Johan
Off-grid energy systems enthusiast.
This post shows how I opened the case of the EG4-WP 48V 100Ah (5.12kWh) battery without damaging any cells or other electrical components. This voids your warranty. First try to contact Signature Solar to see if a less invasive solution exists. In my experience they do their best to help you.
Read this post if you want to:
Procedure:

Clearances (as measured):
If you only want to reset the BMS:
Instead of sawing the entire lid off, You could also make a small hole in the lid of the case. I recommend not using a drill (unless in a very controlled manner) because the clearance between BMS and lid is small. Instead, use a soldering stick or a router if you have one. Where to make the hole... this may very well vary 0.25in (6mm) per battery!:
@Will Prowse @electric @Trkarl @RichardfromEG4
Notes
*This happens, for example, after connecting to an inverter without pre-charging. In my case, the BMS retried connecting roughly five times (each followed by a 4-min protect-mode-time-out) with a Cotek SD-3500-148. I tried reviving the BMS by charging is 24h using a an EG4 charger: unsuccessful. SS sent me a replacement.
** the Overkill BMS may have the same cell tap connectors, but the JK BMS may be a good alternative too.
This is what it looks like inside.

What BMS is this? How to access?

Distance from reset switch to handle outer edge (the ruler's zero is right above the switch center!).

Distance from reset switch to case long outer edge.
Read this post if you want to:
- reset the BMS from being stuck in "protect" mode back to "stand-by" mode*, or
- replace the BMS by a different BMS**, or
- see what's inside
Procedure:
- First remove both plastic handle ropes (can be done fully non-destructively);
- cut the case all around using an oscillating saw (the famous Will-Prowse tear down method),
- Carefully saw right above (!) the seam (in my case this worked without touching cells - in your case it may not - it's your risk!
- The case wall thickness is 5/8in (8mm) all around (see photo).
- Apply multiple saw passes, gradually increasing the kerf depth.
- carefully pry the lid off with chisel (re-solidified debris may "weld" the lid a bit to the case's body locally).

Clearances (as measured):
- from cutting plane to cells: 1/4in (6mm); ? OMG
- between case long inner wall and cells: zero
- between BMS circuit board green top surface and lid bottom surface: 3/4in (20mm)
If you only want to reset the BMS:
Instead of sawing the entire lid off, You could also make a small hole in the lid of the case. I recommend not using a drill (unless in a very controlled manner) because the clearance between BMS and lid is small. Instead, use a soldering stick or a router if you have one. Where to make the hole... this may very well vary 0.25in (6mm) per battery!:
- 7 5/8in from the handle outer edge (see photo),
- 4 3/4in from the case long outer edge on the negative terminal side (see photo)
@Will Prowse @electric @Trkarl @RichardfromEG4
Notes
*This happens, for example, after connecting to an inverter without pre-charging. In my case, the BMS retried connecting roughly five times (each followed by a 4-min protect-mode-time-out) with a Cotek SD-3500-148. I tried reviving the BMS by charging is 24h using a an EG4 charger: unsuccessful. SS sent me a replacement.
** the Overkill BMS may have the same cell tap connectors, but the JK BMS may be a good alternative too.

This is what it looks like inside.

What BMS is this? How to access?

Distance from reset switch to handle outer edge (the ruler's zero is right above the switch center!).

Distance from reset switch to case long outer edge.
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