Charging Voltages by Model: Why 12V, 24V and 48V Packs Differ
A common mistake when charging a LiFePO4 pack is to assume that the charge voltage is the same for every pack at a given system voltage, or that a charger set for one model will suit another model at the same voltage. This article explains why charging voltages differ by model, using the listed figures on this site as examples. It does not give a single charge setting for the whole range, because the listed charge voltages and currents differ by model.
Nominal voltage is not charge voltage
Nominal voltage is the working voltage used to describe a pack, while charge voltage is the higher voltage applied during charging. For example, a pack described as 12.8 V nominal, a pack described as 25.6 V nominal and a pack described as 51.2 V nominal all have charge voltages above their nominal voltages, but the exact charge voltage depends on the model and on the cell arrangement. A buyer who confuses nominal voltage with charge voltage may set a charger too low, leaving capacity unused, or too high, which the management system should prevent but which should not be relied upon as the normal charging method. The listed 48V packs on this site give a charge voltage of 58.4 V, plus or minus 0.2 V, for both the 50Ah and the 100Ah models.
Nominal voltage is the working voltage used to describe a pack, while charge voltage and cut-off voltage are separate limits. A 12.8 V pack, a 25.6 V pack and a 51.2 V pack belong to different systems and are not interchangeable, even when their capacities look similar. Buyers should confirm the system voltage, the charge voltage and the cut-off voltage for the exact model, and should check that the existing charger or inverter settings match those limits before ordering.
Charge current differs by model at the same voltage
Charge current also differs by model at the same voltage, and it matters as much as charge voltage. For example, the listed 12V 12Ah pack gives a charge current of 6 A with a maximum of 12 A, while the listed 12V 36Ah pack gives a charge current of 15 A with a maximum of 30 A, and the listed 48V 100Ah pack gives a charge current of 50 A with a maximum of 100 A. Those figures are not interchangeable, and a charger set for one model should not be assumed to suit another model at the same voltage, even when the charge voltage happens to match. The reason charge current differs is that the management system, the terminals and the cell arrangement for each model are rated for different currents.
A battery management system watches the cells in a pack and disconnects the pack when a limit is crossed. The exact limits depend on the model, so buyers should check the protection list for the model they are considering rather than assuming every pack in a range shares the same list. In the models listed on this site, protection typically covers over-charge, over-discharge, over-current, over-temperature and short circuit, with cell balancing on some models only. Where a model page does not list balancing, it is not claimed for that model.
Cut-off voltage and the charging window
The charging window for a pack is bounded by its charge voltage at the top and its cut-off voltage at the bottom for discharge. The cut-off voltage is the voltage at which discharge should stop, and it is listed per model - for example 10.0 V for the listed 12V packs, 20.0 V for the listed 24V packs, and 40.0 V for the listed 48V packs. Those figures should be checked against the inverter or load settings, because a system that discharges a pack below its cut-off voltage is using the pack outside its stated limits. The width of the charging window also affects how state of charge is estimated: LiFePO4 has a relatively flat discharge voltage curve, so voltage alone is a poor indicator of remaining capacity for much of the discharge.
Cycle life is measured under a stated test condition, and the condition matters as much as the headline number. A figure measured at a low discharge rate and a shallow depth of discharge cannot be compared directly with a figure measured at a higher rate and a deeper depth, because the tests differ. A buyer comparing models should therefore read the condition behind each figure, and should ask for any missing detail — rate, depth of discharge, capacity remaining and temperature — before ranking two models against each other.
Temperature and charging voltage
Temperature affects charging in two ways. First, the listed charging range for the models on this site is typically from 0 degrees Celsius upward, and charging below that range should not be attempted without a specific confirmation for the model. Second, the charge voltage itself can be temperature-sensitive in some systems, where a temperature-compensated charger adjusts the voltage with temperature. Whether temperature compensation applies, and how it is set, depends on the charger and the model, and it should be confirmed for the specific installation rather than assumed from a general description.
Temperature is a check that is often overlooked when a pack is chosen by capacity alone. The listed temperature ranges on each product page state the charging, discharging and storage ranges for that model, and those ranges should be checked against the installation location and the climate. Charging below the listed charging range should not be attempted without a specific confirmation for the model, because charging in cold conditions can damage the cells. If charging in cold conditions is a regular requirement, the enquiry should state the lowest charging temperature.
A model-by-model charging checklist
Before charging a new pack, check three things for the exact model: the charge voltage, the charge current and its maximum, and the charging temperature range. Then check that the charger or inverter settings match those three values, and that the cut-off voltage is set correctly for discharge. If any of those values is missing from the product page for the model, ask for it in the enquiry rather than borrowing it from another model. That checklist is short, but it prevents the most common charging mistakes, which come from assuming that a setting for one model applies to another model at the same voltage.
For a business enquiry, the most useful details are the system voltage, the capacity, the expected discharge current, the operating temperature range and the physical space available. A pack that fits on paper can still fail in use if the discharge current, the temperature range or the terminal layout does not match the application. That is why this site asks buyers to confirm specifications per model, rather than selecting from a generic table.
Enquiry checklist
Before sending an enquiry, note the voltage, capacity, quantity, application and any required certification document. State whether the pack will be used indoors or outdoors, and whether a display or a particular terminal type is needed. Minimum order quantity and lead time are unavailable on this site and are confirmed per model in the enquiry. Quotations are confirmed per order.
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Frequently asked questions
How do I get a quotation?
Send an enquiry with the voltage, capacity and quantity you need, plus the application. Quotations are confirmed per order, and specifications are confirmed per model before payment. This site does not list fixed selling figures.
What certification documents can you provide?
ISO 9001 is stated by the company. Certificates are available upon request. If a buyer needs a certificate for a specific model, ask for it in the enquiry and name the model, so the correct document can be checked.
Are the specifications on this page valid for every model?
No. Specifications are shown per model and must not be read across the whole range. Where a value is not listed for a model, the page says to confirm per model rather than filling in a generic figure.