Simple Guidelines when Buying a Charger
1. Choose the correct charger by battery chemistry like lead-acid, li-ion, LiFePO4 etc. Most chargers serve one chemistry only. Make sure that the battery voltage agrees with the charger. Do not charge if different. A lead acid battery charger does not suit for a lithium battery (Li-ion, LiFePO4, LiMnO2 etc.) and a lithium battery charger does not suit for a lead acid battery (AGM, GEL etc.).
2. The Ah (battery capacity) rating of a battery can be marginally different than specified. Charging a larger battery will take a bit longer than a smaller pack and vice versa. Do not charge if the Ah rating deviates too much (more than 25 percent).
3. A lead acid charger should have a float charge when fully saturated; a nickel-based charger must switch to trickle charge when full. Lithium battery cannot absorb overcharge and no need of trickle or floating charge. Trickle charge and float charges compensate for the losses incurred by self-discharge.
4. A high-wattage charger shortens the charge time but there are limitations as to how fast a battery can be charged. For lead acid battery, charging time often 8-12 hours. For lithium battery, charging time is often 3-4 hours. For example, if your lead acid battery 48V100Ah, then you need a 48V 8-12A lead acid battery charger. If your lithium battery is 48V100Ah, you need a 48V 25-30A lithium battery charger.