Installed a 29ah SCiB, now my car only charges sometimes

[ka0s1]

So I have a 2009 Cadillac CTS that I’ve ran 96ah of headway in for about a year, also has a JS 250a alt with a 14.8v regulator on it, I’ve been running it at 14.8v for about a year with a brandxelectrical voltage controller. It plugs into the alt like the factory plug and then the factory plug plugs into the controller to keep batter light off

Okay now to the issue. I installed a 29ah SCiB (controller is supposed to allow charging up to 15.5 v,) after installing the alternator wouldn’t charge, so I let it sit for a day ir two till I had the time and then I started the car and it started charging, next day the car doesn’t charge

So the issue I’ve ran into is sometimes when I start my car it starts charging and sometimes when I start it it doesn’t charge at all. I have absolutely no idea where to even begin. I’ve already changed the control box for the controller and still nothing. When the car charges it charges to 15.3 max so I know it’s not the computer somehow blocking the controller and telling the alt not to charge because of high voltage (not my current problem tho a diode will fix that)

Im not saying that it can’t be the alternator I just want second opinions before I move on. If I do order an alt I would get a 360a with a 15.5v self excite regulator to bypass the factory plug and all the confusing wiring and just put it on a voltage controller

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[Popwarhomie 5,000+ posts]

When it does work is it at 14.8 volts or higher?

On mine I bypassed the factory alternator wiring completely and ran a diode on the sense wire to get 15.5+ volts. This was not a GM vehicle though.

 

[ka0s1]

When it does work is it at 14.8 volts or higher?

On mine I bypassed the factory alternator wiring completely and ran a diode on the sense wire to get 15.5+ volts. This was not a GM vehicle though.

It will work above 14.8 when it works. It’s completely random I’ve tested the alt when it happens and when it’s charging it’s charging as it should but when battery voltage is dropping the alt isn’t putting out any voltage. I’m leaning towards maybe the 14.8 regulator on the alt but I’m still kinda new to all of this so I’m not sure

 

[Popwarhomie 5,000+ posts]

That's what I would guess. Contact JS and see what he has to say.

 

[Mitchell Fosgate III]

You can only charge it up to 14.4 volts for the battery. There's a fuse box, if charging goes over, it goes above the amp rating for the battery cable. Then it dies or the fuse is broken. Almost all car battery charge up to 14.4 to be accurate.​