The Orion cell tap validation tool for the Junior, which also covers the standard Orion BMS 2. It checks a cell tap harness for correctness before it is connected to the BMS.
A cell tap harness carries a wire from every cell group in the pack. Cross two, reverse a polarity, or leave one off, and the BMS sees voltages that make no sense. In the worst case it sees a large fraction of pack voltage across an input designed for a single cell, and the damage is done in the instant the connector seats.
The harness is also the last thing built and the first thing plugged in, usually at the end of a long day, by someone who has just finished a hundred crimps. This tool takes that moment out of the critical path: you test the harness on its own, confirm it, then connect it.
It finds incorrect sequence, reversed polarity, missing connections and shorts.
This is the Junior 2 version, which covers the Orion BMS 2 Junior as well as the standard BMS 2. If you are only ever working with the standard BMS 2, the standard validation tool is the other option.
Key specifications
| Part | OXMTAPJ2 |
|---|---|
| Type | Cell tap harness validation tool |
| Compatible with | Orion BMS 2 and Orion BMS 2 Junior cell tap harnesses |
| Detects | Incorrect sequence, reversed polarity, missing connections, shorts |
| Weight | 0.9 kg |
Features
- Finds a harness fault while it is still a harness fault, not a dead BMS
- Catches the four failures that actually happen: sequence, polarity, opens and shorts
- Covers both the BMS 2 and the Junior, so one tool suits a workshop running both
- Pays for itself the first time it stops a miswired harness reaching a BMS
Compatibility
For Orion BMS 2 and Orion BMS 2 Junior cell tap harnesses.
If you only need it once, hire it. Most builders validate a pack and then have no use for the tool until the next one, so we also offer the standard tool on 7 or 14 day hire. Buy it if you build packs regularly.
In the box
- 1 x cell tap validation tool, Junior 2
Downloads
No document is published for this tool. The standard validation tool's manual covers the same procedure.



Worldwide Shipping
Fellten offers worldwide shipping through trusted carriers including UPS, DHL, and pallet freight services. Whether you're a professional installer or a classic car enthusiast, we ensure your order is packed securely and delivered efficiently.
We are fully certified to ship dangerous goods, including lithium-ion batteries, in compliance with all international regulations.
For UK orders, most in-stock items are eligible for next working day delivery if placed before 12:00 PM. Orders placed after this time will be shipped on the next working day. Please note that all delivery estimates are stock-dependent, and you will be notified if any delays are expected.
Shipping costs are calculated at checkout based on your location and order details, so you’ll always have clear and accurate pricing before completing your purchase.
Payments are securely processed using Stripe. We accept all major credit and debit cards.
