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

[s/v Jedi]

Originally Posted by GreenWave

As I am in midst of upgrading to LFP, I am catching up on this thread, and you sir, just solved my biggest question/problem. I had been trying to figur eout if I could do what you suggest here (using the Victron Smart BMS) but this could work for sure.

Thank you. So many disregard this tip because they find the SmartBMV too expensive to buy…. while buying a $1,000.- BMS

[Simi 60]

Originally Posted by Fuss

So there we have it, Lifepo4, no different to a large AGM bank from the previous decades or a big 2v traction bank like I had as far as alternators are concerned.

So how do you explain us killing off Delco 24v 26si large frame alts charging AGM on two seperate occasions?

[Fuss]

Ah,well, I don’t know … but it sounds like a similar problem to lifepo4 that existed in the past… which is what i mean… nothing new

[CaptainRivet]

Originally Posted by s/v Jedi

Thank you. So many disregard this tip because they find the SmartBMV too expensive to buy…. while buying a $1,000.- BMS

Absolutely agree.
And even if you have a 1000$BMS and willing to spend that much on a BMS then you should spent the 50 bucks more then a smart shunt and get a BMV instead and set it up as Jedi explains as last resort.
I have a BMV712 that was used far beyond its capabilities for the lead in the other hull and actually connected it lately as Jedi described above to LFP as last resort in case my BMS fails plus this delivers now additionally to cerbo the battery data. One of many things i learned here. Thanks Jedi for sharing things like this and for free.

you need a shunt anhow to measure ah and SOC and a BMS can fail too doesn't matter how much it costs, actually very easy when eg balance cable shorten, so this tip is a nobrainer with LFP.

[newhaul]

Originally Posted by Fuss

Ah,well, I don’t know … but it sounds like a similar problem to lifepo4 that existed in the past… which is what i mean… nothing new

My system by my design requires a DC TO DC 60 amp to protect my oversized ( for my engine ) 75 amp 23si chevy truck alternator( stock on my 10- two was 35 amp mitsubishi .
if I hook up direct as you suggest saying I won't have issues?
Are you going to pay for the new alternator?

[CaptainRivet]

Originally Posted by Fuss

Ah,well, I don’t know … but it sounds like a similar problem to lifepo4 that existed in the past… which is what i mean… nothing new

Again wrong and ... its Fundamentally different:
A big AGM bank (which is a major fire hazard by itself) has still a very high resistance. if its getting small enough through paralleling the resistance gets that low that it is fouling the Standard regulator in producing high output but that for quite a small amout of time in bulk, most time the alternator spend is in absorption with much smaller load. If there is still quite a high resistance and a bit of undersized cable or corroded connection that already saves your alternator.
It doesn't also need a surge protection due to this.

LFP the internal resistance is basically not existent
means very close to a short and its actually the cabling from alt to bank and fuse and connections thats present a bit of resistance to alternator but standard regulator is fouled to wide open full throttle,"give me all you can till you die" and this constantly as a LFP is 99% of time in bulk=full throttle and thats why the alternator burns out much faster. You also need a surge protection as resistance that limits surge current is basically not existent.

The key to survive and max relaible output of an alternator with LFP doesn't matter if 35A plastic or 300A heavy duty one is alternator temp management and the temp at the stator is what need to be managed, not the casing.
To get around this you can use a DC2DC with around max 50% of your alternators rating (if you have a good ventilated engine room, if bad go down to 30%) thats limiting the load and due to this. Why because its a well known fact that in boats without the cooling wind and often bad ventilation the alternator needs to rely on its self cooling capabilities which is normally in the range of 30-50% of rating.
Most newer stock alternator have temp management whichbis quite basic and if you modify for external regulation you loose that temp management.

Small 3 and 4 zylinder Volvos and Yanmars are delivered now with the 115A Mitsubishi alternator which has a very good conservative temp management and delivers 70-80A in the beginning and then is regulated back to 50-60A depending on your engine room ventilation. So 50% of rating. This alternator is developped for light commercial trucks in high temp countries like africa with a high current needs eg cooling trucks that often stand longer in one spot=rely on self cooling. But in this setup it turns at 6000-9000rpm up to 13000rpm but a orange line at 15000RPM. Not possible in many boats as the pulley on the crankshaft is limited in size so you can be happy if its a 1:3 ratio (actually Volvo D1/2 is 1:2,65, only the bigger D4 has 1:3,15) so alternator turning 2000 till 6000RPM at max further reducing self cooling capacity and often the heat exchanger only present in boats is sitting on the back of the alternator reducing its self cooling capabilities further.

This 115A Mitzi you cannot put directly on a LFP BUT no problem to put on a big agm bank. For LFP you should get the Nordkyn VSR200 regulator that without modofications turns it into a fully regulated alternator and keeps the factory temp management and you normally get constant 85A out of it with the Nordkyn relaible and save sonthe temp management enables it to pull nearly 75% of its rating in standard gearing 1:2:65. You can improve that to 100-110A by gearing it to 1:4. You reduce its lifespan in half but its only 250Euro remanufactured, so worth doing that if you can fit that big of a pulley.

[Fuss]

There is no difference between a Lifepo4 bank and a large AGM bank. If an alternator running full field maximum output is 100 AH then this is what it puts out regardless of battery type.
Sailingharry sums it up so I don’t have to rewrite it…..
---Quote (Originally by Fuss)---
Ah,well, I don't know . but it sounds like a similar problem to lifepo4 that existed in the past. which is what i mean. nothing new
---End Quote---
Here here! The problems that people have with LFP is that they take a severely undersized lead system, and try and install an adequate/ample LFP. They would have the same issues if they simply upgraded their lead system. On my 800Ah AGM bank, with 270A of alternators (total from two), I can easily charge at 170A or so for an hour or more until I hit acceptance and start backing off the charge rate. If I only had a 150A alternator, that would be more like 2-3 hours before hitting acceptance. When I go to LFP, the loads on the alternators will extend slightly, but the change would be irrelevant. Any boat with an AGM bank of any meaningful size (over about 300Ah) and a modest alternator (under 150A) already has a temperature sensing regulator (or already has fried their alternator!).

[CaptainRivet]

Originally Posted by newhaul

My system by my design requires a DC TO DC 60 amp to protect my oversized ( for my engine ) 75 amp 23si chevy truck alternator( stock on my 10- two was 35 amp mitsubishi .
if I hook up direct as you suggest saying I won't have issues?
Are you going to pay for the new alternator?

For sure he doesn't pay. Again just blabla.
Well and i bet he put temp sensor but didn't use them to properly manage the alternator.
At the end we will figure an undersized cable and corroded connection saved his alternator and the 140 degrees C was a wrong measurement.
The same as his engine has in the end a 2,5kw starter that needs just needs 400-500A surge capabilities and his engine manufacturer hugly overspeced by stating you need a 1400CCA battery. But Fuss stating the EVE cells can do 1400cca by pulsing and other bs he wrote. So it was surge peaks of max 500A in reality which is below spec of 2C peak why 4x280AH EVE sells survived that 9 month...
Was always the same reason of a 2nd faulty installation issue that saved guys like him from equipment frying or boat burning down.

[newhaul]

Originally Posted by CaptainRivet

For sure he doesn't pay. Again just blabla.
Well and i bet he put temp sensor but didn't use them to properly manage the alternator.
At the end we will figure an undersized cable and corroded connection saved his alternator and the 140 degrees C was a wrong measurement.
The same as his engine has in the end a 2,5kw starter that needs just needs 400-500A surge capabilities and his engine manufacturer hugly overspeced by stating you need a 1400CCA battery. Otherwise a 4x280AH EVE sells cannot survive that 9 month...
Was always the same reason of a 2nd faulty installation issue that saved guys like him from equipment frying or boat burning down.

I don't even know what engines or what vessel he has . My westerbeke 10- two can be started with the battery off of a lawn tractor . 350cca but I'm oversized with a grp 24 fla on it .

[CaptainRivet]

Originally Posted by Fuss

There is no difference between a Lifepo4 bank and a large AGM bank. If an alternator running full field maximum output is 100 AH then this is what it puts out regardless of battery type.
Sailingharry sums it up so I don’t have to rewrite it…..
---Quote (Originally by Fuss)---
Ah,well, I don't know . but it sounds like a similar problem to lifepo4 that existed in the past. which is what i mean. nothing new
---End Quote---
Here here! The problems that people have with LFP is that they take a severely undersized lead system, and try and install an adequate/ample LFP. They would have the same issues if they simply upgraded their lead system. On my 800Ah AGM bank, with 270A of alternators (total from two), I can easily charge at 170A or so for an hour or more until I hit acceptance and start backing off the charge rate. If I only had a 150A alternator, that would be more like 2-3 hours before hitting acceptance. When I go to LFP, the loads on the alternators will extend slightly, but the change would be irrelevant. Any boat with an AGM bank of any meaningful size (over about 300Ah) and a modest alternator (under 150A) already has a temperature sensing regulator (or already has fried their alternator!).

The problem is you have no idea what you talking about and constantly mixing up things to fruit salat and try turning them around to proove your blabla bs statements which are simply wrong.

Its not an irrelant and a slight change going from AGM to LFP, its Fundamentally different.

[Simi 60]

Originally Posted by CaptainRivet

Its not an irrelant and a slight change going from AGM to LFP, its Fundamentally different.

Very little change for us.
Reprogramming the multiplus and the mppt and some extra fusing and cabling was pretty much it

[newhaul]

Originally Posted by Simi 60

Very little change for us.
Reprogramming the multiplus and the mppt and some extra fusing and cabling was pretty much it

Yep but what would happen if you hadn't made the changes ? The charge profiles are significantly different .
I was lucky no engine and the onboard charger was a simple 10 amp unit and batteries were done . so blank canvas to install what I wanted .

[CaptainRivet]

Originally Posted by Simi 60

Very little change for us.
Reprogramming the multiplus and the mppt and some extra fusing and cabling was pretty much it

If you have the right equipment that can be adapted. And you still kept your lead and went with DC2DC, so its not directly connected to LFP.

Your low rev setup with beefy alternators is actually the prime example when an expensive wakespeed regulator fully integrated via CAN to BMS and 2 temp probes per alternator really makes sense to get reliably the max current from your low reving beefy alternators and being a motoryacht thats a much used charging source that makes sense to be optimzed in performance and reliability.


You use 2x DC2DC plus lead battery to limit current output from alt and them getting too hot. Thats static fixture based your fried ones before and only put a bandage on the wound instead tackle the route cause of your very low revs and resulting high operating temps on your alternators as they need to rely on their even further reduced self cooling capabilities because they run on lower revs so each A more output creates exponentially more heat due to missing cooling air.

[Simi 60]

Originally Posted by CaptainRivet

some stuff

Well, that's the 4th time I've read that and not 100% sure I fully understand

But I think it was
Get an expensive Wakespeed with all this other "stuff" so it can throttle my alt back to around 70% so it doesn't cook
Because somehow it's so much better than the easy and more affordable dc2dc X 2 which ......wait for it.......uses 70% of the alts output so has the same result?

and being a motoryacht thats a much used charging source that makes sense to be optimzed in performance and reliability.

We've been out here full time for seven years and haven't had or used this "much used" charge source in all that time.
Even went a year or more without an alt at all, so that shows how much it was used.

[CaptainRivet]

Originally Posted by Simi 60

Well, that's the 4th time I've read that and not 100% sure I fully understand

But I think it was
Get an expensive Wakespeed with all this other "stuff" so it can throttle my alt back to around 70% so it doesn't cook
Because somehow it's so much better than the easy and more affordable dc2dc X 2 which ......wait for it.......uses 70% of the alts output so has the same result?


We've been out here full time for seven years and haven't had or used this "much used" charge source in all that time.
Even went a year or more without an alt at all, so that shows how much it was used.

A wakespeed costs 600Euro and 2x Sterling DC2DC is about the same on sale, not on sale more expensive. And even if 200 more expensive thats nothing in boat bucks...
The difference is the wakespeed is regulating it dynamically and really regulating the alt reliably to its max output possible and on very hot days this might be even cut back to 80% while on colder maybe only 40%. How this really is the wakespeed will tell you...and adapt dynamically and reliable to it for the same amount of money.
Not so the DC2DC is fixed at 70% derating without taking the actual root cause alternatur temp into account. And on very hot days that might be even too less and you fry them a 2nd time.its playing lottery. Or do/did you have constant temp monitoring on the alternator over a longer periode to see its fix 70% derating will do it independently from surrounding temps. But still then the wakespeed solution is superior for the same money spent.

If the alternator on a your motoryacht are that unimportant why did you invest in them at all?