The battery system
Built from batteries you can buy anywhere.
Every StepRanger runs on the same 12V 25Ah sealed lead-acid deep-cycle cell, wired in series. Nothing proprietary. No electronics locking you to us. Rated from 5°F to 122°F, and built to be serviced with a wrench.
All-Terrain Single: 4 × TNE12-25 · 4 in series · ~57 lb of battery
Why sealed lead-acid
The right chemistry for a truck that lives outside.
We chose the battery the way we chose everything else on the truck: by what holds up on a property, not by what reads best on a spec sheet.
A mature traction-class chemistry — the same family that runs forklifts, wheelchairs, and low-speed EVs. No battery-management computer to fail, no firmware, no pairing.
Winters in an unheated shed with the batteries in place. Charge it, flip the breaker off, top it off in spring. Nothing comes indoors.
Bolt-down terminals and standard cells. A pack that sat too long can usually be brought back with an ordinary 12V automotive charger — we'll walk you through it.
No lithium surcharges, no carrier restrictions. Replacement sets ship like any other part, to any address in the country.
The trade. Sealed lead-acid is heavier — about 14 lb per cell — and it charges overnight rather than in an hour. For a work truck that lives outside, gets parked for a season, and needs to be fixable in a barn, we take that trade every time.
The cell
Tianneng TNE12-25.
A 12V 25Ah sealed deep-cycle traction battery from one of the world's largest lead-acid manufacturers. Nano silica gel electrolyte, no acid stratification, and a 400–600 cycle rating at full depth of discharge.
- Nominal voltage
- 12 V
- Rated capacity, 20 h
- 25.0 Ah
- Capacity, 10 h / 5 h / 2 h
- 23.2 / 22.6 / 20.0 Ah
- Chemistry
- Sealed AGM / gel, deep cycle
- Class
- 6-DZF-20 traction
- Length × width × height
- 181 × 77 × 169 mm
- Height to terminal top
- 170 mm · 6.69 in
- Weight
- 6.45 kg · 14.2 lb
- Terminal
- I10 — M5 brass insert
- Case
- ABS, UL94-HB
- Cycle life, 100% DoD
- 400–600 cycles
- Cycle life, 50% DoD
- ~1,200 cycles
Source: Tianneng Group TNE12-25 datasheet
The pack
Four cells make a 48V truck. Five make a Pro.
Every pack is a straight series string of the same cell. Add a second string in parallel and you have a Dual — same voltage, same speed, twice the amp-hours.
| System | Cells | Pack | Stored energy | Battery weight | Models |
|---|---|---|---|---|---|
| 48V Single | 4 × 12V in series | 48 V · 25 Ah | ~1.2 kWh | ~57 lb | All-Terrain |
| 48V Dual | 8 × 12V · two strings in parallel | 48 V · 50 Ah | ~2.4 kWh | ~114 lb | All-Terrain Dual |
| 60V Single | 5 × 12V in series | 60 V · 25 Ah | ~1.5 kWh | ~71 lb | Pro 60V |
| 60V Dual | 10 × 12V · two strings in parallel | 60 V · 50 Ah | ~3.0 kWh | ~142 lb | Pro 60V Dual |
A second set doesn't make the truck faster. It doubles runtime and halves the load on each cell, which is also what makes the pack last longer under heavy use.
The All-Terrain and the Pro share the same 48–60V controller. The system voltage is set by how many cells are in the string, nothing else.
Dual sets charge through the single factory port. Parallel strings settle to the same voltage on their own — no balancing routine, no second charger required.
Nothing proprietary
No lock-in. Ever.
We build the truck. We don't build a battery you can only buy from us.
- The cell is a standard 6-DZF-20 form factor made by many manufacturers. Any 12V 25Ah deep-cycle AGM or gel battery with matching dimensions and M5 terminals is a drop-in replacement.
- No encrypted battery module, no dealer-only replacement, no software pairing. Swap a set with a wrench and a socket.
- We stock matched sets so you don't have to shop for them — the same cells that ship in the truck, at a straight price.
- Working on your own truck doesn't void the warranty. Batteries are a wear item; everything else is covered for two years.
Performance
Pull hard and the pack gives up less.
Capacity is rated at a slow, 20-hour discharge. Empty the same cell in two hours and you get about 80% of it. That's Peukert's law, and lead-acid feels it more than lithium does.
In practice: steady, moderate throttle covers more ground than repeated hard acceleration, and a heavy load up a long grade eats range faster than the distance alone suggests. A Dual set halves the draw on each cell — which is why it more than doubles real-world range under load.
Source: TNE12-25 datasheet, rated capacity
Typical range on a charge, unloaded, mixed terrain.
Engineering estimate. Real-world 13–23 miles single by conditions; roughly half under a 500 lb load.
Full constant-current discharge data
Amps each 12V cell will deliver for a given time, at 77°F, down to an end voltage of 1.75 V per internal cell (10.5 V per block). Multiply time by amps for delivered amp-hours.
| Duration | 30 min | 45 min | 1 h | 2 h | 3 h | 5 h | 10 h | 20 h |
|---|---|---|---|---|---|---|---|---|
| Current (A) | 30.0 | 21.5 | 17.0 | 10.0 | 6.87 | 4.52 | 2.32 | 1.27 |
| Power (W per cell) | 58.0 | 42.0 | 33.5 | 19.8 | 13.7 | 9.05 | 4.67 | 2.57 |
The datasheet publishes no single "maximum continuous" figure. The 30-minute column (~30 A, about 1.2C) is the highest sustained rate on the sheet. For anything you run all day, keep continuous draw at or below roughly half that.
Inside the charge window. Full performance around 77°F.
Temperature
Cold trims range. It doesn't hurt the pack.
Lead-acid slows down when it's cold and speeds up when it's warm. At freezing you have about 85% of your summer capacity; at 5°F, about 72%. That's chemistry, not a fault, and it comes back with the weather.
- Discharge5°F to 122°FDrive it in this range.
- Charge32°F to 104°FDon't plug in a frozen pack. Let it come up above freezing first.
- Storage5°F to 104°FCool is better than warm — heat speeds up self-discharge.
- Optimum77°F ± 5°Where every rating on this page is measured.
Charging
Plug it in after a full day. That's the routine.
The factory charger runs a three-stage profile — bulk, absorb, float — and stops itself when the pack is full. Charge overnight from a standard wall outlet. No timers, no unplugging, no overcharge.
Plug in after a day of use, full by morning. Included with the truck; spares are $20.
Plug in after a day of use, full by morning. Dual sets charge through the same single port.
Topping off after a short trip is fine but not required. What matters is that the pack doesn't sit low.
Sitting flat is the one thing that shortens sealed lead-acid life. Recharge the same day you run it down.
The charger is rated from 32°F. In a cold shed, bring the truck somewhere warmer to charge, or wait for a mild day.
Charging from solar or a third-party charger — setpoints
For owners charging outside the factory charger: a solar controller, a bench supply, or a custom build. These packs have no battery-management system, so your controller's setpoints are the only protection. Set them exactly.
| Setting | Per 12V block | 48V string (4) | 60V string (5) |
|---|---|---|---|
| Bulk / absorb limit | 14.75–14.85 V | 59.0–59.4 V | 73.8–74.3 V |
| Float | 13.7–13.9 V | 54.8–55.6 V | 68.5–69.5 V |
| Max charge current | ≤ 0.2C | 5 A single · 10 A dual | 5 A single · 10 A dual |
| Temp compensation (ref 77°F) | −24 mV/°C absorb · −18 float | −96 · −72 mV/°C | −120 · −90 mV/°C |
| Resting 100% (4 h off charge) | 12.8–12.9 V | 51.2–51.6 V | 64.0–64.5 V |
Hold absorb until current tapers to roughly 0.5–1 A, then float. Never equalize — these are sealed cells. Don't run the factory charger and a solar controller at the same time. Fuse anything you add close to the battery post. Never pull 12V off a single block in the string. No charging below 32°F. Most consumer MPPT controllers don't offer a 60V profile — confirm a fully programmable lead-acid profile before you buy.
Storage & winter
Charge it, switch it off, walk away.
A sealed lead-acid pack loses about 10% of its charge over three months on the shelf at room temperature. A cold shed slows that down. Heat speeds it up. Either way, the batteries stay in the truck.
- Charge to 100%
Run a full overnight charge before lay-up. A full pack rides out a winter; a half-empty one doesn't.
- Flip the main breaker off
The switch on the battery box isolates the pack completely. With it off, nothing on the truck — USB ports, ring light, controller — can draw the batteries down.
- Leave it where it is
Shed, barn, or unheated garage. The batteries don't need to come inside, and at ~14 lb each in a tight enclosure you don't want them to.
- Top off in spring
Once the pack is back above 32°F, run a full charge before the first day out. If the space stays above freezing all winter, leaving the charger connected on float is fine too.
Stored hot — around 100°F — a pack can be down to half in three to four months. Stored cold, it holds most of a year. If the factory charger won't recognize a pack after a long lay-up, don't replace anything: it can usually be recovered. Contact us and we'll walk you through it.
Source: TNE12-25 datasheet, capacity vs. storage time
Lifespan
One habit decides how long the pack lasts.
Don't run it flat. A cell drained to empty every time is rated for 400–600 cycles. The same cell recharged at half is rated for about 1,200. Charge after a full day and you're on the long curve.
A cycle is one discharge and recharge. At a few work days a week, the difference is seasons versus years. Dual sets help here too: the same day's work is a shallower cycle on each string.
Source: TNE12-25 datasheet, cycle life vs. DoD
Powering accessories
Lights, inverters, winches — the rules.
The pack can run more than the motor. Do it off the full pack, on its own fused circuit, and size it to the battery you have.
- 12V accessories: use a 48V→12V (or 60V→12V) DC-DC converter fed from the main battery terminals. A 40–60 A converter covers lights, USB, fans, radios.
- Never tap 12V off one cell. The cells are in series; pulling from one unbalances the string and damages the pack. Always convert from the full pack.
- Own fused circuit, never through the controller. Inverters and winches wire straight to the battery side with an inline fuse. Reversed polarity damages the controller and isn't covered.
- Keep continuous draw modest. Around 600 W sustained on a single 25 Ah bank, roughly double on a Dual. Short bursts to ~1,400 W are fine. Size an inverter to the tool's surge, not its running watts.
- 48V- or 60V-input inverter, pure sine. Most off-the-shelf inverters are 12V and won't work directly. Mount it vented and weather-protected, not sealed.
- Rain is fine. Submersion isn't. Normal weather is expected. Don't pressure-wash into the battery box.
Planning a specific setup? Send us the tool list and we'll size it with you.
Battery questions
Asked most often.
Does StepRanger use lithium batteries?
No. Every StepRanger ships with sealed lead-acid deep-cycle cells — the Tianneng TNE12-25, four in series for 48V trucks and five for the Pro 60V.
What battery does it use, exactly?
A 12V 25Ah sealed AGM/gel deep-cycle cell in the standard 6-DZF-20 traction form factor: 181 × 77 × 169 mm, 14.2 lb, M5 bolt-down terminals. The full datasheet is linked above.
Can I replace the batteries myself?
Yes. The pack is bolted together with standard terminals inside the battery box. We sell matched sets — the 48V set is four cells, the 60V set is five — or you can use any 12V 25Ah deep-cycle AGM/gel cell of the same size. Replace a full string at once so the cells age together, and doing your own work doesn't affect your warranty.
How long does a charge take?
Plug it in after a day of use and it is fully charged overnight, on any model, single or dual. The charger runs bulk, absorb, and float on its own and stops when the pack is full, so leaving it connected is fine.
Will cold weather hurt the batteries?
No. Cold reduces available capacity — about 85% at freezing and 72% at 5°F — and it comes back as the pack warms. The pack is rated to discharge down to 5°F. The one rule: don't charge below 32°F.
Do I need to bring the batteries inside for winter?
No. Charge to full, flip the main breaker off, and leave the truck in the shed or garage with the batteries in place. Top it off in spring once it's above freezing. Sealed lead-acid handles cold storage without damage.
How long do the batteries last?
It depends almost entirely on how deep you run them. Drained flat every cycle, the cell is rated for 400–600 cycles. Recharged after a normal day at roughly half, about 1,200. For most owners that's years, not seasons.
What's the difference between a Single and a Dual?
A Dual adds a second string of cells in parallel. Same voltage and speed, double the amp-hours: roughly double the range, more headroom for accessories, and a shallower cycle on each cell. Both strings charge through the one factory port.
Can I run an inverter or power tools off it?
Yes, with sizing care. Wire a 48V- or 60V-input pure-sine inverter straight to the battery on its own fused circuit, never through the controller. A single 25 Ah bank sustains roughly 600 W; a Dual roughly double. Short surges to about 1,400 W are fine. For regular high-draw use, a Dual set is the right starting point.
My pack sat all winter and the charger won't recognize it. Is it dead?
Usually not. A deeply discharged pack can often be brought back with an ordinary 12V automotive charger on each cell for 45–60 minutes, after which the factory charger picks it up normally. Contact us before replacing anything and we'll walk you through it. If a cell truly won't come back within the warranty period, it's covered.
Next
A truck you can keep running yourself.
Two-year warranty on the truck, standard cells in the box, and a co-founder on the phone when you have a question.