Visit our Popular Forums

**Dockhead** · 20-08-2018, 08:53

Quote:

Originally Posted by sailorboy1

I doubt there’s going to be experimental data of cycles for not recharging afterwards. That’s really “I’m a cruiser and my batteries lasted 4.3 years.”

You may be right, but since this reflects the actual use case of a fair number of cruisers (and probably other users of lead batteries), surely it's a study worth doing.

It would be right up MaineSail's alley -- he's done a bunch of stuff like this. Of course he's now crazy about lithium and probably doesn't care about lead batteries any more.

sailorboy1 · 20-08-2018, 08:56

I think I did a “how long do your batteries last” years ago here

Paul L · 20-08-2018, 08:56

Quote:

Originally Posted by newhaul

the bank I just got is basically drop in I just adjusted my solar to stop charging .2 volt below the banks max charge point . ( Lfp actually don't like to be charged to 100% ) Not to hard to do . Heck you should adjust the charge controller for each different manufacturers specs for their Gc2 Fla battery as well to maximise its life expectancy.

So no bms or lvc and hvc No separation of the charge bus,......?

Paul L · 20-08-2018, 09:02

Quote:

Originally Posted by sailorboy1

I doubt there’s going to be experimental data of cycles for not recharging afterwards. That’s really “I’m a cruiser and my batteries lasted 4.3 years.”

I think this is the most reliable data available and its not very reliable. You can average it out over a lot of boats. In fulltime use a cruising boat with a small ah bank vs a large ah bank makes up the two interesting categories. Which category shows longer battery life on average.

**skipmac** · 20-08-2018, 09:07

Quote:

Originally Posted by Dockhead

I wish MaineSail would comment.

As do we all.

There is no basis at all stated in that article, for the recommendation not to ever discharge below 50%. In the test, the batteries were discharged only to "just under 50%".

Well, I did mention the article contained no whys or wherefores. Basically do this because.

Quote:

Originally Posted by Dockhead

The only thing that this test demonstrates is that regular failure to charge to 100% ruins AGM's quickly. Whether FLA's are ruined as quickly, I don't know. The tested bank lost 30% of its capacity after only 30 partial cycles! Yowza! I did at least that many partial cycles to my own bank just in the month of July!!

Is your bank AGMs or FLAs? The issue of partial charging does seem to be overlooked by a lot (most?) boaters that consider switching to AGMs.

Quote:

Originally Posted by Dockhead

My first reaction to this is lithium looks awfully good, after reading this, for anyone who doesn't have solar.

Lithium looks great until you consider two things, the really high initial cost, not just for the batteries but to upgrade the charging system(s) and adding the battery management system. The second, if something happens and you screw up by overcharging or over discharging the batteries you have just made a very expensive mistake and one that cannot be remedied in any out of the way location.

I have to agree with A64s recommendation for sticking with FLA batteries for cruising in remote areas. A FLA setup is a lot less likely to totally die, more tolerant of mistakes and it's possible to patch up or jury rig until you can get somewhere to redo the whole thing. Most anywhere in the world there are people you could buy a few car batteries to get by for a while and they would be a drop in for a FLA installation. I guess you could do the same for a dead LiFePO system as well but with a little more reconfiguration of the charging systems required.

foufou · 20-08-2018, 09:14

While there may be an advantage to discharge to a lesser SOC the hassle of replacement might be enough of a consideration to stick with the 50% discharge rule of thumb

Garrettw · 20-08-2018, 09:29

I graphed the lifetime energy vs DOD for the three examples I saw in this thread: Trojan, Lifeline and that US Battery Manufacturers Consortium. This gives a somewhat rudimentary indication of overall value. Caveat is that it doesn't include more complex issues like short cycling your charging equipment and so forth. Also, I didn't pay attention to differences in chemistry on the charts so comparing one graph to another might be apples and oranges.

Y Axis is lifetime energy content. I left out the specific values since it doesn't matter (i.e. same whether 1000ah pack or 1ah pack). The higher the line is on the graph the better value you hypothetically get. Or said another way, the more lifetime energy you get out of the pack.

X Axis is % DOD

Some conclusions:

Trojan does appear to have a sweet spot at 60 to 70% DOD.
Lifeline looks like it falls off at 50% DOD.
USBMC's go-by seems to be linear indicating that if it were an actual brand, one should limit discharge to the minimum that your lifestyle would allow.

**newhaul** · 20-08-2018, 09:48

Quote:

Originally Posted by Paul L

So no bms or lvc and hvc No separation of the charge bus,......?

the bms is built into my battery pack from the manufacturer.
Why separate the charge bus? I personally have lots of solar and wind generation power (for my size boat) no alternator on my engine . Dynostarter puts out 11 amps and charges my little 500cca Fla start battery. ( I will have an alternator on the boat to install if for some odd reason I need the power to charge my Lfp bank. )
this is to replace the failed Fla house bank that came with the boat when I got it.

thinwater · 20-08-2018, 10:03

The assumption that a smaller bank that is discharged more deeply will suffer from not being fully recharged between cycles is a logical red herring. Because the bank is smaller, it will be easier to recharge (based on experience, not theory) from solar.

Either way, it is a false inclusion of a separate problem.

ramblinrod · 20-08-2018, 10:37

[QUOTE=thinwater;2700837]The assumption that a smaller bank that is discharged more deeply will suffer from not being fully recharged between cycles is a logical red herring. Because the bank is smaller, it will be easier to recharge (based on experience, not theory) from solar.

Either way, it is a false inclusion of a separate problem.[/QUOTE

I don’t know anyone made that assumption.

But the assertion that the lower discharged bank will be held at a lower state of charge longer, leading to a shorter life is a logical truth, EEE, if one accepts that the longer a battery is held at a lower state of charge, the greater the sulfation and the greater the sulfation the shorter the batter life.

If one doesn’t accept these principles, they need to gain a better understsnding of how batteries discharge and charge. Google wil help.

bank wsame size bank d

ranger58sb · 20-08-2018, 10:53

Quote:

Originally Posted by Garrettw

Y Axis is lifetime energy content. I left out the specific values since it doesn't matter (i.e. same whether 1000ah pack or 1ah pack). The higher the line is on the graph the better value you hypothetically get. Or said another way, the more lifetime energy you get out of the pack.

X Axis is % DOD

It would be useful to know something about the difference in magnitude on the Y Axis. If difference from lowest to highest is 300 kWh or Ah or whatever, that's different from 30000 kWh or Ah or whatever... former number not necessarily being all that significant, latter more likely to be very significant.

-Chris

**Dockhead** · 20-08-2018, 11:09

Quote:

Originally Posted by ramblinrod

. . if one accepts that the longer a battery is held at a lower state of charge, the greater the sulfation and the greater the sulfation the shorter the batter life . ..

A key question! Where do we get information to support this idea? Google doesn't help. It sounds like a good logical explanation, but where do we get this information? Calder doesn't write anything about it, and there's nothing turned up by Google.

**Dockhead** · 20-08-2018, 11:11

Quote:

Originally Posted by thinwater

The assumption that a smaller bank that is discharged more deeply will suffer from not being fully recharged between cycles is a logical red herring. Because the bank is smaller, it will be easier to recharge (based on experience, not theory) from solar.

Either way, it is a false inclusion of a separate problem.

So, this is another good logical explanation, but it conflicts with the other good, logical explanation. Which one is right?

This one seems to say that sulphation comes from not getting the battery up to full charge, not time held at low state of charge. And it's absolutely logical as stated by Thinwater.

kmacdonald · 20-08-2018, 11:31

Quote:

Originally Posted by thinwater

The assumption that a smaller bank that is discharged more deeply will suffer from not being fully recharged between cycles is a logical red herring. Because the bank is smaller, it will be easier to recharge (based on experience, not theory) from solar.

Either way, it is a false inclusion of a separate problem.

Agreed. The smaller bank discharged deeper will be more efficient and faster to fully recharge. Another advantage of deeper discharge.