Voltage Fluctuations - why?

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Superjuice..
The curious issue is the "change" from 14.2 to 13.8 then back to 14.2. Typically a regulator will hold the generator at a ONE specific voltage. It's uncommon to see the output voltage to shift around like described.

I don't have a wire diagram to see if there any other controls at play affecting the output voltage. The newer regulators use an IC controller instead of discrete electronics. It could be possible this is the way it should work but I doubt it. There could be a bad connection or a bad sense wire (S) to the alternator.

I think the regulator is starting to shoot cr^ps and eventually he'll cook his battery.

rhyary: How did you hook up the voltmeter ?
 
My blue sea is the 500amp, not the 120amp one.

The battery tender was charging at 14.53. Have not see this with the alternator.

Now my aux battery reading 12.8 at rest. Given the ambient temp, I would say this is 100% Charged AGP deep cycle battery. The starting battery is at 12.6 as it should. The starting battery was not on the charger. The two are isolated when the truck is off.

What will be interesting to see is for how long the AGP 31M deep cycle will stay at rest on 12.8 given my short commute and the fact that the ham radio is on running in it.

It has not been on 12.8 in quite some times. Typically resting on 12.55.

If I can charge it from the house once a week and it will give me 12.8 for a week, then I will adapt this practice with the hope that the deep cycle will last more than 5 years.

Lastly, to the contributors that think I make too much of it, the high rate of deep cycles battery failure in this crowd will have to be explained. However, I certainly not going to debate sun spots on a technical section. We, after all, have the chit-chat for that. To keep this discussion on target, we can assume that the instrumentations are correct. I double check every thing with two other voltmeters, so between my in dash volt display, inexpensive west marine meter and an expensive meter they all correlate.

There is inherit problem with the deep cycle batteries and short commute (up to an hour or two) that causes the deep cycle to not get to 100% charge

I am only collecting evidence at this point and offer observations. Of course the Mud user is free to disregard this thread or any other of my threads.
 
StopGap,
It is hardwired to the batteries via a three way switch as a picture depicts.

Please note that I don't have wild fluctuations. Sometimes it settled on 13.8, and then settled in 14.2. I agree that I expect it to settled on 13.8 as float.

Don't think 14.2 will cook the batteries. It is still with in normal range, although I can't explain it.
 
You may want to check this out as well from Photomans bracket post. Grounding issue.
https://forum.ih8mud.com/80-series-tech/206807-upgrading-stock-alternator-130-150-amp.html


Post 180 https://forum.ih8mud.com/80-series-...ock-alternator-130-150-amp-9.html#post5341226

low charging voltage, FIXED!
--------------------------------------------------------------------------------

So I've been running the 150amp for awhile and started off charging fine, 14.15 volts. Recently the voltage started to jump around and settle about 13.5. So i tightened the belts and got it up to about 13.8, still low. After checking all my wiring i tested the voltage from the positive to the alternator case....14.38WTF. I contemplated running a ground directly from the case from one of the available threaded holes...i shouldent need to do this though. After looking over the instructions again i just cranked the 5/8ths through bolt with the nut on the back, hoping to make a better ground and BINGO! back to 14.15. I'm still losing .13 volts from the alternator case to the battery but i guess i can live with that, must be some resistance through the engine/frame. What to you guys think, is that about what you're seeing? Any thoughts on directly grounding the alternator to the frame or battery? Hope this helps someone else that may be seeing some voltage drop, even if they didnt realize it

I forgot to crank down the 14mm pivot bolt, it was very loose, now my voltage drop is only .02

Just an idea to check since it fluctuates.
 
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I had the same experience with my 150 amp. bolt. Found it the same way, voltage dropped at battery negative but not at the alt. case. Tighten the belts, better...tighten the bolt, FIXED! I think the fact that that pivot bolt isn't threaded but instead has a nut on the back makes for a weaker connection. I also had the thought to use one of the threaded holed as a secondary ground but didn't have the correct bolt/screw on hand.

I realize this might not explain the fluctuations this time but it should be checked periodically.
 
Rami,

I don't think it would be a problem on short trips, longer trips (4hrs) it will limit your battery life. Batteries charge at just under 14.4 volts, depending on plate alloys and separator materials. Above 14.4v the battery starts gassing. If you,re driving an hour it won't matter much. If you're driving a while and often, continuous 14.4vdc could shorten the battery's life by corroding the plates.

I did a little more research and it turns out there are a series of chips made for alternators and charging lead acid batteries. The ICs are meant to boost the charge voltage when turned on and revert to float voltage. If the sense voltage is lost, the chip executes a charge strategy similar to the initial charge cycle.

I think there is either something wrong with your sense wire/connections or the regulator is going bad.
 
StopGap,
Please note that my alternator is maintaining on 14.1 to 14.2. Not 14.4.

If it ever gets to 14.4, it will be for a short while after a very cold start. As it should.

On a long trip it will be on 14.1.
What I don't understand is why it will settle on 13.8 after a while, for awhile and go back up to 14.1.

I understand about the gassing process.
 
Even though there is only 0.4vdc rise in voltage it is significant for deep cycle battery life spans. I'll go back to the original assertions.

1) The volt meter is not correct. Since the 13.8vdc and the 14.2vdc has been independently verified at the battery, we can ignore this item.

2) Battery or alternator wiring is bad, inducing an artificial rise in voltage. I don't buy into this idea due to the nature of the voltages. Tighten everything you can. BTW, poor voltage and ground connections usually produce the opposite effect -->low voltage

3) Sense wire is poorly connected or broke internally. As far as I know this has not been checked. Depending on the vintage of the regulator installed the 14.2vdc could be a result of sense voltage failure.

4) The voltage regulator in the alternator has failed, unpredictably producing the 14.2vdc.

5) This is the way the regulator should work. I've never seen this before and doubt its correct.

6) Sunspots and Zombies :D

I think 3, 4 and 5 are your best bets as an explanation. Since you don't like any of these, I guess you should be prepared to live with it and deep cycles batteries with a slightly shorter life.

cheers, gary
 
Rami,

I found your problem. You mentioned in post #7 you bought an isolator: "This is a the blue sea switch that comes with the blue sea isolator."

You purchased an ACR (automatic charging relay) not an isolator. This allows flow both ways unlike an isolator that only allows flow of current one way. ACR's are used for multiple banks of batteries not just two batteries like an isolator.

The fluctuation is how all ACR (automatic charging relay) systems work. This is done by the relay position setting see below.

This is off blues web site: ML-Series Automatic Charging Relays (Magnetic Latch) - Blue Sea Systems

Live Current Switching 300A @ 12V DC - 10,000 Cycles
Relay Contact Position
Combine (30 sec.) 13.5V @ 12 Volts / 27.0V @ 24 Volts
Combine (90 sec.) 13.0V @ 12 Volts / 26.0V @ 24 Volts
Open (10 sec.) 12.35V @ 12 Volts / 24.7V @ 24 Volts
Open (30 sec.) 12.75V @ 12 Volts / 25.5V @ 24Volts
Open High 16.2V @ 12 Volts / 32.4V @ 24 Volts

Here is a page that better explains it: Automatic Charging Relay (ACR) Explained - Resources - Blue Sea Systems

You for sure have the ability to run many batteries off of it. ACR's are super HD for a dual system.

A little over kill for a dual battery system. None the less I want one just for your cool switch. LOL
 
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Offroad4x4,
I am not sure why is the ACR a problem. After about 90 second the ACR combine both batteries and both batteries are electrical one system. In addition, the switch allows me to manual disconnect the batteries so only the starting battery is in the loop. I suppose I can run the car for a day or two with only the starting battery and see if it makes a difference in terms of the fluctuation.

But it looks like you found something I am not aware off. Clue me in.
 
Sorry bad choice of words.

ACR is not a problem it was the anwser sort of speak. We were all looking to find out anwsers relitive to an isolator and how they act to anwser your original question.
ACR's and isolators are two different units doing like jobs. ACR's can pull from one battery to the other while isolators will not pull back any voltage only combine batteries. In the last link above it should explain the ACR better than i can here. If it doesn't anwser it good enough there is contact info at the bottom for a direct phone line to Blue Sea.

Your ACR should work fine for your application just super HD.

Like you said it is working fine just jumping up and down voltage wise.
 
I have scanguages on both my Subaru and my Land Cruiser and in both cases the voltage changes all the time and not necessarily with rpms or things turning on and off.

However, unless you run your rpm at one exact speed all the time, which obviously none of us can do, I think you might be under estimating the affects that the change in rpms will have on the alternator as your drive along. Even at idle, the engine speed will change or fluctuate slightly and if anything turns on like th defroster or AC that will have an affect also.

In my experience, changes in voltage doesn't harm batteries. What harms batteries is if they are left connected while the engine or charging system is disconnected and one battery has a slightly less charge than the other, which is almost always the case. The batteries will then try to discharge each other, eventually destroying one or the other. I've killed a few Optima yellow tops this way years ago.

Now my system makes sure both batteries are always disconnected from each other when the engine is turned off and they've lasted several years now with no issues.
 
Offroads4x4,
Got cha'. I did extensive reading including talking to Blue Sea tech support BEFORE purchasing so I believe I know what I bought. You just made me nervous for a minute. We all set.

Brian894x4,
Mine are disconnected automatically when the engine is off. They are reconnected automatically 90 second into the charge. Not only that, but when I start the engine, the ACR automatically disconnect the batteries so that electronic devices connected to the second battery don't receive the spikes from the starter. It is described in the link Offroad4x4 provided. The fluctuation are not within second but within minutes. If I am on 13.8 it may be there for 5 or 10 minutes. Conversely if I drive to two hours, I may get 14.1 for a long time, more than you would think, and it should get to float voltage at some point.

As a data point my charge today behaved EXACTLY the way I want it. I had a longer commute today. So after start it was charging at 14.3 then went down to 14.2, 14.1 eventually after 20 minutes settled on 13.8/13.9. Exactly what I am after.

I am curious if on the reverse commute it will behaved exactly the same. Mondays I have a longer commute. It is also after I topped off the Aux battery with the battery tender on Friday overnight.
 
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