mAh worked fine for consumer electronics. In industrial motive power procurement, it's where most specification problems start. The formula is middle school math: Wh = mAh × V ÷ 1000. The issue is what V actually means when different suppliers are using different numbers, and those numbers can diverge by over 20%.
Had a cold storage client last year bring us three quotes to verify. Same nominal spec: 48V 460Ah forklift batteries. Prices ranged from $4,200 to $6,800. He wanted to know if the expensive one was ripping him off.
I told him to request 0.5C discharge curves from all three and check the voltage reading at 50% SOC. One showed 51.2V, one showed 48V, the third couldn't produce the data at all. The first two, both claiming 460Ah, differed by nearly 1,500Wh when you actually calculated it. The $4,200 quote had the highest cost per actual energy delivered.
What 460Ah Actually Means on a Quote
LiFePO4 cell working voltage runs roughly 2.5V to 3.65V. A 48V system needs 15 cells in series, so actual pack voltage swings from 37.5V up to 54.75V. Same battery, same Ah rating, completely different Wh depending on where you measure.
| SOC State | System Voltage | 460Ah Converted to Wh |
|---|---|---|
| Full charge | 54.75V | 25,185 |
| Mid-point | 51.2V | 23,552 |
| Nominal | 48V | 22,080 |
| Near cutoff | 40V | 18,400 |
Some suppliers quote at nominal voltage, some at mid-point, some just write down an Ah number and let you guess. Polinovel specs use mid-point voltage consistently. The FL51460 measures around 23,500Wh. Compare that against a competitor using 48V nominal math showing 22,080Wh, we look more expensive. Actual energy delivered might be identical or we might even be cheaper.
How to verify: Get discharge curve raw data from your suppliers. Read voltage at 50% SOC. Convert all quotes to the same voltage baseline before comparing unit price. A supplier who can't produce curves either hasn't tested or didn't like the results. Either way, worth considering what that means for the partnership.
Purchase Price Is Just the Tip
Lead-acid procurement habits die hard. Look at initial unit cost and cycle count, make a spreadsheet, pick the lowest number. With lithium, that calculation misses too much.
We've tracked actual spending before and after switchovers at several client sites. One two-shift warehouse running 20 reach trucks on lead-acid. Hidden costs they never realized they were carrying:
Watering maintenance.
15-20 minutes per battery per week. 40 batteries total. Monthly labor cost over $800 just on that. Buried in general warehouse overhead, never itemized separately.
Swap time.
Lead-acid can't make a full shift, so mid-shift battery changes. Each swap runs 30+ minutes. Two shifts per day means two swaps. One truck, one hour daily just changing batteries. Twenty trucks, twenty man-hours. Multiply by 22 working days and your labor rate.
The Year 3 cliff.
Lead-acid cycled at 50% DoD starts falling off a cliff around year three. Procurement compared "cycle life" numbers at purchase. Supplier said 2,000 cycles. Real-world got maybe 1,400 before replacement.
None of this shows up on the quote.
Polinovel FL51420 reach truck batteries support opportunity charging. Twenty minutes at lunch adds enough juice to finish the day. Swap process eliminated. Watering doesn't exist. Initial acquisition cost is higher than lead-acid though. Whether it pays back depends on your specific operating parameters.
When Does It Actually Pay Back
The 14-18 month industry number means nothing because every operation is different.
Calculate yours:
(Monthly watering labor hours × hourly rate) + (Swap events × time per swap × hourly rate) + (Monthly kWh consumed × efficiency gap × electricity rate) = Monthly hidden cost
LFP acquisition premium ÷ Monthly hidden cost = Payback month
Concrete scenario: 20 trucks, two shifts, $28/hour labor, $0.11/kWh electricity. Based on client data we've tracked, monthly hidden cost runs $4,200 to $5,800 depending on swap frequency and charging patterns.
Per-battery premium of $3,500 over mid-tier lead-acid, times 20 units, equals $70,000 incremental investment. Divided by $5,000 monthly savings, payback hits at month 14. Higher labor rate, higher electricity price, more frequent swaps, you might see month 12. Lower numbers push it out further.
Only you know your actual numbers. Only you can run this calculation for your operation.
Bigger Capacity Isn't Insurance, It's a Trap
Lead-acid logic says buy the biggest battery that fits. Leave room for margin. That thinking backfires with LFP.
Lithium iron phosphate ages faster when sitting at high state of charge. You spec 40% oversized, daily operation only uses 60% of capacity, battery floats in high-voltage territory constantly. Year one looks fine. Year two, degradation accelerates. Year three, it falls apart. Dies earlier than a correctly sized battery would have.
Proper sizing works backward from actual energy consumption, applies temperature correction, C-rate correction, aging margin, arrives at target capacity. Cold storage correction factors differ completely from ambient warehouse. High-cycle AGV applications use another set of calculations entirely.
The details here involve Polinovel internal test data and experience curves that don't fit in a public article. If you've got a specific project under evaluation, send over the operating parameters and we'll produce a targeted sizing recommendation.
What Your Supplier's Documentation Should Include
Discharge curves. Minimum three: 0.2C, 0.5C, 1C. Shows how voltage behaves under different load rates.
Temperature performance data. Capacity retention from -20°C to +60°C. Running cold storage without checking this chart carefully means a rough winter ahead.
Cycle life test reports. Must state test conditions: temperature, DoD percentage, charge/discharge rate. Some suppliers claim 4,000 cycles but test conditions were 25°C, 50% DoD, 0.3C. Nothing like your actual operating environment.
UN38.3 transport certification. Baseline requirement.
Polinovel provides all of the above as standard. If suppliers you're currently comparing can't produce equivalent documentation, consider what that gap implies.
Next Step
Polinovel has been building industrial motive power batteries since 2012. Forklifts, AGVs, golf carts, airport ground support equipment. We know where lithium advantages are clear and where the switch might not be worth it.
If you have a specific project under evaluation, send over your shift schedule, current swap frequency, maintenance hour records if you've got them. We'll produce a sizing analysis with assumptions and calculations laid out clearly. You can verify the numbers yourself.
Analysis typically takes about a week. Whether or not you end up choosing our product, you'll have a decision framework you can defend to finance and operations.
