A while ago, I’ve bought the ISDT C4 EVO USB-C-powered battery charger to replace my MAHA C9000 (of which there seems to be a new “Pro” model available). The ISDT charger gets regular firmware updates which add new features and optimises the charging modes for different battery chemistries.
Up until firmware 1.0.44, everything worked fine. Then, in late September 2024, firmware 1.0.46 came along. Suddenly, the charger showed some “Unknown Error 0x400” messages whenever it was discharging a battery and the battery was empty and thus the voltage fell below 0.9V. Often, it would also reset the slot and think the battery was just inserted. Resulting in weird loops and the charger beeping wildly. Only the plain simple “charge to full” (with the “discharge first” option disabled!) would still work, all the other flashy features were useless.
Version 1.0.46 has since been retracted and there’s a 1.0.45 now showing up as the “latest” version in the ISD GO app. However, downgrading to that (using the new “Firmware Repair” option) didn’t help at all as the same problem still exists in that version. And the firmware tool doesn’t allow to select any earlier version.
So, I went on a mission to find a way to downgrade to 1.0.44 – the last known good version.
The same hardware is also sold under the name Kyosho Speed House Multicell Charger evo. And for some reason, this one has ALL the features enabled for some years now. The firmware version for that one is 1.0.0.10 from June 2022. It might be, that ISDT made a bit of money by licensing the charger incl. all features to Kyosho while selling it with a limited feature set to their own customers.
This also meant that there was some desire to flash the Kyosho firmware to ISDT devices amongst its user base.
Kyosho’s tool detects the “brand” and refuses to flash its version.
But, it appears that someone patched an old version of the ISDT update tool for Windows and made it ignore whatever currently is on the device. You just put a file Firmware.fwd into a folder and it will flash it. This Reddit comment pointed me to 𝕏-formerly-known-as-Twitter user @Westhill_Shinya. In his profile, there’s a link to a Google Drive with the patched updater (already including the Kyosho firmware). Just download and unpack.
Now to the tricky part: Where to get the older C4 EVO firmware file? For some reason, ISDT restructured their website a while ago and since then, only the very latest version is easily available. You can get a JSON overview of all available firmwares for their various devices from https://www.isdt.co/down/firmwares/firmwareDownloadList.json . Find the URL for the C4 EVO and put it into the Wayback Machine at the Internet Archive – like this – then just select the desired date and download the archived firmware. The ones from July and September 2024 are version 1.0.0.44.
Finally, get a Windows system (or VM), put the patched update tool on it, put the firmware file into the Firmware folder of the updater and run it to flash it to your charger. Done! It’s finally useable again.
(Or use the opportunity and flash the Kyosho firmware with which a lot of people are pretty happy, too.)