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Max current for OBD2 connector

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MrAl
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Max current for OBD2 connector

Post by MrAl »

Hi,

Anyone know the max current rating of the +12 and ground pins on the OBD2 connector for a 1998 v70?

For example say we wanted to run something off of the +12v supply from that connector.
I intend to run a small meter which i'm sure would be ok, but i also might want to light charge the battery though that too.
I’ve been driving a Volvo long before anyone ever paid me to drive one.
1998 v70 on the road since April 2nd, 2015
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Re: Max current for OBD2 connector

Post by wizechatmgr »

It appears it is rated (per SPEC) for 12V @ 4A, but I wouldn't try to put that much through, maybe 500mA since it sounds like you're just trying to maintain the battery.

https://en.wikipedia.org/wiki/On-board_diagnostics
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Re: Max current for OBD2 connector

Post by abscate »

On ME7 I think the OBD pulls current from the cDM and the ECU

I would not try to charge the battery through the OBD until you understand that circuit fully.
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Re: Max current for OBD2 connector

Post by MrAl »

wizechatmgr wrote: Fri Sep 08, 2017 6:41 pm It appears it is rated (per SPEC) for 12V @ 4A, but I wouldn't try to put that much through, maybe 500mA since it sounds like you're just trying to maintain the battery.

https://en.wikipedia.org/wiki/On-board_diagnostics
Hi,

Yes thanks. I dont intend to put more then 200ma though it.
I’ve been driving a Volvo long before anyone ever paid me to drive one.
1998 v70 on the road since April 2nd, 2015
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Re: Max current for OBD2 connector

Post by MrAl »

abscate wrote: Fri Sep 08, 2017 7:16 pm On ME7 I think the OBD pulls current from the cDM and the ECU

I would not try to charge the battery through the OBD until you understand that circuit fully.
Hi again,

I looked up the wiring and it looks like pin 16 goes back to the battery (+) positive terminal, and that goes through two different fuses.
The ground wire looks like "chassis ground" is pin 4.

Does that sound right? I had measured the voltages across those two pins many times in the past, but did not look them up until now. If i dont do it that way then i have to install a new wire that goes directly to the battery.

Amazingly, the 11C5 fuse is 15 amps in my car, or at least that's what it was when i bought it and still is. That i think is the smaller fuse in line with the pin 16 of the OBD2 connector (+12v) which is said to be "always on".
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Re: Max current for OBD2 connector

Post by abscate »

Snap a pic of the wiring diagram so we can confirm. You don't want to get this wrong
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Re: Max current for OBD2 connector

Post by MrAl »

abscate wrote: Sat Sep 09, 2017 1:36 pm Snap a pic of the wiring diagram so we can confirm. You don't want to get this wrong
Hi again,

Yes, and due to the concerns i am starting to think maybe install my own wire to the battery like i did in the old Hyundai. That way i can be responsible knowing exactly how it is wired as to wire size and fusing and nice heavy insulation too.

For this i would just have to find a good way to connect the wires to the battery. Last time i stuck the wires inside the battery connector but a better way would be nice.

Thanks and here's the wiring diagram i found...

I have confirmed that the 11C/5 fuse is 15 amps in my car as per photograph i took a long time ago and did not change any of those fuses ever. The writing on the fuse box lid also includes the word "Dianos" and "15A" so i think that part is right.
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Re: Max current for OBD2 connector

Post by wizechatmgr »

Could also likely use the B+ from the radio harness, also known as the memory circuit. It shouldn't be switched.

Usually if I run a battery tender/maintainer I just hook up the harness at the battery and run the plug to the side, similar to the setup folks do with block heaters. If you have one of those super volvo installed ones with the outlet on the side of the vehicle you're lucky :)

How long do you plan on this car sitting? If it is only a couple of weeks at a time the battery should be fine. If it is chronically low, then you have a charging system or battery issue. If it is going to be more than 4-5 months, I usually remove the battery and bring it indoors.
Wisdom requires knowledge as a prerequisite, but knowledge can be developed due to a lack of wisdom.
In order to learn how to fix something, you must first learn how to break it.
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Re: Max current for OBD2 connector

Post by MrAl »

Hi,

Yes it does not have to sit that long, just a few days max problem unless there is really bad weather and then it could be a full week (7 days).

It's starting to look like it would be better for me to go right to the battery with this. I have the cord from the older car i had, and now i found a way to connect to the battery without loosening the normal big terminals.
I’ve been driving a Volvo long before anyone ever paid me to drive one.
1998 v70 on the road since April 2nd, 2015
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