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Swapped alternator, some possible issues with large caps


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I had a custom alternator rigged up for my chevy spark 2014. 5 companies turned me down saying they couldn't offer me a higher amp alternator vs stock ( 120A ). Singer made a custom one by using the stock front-end of the bell, machined it out, and managed to get me 200A.  This alternator bypasses the field control and is made to run high. This was done, because the stock system would go into a gas-saving 12.8V alternator output eco mode. With the bypass ( not connected ) the car puts the alternator in an assumed 13.8V constant mode. In our case, the alternator runs 14.5V 24/7 in all conditions because its self regulating and singer set the regulator to the higher voltage. Im able to run full-tilt on my dual sundown-audio x8 v.3's and never see my voltage drop below 14V, so the alternator handles it well. Super happy.

 

So one day, i thought it would be cool/fun to put a 500F maxwell ultracap bank with the system. Had the bank charged up to the battery in the rear ( i have 2 batteries, front and rear ). The 500F bank was at 13.8 like all else, as i had the car on an external power supply for charging/testing. When i started the car however, the car wouldnt start. It would get a few turns before the rpms just dumped to zero and stalled. Almost like the alternator current draw is way too much for the engine to handle.  Is that even possible? Once i took the bank off, it starts fine with the two batteries. Tho i noticed at idle rpms, something like windshield motors, can make the rpms bog for a few seconds while the rpms dip and overshoot back up.

 

This is a 80HP 1.2L or so vehicle. Not much. Running an alternator of higher current & clocked up voltage. Is it possible for it to really bog my engine that much? These cars idle at like 800rpm if not less. Tiny eco friendly engines.

 

The car does have a battery current sensor...could that be why?

 

I have positive from the alternator going to the front battery. And front battery + and - parallels to the rear battery. All 1/0. Front battery ground cable is 1/0 with the current sensor. Thankfully, it fits 1/0 stock.  However, im also heavily grounded in the rear. Rear battery grounds to the seatbelt anchor bolt, as well as the 1/0 ground that returns back to the front battery. 1/0 all around.

 

Electrically great, but it occured to me, any draw on the system ( or that 500F going from 13.8 to 14.5v ) is 100% non existing to that current censor. As, id expect it travels to the frame, and frame to engine/alternator. Fully bypassing that censor. Would this possibly cause an issue, where the engine may idle too-low due to not knowing theres a demanded load happening? Im at a lost if this is my problem, or if my engine is literally just too pissy to handle this alternator when at idles & demanding load.

 

Note - normal operation with 2 batteries, ive been hammering this system for a year now with zero issues. Very solid voltage. This ONLY came up when i put that 500F bank on and relised the car doesnt start. Then it made me notice the other minor things I never noticed, like idle + make the window go up even tho its already max up, bogs the engine for a second and makes it overshoot rpms before returning back to the 800'ish idle. Im mostly posting this to know if that current sensor being bypassed with rear grounding, is screwing my stuff up..if alternator can be too heavy for an engine.. or if i have another, worst underlying issue.

 

Thanks for your time & look forward to ideas

 

 

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Edited by Vexser
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