Alternator Size with LiFePo4

[rgleason]

[QUOTE=OceanPlanet;2805523]

Originally Posted by Nicholson58

You might consider a small case 180A MGDC with external rectifier, for high continuous output. Or a shortened large case 250A with RR, with which we see near 240A continuous.

Yes, Bruce, the 180A MGDC was the one I was considering earlier.
Since then I've been reading the threads here and learned more about Lifepo4 charging and longevity.

It appears that for longevity, alternator charge rate should be .30C or less, and occasionally can be higher when needed. I am going to try to keep charging in the middle, from 10%-75% SOC with a faster C-rate of .35C-.4C (for lower SOC) and then drop it down to .3C and bring the voltage up to about 13.88v and stop, if more energy is needed for some unusual reason, I would then drop down to .2C and continue charging up to about 13.95v.

With a cruise daily demand of 100ah and an infrequent at sea daily use of 140ah (perhaps a little short due to the autopilot) I think a 200ah - 260ah bank would work the majority of the time.

200ah x .4C = 80a, oversize 150% = 120a alternator, 1.5hrx 80a = 120ah.
260ah x .4C = 104a, oversize 150% = 156a alternator, 1.5hrx 104a=156ah.

If the C-rate is lower
.3C x 200ah = 60ah x 1.5hr = 90ah
.3C x 260ah = 78ah x 1.5hr = 117ah
and SolarPV 100watts at dodger initially can make up the difference.
With two more 100w panels at the stern later.
Cruising use of the engine will likely be 30-45min in the morning and the same in the late afternoon for total charging time of 1.5 hours.

So it seems to me that an alternator that has a continuous output for 2 hours of 100a minimum, when hot would work.
I understand large frame alternators have a better chance of achieving good continuous ratings. Isn't the MGDC a large frame? Perhaps I should just look at the dimensions.


I have drawn a large frame alternator location that may work with a dedicate belt.

[rgleason]

Thanks EVM, that helps narrow it down. 130 amps continuous would be fine. What is your low rpm output, say at 750 engine rpm and 1000 engine rpm? I am looking for reasonably good performance, better than 40a, preferably 60a-70a .

Originally Posted by evm1024

Consider a 28Si. I was convinced to get one. 200 amps for less than $400. Of course I down rate it to 130 amps with the belt manager.

I have drawn a 28SI and with some adjustments it may work. See Small Boat Electrical for Sail Post #113
I may locate the alternator higher, so as to miss the manifold more.

It leaves the water pump">raw water pump running off the existing pulleys and adds a new pulley on the face of the 3YM30 which is aligned with the new alternator pulley which has been pulled forward to leave more room in back near the manifold. The belt will have good 180 degree contact and be tightened by adjustment of the alternator.

I will have to reconfigure the bracket and probably build a new one.
I may need an idler pulley for the water pump belt for adjustment.
I will have to move the system water hose.

[rgleason]

Al Thomason's VSR Alternator website

Wakespeed website

Alliance Wakespeed High Output Alternators and Wakespeed Alternators Facebook
mentions Rick Jones, former Balmar, Al's partner.


Hairpin, dual fan, etc. for gas engines.

[evm1024]

For fitting I just moved the alternator further away from the engine (back when I fitted a serpentine belt)

You can see how I made this alternator an external regulator one. here:

http://www.cruisersforum.com/forums/...on-204361.html

I don't have a number for 750 rpm off the top of my head. It was making 85 amps at 1000 at a nice low 125F to 135F on a normal 80 degree day.

The pulley is a bit large so it is not set up for low RPM and the belt manager was on to get the 85 amps (to a nearly full LiFePO4 bank)

I also have a write up on installing a serpentine belt for this alternator. (search is your friend)

Regards.

[rgleason]

evm1024

"It was making 85 amps at 1000 at a nice low 125F to 135F on a normal 80 degree day.

The pulley is a bit large so it is not set up for low RPM and the belt manager was on to get the 85 amps (to a nearly full LiFePO4 bank)"

EVM1024
The ratio from crank to alt is about 1 to 3 so at 1800 RPM cruise we will be turning the alt at 5400 RPM.
And at 1000 RPM the alternator could still produce significant output.

My engine area is quite narrow, but I think raising the alternator several inches will help.


Perfect, this what I would like to do.
1. Alternator Choices, SI28 or 200A J-180mount we build here, the CMI-ED200-ER,
2. Converting Delco 28Si to external regulation
3. Who makes TAD and Serpentine Belt? (Uses a K6 Belt)


SW Diesel is in Boston!
TAD serpentine kits


Serpentine Kits CVF


I have another place that will custom make the crankshaft pulley.

[tanglewood]

SW Diesel appears to be in So Cal, not Boston.

[rgleason]

Yes, I guess I was hallucinating. Thanks Tangle

Originally Posted by tanglewood

SW Diesel appears to be in So Cal, not Boston.

Just happened on some excellent posts about charging starting with Nebster's Post #176

As you move up in charge rate, the excess voltage rise grows substantially, and you can end up not storing as much energy as you planned, unless you do in fact add CV time.

A typical cell will reach only ~90% true SOC at 0.2C to 3.45V, whereas it will reach 96% SOC at 0.1C to 3.45V. If you are so brash as to select a charging system capable of something like 0.40C (ahem), the numbers decrease much further, and you simply must elect to enter absorption if you want to get full use of your battery pack.

My suggestion is: if you plan to do any charging above 0.1C, you should test and verify the charging results yourself before committing to a solution that only uses a CC charge strategy.

and ending with Mainesail's post #205

I see a lot of focus on "replacing Ah" with ideals and thoughts of getting back to full .... (not what nebster is discussing, he gets it)

This is a lead acid mentality. Instead simply focus on replacing only what you need for the next 12, 24, 36, 48 hours etc. and shut it down.

If you have an opportunity to get back to near full, by all means take it, but don't fuss about it daily. Spend the money now to size the bank for a few days worth of silence and you'll really begin to appreciate LFP even more.

For example we leave our bank at less than 50% almost every-time we leave the boat. When we get back to the boat I fire up the engine & alt first. By the time we stock the fridge, bar, ready the vessel, stow our gear, leave the hook and get out of the harbor, about 40 minutes +/-, we have replenished more than an entire days worth of energy + what ever SOC we left it at.. The motor, if fully warm, then gets shut down and the PV flipped on.

With the addition of the new Balmar SG200 we will no longer need to guess at the accuracy of our SOC via a Coulomb counter. I doubt our bank will see 100% SOC all that often. It's just no longer necessary... LFP is really, really quite simple if you can leave the lead acid mindset in the 60's

Maine Sail on charging Post #224

Why......? CC/CV charging will do all this for you. Set it at 13.8V - 14.0V and have it stop at .03C - .025C & you're done.
You're over complicating something that is actually quite simple.

Post #272

How do you know when to stop at .03C-.02C?

When you know your net charge current, accounting for house loads, you can now count how long it takes from the time you hit the target voltage until the time current drops to your desired tail cut off. You now set the absorb duration to do that. I have been doing this with the Balmar MC-614 for many years and well over 1000 cycles...

[rgleason]

Maine Sail I never thought to ask, what Charge rate do you use with your Alternator / Lifepo?

What is the max charge rate that you would use occasionally?

[tanglewood]

Originally Posted by rgleason

Yes, I guess I was hallucinating. Thanks Tangle




Just happened on some excellent posts about charging starting with Nebster's Post #176

and ending with Mainesail's post #205


Maine Sail on charging Post #224




Post #272

How do you know when to stop at .03C-.02C?

Go back and look at the graphs in the alternator/alternate charge profile thread. It's all right there.

[rgleason]

Originally Posted by tanglewood

Go back and look at the graphs in the alternator/alternate charge profile thread. It's all right there.

Alternator not regulating charge


Charging Profile


Charging Issues - solar bulk charge =12.65v, alternator=14v


Understanding a model for battery charge acceptance




Are any of these the thread you are thinking of?

[rgleason]

Well, I found some answers to my question on Maine Sail's MarineHowTo website.

https://marinehowto.com/marine-alternator-installation-tips-tricks/

1. For Constant Duty with small frame alternators, removal of internal rectifiers and remote rectifiers are required. This is what Marine Sail has done to charge a large LiFePo4 Bank.
2. Another alternative is to mount a large frame alternator which does not get as hot.
3. Alternator Output Cold and Hot Ratings are not "Continuous Duty", not even close, not even Balmar's ratings. The problem is a Continuous Duty rating is ship and installation dependent and impossible to measure.

https://marinehowto.com/lifepo4-batteries-on-boats/

1. Maine Sail advises "On my own boat I charge the 400Ah LFP bank at approx 145A to 13.8V and the current taper lasts only 30-35 minutes." So that is a charge rate of .3625C
2. He advises that LFP "can take immense current, and charge extremely fast, but really tend to do extremely well with .3C to .5C in charge current." - So it is entirely possible to charge at .5C occassionally when needed.
   
3. He also advises that approximately 80% of the LFP Bank is fully usable. It appears that 80% DOD is where to stop discharge to maintain battery #cycles. Also there is absolutely no need to fully charge these batteries, and actually it is better not to fully charge them all the time. (Therefore I am going to assume the max they'll be charged to is 95%, leaving 75% usable.) Also don't try to top off the batteries when coming back to the mooring. Maine Sail says "LFP batteries actually prefer to sit at 30-65% SOC"

I currently have 225ah Lead acid x .35 available = Total 78 ah fully available.

I am considering 200ah LFP x .75% = Total 150 ah available. almost double my current ah available. So I'll have more Ah available than a 400ah Lead Acid bank! The weight will be about 1/2 of the Lead Acid and I won't be plagued by the long charge tail to 100%SOC to properly maintain the batteries.

Charging this bank at .35C x200ah would require a continuous output of 70ah. Charging it at .5C x200 would require a continuous output of 100ah. So theoretically charging at .35C would almost recharge the available 150ah in 2.15 hours with the exception of the battery efficiency CEF which is quite good for LFP.

This is not as fast as I was hoping for, but it certainly is better than Lead Acid! I would be able to restore the current available capacity 78ah in a little more than an hour, so perhaps that should be my goal. Adding a little more LFP capacity would help, by keeping the charge rate at .35C and increasing the continuous duty amps needed for the alternator.

If I forego the .5C charge rate, I might be able to get away without a serpentine belt, but for this installation I think it would be best to change the belt.

[Delfin]

Originally Posted by rgleason

Well, I found some answers to my question on Maine Sail's MarineHowTo website.

https://marinehowto.com/marine-alternator-installation-tips-tricks/

1. For Constant Duty with small frame alternators, removal of internal rectifiers and remote rectifiers are required. This is what Marine Sail has done to charge a large LiFePo4 Bank.
2. Another alternative is to mount a large frame alternator which does not get as hot.
3. Alternator Output Cold and Hot Ratings are not "Continuous Duty", not even close, not even Balmar's ratings. The problem is a Continuous Duty rating is ship and installation dependent and impossible to measure.

https://marinehowto.com/lifepo4-batteries-on-boats/

1. Maine Sail advises "On my own boat I charge the 400Ah LFP bank at approx 145A to 13.8V and the current taper lasts only 30-35 minutes." So that is a charge rate of .3625C
2. He advises that LFP "can take immense current, and charge extremely fast, but really tend to do extremely well with .3C to .5C in charge current." - So it is entirely possible to charge at .5C occassionally when needed.
   
3. He also advises that approximately 80% of the LFP Bank is fully usable. It appears that 80% DOD is where to stop discharge to maintain battery #cycles. Also there is absolutely no need to fully charge these batteries, and actually it is better not to fully charge them all the time. (Therefore I am going to assume the max they'll be charged to is 95%, leaving 75% usable.) Also don't try to top off the batteries when coming back to the mooring. Maine Sail says "LFP batteries actually prefer to sit at 30-65% SOC"

I currently have 225ah Lead acid x .35 available = Total 78 ah fully available.

I am considering 200ah LFP x .75% = Total 150 ah available. almost double my current ah available. So I'll have more Ah available than a 400ah Lead Acid bank! The weight will be about 1/2 of the Lead Acid and I won't be plagued by the long charge tail to 100%SOC to properly maintain the batteries.

Charging this bank at .35C x200ah would require a continuous output of 70ah. Charging it at .5C x200 would require a continuous output of 100ah. So theoretically charging at .35C would almost recharge the available 150ah in 2.15 hours with the exception of the battery efficiency CEF which is quite good for LFP.

This is not as fast as I was hoping for, but it certainly is better than Lead Acid! I would be able to restore the current available capacity 78ah in a little more than an hour, so perhaps that should be my goal. Adding a little more LFP capacity would help, by keeping the charge rate at .35C and increasing the continuous duty amps needed for the alternator.

If I forego the .5C charge rate, I might be able to get away without a serpentine belt, but for this installation I think it would be best to change the belt.

I've gotten by with a double belted alternator putting out 130 amps without any dusting for the last 2,000 hours.

[rgleason]

Thanks Delfin, that is very helpful information.


Here is experience with a Mark Gasser 160a with remote rectifier, outputting 120amp regularly to 400ah Lifepo (C-rate of .3C) .

[rgleason]

Al Thomaston's response to some of my questions about the WS500.

http://www.cruisersforum.com/forums/...ml#post2808642

He'll be looking for Newhaul at the show.

[rgleason]

I think this alternator may be too big for our installation, but it looks interesting. The 14v, 325a J-180 mount would be way too big for our 3YM30 and would hit the exhaust manifold for sure unless we had a bigger engine space and custom brackets.

PDF with dimensions here

Read Typhoon's and Maine Sail Posts in this thread
http://www.cruisersforum.com/forums/...ml#post2061632

https://www.ecotechalternators.com/c...e-alternators/
use with Lifepo

https://www.ecotechalternators.com/testimonials/
Technical Advantages
https://www.ecotechalternators.com/a...mp-alternator/

More technical
http://www.ecotechalternators.com/wp..._Amps_Idle.pdf
Leads to questions about how they regulate it.

New patented technology: The unique use of permanent magnets enables the high output Eco-Tech 305-I alternator to generate 260 Amperes (135 Amperes for 28V versions) at 1,800 Alternator RPM as compared to 2000 RPM, the idle speed most often quoted by competitors.