What are the differences between lithium-ion battery chargers and lead-acid battery chargers? Can they be used together?
Currently, lithium-ion batteries are widely used, not only in industrial products or special equipment, but also in the mass consumer market. For example, lithium-ion batteries for electric bicycles, high-power flashlights, backup power supplies, and other related equipment will inevitably see a large market demand, making this a hot topic for power supply manufacturers.
It's important to note that the charging process for lithium-ion batteries is completely different from that of nickel-cadmium and nickel-metal hydride batteries. It's a complex electrochemical reaction process. Therefore, it's necessary to use a dedicated charger. Even with a dedicated lithium-ion battery charger, it's crucial to differentiate between 4.1V and 4.2V when the battery is fully charged, as the voltage tolerance requirements are very strict (typically 1%). The quality of the charger plays a vital role in the lifespan of the lithium-ion battery. Excessive charging voltage or current can damage or even render the lithium-ion battery unusable.
So, what's the difference between lithium-ion battery chargers and lead-acid chargers? Can I use a lead-acid charger to charge a lithium-ion battery? Will it be effective? The answer is definitely not recommended. Although it doesn't have the function of a pulse charger, theoretically it can charge lithium-ion batteries, but it may still damage them. Although lithium-ion battery protection boards can theoretically protect them during charging or discharging, if the charging protection voltage is frequently triggered, the charger's output voltage is incorrect. After this happens, the battery will always lag behind. Try not to use a charger with too high a protection board. Because the battery is stored in a battery case, you can't normally see the battery's consistent condition. I don't know when, but if its consistency is compromised, the voltage will be slightly higher. The battery will be damaged.
In fact, to overcome the high resistance of lead-acid batteries, the charging voltage of constant current charging is increased by about 5%. This means that if you choose a charger with the same voltage, the voltage will be slightly higher for lithium-ion batteries. Because of the high resistance of lead-acid, the efficiency of constant current charging is affected by the increase in voltage, which can damage lithium-ion batteries. A key reason is that during the charging process of lead-acid batteries, there are two voltage points that change between hydrogen and oxygen. The oxygen voltage change point is 13.8V, and the hydrogen voltage change point is 14.7V. Therefore, the high constant voltage of a lead-acid charger is fixed at 14.7V * number of batteries, and the low constant voltage (floating charging voltage) is fixed at 13.8V * number of batteries.
If the protection voltage of a lithium-ion battery protection board is 4.2V, it is safe to use. Unless otherwise specified, it shouldn't be charged at a constant voltage. However, when the normal protection board starts at 4.25V, plus a +/- 0.035V error, isn't that quite safe? It might not be a big deal for an 18650 battery, but it's hard to say for a large aluminum-cased battery. Many lithium-ion batteries use normal protection boards with a cutoff protection voltage of 4.25V, so this protection might be ineffective in critical moments. Lithium-ion batteries have very low internal resistance; for example, a 13-string lithium-ion battery is 48 volts with a cutoff voltage of 54.6 volts, while the constant current cutoff voltage of a lead-acid battery is higher at 57.9 volts.
Of course, lead-acid batteries can be improved for charging, for example, by removing the low constant-voltage phase circuit and pulse circuit. If you look at the charging curve of lithium, you can see that in the constant current stage, the charge is about 96% of the total capacity; under constant voltage, only 4% of the capacity is filled. If the rotating light is not plugged in, the lithium-ion battery is already 99.5% charged. Therefore, lead-acid chargers use lithium for charging, which is less than the final balance and the 0.5% float charge. High and low constant voltage charging on the leads are both low-critical points; rechargeable lithium only needs to be partially charged. However, lithium-ion batteries will not sulfide, and partial charging does not affect their lifespan and can even extend their lifespan.
