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Hi

Ioniq 2020 38kWh Premium EV.
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A few weeks ago I had the dreaded 12v drained issue. Since then I have fitted a BM2 monitor and have seen some interesting behaviour. In particular my Ohme was charging the car and reported it didn't reach 100% but the car had, when I looked at the 12v chart it consistently seemed to be doing something to drain the battery repeatedly. I have since disconnected the Hyundai login from the charger and not seen the same graph on the BM2. I am wondering if the Ohme was polling the car repeatedly and draining the 12v?

In the meantime the 1st 12v drain was never identified and the dealer says the battery is fine. I have considered fitting a bigger battery as clearly these 40ah can drain very quickly under certain circumstances. I have found a 56ah that seems to fit for £128 and was wondering if anyone else has tried a bigger capacity battery and did it help with 12v reliability?

Thanks

John
 

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A few weeks ago I had the dreaded 12v drained issue. Since then I have fitted a BM2 monitor and have seen some interesting behaviour. In particular my Ohme was charging the car and reported it didn't reach 100% but the car had, when I looked at the 12v chart it consistently seemed to be doing something to drain the battery repeatedly. I have since disconnected the Hyundai login from the charger and not seen the same graph on the BM2. I am wondering if the Ohme was polling the car repeatedly and draining the 12v?

In the meantime the 1st 12v drain was never identified and the dealer says the battery is fine. I have considered fitting a bigger battery as clearly these 40ah can drain very quickly under certain circumstances. I have found a 56ah that seems to fit for £128 and was wondering if anyone else has tried a bigger capacity battery and did it help with 12v reliability?
It's likely that every time the car is actively polled - whether by you using the app or a 3rd party system like Ohme (which polls the same API as the phone app) various ECU's are woken up in the car to retrieve the data to send back, and this will put an increased load on the 12v battery. This is certainly the case on my Leaf - you can even hear some relays clicking under the bonnet when you poll the car with the app.

I don't have an Ohme but at one point I was considering doing some scripting to emulate what the Ohme does - polling the Nissan API for my car for charge state periodically and sending a command to my EVSE to stop charging when a desired SoC is reached.

Foremost on my mind when developing this was the importance of not polling too often and not polling when the car is not actively charging to avoid discharging the 12v battery. So ideally any system doing this would need to know whether the car was charging or not before starting to poll the car. I would hope that the Ohme would do this and not just blindly keep polling because the car is plugged in even if the car has finished charging and is no longer maintaining the 12v battery, but who knows.

While I did get a proof of concept working for my system I abandoned it because the Nissan API wasn't reliable enough to rely on and ended up using a timer based setup instead.

If you're having problems with the 12v battery running down on your car and disabling the Ohme login for the car has made the change you've noticed, I'd be inclined to not use that feature, at least for a while while you gather more data from the BM2. Perhaps it isn't implemented very well.
 
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