Expand your backup power with the FIRMAN Zero-E Battery expansion pack. Adding 1,040Wh of capacity to your FIRMAN Zero-E Energy Storage System, this slide-lock battery connects effortlessly—just slide it into place until
Competitive in its class for camping & home projects.
Best for: Camping & Home Projects
Running output
See specifications
Fuel / power
Battery
Weight
28.6 lb
Strongest reasons
Expand your backup power with the FIRMAN Zero-E Battery expansion pack. Adding 1,040Wh of capacity to your FIRMAN Zero-E Energy Storage System, this slide-lock battery connects effortlessly—just slide it into place until.
Stored energy is higher than 65% of its class.
Battery power avoids exhaust at the point of use.
Know before buying
This is an expansion battery, not a standalone power source. Confirm the exact compatible base station before buying.
Scores at a glance
63
Class score
59
Starter fit
Competitive in its class among 103 compact expansion batteries.
The only verified seller destination. Its listed price is known, but shipping and delivered cost still need confirmation. Confirm price, stock, shipping, and the exact model on the seller’s site.
Class comparisons use 103 compact expansion batteries. Runtime figures can use different loads, fuels, or test conditions; confirm the model manual before planning fuel or battery duration.
Product gallery & complete specifications Official imagery, full spec tables, use cases, and source linksView details
These manufacturer images may include dimensions, control-panel callouts, included equipment, safety features, and common use cases. Scroll sideways to view the complete set available for this model.
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Complete specifications
Every official field, organized.
The technical fields below come from FIRMAN’s model-specific specification file. Product photos and infographics come from the official product gallery. Confirm current documentation before purchase.
Outdoor use only for combustion models. Never operate a fuel-burning generator inside a home, garage, shed, or other enclosed space. Follow FIRMAN’s manual and use an approved transfer method for home connections.
Manufacturer overview
Expand your backup power with the FIRMAN Zero-E Battery expansion pack. Adding 1,040Wh of capacity to your FIRMAN Zero-E Energy Storage System, this slide-lock battery connects effortlessly—just slide it into place until it clicks. Stack up to 10 batteries for a total capacity of 11,440Wh, giving you serious energy for extended outages or off-grid use. Charge it independently or as part of your Zero-E system. An onboard 100W USB-C port powers laptops, tablets, phones, drones, and more. Built with Lithium Iron Phosphate technology, the Zero-E Battery delivers safe, reliable performance with over 4,000 charge cycles. Whether you're preparing for emergencies or powering adventures, this expansion pack keeps you going longer. The FIRMAN Zero-E Energy Storage System delivers clean, emission-free power wherever you need it—perfect for homes, apartments, RVs, and vehicles. With 4,000 starting watts and 2,000 running watts, the Zero-E can power small to medium appliances, electronics, and essential devices. Featuring advanced EPS (Emergency Power Supply) pass-through technology, the Zero-E automatically backs up your fridge, modem, sump pump, or security system during an outage—switching to battery power in milliseconds. Its Lithium Iron Phosphate battery ensures safe operation, 4,000+ charge cycles, and long-term reliability. Need more runtime? Easily expand with slide-on Zero-E batteries—up to 10 add-ons for a total of 11,440Wh capacity. Power up your devices with six 120V outlets, a TT-30R RV outlet, four USB-A ports, two 100W USB-C ports, a 12V cigarette outlet, a 12V DC port, and a Qi wireless charger. Recharge the Zero-E your way: from a standard wall outlet, your vehicle’s 12V socket, or up to 400W of solar input. Whether you're preparing for emergencies or living off-grid, the Zero-E is your all-in-one portable power solution.
Certifications
cETLus (UL2743)
Yes
UN38.3
Yes
FCC SDOC
Yes
FCC ID
No
IC ID
No
DOE
No
CEC
No
SDS
Yes
ROHS
Yes
Main Unit
Rated Capacity
1040Wh
Cycle Life
>4000 complete cycles to 80% capacity
Storage Temperature
-20 ~ 40 °C (-4 ~104 °F)
Discharging Temperature
-20 ~ 40 °C (-4 ~104 °F)
Charging Temperature
0 ~ 40 °C (32 ~104 °F)
Shelf Life
12 Month
Input
AC Charging Watts
400W
MPPT Watts
400W
Car Charging Watts
240W
USB-C PD Watts
100W
Output
USB-C PD Watts
100W
Control Panel
LED Level Display
Yes
Main Power Switch
Yes
USB-C PD In&Out 100W
Yes
XT60 DC Input
1
Expansion Pack Male Connector
Yes
Expansion Pack Female Connector
Yes
XT60 Cover
Yes
Frame
Pull Rod
Yes
Color
Black
Battery Pack&BMS
Battery Cell Spec
LI-FUN 25Ah 3.2V
Battery Type
LFP
Pack Configuration
13S1P
Cooling
NA
Rated Charging Current
35A
Rated Discharging Current
65A
Overcurrent Protection
Yes
Temperature Protection
Yes
Short Circuit Protection
Yes
Balance Management
Yes
Packaging
UPC Code
840876105016
Carton Dimensions
19.7x15x11.4
Carton Weight
31.5
Product Dimensions
15.4x10.6x8.3
Product Weight
28.6
Best-fit uses
Camping
Home Projects
Power Outage
Tailgate
Work
Standout features
See the complete specifications and official gallery above.
Compare it with your actual load.
Run your essentials through our independent wattage calculator before buying.
The lowest sticker price is not always the best offer. We rank exact-model seller pages using price, stock, shipping, freshness, returns, and warranty details—then show what is still unknown.
Price and delivered cost
Shipping is included only when the seller publishes a usable amount.
Stock and freshness
Current, low-stock, preorder, and stale records are scored differently.
Purchase protections
Published return and warranty terms improve evidence confidence.
Affiliate-neutral ranking
Commission status is recorded but never adds ranking points.
Watch this model
Save it to your shortlist to retain the current price snapshot and turn price and safety watches on or off.
The only verified seller destination. Its listed price is known, but shipping and delivered cost still need confirmation.
Seller data checked Sep 15, 2026.
Shipping not yet verified.
Open fields: confirmed stock, delivered cost, return window, warranty term.
Prices, local stock, shipping, taxes, installation, and seller terms can change. Confirm the exact model and final checkout total before buying. Affiliate disclosure.
One exact-model seller destination is currently verified. We show the unknown fields so a single listing is never presented as a broad market comparison.
A durable record, starting with verified snapshots.
We preserve each dated seller observation instead of replacing the old number. Trends use the lowest verified listed price on each observation date—not an estimated market price.
Ownership is mostly about charge readiness, cable compatibility, storage conditions, and preserving battery health.
Ownership rule
Use the exact FIRMAN B104201 manual for maintenance intervals, fluids, storage limits, and warranty requirements. Similar models are not interchangeable.
Coverage can vary by use, seller, and region. Confirm eligibility and exclusions before purchase.
Service information
2 official resources
An owner or operator manual is linked below for exact service intervals.
Battery care
Low mechanical upkeep
Plan for charge-state, cable, ventilation, firmware, and storage-temperature checks.
Handling & storage
28.6 lb · Battery
Store dry and within the manufacturer’s published temperature and charge-state limits.
Practical care plan
From delivery to long-term readiness
1
Day one
Register and record the exact unit
Save the receipt, serial number, seller, warranty terms, and all included cables before packaging is discarded.
2
First setup
Confirm charging limits and update status
Use the official manual to verify every AC, vehicle, and solar input limit. Install firmware updates only through the manufacturer’s supported process.
3
Before a trip or outage
Run a readiness check
Inspect ports and cables, confirm state of charge, test the intended loads, and make sure the recharge plan still matches the forecasted need.
4
During storage
Protect long-term battery health
Follow the model manual for storage temperature, ventilation, recharge cadence, and recommended state of charge. Do not use generic battery advice in place of its limits.
Before you buy
Five ownership questions to settle first
Confirm that 3-year warranty applies to your seller, region, and intended use.
Open the official manual for B104201 and review setup, service intervals, warnings, and storage requirements.
Verify access to FIRMAN parts, authorized service, and a practical return path in your area.
Confirm every charging cable, solar input limit, expansion-battery match, and indoor-use restriction.
Confirm the unit, fuel or charging gear, and essential cords fit the intended storage and transport space.
We separate sourced facts, reproducible calculations, editorial judgments, and missing evidence. That makes every important claim easier to inspect—and harder to overstate.
Published-data coverage
100%documented
6 of 6 relevant evidence fields are documented for this model.
Source-backed editorial analysis—not a hands-on or laboratory test.
No Find My Generator hands-on test, instrumented load test, teardown, or long-term ownership trial is claimed for this page.
Manufacturer specifications may use different fuels, loads, test distances, temperatures, or operating modes. Cross-brand comparisons inherit those differences.
The listed price is a dated snapshot and may not equal the current delivered price.
Editorial analysis for FIRMAN B104201. Source record last verified Sep 15, 2026. Corrections can be submitted through the contact page with a model-specific source.
Ownership resources
Accessories, manuals, and documents.
Start with the exact FIRMAN B104201 model or item number. Accessory families can look alike while using different connectors, electrical limits, engines, or mounting points.
Compatible accessories
Match by model and connection.
Verify exact fit
Solar charging equipment
Shop FIRMAN solar panels, charging leads, and adapters intended for its portable-power ecosystem.
Match the connector, solar input voltage, current limit, and maximum input published for B104201.
Compatibility note: Links lead to manufacturer or official retailer resources. Confirm the full model or item number, connector type, voltage, amperage, and published compatibility list before buying. Installation involving a home panel, inlet, transfer switch, or fuel plumbing should be handled as required by local code.
Deeper analysis
Open the details you need
The key decision is above. These supporting scorecards, owner signals, and evidence notes stay out of the way until you want to inspect them.
Fit and score detailsSee the class benchmarks and personalize the fit score for your needs.
Find My Generator score
63/ 100
Competitive in its class
Compared with 103 compact expansion batteries in the current catalog.
Endurance65
Stored energy versus the class
Portability38
Lower weight scores higher
Fuel flexibility85
Rechargeable, indoor-safe operation
Value76
Output or stored energy per listed dollar
Class comparison
See what each spec really means.
A number is more useful with context. Each row shows this model beside its class median and translates the difference into a percentile.
SpecificationThis modelClass medianClass standing
Stored energy
Higher than 65% of its class
This model · 1,040Wh
Median · 1,008Wh
Higher than 65% of its class
Product weight
Lighter than 38% of its class
This model · 28.6 lb
Median · 25.3 lb
Lighter than 38% of its class
How the score works: Scores use published specs and are relative to comparable products in this catalog. Missing specs are excluded and remaining weights are normalized. Runtime is the longest manufacturer-published figure and may use a different load or fuel than another model.
This personal score is separate from the model’s class score. It measures fit against your priorities and gives neutral partial credit when price or noise data is missing.
Power fit
0/35
3,000W below your running target.
Budget fit
20/20
$499.99 is within your budget.
Fuel fit
15/15
Battery works with your flexible fuel preference.
Portability
10/10
28.6 lb against your medium portability priority.
Noise fit
10/10
Battery operation strongly matches your quietness preference.
Use-case fit
3.5/10
Home-backup fit rewards adequate output and fuel flexibility.
Testing, reviews and evidenceCheck hands-on testing status, owner reliability signals, sources, and data confidence.
Checking the hands-on test ledger…
Testing protocol
The methods behind every result.
This category-specific protocol defines the questions, equipment, conditions, outputs, and safety gates required for this exact model. Published specifications stay visibly separate from hands-on measurements.
These numbers organize the test plan. They are not independent confirmations.
Model-specific test matrix
Questions the measurements must answer.
01
Planned measurement
Usable added energy
Pending
How much additional delivered energy does B104201 provide to a compatible base station?
Pair the exact manufacturer-approved base station and firmware, fully balance the system, then discharge through a measured fixed AC load to normal cutoff. Repeat the same base-station test without the expansion battery.
How much input energy is required for the added usable output?
Measure wall input energy for the paired-system recharge and delivered output energy for the matched discharge. Subtract the separately measured base-station contribution.
Does the paired system charge, balance, sleep, and wake predictably?
Record displayed state of charge for the base and expansion battery during charge, rest, discharge, shutdown, and restart. Note balancing time and any persistent percentage divergence.
Do surface temperatures remain stable during sustained charge and discharge?
At defined ambient conditions, record non-contact surface temperatures at repeatable enclosure and connector locations during the paired system’s charge and discharge cycles.
Which exact base station, cable, and firmware combination was proven?
Record model, serial, cable or dock identifier, firmware, connection sequence, and all system messages. Do not generalize results to similar-looking connectors or unlisted models.
Verified base modelCable / dock IDFirmwareConnection result
Controlled conditions
Record the exact model, serial number, firmware, sample source, and test date before any measurement.
Log ambient temperature, humidity, elevation, wind, surface, and background sound for every test block.
Record instrument model, range, accuracy, and most recent calibration or verification date.
Repeat timing, starting, and sound measurements three times when conditions allow; publish every valid run.
Keep original notes, load logs, meter exports, photos, and any excluded-run explanation with the result.
Required equipment class
Rated programmable or resistive AC load
Bidirectional watt-hour and power analyzer
Calibrated sound-level meter
Temperature logger or verified non-contact thermometer
Waveform capture equipment when transfer-time claims are tested
Safety gate
Use a noncombustible, ventilated test area with battery-rated emergency procedures; stop for swelling, odor, smoke, leakage, abnormal heat, or impact damage.
Testing is for qualified personnel using correctly rated load equipment and the manufacturer’s required grounding, bonding, clearance, and protective-device instructions.
Never connect a generator directly to building wiring or bypass overload, temperature, battery, GFCI, or carbon-monoxide shutdown protection.
Stop a run for unstable voltage or frequency, overheating, fuel or electrolyte leakage, abnormal sound, damaged wiring, or any manufacturer fault indication.
Badge rule: this product receives no “FMG Tested” label or score benefit until a real unit, instruments, conditions, valid runs, raw records, and limitations are documented under the public protocol.
Verified owner reliability
What happens after the honeymoon period?
Long-term reports from confirmed owners show starting, maintenance, failure, support, and recommendation outcomes for the FIRMAN B104201.
Reliability percentages stay hidden until at least 5 ownership-verified reports are published for this exact model — 5 more needed.
Ownership checked
Purchase or registration evidence is reviewed privately.
Time in service
Reports separate new ownership from 12+ month experience.
Failures documented
Repairs and maintenance are captured, not buried in a star.
Reports stay private while ownership and model details are checked. Contact information is never shown publicly.
Data trust & safety
Fresh specifications. Visible recall checks.
We show when this record was verified, where its specifications came from, and whether its model number appears in the official CPSC generator-recall dataset.
Prices can change faster than technical specifications. Always confirm the current price, exact model number, and manual before purchase.
CPSC model screening
No model-number match found
39 records checked
The FIRMAN B104201 model text did not match the generator recall records in our current CPSC snapshot. This is a screening result, not a guarantee or safety certification. Recalls can be serial-number specific, newly published, or use a different product description.
Review scope: exact model identity, published specifications, calculation inputs, source quality, safety language, and affiliate independence. This is an internal editorial review, not third-party engineering, electrical, or safety certification. Hands-on testing is claimed only when a complete test record is published.Request a correction.
