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Add a battery?

I've bought and fitted the OVMS unit to my Kia e-Niro and as I'm concerned about draining the 12v battery I've spliced the OBD power wire to a fuse that's powered on when the car is turned on or charging.  This works fine and I'm happy with it, however I'd like the OVMS unit to remain on a little longer after power off.  To me the obvious way would be connecting a battery to the unit that is charged via the connection when it's there and can run the unit until flat when it's not.  I'm not sure exactly what unit is powering OVMS, is there an addon for it to do this?

Stanton's picture
I think you have a situation

I think you have a situation of "2 wrongs don't make a right".

Without more info, I suspect you have a weak 12v battery (that probably needs to be replaced)...and are trying to compensate with an (ill-advised) addition of another battery (which will also eventually need to be replaced) plus additional circuitry. My advice is:

1) get a better/newer 12v battery (I replaced my lead-acid starter battery with a LiFePO4 starter battery), and

2) reduce the power-down/time-out parameters in the OVMS configuration (for WiFi and cellular)

inf0mike's picture
You should also be aware that

You should also be aware that the issue is not really that the OVMS unit drains the 12v battery as its power draw is very low.  The actual problem on the Hyundai / Kia vehicles is that the OVMS keeps several of the cars ECUs active preventing them from going to "sleep" properly and in fact the cars own systems drain the battery.  Adding an additional battery to keep the OVMS alive will probably not help your situation.  SInce the more recent software updates in the car, the "battery saver" option that used to exist in the menus has been replaced with permanent feature where the car wakes up every 4 hours to top up the 12v battery so the problem might not be as big a concern as it used to be.

I have OVMS on a Hyundai Kona (which is essentially the same as your Niro) and I just have a simple switched OBD cable to power the OVMS on and off.  I power it on when I get in the car and power it off when I am back home.  It is safe to power on at the beginning of a day of running about and leave it on all day, powering off at the end of the day (for example):


Switched OBD

How can you make switched OBD?

Thanks for the advice.  In

Thanks for the advice.  In terms of top up, I see my e-niro wake up every 24 hours for 20 mins to top up the 12v battery, not every 4 hours.  Perhaps I don't have the latest firmware applied, as I've got a 2 LR I don't believe I can patch it myself and need a dealer so will investigate.

The reason i've patched into a fuse that only powers the unit on drive and charge is my primary interest is SOC which this gives me fine, i'm not sure that in all honestly I'm missing much else, my main interest was in the anti-theft piece around if GPS detects movement without the car being started and a small battery addition to the OVMS unit would do that in my view.  I've heard a lot of anecdotal evidence showing that the e-niro gets drained by OVMS on the forums, so whether it's caused by a small battery or bad design in a one month old car it's not something i'm really looking to run into :).

Stanton's picture
Now knowing that it's new car

Now knowing that it's new car/battery we're talking about and the "power on" behavior of the the Niro...I think it's safe to say that the OVMS module isn't really the source of the 12v drain.

Having said that, I still recommend visiting the "power settings" page of the OVMS config where there are timers to power down/time out the WiFi and cellular functions.

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