[Unspec]

Trying to figure out how much current the car draws while it's off. I know that a lot of ECU's stay on for 15 minutes, so I waited an hour to let the car go to sleep. I'm suspecting that the car doesn't go into true sleep mode if the hood is open, because even after an hour, measuring the current immediately blew my multimeter's fuses (10A max). What's the proper way to measure the sleep draw?

[Surly73]

Originally Posted by Unspec

Trying to figure out how much current the car draws while it's off. I know that a lot of ECU's stay on for 15 minutes, so I waited an hour to let the car go to sleep. I'm suspecting that the car doesn't go into true sleep mode if the hood is open, because even after an hour, measuring the current immediately blew my multimeter's fuses (10A max). What's the proper way to measure the sleep draw?

From your description, I'm pretty sure you're not connecting properly to measure current. I suspect you're connecting your multimeter across the terminals while in current mode, which is short circuiting the battery through your meter.

Current is measured in line, meaning in line with the battery, which means in the trunk, not under the hood.

The way to do it could be to disconnect a lead like the ground line, and reconnect that THROUGH the meter. The catch here is that when you first connect it I bet that >10A is drawn even if just for a surge, meaning it may still blow the fuse in the meter. If that's the case then you need different kinds of instrumentation. I know that when I reconnect my battery it sparks. If there's a spark, there's a decent chance it's >10A in-rush surge.

Words of warning - if you don't know what you're doing, don't do it. Batteries can supply a lot of current and accidentally connecting something, or brushing the wrong two things together, can cause damage.

What problem are you trying to fix? If you're getting "increased discharge while stopped" use ISTA to pull codes which will likely point you towards the issue.

[Unspec]

Originally Posted by Surly73

From your description, I'm pretty sure you're not connecting properly to measure current. I suspect you're connecting your multimeter across the terminals while in current mode, which is short circuiting the battery through your meter.

Current is measured in line, meaning in line with the battery, which means in the trunk, not under the hood.

The way to do it could be to disconnect a lead like the ground line, and reconnect that THROUGH the meter. The catch here is that when you first connect it I bet that >10A is drawn even if just for a surge, meaning it may still blow the fuse in the meter. If that's the case then you need different kinds of instrumentation. I know that when I reconnect my battery it sparks. If there's a spark, there's a decent chance it's >10A in-rush surge.

Words of warning - if you don't know what you're doing, don't do it. Batteries can supply a lot of current and accidentally connecting something, or brushing the wrong two things together, can cause damage.

What problem are you trying to fix? If you're getting "increased discharge while stopped" use ISTA to pull codes which will likely point you towards the issue.

Yup, I'm putting my leads where I would normally jump the car in the hood. Guess that's wrong! I know enough about electrical stuff to not hurt myself, but not enough to know how to measure things lol.

I'm trying to see how much power I need to provide for a battery maintainer. I don't have outlets in my parking space at the apartment so I wanted to use a solar panel to charge. Unfortunately it's also indoors but with 24/7 fluorescent lighting so I wanted to see if the lights could provide enough power to my solar panel to maintain the battery.

[Surly73]

Originally Posted by Unspec

Yup, I'm putting my leads where I would normally jump the car in the hood. Guess that's wrong! I know enough about electrical stuff to not hurt myself, but not enough to know how to measure things lol.

I'm trying to see how much power I need to provide for a battery maintainer. I don't have outlets in my parking space at the apartment so I wanted to use a solar panel to charge. Unfortunately it's also indoors but with 24/7 fluorescent lighting so I wanted to see if the lights could provide enough power to my solar panel to maintain the battery.

As long as you don't have a malfunction in the car, any will do. Full sleep draw will be low (just guessing 20mA - some quick googling suggests that 80mA is defined as a max acceptable upper limit). If you think about it, this current draw is always present and a 90-100Ah battery needs to be able to restart a car that's been parked for weeks. It can't be very high when things are working properly.

I'd say 2A will work, but one of the ~4A models would allow it to more quickly recover a battery which is low and get to the "floating" stage. I like my CTEK MXS 5.0 I've had about 1.5 years. I had a de-sulphating battery minder for about 15 years before that which worked OK too. I plug in overnight regularly (from every 1-2 weeks in the summer, sometimes every night in the dead of winter).

Now if you're using solar panels to direct connect and charge (I've thought about this too so that the car charges while parked in the commuter lot ) you'd just need to be careful of the output controllers - can they handle being connect across a battery and not just a load like a cellphone charger? What is the target output voltage? If they make sufficient power to charge, when would they cut off? (AGM batteries have a hard upper limit of 14.8VDC before damage) and that kind of thing.

Sounds like a fun project Some times I think that I'd like to put solar panel on the top side of the moon roof sliding shade.

[Unspec]

Originally Posted by Surly73

As long as you don't have a malfunction in the car, any will do. Full sleep draw will be low (just guessing 20mA - some quick googling suggests that 80mA is defined as a max acceptable upper limit). If you think about it, this current draw is always present and a 90-100Ah battery needs to be able to restart a car that's been parked for weeks. It can't be very high when things are working properly.

I'd say 2A will work, but one of the ~4A models would allow it to more quickly recover a battery which is low and get to the "floating" stage. I like my CTEK MXS 5.0 I've had about 1.5 years. I had a de-sulphating battery minder for about 15 years before that which worked OK too. I plug in overnight regularly (from every 1-2 weeks in the summer, sometimes every night in the dead of winter).

Now if you're using solar panels to direct connect and charge (I've thought about this too so that the car charges while parked in the commuter lot ) you'd just need to be careful of the output controllers - can they handle being connect across a battery and not just a load like a cellphone charger? What is the target output voltage? If they make sufficient power to charge, when would they cut off? (AGM batteries have a hard upper limit of 14.8VDC before damage) and that kind of thing.

Sounds like a fun project Some times I think that I'd like to put solar panel on the top side of the moon roof sliding shade.

I'm using the battery tender solar controller, so it handles most things you mentioned and is AGM safe. Also prevents discharging the battery when the solar panel is "off". I'm probably abandoning this idea, as even with a 100W panel I'm only getting like 5mA lmao. So to actually get enough current to charge my battery I'd have to spend like 400 bucks in solar panels. Not worth!

[Surly73]

Originally Posted by Unspec

I'm using the battery tender solar controller, so it handles most things you mentioned and is AGM safe. Also prevents discharging the battery when the solar panel is "off". I'm probably abandoning this idea, as even with a 100W panel I'm only getting like 5mA lmao. So to actually get enough current to charge my battery I'd have to spend like 400 bucks in solar panels. Not worth!

Check that math.

100W / 14VDC = 7.1A

EDIT: Of course we don't know how much energy you'll recover from the light actually falling on the car as opposed to direct sunlight.

[Unspec]

Originally Posted by Surly73

Check that math.

100W / 14VDC = 7.1A

EDIT: Of course we don't know how much energy you'll recover from the light actually falling on the car as opposed to direct sunlight.

Sorry, I was probably unclear. I know it's 7.1A max. But when I measured it, it actually put out around 5mA.

[Surly73]

Originally Posted by Unspec

Sorry, I was probably unclear. I know it's 7.1A max. But when I measured it, it actually put out around 5mA.

OK - so that's a function of the light available - got it

That's too bad...

[pierreye]

Don't feel it's necessary to charge the battery everyday. I only do it once or twice every year especially when I'm on long holiday (which been scraped for this year due to Covid-19).