Replace batteries

I wanted to send my Trident back for a battery replacement.
The message I got back from Sofar Ocean Tech. was:
“We unfortunately are no longer offering repairs for the Trident as of 2021. We are only providing replacements Tridents for customers under warranty as well as extra accessories like motor kits, chargers, side bumpers, etc. I am sorry for the inconvenience.
Best Regards,
Conor Randall”
So I was wondering if anyone has replaced the batteries on their own?
And how hard is it?
Or other possible options?

Here’s some information on the batteries from my disassembled Trident, but probably won’t be much help for ‘exact’ replacement batteries unless TENERGY still sells Item No : 34136.

Label on Trident batteries.
TENERGY Item No. 34136
Li-ion 18650 10.8V 4.4Ah (47.52Wh)
Rechargeable Battery Pack with PCM (Protection Circuit Module)

I’ve heard the red and black wires are positive and negative.
The two white wires are the outputs from a thermistor for temperature monitoring.


Images :
Trident Battery Packs.jpg with 3 18650 for reference
Trident Battery Connector.jpg
Hull Bottom No PCB
Cracked camera lens on Trident - #15 by webhoppery
The batteries are placed in front of the 2 thrusters.

How long did your batteries last? Your usage scenario? Charges?


Trident Battery Packs

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thanks for the information!
What did you learn from taking it apart, was it difficult?
I would think we should post a replacement guide on how to replace the batteries.
Did you take pictures of taking it apart?
I have lots of equipment and enjoy the challenge.

I second the need for a battery replacement guide!

@John_Stager I had sent my dead Trident to Sofar to fix and it was returned disassembled (per request) with a package of 25 loose screws and 2 washers.

Allen wrenches needed for disassembly :
2.5 mm for hull separation
1.3 mm to remove the PCB to get to the battery packs

The link above to the “Cracked camera lens on Trident” has an image of the hull bottom with the PCB removed. It shows the locations of the 20 screws holding the hull halves together.

With the hull separated, the PCB has 1-1.3 mm mounting screw by the camera mount.

The bottom of the PCB has 3-3 pin connectors for the motors, and a 4 pin connector for the external temperature? and pressure? sensors.

Questions / Notes :
Be gentle removing the cables. My front LED PCB connectors broke the solder joints.
Can we get the battery packs from TENERGY?
If there’s no thermistor in the battery packs, what will the Trident SW do?
The torq and sequence for tightening the hull screws?
Negative pressure test for leaks?
Where the 2 big washers go?
The 5 extra screws?

Good luck!


I added a u-tube video showing my tear down of the trident

hope this helps with how to replace the batteries


Thank you John…this is pure gold.

Thanks again webhoppery…more pure gold.

I have reassembled the Trident
see utube video
I cannot pull and hold a vacuum on the finished unit
Any ideas on how to find the leak, I would appreciate?
Maybe I should add some Permatex thread sealant around the screws?
and add some grease on the o-ring around the perimeter of the unit?

@John_Stager My hull screws had what looked like a bright blue dab of LOCTITE’s TITE’N ? on one side.

Just to be sure, maybe check the vacuum hold when disconnected from the Schrader valve?

I see why you ‘enjoy’ the challenge - LOTS of ‘toys’!

Wish Sofar support would chime in with some of their assembly procedures.

Thanks John_Stager,

I appreciate the detailed description of your assembly procedures.

Just as webhoppery has suggested, and I am sure you have already considered it, the leak may be downstream of your hull.

If the leak is caused by one of the seals, the only value I can add is to suggest careful reassembly after applying silicone grease to all of the seals and after checking for proper alignment of the seals and their mating surfaces. OpenROV had some QA issues with seals and flooding at the beginning so I suspect the task of resealing our hulls is going to be a challenge for us all. Make sure you check for any potential bridging of the seals by contamination.

I am also giving thought to the potential of using liquid silicone seals similar to these ones for engines as well. In my experience, seals are always single use items and the large hull seals are likely to be set with small imperfections from the hull flanges that don’t perfectly align the second time around. Alternatively, we may be able to find a supplier/distributor for the original seals as a kit.

Could it be leaking in the Shrader valve thread root?

I am still working at it.
Here is a u-turbe video of the battery cases I made, that might work…

My main electronics board still does not show the correct leds on the tail when the batteries are full. So I think the water has damaged my main elec. bd.
The tail bd. has the IMU sensor and that is working, but that could also be bad.
Has anyone decided to scrap their unit and would sell the electronics?

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Since you can apply power, any thoughts on the Debug port ( Tx, Rx, GND ) by the SAMD21? I happened to notice it below the 8 pin connector in your video.

The battery holders sure printed out nice. What did you use?

I have an Maker Gear M3 printer. I made a plexi-glass case to enclose it. Case prevents drafts. Printed in Gizmo Dorks ABS filament. I have had the printer for a couple of years and had very good luck with it.
maker gear m3.jpg

Yes, I saw the debug port and would think you could hook up a serial terminal app. (like Realterm) for some kind of diagnostic info. But have not tried that.