Auto alt vs. conventional gen head + batt chgr

[cujet]

I have a small 3HP Chinese diesel and a 3HP Briggs. I could use either one. I would like it to drive an alternator or generator head for battery charging. My original thought was to use a Ford alternator and belt drive it (I have an alternator from my 98 F150). Manually changing the RPM as the load might require.

However, would it be better, more efficient and/or more useful to simply use a conventional direct drive generator head?(I have a small one) And, simply plug in a conventional battery charger. It would probably have to run at 3600 RPM all the time, and that might not be the best thing, for a number of reasons.

[mobile_bob]

what voltage battery bank do you wish to charge?

if you wish to do 24 volts, i defy anyone to exceed the efficiency of the system outlined in my white paper report on "high efficiency and high output alternators"

you just won't even come close with a 120volt genhead driving a charger, even if it is a high efficiency, pf corrected expensive unit

while i haven't tested at 12 volts nominal, i suspect that the system would still outperform the 120vac and charger scheme.

forget the ford, gm, chrysler et. al, alternators and step up to a prestolite/leece neville 110-555jho large frame alternator if you decide to go
that route, its just so much more robust, easier to work on, reasonable price and widely available, and is the easiest of the bunch to control
with a 3 step regulator that you will invariably end up using anyway sooner than later.

the efficiency as outlined in the white paper is ~80% for the 555 alternator as used and controlled, that is right at where the st head is at making
AC power and better than the product of the st efficiency and a high efficiency charger.  with a balmar or similar you can tailor the output to match your engine's available power and get true 3 step temp compensated charging.

fwiw
bob g

[Tom Reed]

I've got a 5 hp OHV Tecumseh with a 5" pulley belted to a 63 amp Delco 10si with a 4" pulley. To start charging the plug to the voltage regulator is plugged in. I've got to really rev that engine up to keep it from stalling when it starts charging.

[BioHazard]

I asked a similar question a little while ago, I wanted to use a nice charger with my little 2hp generator. What everybody tells me, is that unless you have a really big generator, the charger will output very little power - not what it is rated for. I don't fully understand why but I'm sure somebody can explain...

[BioHazard]

Here's the question I posted:
http://www.microcogen.info/index.php?topic=1782.0

[cujet]

Well, my initial thought was 12V. However, I do get my hands on 24V aircraft batteries regularly. So, I could simply go with a 24V setup.

While it would be fantastic to be efficient, I'm not sure that matters much here. But rather that I simply have the capacity to do it on cloudy days.

[rbodell]

I run an automotive alternator to charge batteries. The first thing I noticed is that if you run a regulator, after a short time, it drips back to 2 or 3 amps. I switched to a rheostat to operate the alternator at the amperage I want it to put out. With this setup it will stay at whatever amperage I set it at cutting the charging time by many hours. I have 6 - 6 volt deep cycle batteries wired up for 12 volts. I charge it continuously 6 hours a day at 30 amps. The batteries do not even get the slightest increase in temperature at 30 amps. Remember the 30 amps is distributed between all 6 batteries. This would be too much if there was only one or two batteries. I don't have a problem with the batteries running low on water either.

[Lloyd]

I run an automotive alternator to charge batteries. The first thing I noticed is that if you run a regulator, after a short time, it drips back to 2 or 3 amps. I switched to a rheostat to operate the alternator at the amperage I want it to put out. With this setup it will stay at whatever amperage I set it at cutting the charging time by many hours. I have 6 - 6 volt deep cycle batteries wired up for 12 volts. I charge it continuously 6 hours a day at 30 amps. The batteries do not even get the slightest increase in temperature at 30 amps. Remember the 30 amps is distributed between all 6 batteries. This would be too much if there was only one or two batteries. I don't have a problem with the batteries running low on water either.

R-B-Dell,

Good to see ya back.

You're right, you're wrong.... You're so F...k...g Right, You're so F...k...g Wrong.

One solution doesn't fit all...yea bats are bats but, Really bat banks aren't the same, and neither are charge source, and regime.

An under/over sized charge source, can and will affect the outcome of the health of the bat bank.

I'm just saying you can't apply a one size fits all.

A FLA can take just about all the current that you can throw at it, under most situations.... As long as it is voltage/current/temp limited.

The real design limits come when you have either a low/high source charge relative to the size of the bank.

I repeat there is no one size fits all.

Each bank depends on a proper sized charge source to replace the power extracted, to the power-replaced ratio.


This whole rant is dependent on whether you want to get the longest life out of the bat bank.

Lloyd 

[Mad_Labs]

An alt based genny will beat the tar out of a 120VAC to 12/24VDC genny/charger setup. I have both setups, and the lawnmower/alt uses a fraction of the fuel, say 1/2 to 1/3 less. My AC generator is much larger than the charger (5000W vs 1200W) so you could do better with a smaller genny.

Jonathan

[squarebob]

Here is my little 3.5 HP AA1 diesel turning a 24V alt. Works like a charm.

[bschwartz]

It looks like a 2 to 1 ratio on the pulley size.  If that is a 3600 RPM engine, that would turn the alternator at 1800 RPM.  Isn't that a little slow for a car alternator?

[squarebob]

Everyone talks about stalling out their engines with too much load. The ratio works out to be .575. The engine puts out 1 HP per 1000 RPM. I slowed down the Alt. RPM based on the performance curve I have for the unit  (see attachment). The engine is variable speed so I can run the alternator RPM from about 500 (and 0 output) up to about 2000 RPM. Now the fastest I can get the engine to run with a battery bank that needs a lot of charge is about 3000 RPM and 1725 RPM on the Alt. It puts out about 35 Amps and gray smoke from the exhaust. As the bank charges up and the Amps drop, I can slow the engine down to match the needed output and save fuel. I built this as a charger to take my bank from about 80% to 100% and as a backup to my GM90 setup.

Bob

[veggie]

I run an automotive alternator to charge batteries. The first thing I noticed is that if you run a regulator, after a short time, it drips back to 2 or 3 amps. I switched to a rheostat to operate the alternator at the amperage I want it to put out. With this setup it will stay at whatever amperage I set it at cutting the charging time by many hours. I have 6 - 6 volt deep cycle batteries wired up for 12 volts. I charge it continuously 6 hours a day at 30 amps. The batteries do not even get the slightest increase in temperature at 30 amps. Remember the 30 amps is distributed between all 6 batteries. This would be too much if there was only one or two batteries. I don't have a problem with the batteries running low on water either.

R-B-Dell,

Good to see ya back.

You're right, you're wrong.... You're so F...k...g Right, You're so F...k...g Wrong.

One solution doesn't fit all...yea bats are bats but, Really bat banks aren't the same, and neither are charge source, and regime.

An under/over sized charge source, can and will affect the outcome of the health of the bat bank.

I'm just saying you can't apply a one size fits all.

A FLA can take just about all the current that you can throw at it, under most situations.... As long as it is voltage/current/temp limited.

The real design limits come when you have either a low/high source charge relative to the size of the bank.

I repeat there is no one size fits all.

Each bank depends on a proper sized charge source to replace the power extracted, to the power-replaced ratio.


This whole rant is dependent on whether you want to get the longest life out of the bat bank.

Lloyd  

Rbodell has stated many times on the forum(s) that his system was built this way "because it works for him" and has not claimed that his methods will work across the board. I am thankful that Bob has shared his info and experiences and hope many others will do the same. By sharing what we do, it does not necessarily mean that we are stating that it will work out the same for all applications.

veggie

[BigGreen]

Hey Bob
Nice to see you drop in. It's been a while 

[rbodell]

Hey Bob
Nice to see you drop in. It's been a while 

Thanks a lot, I got tired of being retired and somebody asked me to give them a hand for a few days. It has been almost a year and I figure I don't owe then anything LOL. Actualy I had a close call the other day. I fell about 8 feet on to some sharp pointed pieces of steel on a garbage truck compactor blade I was welding on. https://picasaweb.google.com/111457583175221109892/November302011#5680913284046383650 It really hurt at the time, but I never got any more than a slight scratch. The ems thought I was impaled on those pieces of steel but no. I have a bad back and didn't even get a back ache. For some reason the fellow upstairs seems to have a reason to keep me around. It did make me think that there must be something better than working so I retired again. Now I have more time.