Reply
 
Thread Tools Display Modes
 
Old 03-14-2015, 11:59 PM   #1
Senior Member
 
xcnick's Avatar
 
Join Date: Jan 2013
Location: Lake Tahoe
Posts: 214
Does alternator know how many amps to send to the Battery?

I get that when the battery volts are lower than the alternator then it sends juice to the battery. However I have the big alternator, 95 amps, and there is no way it is sending that much to charge or at least I hope not, the wire to the coach battery is too small for one thing. I have the Sure Power 12023A isolator if that has anything to do with it. But my question is for the van battery as well.
__________________

__________________
1996 Ford EB 2 wheel drive 460
xcnick is offline   Reply With Quote
Old 03-15-2015, 12:30 AM   #2
Senior Member
 
E350's Avatar
 
Join Date: Oct 2010
Location: Sacramento Delta, CA
Posts: 1,011
Re: Does alternator know how many amps to send to the Batter

I asked the same question on a different forum and this is the answer I got:

"The regulator controls the amount of current to the field circuit in the alternator, basically making the rotating magnet stronger or weaker to maintain the output voltage.

It does this by switching the circuit to the field, very fast, up to 100hz.

The output from the stator is not switched at all and is connected to the battery."
__________________

__________________
2002 E350 ext.; 160K; 7.3L; 4R100 (w/4x4 deep pan & filter); 4x4 conv. w/2007 F250/F350 coil frnt axle (oppos. dual Bilstein press. shocks cured DW) diff chg from 3.55 to 3.73 (bad!); BW1356 t.c. (bad!); LT265/70R17/E Michelin LTX M/S2; Engel MT60 Combi Fridge-Freezer; 4 BP 380J pv panels; Auragen 5kw AC gen. in top alt. position; Webasto Dual-Top; Voyager top. 1995 5.8L EB Bronco, bone stock.
E350 is offline   Reply With Quote
Old 03-15-2015, 01:15 AM   #3
Senior Member
 
xcnick's Avatar
 
Join Date: Jan 2013
Location: Lake Tahoe
Posts: 214
Re: Does alternator know how many amps to send to the Batter

Thanks E350. Technical, but still understandable. So if my house battery is very low I wonder how many amps it takes to equalize the volts and by implication how many amps are going to the battery?

It seems a crude way to charge compared to a fancy 3 or 4 phase charger one might use at home.

But the scary thought is having a dead cell in the house battery and the voltage would never come up. Then would the alternator try to give it all the available amps? Giving some 80amps down 20 feet of #10 wire sounds like a fire about to happen.
__________________
1996 Ford EB 2 wheel drive 460
xcnick is offline   Reply With Quote
Old 03-15-2015, 12:17 PM   #4
Member
 
Join Date: Jul 2013
Posts: 37
Re: Does alternator know how many amps to send to the Batter

from my understanding the battery determines how much amps it will get. Even if you have a 95 amp alternator capable of putting out 95 amps, the battery will only take what it needs. if its completely empty it might take it all, but as it fills up it takes less. Amps are always available but its the voltage that forces it into the battery.

I run my own tests with different agm batteries to see if I could overcharged them. For my tests I use my solar panel which can produce 12 amps and also a seperate small triton 7 amp dc charger. All the batteries were fully charge. 145ah agm, 102ah agm, 35ah agm, 28ah agm, and 17ah agm.

Both solar controller and dc charger recognize a full battery and went into float mode. The only thing I notice the larger the battery the more amps it took in the float mode. I ran the tests many times and always got the same results. Its almost impossible to overcharge or damage a full battery. My conclusion is that a full battery will only take minimal current. My house battery is inside my van and i wanted to see worst case scenario, and feel safe having the battery where its at.

About the bad cell, if the other cells are full, I suspect the alternator will have the amps available but the battery wont take it. From what I read about destroyed batteries is that it wasnt the amps that killed it but the volts. If something fails in the alternator side and voltage goes over 15 volts, that will destroy the battery.
You can always put a fuse between the alternator and your battery to protect the wire just in case.
For myself I have fuses on all the wires that connect to my battery.
jony101 is offline   Reply With Quote
Old 03-15-2015, 01:46 PM   #5
Site Team
 
daveb's Avatar
 
Join Date: May 2007
Location: Turlock Ca
Posts: 9,878
Garage
Re: Does alternator know how many amps to send to the Batter

Quote:
Originally Posted by xcnick
Thanks E350. Technical, but still understandable. So if my house battery is very low I wonder how many amps it takes to equalize the volts and by implication how many amps are going to the battery?

It seems a crude way to charge compared to a fancy 3 or 4 phase charger one might use at home.

But the scary thought is having a dead cell in the house battery and the voltage would never come up. Then would the alternator try to give it all the available amps? Giving some 80amps down 20 feet of #10 wire sounds like a fire about to happen.
I've had a starting battery go bad (shorted cell) and the inverter/charger was pumping out just under 50 amps IIRC. I do not know if it could have began to pull more as the failure continued. To be honest I don't know what the max output is on my shore charger. It was obvious something was wrong because the battery was too hot to touch. But it was the smell that told me something was up even though I should have read the gauges and figured out something was failing long before it off gassed.

I've never seen an alternator put out what they are classified as... Could be wrong but a 200A alternator never seems to supply a 200 amp charge or at least that is what I've found. #10 wire should handle 55A so yeah that can be kind of close from what I saw a dead shorted battery was pulling. Just from field experience, I've rarely see my two 210AH house batteries pull more than 30 amps when dropped to 50% of charge and that tapers off rather quickly as they start to charge up. But if you run a microwave that is a different story. Mine pulls like about 70 amps so things can get loaded up with more stuff running but I've always figured much of the draw comes from the battery bank and not just from the charging system.

I've never researched isolators but would guess there is a limit to the amount of current they pass (depending on the model) as well, so a breaker and a amp gauge might be a good idea.

I've got #4 copper from the battery to my Blue Sea two-way separator so the only time I worry is when trying to use the house to start the engine with a dead starting battery system.

Have you ever measured your max load?
__________________
2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer

Sportsmobile 4X4 Adventures..........On and off road adventures
daveb is offline   Reply With Quote
Old 03-15-2015, 02:19 PM   #6
Senior Member
 
xcnick's Avatar
 
Join Date: Jan 2013
Location: Lake Tahoe
Posts: 214
Re: Does alternator know how many amps to send to the Batter

Quote:
Originally Posted by daveb
Have you ever measured your max load?
No, I don't have a tool that can measure this many amps. However this begs a good question. How do I add amp gauges into the van?

My house battery is inside like Jonny101 and I glad to see someone else has the same fears. I am thinking more about this because I want to add a second battery. My thought is to just run a second wire from the isolator to the second battery. If #10 worked for one battery, 2 10's should work for 2 batteries. Actually I am guessing it is 10, could be 8.

I don't have an inverter attached to house battery, so I don't think the load is ever more than 10 amps. (Fridge 2.5, TV 2.5, LED lights) Therefor my worry was how much I would draw when the two batteries are low and I just let the engine idle for half an hour. Hot weather, van stationary, small wire, big draw, could be a bad thing.
__________________
1996 Ford EB 2 wheel drive 460
xcnick is offline   Reply With Quote
Old 03-15-2015, 03:22 PM   #7
Site Team
 
daveb's Avatar
 
Join Date: May 2007
Location: Turlock Ca
Posts: 9,878
Garage
Re: Does alternator know how many amps to send to the Batter

Depends on what you want to measure. I measure my loads not just the charging current. There was a post some time back about installing flush mounted multi-meters. I'll see if I can find it.
As far as wire size, adding another battery can be a factor. Larger batteries can pull a fair amount of current to recharge from what I've read although I've never seen those higher values on my build. There are wire sizing charts in the FAQ's. You just need to know what kinds of loads you'll apply to the bus wire. I didn't know until I cranked up everything in my van and read what my gauge said. The microwave is the big hog.
__________________
2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer

Sportsmobile 4X4 Adventures..........On and off road adventures
daveb is offline   Reply With Quote
Old 03-15-2015, 03:43 PM   #8
Senior Member
 
xcnick's Avatar
 
Join Date: Jan 2013
Location: Lake Tahoe
Posts: 214
Re: Does alternator know how many amps to send to the Batter

Thanks, I have a wire size chart. I just don't know what the amps will be.

Any recommendations for inexpensive tool to measure this many amps? My Harbor Freight multi meter is not going to be happy with this task.

It does seem I am going to have to let the battery drain and then start up the van to know for sure.
__________________
1996 Ford EB 2 wheel drive 460
xcnick is offline   Reply With Quote
Old 03-15-2015, 05:59 PM   #9
Senior Member
 
Scalf77's Avatar
 
Join Date: May 2007
Location: Beaverton, OR
Posts: 1,604
Re: Does alternator know how many amps to send to the Batter

For the Sure Power 12023A isolator they recommend 6 gauge with a 50 amp fuse/breaker for 15 to 20 ft runs and 4 gauge with a 50 Amp fuse/breaker for 20 to 25 feet. So if you had 10 Gauge wire, it would not be installed correctly, and you should also have a fuse/breaker. The size and/or number of batteries is not the driving factor here.

The existing loads to run the Van, lights, stereo, heat/aircond will take up a great deal of the available current your 95 Amp alternator is putting out. A seriously low battery or one with a "shorted cell" will cause the alternator to put out its maximum current. Working a alternator at maximum output for a long period of time will cause your alternator to have a shorter life

Also remember at idle, your also not putting out max power

-greg
Attached Files
File Type: pdf BUS_CBT_INST_180012q.pdf (3.04 MB, 7 views)
__________________
2004 E350 EB V10 E/PH 2WD
Scalf77 is offline   Reply With Quote
Old 03-15-2015, 07:25 PM   #10
Senior Member
 
xcnick's Avatar
 
Join Date: Jan 2013
Location: Lake Tahoe
Posts: 214
Re: Does alternator know how many amps to send to the Batter

Quote:
Originally Posted by Scalf77
So if you had 10 Gauge wire, it would not be installed correctly
My thoughts exactly, but I bought a used 96 so it is a little late to point that out to sportsmobile. I first started wondering when I saw the wire was laid next to factory wiring that runs close to the driver side exhaust. The factory wires are all in some kind of heat resistant tape and a loom. The wires from Sportsmobile are run in radio shack plastic loom and it is all melted away.

Not that I am any better. As a redneck electrician I am trying to figure out if two #10 wires equals one #6.
__________________

__________________
1996 Ford EB 2 wheel drive 460
xcnick is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

» Sportsmobile Registry

The Yeti

TexGX

Blue Buffalo

BigBrap
Add your Sportsmobile
Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by Sportsmobile SIP or any of its affiliates. This is an independent, unofficial site.


All times are GMT -6. The time now is 03:21 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
×