Alternator Size with LiFePo4

[rgleason]

OceanSpray built a nice regulator that measures current with a shunt.

http://www.cruisersforum.com/forums/...ml#post2073195


I wonder if these boards are available?

[john61ct]

Yes I've always been **very** impressed by Eco-Tech.

Apparently very responsive management.

[rgleason]

Originally Posted by rgleason

OceanSpray built a nice regulator that measures current with a shunt.

http://www.cruisersforum.com/forums/...ml#post2073195


I wonder if these boards are available?

His website for the Regulator is here, he has a Generation 2 coming out.


SeaLITHIUM VRC-100 Advanced Alternator Controller | | Nordkyn Design


This website is packed with information, and one section has information about LFP

[rgleason]

Here is American Power's version of Al Thomaston's regulator


APS-500: Top 5 Q & A on our new regulator - American Power Systems, Inc.®

[rgleason]

While disassembling two 2004 Dell Inspiron XPS 15 laptops for the third time, to clean them and renew the thermal paste, I considered the heat removal system.

It is two heavy copper heat pipes with a sturdy multiple fin fan coil at the end. A 2.2" diameter x thin 3/8" fan then pulls fresh air through the laptop and forces it out through the fan coil. This system manages to keep about normal power use down to 52c-54c (125f-129f) in the computer.

See attached picture, the copper heat tubes and black fan coil are on the upper right. What would four or six of those secured with thermal heat paste to the outside of the alternator, with a big robust fan moving heat to outside do for the alternator output and longevity? Maybe it would not be too hard to make 3 larger purpose-built heat tubes with fan and fan coils.

Afterthought -Maybe the heat tubes should just go down into the bilge water or the water tank, with no fan needed, but what would happen with grounding and corrosion? Of course there is also a vibration issue with this...
Also because heat rises, the pipe won't work in this direction - heat on top and cold lower.

Design of a horizontal heat pipe for electronics, this provides a lot of very good information about designing heat pipes and could be applied to alternators, but we need to know how many watts should be removed.

https://www.electronics-cooling.com/...ng-heat-pipes/






Heat Pipe

video

More heat pipe

https://www.youtube.com/watch?v=R5bJU5QcDho

[rgleason]

https://celsiainc.com/


Has on line calculators and information about heat pipes, fins, vapor chambers etc.

[rgleason]

AAVID

https://www.digikey.com/en/supplier-...SAAEgIUV_D_BwE

Other posts referencing heat output and standards for alternators:
http://www.cruisersforum.com/forums/...ml#post2746626

Mainesail 255F is a good high number.
http://www.cruisersforum.com/forums/...ml#post2747354

Tanglewood
http://www.cruisersforum.com/forums/...ml#post2747759

...Heat builds up ..in two places,rectifier diodes, stator windings.

Temp sensors like the Balmar sense the rectifers, not the stator.
I instrumented the stator on a LN series 5000 "large frame" alternator, nameplate rating 190A @24V nominal. I regularly ran it at full output for hours at a time.

The diodes never came anywhere close to the 100C trigger point for the Balmar Regulator.

But the stator, on the other hand, would reach 150C (300F). I spoke with LN about it, and you would expect the max allowed temp would be a specified number for every alternator, but no. After two escalations to engineering, the answer was that that stator temp was normal and acceptable. So my conclusion was that for that particular alternator, the nameplate rating was also the continuous duty rating. But I would not make that leap of faith on smaller units.

Tanglewood
Another post with more info about the stator heat.
http://www.cruisersforum.com/forums/...ml#post2750202

The diodes generate heat proportional to the current. Heating is a fixed voltage drop, times the current.


But the bigger factor is heating in the stator windings since that grows as the square of the current. The windings are a fixed resistance with varying current, so heating is i^2 times R. So double the current and you quadruple the heating.


So there is benefit is remote mounting the diodes in getting that heat away from the rest of the alternator, and perhaps improving air flow at the same time. But you will still generator the same heat in the ER, though not concentrated in the alternator case.


So looking back at my earlier comments about running at a higher voltage, if you double the voltage, you halve the current for the same power output. That also cuts the diode heating in half, and reduces the stator heating by a factor of 4. Now it's much easier to keep the alternator cool.

[rgleason]

Tanglewood's most definitive statement on diode rectifier and stator heat loss.
http://www.cruisersforum.com/forums/...ml#post2750840

...stator heating losses. An example LN 185A alternator has a stator winding resistance of 0.020 ohms. Here's the heating at different loads:


50A: 50*50*.020 = 50W
100A: 100*100*.020 = 200W
150A: 150*150*.020 = 450W

185A: 185*185*.020 = 684W


And for comparison, here's the diode heating:


50A: 50 * 0.6 = 30W
100A: 100 * 0.6 = 60W
150A: 150 * 0.6 = 90W

185A: 185 * 0.6 = 111W

And here is the total heating power as compared to the output power @12V, and associated efficiency.

50A: 80W heat, 600W power, 88% efficient

100A: 260W heat, 1200W power, 82% efficient

150A: 540W heat, 1800W power, 77% efficient

185A: 795W heat, 2220W power, 74% efficient


You can see the rapid decline in efficiency as the current goes up

Note that these numbers just calculate the electric heating in the alternator. There are also losses in the rotor, and in mechanical drag, especially from the fans. Power to drive a fan increases as the cube of the speed. Typical alternator total efficiency is in the 50%-60% range.

So cooling technology has to deal with between 200w (100a) to 795w (185a). If the heat issue was properly dealt with, the alternator would not have to operate as close to its max capacity, making it more efficient.

I think about my 65a Balmar now outputting perhaps 100w of heat. What happens when I go up to a 185a alternator outputting 795w, which is a huge increase? My refrig will no longer work because it is next to the engine, the engine room temps will go way up if I don't deal with it right, and I've created another problem that has to be solved, so I best get this right to start with.


Just putting in an oversized alternator does not solve the full problem.


https://www.boydcorp.com/thermal/heat-exchangers.html


https://www.boydcorp.com/thermal/liq...ld-plates.html

[john61ct]

I don't have that much to say about HowTo assist cooling, other than relocating away from the alt seems to be the first step.

But I would be really sure it was necessary before going to a lot of trouble.

I seem to recall you were disappointed learning charging LFP at a high C-rate (over say 0.5C) was not recommended as a regular habit?

So are you sure you won't kill two birds with one stone just bringing the charge current rate down a bit when ambient temps go high?

[OceanPlanet]

Higher voltage better...24V highly recommended for high-energy systems. The new Integrel systems will be 48V (actually as high as 56+V)

For 12V systems it really helps to go with the external rectifiers

However one key issue we see a LOT, is that there is simply no ventilation near the alternator(s). Often there is a fan blowing air in or out of the engine compartment however without any thought as to how the air actually might get to the alternator. The air blowing in mostly just goes straight to the engine air intake and gets sucked up by the engine. If there is simply an intake vent near the alt to allow air to flow in and around it, as the air moves towards the engine intake and/or the exhaust fan/vent, it certainly helps. Otherwise, the alt is often simply sitting in the port fwd corner of the engine box, surrounded by it's own hot air essentially moving it around in a circle...

[newhaul]

Originally Posted by rgleason

Tanglewood's most definitive statement on diode rectifier and stator heat loss.
http://www.cruisersforum.com/forums/...ml#post2750840


So cooling technology has to deal with between 200w (100a) to 795w (185a). If the heat issue was properly dealt with, the alternator would not have to operate as close to its max capacity, making it more efficient.

I think about my 65a Balmar now outputting perhaps 100w of heat. What happens when I go up to a 185a alternator outputting 795w, which is a huge increase? My refrig will no longer work because it is next to the engine, the engine room temps will go way up if I don't deal with it right, and I've created another problem that has to be solved, so I best get this right to start with.


Just putting in an oversized alternator does not solve the full problem.


https://www.boydcorp.com/thermal/heat-exchangers.html

but you also forget the sq of time in that equation. Figuring at 75% efficiency . 75 amps puts out 50 amps and a 185 puts out 138 at 75% so that is a 2.78 times more charging power which reduces Lfp charging by about 60% time wise .
So for for 400ah bank at 20% will take about 6 hours with the 65 amp alternator and just unfolded 2 with the 185 amp one so the bigger alternator will actually generate less overall heat in the vessel ( when you add in the latent heat generated by the engine itself

[rgleason]

Thank you for the points OceanPlanet [Bruce] and John.
John: Re charging lifepo, I modified that to target .25C (normal) to .3C range (when needed)



I need to convert watts to btu to comprehend this better
1 watt = 3.14btu/hr so


50A: 80W heat, 600W power, 88% efficient, 251 btu/hr heat
100A: 260W heat, 1200W power, 82% efficient, 816 btu/hr heat
150A: 540W heat, 1800W power, 77% efficient, 1,695 btu/hr heat
185A: 795W heat, 2220W power, 74% efficient, 2,496 btu/hr heat


1 ton of cooling = 12000 btu/hr, so these loads are not that huge, the 50 amp heat load is comparable to sensible heat from a person sitting in a auditorium and the 100 amp heat load is about double the sensible heat from a person doing heavy work.



Note: The initial figures do not account for the engine heat required for the given amps.


I totally agree with what Bruce says about typical engines and alternators.

[rgleason]

Originally Posted by newhaul

but you also forget the sq of time in that equation ... so the bigger alternator will actually generate less overall heat in the vessel...

by virtue of the faster charge rate. Good point, glad to see there would be some reward for the changes and cost.

[rgleason]

Tanglewood's statement on diode rectifier and stator heat loss. Alternator Size with LiFePo4 links increased heat with increased amps.

Bruce from Oceanplanet says 24vdc systems are highly recommended for high energy systems.

Is one of the advantages of going from a 12vdc alternator to 24vdc, that you are not increasing the amperage produced, but increasing voltage instead? By doing this less heat will be produced by the stator and the diodes?

The other benefit comes from sizing wires or going longer runs.

Just for study, I found several 24vdc alternators. I think all the Balmar 6 Series can be run with their MC-614 at 24vdc but I am not sure of this. I do think that the winding should probably be different for 24vdc.

Here are a couple of 3.15" Dual Foot 50a-70a 24vdc Alternators that look like they might work with the engine.

• ZRD - High Output Replacement Alternators 24vdc - 50amp Ext reg. direct replacement of Yanmar Hitachi Alternator $520
• Balmar Series 6 60-24v-70a-SR $919

While these options are pretty expensive, there may be something available in 3.15 dual foot 50a 24v in the broader market that will fit.

It looks like I might not need to change to serpentine if I change to 24vdc Alternator. of course it means changing other things like batteries, wiring and having a DC to DC Battery Charger. The change to 24vdc will also help with wiring sizes, particularly since I'd like to move the batteries to the cabin, which will be further away. I could not use the Balmar ARS5 anymore, but Al Thompson's will work.

Current YM-3YM30 pulley measurements:
Crank Pulley Face / Alt Pulley = 4.75/2.75 = 1.73 Ratio ----> 4.75"/2.2"=2.15 ratio using Balmar 1303
This is not good enough, it should be at least a 2.4 or 2.5 ratio.
I don't think there is a pulley of 2" but that would get the ratio to 2.375 and the belt might object.

Quite obviously, the first thing I should do is make the existing 65a Balmar pulley smaller as the existing alternator will perform better. Hope I don't need the serpentine costs.

I would be very interested if 24vdc alternator will not produce as much heat.

[rgleason]

Marinehowto has an excellent sale for a well built alternator that will fit our 3YM30
CMI-90-ERH - 90A Hitachi Replacement Externally Regulated Alternator $299
This is not 24v, but it would be a possible replacement. I wonder if there is enough airflow openings to keep it cool, but we would be de-rating it to about 70a. The batteries would remain as 12vdc and I could keep using the ARS5 regulator.

I definitely need to get the 1.73 belt ratio up to at least 2.2


At gotomarine with search "Yanmar Alternators" I found some new Yanmar Alternators (I had been doing searches on 3.15 dual foot alternators and matching manuf. numbers) Look at this pdf Yanmar Alternators on page 79 and page 81 for external regulator and rectifiers.

Of interest were 24vdc alternators, no prices yet.

• 20025-24V (New 24V, 50-AMP) Rplc. Yanmar # 129900-77240
• 20026-24V (New 24V, 50-AMP) same but external regulation.

They also have 12v for Yanmar

• 20025 NEW 12V, 94-AMP for $183 - Dual foot, Yanmar #’s 129772-77200,119573-77201, 129470-77200Hitachi #’s LR155-20, LR180-03 Negative Ground
• 20028 12v 120a for $252.00 10-DN Style Alternator Dual Foot, Non-Regulated Isolated Ground, Heavy Duty Diodes, External Voltage Regulator # VR-1200, not included