Why Lead-acid Battery Charger and Lithium Battery Charger Can Not be Mixed Use?

Both are 48V electric vehicle batteries, but the Lead-acid Battery Charger and Lithium Battery Charger are not universal. The fact is that the two chargers really cannot be mixed. Generally speaking, under the premise of the same specifications, lithium battery chargers can be used for emergency use of lead-acid batteries.
However, even with the same specifications, lead-acid battery chargers cannot be used to charge lithium batteries.

Now, let's explain the difference between the Lead-acid Battery Charger and Lithium Battery Charger.

Why can't lead-acid battery chargers be used for lithium batteries?

The physique of lead-acid batteries and lithium batteries is different.
The cell voltage of lead-acid battery is 2V (the common specifications of battery packs are 6V, 12V, 24V, 48V, 60V, 72V etc). When fully charged, the lead-acid battery cell voltage is 2.4V.

The cell voltage of the lithium battery is 3.6-3.7V, and the cell voltage of the lithium iron phosphate battery is 3.2V. When fully charged, the voltage of the lithium-ion battery cell is 4.2V, and the cell voltage of the lithium iron phosphate battery is 3.65V.

The program setting and manufacturing process of the charger are different.
The charging voltage of lead-acid battery chargers is usually higher than that of lithium battery chargers. Take a 36V charger as an example, the minimum charging voltage of a lead-acid battery charger is 41.4v-44.0V, and the maximum voltage of a lithium compatible battery charger is generally within 42.5V, and even allows the battery to stop charging at around 41.8V.

Different charging methods.
The charging method of the lead-acid battery charger is the pulsed constant current charging method. And the lead-acid battery charger uses a 2-stage or 3-stage charging mode.
That is to say, after the battery is fully charged (the light turns to green), the charger will continue to supply the lead-acid battery with a small current. In other words, we may feel that, lead-acid batteries more durable the longer they are charged.

The lithium battery pack charger uses the CC/CV constant current to constant voltage method to charge the lithium battery. Charge the lithium battery in an empty state to about 90% using a constant current method, and then switch the charger to a constant voltage mode to fully charge the battery. And when the charger determines that the lithium battery is fully charged, in addition to the indicator light, the lithium ion battery charger will not have current to continue to replenish the battery. Because lithium batteries are not allowed to be overcharged.

What is the impact of mixed use of chargers on the batteries?
Using the lead-acid battery charger to charge the lithium battery will cause the lithium battery to be overcharged and the protection board will enter the protection state.

In the case of the same specification, it is possible to use a lithium battery charger to charge the lead-acid battery, in theory, if it is only an emergency behavior. However, since the voltage of the lithium battery is lower after being fully charged, and there is no small current to supplement the charge, the lead-acid battery will not be fully charged when using a lithium battery charger.

Reasons why lithium battery chargers cannot charge lead-acid batteries.
Although the theory of the charger without the pulse function can charge the lead-acid battery, it may still damage the battery.

The life span of the lead-acid battery will decrease with the number of times of use, and the battery has a memory effect.
Therefore, in our daily life, we will give lead-acid batteries more charging time to ensure that the battery is fully charged before charging. If a lithium battery charger is used to charge a lead-acid battery, the actual single-charge behavior may sacrifice the lead-acid battery's one-cycle life.

In brief, use a lithium battery charger to charge a lead-acid battery, the battery will be undercharged; Use a lead-acid battery charger to charge a lithium battery, the battery will be overcharged.