One thing that confuses a lot of people is chargers. Can you use a lead-acid charger to recharge a lithium battery? The simple answer is “it depends”. Read on to learn when you can, and when you should not.
Batteries come in many different forms. Some batteries are rechargeable, some are not. Even rechargeable batteries have different designs. Lead-acid, Ni-Cad, and Lithium are some of the more common battery types.
How Battery Chargers Work
Lithium batteries tend to have a slightly higher voltage than a lead-acid battery of a similar specification and also tend to have a narrower operating window of voltage when depleted too.
Lithium batteries charge by receiving a steady supply of current until they are fully charged, then the charger cuts off. There is no ‘float’ or ‘trickle charge’ on a lithium battery charger.
Lithium battery chargers work very well for ‘fast charging’. They can supply a rapid charge of current until the battery is almost fully charged, then will reduce the charge sent to the battery as the battery is almost full.
Meanwhile, lead-acid battery chargers work on a three-step process. This process is:
- Bulk
- Absorption
- Float
The bulk phase is fast and will charge the battery to about 80 per cent. At that level of charge, the internal resistance of the battery cannot accept the full rate of charge so the battery charges at a slower rate in the absorption stage.
Then float stage occurs when the current taken by the battery reaches a trickle, or if the battery charger sits in the absorption stage for around four hours.
This can happen for a number of reasons, for example, if the battery charger is underpowered for the battery, or if it is being used to charge too many batteries at the same time.
Some ‘smart’ chargers can test the battery before they start charging, and will then determine what phase to start in. This helps to ensure the fastest rate of charging while still protecting the battery from damage.
Can You Use The ‘Wrong Type’ of Battery Charger
If you use a lithium charger on a lead-acid battery, it will supply a constant voltage to the battery for as long as it is able to.
This could drain the cells below their usual capacity and shorten the life of the battery so it is not a good idea to try.
If you are able to control the voltages and charging times with great precision then you may get away with doing this in an emergency, however, it is best to use the right charger whenever possible.
Using a lithium battery with a lead-acid charger is a different matter.
You can use a lead-acid charger to charge lithium batteries as long as you can set the maximum voltage of the charger and as long as the charger does not have an automatic equalisation mode enabled.
Most modern chargers will let you turn that feature off, and assuming it is turned off, the charger should be safe to use.
If you opt to use a lead-acid charger with the equalisation mode disabled to charge a lithium-ion battery, then you must disconnect the battery as soon as it is fully charged, to avoid damage to the battery.
The ideal option, however, is to use the correct charger type for the battery. There are multi-mode chargers that can be used to charge any kind of battery and that have features to protect the battery and prolong its life.
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