Depth of Discharge Myth?

[Dockhead]

Originally Posted by a64pilot

I think Main Sail sort of sealed the deal, and pretty much stated that it’s not a myth.
Surprisingly no one challenged him.. . .

It's pretty hard to challenge the guy who has done the real testing in an exhaustive and scientific way, and published it. The guy with an impeccable record of intellectual honesty.


Sealed the deal for me.



Also, I did get a response from Trojan saying the same thing as what MaineSail is telling us.


So my own conclusion to the original question in this thread is that the cycle life charts don't apply to real life usage and that you really do want to avoid discharging below 50% as much as possible.


I was asking this question to try to be sure I really understood the issue before making a decision to go to lithium or not.





I'm still curious about the exact mechanisms by which lead-acid batteries fail, and how we can operate them better to make them last longer, so I'm still reading about Ostwald Ripening of lead sulfate crystals, the real deal on positive plate corrosion, and other issues. I've come to the conclusion that the Wikipedia/Nigel Calder level of explanation of what is happening is greatly oversimplified, and I feel sure that there is a lot more to know which would be useful in practice for operating our batteries better.





I also have come to the conclusion that lithium, or possibly a lithium/lead hybrid system, makes sense for my particular use case. I think you need either a decent sized solar system or regular (not constant, but regular) access to shore power, to operate lead acid batteries reasonably well. For years I had neither, and was murdering lead acid batteries because they were sitting at a partial state of charge whenever I left the boat on her mooring. Now I'm spending winters in a marina and it's not so bad, but I'm still off grid 4 or 5 months a year, and my use pattern is simply not good for lead batteries, which hardly me last 3 years being used like that. My present set of Trojans are only 2 years old and already showing signs of lost capacity. Lithium totally solves this problem -- they are happy to be left at 50% or even 20% charge, so just switch them off when you leave the boat and forget about it. How much time did I waste during the years on my mooring trying to get a really good finishing charge on the batteries before leaving -- I even bought a Honda generator to use for this so that I wasn't wearing out my heavy duty diesel generator running it for hours at light load. A ridiculous PITA -- slave to my batteries.



As to the cost: the lithium cells themselves are less than double the cost of the equivalent quantity (based on usable power, not nominal amp/hours) of quality flooded lead batteries -- in Europe (other markets will have different cost ratios). Even adding to that the one-time cost of acquiring an appropriate BMS and modifying the electrical system, and the cost of lithium is not ridiculous compared to the cost of a quality FLA bank -- again, in Europe (YMMV in other markets). So for my particular use case, lithium will have paid for itself already at 5 years or so, and that's just the economics (for my particular use case), not touching on the advantages of lithium in operation and freedom from fiddling with finishing charges.



So thanks to everyone for the interesting discussion. I will continue reading, and I'll post again if I come across something really interesting, but meanwhile I will continue working on the hybrid bank design, too.

[ranger58sb]

Originally Posted by newhaul

you are correct I should.
First off lots of reading so I had a clue as to what I was doing .
Then I installed a system on my last boat to test .
Since that time the price has come way down.
I have to admit I have only installed 7 systems complete and worked on an additional 14 systems .
That is not counting all of the systems I have remotely assisted in designing for people doing self installs.
I am no expert on Lfp but I do try to expand my knowledge as much as possible.

Seems like more hands-on experience than many.

-Chris

[rgleason]

Great tests and info. Are these correct?
A64pilot - T-105 gc2?
Leaseonlife - Deka gc2?
Newhaul - Li?

Two observations:
How do yet adjust Genasun GV-10 pb couldn't find instructions?
This problem getting to 100SOC suggests that smaller size banks might be better, that solar size and adjustible solar controllers are essential, and that Firefly batteries might be a reasonable choice.

What solar controllers are adjustible?

Dear wife thinks I'm obsessed about soc and batts -' just get new when needed. Shes sick of it.

[daletournier]

Originally Posted by rgleason

Great tests and info. Are these correct?
A64pilot - T-105 gc2?
Leaseonlife - Deka gc2?
Newhaul - Li?

Two observations:
How do yet adjust Genasun GV-10 pb couldn't find instructions?
This problem getting to 100SOC suggests that smaller size banks might be better, that solar size and adjustible solar controllers are essential, and that Firefly batteries might be a reasonable choice.

What solar controllers are adjustible?

Dear wife thinks I'm obsessed about soc and batts -' just get new when needed. Shes sick of it.

Bluesky controllers can be adjusted allowing dropping down to float when end amps are reached or what ever amps you program into the controller. You can also have absorption on a time setting if you prefer.

[LeaseOnLife]

Originally Posted by rgleason

Great tests and info. Are these correct?
A64pilot - T-105 gc2?
Leaseonlife - Deka gc2?
Newhaul - Li?
...
What solar controllers are adjustible?
...

LeaseOnLife has

• 660Ah Lifeline AGMs in three banks
• 1000W solar, some shaded depending on boom position, with 5 Victron SmartSolar or BlueSolar Mppt controllers, which are very programmable plus have bluetooth to smart phone and can also be read by wired connection to Raspberry PI
• BMV-700 also connected to the PI

[LeaseOnLife]

Originally Posted by daletournier

Bluesky controllers can be adjusted allowing dropping down to float when end amps are reached or what ever amps you program into the controller. You can also have absorption on a time setting if you prefer.

But is that Amps of solar or Amps going into the battery? I guess Amps of solar.. So the solar controller doesn't really know trailing amps of the battery ?

[daletournier]

Originally Posted by LeaseOnLife

But is that Amps of solar or Amps going into the battery? I guess Amps of solar.. So the solar controller doesn't really know trailing amps of the battery ?

It's wired to a shunt, therefore it is able to measure battery acceptance amp rate. Thus the regulators can be programmed to drop into float once end amps are reached.

[newhaul]

Originally Posted by rgleason

Great tests and info. Are these correct?
A64pilot - T-105 gc2?
Leaseonlife - Deka gc2?
Newhaul - Li?

Two observations:
How do yet adjust Genasun GV-10 pb couldn't find instructions?
This problem getting to 100SOC suggests that smaller size banks might be better, that solar size and adjustible solar controllers are essential, and that Firefly batteries might be a reasonable choice.

What solar controllers are adjustible?

Dear wife thinks I'm obsessed about soc and batts -' just get new when needed. Shes sick of it.

gc2 on Spencer when purchased switch to Lfp on replacement time. 200 watts solar on it .
(Selling on contract).
Islander 24 was Fla 4 Dd 100 watts solar. P30l controller. Current boat defender had grp 27 car batteries when I got it . Switched to Lfp 400 watts solar, p30l controller 400 watts wind internal controller. ( all controllers adjustable.). Still restoring that boat. Current 100ah looking to eventually have 200ah custom built in 2 packs one bank.
Installing md2 with no alternator. Just the dynostarter using small Fla for start battery. ( totally isolated from the house power system. Questions pm me I would be happy to assist as possible.

[rabbi]

Originally Posted by rgleason

What solar controllers are adjustible?

The newer Victron Energy ones can be configured by App

Originally Posted by rgleason

Dear wife thinks I'm obsessed about soc and batts -' just get new when needed.

Get what? New wife?

[newhaul]

Originally Posted by rabbi

Get what? New wife?

trust me its cheaper to get new batteries every 3 years

[ramblinrod]

Originally Posted by newhaul

gc2 on Spencer when purchased switch to Lfp on replacement time. 200 watts solar on it .
(Selling on contract).
Islander 24 was Fla 4 Dd 100 watts solar. P30l controller. Current boat defender had grp 27 car batteries when I got it . Switched to Lfp 400 watts solar, p30l controller 400 watts wind internal controller. ( all controllers adjustable.). Still restoring that boat. Current 100ah looking to eventually have 200ah custom built in 2 packs one bank.
Installing md2 with no alternator. Just the dynostarter using small Fla for start battery. ( totally isolated from the house power system. Questions pm me I would be happy to assist as possible.

What LFB Batteries and BMS have you installed?

[newhaul]

Originally Posted by ramblinrod

What LFB Batteries and BMS have you installed?

rod I bet I have the same or similar experience with lfb batteries that most people on the forum do however this current line you are trying to do is exactly what you reported against me in the Fla vs Lfp thread.

Btw lfb batteries are single use lithium batteries like the ones recommended for use in the early digital cameras. Also the ones that the " energizer bunny " is currently pushing.

[ramblinrod]

Originally Posted by newhaul

rod I bet I have the same or similar experience with lfb batteries that most people on the forum do however this current line you are trying to do is exactly what you reported against me in the Fla vs Lfp thread.

Btw lfb batteries are single use lithium batteries like the ones recommended for use in the early digital cameras. Also the ones that the " energizer bunny " is currently pushing.

I have no idea what you are talking about???

You stated you have field experience installing LFP batteries; what LFP batteries and BMS system do you have this experience with?

(LFB was a typo).

[evm1024]

Originally Posted by ramblinrod

I have no idea what you are talking about???

You stated you have field experience installing LFP batteries; what LFP batteries and BMS system do you have this experience with?

(LFB was a typo).

Tit for tat

Rod, You have not confirmed your number of LiFePO4 installs. Perhaps you should state it clearly before asking other. How are we to form an opinion of the usefulness of what you post?

You do profess to be an expert and well able to decide what is the best course of action but you do nothing to establish your bona fides in regards to LiFePO4 installs.

Perhaps you should give a little to get a little. Just state the number of LiFePO4 installs you have done.

While I'm at it we all know that an ABYC certification is only worth the person who holds it. All of the surveyors and ABYC techs I've talked to are in complete agreement that most ABYC techs know less than they should.

This of course is no indication of your skills. It only says that holding up an ABYC cert is not enough to give the holder credibility. Direct experience and positive customer reviews is a much better indicator along with the praise of your peers.

[senormechanico]

Kinda OT, but I have run across several supposedly "Certified" sewing machine techs I'd not trust with newer $10K and up sewing computers.
Several of the the victims of those shops have wound up bringing them to me for proper fixes.