Battery draining after battery relocation and etc.

[timmyr77]

Hello r3v, so I'm having the typical batter drain. Alternator is rebuilt and was charging fine prior to me relocating the battery to the trunk in my vert and changing the light control wiring that short circuited under my dash. I put everything (almost) together and drove my car a few days. Battery died about 3 days later. I charged it up, cleaned the terminals, and after about 5 days of sitting and 2 days of driving it died again. I charged it again, and checked to see what I'm getting back from the alternator and it shows 12.5v. I know it's supposed to be closer to 13.5 but 12.5 should still do right?

I'm wondering if I failed to do soemthing when relocating the battery to the trunk. The other issue could be I messed up something when soldering the new light wiring harness, in which case I will just buy a new one.

Any suggestions or thoughts are apreciated.
Thanks Tim


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[AndrewBird]

Alternator should be putting out 14V with the engine running. If you only have 12.5V at the battery with the engine running, your alternator isn't working or isn't connected to the battery somehow.

Does your battery light work? It should light up with the key turned to on but the engine not running.

[spdracrm3]

how did you relocate the battery to the trunk? did you use a harness out of a donor car that had trunk mount or make custom cables? there are fuses in the factory cables to prevent damage and fires due to shorting.

if you have a volt meter what is battery voltage at the battery with the engine reved above idle speed ? does your meter do Amp testing? if so what is current draw with everything off? (put meter between disconnected neg cable and neg battery post with meter in Amps/MilliAmp position) be sure everything is off and key is out of ignition ,door all closed and trunk light off/bulb removed

[timmyr77]

Battery light works. It's not on when the engine is running.

I relocated using the harness out of a 325i sedan. I'll the check everything you said when I have some help for someone to rev the engine but when I check power coming to the battery yesterday it was 12.5 v too. So it's not loosing it along the way I guess. I'll get back with results. Thank you


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[timmyr77]

Alright i just went out and checked it at idle again for curiosity because when I did a battery test this morning it showed 100% after driving it for 2 days. And I'm getting 13.75 from the alternator and 13.75 to the battery. Not sure what it was but I guess it works. Thank you guys


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