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Because I have enough 2512 package resistor inventory, but the resistance value is different from that of the existing module board. I re connected five 22r resistors in parallel with the total resistance value of 4.4 ohm. The 2512 resistor is still very expensive to purchase. These modules are not large in number and are welded by hand

Thanks Stuart, not sure I completely understand, I have the relay set to normally open, setting to normally close will just trigger the shut, maybe I can try using 2 relays from one to the other, hopefully the reset does not set the pin to high simultaneously

It makes no difference what the rules are set to when the power is removed from the controller. The relays will be opened, if that is how you have them physically wired. When the controller resets, the board is momentarily in the no power state and thus the relays are opened. You choose the power off open or closed state via the physical wiring. That wiring should be such that when you yank the power from the controller loads and chargers shut off to protect the batteries.

Again, the software settings are totally irrelevant when the board powers down or the CPU resets.

Isn’t this the real problem? The controller should not reboot when wifi is dropped.

Maybe your problem is similar to one that I had. I found that with my wemos clone, it did not have enough power from the voltage regulator when the wifi was first turned on at startup. This caused the relays to open, which killed the power to my router and thus the controller booted without a wifi connection.

On a related note, I modified the code to switch to AP mode when the router is not there so that I can find it from my phone and see the battery status.

So yes, I would be happy if we had to option to disable the controller from rebooting if it cant find a wifi signal, Can someone tell me where in the code that vaule is and I am happy to change it.

As @John_Taves mentioned, this could be a wemos clone issue. When the wemos loses WiFi I think the chip increases power to the WiFi antena to search for the signal.

This seems to reboot some clone devices with incorrectly sized power regulators.

Hey Stuart, so is there nothing in your code that issues a reboot ?
I have a PRO on it’s way and hopefully this will solve my intermittent WIFI issues, I’ll keep you posted

I think it reboots if you change the mqtt or influx settings, but that’s all.

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Clarification for future readers of this thread…

The “physical wiring” connections mentioned refer to the normally open and normally closed
(often abbreviated NO and NC) relay contacts.
the term normal denoting the relay in an unpowered state.

which is accomplished by using the normally open contacts.

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Adding to that, as somebody who’s spent a large proportion of their professional life doing industrial controls and automation, this is a primary consideration of any control scheme, you must design it - as far as possible - to “Fail Safe”, meaning that the unpowered state is that which is safe, or if you can’t be certain of that, the least likely to have dangerous consequences.

This is why motor starters always drop out when the mains fails and don’t restart automatically, but emergency lights are normally held “off” by a mains-powered relay (or equivalent) and the light comes on when the mains fails.


How to deal with the problem that when there is a load, the single battery undervoltage control relay disconnects the output. Because the load disappears, the voltage rises again, and the relay acts again. As a result, the relay is always in oscillation state

And overvoltage should also have this problem!

Sure, please drop me a PM

We already stock the module boards in the OpenEnergyMonitor store. We will have stock of the controller boards in the next week or so

Are your cells dropping that much when under load? Are the cells matched to the expected load ?

Hi Huey, just saw you post for some spare controller boards, i’m after some. Could you pm me?

4 posts were split to a new topic: Module reports external temperature when no sensor is connected

Small capacity battery, voltage drop faster

Found a software limitation “Pack over voltage (mV)” 65500. I have 20 cells 18650 = 84000 mV
When you enter a larger value, it writes what has been saved, when the page is refreshed, it writes other different numbers.

That was raised a couple of days ago, can you please raise a bug on github.

Thé system was originally designed for 48V usage, but does work with higher voltages.

Many also talked about the problem of turning the relay on and off at the voltage limit values. In many systems, this is solved by two values. The first value is disable, the second is enable. Thus, by spreading these values among ourselves, we get rid of the problem of relay bounce.

Did you ever solve your issue with the CRC errors?

Similar setup to you, works fine when running on mains USB PSU, but get a few CRC errors when running on a stepdown converter connected to the batteries. Tried multiple converters and still same results.


As others have pointed out it could be your batteries, but yes, the rules need to have a recover value to prevent the oscillation. I made a version that had that with the rules, then rewrote that to be less generic. I don’t have rules, so much as I have max/min and recover settings for cells and the pack and temperature. Then you designate your relays to be either load or charge, and the logic of the code does the rest. You can also set the relays to respond to state of charge, but that’s only possible if you are monitoring current, which I am doing.

I don’t think I have the rules style code anymore, but I committed the one I am using to