40v side-by-side adapter compatible with Ryobi 18v

Updated 05/22/2025

Allows for the use of two Ryobi 18v batteries in place of a 40v battery.

Suggested print settings:
 - 0.20mm QUALITY
 - PETG (pictured using OVERTURE PETG Grass Green)
 - Infill density 20%
 - Infill pattern Grid
 - 3 Perimeters
 - Supports required

Assemble by printing:
 - Qty. 1 of 18V DUAL to 40v wSpacer v2.2
 - Qty. 2 of 18v terminal glue-in (so you end up with 4 pieces)
 - Qty. 1 of 40v to 18v plate 14awg v3.4

Insert Qty.4 of Keystone 209. 1 Cell Leaf Spring Battery Contact (with wires soldered on at about a 45deg angle, use a MINIMUM of 14 AWG, see the picture for lengths, allow soldered connections to cool BEFORE inserting!!!)

The batteries are wired in series; the gray wire goes from - on the first battery to + on the second battery.

Optionally use J-B weld high heat to submerge the +positive leaf spring terminal in place.

Glue in Qty.4 of “18v terminal glue-in” over the leaf spring contacts you inserted

Pass the wires through the channel and into the channel in the 40v to 18v plate

Attach the 40v to 18v plate using Qty.4 of M4 14mm or 16mm (max) screws

Crimp on ¼" male spade quick connect terminals and insert into the 40v to 18v plate

Glue in Qty.1 of plate terminal cover (prints with the 40v to 18v plate)

** KNOWN COMPATIBILITY LIST BELOW **
-- RY40407 = Blower 550 CFM, 125 MPH Whisper Series (Brushless)
-- RY40408 = Blower 525 CFM, 110 MPH
-- RY404013 = Blower 650 CFM, 160 MPH (Brushless)
-- RY404015 or RY404150 = Blower/Vacuum 600CFM
-- RY40002 = String Trimmer/Power Head (Expand-It)
-- RY40006 = String Trimmer/Power Head (Expand-It)
-- RY40220 = String Trimmer/Power Head (Expand-It)
-- RY40009 = String Trimmer/Power Head (Brushless)
-- RY402011 = String Trimmer/Power Head (Brushless)
-- RY40604 = Hedge Trimmer (Brushless)
-- RY408013 = Snow Shovel
-- RY40405BTL = Vac Attack Leaf Vacuum/Mulcher
-- RYi300BG = 40V 300-Watt Pure Sine Wave Power Source

** DO NOT USE ** any adapter in...
- RY404100 or RY404010 = Blower 730 CFM, 190 MPH Whisper Series (Brushless) ...this model has been observed drawing too much amperage, resulting in melted contacts
- RYi1802BT or RYi1802B6 = 1800-Watt Portable Battery Power Station Inverter Generator ...because it cannot communicate with the battery pack extra pins, it does not recognize the battery at all

You can use this adapter instead of a Ryobi 40v battery with P/N: OP4020A = 2Ah / OP4040 = 4Ah / OP4040A1 = 4Ah / OP40404VNM = 4Ah / OP40504 = 5Ah / OP4050A = 5Ah / OP4060A = 6Ah / OP4060A1 = 6Ah / OP40604 = 6Ah / OP40605 = 6Ah HP / OP40754 = 7.5Ah / OP4080A = 8Ah / OP40804 = 8Ah / OP40125 = 12Ah

The batteries are wired in series.

NOTE: Always use two 18v batteries that are at the same Ah rating and the same level of charge. The BMS built into all Ryobi 18v batteries will still provide a safe low voltage cut-off when the batteries are used in series to power a tool.

NOTE: Never try to charge two 18v Ryobi Li-Ion batteries in series (in any 40v charger) as damage to the BMS is possible. Charge the 18v batteries individually in approved chargers.

If you need the STLs of these parts, please see:
https://www.printables.com/model/1303958

Don't have a 3D printer yet? That's OK, order already printed from…

https://jpelectron.etsy.com