# Fathom X tether maximum current rating **URL:** \ **Category:** Blue Robotics Products\ **Created:** [December 12, 2024, 3:17pm UTC](https://discuss.bluerobotics.com/t/fathom-x-tether-maximum-current-rating/18833 "2024-12-12T15:17:08Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![zurn](https://avatars.discourse-cdn.com/v4/letter/z/a3d4f5/32.png) [@zurn](https://discuss.bluerobotics.com/u/zurn)\ **Post date:** [December 12, 2024, 3:17pm UTC](https://discuss.bluerobotics.com/t/fathom-x-tether-maximum-current-rating/18833/1 "2024-12-12T15:17:08Z")
Hi everyone, I’m just wondering if there’s a definitive maximum current rating for the Fathom X tether. I can’t seem to find it anywhere. I realize the wires are 26 AWG, but the internet provides VERY inconsistent current ratings from page to page. We have the 100 ft, 4 conductor one (BR-100862-100). Thanks! -Dave ---
**Author:** ![tony-white](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/tony-white/32/18385_2.png) [@tony-white](https://discuss.bluerobotics.com/u/tony-white)\ **Post date:** [December 12, 2024, 6:24pm UTC](https://discuss.bluerobotics.com/t/fathom-x-tether-maximum-current-rating/18833/2 "2024-12-12T18:24:43Z")
Hi @zurn - There is not simple answer to this - it depends entirely on how much cooling you’re able to provide! This [calculator](https://bluerobotics.com/learn/voltage-drop-calculator/) will tell you the energy that is lost due to voltage drop in the wires. If you’re able to dissipate that heat energy along the length of wire, by say, immersing it in water, you’ll have more current capacity then if the tether is entirely dry… Higher voltages help! The more the copper the better! Note - the Fathom-X is the tether interface, and our tether is called Fathom tether. You also have an 8 conductor, 4 _twisted pair_ tether if that BR # is correct. ---
**Author:** ![PoseidonROV](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/poseidonrov/32/5541_2.png) [@PoseidonROV](https://discuss.bluerobotics.com/u/PoseidonROV)\ **Post date:** [December 13, 2024, 7:12am UTC](https://discuss.bluerobotics.com/t/fathom-x-tether-maximum-current-rating/18833/3 "2024-12-13T07:12:21Z")
Having tested the tether with a surface power supply, I can say from experience that it is impractical to go above 1 amp per conductor due to heating. We tried 100m at 2A and 330VDC and we used one twisted pair (2x 26AWG conductors) for + and one pair for -. It worked, but it’s not designed for either high current or high voltage. Fortunately, it’s easy to get a tether with larger conductors, either off the shelf or custom. ---
**Author:** ![nickbrick](https://avatars.discourse-cdn.com/v4/letter/n/3bc359/32.png) [@nickbrick](https://discuss.bluerobotics.com/u/nickbrick)\ **Post date:** [February 12, 2025, 12:47pm UTC](https://discuss.bluerobotics.com/t/fathom-x-tether-maximum-current-rating/18833/4 "2025-02-12T12:47:44Z")
Hi Tony, Assuming the cable were a suitably large enough CSA to handle higher current with minimal volt-drop. What would be the maximum wattage the FathomX boards could handle? I’ve seen a post suggesting they can handle up to 400VDC but i can’t see any max. current spec for the boards themselves ---
**Author:** ![tony-white](https://sea1.discourse-cdn.com/flex019/user_avatar/discuss.bluerobotics.com/tony-white/32/18385_2.png) [@tony-white](https://discuss.bluerobotics.com/u/tony-white)\ **Post date:** [February 12, 2025, 3:08pm UTC](https://discuss.bluerobotics.com/t/fathom-x-tether-maximum-current-rating/18833/5 "2025-02-12T15:08:14Z")
Hi @nickbrick - Welcome to the forums! The Fathom-X is ONLY for communication - while it can be used with voltage present on the twisted pair being used for signaling, things generally work better when a dedicated twisted pair is used for communication… No current should be passed through the Fathom-X board!