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Old 10-23-2017, 03:34 PM   #1
weq92f
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too many amps, need better alt?

Going to add electric fans which when running will draw 24 amps ( 2x12 ). Calculating my total amp draw across the entire system I find that if everything is actuating all at once my total draw would be 121 amps.

My alt is currently a CS-130 at 105AMP. So, it's pretty close at the moment to being about the right size for my system without the fans ( amp draw without fans is currently 97 if all electrics came on at once! ).

What'dya think, should I upgrade the alternator as well when I add the fans?

Here's the amp calculations just for grins:


dizzy 8
Electric cooling Fans 24 total ( 12x2 )
Headlights 15
tail led lights 2
gauges 5
Radio/Stereo 8
Atomic EFI unit w/pump 30 max: normal: 14-18 -- I calc'ed 18
MSD 6a box 6 max
electric windows 10?
electric door locks 4
electirc seats 10?
A/C blower fan 7 on high
A/C clutch 4

121 total if all is running at same time
97 without the fans added

Thanks,

-klb
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Old 10-23-2017, 09:04 PM   #2
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Re: too many amps, need better alt?

I think your numbers are high in lots of places. If you are running a msd box the distributor is pretty much not going to draw much, dont think you need to have the door locks on the list. They only pull for a split second. What are the chances of all this on and at full load all at once? I think you will be fine with what you have.
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Old 10-24-2017, 12:29 AM   #3
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Re: too many amps, need better alt?

I agree, you can always upgrade the alternator if it doesn't meet your needs. Remember when they went to the CS alternators they were used on cars and trucks with fans and power windows, Locks etc.
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Old 10-24-2017, 12:39 AM   #4
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Re: too many amps, need better alt?

I agree with PG.

I would add up all your heavy hitters that could be on at once and at idle.
Like fans, fuel pump, AC, headlights and stereo.
I would dig out the DMM and measure voltage at the battery and alt to figure out what alt you need. Most alternators amp rating are at the max rating and not at engine idle speeds. So a 105 amp alt may only put out 65 amps at idle (800 RPM), and 105 amps at like 1200 RPM. Just something to add to the equation.
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Old 10-24-2017, 08:24 AM   #5
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Re: too many amps, need better alt?

Thanks guys! The consensus seems to be my alt ( 60-80A idle, 105A max ) will probably do the job just fine. If not, a couple hundred bucks will get me an easy swap to the next level at 140A or so down the road.

So at idle with fans spinning and the usual stuff on, my gauge should still read around 13 Volts at the dash? If I see it dip to 12 or below, that's no good right?

Thanks,

-klb
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Old 10-24-2017, 02:29 PM   #6
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Re: too many amps, need better alt?

Quote:
Originally Posted by weq92f View Post
Thanks guys! The consensus seems to be my alt ( 60-80A idle, 105A max ) will probably do the job just fine. If not, a couple hundred bucks will get me an easy swap to the next level at 140A or so down the road.

So at idle with fans spinning and the usual stuff on, my gauge should still read around 13 Volts at the dash? If I see it dip to 12 or below, that's no good right?

Thanks,

-klb
Correct. You should actually see around 14.3 volts running at idle. Use a digital multi-meter. Also a good indicator is if your headlights go dim at idle and get brighter when you rev it when all accessories are on.
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Old 10-27-2017, 10:11 AM   #7
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Re: too many amps, need better alt?

My formula:

Alternator should be running @ 75% capacity no more.

Total amp draw should be 75% of alt max amp rating. This ensures a good long alternator life.
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Old 10-27-2017, 03:06 PM   #8
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Re: too many amps, need better alt?

One thing I didn't see in your calcs are the wipers.

Very likely you could be running headlights, running lights, wipers, blower motor on max and AC + stuff needed to run the truck all at the same time. Quick test would be to turn all that stuff on at a bit above idle and watch the volts. If they stay up, you are good.

Don't worry about things like locks, windows and adjustable seats since the battery can easily supply them for the seconds they are on.
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Old 04-09-2019, 07:40 PM   #9
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Re: too many amps, need better alt?

Today I'm doing some testing in 85* outdoor temps. With everything on ( cooling fans on high, AC blowing on high, lights, radio wipers,...), I'm reading 12.5 volts at the battery, 13.5 volts at the alternator post and the gauge is reading around 12, likely closer to the battery reading but lower. This is at idle in neutral ( auto trans ) at about 675 RPM. In gear, the RPM doesn't drop very much.

Minus the lights and wipers, this is pretty much the norm for summertime driving in terms of the state of the charging system during stop and go summertime driving. At speed, the fans will kick off.

What do you guys think, is my alt keeping up well enough here at full load? BTW, most of the big draw items are wired directly to the alt post.

-klb
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Old 04-10-2019, 05:31 PM   #10
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Re: too many amps, need better alt?

Checked all the connections today and did some further measuring of things after a longer drive. Today I measured 12.4 volts at the battery, 13.3 at the alt post and the gauge was reading around 12. This while all the eletrics were on full blast.

Actually had to sit idle at a train for a good 10 minutes ( near constant cooling fan on high and A/C blowing - I think the fans cycled off once or twice ) before pulling up into the drive and measuring with the DMM. After killing the engine the battery measured 12.47 volts.

-klb
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Old 04-10-2019, 07:36 PM   #11
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Re: too many amps, need better alt?

I would be a bit concerned about the 1.0 volt drop alt to battery. Maybe start by putting a larger gauge wire from the alternator to the battery.

Where is the volt meter connected? Under the dash?
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Old 04-10-2019, 11:05 PM   #12
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Re: too many amps, need better alt?

Battery should be seeing what the alt is seeing for voltage. I’d like to see a diagram of how your power distribution is set up. Sounds like the remote voltage sensing is not liking however you have everything wired.
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Old 04-11-2019, 11:48 AM   #13
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Re: too many amps, need better alt?

Quote:
Originally Posted by 67 Burb View Post
I would be a bit concerned about the 1.0 volt drop alt to battery. Maybe start by putting a larger gauge wire from the alternator to the battery.

Where is the volt meter connected? Under the dash?
Will have to chase it down to determine...

Quote:
Originally Posted by gmachinz View Post
Battery should be seeing what the alt is seeing for voltage. Id like to see a diagram of how your power distribution is set up. Sounds like the remote voltage sensing is not liking however you have everything wired.
A PO installed a new harness, Painless I believe. It's going to be an adventure tracing down the leads to figure out exactly how it's all wired up. The gauge of the leads connected to the alt all appear to be on the small end of the scale and none of them make a direct path to the battery. Appears to me any path to the battery goes through the fuse box, probably through the volt gauge and through some other wiring that is definitely not of the proper gauge.

The cooling fans pull directly from the battery. If the alt doesn't really have a direct circuit to the battery, could the amp draw of the fans on the battery cause damage to the wiring ( possible fire ) between the alt and the battery due to the draw?

As you may have figured, I'm not a great electrical guru!

-klb
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Old 04-11-2019, 12:09 PM   #14
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Re: too many amps, need better alt?

Well the problem I have with Painless and even AAW to a degree is that they follow pretty damn close how GM originally designed the circuits...complete with shortcuts, barely adequate wiring sizes and type, etc. There should be more of a focus on modernizing the electrical circuits but thats more difficult to do that to just copy GM 100%.

The various power leads do need fused protection BUT-there should not be any accesssories pulling directly from the battery-instead all power runs should come from a single common +12 junction-and from that junction the alternator remote voltage sensing wire also needs to land there. The reason is because its easier for the voltage regulator to adjust to changing voltages if it is directly upstream from all sources of power-everything passes thru sort of like a floodgate and the regulator will try to maintain system voltage of 14V or so.

Now, if you are running multiple things and pulling power from different places, the alternators’ regulator can’t “see” the changes in voltage demands as easy so it has a hard time keeing up....thats why there is imo a significant amount of voltage drop (over 1V) in your system. Moreover you have:

Too many power runs
Not large enough wire diameter
Too long of wire lengths
Not updated enough to run modern accessories

This isnt to say what you have now wont work or continue to, I’m just saying its not optimal-alternators don’t like being overworked...and not running a sustained higher voltage (over 14V) makes it tuff on any alternator to live a long life. And consequently, your accessories wont live as long either. 12VDC things like actuators, motors, etc are designed to run at 16V, so the closer you can get to that the less amperage they require to do the work. So if that alternator is hovering around a system voltage of 12-12.5 all of your devices are pulling more amperage than they would use at 14V. That is why bigger is always better with regards to wire sizing and the charging system-but it needs to be thought out.
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Old 04-11-2019, 01:03 PM   #15
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Re: too many amps, need better alt?

.
Thank you for this explanation, really helps me understand what may be happening.

Before adding the fans, the system was OK. Adding the fans and particularly my decision to wire the relays to the battery ( through a breaker ) has pushed it a bit too far.

There are other accessories that are direct draw from the battery as well for example the headlight relays are wired there.

All of these power leads should be combined onto a common distribution block along with those that are wired directly to the alt post and then a larger gauge lead should be run from the alt post to the block? Then the block would be connected to the battery by an equally large gauge cable...say...6?

-klb
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Old 04-11-2019, 02:43 PM   #16
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Re: too many amps, need better alt?

Yes-I think that will eliminate most of your voltage loss. Let us know before/after results too! So take a reading at the alt post before and after as well as at your interior fuse panel batt cavities before/after.
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Old 04-13-2019, 01:01 PM   #17
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Re: too many amps, need better alt?

.
After further review...

I think I'm understanding this a bit better now. First, I don't have a CS-130. That was a miss on my part. It's a CS-130 looking case but it's a single wire alt made by tuff stuff.

There are 3 leads attached to the single pole. One to the starter solenoid, one to the main fuse panel power and the other powers the relay bank for headlights/horns.

The cooling fans, starter and a few other leads are connected directly to the battery.

Given this, I think what I need to do is go back to a 3 wire internally regulated alternator so that I can use the remote sense wire to keep 14 volts at a common power distribution block where everything gets power.

That is, unless there is a way to wire the one-wire alt to emulate the same setup?

-klb
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Old 04-24-2019, 12:23 PM   #18
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Re: too many amps, need better alt?

.
So... researching these one-wire alt's I'm finding there are two types of people: those that like them and those that do not!

Both Powermaster and Tuff-Stuff markets a portion of their alts as being capable of both OEM hookup and one-wire hookup. However after a good deal of effort I've been unsuccessful in getting either company to commit to me that their product does or does not actually do remote sensing of voltage like the OEM CS ( et al ) style alternators do.

Either by phone or email, both companies are very quick to quote their own marketing material by stating that their products will work with OEM hookup or one-wire but when asked directly about the remote sense capability, they go numb and become unresponsive. On the SummitRacing website, one of the TuffStuff products has an accompanying image that indicates their OEM Plug is a dummy, that it isn't connected internally and is inoperable.

A shame really that these guys are out there misleading consumers with this crap.

Back to the problem...

As an interim solution, I've moved the cooling fan lead to the alt post since that is where the voltage sensing is happening in this setup. This made one interesting difference: when the fans kick on, the additional load on the system no longer bogs the engine down temporarily like it did before. The alt must be sensing the load now immediately and compensating somehow without needing to put too much strain on the engine? Maybe the fans were pulling the voltages down far enough system wide to affect the idle in other ways via the EFI unit, coil, fuel pump, etc. before the alt compensated?

At some point in the near future I'm going to rewire this as discussed before so we have a common distribution point that gets fed from the alt. Regardless of it being a one-wire, I'm thinking this will be the best route to go.

Pretty sure I'll not be purchasing any products from these two companies though.


-klb
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Old 04-24-2019, 04:41 PM   #19
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Re: too many amps, need better alt?

most self exciting regulators have a higher voltage set point that will help with downstream loss. the cs 130 se regulator set point is 14.6 volts in the two suppliers I checked. the 10si regulators are 14.8 volt set point.
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Old 04-29-2019, 01:41 PM   #20
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Re: too many amps, need better alt?

Hard to beat the CS144 alternator upgrade as a good insurance against insufficient juice.. Calculating loads this way neglects the fact that recharging the battery after a few minutes of changing or a long spell of non-use can pull 30+ amps for several minutes.
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Old 05-02-2019, 02:11 PM   #21
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Re: too many amps, need better alt?

There is a lot of good information in previous post, but you have some equipment like a digital multi meter but do you have an amp clamp? I have two from Fluke that are expensive, but one from PICO and the other is a digital read-out from craftsman. I checked and measure / tested it against the others...real close and I was surprised as many on the market are $25-$35.

When you have a fan(s) or any electrical device in a series circuit, even a bulb(s), when you turn them on, they have cold copper windings or filaments. There is a brief in-rush of current or higher amps, then quickly drops the amperage during the on or continuous use. Please take this into mind to make a list like you did and take an amp clamp and take an actual reading.

Fuses are thermal devices that open when they get too hot, but inside the cab is cooler than the engine compartment, and those fuses inside will open when hotter and the ones in a hot engine compartment.

Using your DMM to check voltage drop is "Best Practice" when it comes to making sure everything electrical is correct and will not cause a problem now or later. The thing to remember is the higher the amperage, the higher the voltage drop. A high amp circuit on the B+ side and ground side (Often Overlooked) will be closer to 0.500 volts. Low amp circuits will have or should have closer to 0.050 amps. A dedicated ground found on sensors to the PCM/VCM will go into the PCM/VCM, thru it, out one of 3 or 4 grounds to connector G100, should measure 0.400 max. This is industry standard for the PCM sensor ground circuits.

I agree that 1.0 volt drop or loss between the alternator to the battery is too high. If the battery is a top post, use the post first and connector second to see if there is a difference as this will show a cleaning is needed. If the battery is a side terminal type, go to the center bolt and then get under the cables rubber PVC cover and check again. Side terminal batteries can leak into the cable and will cause huge resistance and not be seen.

If it all adds up to more than what you alternator produces, yes you may consider a AD244 that is rated at 144 amps to 130 amps is what GM shows.

So, check actual amperage on main circuits you have or are concern with and write it down. Fuses will handle a temporary in-rush of higher current due to cold windings. Do not forget larger gauge wire for grounds everywhere including frame to bed, frame to cab, cab to back of engine, battery ground to engine, ground to front fender, perhaps a ground from engine to frame at front.

Then check and do the positive cables as well. I use dielectric grease on all connectors, bulbs, flashlight, smoke detector, digital multi meter, everything. May it's too much, but works for me.

The AD244 or the newer DR44G can be mounted on the vehicle with a little effort and 1 wire regulators are sold everywhere with a 14.8 volt set point and 2.5 second turn-on time after starting. I use alternator man.com

Remember the battery as well. A good battery in open circuit will measure at 12.8 volts. A battery with 100% state of health will only require less than 0.03 volt to charge it going down the road. GMs' new Load Shedding logic controls the alternator using PWM to reduce engine load for fuel economy, and a TECH2 will show this activity going down the road.

Best of luck. (See below)
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Old 06-05-2019, 07:01 PM   #22
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Re: too many amps, need better alt?

.
Thanks for all the input everyone!

Finished this off today... Also added an A/C trigger to my EFI unit which will kick up the throttle slightly and turn on fan #1.

I'll report whether this makes any difference when I get it all buttoned up.
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Old 06-08-2019, 01:39 PM   #23
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Re: too many amps, need better alt?

.
Under load w/fans and headlights on, engine at idle I'm seeing 13.5v at the distribution block.

At cold start it's just over 14v at the block.

What do you guys think? Alt is weak? It's a 5ft 6awg cable from alt to dist block.

-klb
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Old 06-08-2019, 02:15 PM   #24
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Re: too many amps, need better alt?

Nope, Its all fine. What you are seeing is voltage drop on a high current circuit. Remember, low current is less than roughly 30 amps, so across the wire from connection to connection will show this drop of 0.300 volt DC to 0.600 volts DC. High current over 50 - 60 amp of more, you can expect to see 05.00 volt DC or 1/2 of one amp. You are test for a simple voltage reading at two locations showing the difference in supply as compared to distribution where the current is split out into many circuits. Your difference is 5 volts. Now, use and amp clamp to find the actual current being used on each circuit. If you don't have one or don't need to see the current, then take you DMM from the battery positive to the positive wire at the distribution block voltage supply. Then you will see the loss or drop in voltage.
Yes, you can install a large gauge wire, but only slightly less drop in voltage. Say you have some really good jumper cables sitting around. One with more copper wire than insulation. Connect one end to your battery, the the same end to the bolt of your distribution center. It will like installing a large gauge wire. Then is you can do this safely, take you DMM and take the same reading again. Changes are, they will be near the same.
Digital readout amp clamps have come way down in price over the last decade and are surprisingly accurate. Get on the has DC and a clamp the is not too large nor too small. It can show each circuit and tell you how many amps are going thru it. Add them up at you distribution block, then check how many amps are coming out of the alternator at the same speed. It will add up real close to actual amperage being used. If you have a friend that can hold the engines speed at say, 1,500 RPM's, then measure at the alternator again.
Remember, some current is used to charge the battery depending on it's condition and how long it's been since you started it. Give it a chance to charge up with the engine running, then take you tests.
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Old 06-08-2019, 03:12 PM   #25
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Re: too many amps, need better alt?

Quote:
Originally Posted by LH Lead-Foot View Post
Nope, Its all fine...
About the least expensive DC current amp clamp I'm seeing is a 50 dollar model on Amazon. While I would like to know the exact numbers, that's a bit steep for a tool that I'd rarely use. I'll check around see if a neighbor has one I can borrow.

-klb
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