Leftover from the alternator

[peer oliver schmidt]

Good Morning America,

anyone ever made some tests to determine how much of a 80amp or 100amp
alternator ended up in the house battery on an average day of driving?
Looking at more recent RVs I see alternators exceeding 200amp, and I
wonder if todays cars need more amps, or if they are just able to
provide more charging.

Inquisitive mind wants to know Thanks a bunch.
--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, VA

 

[Jim Hupy]

Peer, electrons are kinda like water, you can only pour them into the
battery until the bucket is full, then it won't hold any more. With an
alternator, you are dealing with CEMF or counter electromotive force. If
you have the same number of electrons on both sides, then, no more
electrons will flow, except when some are being used by resistances in the
circuit. Then, that much will be allowed by the regulator in the
alternator. If you are driving down the road, the ignition is using a few,
the occasional use of the turn signals and brake lights use a few, the
heater blower uses some, etc. Does not matter much what the real potential
of the alternator is, only what the demand is.
Jim Hupy
Salem, Or
78 GMC Royale 403

On Tue, Nov 15, 2016 at 8:04 AM, Peer Oliver Schmidt GMC <

> Good Morning America,
>
> anyone ever made some tests to determine how much of a 80amp or 100amp
> alternator ended up in the house battery on an average day of driving?
> Looking at more recent RVs I see alternators exceeding 200amp, and I
> wonder if todays cars need more amps, or if they are just able to
> provide more charging.
>
> Inquisitive mind wants to know Thanks a bunch.
> --
> Best regards
>
> Peer Oliver Schmidt
> PGP Key ID: 0x83E1C2EA
>
> '76a Eleganza II, VA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Gene Fisher]

Read here
http://www.gmcmhphotos.com/photos/buzz-box-converter-problems-and-replacement/p17534.html

> Peer, electrons are kinda like water, you can only pour them into the
> battery until the bucket is full, then it won't hold any more. With an
> alternator, you are dealing with CEMF or counter electromotive force. If
> you have the same number of electrons on both sides, then, no more
> electrons will flow, except when some are being used by resistances in the
> circuit. Then, that much will be allowed by the regulator in the
> alternator. If you are driving down the road, the ignition is using a few,
> the occasional use of the turn signals and brake lights use a few, the
> heater blower uses some, etc. Does not matter much what the real potential
> of the alternator is, only what the demand is.
> Jim Hupy
> Salem, Or
> 78 GMC Royale 403
>
> On Tue, Nov 15, 2016 at 8:04 AM, Peer Oliver Schmidt GMC <

>
> > Good Morning America,
> >
> > anyone ever made some tests to determine how much of a 80amp or 100amp
> > alternator ended up in the house battery on an average day of driving?
> > Looking at more recent RVs I see alternators exceeding 200amp, and I
> > wonder if todays cars need more amps, or if they are just able to
> > provide more charging.
> >
> > Inquisitive mind wants to know Thanks a bunch.
> > --
> > Best regards
> >
> > Peer Oliver Schmidt
> > PGP Key ID: 0x83E1C2EA
> >
> > '76a Eleganza II, VA
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[peer oliver schmidt]

Hmm, thanks.

It doesn't really answer my question, probably because I worded it wrong.

Let's try again:

a) The alternator feeds the chassis battery until the alternators
voltage and the chassis batterie's voltage are identical.

b) Depending on the type of chassis battery and the amount of left-over
amperage the time it takes to fill-up the chassis battery changes.

How much is that left-over amperage? I assume, with a 100amp alternator,
it must me over 20amp, which would be available to fill up the chassis
battery and the house battery, given a good charge regulator in-front of
them.

How wrong are my assumptions?

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, VA

 

[Jim Hupy]

Peer, if you are coming off a period of prolonged use of the house
batteries and their voltage (potential) has dropped a bit, then both the
rate of charge (amperage) and the duration ( length of time until equal
potential is achieved) will increase. This will be affected somewhat if the
alternator is wired through an isolation diode. Can't be too exact here, as
this is hypothetical.
Jim Hupy

On Nov 15, 2016 11:24 AM, "Peer Oliver Schmidt GMC"
wrote:

> Hmm, thanks.
>
> It doesn't really answer my question, probably because I worded it wrong.
>
> Let's try again:
>
> a) The alternator feeds the chassis battery until the alternators
> voltage and the chassis batterie's voltage are identical.
>
> b) Depending on the type of chassis battery and the amount of left-over
> amperage the time it takes to fill-up the chassis battery changes.
>
> How much is that left-over amperage? I assume, with a 100amp alternator,
> it must me over 20amp, which would be available to fill up the chassis
> battery and the house battery, given a good charge regulator in-front of
> them.
>
> How wrong are my assumptions?
>
> --
> Best regards
>
> Peer Oliver Schmidt
> PGP Key ID: 0x83E1C2EA
>
> '76a Eleganza II, VA
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Matt Colie]

> Good Morning America,
>
> anyone ever made some tests to determine how much of a 80amp or 100amp alternator ended up in the house battery on an average day of driving?
> Looking at more recent RVs I see alternators exceeding 200amp, and I wonder if todays cars need more amps, or if they are just able to provide
> more charging.
>
> Inquisitive mind wants to know Thanks a bunch.
> --
> Best regards
>
> Peer Oliver Schmidt
> PGP Key ID: 0x83E1C2EA
>
> '76a Eleganza II, VA

Peer,

I might be a a better position to answer this than most.

My 73 coach has an 80amp model alternator. If we have dry camped for a couple days and I crank up the main engine, and it comes up to 1300, the
instrument reports about 80 amps for a short time. I do not have any monitor except voltage on the starting battery, but at that same time, it will
show a terminal of about 13.8. Guessing from the charge curves, that terminal would be a charge rate around 20amps. This is what I would expect to
see after just cranking the main engine to start. That usually takes about 8 or 10 compressions to fire. If you are not aware, 23s have the house
bank in the front and mine is a pair of GC2s. I believe this is why I had trouble with the alternator belt. I know from boat work that 100amps on a
12V (13~15V) system is where any single V-belt runs out of sense of humor. I can also tell you that it will take about 4 hours of driving to get the
monitor to say that the house bank is at 90%. The house bank is will have been being charged at 14.8 that whole time. I would like to get this down,
but that just is not easy to do. Programable voltage regulators are available, but for me, the cost/benefit ratio just is not there.

Why do new cars have 200amp alternators?
Because passcars now have outrageous electrical demand. Think about the heated stuff: Not just back windows and mirrors now. There are also seats
and steering wheels. Then, think about the power that is now used by the engine controls. I almost didn't mention the other stuff.....
Then, when testing a new platform, we were often told to move the vehicle at lease 4 times a day and never more than one half mile. It takes about a
week of that to screw things up.
Did you notice the bundle of wires in those new alternators? They go to the ECU. The alternator is off-line for a short time after a cold start and
the ECU eases it back in slowly and manages the idle while it does. If it just threw the load back on the cold engine it will stall it. I can
actually have that problem if I am not careful with the after dry camp cold start. I can survive if I can get the engine idle speed low enough to
stop charging.

I bet I opened another question. If so, I'm here.

Matt
--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit

 

[mark sawyer]

Peer,

I don't have an answer for you, but wanted to add that alternator output varies quite a bit with RPM and temperature as well. I was looking at one
day possibly upgrading the alternator in my GMC, and I came across this company that I believe has an alternator that fits our application, assuming a
pulley change.

Yes, these are quite pricey compared to a standard replacement... That's the main reason I balked at upgrading... Also I believe I would need to
upgrade some wiring on my coach to handle the added current, as well as a higher capacity isolator...

ANyway, if you scroll down on this link, there is an output chart for various RPM vs the output amperage of the alternator. They push on their
website that "Standard" alternators tend to perform lower so far as output/rpm than the charts of their alternators, FWTW. That's independent of the
overall higher capacity of these alts.

https://www.dcpowerinc.com/fit/Chevrolet~Blazer~1980~5.0L-V8/7127-3-1v-180-hp.html

NOTE: the RPM on the chart is ALTERNATOR RPM not engine RPM. Website says that alternator RPM generally runs 3 to 3.5 times engine RPM, based on the
size pulley(s)...
--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX

 

[john r. lebetski]

Like Matt said, but think of it in terms of voltage instead of Amperes. As long as the alternator can maintain the Voltage it is asked to, and not
sag, the system is working. 80A , 100A, 200A alternator no difference in charge time. Keep in mind the voltage regulator is thermal compensating. At
Zero F it may put out 14.4V and at 100F 13.2V as it trys to compensate for the Voltage needed by the battery to be fully charged/not overcharged. This
is to try to track the rate of the chemical reaction in the cells which slows with temp drop. One thing that is the biggest power demand on new
vehicles that was not listed was electric fans. Start up demand to overcome inerta is many times higher yet. So much so that many vehicles start them
with a sequencer so they both don't draw at the same time. Another good reason to keep our engine driven clutch fans which will move more air than
any 12V electric. Vehicles like Prevost use 24V for high demand electrical circuits like condenser fans and interior blowers to keep wire gauge and
voltage drop manageable.
--
John Lebetski
Woodstock, IL
77 Eleganza II
Source America First

 

[peer oliver schmidt]

Matt,

thank you.

Your explanation did provide the information I was after, including the
warning of not just blindly going with a larger alternator.

And thanks to the others as well. A note to John L: I plan on getting
LiFePO4 house batteries, which, afaik, accept much higher amperage for
charging.

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, VA

 

[Ken B]

Jim Hupy pretty much hit on your answer in his first posting.

The size of the alternator required for your application is determined by the load you plan to put on it. If the load is 40 amps then the alternator
will put out 40 amps even though it is rated for 100 or 200.

So what is the load?
Ignition (a couple of amps,
Lights if on turned on (12 or 14 amps),
Heater fan if turned on (up to 20 amps),
and battery recharging.
You can add a few amps for radio and misc items that you might be powering.

On most systems the engine battery will recharge in 10 or 15 minutes at a low charge rate if all it was used for was starting.

That leaves the house battery. The rate of recharge will be determined by its current state of discharge and temperature. The rate may start off
high but it will very rapidly reduce it's load. I suggest that for most of it's recharging time the rate will be between 20 and 3 amps.

As a side note, there is a 50 amp CB in the GMC rear mounted battery line. So the recharge rate can never hit 50 amps or it would be shut down by the
CB.

So if you add all of the above items together you will be well below the alternator's 80, 100, or 200 amp generating capacity.

Note that higher alternator charging capacity is only available at higher engine / alternator speeds like cruising down the highway.

In a coach with lead Acid batteries you should not plan to run the house battery down below %40 or %50 for battery longevity purposes. So when
looking at Gene's battery charging graph you need to look at the chart STARTING at the %40 or %50 point.

My conclusion is that going from 80 to 100 amp alternator is no problem if you are already replacing the alternator. It costs the same and it gives
you a little more capacity at slower speeds. Going to anything higher than that is a waste of money and time unless you are adding some huge load to
the standard GMC electrical system.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Gene Fisher]

Yeah
Go ken go

> Jim Hupy pretty much hit on your answer in his first posting.
>
> The size of the alternator required for your application is determined by
> the load you plan to put on it. If the load is 40 amps then the alternator
> will put out 40 amps even though it is rated for 100 or 200.
>
> So what is the load?
> Ignition (a couple of amps,
> Lights if on turned on (12 or 14 amps),
> Heater fan if turned on (up to 20 amps),
> and battery recharging.
> You can add a few amps for radio and misc items that you might be powering.
>
> On most systems the engine battery will recharge in 10 or 15 minutes at a
> low charge rate if all it was used for was starting.
>
> That leaves the house battery. The rate of recharge will be determined by
> its current state of discharge and temperature. The rate may start off
> high but it will very rapidly reduce it's load. I suggest that for most
> of it's recharging time the rate will be between 20 and 3 amps.
>
> As a side note, there is a 50 amp CB in the GMC rear mounted battery
> line. So the recharge rate can never hit 50 amps or it would be shut down
> by the
> CB.
>
> So if you add all of the above items together you will be well below the
> alternator's 80, 100, or 200 amp generating capacity.
>
> Note that higher alternator charging capacity is only available at higher
> engine / alternator speeds like cruising down the highway.
>
> In a coach with lead Acid batteries you should not plan to run the house
> battery down below %40 or %50 for battery longevity purposes. So when
> looking at Gene's battery charging graph you need to look at the chart
> STARTING at the %40 or %50 point.
>
> My conclusion is that going from 80 to 100 amp alternator is no problem if
> you are already replacing the alternator. It costs the same and it gives
> you a little more capacity at slower speeds. Going to anything higher
> than that is a waste of money and time unless you are adding some huge load
> to
> the standard GMC electrical system.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[Daniel]

Hello Peer,

As you probably know in the newest MH with the Euro 5 and especially with the Euro 6 engines, the alternator often only works when the engine is
running at its lowest fuelconsumptionrates !!
Meaning that running a Mercedes Hymer ML-T for two hours did acually drain the house batteries!!
By then the engine did find the by a relais coupled house and starterbatteries, as _one_ battery, alternator only working at minimal, to preserve
perhaps 0,05 gallon of fuel an hour .... Leaving the MH after that ride with less battery capacity then in the beginning.

Many customers did not notice it in the beginning, or got shorepower and reloaded the batteries that way.
But also people with more "boondocking ambitions" got in to trouble.
The dealers didden't understand it in the beginning, since in the earlier days, driving ment charging, more or less, and even if the last 20% charge
lastet quit long ....

Some more technical educated, customers, understood the problem they were facing and forced the alternator to jump in with really some extra amps, by
turning their headlights on as an extra load. But that was not the best or elegant sollution.

That problem forced the MH outfitters to add a B2B powerboosters, so this way they could overcome the problem.
Using gel or lead-acid batteries with their big internal resistance makes those electronic devices valuable.
I did get only 18 amps at start in my two housebatteries which very quick dropped to 10 .... 8 .... 5 amps.
(I use the Victrom BMS, to monitor things ....)
Now I am in the process of changing the charge cables from 6 mm diameter to 16 mm diameter, and adding a Votronic VCC 1212-45 Chargebooster.

I your situation, if you change the battery to LiFeYPO4 you only need the big cables and they will suck up the electricalenergy all the way till they
are full, since their internal resistance is extremly low.

For you reference, since your german is your native language, see the german "Wohnmobilforum" were they have their own goeroes
And a subsection about this new battery technology.

Bye, Daniel

--
Daniel Jacobs, No GMC, but an admirer of them .... We'll see what the future brings ....

Always remember, the world is full of nice people!
So, if you can't find one, be one!

 

[johnny]

Ammeters (one per battery) are Your Friend. Although if you have a 26' outfitted by GMC with teh house bank in back, you have to either put the house
ammeter back there or use a shunt meter. They are, however, the only way to really see what the electrical system is doing with the batteries.

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon

 

[emerystora]

Not the only way. I have a Statpower Trucharge charger with a remote panel that tells the battery condition and charging level when it is plugged in.

Emery Stora
77 Kingsley
Frederick, CO

>
> Ammeters (one per battery) are Your Friend. Although if you have a 26' outfitted by GMC with teh house bank in back, you have to either put the house
> ammeter back there or use a shunt meter. They are, however, the only way to really see what the electrical system is doing with the batteries.
>
> --johnny
> --
> '76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
>
> "Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[johnny]

No, it infers condition based on voltage and rate of change. It also - at least most of them do - plays with the voltage applied from time to time
to preclude sulfating and overcharging. I got one of those too - dunno the make at the moment -and the coach stays plugged in when it's home so I
know the batteries are hot when I leave. It does not, however, tell me anything about them when I've got the engine running, or when I'm ensconced at
Chez WalMart or some other powerless venue.
My 23' has a solar charger and controller for the house battery which also works quite well. On startup, the ammeter shows little or no charge to the
house battery unless I've been staying without hookup. The chassis battery will - assuming everything is working properly- show a high rate of charge
for a few minutes, then taper off to little or nothing as the battery recovers from the cranking drain.

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon

 

[peer oliver schmidt]

Johnny,

thanks for the hint of trying it out myself

This is for my European 23' GMC that I plan to acquire in Spring 2017.

From all the information I have gathered so far, it seems that the
amperage used by the GMC for regular stuff is way less than it is for
more current coaches, and that I will have sufficient left-over for
starters. After all, I'll need about 40Ah each morning to get SWMBO and
my drink fixed, and we mostly drive more than long enough to fill-up
that bit of juice.

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, VA

 

[Gene Fisher]

OEM has been good for 40 years

On Wed, Nov 16, 2016 at 9:44 AM Peer Oliver Schmidt GMC <

> Johnny,
>
> thanks for the hint of trying it out myself
>
> This is for my European 23' GMC that I plan to acquire in Spring 2017.
>
> From all the information I have gathered so far, it seems that the
> amperage used by the GMC for regular stuff is way less than it is for
> more current coaches, and that I will have sufficient left-over for
> starters. After all, I'll need about 40Ah each morning to get SWMBO and
> my drink fixed, and we mostly drive more than long enough to fill-up
> that bit of juice.
>
> --
> Best regards
>
> Peer Oliver Schmidt
> PGP Key ID: 0x83E1C2EA
>
> '76a Eleganza II, VA
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[peer oliver schmidt]

gene,
> OEM has been good for 40 years

And I like to add a few more years to those 40

--
Best regards

Peer Oliver Schmidt
PGP Key ID: 0x83E1C2EA

'76a Eleganza II, VA

 

[johnny]

Chassis side is strictly 70s automotive. 5 - 6 Amps for the HEI, p'raps a bit more for points, an amp or two for gauges. Head, tail, and clearance,
maybe 30 - 35 total. My 23' is all LED house lighting except the porch light, turn it all on and it draws like nothing. The water pump is a current
hog but only runs when a faucet is running. An AC inverter will kill the batteries fairly quickly if it produces much AC power... but what do you
need AC for anyway? Microwave? Run the genset for it and hot water each morning is what I do if I'm WalMarting. For dry camping, ask some of the
guys here who do a lot of it - Colie et al.

--johnny

--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon