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Kona PremSe64k 2020+bluelink +ohme
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Having just met with yet another flat 12v battery last night I went back to my manual and it says to disconnect the battery if left for a long time, which I now consider 15 days or more of very little or no use. And so, given lockdown will continue I have resolved to recharge the car tonight and then tommorrow disconnect my 12v battery and reconnect it when next needed.

Now that's okay for me. I don't mind going under the bonnet and doing what's necessary. However I have just had a thought that it would be perhaps useful to have a remote device to flip a relay connected to the battery that disconnects it and reconnects it.

I came across this one on ebay
that seems to do much of the job.

Has anyone else done this kind of modification? Does it work? Or is better just to K.I.S.S?
 

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I believe that in addition to a dashcam you also have an OBD2 adapter . You may not know that stageshoot reported in another forum that:
"I can tell you from experience that if you leave anything connected to the OBD Port on the Hyundai Kona EV it will flatten the 12v battery in less than 12 hours, not because of the item connected to the OBD, but because it keeps all the other computers in the car awake thinking there is diagnostics going on..."

You have indicated a discharge time of 15 days so his discharge time of 12 hours doesn't match, but his explanation of a discharge process might apply for your issue...
 

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Nissan LEAF30
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Does it come with the tie wraps shown locating it in the pictures? :rolleyes:
You can get manual cut-off switches which do the job very effectively but are also known to fail. Frankly in your situation I'd just charge the 12v weekly when not driving the car.
 

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Hyundai Ioniq 28
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However, I have just had a thought that it would be perhaps useful to have a remote device to flip a relay connected to the battery that disconnects it and reconnects it.
As you say, that gizmo would stop the 12v DC battery running down from some kind of vampire drain over time. Unless, of course, the car side of the remote unit itself drains too much current as it sits there attached to the 12v battery for weeks waiting to be contacted by the drivers' fob. Probably a tiny drain as it's on standby but who knows over time.

I did consider using a simple isolator kill switch such as used by classic cars and race cars but on reflection that would be difficult to organise as the car wouldn't lock if the battery was disconnected and the bonnet closed. Even worse, you would have to get back in by the physical key and open the bonnet to re-energise the 12v battery. In an Ioniq that is a right faff as you have to force off a cover to reveal the keyhole and then an even worse fiddle to get the cover back on.

So I went back to my usual maintenance regime but brought the monthly smart charge connection down to fortnightly.
 

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KIA Soul EV 64kWh
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Having just met with yet another flat 12v battery last night I went back to my manual and it says to disconnect the battery if left for a long time, which I now consider 15 days or more of very little or no use. And so, given lockdown will continue I have resolved to recharge the car tonight and then tommorrow disconnect my 12v battery and reconnect it when next needed.

Now that's okay for me. I don't mind going under the bonnet and doing what's necessary. However I have just had a thought that it would be perhaps useful to have a remote device to flip a relay connected to the battery that disconnects it and reconnects it.

I came across this one on ebay
that seems to do much of the job.

Has anyone else done this kind of modification? Does it work? Or is better just to K.I.S.S?
There is an ON/OFF switch in the fuse box.
Could this be used to reduce battery drain when the car is stored?
I believe it is used in this way for shipping
 

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Hyundai Ioniq 28
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But if you fill in the compatibility chart it says:
I can't see any reason for it to be incompatible. It's only affecting the 12v DC battery and not the car itself. And would work just the same inside any car, or out of it as well in fact. The description also says this - " Remote Receiver Standby Current: 0.0085A ". So my query about it draining the battery itself seems to not be a problem over 15 days as standby drain is negligible.

However, I do see a potential problem. As its a latching relay that is used to maintain the connection of the battery to ground then that latch will have to remain engaged at all times. If the latching unit fails at any time the negative lead will disconnect. And that could happen in the 3rd lane of a motorway at a very inconvenient time. I would favour the KISS route because of this alone.
 

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There is an ON/OFF switch in the fuse box.
Could this be used to reduce battery drain when the car is stored?
I believe it is used in this way for shipping
This doesn't reduce the passive draw by much - from distant memory when I was doing measurements it was something like 25% off a 20mA or so baseline draw. It may be more functional on models that have telematics.
 

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What are the implications on your insurance if something were to happen and it transpires that your alarm wasn't active?
 

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30KW Tekna (2017)
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Has anyone actually not driven their car for at least 15 days in this lockdown? Your allowed to shop and exercise?
I mean if your car battery needs disconnecting after 15 days, its time to look for a new car make I think! Thats just not reasonable for the population as a whole.
 
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