BigDB

Ok Iv got a Optima red top mounted in the back, ever since I switched to the Optima in the back Iv had weird starting/charging issues. Iv included a diagram of how my system is wired. All wires are 1GA crimped and soldered brass eyes except the Alt wire which is 6GA. Cold the system charges but shortly after the system shows under 13v like the Alt doesn't sense an electrical load. (is this a cause of the AGM battery?) I have not done a voltage drop test yet as I have the trans out but will once my scatter shield shows up. On hot restarts it acts as the battery is almost dead as it turns over slow and I hear the relays clicking inside the vehicle, the trip also resets. Once started it searches for idle and wont idle down eventually throwing a IAC code. Battery probably needs replaced but I don't want to replace it with another AGM if its causing part of the issue. Thanks for the replies.

Doug G

I would not run less than an 0ga. for + and -.

But sounds like a grounding issue. How is battery and motor grounded ?

BigDB

Battery grounded to rear seat belt buckle and car has cage tieing front to rear. Block is grounded to multiple points on the unibody

soundengineer

iTrader: (16)

you need to run a ground directly to the Battery, not thru the chassis
Chassis Grounds suck...period..only good for small wires and low current.

BigDB

I'll give that a shot. Ill see what I can get local as I don't have any battery cable at the house.

soundengineer

iTrader: (16)

also, your alternator wire needs to be quite a bit bigger if it runs all the way to the back...
down to a 1awg or a 1/0 wire

BigDB

Once I get it all back together I'll do a voltage drop test and see what cable I can get local. Thanks for the suggestions.

soundengineer

iTrader: (16)

you can buy 1awg and 1/0 wire from any welding supply store...
they all carry it, and most carry precut prepackaged rolls of 25/50/100 ft

soundengineer

iTrader: (16)

NO!!!

that document has a drawing that recommends 10 gauge wire from the switch to the alternator.....

it does say maximum 20 amps on the alternator lug......which means that switch is not really rated for anything in the real world...

that switch is a waste of money unless you own a Honda Civic.

BigDB

Problem where im located is Lowes and Walmart are about all we have. Its a town built around the base, so its a small town life which I kinda like. Its a few hours to a "real" city but Ill probably make that trip this weekend.

Im actually using that same Moroso switch but not using the alternator 3/16 lugs. I ran my alt back to the 1/2 inch lug on the battery side because its rated at 300 amps continuous. Iv checked to make sure the switch doesn't get hot, but maybe its the cause?

soundengineer

iTrader: (16)

as long as you run to the big lug, you should be fine...

I guarantee its either your Ground, or not a big enough wire on the alternator..

I'd start with the ground. grounds cause a lot more problems than the alternator wire would

Slowhawk

iTrader: (12)

On all the cars we do I run a 1/0 ground from battery to the frame, cleaned real good,painted over it. Then 2 ground straps off the motor, 1 on each side of 1/0 braided.

Power wise, 1/0 from battery to starter, then from starter to fuse box with 4 gauge.

Altinator has a 4 gauge going back to the battery.

Never/ever a starting or charging issue. All ends are crimped correctly.

soundengineer

iTrader: (16)

oh yes...many many times....
If you only knew my racing history.....I dont tell a lot of people on the internet as it was a over decade ago... but I spent some time in the hospital because of a 180mph wreck.




ever had a race car that requires 140+ amps for the alternator draw......I have....
****... my fuel pump alone draws 30 amps....more than the 20 amps that that switches small terminal supports.

soundengineer

iTrader: (16)

I always laugh my *** off when people get butthurt on the internet....

you crack me up....


and 2000 amps intermittent on that switch...300 continuous..


what you failed to realize was the point of my post was to show that a small lug rated for 20 amps is not sufficient even for a non race car...


no matter where your battery connects....if you have to supply voltage, your alternator has to be able to keep up with the demand...
sure...you draw less at idle than you do at WOT..

that 20 amp lug can probably handle short amount of higher current draw...
but a road race guy is going to have a high current draw for a lot longer than a drag race guy...and realistically, a drag race guy will have issues over time as he will burn out the contacts over many races...

and 10 gauge wire going from the rear of a car to the alternator??
seriously?
even stock wiring is larger than 10 gauge wire and its less than a few feet from the battery typically.

its just not worth the risk on an EFI car...
a Carb vehicle with a mechanical fuel pump might be a different story...
I know some carb guys that bascially dont have anything to draw any real current and can get away with a very small alternator. (I've seen small ones that only do 30 amps)


and just because you dont think a "real racecar" should have an alternator...doesnt make it true..
dont know where you live or know anything about you...
but if you go to some of the Bigger x275 races...I know some of those guys dont have an alternator and prefer to charge between rounds...but there are still quite a few guys who do have an alternator.


and lets not even talk about circle track.... NASCAR guys use an alternator...I definitely consider them a "real racecar"

sweetbmxrider

iTrader: (13)

I can't tell if your diagram is like this but you want the battery and alternator on the same side of the switch. On the other side you can run the lead to the starter post. Then you can run a lead from the starter post to the fuse/junction box. You can run the fuse box to the rear as well but it isn't necessary. You want a shorter run to the starter though, its current configuration is too much lead. You also want a large ground from the motor to the chassis, if not all the way to the battery, and it should at least match the positive leads in gauge size and wire type. Wire type plays into factor here as well. Use quality wire like guys with large stereos run.

85Iroc

iTrader: (12)

I would run 0g ground from front to back, anchoring at a couple of points along the chassis.

I actually changed transmissions because my transbrake wasn't working and I thought it was a trans problem. When the new trans did the same thing we figured out it was a ground issue.

Ed Wright

iTrader: (1)

Scott, your beating your head against a wall here.

BigDB

Thanks for all the replies guys. I will go thru my system when I get the trans back in it. I will update this thread when all is said and done.

soundengineer

iTrader: (16)

I know Ed......
but my problem... is that I care too much....

mike13

iTrader: (27)

Is there more amperage draw on a fuel injected ls at wide open throttle than at idle?