Checked as a single pack, which covers this inverter’s charge current on its own.
Full specifications: OutBack VFXR3648A and Pytes R-BOX 48V 100Ah.
The four checks
Voltage window: Overlapping window 44.8 to 58.4 V
The inverter operates from 40 to 64 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: 85 A into a 100 A limit
The inverter tops out at 85 amps and the battery accepts 100 amps, so a default install cannot overrun the pack. Adding batteries in parallel raises the accepted current further.
Surge rating: Battery surge figure unpublished
A surge to 7200 watts draws roughly 150 amps at 48 volts. This battery publishes a 100 amp continuous rating and no separate surge figure, and continuous is the wrong number to check a motor start against. Confirm the peak rating and its duration with the manufacturer before running motor loads.
Closed-loop communication: No shared protocol
The inverter speaks Modbus and the battery speaks CAN, RS485. There is no common protocol between them, so closed-loop operation is off the table regardless of cabling.
What this means when you install it
Set the inverter charge current to 85 amps or less. That is the inverter maximum, which this bank can absorb. Protect the battery run with a 100 amp Class T fuse and 2 AWG cable.
The inverter speaks Modbus and the battery speaks CAN, RS485. There is no common protocol between them, so closed-loop operation is off the table regardless of cabling.
Figures side by side
| Field | OutBack VFXR3648A | Pytes R-BOX 48V 100Ah |
|---|---|---|
| Voltage window | 40 to 64 V | 44.8 to 58.4 V |
| Charge current | 85 A delivered | 100 A accepted |
| Peak draw | 7,200 W surge | surge unpublished |
| Usable capacity | n/a | 5.12 kWh |
| Comms | Modbus | CAN, RS485 |
Manufacturer documents
Manufacturer documents: OutBack Power 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: Pytes download centre. 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.
OutBack VFXR3648A on AmazonPytes R-BOX 48V 100Ah 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 Pytes R-BOX 48V 100Ah
EG4 6000XP with Pytes R-BOX 48V 100Ah
Partial match, some fields unverified.
EG4 18KPV with Pytes R-BOX 48V 100Ah
Partial match, some fields unverified.
EG4 FlexBoss21 with Pytes R-BOX 48V 100Ah
Partial match, some fields unverified.
Sol-Ark 12K with Pytes R-BOX 48V 100Ah
Partial match, some fields unverified.
Questions people actually ask
Will the OutBack VFXR3648A work with the Pytes R-BOX 48V 100Ah?
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 100 amp Class T fuse and holder, 2 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 speaks Modbus and the battery speaks CAN, RS485. There is no common protocol between them, so closed-loop operation is off the table regardless of cabling.
What charge current should I set?
The inverter tops out at 85 amps and the battery accepts 100 amps, so a default install cannot overrun the pack. Adding batteries in parallel raises the accepted current further.