Power Problems. Please help.

**RPM_VR4** · 11-14-2004, 12:16 PM

My system works good most of the time if the car is running (although sometime if I am idling I have to rev the engine to keep it alive). I do not survive cranking and it will only work for about 5 min if the car is off before it locks up.

Here's what I got:

Bat-Cap 800 under the hood connected to the chassis, car power, and the alternator. Three 2-AWG wires (two for power, 1 for gnd) running to the trunk where I have an SLA (yellow top) [yes, I have 120A breakers near both batteries in case of short]. Then, the SLA goes to a ground distro and a fused power. I have a 1.3F cap going to both distros (unfused, but with 50A auto-reset braker). The GND distro is connected to chassis. On the fuse block I have 2 Amps, the Radio, and the PC. PC is ran off a RadioShack 60Watt DC/DC (16-9V to 12V regulated) and a PW-70A. The PC is a FlexATX /w a Celeron 1.1, one SIMM, a laptop HDD, one case fan + CPU, and 12V going to a Lilliput. On the USB bus I have a DeLorme GPS, the liliput touchscreen, and an IR-Man.

Here's what I intend to change:

I need a better 12V regulator. I'm going to use a SiPex evaluation board of a tiny DC/DC switcher that can go up to 6A.

Due to not surviving cranking, I'm thinking of using an isolator. Another option is to use a power relay, but that would not solve the problem of having to rev sometimes when idle (like in a fast food line).

Will an isolater fix my problems? If yes, why does it currently work for only 5 min when the car is off?

Any other suggestions are welcome.

Thanks,
-Ryan

**RPM_VR4** · 11-15-2004, 04:24 PM

^ Bump ^

Come on you tank battery experts, give me some advice. (Please).

**RPM_VR4** · 12-01-2004, 03:50 AM

^^^ BUMP ^^^

New info:

Got an isolator but haven't installed it yet. I'm still waiting for the SiPex sample.

Have only ever seen the needing to rev issue once.

Does survive cranking sometimes.

Question: Please explain the theory behind a "tank-battery" and tell me if I am doing it right by using a BatCap 800, a normal SLA (Yellow-Top equiv.), and an isolator.

**dbxxx** · 12-01-2004, 11:51 AM

no dont use an isolator.

i have a similar setup up in my jeep but i have everything in reverse. i have my main battery powering my batcap 800 then going to the 1F cap the to the distros. i have a the stock 130 amp alt. and i have no problem powering 5000 max watts to my stereo. Also you dont have to run that ground wire from battery to battery you can ground each one individually. make sure that the line that is chargin your second battery inst fused. until it is distributed to the products.

I would also recommend upgrading your big three using that 2 gauge ground you no longer need.

alt- ground wire
alt- batt wire
batt- ground

you can just add those wires on to the existing terminals no need to cut anything. Shouldnt take more than 2 hrs to do. i wish i could fidn the link for ya.

hope that helps
if i said anythign wrong please correct me

**dbxxx** · 12-01-2004, 12:00 PM

dont use an isolator keep the batteries in parallel
by the way how big is your alt?

**RPM_VR4** · 12-01-2004, 03:07 PM

Thanks for the comments. I want to hear from people about pros/cons of my setup. I think your suggestions may not really work for my config though. Please read below and then give me your opinion. Anybody else willing to chime in too?

I think my Alt is 130 (is a 3000GT).

My config is a lot different since the main battery is in the trunk. The alternator needs to charge the main batt at upto 130A. Using the car chassis to do this is not wise. Also, without the isolator, the BatCap is capible of sending 800A to the rear. As for improving grounding under the hood... I have tons of 2AWG ground-wires connecting everything under the hood (ground-wire-kit style which does add HP).

I know the BatCap is not intended to be used with an isolator, but I have run my car off of just the BatCap before, and since the BatCap is under the hood (I couldn't fit a normal SLA battery under there due to space taking engine mods), I am trying to go for more of a 2nd battery approch instead of a bass-cap approch. Besides, without an isolator, the PC does not always survive cranking and sometimes the LCD (powered via ATX +12) will flash a bit due to the engine bringing down the voltage. I need a "tank-battery" and I believe an isolator is the best way to do that (yes/no)?

BTW: Does your setup survive cranking just by having the BatCap in the rear with the PC? I would think cranking would still bring down the voltage (unless you have an isolator).

**dbxxx** · 12-01-2004, 03:21 PM

yeah it cranks fine, i dont have to rev anything. (if by cranking you mean starting).
i found the link it may be worth a look at least.
http://forum.sounddomain.com/ubb/ult...c;f=5;t=007801

you seem to have a pretty serious electrical problem. it seems as if you arent charging your battery correctly if youre having to rev you engine to get power to it.

maybe a diagram will help me understand your problem. by the way all batteries are grounded to the chassis one way or another.