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Y’all might want to try this trick to keep your battery being charged all the time. It worked on my HEV.

Keep your headlights turned on all the time. Not on automatic, but on. The car automatically turns them off when you turn the car off so you don’t have to worry about them draining the battery.

On my HEV, I found the voltage fluctuated a lot from high 11 volts up to over 14. Low voltage is not good on an amplifier so I started experimenting. After a while I found that when your headlights are on, the battery voltage stays at above 14 volts! Perfect!

Try it on one of the PHEV or a BEL and let us know what it does.
 

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battery died (3v) so i charged it and it’s running again but it’s only holding around 12.3v so i think it needs to be replaced.
took the car to the dealer where he tested the battery, for no charge by the way, and told me it was fine; good for my wallet, not so good for my peace of mind because now i’m worried about vampire discharge. i told them i’d monitor the voltage.

since then no problems but in an attempt to duplicate the failure i charged it up to 12.6v and then let it sit for 30 hrs during which the battery varied from 12.3v to 12.5v except for a single reading of 12.7v. isn’t 12.3v like a 30% discharge? is this normal? how low can it go and still start the car?

when i started the car the battery saver notice came on which maybe accounts for the 12.7v reading. what is the threshold level for the battery saver to kick in?

i also measured the current with the car off between the positive battery terminal and the cable and got 0.5 mA, which x30hrs is 0.2 Ah. (the tsp regarding the rear door locks draining the battery requires putting the car in sleep mode which of course i didn’t do since i have no idea what it is.) find it hard to believe this would drop the voltage 0.3v

found an internet post that said as a rule-of-thumb SOC (state of charge) could be directly related to remaining Ah. so if a voltage drop from 12.6v to 12.3v takes it to around 70% that would be 31.5 Ah (45 Ah x 0.7) remaining. where did my other 13.5 Ah go?

all things considered, i can’t help but think that i caused the problem. what’s aggravating is that i just can’t imagine what i did.......
 

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I'm not sure of the exact number but I don't think you need too many volts at all, just enough to get the computers running. I'd like to know the number too LOL. How many volts do the computers need to fire up?
 

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My dashcam shows the volt before I start my Niro, it is roundabout 11.4 V ... I see this over more than one year and no probs to start the car ...
Here it was 11.5 V:
6827
 

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I'm not sure of the exact number but I don't think you need too many volts at all, just enough to get the computers running. I'd like to know the number too LOL. How many volts do the computers need to fire up?
Computer chips have very tight limits of operational voltages. Most chips are either 5VDC or 12VDC. They'll tolerate about 10-15% high/low, but that's about it. A 12V device likely either won't work or behave strangely at about 10 volts.
 

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Computer chips have very tight limits of operational voltages. Most chips are either 5VDC or 12VDC. They'll tolerate about 10-15% high/low, but that's about it. A 12V device likely either won't work or behave strangely at about 10 volts.
Thanks for the info. I guess the days of hitting things with a hammer are over. :D
 

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isn’t 12.3v like a 30% discharge? is this normal? how low can it go and still start the car?
It is an ominous level suggesting impending failure in an alternator equipped car. From other forum posts, it appears something like 12.2/12.3 volts is the trigger threshold. Lots of reports of sub 12 volt readings not triggering. The issue with lead acid batteries is that such repetitive low voltages insure damage and early battery failure compared to ICE alternator equipped cars. Again from many reports on many brands of EVs, the cure is regular maintenance with a smart trickle charger to reverse damage.
 

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So has anyone tried leaving their headlights on so the DC-DC converter keeps the battery voltage up the entire time the car is turned on?
 

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Computer chips have very tight limits of operational voltages. Most chips are either 5VDC or 12VDC. They'll tolerate about 10-15% high/low, but that's about it. A 12V device likely either won't work or behave strangely at about 10 volts.
That's true for individual ICs but likely not the case for the whole system. I guarantee that the ECU itself runs on either 5 or 3.3 VDC and there is a DC-DC converter that drops the 12V accessory bus voltage to the level required by the actual chips. I would be surprised if the ECU wouldn't run just fine on as little as 8-10 volts. (Source: I design power supplies for a living. 😁)

Now, whether the fuel injectors would fire effectively at that level is a different story.

This is one reason you can still roll start a modern car with a manual transmission. Even if the battery is too low to crank the starter it will usually still be enough to run the ECU so once the engine is turning it starts right up.

Chips that run on 12V or more are generally things like amplifiers and drivers. Most logic circuits use much lower voltages to reduce power and heat. Levels as low as .8V are common in modern circuits.
 

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Just chiming in with a similar problem. I have a 2019 Niro PHEV and have no issues unless I leave a door or the rear hatch open. If I do that I'll have a dead battery in something like an hour. I measured the parasitic draw with door and hatch open and it's about 5A. With doors closed (and waiting for the interior lights to go out) it's around 0.5A. I have the battery saver + enabled and see the message upon startup occasionally that it was used, but it definitely doesn't work when leaving a door open. It's been a real pain on camping trips where I'm in and out of the vehicle without running it for a couple days. I have a lithium jump starter now but climbing into the back of the car to release the trunk can be problematic with a packed car (the battery is low enough where the fob won't open the trunk. It's also fun when I trigger the alarm in the whole unlocking/jumping process).
Brought it to the dealer today for 30k service and asked them to test the battery and look at parasitic draw. I don't think they did a load test, though, and they definitely didn't look at parasitic draw. I'm not sure what battery test they do for the standard multi point inspection... basically voltage test? It passed whatever they did.

I probably need to have a proper load test done and I'm thinking that swapping in LEDs for the interior lights would lower the draw to a point where I don't have to be so paranoid about leaving a door/trunk open!
 

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You can jump-start from the front, if necessary ...
 
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