![]() Just another reason that a standard lead acid charger doesn’t suit lithium batteries. Lithium charge algorithms will normally set a return to bulk voltage of 13.1-13.2V. At this voltage the lithium battery will have been depleted to approx 10-15% state of charge. This voltage for a lithium battery is way too low. The “return to bulk” voltage setting in lead acid chargers is normally 12.5-12.7v. Once the voltage reaches the “return to bulk” voltage, the charger will then start a new charge cycle and start re-charging the battery. If the loads increase past the charger’s maximum output in float, then the battery voltage will start to reduce. ![]() Once the charger is in Float, it will maintain the battery at a pre-set voltage (normally between 13.3-13.8v subject to the battery type) and also support any loads running at the time. A 100% full lead acid battery’s voltage is approx 12.7v. The other function that lead acid chargers have is a “return to bulk” voltage. Applying an equalization charge of 15v+ to a lithium battery will damage the cells beyond repair. Lithium batteries do not require any form of equalization. On some chargers this mode may be automatic and can’t be turned off. Most, if not all, lead acid chargers have an equalization mode. ![]() This generally happens if the charger is undersized for the battery bank or there are loads running on the system and not allowing the charger to reduce the current below the transition point. The absorption stage is also time based, if the charger is still in its absorption phase after 4 hours, the charger will automatically transition to the float stage. Once the current reduces to approx ≤10 % of the chargers total output, it will then move to the float state. In this charge phase the charger will hold the maximum voltage for the chosen battery and charge the battery with reduced current as the batteries internal resistance can’t accept the charge current at maximum output. This system allows fast charging without the risk of over-charging and is suitable for Li-ion and other battery types. The current then reduces as the battery becomes fully charged. The charger limits the amount of current to a pre-set level until the battery reaches a pre-set voltage level. Lithium chargers are based on a CV/CC (constant voltage/constant current) charge algorithm. LiFePO4 is a “clean” system and only takes what it can absorb. The so-called ‘miracle charger’ that promises to prolong battery life and gain extra capacity with pulses and other gimmicks simply does not exist. Whilst lead acid offers some flexibility in terms of voltage cut off, manufacturers of LiFePO4 cells are very strict on the correct setting because Li-ion cannot accept overcharge. The differences with Li-ion relate to the higher voltage per cell, tighter voltage tolerances and the absence of trickle or float charge at full charge. As you can see, we are playing with a very narrow window of voltage with lithium, less than 0.5V over 80% capacity.Ī Lithium LiFePO4 charger is a voltage-limiting device that has similarities to the lead acid system. A lithium battery at 20% capacity will hold voltage around 13V, its lead acid cousin will be approx 11.8v at the same capacity. Its lead acid cousin will be approx 12.6-12.7v. Lithium batteries are not like lead acid and not all battery chargers are the same.Ī 12v lithium LiFePO4 battery fully charged to 100% will hold voltage around 13.3-13.4v. This is a question we get asked every day by the general public. Can I charge my lithium battery with a lead acid charger?
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