Electrical Advice

[01BlackZ71]

A friend of mine has a 1999 Silverado with the 5.3 liter in it. He has an airbag suspension on it and recently installed two new air compressors. They are two very large compressors, which I'm sure require a lot of power to run.

 

Anyway, when they were both turned on they sounded like they weren't really running as strong as they could/should, and if he let the truck idle with them on his voltmeter in the dash would drop almost to the red. If the truck was revved a little the compressors would run faster and sound better. He recently had one of the compressors burn out, and now I have a question.

 

He thinks the best way to solve the problem would be to add a second battery. He currently runs just a standard size battery, and was wanting to switch to dual Red Top Optima batteries. However, I was under the impression that the battery more or less started the truck, and the alternator kept it and all the other electrical stuff running. I'm trying to convince him to just buy a high output alternator for the truck because that would solve the problem. Am I right? Should he just buy a bigger alternator to power the compressors, or would a second battery with the stock alternator actually work?

 

Thank you.

[bfrd22]

Both:

 

If I am right each compressor will draw approx 30 amps at 12 volts. Thats a 60 amp per minute draw.

 

If he as air Cond, he would have I believe about a 100 amp alt.

 

Delco has a 30 percent variance in acceptable out put. So your probably getting maybe 80 amps out of it.

 

Now the 80 amp output would only occur around 2000 engine RPM.

 

At Idle your only putting out 1/3rd or about 27 amps. Just enought to run your lights and AC on low.

 

So A bigger Alt would be in line.

 

Further an additional Deep cycle battery. Personally I would suggest an RV type. 600 amp with around a 150 reserve. Also install an Isolator to further protect the trucks systems.

 

The problem is that a battery at 11.8 volts is about 80% depleted. Pretty much dead. and very hard on the trucks electronic because it no longer is providing the Voltage and Current smoothing function is performs.

 

Once you get into this lower voltage you are now running a Pulsing DC. very hard on the systems.

 

He burned up the motors due to heat. as the voltage avalible droped the amperage draws of the motors climbed.

 

30 amp x 12 volts. 60 amps @ 6 volts.

 

160 amp high output alt. 600 to 725 deep cycle RV with 100 min plus reserve with an isolator.

 

 

Now I've never ran bags and compressors. But I work with these issue of High amperage draws at idle on emergency vehicles everyday. Similar problem.

 

 

There a company in Texas Vital Alternator. Specialize in High Out Put Alts.

 

1-800-886-8224

 

tell em Andy from Canada Sent ya

[01BlackZ71]

I appreciate the reply. Surely out of the hundreds of people who view this board daily someone else could add some more. Anyone?

[Stealthy]

Since the response is light I'll drop out of lurker mode with an observation.

 

I don't know anything about air suspensions and their layout, but from an electrical standpoint my decision would be impacted by compressor run-time. If they run a small percentage of the time I would dedicate an isolated battery to them (suited to that kind of load) and locate everything close together using heavy guage cabling. If they are designed to run continuously (the compressors) I would do the same thing, but also add the appropriate HD alternator.

 

Besides the continuous draw, compressors also have a large inrush current on startup. The problem with an alternator only solution is that the alternator can't dump that large amount of current instantly; batteries can. As long as the compressors only run occasionally the stock alternator (or a common HD one) can replenish the batteries during the compressor off-time. If the compressors run for extended periods, the battery can handle the inrush while the (specialty, super-heavy-duty, expensive) alternator ramps up it's output to maintain system voltage.

 

One other thing, and again I know nothing about air suspensions: If you increase the size of the air storage tanks (I assume they are used, being a pneumatic system) the compressors won't start/stop as much. increasing longevity and easing the electrical demands.

 

-Stealthy-

[01BlackZ71]

"lurker mode" That's funny

 

Ok, a crash course in air suspension. You have bags at the four corners, tanks mounted either in the bed or under the truck, with at least 4 valves in between. A compressor(s) is connected to the tank to supply the air pressure. If the tanks are completely full (this all depends on the capacity of the tank(s)) then you can lift the truck off the ground a couple of times before there just isn't enough pressure to do it again. Then you hit the switch for your compressor to kick on and replenish the tanks. The compressors do not run all the time, unless you have an extremely small compressor and air tank and are constantly raising and lowering the truck. My friend had a small compressor and it took forever to pressurize the tanks, meaning that he had to listen to it hum and couldn't play with his bags as much (if he was in a parking lot or something). So when he rebagged his truck this summer he put two of the largest compressors out there in it so he could get air fast. We quickly determined that the compressors take A LOT of electricity!

 

For run time, I'd say they only run for 3-7 minutes at a time on average. In my opinion though, I think if he could supply them with more power they would run a lot faster and efficiently so the times would be even less.

 

I forgot to mention in the first post that he has consequently burned up one of the compressors. We figured it burned up from lack of adequate power. I will add, that since the one compressor has "died" the other has come to life and runs a lot stronger, verifying that they need more juice to run better.

 

Does that help any more? The two responses I've recieved have been great, but more never hurt.

 

Also, for those of you looking to bag a truck, my friend wishes he had just bought a compressor that mounts to the motor and works a lot like an air conditioning compressor does. Still though, he is looking to quickly resolve his electric compressor problem.

 

Thank you.

[Ben]

You have a CS-130D alternator (CS=charing system and 130=dia in MM of the alternator). Consider going to higher output CS-130D or switching to bigger CS-144.

 

Hot links to vendor selling both and in kit forms.

 

shows cs130d vs cs144 and all of the kits

 

pic 130d/144 side

 

 

pic 130d/144 front

[Ben]

PS...his battery is going and most likely has in-famous positive post issue, which will kill alternators, pos cables and even starter.

 

PPS...if he's jump started another vehicle while his engine was running, that will kill alternators, which will kill batteries.

 

Here's my standard reply

=====================================================

 

 

 

....note that the brass nut is drilled out and just acts like washer. There are TWO OEM lugs on the battery terminal, then brass nut, then accessory lug (3 wires, two 50 amp fuse holder, one 30 amp fuse holder) and alarm power wire. Have since gone to store bought that looks very much like this one (it's shown on #1 Son's battery page).

 

 

http://forums.vmag.com/suvsuburban0402/mes...sages/5109.html[/url

 

TEXT from that article:

 

That bad battery post design can/does kill alternators, batteries, starters, battery cables, and wreck havoc with other electrical circuits.

 

Think many don't know what Traveler and I are talking about. Here's an example of what is happening and the cause'n affect:

 

Take the battery positive cable lug and unscrew it from the battery (disconnect it). Manually hold the cable lug to the battery post. Start the vehicle. Now touch, remove, touch, remove the cable lug to and from the battery pos terminal. THAT is EXACTLY what happens when that stupid lead spacer crushes and allows the bolt to bottom into the battery pos post.

 

The alternator sees the battery, charges (provides oltage/current), then the connection goes away. Voltage at the alternator goes up (maybe several hundred volts, instantly...or almost that fast). Then when the contact is made again, the alternator will see huge load (maybe hundreds of amps, instantly...or almost that fast). This is called load dumping and will kill a good alternator in short order.

 

Above load dumping will also kill the battery in short order too. Over voltage and over current. Also will have high resistance terminal, meaning voltage drop, meaning current used at that spot. That current usage turns out to be heat...high enough to melt the battery case, which will allow battery acid to leak into the joint *AND* down the cable (cable acting like a wick and cable insulation acting like a hose...carrying battery acid down to the starter...starter don't like battery acid).

 

Another cause is that there is a lead spacer between the two cable lugs on the battery post. One time use, as 2nd time tightening the bolt will have the lead washer too short to provide resistance and allows the bolt to bottom out inside the batt pos terminal. That then cracks the batt case, allowing acid to leak...ditto above, ruining cable, starter, alternator, battery, etc. Throwing away the lead washer, cutting off the plastic from the lug blades (flat part only) and replacing the washer with stack of brass washers that won't allow the bolt to bottom is a fix.

 

All of the above then has this affect on the vehicle computer: turns it on and off. Or various components of the vehicle. Which one??? Who knows and not always the same one. Engine dies for no apparent reason. Doors lock and unlock for no reason. Window motors burn up for no reason. Lights turn on, off for no reason. After market alarms turn on/off and lose their programing. ETC, ETC, ETC.

 

Another way to avoid/manage the lead crush washer is to use a hardened brass bolt that is threaded whole length, that is longer than needed and a hardened brass nut. Put nut on and screw it to the bolt head. Stack up all of the lugs on the bolt, then screw the bolt into the battery pos terminal till it hits bottom, back off 1/2 turn. Now turn the nut down onto the stack of lugs while holding the bolt hex from turning (do not allow bolt to bottom into the batt terminal and only HAND tight). Tighten the nut till it's tight and makes good connection. This way you'll be able to keep that lead spacer and not have to cut off the plastic covers on the lug blades...

 

This avoids bottoming the bolt, which is one cause of acid leaks (cracks battery case), other is high resistance and the heat generated melting the batt case...causing acid leak.

 

Another potential is jumping another car while your engine is running. Here is hot link to that thread at hot link below.

 

http://forums.vmag.com/suvsuburban0201/mes...sages/1157.html

 

 

How2 to jump start another vehicle without damaging your alternator

 

 

Posted by Ben on February 18, 01 at 20:24:45:

 

Have received several email requests on how2 jump start, so here are my thoughts on the subject.

 

First, why it can/may damage your alternator. When an engine's starter is first energized, there are huge inrush currents needed to build the magnetic fields necessary. Rule of thumb is 10 times locked rotor current, an approximate number. So a start motor can pull several hundred amps of current (500-1,000 amps). The current will come from the vehicle that has the juice (your's that's jumping the dead one).

 

To avoid damaging your alternator, here's the sequence and what/why's. Good vehicle with the good battery is vehicle A, dead battery is vehicle B.

 

A's engine off, connect pos battery to B's pos battery (make sure vehicles are not touching, else there's a neg connection). Start A's engine. Connect B's neg battery term to A's alternator bracket (to avoid sparks at the battery, there's hydrogen & oxygen gases around batteries). Careful, there's rotating stuff.

 

Let A charge B for a while. Depending on how dead B is, up to 15 minutes with A's engine RPM held above 2Krpm. This will charge B's battery enough to allow it to help A's battery in a second.

 

TURN "OFF" A's engine and allow it to stop rotating for a few seconds.

 

Now start B's engine with A's battery connected, but A's engine OFF.

 

This will have A's alternator not supplying any current and the current draw from B's starter motor will only get current from A's & B's battery. Once started, leave it running for a bit and then carefully remove the connections. Safest is to stop both engines, but sometimes B will stall. A's alternator diodes will not be exposed to hundreds of amps and will save an alternator replacement down the road.

 

Alternator diodes are only rated for a fraction of the rated current of the alternator and will fry if exposed to high current draw. That is why your own vehicles starting circuit disconnects the alternator while starting and reconnects after the engine starts. The battery is to supply this spike current, that is why batteries are rated in "cold cranking current". The better ones are rated 800-900-1000-plus amps.

 

Also, why the connections and wiring between the battery & starter must be in tight and low resistance

[Stealthy]

For run time, I'd say they only run for 3-7 minutes at a time on average...

 

I forgot to mention in the first post that he has consequently burned up one of the compressors.  We figured it burned up from lack of adequate power.  I will add, that since the one compressor has "died" the other has come to life and runs a lot stronger, verifying that they need more juice to run better.

 

So do you run the compressors only 2-3 times a day? If that's the case you may be able squeek by without a bigger alternator (though it's probably a good idea if funds allow).

 

I'd try just adding the dedicated battery and isolator to start with. The compressors will definately run better and the truck electrical system would be much happier. The concern then is just maintaining a charge. If the stock alternator is overtaxed then you can either upgrade it or (since it seems your buddy has no fear of modifications) add a second alternator.

 

As for burning up the compressor, a lot of the damage was probably sustained during startup when they were struggling to get up to speed. With adequate power they should "snap" on almost instantly. One way to minimize the startup strain is to start the second compressor 1-2 seconds behind the first one. Then they won't fight one another for inrush current.

 

-Stealthy-

[Ben]

Add that typical rule of thumb for high inrush (motors) is to use 10X the max current or locked rotor current.

 

So if the 30 amps is correct, in rush will be in the neighborhood of 300 amps. Not very long, but long enough. Times 2 pumps if they are turned on at the same time. That would make it around 600 amps of inrush current. Of course dependent on the type of motor on those compressors.

 

Very few alternators can handle this and why jump starting another vehicle with our engine running will kill the alternator...the other cars starter will pull that kind of current, even more if V8 from the highest voltage source...the alternator if it's running.

 

The battery is supposed to supply this type of current. Why some have said to use an isolator. But if your buddies alternator is going bad, the battery is also most likely going bad too (read my post above in previous).

 

The wiring and protection must be sized accordingly. Larger wire size and slow blow fuse made for motor protection or circuit breaker.

[Ben]

Maybe folks don't know what inrush is.

 

It's the power (amps, voltage) needed to magnatize the metal of the whole motor, the windings in both the armature and field, and the magnetic fields of both the stationary field and the moving armature.

 

This is before the armature will even move, as to move it has to have opposing magnetic fields. Push/pull of the armature working against/with the housing field windings. A bit less current if the permenate magnet.

 

The bigger the electric motor power rating, the more iron/windings/etc that has to be magnatized, which means more power.

[JayMan]

Both:

 

If I am right each compressor will draw approx 30 amps at 12 volts. Thats a 60 amp per minute draw.

 

If he as air Cond, he would have I believe about a 100 amp alt.

 

Delco has a 30 percent variance in acceptable out put. So your probably getting maybe 80 amps out of it.

 

Now the 80 amp output would only occur around 2000 engine RPM.

 

At Idle your only putting out 1/3rd or about 27 amps. Just enought to run your lights and AC on low.

 

So A bigger Alt would be in line.

 

Further an additional Deep cycle battery. Personally I would suggest an RV type. 600 amp with around a 150 reserve. Also install an Isolator to further protect the trucks systems.

 

The problem is that a battery at 11.8 volts is about 80% depleted. Pretty much dead. and very hard on the trucks electronic because it no longer is providing the Voltage and Current smoothing function is performs.

 

Once you get into this lower voltage you are now running a Pulsing DC. very hard on the systems.

 

He burned up the motors due to heat. as the voltage avalible droped the amperage draws of the motors climbed.

 

30 amp x 12 volts. 60 amps @ 6 volts.

 

160 amp high output alt. 600 to 725 deep cycle RV with 100 min plus reserve with an isolator.

 

 

Now I've never ran bags and compressors. But I work with these issue of High amperage draws at idle on emergency vehicles everyday. Similar problem.

 

 

There a company in Texas Vital Alternator. Specialize in High Out Put Alts.

 

1-800-886-8224

 

tell em Andy from Canada Sent ya

I would say an isolator and separate system for this airbag system. Must be one of those "slammer" trucks, right??

 

You can rig up a second alternator, which would be completely separate from the vehicle electrical system. That would avoid a lot of problems and potential PCM failure.

 

I know what you mean about emergency equipment and high idle current draws. Kussmaul makes a very nice line of load management systems, fast idle kits (Automatic or manual), and boosters. A nice thing about the automatic fast idle is once the voltage drops to a preset point, the idle is increased to 1500-2000 RPM.

[99-2door]

PS...his battery is going and most likely has in-famous positive post issue, which will kill alternators, pos cables and even starter.

I knew somebody would blame this on the side-post battery.

[AZ-Z71]

Just courious, Is this how they are rigging up the electrical for running extra lights like sereval high watt KC lights?

 

Was thinkiing about adding a grill mount/bumper mount lighting system with maybe three or four high watt off road lights. (Not sure of wattage yet) Just toying with the idea but want to know what I would have to do to support them.

[bfrd22]

Generally you wouldn't have a problem.

 

A 100 watt light draws about 12 amps, 55 watt about 6 amps

 

Size your wires 14 guage and use relays.

 

Depending on usage you wont have a problem as there is no major inrush of current.

 

If you plan on using em more often go to a deep cycle reserve.

 

I run 2 55 watt ditch lights in the Grill Guard, 2 100 watt 5" projectors, and 100 watt Procomp 5x8. On the show bar.

 

3 curcuits, Front; Projectors and ProComp.

 

Projectors and 5x8 on the show bar and are remote controled.

 

I run a deep cycle 725 CCA with a 125min reserve.

 

not a problem yet.

[BlackSilver]

Since the compressors are only an occasional surge load, a larger alternator is an inappropriate solution. If additional capacity is needed (which I really don't believe) a second battery in parallel will cover the short duration intermittent load.

 

However, before I added anything, I'd clean up the wiring and connectors, ensuring I used the shortest routes and good heavy conductors.