Connecting multiple lithium batteries in series or parallel is a very complicated issue, which is considered a difficult problem internationally. This is because it is difficult to manufacture each lithium battery with exactly the same internal parameters. These differences will continue to accumulate after multiple charges and discharges. Not only would this significantly reduce battery performance, but there is also a risk of explosion! Currently, lithium batteries used in electrical devices such as cameras and others only use two batteries and must have a dedicated protection circuit! Not to mention you have to stack it to 60 volts! The reason why new energy vehicles are not developing rapidly is because of this problem with batteries. So I warn you not to connect in this way. Of course there may be another problemioned in the second stage, that is, even if the voltage is sufficient, whether the current is sufficient still needs to be calculated separately. Because series current is only equivalent to the current capacity of a current.
Cell phone chargers generally refer to regulated 5V power supplies, not chargers. They cannot directly charge lead-acid batteries. A current limiting resistor must be added and a 5V supply is used to charge the lead. batteries.
The full voltage of a 4V lead-acid battery is 4.8V. When using the charging base, it is generally powered by a 6V power supply and the voltage 5 V power supply is not sufficient.
The mobile phone charger uses a 5V regulated power supply, and the output is connected to a 4V battery. If the voltage is lowered, the regulated power supply will behas overcharged and will damage the cell phone charger.