Re: LiFePo4 batteries: Twin 24V Alternators on the main engine

Chris Paul

Hi Scott, 
Thanks for your reply.

Yes - more solar - Agree 100% 
A priority for me is to reduce generator time and the twin alternator idea had this in mind. 
Currently I have 780W on arch
I am considering about 400W on the railings as many other boats have.
I'm not happy with soft panels on the bimini.
   The bimini is expensive & time consuming to replace (maybe 3 months during cyclone season). 
   When I see older bimini's with flexible solar I also see stretched seams & sharp edges & places where water drips probably will come.

Please let me know how you can get 760W of hard panels above the Bimini. 
Maybe not possible on my SM as the boom is very close to bimini
(My crazy idea was to recut the main sail clew maybe 6-8" higher - thus lifting the boom enough for hard panels??)
(maybe your boom on the 54 is a bit higher??)

Also my boat came with a wind generator on the mizzen below the radar.
It is currently not connected & I am not sure I even want it because:
 1. The mizzen staysail cannot be used (I love ghosting in flat seas)
 2. An electrician told me it will not work well in conjunction with existing MPPT solar regulators and lithium batteries. 
     Probably needs a new regulator - hopefully someone can explain more about this.
     It will however work on a windy night! 
 3. It is noisy & a bit anti-social.
 4. Old technology, Expensive & time consuming to replace or fix (Solar now has more bang for the buck!)

So my redundancy plan is something like this:

Large battery bank 900Ah lithium + 100Ah of Lead as back up

Electrical cooking - (not using gas unless it is an emergency)
   still have gas connected but have not used since lithium was installed
   no filling of gas bottles - 
   no compliance problems

1KW Electric Outboard -  
   Adds about 25% extra electrical requirements to the existing Amel electrical use - 
      no flooding or starting issues, 
      she can talk on mobile phone while motoring, (we can easily talk to each other)
      light weight comes in 2 parts so no crane required - she sets it up by herself
We still have 15HP Yamaha 2 stroke OB 
   main engine back up - my redundancy plan if my Yanmar is out of action.
   speed, if required 
   After buying the electric outboard we hardly use the Yamaha.

Electricity generation - 
   Generator 200A , 
   Twin alternators hopefully 80A when set up, 
   Solar hopefully 60A, 20- 30A now 
   Wind 15A?? more likely 5A (even more likely ZERO AMPS)

So I have numerous options: 
   Once my twin alternators are set up if I run the engine for 2.5 hours it puts out 200AH = 1 hour of generator time
   Once my solar panels are increased I should save generator time.
   The mizzen staysail should also save some engine time.

So it is all a work in progress but I'm slowly getting there.

I will probably be in Whangarei, or near by, for cyclone season. 
I hope to do some cruising around NZ this summer.
There are 3 other Amels in Whangarei and it is a very friendly marina.
We don't have a car - just cycle or walk as most things are close by.

Regards, Chris Paul 
SV Glazig
SM #352 (2002)
Whangarei, NZ

On Monday, 15 August 2022 at 10:25:40 am NZST, Scott SV Tengah <scott.nguyen@...> wrote:


My first priority would be to increase your solar output. We are at 960 and have figured out a way to add 380*2=760w of hard panels over the Bimini. Assuming they're installed correctly, they just work. Take a look at half cut cells as they tolerate shading far better. 

Regarding alternators, I will preface by saying that I stuck with the standard Mastervolt 110amp 24v alternator that is spec'd on most 54s. I changed the external regulator to the Alpha pro II, which has a lithium profile. It outputs anywhere from 80-90 amps at my miserly 1300rpm (per Amel, the most efficient speed, maximizing range). I disagree with Bill that it has no meaningful impact on generator usage, at least in my case.

We have 450AH of Victron lithium batteries. My 11kw Onan has 200amps of 24v charging capacity. As you know, the lithium batteries will take full current until almost full, so my generator usage is very optimized.

I don't know how much you motor, but let's assume 400-500 hours. 400 hours X 80 amps from alternator = 3200 amp hours into my batteries. Even at my 200 amps of charging via Onan/230v chargers, that's 3200/200 = 160 hours of generator usage saved per year. Don't know about you, but as a result of that, we rarely run our generator and we're cooking with electric and running the dishwasher daily and water maker every third day or so.

For me, nearly eliminating my generator usage (we do run it now and then to make sure it doesn't become a rust ball) is not about saving diesel costs. It's about maintenance and the associated time to source diesel, replace parts, change oil, etc. And listening to that damn Onan. And of course, environmental considerations.

Another side effect is that while my batteries will happily accept 200amps until nearly full, they actually are happier taking 80amps. This gives them more time to top balance as they get full.

I know this doesn't help you decide between keeping your current setup or adding more alternators, but just want to state that our 24v engine alternator contributes a meaningful amount without adding additional operating hours.

How long will you be in Whangarei? We are in Fiji now, but intend to head there for cyclone season.

2007 A54 #69
SV Tengah

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