Causes of low voltage?

[float_6969]

OK, so here's the info;-Under no load, I've got about 13V at the SDS. It actually fluctuates from as low as 12.8V-13.5V.-If I turn on ALL off my electrical accessories the voltage at the SDS drops to a whopping 10.8V. -That same condition at the battery renders me almost exactly one volt more than that (11.8V)-I didn't check the voltage at the battery w/no load-The alternator checked out OK two weeks ago when I had it tested-I am using a riding lawn mower battery-It has been, unfortunatly, deep cycled about 5/6 times (completly, or nearly completely discharged and recharged)-I have the stock KA-E negative battery cable that grounds at the battery tray (chassis) and at the engine block-The positive battery cable is twice as long as stock because my stock cable barely reached with this battery so I stuck my KA-E cable on there too (full length) so that it would reach.

I plan on trying to shorten up the positive battery cable and adding some grounds and see what that does. I'm also going to check the voltage at the back of the alternator and see what that comes out at. Any opinions/tips would be greatly appreciated!

[CA19DET]

Quote »-I am using a riding lawn mower battery-It has been, unfortunatly, deep cycled about 5/6 times (completly, or nearly completely discharged and recharged)-I have the stock KA-E negative battery cable that grounds at the battery tray (chassis) and at the engine block-The positive battery cable is twice as long as stock because my stock cable barely reached with this battery so I stuck my KA-E cable on there too (full length) so that it would reach. [/quote]those all sound suspect to me, i would get bigger gauge wires for the gounds and power, test out your current set up with just abigger (preferable new) battery, and try cleaning all your grounds..

[biosehnsucht]

ditto. somehow I think the current capacity of any lawnmower battery, "large" (riding) or not, is a bit suspect.

[maik21]

i have the same problem...and the repair man change the voltaje regulator of the alternator and now, all be fine!!!

[maik21]

and one more... when the diode into the alternador fail... you can drive fine.. but when the night comes, you need to on lights.... the batery voltaje comes down and the vehicle stop <--- thats was my problem... !!

[slownslurious]

take it to autozone for a free battery/alternator test... also agree with checking the voltage drop on your wires. If its like 11 volts at the ecu end what is it at the battery? if its low at the battery its probably your alt.

[boost_boy]

OK, so here's the info;-Under no load, I've got about 13V at the SDS. It actually fluctuates from as low as 12.8V-13.5V.-If I turn on ALL off my electrical accessories the voltage at the SDS drops to a whopping 10.8V. -That same condition at the battery renders me almost exactly one volt more than that (11.8V)-I didn't check the voltage at the battery w/no load-The alternator checked out OK two weeks ago when I had it tested-I am using a riding lawn mower battery-It has been, unfortunatly, deep cycled about 5/6 times (completly, or nearly completely discharged and recharged)-I have the stock KA-E negative battery cable that grounds at the battery tray (chassis) and at the engine block-The positive battery cable is twice as long as stock because my stock cable barely reached with this battery so I stuck my KA-E cable on there too (full length) so that it would reach.

I plan on trying to shorten up the positive battery cable and adding some grounds and see what that does. I'm also going to check the voltage at the back of the alternator and see what that comes out at. Any opinions/tips would be greatly appreciated!

Ryan, from experience with installing SDS systems for myself and customers, the circuit you're using is not strong enough to completely power the SDS system. You can either:

A. Probe around your in-car fuse panel to find a stronger switched 12volt ignition source (This is usually the fix).

B. While the car is running, check the alternator's output to see where you're at voltage wise.

C. Definitely make sure the SDS is grounded properly

D. Your Lawnmower battery is worthless in this application.

E. Call me if you still can't get it right..............

Dee

[float_6969]

I replaced the battery and I'm fine now. I havne't seen below 13V on the SDS since I put it in this morning.

I replaced it with another lawnmower battery. It was $25. Due to space limitations (intercooler piping), I've either got to use this battery, buy that stupid expensive one that Heavythrottle has, or relocate it.

I will probabally opt to re-locate it later, but for $25, and practically no work, that was the best option for now.

[biosehnsucht]

I'd buy the expensive one - relocation is a *****, and you'll need a batter box and/or external kill thingy in alot of racing organizations' events

[slownslurious]

my friggin MOPED uses a lawn mower battery and it can run it dead pretty quickly...

[float_6969]

I ran this exact same battery for at least a year before this. And like I said, it was deep cycled WAAAYYY more times than it should have been. I'll prob get another, "better" battery later. But it's low on my priority list right now.

[nnkfws333]

Ever try those Miata batteries? I used them on my last car (SR) and I never had a problem like that.

[float_6969]

The problem is that even this lawnmower battery barely fits. I don't even have a tie down on it because it won't clear. Damn intercooler piping...

[nnkfws333]

Well looks like you might be relocating it to the trunk then right? Must be a pain in my opinion if someone ever needs a jump. Glad your problem is solved though.

[float_6969]

PDM Racing has a battery that is really small and will fit underneath the passenger seat if I want. I could also leave it in the stock location, but I don't know how it'd fit.

[slownslurious]

Well looks like you might be relocating it to the trunk then right? Must be a pain in my opinion if someone ever needs a jump. Glad your problem is solved though.

you do realize you can just jump it either from the wires under the hood or on the battery in the trunk, right? so jumping a car with a rear mount battery is actually easier because you can jump from either end..

[Dattebayo]

After a battery re-location, why/how would you keep wires under the hood that are exposed for jumping? Are you daft?

[slownslurious]

someone please tell me he is joking...

[Dattebayo]

Since you are apparently way smarter than me Ill just say that it seems like a incredible redundancy with potential for losing voltage along the trip. A smoother, less junctioned wire/circuit will carry electricity more efficiently than a spliced one, especially with higher current. Its just something that was beaten into me while apprenticing for the local 26th IBEW.

[slownslurious]

unlike you, apparently I did not rewire the entire car when I ran my trunk mounted battery, so the stock battery cable is still present, as are 2 or 3 other perfectly acceptable places to jump start.... I'm not sure what ibew is but apparently it doesn't transfer into the CA forums very well.

[float_6969]

Alright kids, chill out. We don't need a pissing contest. The purpose of the post was to ask a question and that question was answered.

Any more snyde posts and I'll delete all non-relavent posts and lock the thread.

[boost_boy]

Alright kids, chill out. We don't need a pissing contest. The purpose of the post was to ask a question and that question was answered.

Any more snyde posts and I'll delete all non-relavent posts and lock the thread.

Big man today aren't we ?

Alright kids, chill out. Any more snyde posts and I'll delete all non-relavent posts and lock the thread.

Alright kids, uncle stop being rowdy before uncle Ryyan snuffs your post . J/K

Dee

[float_6969]

Well I got a little better numbers today regarding the voltage. Apparently the problem isn't fixed as the wideband still keeps resetting. Here's some measurements I took tonight;

No major loads14.5V @ Alternator14.4V @ Battery13.3V @ SDS (and wideband)Full electrical load12.0V @ Alternator11.9V @ Battery11.1V @ SDS (and wideband)

I've shortened the positive battery cable back up. I've got basically no resistance on the battery ground. I ran a ground wire from the battery to the general location of my SDS and Wideband grounds (they're not all on the same spot, but they're close to each other)

I'm suspecting the voltage regulator as I shouldn't be getting down below 12V at full electrical load at idle, should I? The only things I haven't done yet are anothe new battery and a different switched source.

I'm so sick of wiring....

[biosehnsucht]

try a full size batteryI know it won't fit, but hook it up somehow and see if it fixes it when testing sitting still

I'm not sure if regulators are going to help raise voltage. might be a dying alt regardless, but AFAIK the regulator is a limiter more than an increaser..

[Dattebayo]

How soon after startup did you get the full-load readings? This may be important if the levels drop off before 2 minutes pass by, pointing to your battery as the culprit. If the levels are constant from after startup, I would suspect teh voltage regulator.

[float_6969]

How soon after startup did you get the full-load readings? This may be important if the levels drop off before 2 minutes pass by, pointing to your battery as the culprit. If the levels are constant from after startup, I would suspect teh voltage regulator.

Actually, now that you mention it, I think it does get worse the longer the car runs.

try a full size batteryI know it won't fit, but hook it up somehow and see if it fixes it when testing sitting still

I was thinking about trying that this weekend. I don't know how I'm going to drive the car though. I may have to take the hood off...

I'm not sure if regulators are going to help raise voltage. might be a dying alt regardless, but AFAIK the regulator is a limiter more than an increaser..

It does both. It increases or decreases the current flow bases on how much voltag the alternator is creating. If the current drops below 12.5V it will increase voltage, if it goes above 14.5V, it will decrease voltage.

[float_6969]

BioShenSucht: In the other post you asked what the voltage was when running with minimal load, and when off.

MInimal load is 14-14.5VOff is 12.5V

[float_6969]

OK, it's all fixed now. I ran a relay and more direct wiring to the SDS/wideband fuse system and cleaned all of my grounds and I'm getting no voltage drop at all. I guess the stock wiring was just too long. Thanks for all the help though guys!

[biosehnsucht]

after having to rebuild my alternator two (or was it three??) times, I replaced my alt positive wiring, replaced the positive battery terminal with a toyota one (really nifty attatchment, and has built in fuse stuff on it and multiple bolt on connectino points), .. the negative terminal is still hooked up as it was tho, so if anything my grounding is still crap, but I haven't had to rebuild again yet.. I had to rebuild like after a month and ahalf or so maybe two each time..

[Dattebayo]

Was it just all the junctions that made the drop you think or was it just the length of wiring that made it drop? I'm just curious for the moment.

Also, your battery may be fine for now, but perhaps in the future after many start ups you may see the same issues again but with a twist. Look at the cold start-up amps available from the battery (available from the manufacturer sticker) and compare them to what your car pulls when cranking cold using an ammeter.

This will decide the life of your battery. If you wish to keep the current battery I would suggest you pull the battery every few nights and charge it with a house charger or charge it in the car.