gets over nominated voltage, it can catch on fire. Car batteries can produce a mixture of oxygen and hydrogen which can be ignited by a spark, resulting in an explosion spraying sulfuric acid everywhere.
Charging a lithium battery with a car battery
If your car lead-acid battery operates at a higher voltage than the lithium battery, you could use it to charge the lithium battery. You should never do it by directly connecting the SLA battery to the lithium one. You need to have a device that converts the lead-acid output voltage to the required voltage at a safe current for charging your lithium battery.
The best thing you can do is to use a something like this, a travel charger that connects to the car cigarette lighter. These charger come with standard XLR Battery Charger Connectors, used by most electric scooters. It is also possible to connect the red wire for a positive port, and the black wire is for a negative port, but make sure that there is no leak or breaks.
The maximum voltage of a single cell in Li-Ion battery pack is 4.2V, and this must not be exceeded, or the battery will be damaged.
Charging with a Solar Panel
Solar panels are used as one of the sources of energy for modern devices like mobile phones, tablets, and other portable electronic devices. The battery can be charged from standard commercial solar modules, but it definitely requires a solar charge controller.
Generally speaking, charging a scooter battery using solar panels is possible, but not very practical. But, if you’re willing to spend some money and deal with large size panels, it can be done. Most solar panels only put out under 20V, on a very bright sunny day, as they are designed to charge 12V batteries. Panels are connected to a charger controller or MPPT, so you would need to boost the voltage out if your panels are to charge a scooter battery, most electric scooters for adults come with 36V or 48V. These MPPT are relatively expensive. If you have a 48V scooter, you need 52V to charge. Under the best of circumstances to fully recharge a depleted 48V battery under 5-6 hours of full sun, you would need large panels, probably 2 x 100 Watts, 2 x 4 feet each, these are probably in the $250 range. Yes, portable, pliable and folding, are also available but much less efficient, they are really expensive.
This is the problem that potentially could be solved very soon in the future, but for now there are only concepts and projects, like this one.
Can you charge a scooter battery with standard AA batteries?
In theory? Yes. In reality? No. As a rule of thumb, each AA battery has a voltage of 1.5V. Therefore, if your scooter battery has a voltage of 36V, you would need 24 AA batteries. You would need to connect the AA batteries in series to create a single unit, which would be quite a chain. The connection between the batteries must be firm without any gaps. Then, you would have to take the battery out of your scooter, connect the positive end of your looong AA chain to the positive terminal of your device and the negative end to the negative terminal of your Li-ion battery. We would say that this is very complicated process, and in no way practical way to charge a battery in urgent need.
Safety Tips for Charging Lithium Batteries
We have already covered how to safely handle, store and charge batteries in this article, but here are few most important things to remember:
- Keep you battery away from extreme heat, this can cause the battery to overheat and short-circuit, leading to a fire.
- Don’t use the wrong type of charger because it can damage the battery. Always consult the manual and the manufacturer before trying something out.
- For extended storage, discharge a lithium-ion battery to about 40 percent and store it in a cool place.
- When possible avoid frequent full discharges. Instead, charge the battery more often.
- Get a scooter with a higher capacity battery and longer range, it may initially be more expensive, but if you max out your scooter battery too often, you will have to replace it pretty soon.