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**a64pilot** · 14-09-2018, 13:10

I would suspect that it’s not damage to the LFP battery they are suggesting, but possibly if the LFP bank disconnects due to it being charged, the potential damage the DC system that is no longer being dampened by a battery bank, functioning as a large capacitor?
That is what I think funny when I see the car stereo guys when the attach a big capacitor to their amps, that are of course connected to the battery. What do they think the battery is, if not a monstrous cap?

senormechanico · 14-09-2018, 13:16

Next time my LiFePo4 bank needs a hit from my alternator, I'll hook up my Fluke ScopeMeter to it and take a photo of the ripple, if any.
I'll also take a photo at the same time at the alternator output terminal.

This might be awhile before it gets posted.
The solar keeps the bank full.

john61ct · 14-09-2018, 14:29

Quote:

Originally Posted by tanglewood

implied is that an alternator direct connected to an alternator is an inadequate filter and will damage the LFP cells.

I assume you mean alt connected to battery.

No you are correct, long as proper voltage and amps no problem for the batt.

I see two benefits only.

Load dump to protect the alt diodes.

Ability to drive DCDC charger with no battery.

AFAICT just putting a cheap lead bank in also solves those issues, seems silly to me for the price.

But if paying the money to avoid that is worth it to some, then fine they should buy it.

senormechanico · 14-09-2018, 15:22

Make your own for cheap if you think you need one:

https://www.ebay.com/itm/16V-20F-Ult...r=512347314813

There's another version rated at 48 volts. Still under a hundred bucks.

https://www.ebay.com/itm/Super-Capac...oAAOSwdMBa4gRH

tanglewood · 14-09-2018, 15:38

Quote:

Originally Posted by hellosailor

tanglewood-

There are companies selling "alternator stabilizers" for the loud car stereo folks too. Same thing.

IF your alternator, with integral or external regulator, is working properly you should only be getting uniform clean DC from it. If you've ever heard "alternator whine" on a car or boat stereo, you know sometimes an alternator is leaking AC.

Take any multimeter, set it to AC, and connect it to the alternator output. You should see no AC voltage if it is working properly. Now also reverse the multimeter leads and recheck--because some multimeters are built in a way that will show AC voltage one way, and not the other, even though in theory both should be the same.

If there's no AC voltage coming through, you don't need that big filter capacitor. If you need the filter capacitor, it is just masking a problem in the alternator.

While connected to a battery, or not?

hellosailor · 14-09-2018, 15:41

tanglewoood-
Connected, as usual.

A64-
In a car stereo, a big capacitor can make a difference. Around 1980, I could show you a brand new Audiovox car stereo that sold for 1/10th the price of the GM product. And, if oyu hit heavy bass (cannon fire in a master lp recording of the 1812 Overture) the radio would literally go SILENT because it needed more power than the car could supply for the heavy bass. Go figure.

In theory, giving a better stereo an extra "power now" source can help during those moments. Of course, running battery cable instead of the usual dinky SAE wiring would have done that too. If the radio wasn't so incompetent to begin with.(G)

**a64pilot** · 14-09-2018, 15:51

The battery is a big Cap.
Car stereos have always been bogus with their claims and there is often just no logic with the claims.
I’ve seen 1,000W stereos, with a 10 amp fuse. That just isn’t possible.

Neither here nor there though, other than to try to explain how marketing works at times.

However in this case I think there is more to this thing than we are supposing.

tanglewood · 14-09-2018, 16:01

Quote:

Originally Posted by hellosailor

tanglewoood-

Connected, as usual.

.(G)

Then I agree you will only see ripple, and hopefully very little. But that because of the connected battery. The alternator’s open circuit output is half wave rectified three phase AÇ. Wow, that’s a mouthful.

So in question is the relative filtering capability of LA vs LFP. Sterling claims their filtering is better for LFP and they can otherwise be damaged by an alternator’s inherently AÇ output. In other words they are claiming that more filtering is required when connecting to LFP or you risk battery damage. Seems to me like a stretch of a claim.

john61ct · 14-09-2018, 16:09

Yes, there are several product lines from Sterling that I call a solution looking for a problem, the "creative" marketeering Force is as strong as the engineering with this one.

But there are people with lots of extra money, and there may be some with a niche situation that actually get good value.

But maybe Maine Sail will come along and outline a use case where this unit is worth every penny!

senormechanico · 14-09-2018, 19:28

Quote:

Originally Posted by a64pilot

I’ve seen 1,000W stereos, with a 10 amp fuse. That just isn’t possible.

With inline current limiter circuitry (not just a fuse) and a huge capacitor, you would have the equivalent of an internal battery ready to deliver huge instantaneous power.
Therefore, a 1,000 watt peak output would be perfectly attainable.
That said, I've never seen one but it would be possible.

Delfin · 14-09-2018, 21:36

Quote:

Originally Posted by tanglewood

It looks like not much more than a supercap, and even says so on the cover.

Implied in the description is that alternator output to an LFP without a parallel LA or supercap will damage the LFP. So saying the LFP as a filter in place of an LA battery will damage the LFP.

Has anyone heard of issues charging LFP directly from an alternator (assuming proper regulation)? I haven't.

None in my usage. It is an Ample Power 130 Ah alt. I de-tuned it to 80% via the Balmar and it charges up the LFP just fine.

**Dockhead** · 15-09-2018, 01:55

Quote:

Originally Posted by john61ct

99% use cases the alternator still goes to a lead Starter batt, so based on KISS I agree keeping this functionality separate..

You should keep in mind that on larger cruising boats, dual alternators with separate alternators for house and for start is fairly common. More or less all Oysters, Moodys, HR's, etc. over 45 feet from the last 20 or 30 years. So I think considerably less than 99% of cases are single alternator to start batt.

My use case is like that and I'm sure many others considering going to lithium have this issue with no good way to have lead between the alternator and the lithium bank.

**Dockhead** · 15-09-2018, 02:03

Quote:

Originally Posted by john61ct

I assume you mean alt connected to battery.

No you are correct, long as proper voltage and amps no problem for the batt.

I see two benefits only.

Load dump to protect the alt diodes.

Ability to drive DCDC charger with no battery.

AFAICT just putting a cheap lead bank in also solves those issues, seems silly to me for the price.

But if paying the money to avoid that is worth it to some, then fine they should buy it.

Yes, he doesn't say that it's needed just for alternator to lithium connection.

He says:

"This product is essential if alternators are used directly onto Alternator to Battery Charger or Battery to Battery Charger without being attached to a starter battery."

So just for to protect the alternator from inductive voltage spike you don't need that -- you can use this:

https://sterling-power.com/products/...tection-device

It does look like this thing (the "alternator linearisator") is a patch for his B2B and "A2B" chargers, so that they can be used with lithium which can be taken off line rather than floating.

tanglewood · 15-09-2018, 05:25

Quote:

Originally Posted by Dockhead

You should keep in mind that on larger cruising boats, dual alternators with separate alternators for house and for start is fairly common. More or less all Oysters, Moodys, HR's, etc. over 45 feet from the last 20 or 30 years. So I think considerably less than 99% of cases are single alternator to start batt.

My use case is like that and I'm sure many others considering going to lithium have this issue with no good way to have lead between the alternator and the lithium bank.

Agreed with this sort of configuration. We have dual 200A, continuous duty alternators dumping 100% into LFP. Start batteries are charged from generator and or wing engine alternators, and B2B off the LFP bank.

With proper controls, there is just no benefit to mixing lead in with the LFP, so we have it only as an emergency replacement via manual switches for totally failed LFP.

Other aspects of our dynamics are different too. We use much more power than many other boats, and recharge away from the dock is always via ICE. We have solar, but it can only carry loads during the day, and isn't enough to do any measurable recharging. So no good way to do a finish charge on LA other than running a gen for a lot longer than you would like.

In this sort of an arrangement, LFP is a god send.

And what I think all this really shows is how much the "right" answer can vary from boat to boat. Saying that "best practice is X, Y, and Z" probably just means the situation hasn't been evaluated with any real thought. And it ties back to the need for skilled techs who can make such an evaluation and come up with a couple of good alternatives for "your" boat.