Alternator Size with LiFePo4

[rgleason]

Originally Posted by john61ct

Things are complicated enough, do not further complicate things unnecessarily, stick to KISS 12V unless you have an exceptional known-with-certainty **compelling** reason to go higher.

Reason: No continuous rating for Alternator Output by manufacturers, Reports of poor performance for high amp alternator installations, which take longer to charge that intended. Little definitive information about the environmental and installation factors contributing to these problems.

Goal: To avoid the problem altogether.

=====
Battery 12v - 230 ah x 0.5C = Alt 115amp continuous x 2.0 hours = 85% derating 115a/.85 = 135a Manuf. Alternator Capacity
Battery 12v - 230 ah x 0.7C = Alt 160amp continuous x 1.4 hours = 85% derating 160a/.85 = 188a Manuf. Alternator Capacity

Battery 24v - 115 ah x 0.5C = Alt 60amp continuous x 2.O hours = 85% derating 60a/.85 = 70a Manuf. Alternator Capacity
Battery 24v - 115 ah x 0.7C = Alt 80amp continuous x 1.4 hours = 85% derating 80a/.85 = 94a Manuf. Alternator Capacity

Since amps cause heat, not volts..
So, a 24v 100a Alternator would work and probably have a lot less heat.

Note there are other factors and design issues which need to be addressed, like HD bearings, High temp grease, etc.

Balmar only makes a Series 6 24vdc 70amp Alternator for our engine $1080
http://www.balmar.net/?product=alternator-60-24-70-j10
And the 24volt MC-624 regulator would be required too. $432
Serpentine Belt $450+/-

[rgleason]

Duckworks Magazine -A compilation of information and tips from Rick Young, Steve Dashew, George Walner, and Bob Gayle

This is an older article...

See "Battery Decisions - 12 or 24 Volts"

" I would suggest that there are other good, even better reasons for using a 24 vdc system on today's boats. These have more to do with the nature of the marine market itself, and the increasing use of electronic equipment on board."


Under "Alternators and Regulators"

"Truck alternators aren't designed to charge banks of deeply discharged batteries...designed to maintain against a load"
"Now... boat with a large battery bank and an intermittent charging regimen..full output..."
" Two small frame high output alternators (90-100A) will not be as reliable...or efficient as one 160A large frame alternator. .."


Under "Alternator Heat Management"
"The majority of the heat from an alternator comes from the rectifier diodes, which convert the alternator's AC power to DC. Most alternators draw air from back to front. Unfortunately, the air behind the alternator in most installations is typically beside the exhaust manifold of the engine - the hottest place in the engine compartment. Alternators with internal rectifiers can get so hot, you could fry an egg on them, and many can get hot enough to melt the epoxy insulation on the stator wiring when operated at fullfield current"


The next image is Dashews externally mounted rectifiers with fans outside the engine compartment. Further down they mention"...most amperage you can get reliably from a12vdc alternator is 160A, which makes the Leece-Neville 110-555 "triple nickels" one of the better off-the-shelf alternatives. ...The large frame Delco CS144 140A alternator ...has a good reputation also.


Another option..."Bob Gayle wrote a white paper4 about improving the efficiency of a typical truck alternator and thus its power output. He switched a Leece-Neville110-555 alternator to charge at 28.8vdc. The measured output for this alternator were 130A @ 14.2v (1.85 kW) at 3400 rpm. With the regulator fooled into using a 28.8 volt setpoint for output, the alternator produced the same 130A @ 28.8v (3.74kW) at 3400 rpm at full field current, almost doubling its power output.
Bob used an old 12v Balmar regulator monitoring voltage from the middle of the battery bank, so the regulator thought the alternator was generating 14.4v; instead of the actual 28.8 volts being delivered...'


Under "Selecting the pulley ratio"
"...I would want to turn the alternator at 3400-4500 rpm alternator speed at 1800 engine rpm - a pulley ratio of 1.88:1 for 12v (2.5:1 for 24v). At 3000 rpm the alternator would be turning 5640 rpm (7500 rpm for 24v), still below its 8000 rpm limit."

[john61ct]

You are not solving actual problems by going that route, nor even reducing the uncertainty.

Sticking with known-good units will eliminate the uncertainty without all that added complexity.

Can you fit a large-frame alt?

If you get one rated for example 150A, and in hot conditions need to de-rate its output to 100A, is that actually a problem for you in practice?

I am happy as anyone speculating about implementing edge-case scenarios, but thinking back to your pretty simple conservative use case and the very practical limitations you were focused on overcoming, pretty conservatively,

it seems to me you're getting out there into Science Project tech for tech sake's territory.

[john61ct]

wrt to HP

2HP per 1000W actually produced is a common guideline seen.

There are many packaged DC gensets (engine+alternator) that size the engine quite a bit higher though.

My fantasy 15kW unit based on a military 28V alt I figure would need 30+HP.

[newhaul]

Originally Posted by john61ct

wrt to HP

2HP per 1000W actually produced is a common guideline seen.

There are many packaged DC gensets (engine+alternator) that size the engine quite a bit higher though.

My fantasy 15kW unit based on a military 28V alt I figure would need 30+HP.

So wiring an alternator to produce 120 volts dc at 20amps would take about 3 hp
And then steped down to 12 volts externally would produce just under 200 amps.
Seems reasonable to me.

[rgleason]

http://www.delcoremy.com/Alternators...y-Model-Family



Delco 28si (200a) 12v, 24v also available
Has a higher temp rating
Temperature Rating 125°C / 257°F

Also
Delco 24si (160a) 12v, 24v also available.
12V 8600310 160
24V 8600388 70
Temperature Rating 105°C / 221°F

J80 Hinge, Short hinge version
Shaft OD (Pulley): 0.875in / 22.22mm

I found reference to the Leece-Neville-110-555JHO being a replacement and some notes show the LN has the following dimensions.
- total shaft length is 2.05"
- 1.02" for the pulley and 1.03" of thread for the nut

Would the Delco be similar????
If so,
Total Width= 9.27"
Width back of stud to beginning of pulley = 5.22"
The width of the case is critical. Balmar Series 6 has a case length of 5.08" so with 5.22" it gets even closer to the heat exchanger.
But it is close enough to continue measuring.

For my Yanmar the saddle is 3.15" so this is too wide by 0.83"


The saddle bolt to tightening bolt dimension is 7.22"
Which is greater than my Yanmar (6.5") by 0.72", I believe

This is all based on assumptions which are not actual measurements.


Who knows these dimensions for the pulley shaft and threaded part of the shaft lengths?

[rgleason]

Originally Posted by newhaul

So wiring an alternator to produce 120 volts dc at 20amps would take about 3 hp
And then steped down to 12 volts externally would produce just under 200 amps.
Seems reasonable to me.

Well, maybe John's figure is a little low, because Balmar has this here
150a = 5.2hp for example.

Which is a reasonably significant portion of my engine's 30hp, but Stu's "Small Engine" mode switch which jumpers the Balmar 614 regulator alternator temp sensor to drop the field to 50% power might be an reasonable answer to loading on the engine while powering against current and wind.


John, perhaps Newhaul and I are a bit "out there" at times, but I am still learning...it always helps to have someone bring it back to practical. I'd be interested in your response to Newhaul's 120v Alternator idea. Bob Gayle's link about converting an LN to 28v talks about much higher voltages too (48v), and there are some posts in his forum on this that discuss even higher voltages without much change needed to the rotor.

[john61ct]

My response is as above.

I would love to see someone with the right skillset do all this in the back shed and document it all.

But I think you should keep such SPs separate from practical discussions of production-level issues.

Narrowing in, eliminating choices is moving forward IMO this feels like blue-sky brainstorming.

[rgleason]

Delco 24si and 28si appear to be bigger than the Balmar Series 6 which fit.

• Saddle bolt to tighten bolt= 198mm = 7.8" (Balmar Series 6= 6.5") 1.3" greater
• Back thread to shaft thread tip = 234.1mm = 9.21" (Balmar Series 6= 5.08") 5.08"+ 2.05"=7.13" 2.08" greater

The 28si 160a appears to have better low rpm performance than the 180a or 200a from the curves.
12vdc 160a=
at 1300rpm=40a
at 1500rpm=80a (750 eng rpm)
at 2000rpm (1000eng rpm)=160a
the 180a and 200a do not.
The 28si is rated for Higher temperatures 257degF

The 24si 160a from the curve
From Curve
at 1500rpm = 40a
at 2000rpm = 100a

The 24v versions may not produce current as early as when idling the engine at 800 rpm.


These may only fit when the diodes are made remote.

[deluxe68]

Originally Posted by Maine Sail

Ditto to what Bruce said...

If you want high output & a long bulk duration, from a small frame alternator, external rectification is going to be the best solution.

Wish I had done that and bought a Mark Grasser alternator. My Balmar 165 has the onboard diodes covered with a plastic cap on the back. Not sure who thought that was a good idea since it retains heat and restricts airflow. When I get on the boat in the spring I am going to run the exhaust duct up to the alternator.

[rgleason]

Deluxe68 thankyou for posting. Can you describe your installation to me engine, airflow, battery bank capacity, max continuous voltage achieved when in bulk?

[rgleason]

Deluxe68 also, which Series of Balmar is the 165a?

[rgleason]

Delco Power Curves 22si, 24si, 28si

[deluxe68]

Originally Posted by rgleason

Deluxe68 thankyou for posting. Can you describe your installation to me engine, airflow, battery bank capacity, max continuous voltage achieved when in bulk?

Balmar AT-165, Yanmar 4JH2E, 400AH, no idea on airflow or max voltage.If you search the internet you will find lots of people unsatisfied with Balmar small case alternators. Mine overheats when putting out over 125 Amps, engine speed does not make a difference.

[rgleason]

Since the heat and efficiency of the Diodes is the problem, I would like to know if there is a more efficient way of rectifying. I assume all these alternators are using full rectification and not half with a center tap.

This may be old news but a search found a Mosfet solutiion that might be useful, from 2008.

A novel high efficient approach to input bridges - Infineon Technologies
https://www.infineon.com/dgdl/tp-080...53573fb97c3e9f

All these equipments have one or more input diode-bridges to convert the 50- 60Hz (400Hz in aircrafts) sinusoidal waveform, at different AC voltage depending ..

A novel high efficient approach to input bridges
Davide Giacomini, member IEEE, Luigi Chiné
SMPS European Application Lab
International Rectifier


What, if anything is being done to improve the efficiency of Full Rectification using Diodes? The solutions to deal with the heat and inefficiency are extraordinary.