DC to DC charger - not needed for boats with proper alternators.

[rgleason]

Yes, Delco Remy 28SI (160ah) is rated at 10k rpm. Using a smaller serpentine pulley on the alternator (say 2.1"-2.2") increases the rpms to improve cooling, then modifying for external regulation and limiting output to 90-100 amps with the regulator helps with longevity and heat. The final requirement is to protect the alt from HVD by using the appropriate BMS and regulator. There are many ways to skin this cat, and there is no single answer. Best to have a serious engineered solution.

[newhaul]

Originally Posted by s/v Jedi

To be clear, there are two requirements for charging a lithium bank from the alternator:

1. A smart regulator with correct charging profile AND a temperature sensor mounted on the alternator to derate when it overheats.

2. A BMS capable of shutting down the alternator just before a HVC happens. This is why many choose another option because those BMS’s cost more.

Not quite. I charge my lifepo4 from my alternator via a dc dc charger.
No external regulator
No fancy BMS

[s/v Jedi]

Originally Posted by newhaul

Not quite. I charge my lifepo4 from my alternator via a dc dc charger.
No external regulator
No fancy BMS

No, you don’t. You charge your lfp with a DC-DC charger.

[Statistical]

Originally Posted by hjohnson

The issue is that Lithium and Lead need significantly different charging profiles. On my boat, the alternator is doing strictly what the Lithium BMS is calling for, and that would not be healthy for the Lead.

The prime example is that most of the time, I want my Lithiums sitting at between 13.2v and 13.3v where it's best to let them rest, but I want the Lead to be sitting at 13.8v, which is where you want to store Lead.

The Orion-Tr I have was like $200, which isn't significantly more expensive than other options, and does its job with aplomb.

Exactly the AVR would be a step backwards if the two banks have different chemistries.

If someone really wants to use an AVR they should have a lithium starter battery too. That only works if the two banks are the same voltage. However in this case DC to DC charger (or AC charger) is a better solution.

Starters use a lot of power they use negligible energy. Assume 2000W starter motor running for 5 second. That is 2.8W. So even a 20W charger will replace that in 8 minutes. Hell if Victron made a 5W DC to DC charger recharge and sustain a lead acid starter battery.

[Putt-Putt]

Originally Posted by Statistical

Starters use a lot of power they use negligible energy. Assume 2000W starter motor running for 5 second. That is 2.8W. So even a 20W charger will replace that in 8 minutes. Hell if Victron made a 5W DC to DC charger recharge and sustain a lead acid starter battery.

The problem with that kind of thinking is the start batteries are more than likely, also the engine run batteries.

On my ride, 2 sets of electronic engine displays plus the ECM consume about 10 Amps per engine.
All easily powered by one 24V alternator.

Not so much by even a 200W (8 Amp) DC2DC Charger.

Perhaps you run a Gardner.

[newhaul]

Originally Posted by Putt-Putt

The problem with that kind of thinking is the start batteries are more than likely, also the engine run batteries.

On my ride, 2 sets of electronic engine displays plus the ECM consume about 10 Amps per engine.
All easily powered by one 24V alternator.

Not so much by even a 200W (8 Amp) DC2DC Charger.

Perhaps you run a Gardner.

Not much power used on mine just the volt gauge and the tach.
Old school mechanical engines.
Mitsubishi k2b branded as a westerbeke 10-2
And a 75 amp Chevy 10si frame alternator .

[donradcliffe]

Originally Posted by CaptainRivet

a 185A balmar plus blowers and you only get 110A out of it...thats weak, an OEM alternator for 1/3 the price is capable of that performance.

why is the belt manager on 60%???? small engine and does it draw to much hp or do you have a heat problem?

That 185A Balmar with blower should have no problem when running at 170A for 6h straight, its a heavy duty alternator.

You need a reliable system. If you pull 170 amps out of an 185 amp alternator, you are going to need to carry two spares. In addition, if you run the engine in the tropics, the blowers are going to make your life much nicer.

[hjohnson]

Originally Posted by donradcliffe

You need a reliable system. If you pull 170 amps out of an 185 amp alternator, you are going to need to carry two spares. In addition, if you run the engine in the tropics, the blowers are going to make your life much nicer.

More correctly, keep the alternator from overheating. Just let the regulator manage the alternator temperature, and it will give as much as it safely can.

[CaptainRivet]

Originally Posted by motion30

But that's not the whole story. Does your smart regulator allow you to charge the Start batteries and the house battery bank without them being connected?

How do you charge a battery that's not connected? Same LFP chemistry parallel them, charge currents splits itself. Different chemistry DC2DC or ArgoFet splitting diode.

[CaptainRivet]

Originally Posted by donradcliffe

You need a reliable system. If you pull 170 amps out of an 185 amp alternator, you are going to need to carry two spares. In addition, if you run the engine in the tropics, the blowers are going to make your life much nicer.

If it's the right low rev heavy duty large case 185A alt definitly not as this runs even at 185A as correctly speced for this usage.
But for these monsters of alternators a wakespeed regulator +alt temp probe is a no Brainer and cares about all and make sure you don't smoke them.
And yes Simi if you have a cruising RPM of ultralow 1150RPM then you have to take that into account and you need a low rpm speced alternator (eg school bus alternators speced for 1500-3000RPM) and most likely need to even modify their gear ratio.
10kRPM alternator doesn't matter which case is just wrong here by default or need to be derated massively so it makes actually no sense to use this.

[Simi 60]

Originally Posted by CaptainRivet

If it's the right low rev heavy duty large case 185A alt definitly not as this runs even at 185A as correctly speced for this usage.
But for these monsters of alternators a wakespeed regulator +alt temp probe is a no Brainer and cares about all and make sure you don't smoke them.
And yes Simi if you have a cruising RPM of ultralow 1150RPM then you have to take that into account and you need a low rpm speced alternator (eg school bus alternators speced for 1500-3000RPM) and most likely need to even modify their gear ratio.
10kRPM alternator doesn't matter which case is just wrong here by default or need to be derated massively so it makes actually no sense to use this.

So I google school bus alts and a 28si 24v 110 amp come up
The 24v 28si is a 10,000 rpm alternator
From the spec sheet

SPECIFICATIONS
Performance Output
24 Volts 110 Amps
Maximum Speed 10,000 RPM Continuous
12,000 RPM Intermittent

https://www.delcoremy.com/alternator...ype/school-bus

The 24v 36si that I am getting is a 10,000 rpm alternator
From the spec sheet

SPECIFICATIONS
Performance Output
24 Volts 105 Amps
Maximum Speed 10,000 RPM Continuous
12,000 RPM Intermittent

They also specifically mention for the 12v 36si being able to output ...

Superior output producing up to 170 Amps at road speed and 100 Amps at idle

Sounds like they expect low speed usage

[Simi 60]

Originally Posted by Putt-Putt

Delco states that they are able to be run at 10,000 RPM continuous. Unless the crank pulley on your diesel auxiliary is >12" in diameter you likely have no chance in over revving the alternator. Particularly if your engine is limited to 1850 RPM. Really?

The problem is that at 3000 RPM the fan is delivering about 30 percent of it's cooling capacity while the windings are generating about 75 percent of the maximum output, which also means it's producing 75 percent of the maximum heat.

Running this way with the Delco internal regulator which has no clue what temperature is and can't reduce field current based on temperature, you will likely cook it.

NTA855m Cummins
33si and 36si alt is pretty much standard equipment

I am buying 2 alts, both unused - one came off of a K19 and the other off an NTA855

[Simi 60]

Pulled the trigger on Sterling 24v DC to DC @ 35 amp X 2
On sale in Oz for $375 each

Far easier install than the Balmar or Wakespeed imho
Starts will still get amps during anchor lift without the need for additional charger
And the alt will be derated from 105 amp to 70amp with the ability to turn off a charger if needed for further derate

Plus if the Balmar or Wakespeed has issues I have 0 charge
Unlikely both Sterling's will crap out together so the system has inbuilt redundancy.

[newhaul]

Originally Posted by Simi 60

Pulled the trigger on Sterling 24v DC to DC @ 35 amp X 2
On sale in Oz for $375 each

Far easier install than the Balmar or Wakespeed imho
Starts will still get amps during anchor lift without the need for additional charger
And the alt will be derated from 105 amp to 70amp with the ability to turn off a charger if needed for further derate

Plus if the Balmar or Wakespeed has issues I have 0 charge
Unlikely both Sterling's will crap out together so the system has inbuilt redundancy.

Sounds like a good call to me

[Jerry Woodward]

I have a cat with a Balmar 6 series 120A alt on the starboard engine (Yanmar 2gm20f) with serpentine belt. It is regulated by the MC614 regulator. It also has an alternator protection module. I installed it several years ago after consulting with Rod Collins. At the time I had 400ah of FLA batteries that I knew would need replacing soon. The Balmar was wired directly to the house bank. The port engine has the stock Hitachi alt charging the single sealed starting/reserve battery wired to both starters. A 1-2-Both switch allowed paralleling both banks to allow starting from the house bank, or running house loads off the reserve battery. This configuration worked very well, with the caveat that the LA house bank took a long time to get to full charge

Early this year, I replaced the LA batteries with 400ah of Lithium (2 Kilovault 2400). The choice was to wire both alts to the start/reserve battery and use a DC-DC charger to charge the lithiums, or to leave the wiring as is with the Balmar wired directly to the lithium bank and the Hitachi wired to the start/reserve. I chose the latter because I wanted the maximum charging when motoring. I also upgraded my solar to 560 Watts, also wired to the house bank through Victron controllers.

After 2 months in the Bahamas, I am very glad I have the Balmar wired directly to the house bank. When running the starboard engine, I was usually seeing 80amps continuous going into the house bank. I'm usually running the engines for an hour or so to get in and out of anchorages and more if there is no wind, so having this rapid charging was really important.
Another unanticipated advantage was that I could run my AC watermaker on the inverter when motoring underway! It is a Cruise RO 30gph, and draws about 90amps DC on the inverter. I would typically pull out the Honda generator when at anchor to make water. One day, I thought to try the watermaker when motoring underway and it worked very well with solar and alternator powering house loads and the watermaker.