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Old 20-10-2018, 13:07   #1
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Alternator Size with LiFePo4

Engine:Yanmar 3ym30
House: 250 to 300 ah Lifepo4
Acceptance: 0.4C to 1C = 100- 300 amps

I had earlier decided to get Balmar Series 6 60-120amps for FLA batteries, and I had determined I could charge on the hook in reverse at 40-50 amps 850 eng rpm and 80amps at 1000 engine amps when the alt is hot using belt manager and temp sensors, with a new serpentine belt.

I am considering a 150 amp series 6 balmar if it will continuously charge LiFePo at a higher rate say 110-125 amps for 2.5 hours at higher rpms, also on belt manager without overheating and dropping to 80 amps or 100amps.

I have a 3" dia fresh air duct with bilge fan to help control heat.

What are user experiences about this?
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Old 22-10-2018, 07:55   #2
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Re: Alternator Size with LiFePo4

You might look at the Mark Grasser series of alternators using his remote rectifiers, which moves much of the heat off the alternators. This allows continuous output when charging lithium at nearly the cold-rated output rating.

For instance see attached for the J180 saddle mount shortened compact large case (can usually fit right into the stock position, however with an upgraded pulley kit). Note the output with the R.R. is nearly the max cold output.
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Old 22-10-2018, 08:31   #3
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Re: Alternator Size with LiFePo4

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.


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Old 22-10-2018, 08:49   #4
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Re: Alternator Size with LiFePo4

An issue that I suspicion, but do not have any idea how much itís true, is that the difference in say a 150 amp alternator and a 200 amp alternator is nowhere near 50 amps when you look at continuous output.
I again suspicion that as both have about the same mass, and the same cooling fans, and surface area to radiate heat, that the difference in continuous output is going to be less than the rated output difference.

It would be nice if a continuous output could be stated by the manufacturers , but as there is no standard for at want ambient temp and what alternator RPM, I guess thatís a bridge too far.
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Old 22-10-2018, 10:34   #5
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Re: Alternator Size with LiFePo4

Quote:
Originally Posted by a64pilot View Post
It would be nice if a continuous output could be stated by the manufacturers , but as there is no standard for at want ambient temp and what alternator RPM, I guess thatís a bridge too far.
There is a standard In generators it is NEMA MG1 and IEC 60034, but the same codes are used in automotive and bus systems with minor changes. Both standards use the same letter systems for insulation class and both describe duty cycles and maximum allowed temperature rise.

Alternators are rated at 40C ambient temperature (assumes engine rooms are somewhat warm). The four classes of insulation are:

A = 60C rise (so 100C maximum continuous operating temperature)
B = 80C rise
F = 105C rise
H = 125C rise

under NEMA MG1 standby units are allowed to run at 25C above those numbers, in the auto industry 30C is used for non-continuous use.

If you dig in the specs far enough you can usually find the insulation class, for the purposes discussed here you definitely want an F or H class alternator.

You may also see a notation something like H/H or H/B, this is the insulation class/expected operating temperature. Something like H/B means the alternator has 125C rise insulation but the manufacturer has provided enough cooling flow that it expects the unit to operate at full power with only an 80C rise. H/H, on the other hand, means you should expect the full 125C rise (which leads to faster breakdown of the insulation).

The next step is the duty cycle, this is denoted by S# where '#' is a number from 1 to 10. S1 is continuous duty full power output, all the others are some form or other of less than continuous duty.

Every heavy duty bus/ambulance service alternator I've looked at provides insulation class information in the specs, small-case/automotive units it can be harder to find.
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Old 22-10-2018, 15:14   #6
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Re: Alternator Size with LiFePo4

Quote:
Originally Posted by OceanPlanet View Post
You might look at the Mark Grasser series of alternators using his remote rectifiers, which moves much of the heat off the alternators. This allows continuous output when charging lithium at nearly the cold-rated output rating.

For instance see attached for the J180 saddle mount shortened compact large case (can usually fit right into the stock position, however with an upgraded pulley kit). Note the output with the R.R. is nearly the max cold output.
So assuming
750 eng rpm, belt ratio 2.2, alt rpm 1650, alt output 50-70a continuous
1000 eng rpm, belt ratio 2.2, alt rpm 2200, alt output 160a continuous
2000 eng rpm, belt ratio 2.2, alt rpm 4400, alt output 225a continuous

That would be great, the upper end would be more than 1C but it could be capped somehow. Charging would not take 3 hours anymore, but more like 1.5 hours.


I am just trying to envision where I'd put the rectifiers. How far away from the alternator are the cables normally?
Would the J180 fit a Yanmar 3YM30 in the normal position?
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Old 22-10-2018, 15:35   #7
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Re: Alternator Size with LiFePo4

Quote:
Originally Posted by rgleason View Post
So assuming
750 eng rpm, belt ratio 2.2, alt rpm 1650, alt output 50-70a continuous
1000 eng rpm, belt ratio 2.2, alt rpm 2200, alt output 160a continuous
2000 eng rpm, belt ratio 2.2, alt rpm 4400, alt output 225a continuous

That would be great, the upper end would be more than 1C but it could be capped somehow. Charging would not take 3 hours anymore, but more like 1.5 hours.


I am just trying to envision where I'd put the rectifiers. How far away from the alternator are the cables normally?
Would the J180 fit a Yanmar 3YM30 in the normal position?
Mark usually tries to get a higher ratio than 2.2. He does have a kit for his J180/250A on the 3YM30 with a 2.5 ratio. More info here:
https://www.bruceschwab.com/wp-conte...rice-Specs.pdf
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Old 22-10-2018, 15:55   #8
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Re: Alternator Size with LiFePo4

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Old 22-10-2018, 17:17   #9
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Re: Alternator Size with LiFePo4

Quote:
Originally Posted by OceanPlanet View Post
Mark usually tries to get a higher ratio than 2.2. He does have a kit for his J180/250A on the 3YM30 with a 2.5 ratio. More info here:

https://www.bruceschwab.com/wp-conte...rice-Specs.pdf


No Marine installation that I have seen comes even close to the optimum RPM for the average alternator, which is often above 10,000 RPM, but of course varies from one alternator design to another.
I already had my Balmar serpentine belt kit before I learned that Mark has kits that significantly increase the alternator RPM.
If I had known that, I would have bought one of his kits.
A faster turning alternator makes less heat, and due to the fan moving more air, is better cooled also.

Our alternators turn the RPM they due based on installation ease and available room.
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Old 22-10-2018, 17:37   #10
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Re: Alternator Size with LiFePo4

I am going to follow up on the Mark Grasser J180 alternator with external rectifiers, but thought I would advise regarding Balmar Tech Support thoughts about LiFePo4 in my situation.

His [Balmar Tech Support] comment was LiFePo4 is a an "alternator killer" as they have very low resistance and they load the alternator for long periods. Alternators can then easily run too hot and burn up.
  1. Always set the MC-614 Regulator Belt Load Manager to B-3 (15% Reduction to top output) when charging LiFePo4.
  2. Also install the Alternator Temperature Sensor to protect the device by cutting back automatically to 50% at high temperatures.
So the Series 6, 120a serpentine would output 102a with B-33 (15%)
and Series 6, 150a serpentine would output 127a with B-3 (15%)

He said the 120a would have better cooling, but to definitely get the 150a because it has more copper and would meet the LiFePo4 requirements better. He said all installations are different, but he thought we would l probably get 120-125a continuous.

He said the alternator will be operating at its maximum output (hot), most of the time, and one suggestion was to drill 1" holes in the belt cover for better air flow, opposite the alternator. Another suggestion was to run a bilge fan on one of the vents to help with heat (might help to get an additional 2a-5a).

He advised that LiFePo4 charging is not linear either, so there is more resistance as the bank gets fuller (but there it is significantly less than FLA).

Assuming the alternator max 125a is charging at 0.4C so the bank could be 312ah. Given an alternator continuous charge capacity of 125ah, it appears a bank of 250ah (2hrs + to full charge) would be appropriate for us.

Additionally, it can be noted on the new Balmar website pages that the new Regulators have a preset LiFePo4 program for charging, however the user can always program LiFePo4 settings.
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Old 22-10-2018, 18:31   #11
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Re: Alternator Size with LiFePo4

Mark Gasser
  • Alternator Large Frame- MGDC-Alt-J180-250A/large - $1299
  • Remote Rectifier - $600
  • Serpentine ratio 2.5 - 3YM30 Stage 2 Large Frame J-180 $1249
  • Total $3148
  • Output = 180 continuous, charge the bank in 1.5-2 hrs.
  • Alternator Small Frame - MGDC-Alt-160A/small $949
  • Serpentine ratio 2.5 - 3YM30 Stage 1 Premier $799
  • Total $1748
  • Output Adjustment B-3 (15%) = 136a continuous, charge the bank in 2.3 hrs, note ratio is 2.5, better cooling.
Balmar
  • Alternator - Balmar Alternator 60-150-J10 for 3YM30 $884
  • Serpentine ratio 2.2 - Yanmar Kit 48-YSP-3YM-B $646
  • Total $1540
  • Output Adjustment B-3 (15%) = 127a continuous, charge the bank in 2.5 hrs., note parts easily available.
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Old 23-10-2018, 10:37   #12
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Re: Alternator Size with LiFePo4

For a Perkins 4.236

SW Diesel

- Crank pulley K6 $178
- WP pulley K6 $188

- K6 serpentine belt (greenstripe) $25

Pasco Alternators

- Delco Remy 200 amp 28Si $400

Compass Marine

- 2.9" K6 pulley $62

Balmar

- Regulator - Existing $0

- Misc nuts bolts etc $15
- G10 epoxy board $4

Total $872

The 28Si has a different shaft diameter from your "typical" alternator. Sourcing a smaller diameter alt pulley can be a challenge in K6. You could get more power transfer with an 8 rib belt but you would lose the cost savings for the SW Diesel pulleys.

So by going the assemble it yourself way you end up with a 200 amp alternator and serpentine belt kit for under $900 including shipping.

I usually run the regulator so that the alternator outputs around 130 amps.
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Old 23-10-2018, 11:50   #13
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Re: Alternator Size with LiFePo4

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Originally Posted by evm1024 View Post
For a Perkins 4.236

SW Diesel

- Crank pulley K6 $178
- WP pulley K6 $188

- K6 serpentine belt (greenstripe) $25

Pasco Alternators

- Delco Remy 200 amp 28Si $400

Compass Marine

- 2.9" K6 pulley $62

Balmar

- Regulator - Existing $0

- Misc nuts bolts etc $15
- G10 epoxy board $4

Total $872

The 28Si has a different shaft diameter from your "typical" alternator. Sourcing a smaller diameter alt pulley can be a challenge in K6. You could get more power transfer with an 8 rib belt but you would lose the cost savings for the SW Diesel pulleys.

So by going the assemble it yourself way you end up with a 200 amp alternator and serpentine belt kit for under $900 including shipping.

I usually run the regulator so that the alternator outputs around 130 amps.
Correct the 28si Alternators haa a 7/8" (22.23mm) shaft.
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Old 23-10-2018, 12:03   #14
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Re: Alternator Size with LiFePo4

Note the main reason to go to a stock higher-amp alt, should not be to actually get all those rated amps, but

in order to run continuous output at a lower proportion of the max rating,

for reliability and longevity.

So pulling 110A from a 150A alt is better than to attempt pulling 100A from a 120A alt.

The electronics mounted remotely does let you increase that ratio, but to me the increase in reliability and longevity is the greater benefit.
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Old 23-10-2018, 13:32   #15
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Alternator Size with LiFePo4

Your not going to get 85% continuous output from a higher amp alternator, but you may get more than 85% continuous output from a lower rated one.
That is what is wrong with those calculations.

Secondly, you canít compare a small frame alt to the Mark Grasser J series alternator in continuous output, even with the diodes still installed, then remove the diodes and you get another leap forward.
The J even with the same rating, will make way more power continuously without overheating.

Maine Sail was selling the Mark Grasser J series alt at one heck of a price, I was tempted myself, but in truth not much of my charging comes from an alternator anyway, plus the difficult in fitting, and another project, did me in.

Just me, as I have mine set rather conservatively for a long life, but I run my Mark Grasser 165 at a belt manager setting of 4 and have the high temp limit at 90C and get it seems about maybe 90 amps continuous, and it runs at a steady 90C it seems.

If it were a 200 amp alt and I ran the same setting, Iíd bet maybe Iíd see 100 amps, an increase of 10 amps, but that is a SWAG, I know I wouldnít get another 35 amps.

Best answer I can get from those that have done the testing and know, is that the actual continuous power increase is not linear with the bigger rated small frame alternators, although I didnít get any kind of number.
Person I brought my 165 from recommended the 165 when I asked about a 200, I was basically told itís a lot more money, for not much more output, and they stood to profit from the sale of the bigger alt and talked me out of it.
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