Geyserwise Charging/DC Circuit?

Has anyone traced out the Geyserwise 12V charging circuit from PV to battery and load?

The reason I ask is that my batteries don’t last more than about two years and I thought it’s because of the heat in the ceiling. Today I noticed the wall unit flashing due to a ‘low’ battery and realized that even with Mains connected the unit seems to run off the battery. This means it cycles 365 times year and two years is about right for a LA battery to die from daily cycles + heat.

Am I wrong in my assumption? Maybe I can do better by using a 48/12 DC-to-DC converter and use my house battery to power the unit and disconnect the dedicated small PV panel. Cabling is just a bother all the way up to the top floor.

*It’s a pity they don’t save settings in eeprom to keep the values after a power failure - I would have paid extra for that.


As far as I’m aware the battery is only used during power outages. It draws very little current.
The battery is charged whilst the mains is on…

Correct, it seems to be the case.

I forgot that my supplier has the ability to disconnect the geyser remotely which was the case last night. This morning at 5am it was On again. I would still like to see the charging circuit if anyone has gone through the hassles of tracing it out.

Which model do you have?

Geyserwise Max with the 12V pump.

Here is something interesting I found after I discovered an old Geyserwise TS in my garage.
First a disclaimer: In providing this information I do not in any way attempt to reverse engineer the designers intellectual property. The information provided is purely for self-use and possible improvement due to constant load-shedding and better battery management.

Ok, so that said. The circuit diagram of this old unit seems to be a simple 12V regulator circuit, there are no other battery charge stage other than an attempted storage or float stage. Voltage measured on my bench is actually 11.93V which I think is a bit too low to charge the battery properly, even as a float/storage charge. Current is very low, I suspect nothing more than 800mA max.

From this old TS model there is only 5V path from the PSU/MCU board to the relay board where the AC PSU is. This shows that it will not charge the battery (12V) using mains and rely solely on Solar to charge the battery. With multiple load-shedding stages and a possibility of a few overcast days I think the battery could drop in voltage to level that is not desirable. It does however provide a 5V rail from the AC supply hence my unit (with the dead battery) being powered at night while the grid is On.

My idea is to bypass the PV panel and connect a DC-to-DC (48/12) to my house battery and then connect the Geyserwise to the output set to 12V. This way it will, nearly always, have power and charging becomes a non-issue.

If anyone could share similar info on the Geyserwise Max model to see if it uses a similar, or different circuit, that would be great. I hate climbing in to the ceiling at +40 degrees C and fiddle around there in the dark and dust.

Edit: I managed to get hold of the main board also - good thing I horde old stuff. It seems the 5V does in fact NOT connect directly to the Relay/PSU board other than through an opto-isolator probably for some status updates. The MCU/PSU is totally independent. The battery should last through a good few days without sun as it’s only the MCU on there. It just needs to charge a bit ‘better’ than 11.93V.

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