positive battery cable

**synamin** · 05-29-2018, 12:59 PM

Back story: I went to go change my battery terminals, cut off both neg and pos battery cables from current terminals. then put it on a new terminal and went to put everything back together. Now the pos cable wont reach the battery lol.

I was going to extend the cable with a butt connector but somebody told me that it may be smarter to replace the whole positive cable and now that’s what i want to do . i need help figuring out how to get it off

**superj** · 05-29-2018, 01:58 PM

that cable goes all the way to the front so it will be a lot cheaper to do a butt connector, or something like that.

if you can buy the complete cable from another 325 e30, you will be ok though. it runs down under the carpet and comes out but the battery tray in the engine bay, if I remember right though, so its a lot of stuff to put a replacement cable in

**JamieG296** · 05-29-2018, 03:30 PM

Originally Posted by superj

that cable goes all the way to the front so it will be a lot cheaper to do a butt connector, or something like that.

if you can buy the complete cable from another 325 e30, you will be ok though. it runs down under the carpet and comes out but the battery tray in the engine bay, if I remember right though, so its a lot of stuff to put a replacement cable in

Just a thought..... the butt connector could cause a fire because you aren't suppose to splice heavy gauge wire like that. Are you? I mean I know it would be a pain to run it from back to front but it may be worth it to do it right. Again just a thought, if I'm wrong then I apologize.

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**synamin** · 05-29-2018, 03:56 PM

Originally Posted by JamieG296

Just a thought..... the butt connector could cause a fire because you aren't suppose to splice heavy gauge wire like that. Are you? I mean I know it would be a pain to run it from back to front but it may be worth it to do it right. Again just a thought, if I'm wrong then I apologize.

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m
i heard the same thing. which is why i’m leaning a little more toward changing the entire cable.however he’s right about it being a lot of work, i followed the cable through the back seat and i got to take off a lot of stuff to get to where the cable leads

**JamieG296** · 05-29-2018, 03:59 PM

No doubt, I know when I was doing my rear diff and subframe bushings, I seen the cable running up toward the front under the back seat. It will be a pain for sure.with all of the stuff in mine, I'm waiting to have to do that.
I was reading jimlevies post about e30s and he was talking about having to replace a wiring harness. It won't be long with all the crusty plugs for me I'm sure lol.

Originally Posted by synamin

m
i heard the same thing. which is why i’m leaning a little more toward changing the entire cable.however he’s right about it being a lot of work, i followed the cable through the back seat and i got to take off a lot of stuff to get to where the cable leads

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**synamin** · 05-29-2018, 05:44 PM

Originally Posted by JamieG296

No doubt, I know when I was doing my rear diff and subframe bushings, I seen the cable running up toward the front under the back seat. It will be a pain for sure.with all of the stuff in mine, I'm waiting to have to do that.
I was reading jimlevies post about e30s and he was talking about having to replace a wiring harness. It won't be long with all the crusty plugs for me I'm sure lol.

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does the positive cable connect to the wiring harness? i’m not too sure how all that wiring stuff works lol i’m learning as i go

**JamieG296** · 05-29-2018, 05:47 PM

I don't believe so, no. I believe it is just a solid red battery cable. It does not tie in to the harness in thst way.
Sorry not trying to confuse you. These cars are older at this point and all my plugs are beginning to break apart as I unplug them to make other repairs. The more that break, the more parts o have to source to repair. I wish I could just buy the plugs I need and a tool to remove the pins and replace the plugs.

Jamie

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**tomstin** · 05-30-2018, 07:50 AM

Originally Posted by superj

it runs down under the carpet and comes out but the battery tray in the engine bay

I've done this and luckily my interior was out at the time. The real patience test was getting the cable through the firewall grommet. But you don't want to mess with the main power lead, do it right and replace the cable.

**superj** · 05-30-2018, 09:03 AM

I know when I have previously pulled those, I had already removed the interior so it wasn't horribly bad

**somecarguy** · 06-01-2018, 08:52 PM

I would consider adding a circuit breaker which will serve as a junction, give you a convenient cut off switch and provide some additional measure of safety.

**richardodn** · 06-02-2018, 08:38 AM

There are actually 2 wires that run from the battery (+) post in the trunk. The main heavy gauge lead and the secondary lead with the fusible link. These both run to a junction block on the firewall and each have their own binding post on the block. The primary heavy post then has a lead that goes to the starter and another to the fuse box. This is where most of your car is powered from. The secondary post is where all your engine electronics are powered from.

As an aside, any aftermarket electronics that need constant power should be tied in to the primary post with their won fuse as near to the post as possible. Don't tie in aftermarket electronics on the engine electronics post.

**richardodn** · 06-02-2018, 08:43 AM

Originally Posted by somecarguy

I would consider adding a circuit breaker which will serve as a junction, give you a convenient cut off switch and provide some additional measure of safety.

I doubt you'll find a breaker big enough to handle the starter load. Something like that might be sufficient for the line supplying the fuse box but is largely unnecessary.

**somecarguy** · 06-02-2018, 10:12 AM

The breakers are designed for inductive motors and have a curve on which they trip. Meaning they do not trip with the brief starters load. I have one installed in my Alfa and it works fine, I doubt the starter on the low compression BMW draws that much more but you could upsize it if you wanted to

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**modifiede30** · 06-02-2018, 11:05 AM

I have mine fully apart if you need a pic of where the wire runs. I'd suggest installing a master cut off switch in the trunk and then using a small length to connect from the switch to the battery - it'll be a lot less hassle and if you're ever worried about theft, its an easy way to completely disable the car while not around. It'll cause you to lose all your memory info in the car - clock, radio, etc., but depending on frequency might be worthwhile. I just finished gutting the interior to install my kill switch and track interior parts so the main cable is pretty easy to see where it runs to/fro.

**richardodn** · 06-02-2018, 04:25 PM

Originally Posted by somecarguy

The breakers are designed for inductive motors and have a curve on which they trip. Meaning they do not trip with the brief starters load. I have one installed in my Alfa and it works fine, I doubt the starter on the low compression BMW draws that much more but you could upsize it if you wanted to

Cool!

**somecarguy** · 06-02-2018, 04:42 PM

Kill switch = breaker in my suggestion.

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**richardodn** · 06-03-2018, 12:23 PM

Originally Posted by somecarguy

Kill switch = breaker in my suggestion.
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Note that any true kill solution for the trunk mounted battery would have to be a 2 pole solution. One for the main power lead and the other for the engine electronics.

**synamin** · 06-10-2018, 11:05 AM

Originally Posted by modifiede30

I have mine fully apart if you need a pic of where the wire runs. I'd suggest installing a master cut off switch in the trunk and then using a small length to connect from the switch to the battery - it'll be a lot less hassle and if you're ever worried about theft, its an easy way to completely disable the car while not around. It'll cause you to lose all your memory info in the car - clock, radio, etc., but depending on frequency might be worthwhile. I just finished gutting the interior to install my kill switch and track interior parts so the main cable is pretty easy to see where it runs to/fro.

could you please post pictures?

**somecarguy** · 06-10-2018, 03:42 PM

FYI, the trip curve

**mountainclimber** · 04-01-2022, 05:50 PM

There are two cables that connect to the positive terminal of the battery. What do each of them do?

One of the cables is broken and the battery is dead. I had the battery replaced a year or two ago, but the car has been sitting for a couple months in the cold. When I jump the car it starts and runs fine.

Is the dead battery a function of the broken cable, the battery, alternator, or something else?

**82eye** · 04-02-2022, 10:39 AM

there is a small constant draw on e30 batteries. if parking for a long term either remove the battery or put it on a battery tender. if you parked it in the cold, and it ran down, the battery will freeze and destroy it. sounds like what happened here.