Battery Pack Specification Sheet: How to Read One

Two suppliers can offer a “48 V 30 Ah LiFePO4 pack” and deliver products that are not interchangeable. One may be a 15-series build, the other 16. One may rate its peak current for thirty seconds, the other for three. One may quote 2,000 cycles to 70 percent capacity at 0.5C and 25 °C, the other 2,000 cycles at 1C in an undefined environment. The spec sheet is where those differences live, and it is usually attached to the quotation as a PDF nobody reads closely.

Read it properly and you can compare offers on equal terms, and hold the supplier to numbers later. This walkthrough covers the lines that matter for finished packs and for packs built around bought-in cells.

Key takeaways

A “48V 30Ah LiFePO4 pack” can be a 15-series build at 48.0 V nominal or a 16-series build at 51.2 V. Always ask for charge voltage, discharge cut-off and the configuration (for example 16S2P).
Amp-hours without a discharge rate is a hint, not a capacity. A complete line reads “30 Ah at 0.2C, 25 °C, to the BMS cut-off”.
“2,000 cycles” is not a specification until four conditions are attached: depth of discharge, charge and discharge rate, temperature, and whether end of life means 80% or 70% of original capacity.
Watt-hours are the only fair comparison between packs of different voltages – amp-hours multiplied by nominal voltage.
Three omissions worth challenging: peak current with no duration, “up to” in front of every figure, and no cell model named anywhere on the sheet.

Nominal voltage and the window around it

Nominal voltage is a label, not an operating point. A lithium pack moves through a wide range between full and empty, and the range is what your equipment actually sees.

Nominal voltage — the naming convention. A lithium iron phosphate pack called “48 V” may be a 15-series build at 48.0 V nominal, or a 16-series build at 51.2 V that the industry also sells as a 48 V system. They are not interchangeable: chargers, controller limits and BMS cut-offs all differ.
Charge voltage and end-of-discharge voltage — the real boundaries. These decide whether your existing charger works and whether the controller browns out before the pack is empty.
Cell count and configuration — series and parallel arrangement, written as something like 16S2P. It tells you the cell format, how many cells are in the pack, and what a single failed cell does to the whole.

If the spec sheet gives only a nominal voltage, ask for charge voltage, discharge cut-off and the configuration. Those three numbers are what let you check compatibility, and they are the ones suppliers most often leave off a summary sheet.

Capacity, energy and what the number assumes

Amp-hours without a discharge rate is not a capacity, it is a hint. Capacity depends on how fast you discharge and how cold the pack is, so a complete line reads like “30 Ah at 0.2C, 25 °C, to the BMS cut-off”.

Nominal capacity (Ah) — the headline figure, usually measured at a low rate in a warm room. Real-world capacity at 1C in winter will be lower.
Energy (Wh) — amp-hours multiplied by nominal voltage. This is the number that determines runtime and range, and the one to use when comparing packs of different voltages. Our guide to sizing a battery pack works entirely in watt-hours for this reason.
Usable capacity — what the BMS lets you access before it cuts off. If the sheet quotes cell capacity but the BMS reserves margin, usable energy is less than cells × voltage suggests. Ask directly.

Current ratings: continuous, peak, and for how long

This is the most frequently overstated line on a sheet. Peak current without a duration is meaningless — a pack can usually deliver far more than its continuous rating for a second or two, and the question is what it can sustain and for how long before the BMS trips or something gets hot.

Ask for three numbers: continuous current the pack can hold indefinitely in your ambient temperature, peak current, and the duration the peak applies. Then compare that against your motor or load, including starting surges and hill climbs. The thresholds themselves live in the BMS, which is why reading BMS specifications belongs alongside this document rather than after it.

Cycle life: the line that hides the most

“2,000 cycles” is not a specification until four conditions are attached to it, and the absence of any one of them can halve the real number.

Depth of discharge — 2,000 cycles at 80 percent DOD and 2,000 cycles at 100 percent DOD are very different products. Shallow cycling is easier on a cell.
Charge and discharge rate — a cycle at 0.5C is not the same wear as a cycle at 2C, and fast charging shortens life more than fast discharging.
Temperature — cycle counts quoted at 25 °C do not survive a pack that lives at 40 °C or charges below freezing.
End-of-life definition — is the count to 80 percent of original capacity, or 70 percent? The difference is a year or more of service.

If a sheet says only “2,000 cycles”, ask for the four conditions in writing. A supplier who can answer immediately has tested; one who cannot is quoting a cell manufacturer’s marketing figure. Cell-level evidence is the same material we describe in our page on capacity grading reports.

Temperature windows: two of them, not one

There are always two ranges, and conflating them is how packs get damaged in the first winter.

Charge temperature — narrower, and usually the binding constraint. Charging a lithium cell below 0 °C can plate lithium metal and permanently damage it, so cold-climate packs need a low-temperature cut-off or a heating function. If your market has real winters, this line decides whether you need one.
Discharge temperature — wider, but capacity drops as it gets colder. Expect noticeably less range in winter even from a healthy pack.
Storage temperature and state of charge — often omitted, and relevant the moment a container sits at a port. Our page on storage and charging safety covers the practical values.

Mechanical, ingress and interface details

These lines decide whether the pack fits and whether the installation passes inspection.

Dimensions and mass — with tolerances. A pack that is five millimetres too tall does not fit the cavity, and mass matters for vehicle classification and for shipping limits covered in our packaging and marking guide.
IP rating — the first digit is dust, the second water. Read the second digit carefully: a rating for splashing is not a rating for immersion, and warranty claims for water ingress turn on this number.
Terminals and connector type — the single most common reason a replacement programme stalls. Specify the connector, the pinout and the wire gauge.
Communication — whether the pack speaks CAN, UART, RS485 or nothing, and what data it exposes. This determines whether your service team can read state of health or only guess.

Certifications and the documents behind them

A logo on a spec sheet is a claim. The document is the evidence. For cross-border shipments the set usually includes the UN38.3 test summary, a safety data sheet, and conformity documents for the destination market; the full list and who prepares what is in our export document checklist. Ask for the test report numbers and the issuing lab rather than the logo alone.

For European and UK customers, end-of-life data is now part of the same conversation — material composition and recycled content are requested at quotation stage. See end-of-life compliance for what to ask for and when.

Warranty: read it against the spec sheet

A warranty that promises capacity retention is only as good as the method used to measure it. If the spec sheet says 80 percent after a year but does not say how capacity is measured, at what rate and temperature, and with which charger, then the warranty is unenforceable in practice. Our battery warranty page shows the format we use; whatever supplier you buy from, make sure the measurement method appears in both documents and matches.

Red flags: omissions that matter

“up to” in front of every figure — range, cycles or current with no test conditions;
peak current with no duration;
cycle life with no depth of discharge, rate or temperature;
capacity in amp-hours with no discharge rate;
mass that looks light for the stated capacity — worth checking against the cell count;
no cell model named, which makes the pack impossible to trace or replace later;
certification logos with no test report number or issuing laboratory.

None of these mean the supplier is dishonest. Most are habits carried over from consumer sales, where nobody asks. Ask anyway — the answers are more useful than the sheet, and a supplier’s response to a technical question tells you how the relationship will go when something fails. If you want to go further, how to audit a battery factory covers what to check on site.

Frequently asked questions

Why do two 48V packs have different chargers?

Because “48 V” is a nominal label, not a fixed voltage. A 15-series lithium iron phosphate pack and a 16-series one have different full-charge voltages and different cut-offs. Always match the charger to the charge voltage and chemistry on the spec sheet, never to the nominal label alone.

What is the difference between Ah and Wh?

Amp-hours measure charge, watt-hours measure energy. Watt-hours are amp-hours multiplied by nominal voltage, and they are the only fair way to compare packs at different voltages. Runtime and range calculations should always start from watt-hours.

How many cycles should I expect from a LiFePO4 pack?

Ask what the number is measured to. Lithium iron phosphate cells commonly reach two thousand or more cycles to 80 percent of original capacity when cycled at moderate rate, partial depth of discharge and room temperature. The same cell cycled hard, deep and hot will not. The conditions matter more than the headline.

What does an IP rating actually tell me?

Two digits. The first is protection against solid objects including dust, the second against water. A higher second digit means better water protection, but the steps are specific: resistance to splashing is not resistance to immersion. Check the rating against how the pack will actually be washed or exposed.

Do I need the cell model on the spec sheet?

Yes. Without it you cannot verify the configuration, check the cell manufacturer’s own data, trace a batch, or source a replacement years later. It is the cheapest line to add and the most valuable one to have.

Should the spec sheet form part of the purchase order?

Yes. Attach it, with the test conditions filled in, and reference it in the PI. A warranty dispute is settled by comparing a measured value against an agreed one, and the agreed value has to exist in writing before the goods ship.

If you are comparing offers, send us the spec sheets you have been given and the duty cycle the pack has to survive. We will tell you which lines we can meet, which we would change, and why — and if a competitor’s number looks better than ours, we will say what conditions are probably missing from it. Reach us on WhatsApp with the application and the target market.