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Old 26-07-2017, 05:16   #31
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Re: Li-ion Battery Banks

For longevity you do want the alt's voltage setpoint at 13.8V max.

Balmar's external VR MC-614 does a good job.
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Old 26-07-2017, 06:12   #32
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Re: Li-ion Battery Banks

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For longevity you do want the alt's voltage setpoint at 13.8V max.

Balmar's external VR MC-614 does a good job.
The actual alternator or the charger that picks up the feed from the alternator/regulator?

The Relion batteries want 14.2-14.6v at 50amps according to the manufacture's spec sheet. That's well within spec of my Sterling alternator to battery charger, but outside my old PWM solar controller.

I can't afford LiFePo4 at the moment anyway, but those who can, probably have better controllers and chargers than I do.
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Old 26-07-2017, 12:10   #33
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Re: Li-ion Battery Banks

"voltage setpoint at 13.8V max"
That's just 3.45v per cell. Isn't that a good bit lower than most manufacturers call for?
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Old 26-07-2017, 13:58   #34
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Re: Li-ion Battery Banks

Yes, exactly. My theory is that the manufacturers don't want their batts lasting decades.

You only lose maybe 1-2% capacity off the top end staying away from that shoulder. But along with lower than EV discharge rates, you don't need ongoing cell-level (re)balancing.

If you go to a higher voltage, then make sure you just STOP when you hit it, no "absorb" stage at all. Also no float is best.

With 13.8(3.45pc) you can keep going until amps drop to ~.01C

But stopping earlier is healthier than risking hitting the shoulder.
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Old 26-07-2017, 14:07   #35
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Re: Li-ion Battery Banks

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The Youtube couple Gone with the Wynns, have an expensive LiFePO4 battery bank on board. Looking through their equipment list, they don't have any special alternators or the like. They've not reported back any problems in the year or so they've been sailing.
No offense to them, I enjoy their videos quite a bit and they are intelligent people... but the system was installed by professionals at great cost. Its quite possible that they are missing a few details in their publication.
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Old 26-07-2017, 14:12   #36
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Re: Li-ion Battery Banks

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The actual alternator or the charger that picks up the feed from the alternator/regulator?
The bare Alt has no control.

The voltage regulator recommendation here is external, Balmar MC-214, some Alts need adapting to replace or bypass the built-in VR.

If you are talking about additional DCDC chargers like Sterling B2B models, yes, then you can keep a stock VR feeding a Starter, do your fine controls to feed the LFP bank from there through the Sterling, but I think the high-amp models get dear pretty quickly.

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Originally Posted by mikedefieslife View Post
The Relion batteries want 14.2-14.6v at 50amps according to the manufacture's spec sheet.
See above, I haven't seen a vendor in the market yet that optimizes for longevity. Follow them and you'll be replacing the bank much sooner than necessary.

Maybe Bruce Schwab's Lithionics system does?

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I can't afford LiFePo4 at the moment anyway, but those who can, probably have better controllers and chargers than I do.
Yes, the bare cells are just one (very vulnerable) component.

That's why people buy packaged systems with proprietary BMS, paying 7x what a top quality lead bank costs.

Doing it yourself with OTS protective devices is much cheaper, could probably get started playing around for well under a grand.
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Old 12-07-2018, 08:14   #37
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Re: Li-ion Battery Banks

My LifePo system has been running without problems since 2016. In 2.5 years I never had to re-balance the cells, right now they are 23mv out. If your solar panels output is in the low 20 V, I don't think there is much of an advantage to have an expensive MPPT controller, MPT should be fine. Has anybody got a different opinion on this?
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Old 12-07-2018, 08:18   #38
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Re: Li-ion Battery Banks

What is MPT supposed to be, as opposed to MPPT?
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Old 12-07-2018, 10:20   #39
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Re: Li-ion Battery Banks

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My LifePo system has been running without problems since 2016. In 2.5 years I never had to re-balance the cells, right now they are 23mv out. If your solar panels output is in the low 20 V, I don't think there is much of an advantage to have an expensive MPPT controller, MPT should be fine. Has anybody got a different opinion on this?
Sorry, a typo.
It should be MPPT controller, PWM should be fine, not MPT.
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Old 12-07-2018, 11:03   #40
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Re: Li-ion Battery Banks

The gains from MPPT technology is only slight. Somewhere between +5 to +15% is probably the right ballpark as an average, but nevertheless this is a useful bonus especially when solar panel wattage is restricted by size constraints, as it is on so many vessels.

A Vmp of 20v is more than enough to see these benefits with most MPPT controllers (although a Voc of 20v is a little low for any controller). There is little or no extra benefit going to higher voltages, but with high voltage panels MPPT controllers must be used. Lower voltage panels or “12V” panels can use MPPT or non MPPT controllers.

Lithium batteries by virtue of their lower charging voltages should benefit more from MPPT controllers than lead acid batteries when using low voltage panels.
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Old 12-07-2018, 11:16   #41
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Re: Li-ion Battery Banks

Seamn, I'm with noelex on this.

You have to realize that MPPT controllers *are* just enhanced PWM controllers. Both use PWM for the actual charging, and that itself gives you about a 10% gain in charging speed over plain DC charging.

But when your battery only needs 14 volts, and your panels are putting out anything higher? A PWM controller just throws that extra power away. If the battery needs 14 (or whatever number, it may be more like 12.4 after the night) and the panel is putting out 30% higher voltage? The PWM is throwing that away. The MPPT is putting it into the batteries.

That means, unless you have so many panels that you literally can afford to throw out power, the MPPT is always going to give you something extra.

It also means that on a sunny morning, when you're looking at incoming storm clouds and hoping to get a full charge before the 48-hour storm comes in, the MPPT unit is going to be charging your batteries is something like 10% less time, giving you better odds of getting a quick charge before the clouds roll in or the sun goes down.

Yes, MPPT costs more. So do good batteries, or larger panels. Individual choice of whether you need more, bigger, faster, or cheaper, on any part.
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Old 12-07-2018, 11:23   #42
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Re: Li-ion Battery Banks

The problem with most PWM controller is, they usualy are dirt cheap, and people buying them even chose the cheapest among them.

There are well built out there, but most have cheap components, that often fail, they have - if any - only pre-set profiles for lead acid or GEL batteries , sometimes AGM.
They are rearly programmable, and also have often insufficient protection towards reverse polarity, over voltage, over current, over heat. Some even have built-in reconditioning, that cannot be turned off.

All this makes them a risky investment regarding an expensive LFP bank.

I am not saying, they are all scrap, some work really well.

In contrast the MPPT controllers (especially the real ones, not the fake chinese PWM with MPPT sticker on) are more complex and many are adjustable, have a great input voltage range and decend over current protection, but they are pricey.
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Old 12-07-2018, 13:49   #43
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Re: Li-ion Battery Banks

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Originally Posted by noelex 77 View Post
The gains from MPPT technology is only slight. Somewhere between +5 to +15% is probably the right ballpark as an average, but nevertheless this is a useful bonus especially when solar panel wattage is restricted by size constraints, as it is on so many vessels.

A Vmp of 20v is more than enough to see these benefits with most MPPT controllers (although a Voc of 20v is a little low for any controller). There is little or no extra benefit going to higher voltages, but with high voltage panels MPPT controllers must be used. Lower voltage panels or “12V” panels can use MPPT or non MPPT controllers.

Lithium batteries by virtue of their lower charging voltages should benefit more from MPPT controllers than lead acid batteries when using low voltage panels.

Another factor to consider here is that the advantage an MPPT controller gives is for only the bulk portion of the charge. With LiFePo this is the majority of the charge, not so with LA.


MPPT vs. PWM Controllers Photo Gallery by Compass Marine How To at pbase.com
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Old 12-07-2018, 14:07   #44
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Re: Li-ion Battery Banks

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Another factor to consider here is that the advantage an MPPT controller gives is for only the bulk portion of the charge. With LiFePo this is the majority of the charge, not so with LA.
[
Yes, this is good point, once out of bulk mode, controllers are effectively throwing away power so there is no advantage in the voltage conversion inherent in MPPT controllers.

There are exceptions. The popular Victron controllers in “absorption” mode are not in a true absorption phase and therefore are often using MPPT tracking to boost the available output.
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Old 12-07-2018, 14:43   #45
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Re: Li-ion Battery Banks

Charging is not the power's only job.

Any useful loads running, e.g. holding plate freezer, will benefit from greater output, not draw off the bank.
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