Checked as a single pack, which covers this inverter’s charge current on its own.
Full specifications: Sunsynk 5kW Hybrid and Fortress eVault Max 18.5kWh.
The four checks
Voltage window: Overlapping window 44.8 to 58.4 V
The inverter operates from 40 to 60 volts and the battery cuts off outside 44.8 to 58.4 volts. Both stay inside 44.8 to 58.4 volts, which covers a normal LiFePO4 charge and discharge cycle with margin at both ends.
Charge current: 120 A into a 133 A limit
The inverter tops out at 120 amps and the battery accepts 133 amps, so a default install cannot overrun the pack. Adding batteries in parallel raises the accepted current further.
Surge rating: Peak draw 208 A exceeds 200 A
A full surge to 10000 watts pulls roughly 208 amps, past this battery’s 200 amp surge rating for 5 s. The BMS is the thing that stops it, which means a motor start can drop the whole system rather than just dimming the lights. Adding a second pack in parallel is the usual fix.
Closed-loop communication: Both speak CAN, RS485, no document names the pair
The inverter and the battery both support CAN, RS485. Neither manufacturer publishes a document naming the other unit, and a shared bus standard is not a shared message format. It may well work on the bench. Confirm the protocol setting with both manufacturers before relying on BMS control.
What this means when you install it
Set the inverter charge current to 120 amps or less. That is the inverter maximum, which this bank can absorb. Protect the battery run with a 150 amp Class T fuse and 1 AWG cable.
The inverter and the battery both support CAN, RS485. Neither manufacturer publishes a document naming the other unit, and a shared bus standard is not a shared message format. It may well work on the bench. Confirm the protocol setting with both manufacturers before relying on BMS control.
Figures side by side
| Field | Sunsynk 5kW Hybrid | Fortress eVault Max 18.5kWh |
|---|---|---|
| Voltage window | 40 to 60 V | 44.8 to 58.4 V |
| Charge current | 120 A delivered | 133 A accepted |
| Peak draw | 10,000 W surge | 200 A surge |
| Usable capacity | n/a | 18.5 kWh |
| Comms | CAN, RS485 | CAN, RS485 |
Manufacturer documents
Manufacturer documents: Sunsynk product documentation. Figures here should be read against the revision that covers your serial number, because manufacturers revise specifications without changing the model name.
Manufacturer documents: Fortress Power document library. Figures here should be read against the revision that covers your serial number, because manufacturers revise specifications without changing the model name.
Both units, current pricing
Prices on these move week to week, and the battery is usually the line item worth watching.
Sunsynk 5kW Hybrid on AmazonFortress eVault Max 18.5kWh on AmazonComms cableAffiliate links. As an Amazon Associate this site earns from qualifying purchases, at no extra cost to you. Prices and stock change often, and a listing appearing here is not a statement that the pairing above is approved.
Other pairings for the Fortress eVault Max 18.5kWh
EG4 18KPV with Fortress eVault Max 18.5kWh
Partial match, some fields unverified.
Sol-Ark 12K with Fortress eVault Max 18.5kWh
Specs align on every checked field.
Sol-Ark 15K with Fortress eVault Max 18.5kWh
Specs align on every checked field.
Victron MultiPlus-II 48/5000 with Fortress eVault Max 18.5kWh
Specs align on every checked field.
Questions people actually ask
Will the Sunsynk 5kW Hybrid work with the Fortress eVault Max 18.5kWh?
Specs conflict on at least one field. Checked as a single pack, which covers this inverter’s charge current on its own. The four checks below show which field produced that result.
What does this pairing cost to wire up?
Beyond the two units, a 150 amp Class T fuse and holder, 1 AWG battery cable cut to matched lengths, and a busbar if you are running 1 packs. A comms cable if you intend to attempt closed loop, and the pinout is rarely the same between brands.
Where does this pairing go wrong in practice?
The inverter and the battery both support CAN, RS485. Neither manufacturer publishes a document naming the other unit, and a shared bus standard is not a shared message format. It may well work on the bench. Confirm the protocol setting with both manufacturers before relying on BMS control.
What charge current should I set?
The inverter tops out at 120 amps and the battery accepts 133 amps, so a default install cannot overrun the pack. Adding batteries in parallel raises the accepted current further.