The architecture
A 48V server-rack battery feeds a 3kW pure-sine inverter/charger. 800W of PV enters through MPPT. AC output goes to a small protected outlet strip/subpanel on the cart; DC-DC conversion handles lights/USB. The cart uses a steel job box or welded frame with low center of gravity.
Load and sizing math
Corded tools are high watts but low duty cycle. Tool chargers and lights are lower watts for many hours.
| Load | Watts | Hours/day | Daily Wh | Notes |
|---|---|---|---|---|
| Tool battery chargers | 300 | 4 | 1200 | Mixed charging |
| Circular saw / grinder | 1500 | 0.3 | 450 | Intermittent |
| Small compressor | 1000 | 0.5 | 500 | Duty-cycle equivalent |
| Work lights / USB | 80 | 6 | 480 | All day |
| Illustrative total | 2630 Wh/day | Before system margin | ||
Around 2.6kWh/day fits comfortably in a 5kWh battery with reserve. 800W of PV can replace a large fraction of a day's use in good sun.
Full parts list
This is a shopping architecture, not a demand that you buy one exact brand. Match voltage, current and connectors before ordering. Budget ranges reflect the class of hardware rather than a live quote.
48V 100Ah rack battery
Target spec: 51.2V, ~5.12kWh, 100A BMS
Enough energy and current for 3kW inverter use.
Budget: $900–$1600 each
3kW 48V inverter/charger
Target spec: Pure sine, hardwire or outlets, generator/AC charge optional
Runs corded tools and OEM chargers.
Budget: $500–$1200 each
800W solar array
Target spec: Portable/folding or rack-deploy
Meaningful workday recharge.
Budget: $450–$1200 each
MPPT controller
Target spec: 48V bank, PV voltage matched to array
Converts array energy efficiently.
Budget: $150–$350 each
Heavy rolling job box/frame
Target spec: Pneumatic or large casters, 300lb+ capacity
Battery is heavy; center of gravity matters.
Budget: $150–$500 each
DC-DC converter + LED work lights
Target spec: 48V to 12V, 20A class
Runs efficient low-voltage lights/USB without inverter.
Budget: $40–$120 each
Wiring map
This is a high-current build. Use a battery disconnect, appropriately rated Class-T or manufacturer-specified fuse, busbars and protected AC distribution.
[800W PV]-->[MPPT]-->[48V 5kWh BATTERY]-->[MAIN FUSE/DISCONNECT]-->[3kW INVERTER]
| |
[48->12V] AC outlets
| | chargers / tools
LEDs USB
Step-by-step build
Define the heaviest tool
Check startup and running watts of the compressor/saw you truly intend to use.
Choose the cart/frame
Battery and inverter should sit low; panels/cables can ride above.
Mount battery restraint
Use a real mechanical hold-down, not just friction or straps against a smooth case.
Install main DC protection
Fuse and disconnect close to the battery and follow inverter cable-size guidance.
Install inverter and AC outlets
Protect AC outlets appropriately and keep AC/DC compartments physically organized.
Add the MPPT and PV connector panel
Put solar connectors where deployed panels can plug in without opening the high-current battery bay.
Add 48-to-12V accessories
Lights and USB run from a switched DC-DC converter.
Load-test with the actual tool
Start compressor/saw repeatedly while monitoring battery voltage, BMS current and inverter temperature.
Commission it before you trust it
The project is not finished when the LED comes on. Run it through a controlled test so the first real failure is not in the field.
- Battery physically restrained
- Main DC fuse installed
- Disconnect accessible
- Inverter ground/bond per manual
- AC outlets protected
- Cable lugs torqued
- Ventilation clear
- Caster load rating adequate
- Tool surge test passed
- PV open-circuit voltage checked
Mistakes to avoid
Undersizing the battery because the panel is large
Panels make energy only when conditions cooperate. The battery has to carry the load through night, cloud and short high-demand events. Size energy storage from watt-hours, not panel watts.
Ignoring standby loads
Controllers, routers, cameras, inverters and cellular hardware can consume power 24/7. On small projects, a 5W always-on device is 120Wh per day—sometimes more than the 'main' load.
Using one fuse for the entire project
Fuse each branch according to its conductor and load. The fuse protects wire, not the gadget. A downstream short should not require an oversized main fuse to clear.
Mounting the panel where the project is instead of where the sun is
The load can sit in shade. The panel cannot. Use a cable run, pole or remote mount to put the collector in the best solar window.
Skipping a low-voltage disconnect
Deep-discharge protection is cheap insurance. Many charge controllers or smart battery systems can disconnect noncritical loads before the battery is abused.
Upgrade path
Add generator/shore input
The inverter/charger can recharge quickly when solar is not enough.
Add fold-out workbench
Make the cart physically useful even when power is not the limiting factor.
Add a second battery
For all-day corded-tool use, doubling to 10kWh extends runtime and discharge headroom.
Frequently asked questions
Why 48V instead of 12V?
At 3kW, 48V reduces battery current dramatically and makes cabling more manageable.
Can 800W of solar run a circular saw directly?
No; the battery/inverter handles surge and short high power while solar replenishes energy over time.
Is this portable?
It is movable on a job site, not lightweight. Plan ramps and terrain.
Affiliate disclosure: SolarBuild.co participates in Amazon Associates, eBay Partner Network, BLUETTI via CJ Affiliate and Renogy via Impact. We may earn a commission from qualifying purchases at no extra cost to you.