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

[Fuss]

I'm thinking that these DC DC chargers are just there for boats with alternators that cannot handle running at full output.


Thats ok I guess, but for boats with high quality industrial large frame alternators then they don't need them and they can put their full charge into lithium without wasting their time and money on these compromise devices.


I see now that Battleborn has some funny shaped green device that they are promoting that gives your alternator a rest every 20 minutes.



Really, instead of this and these DC to DC chargers should we not be promoting decent high quality fit for purpose alternators first??

[sailorboy1]

Originally Posted by Fuss

Really, instead of this and these DC to DC chargers should we not be promoting decent high quality fit for purpose alternators first??

I am using my 22 year stock alternator with changes to the programing. Everything looks just fine.

[Fuss]

Originally Posted by sailorboy1

I am using my 22 year stock alternator with changes to the programing. Everything looks just fine.

That can be but we need some clarity here.


Victron and others are promoting not using your alternator to charge Lithium. At least not at full capacity. Which is a waste of a good charging resource in my opinion. Investing in a good alternator is much better than these workarounds.

Remember you just paid a lot for this new technology and then one of the big advantages of fast charging, gets throttled back to DC to DC charger of 30ah.


If you can pay for Lithium, you can at least do it justice and get yourself an alternator that can run long at full output.


Cruisersforum as experts have the possibility to set the record straight or give guidelines.


Thats all we need.

I think that decent fit for purpose alternators do not have this problem, thus I started the thread.

[bgallinger]

I have used a 100 amp Balmar alternator with a Balmar MC-614 external regulator to charge my batteries (3x Lithium house batteries and 1 x AGM engine start) for several years now without a DC-DC charger. I always charge the batteries to 100%. I also fitted a Balmar Transient Spike Protector on the alternator.

[Pete7]

Originally Posted by Fuss

Cruisersforum as experts have the possibility to set the record straight or give guidelines.

Thats all we need.

I think that decent fit for purpose alternators do not have this problem, thus I started the thread.

You're making the assumption that people are using the alternator and the primary charging source. I am not sure this is true and suggest a large number of members are using solar as the primary.

Now a nice big shinny alternator might sound good, but they are not cheap. Add external regulation and even more $$$ needed. Then we need to look at the belt situation. Single belt that used to drive a small automotive alternator isn't going to cut it, so serpentine belts, yes more $$$. Even worse trying to convert an older engine out of production even more more difficult relying on finding an after market company offering a solution.

So if you want fast charging from an alternator then it will cost. If however, you are content to use other methods for charging and keeping those $$$ in your bank account rather than someone else's pension fund, then DC>DC is an option.

We all have a choice. I chose solar as the primary and only use the DC>DC charger occasionally, twice in 2021 and only for tests in 2022. So no requirement to change the alternator at present thank you.

Pete

[Pete7]

Originally Posted by Fuss

I think that decent fit for purpose alternators do not have this problem, thus I started the thread.

Okay, design me a system. 31ft yacht, existing alternator 100A, 3/8th belt. Assume 220 LFP. Engine Volvo Penta 2003 raw water cooled.

Lets see what you can come up with.

Pete

[Fuss]

Originally Posted by Pete7

Okay, design me a system. 31ft yacht, existing alternator 100A, 3/8th belt. Assume 220 LFP. Engine Volvo Penta 2003 raw water cooled.

Lets see what you can come up with.

Pete

Why do you want to change the theme of the thread, that's the problem with threads they they don't stay on subject.


But you are right, I was not directing this at you.


I am directing it at people who are worried about their alternator overheating but would like to take advantage of their expensive lithiums large current acceptance over their old lead installation.
They have probably seen Victrons take on this and also seen some of the workarounds being promoted and so they are considering throttling their boats ability to deliver the maximum charge while motoring.


That's clearly not you...but the others might get something out of it.


Maybe some of the sailors have perfectly good alternators for their Lithium installation that can deliver full output but have throttled it with DC to DC chargers or some other work around for no good reason.


You never know, maybe someone else can explain that my opinion is wrong.

[sailorboy1]

Originally Posted by Fuss

That can be but we need some clarity here.

I have posted this a few times, but OK:

100a Balmar, single 1/2" belt, ARS5 regulator
bulk - 14.0V 12 minutes
Absorption - 13.8V 12 minutes
Float - 13.4V 6 hours
Belt manager - B4 20% reduction (I was running B3 with the lead acid to not have belt dust)
Alternator temp - set to 95C (haven't seen it get more than 88C)

4 - 100ah drop in $300/ea batteries with BMS

charges directly gto the LFP house bank
charges the start battery via a FET isolator

currently I have the regulator sense wire connected to the house bank, but am thinking maybe moving back to the alternator output lug

[Pete7]

Originally Posted by Fuss

Why do you want to change the theme of the thread, that's the problem with threads they they don't stay on subject.

I am not changing the thread theme particularly after reading the first and last paragraphs in your opening post.

Originally Posted by Fuss

I am directing it at people who are worried about their alternator overheating but would like to take advantage of their expensive lithiums large current acceptance over their old lead installation.
They have probably seen Victrons take on this and also seen some of the workarounds being promoted and so they are considering throttling their boats ability to deliver the maximum charge while motoring.

The reason I use a DC>DC is so my alternator doesn't overheat.

Originally Posted by Fuss

Maybe some of the sailors have perfectly good alternators for their Lithium installation that can deliver full output but have throttled it with DC to DC chargers or some other work around for no good reason.

I just don't see manufacturers fitting large alternators as standard on engines supplied to yacht manufacturers. I suspect if an owner has fitted a large aftermarket alternator in place, then they have also fitted an external regulator to reduce the risk of over heating, rather than use a DC>DC.

Originally Posted by Fuss

You never know, maybe someone else can explain that my opinion is wrong.

No your opinion isn't wrong, but is open to discussion on a forum. Just as my assumption that lots of people are using solar as a primary.

Pete

[jordanbigel]

Different courses for different horses. Why Victron (and others) may be pushing the DC-DC route is to make it easier (cheaper) for potential customers to buy their batteries.

As for CF, I've been reading threads here about how to charge LifePo4 with Alternator for years and I've read feedback from people here who have chosen both routes. So I do not think there is any shortage of people on CF advocating for direct LifePo4 charging from an alternator, and no shortage of information here on CF about HOW to accomplish that safely.

And I also agree with Pete above who said sailboat manufacturers do not equip their boats with suitable large frame alternators capable of direct LifePo4 charging at high rates (for large battery banks). I refit my boat 20 years ago with 4 gigantic 8D batteries, a large frame Balmar alternator, and a Balmar voltage regulator. So for me, switching to LifePo4 (last year) the choice was clear - and to prevent overheating I de-rated the alternator field signal by 40% and use a temp sensor which will allow the regulator to throttle back the alternator and if it starts to overheat. So far the longest time I have motored with this setup (starting with my 1200ah bank at about 30%) was about 8.5 hours during that time my large frame palmar was putting out over 100amps (after 8.5 hours the alternator was shut down by a relay I installed which stops charging at 85% SOC, adjustable of course).

Since this was the longest I've run the engine with the new LifePo4 bank, I monitored the alternator temp manually every hour (using a handheld laser temp sensor) and everything was stable (ie. once it reached max temp of about 150F it stayed there the whole time, never rising, which I take as a sign I could motor indefinitely without issue).

But I can understand someone with a much smaller bank (like sailorboy above with a 400ah bank) and an existing small frame alternator would choose the DC-DC route. Like I said at the top, different courses for different horses. Frankly, I don't see an issue here as you do.

[Jammer]

Originally Posted by Fuss

Really, instead of this and these DC to DC chargers should we not be promoting decent high quality fit for purpose alternators first??

My boat doesn't have room for the alternator I would like to have. This is almost universally the case on sailboats. There is really no practical way to solve this in most cases without extensive/costly bracketry and extensive, costly, and unsightly changes to cabinetry.

So like everyone else I run an overwound small-frame alternator and take measures to be sure it doesn't burn itself up.


Like most people I use a combination of solar panels, engine charging, and shore power to get enough electricity for refrigeration and electronics.

[s/v Jedi]

It doesn’t work like that. Alternators have been designed for a specific purpose and that is to charge LA batteries while also supplying energy for the normal operation of the vehicle.

The important part is that the thermal design was for the expected RPM and for the charge characteristics of LA batteries. They have never been designed to output full rated capacity continuously.

AFAIK there is no alternator on the market that was designed for LFP battery charging.

There are alternators designed for higher loads, I have sailed many years with 3 alternators bolted to my engine: the oem one plus two Lestec 225A Brute alternators which were beasts. Still, they were designed for charging LA house batteries at RPM’s for normal use of the engine, not high idling like we all want. So I had to de-rate them to be able to use them at lower RPM’s and of course they quickly reduced output when the long absorption charge phase of the LA begin.

Then there’s the question if the engine or the belt is overloaded at the RPM’s used for charging from the alternator. Many problems on that front as well.

Today, when using an alternator for charging a LFP house bank, the two main concerns that must be addressed are:

1 - the temperature of the alternator must be monitored and controlled by the regulator.

2 - the rectifier diodes must be protected against a HVC event.

That’s it. Hope we get LFP alternators soon

[sailorboy1]

Originally Posted by jordanbigel

But I can understand someone with a much smaller bank (like sailorboy above with a 400ah bank) and an existing small frame alternator would choose the DC-DC route.

I didn't chose the DC-DC route! I charge directly to my LFP house bank. I have motored for 6 hours with this setup, but doubt the alternator gets any hotter after it gets to whatever temp it is going to get. I have noted that when I open the engine cover and wait for the the ARS5 regulator to cycle through the displays that the alternator will cool down 5C in 1 cycle.

[sailorboy1]

Originally Posted by s/v Jedi

The important part is that the thermal design was for the expected RPM and for the charge characteristics of LA batteries.

Right in manual, 1400 rpm for cooling. Mine doesn't even get near rated output till then anyway.

[jordanbigel]

Originally Posted by sailorboy1

I didn't chose the DC-DC route! I charge directly to my LFP house bank. I have motored for 6 hours with this setup, but doubt the alternator gets any hotter after it gets to whatever temp it is going to get. I have noted that when I open the engine cover and wait for the the ARS5 regulator to cycle through the displays that the alternator will cool down 5C in 1 cycle.

Apologies, I must have been thinking of another post.