alternator amps and amp hours

[gerrym51]

I have a question that i have never really understood.

If an engine alternator system is say putting out 300 amps.

is it putting out 300 amps per second? Per hour ? or what.


this is regardless whether a battery can actually accept this much.

i will ask additional questions based on the answer to this one

[markopolo]

300 amps would be available for use right then & there.

If it could sustain that output for 1 full hour then 300 amp hours would have been the output.

[gerrym51]

Originally Posted by markopolo

300 amps would be available for use right then & there.

If it could sustain that output for 1 full hour then 300 amp hours would have been the output.

so 1600 amp hours of lithium battery=theoretically would charge in 5 hours?

[markopolo]

Yes, approximately. There would be some loss to heat and inefficiencies.

[booster]

As Marco says, amps are a rate of charge and do not carry any time reference. Amps in a time frame give amp-hours, amp minutes, amp seconds, etc.

A 300 amp alternator is kind of misleading callout. It would probably be more like 300 amp "capable" as it will do anywhere from zero to 300 amps. The alternator doesn't determine how many amps it generates, whatever loads that are present do that. The alternator generates the voltage and then the loads determine how many amps they can accept at that voltage.

Also, in calculations, you need to factor in how much the alternator maximum output will drop when hot. It can be a lot, depending on the alternator design, so that 300 amp alternator might be only 200-250 amps when at full output for a little while. And even lithiums will taper a bit in how much they will take as they near full. Lead acids taper a lot and need extra hold time besides.

[gerrym51]

so in reality-engine generator charging times are'fluid'

[jdhebner]

amps are scientifically defined as 1 coulomb of charge per second.

[booster]

Originally Posted by gerrym51

so in reality-engine generator charging times are'fluid'

That's probably a good way to put it, although once you know the times for your system, I would assume they would be pretty consistent.

[Davydd]

Originally Posted by gerrym51

so 1600 amp hours of lithium battery=theoretically would charge in 5 hours?

I am not sure there is an alternator available that can charge at 300 amps. Nations sells a 270a alternator but output is a variable. Nations says about 200 amps at idle. I've observed about 240 amps at highway speed. The other variables are temperature of the alternator and wire size from the alternator to the battery. Also, our system uses a Balmar multi-stage voltage regulator that is temperature sensing. You'll never see a constant charging. A lithium ion battery should be able to take all the current you can give it. So sitting in the sun with my 420 watts of solar panels, shore power and engine idling I have observed over 300 amps charging.

This is what Balmar says about its alternators.

"Alternator output is dependent on a number of factors; battery condition and capacity, wire size, engine horsepower and engine rpm, battery temperature, and alternator temperature. Of those factors, alternator rotation speed and alternator temperature are the most important."

[booster]

This is a real monster.

https://www.dcpowerinc.com/fit/GMC~S...37-370-xp.html

[gerrym51]

Originally Posted by jdhebner

amps are scientifically defined as 1 coulomb of charge per second.

My head exploded on this comment-thank you very much-lol

[gerrym51]

Originally Posted by booster

This is a real monster.

https://www.dcpowerinc.com/fit/GMC~S...37-370-xp.html

is that a replacement for original-could it be used as a 2nd alternator?

[gerrym51]

Originally Posted by Davydd

I am not sure there is an alternator available that can charge at 300 amps. Nations sells a 270a alternator but output is a variable. Nations says about 200 amps at idle. I've observed about 240 amps at highway speed. The other variables are temperature of the alternator and wire size from the alternator to the battery. Also, our system uses a Balmar multi-stage voltage regulator that is temperature sensing. You'll never see a constant charging. A lithium ion battery should be able to take all the current you can give it. So sitting in the sun with my 420 watts of solar panels, shore power and engine idling I have observed over 300 amps charging.

This is what Balmar says about its alternators.

"Alternator output is dependent on a number of factors; battery condition and capacity, wire size, engine horsepower and engine rpm, battery temperature, and alternator temperature. Of those factors, alternator rotation speed and alternator temperature are the most important."

solar panels/shore power.and engine all at once? my head exploded-again-lol

[Davydd]

Originally Posted by gerrym51

solar panels/shore power.and engine all at once? my head exploded-again-lol

Yep. I wanted to see what it would top out at. I probably didn't get much solar when I did it last April in my woods. I am fully charged right now and plugged in so there is only float going on. When my batteries are discharged some and I plug in I only see about 110 amps max charging rate. That's pretty rare because being out on the road for 148 days this year I only plugged in 19 times and the batteries are always fully charged when I initially do so. I just ran some experiments while I was at home in April.

Which brings up another thought and question. Avanti has the same alternator as I have and was getting higher amps at idle. I wonder if both his alternators are contributing current to his house batteries and my engine chassis alternator is not.

[gerrym51]

Originally Posted by Davydd

Yep. I wanted to see what it would top out at. I probably didn't get much solar when I did it last April in my woods. I am fully charged right now and plugged in so there is only float going on. When my batteries are discharged some and I plug in I only see about 110 amps max charging rate. That's pretty rare because being out on the road for 148 days this year I only plugged in 19 times and the batteries are always fully charged when I initially do so. I just ran some experiments while I was at home in April.

Which brings up another thought and question. Avanti has the same alternator as I have and was getting higher amps at idle. I wonder if both his alternators are contributing current to his house batteries and my engine chassis alternator is not.

seems you'd have to ask ARV that

[Davydd]

I'm pretty sure my engine alternator only charges the chassis battery and not my lithium ion battery bank. That kind of corroborates what Nations says it would do at idle. My second alternator has a 4/0 wire going directly from the alternator to the battery bank. That's a humongous nearly 1/2" diameter copper wire. Avanti's Great West Van originally charged the auxiliary batteries before he upgraded to a second alternator so I imagine the engine alternator might still be contributing charge unless he disabled it to do so. Since such wiring would have to be done by the RV converter from the engine alternator, ARV would have no reason or need to do so.

[booster]

Originally Posted by gerrym51

is that a replacement for original-could it be used as a 2nd alternator?

I don't know of any reason it couldn't be as a second alternator. If the pic is correct, it looks to be in the same case as the 270 amp unit that many are using.

[booster]

Originally Posted by Davydd

Yep. I wanted to see what it would top out at. I probably didn't get much solar when I did it last April in my woods. I am fully charged right now and plugged in so there is only float going on. When my batteries are discharged some and I plug in I only see about 110 amps max charging rate. That's pretty rare because being out on the road for 148 days this year I only plugged in 19 times and the batteries are always fully charged when I initially do so. I just ran some experiments while I was at home in April.

Which brings up another thought and question. Avanti has the same alternator as I have and was getting higher amps at idle. I wonder if both his alternators are contributing current to his house batteries and my engine chassis alternator is not.

He may have a different pulley on his kit than ARV used, so it spins faster, or the 4 cylinder could idle faster, or all the normal loads in the ARV are lowering what the batteries can have, or maybe Avanti's test hadn't settled all the way to base idle at the test point. All possibilities.

[Davydd]

I have the high-idle option and I don't think Avanti has that and I don't think a 4 cylinder idles as fast. As I mentioned, Nations says the 270a alternator should produce 200 amps at idle which is pretty much what I experience. I know what my loads are. Typically 10 amps is the average reading when just sitting and inverter and refrigerator are both on. So my battery net input would read about 190 on the screen and I would interpret 200 amp charging.

Anyway, this gets back to the original 300 amp charging discussion. Didn't know about the brute of an alternator but does anyone use it in a Class B?

[avanti]

Originally Posted by Davydd

Which brings up another thought and question. Avanti has the same alternator as I have and was getting higher amps at idle. I wonder if both his alternators are contributing current to his house batteries and my engine chassis alternator is not.

Where did I say I was getting higher amps than you at idle? I get around 200 amps. Maybe 207, but that is noise.

For the record:
--My OEM alternator is not connected to the house. I wanted it out of the equation. I disconnected the wire to the isolation relay. I left the relay only so my "boost" switch would still work.
--The wire from my Nation's alternator to the battery in the back is 3/0, which is plenty.
--I do not have high idle.