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Usable-capacity comparison · charger and controller checklist · 36V / 48V / 60V / 72V pathsLead-acid usable 50–60%LiFePO4 DoD 88–90%3,500 cycles−20°C ~ 65°C

Lead-acid to lithium conversion:how much further the same nominal capacity actually goes

The most common mistake in a lead-acid to lithium conversion is treating “same voltage, same amp-hours” as “drop it in and go”. Three things actually differ. Nominal capacity is not usable capacity — lead-acid is discharged to only 50–60% to protect its life, while LiFePO4 is recommended at 88–90% DoD, so the same nominal pack delivers close to twice the usable range. The charger must be replaced, because a lead-acid charger has no CC-CV stage and no BMS handshake. And lead-acid and lithium must never be mixed in one power circuit. This page settles all three, then gives the four voltage paths and the pre-upgrade checklist.

battery_charging_full
Lead-acid usable50 – 60%
battery_full
LiFePO4 DoD88 – 90%
autorenew
Cycle life3,500 cycles
timelapse
Upgrade payback6 – 8 months
calculateRun the payback calculatorswap_horizSee replacement packs

verifiedUsable-capacity figures follow this site’s engineering dataset (the 72V capacity matrix and the TCO model); configuration and warranty are governed by the quotation and the spec sheet shipped with your container.

Capacity-cycling test bench for lead-acid and LiFePO4 packs
scienceUsable capacity, not nominal

Four sources of gain

battery_charging_full50 – 60%Lead-acid usable capacityDeep-discharge duty usually keeps more than 40% in reserve to protect cycle life
battery_full88 – 90%Recommended LiFePO4 DoDUsable capacity sits close to the label — the whole source of the range gain
autorenew3,500 cyclesCycle lifeAgainst 300 – 500 for lead-acid, roughly 7 – 10 times
timelapse6 – 8 monthsUpgrade paybackModelled on daily distance and local fuel and power prices — or run the calculator

Specification notice:The figures above are engineering reference values. They may differ with production batch, configuration and actual duty cycle, and the percentages for life, efficiency, availability and coverage are engineering estimates and bench references. Contact us for the detailed specification sheet.

balanceSame nominal capacity, different usable energy

Same nominal capacity: usable capacity and range gain

The table uses a 100Ah nominal pack at each voltage and separates what is on the label from what can actually be drawn. The range change is the ratio of usable capacities (88–90% against 50–60%), not a marketing figure.

Usable vs nominal
Platform / nominal capacityLead-acid usableLithium usableUsable range changeCycle lifeNominal energy
36V 100Ah (3×12V lead-acid / 12S lithium)50 – 60Ah88 – 90AhAbout +47% ~ +80%300 – 500 → 3,500 cycles3.6 kWh → 3.84 kWh
48V 100Ah (4×12V lead-acid / 16S lithium)50 – 60Ah88 – 90AhAbout +47% ~ +80%300 – 500 → 3,500 cycles4.8 kWh → 5.12 kWh
60V 100Ah (5×12V lead-acid / 16S lithium)50 – 60Ah88 – 90AhAbout +25% ~ +54%300 – 500 → 3,500 cycles6.0 kWh → 5.12 kWh
72V 100Ah (6×12V lead-acid / 24S lithium)50 – 60Ah88 – 90AhAbout +47% ~ +80%300 – 500 → 3,500 cycles7.2 kWh → 7.68 kWh

Two details buyers miss. First, LiFePO4 has a higher nominal voltage (76.8V at 24S against 72V for six lead-acid blocks), so the same 100Ah label carries about 6% more nominal energy. Second, usable capacity holds across −20°C to 65°C, whereas lead-acid loses usable capacity noticeably below 0°C. The 60V row is the exception: five lead-acid blocks are nominally 60V, above the 16S LiFePO4 51.2V, so nominal energy actually falls (6.0 → 5.12 kWh) even though usable capacity and range rise — one more reason a 60V frame needs its controller cut-off reflashed. The range change is converted from equal duty-cycle consumption; real mileage moves with payload, gradient, tyre pressure and riding style — run the calculator on your own daily distance.

Specification notice:The figures above are engineering reference values. They may differ with production batch, configuration and actual duty cycle, and the percentages for life, efficiency, availability and coverage are engineering estimates and bench references. Contact us for the detailed specification sheet.

grid_onVoltage by voltage

How each voltage converts: 36V, 48V, 60V and 72V

Lead-acid is strung from 12V blocks, so the four common banks are three, four, five or six blocks. Match full-charge voltage to a LiFePO4 series count first, then decide which components have to move with it.

Voltage matching
Original lead-acid bankFull-charge voltageLiFePO4 series countNominal / full chargeWhat else must be changed
36V · 3×12V in seriesAbout 42 – 44V12S38.4V / 43.8VCharger and instrument re-specced at 12S; controller under-voltage and over-voltage cut-offs reset; DC-DC matched to the low-voltage platform
48V · 4×12V in seriesAbout 56 – 58V16S51.2V / 58.4VFull-charge voltage overlaps 16S closely, making this the best-matched conversion; the charger must change, and most controllers survive if the current limit is verified
60V · 5×12V in seriesAbout 70 – 73V16S51.2V / 58.4V16S charges to only 58.4V, below the original 5×12V lead-acid bank; most controllers survive (≥75V rating) but the low-voltage cut-off must be reflashed (about 52.5V on lead-acid to about 44.0V for 16S), and the charger must change
72V · 6×12V in seriesAbout 84 – 88V24S76.8V / 87.6VController must be automotive grade at ≥100 – 120V (87.6V full charge plus back-EMF surge); insulation rules tighten; at 150Ah the pack drops from about 240kg to about 81kg

The full-charge column is a nominal band — measure your own charger curve before cutting anything. Series counts are derived from LiFePO4 3.2V nominal / 3.65V full charge and match this site’s platform table (48V=16S, 60V=16S, 72V=24S, where 48V and 60V are the same 16S pack); for the low-voltage case see 24V / 36V lithium batteries.

Specification notice:The figures above are engineering reference values. They may differ with production batch, configuration and actual duty cycle, and the percentages for life, efficiency, availability and coverage are engineering estimates and bench references. Contact us for the detailed specification sheet.

Battery diagnostics workbench checking controller, charger and pack voltage and polarity
fact_checkCharger and controller compatibility

The compatibility checklist before you convert

Failed conversions almost always share one cause: only the battery was changed. A lead-acid system and a LiFePO4 system differ in charging protocol, voltage margin, state-of-charge logic and mounting. Work the seven items below in order — if any one fails, do not energise the vehicle.

  • The charger is the one part with no compromise: a lead-acid constant-voltage or three-stage charger has no CC-CV stage and no BMS handshake, so it drives the pack straight into protection or, worse, into overcharge.
  • Voltage margin beats nominal voltage: a 72V platform reaches 87.6V at full charge, so controller and DC-DC ratings must absorb the back-EMF surge rather than merely matching a 72V label.
  • Align the current limit with what the pack can deliver: 150 – 250A continuous at platform level with 3C peaks for short climbs. A limit above the pack rating pushes internal-resistance heating into protection, or worse.
  • The instrument must be re-specced or re-calibrated: a lead-acid gauge estimates charge linearly from voltage, so SOC becomes visibly wrong and shift distance cannot be managed.
bolt150 – 250AContinuous discharge
autorenew3,500 cyclesCycle life
fact_checkSeven checks before the conversion
  • Charger: replace with a CC-CV charger at the correct series count (10 – 40A, BMS handshake). A lead-acid charger must never be reused
  • Controller MOSFET rating: ≥75V on 48V; 85 – 100V on 60V; ≥100 – 120V automotive grade on 72V
  • Controller current limit: matched to what the pack can deliver (150 – 250A at platform level) — never raise the limit to chase torque
  • Terminals and polarity: lead-acid uses bolt terminals, lithium uses keyed high-current connectors. Reverse polarity destroys the BMS, so verify with a meter before connecting
  • Instrument and DC-DC: fit a cluster that talks to the BMS, or re-calibrate SOC against it. Spec the DC-DC for the new platform — taking 12V straight off the bus burns lamps and gauges
  • Battery bay and mounting: lithium has a different envelope, so check length, width and height and mount it anti-vibration (verified to 3G), with a stamped bracket if needed
  • Thermal policy: −20°C to 65°C window, current-limited charging in the cold and automatic derating in heat. Keep charging bays away from the exhaust path
warningSafety: can they be mixed?

Can lead-acid and lithium be mixed? No — three cases explained

block

Paralleled in one circuit

Charge curves and internal resistance differ: on charge the lead-acid reaches absorption voltage while the lithium pack is still filling, and the lithium BMS cannot protect the lead-acid end from overcharge. On discharge the lithium pack is dragged into low-voltage protection and the two sets rob each other. Never mix them in one power circuit.

link_off

Series-stacked to raise total voltage

Stringing lead-acid blocks into a lithium pack makes the lead-acid reach cut-off first, over-discharges the lithium and removes unified per-cell protection and balancing from the whole string. Not a usable arrangement.

electrical_services

Separate compartments (lithium for traction, lead-acid for 12V)

Technically workable, but it must be electrically isolated: run the 12V rail from an independent DC-DC off the traction pack, or from its own 12V source. Never tap the middle of the traction pack, because that section will drift out of balance permanently.

checklist

The correct order

Remove the lead-acid bank first, then fit the lithium pack. Change the charger and the instrument at the same time, re-calibrate SOC display and the under/over-voltage cut-offs once, then run a 5km loaded road test.

helpUpgrade FAQ

Lead-acid to lithium upgrade questions

Can lead-acid and lithium batteries be mixed or paralleled?expand_more
No. Paralleled, the different charge curves overcharge the lead-acid side and leave the lithium pack short of full, while on discharge the lithium pack is pulled into low-voltage protection. Series-stacked, the lead-acid reaches cut-off first and over-discharges the lithium, and the string loses unified protection. They can coexist only in separate, electrically isolated circuits — for example a 12V auxiliary rail on its own supply. Never tap the middle of the traction pack.
How much range do I gain at the same capacity?expand_more
Lead-acid is discharged to only 50–60% to protect its life, while LiFePO4 is recommended at 88–90% DoD, so usable capacity is 1.5 – 1.8 times higher and the range change is about +47% to +80%. On top of that, a 24S lithium pack is nominally 76.8V against 72V for 6×12V lead-acid, so the same 100Ah label carries roughly 6% more nominal energy.
Can I replace only the battery and keep the vehicle?expand_more
Yes, with conditions: the frame must be sound, the pack must fit the bay, and the controller voltage rating and current limit must cover the new platform. In a battery-only swap the charger must still be replaced, and the instrument should be changed to a BMS-aware version. To see whether it pays, enter conversion cost, daily distance, fuel price and power price in the conversion payback calculator and read the payback in months.
How does each voltage convert — 36V, 48V, 60V, 72V?expand_more
Match the series count from the lead-acid bank: 36V (3×12V) to 12S, 48V (4×12V) to 16S, 60V (5×12V) also to 16S, and 72V (6×12V) to 24S. Note that 48V and 60V use the same 16S pack — no higher 20-cell variant is offered here, and 60V is simply the label used when replacing a 5×12V frame. The 48V bank (about 56–58V charged) overlaps 16S at 58.4V most closely and is the best-matched conversion. The 60V bank charges to about 70–73V, above the 16S 58.4V, so the controller low-voltage cut-off must be reflashed (about 52.5V on lead-acid to about 44.0V for 16S). The 72V bank needs the controller rating and high-voltage insulation upgraded too, so it changes the most.
Why must the charger be replaced?expand_more
A lead-acid charger follows a constant-voltage or three-stage curve with no CC-CV stage and no BMS handshake, so it drives LiFePO4 into protection or overcharge. Fit a CC-CV charger of 10 – 40A at the correct series count and confirm the charge voltage and full-charge cut-off match the pack.
Do I need a new controller?expand_more
Most controllers can stay, but two checks decide it: the MOSFET rating (≥75V at 48V, 85 – 100V at 60V, ≥100 – 120V automotive grade at 72V) and whether the current limit matches what the pack can deliver (150 – 250A at platform level). If both hold, keep it — otherwise a new controller costs far less than a burnt one and a batch of rework.
The state of charge reads wrong after the swap. What now?expand_more
A lead-acid gauge estimates charge linearly from voltage, and LiFePO4 has a very flat discharge plateau, so it shows “drops fast when full, barely moves at the end”. Fix it by fitting a cluster that communicates with the BMS, or by re-calibrating the display curve against BMS SOC during commissioning. Commercial vehicles should go straight to an automotive cluster, because only accurate SOC supports shift planning.
How long does the upgrade take to build and ship?expand_more
Samples take 3 – 5 days; a 20GP holds about 180 packs and a 40HQ 320+. Transport ships with UN38.3, MSDS and a dangerous-goods packing certificate (Class 9) in the container, and market access depends on the destination (for example South Africa NRCS LOA, Nigeria SONCAP, Kenya PVoC / KEBS). We load from Yantian / Shekou in Shenzhen or Nansha in Guangzhou and can book against your nearest port.
request_quoteUpgrade enquiry

Send your lead-acid configuration and we will size the upgrade

Tell us the original voltage and lead-acid capacity, battery bay length, width and height, controller model, daily distance and destination port. We will return the matching LiFePO4 series count and capacity, the parts that must change with it, FOB / CIF pricing and the shipping document list.

  • Upgrade configuration advice and pricing within 24 hours on working days
  • Sample packs available to prove bay dimensions and connectors before you commit to a container
  • Vehicle parameters and market-access documents are strictly confidential; NDA available first
mailExport desk: sales@erickshawtrikebattery.com
callDirect / WhatsApp: +86 13922702227
location_onEBattery Office, Room 310I, Huilange BLDG, No. 273, Huangpu Blvd W, Tianhe District, Guangzhou 510620, Guangdong, China
scheduleReply within 24 hours with upgrade advicescienceSized on usable capacity and duty cycle, not on nominal labelsverified_user5-year / 3,500-cycle warranty

Specification notice:The figures above are engineering reference values. They may differ with production batch, configuration and actual duty cycle, and the percentages for life, efficiency, availability and coverage are engineering estimates and bench references. Contact us for the detailed specification sheet.

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The vehicle, controller and conversion details you submit are used only for this upgrade assessment and remain strictly confidential.