Reply
 
Thread Tools Display Modes
 
Old 10-10-2016, 04:12 PM   #21
Guru
 
MurrayM's Avatar
 
City: Kitimat, North Coast BC
Country: Canada
Vessel Name: Badger
Vessel Model: 30' Sundowner Tug
Join Date: Jul 2012
Posts: 2,461
Quote:
Originally Posted by tfmkevin View Post
(hangs head in shame as propeller beanie spins slowly to a halt)
Good one

That goes in my quiver of stolen quotes, right beside "Well, slap my ass and call me Judy!"
__________________
Advertisement

__________________
"The most interesting path between two points is not a straight line" Murray Minchin
MurrayM is online now   Reply With Quote
Old 10-10-2016, 05:25 PM   #22
Guru
 
dhays's Avatar
 
City: Gig Harbor
Country: United States
Vessel Name: Kinship
Vessel Model: North Pacific 43
Join Date: May 2015
Posts: 2,498
Quote:
Originally Posted by sunchaser View Post
I think tfm is having fun. Heck if we looked at every boating add on as having to be the cheapest alternative think about how many marine related companies would go out of business. Why have a boat if we can't pi$$ away some coin while actively engaging in our chosen hobby at the same time.

Being an electrical guy he enjoys the hunt. No different than many others are doing and posting about it on TF. Right now I am in the final design stages of adding an additional AP setup. Keep the old hiccupping AP 20 and add a Furuno 711. Silly investment, yes, but why not?
I agree. More power to Kevin. I look forward to seeing how these work out in the long term. I will need to change out my house bank at some point (original 6 year old sealed LA batteries right now) and wouldn't mind upgrading the performance in the same footprint if I can afford it. I am very happy to have other boaters experiment on the bleeding edge and pave the way for the rest of us.
__________________

__________________
Regards,

Dave
SPOT page
dhays is offline   Reply With Quote
Old 10-10-2016, 05:40 PM   #23
Veteran Member
 
City: Norfolk
Country: VA
Vessel Model: 48' duck
Join Date: Aug 2015
Posts: 47
Quote:
Originally Posted by tfmkevin View Post
(hangs head in shame as propeller beanie spins slowly to a halt)
At this point my next house battery will be a LiFePO4, but who knows what i will settle on next year.

When i was doing research on early this year i was told that my 200 amp alternator that is under spun might not be a good idea and suggested a few 100 to 150 options. There was also a long talk about voltage regulators and how some do not act well to lithium batteries.
choppywater is offline   Reply With Quote
Old 10-10-2016, 05:51 PM   #24
Senior Member
 
Retriever's Avatar
 
City: Anacortes, WA
Country: USA
Vessel Name: Safe Harbour
Vessel Model: Nordic Tug 37
Join Date: Apr 2014
Posts: 138
I've spent a bunch of time buddy boating with Kevin and Laura, including several weeks in the Alaskan wilderness over the summer. No shore power for a hundred miles. As the owner of a similar boat with a conventional battery bank, I was pretty envious of their battery bank setup.

When they woke up in the morning, they had a full tank of hot water for showers. When I woke up, I started the generator, waited for 20 minutes, and then took a shower.

While I neurotically checked SOC to be sure I never dipped below 50%, they didn't worry, since LiFePO4 batteries aren't damaged by deep discharge.

As their batteries dwindled to 15% SOC, voltage was still above 13. When mine get to 50%, they're near 12 volts. With higher, more stable voltage, motors on the boat should be a lot happier.

I typically ran the generator for 30-60 minutes, both morning and evening. They barely ran their generator at all. Don't get me wrong—I'm not afraid of running the generator (it hardly burns any fuel and is whisper quiet)—but not having to even think about electrical usage is super nice.

Sure, there are lots of ways to cut electrical consumption. But when you're on the boat for five months, mostly in the wilderness, little comforts of home are awfully nice. Turning on the tap and getting hot water or being able to plug in whatever household gadget you want whenever you want makes cruising feel less like camping, which I sure appreciate!
Retriever is offline   Reply With Quote
Old 10-10-2016, 07:31 PM   #25
Senior Member
 
Toolbuddie's Avatar
 
City: Huntsville, AL
Country: USA
Vessel Name: Sea Note
Vessel Model: Mainship 40
Join Date: May 2014
Posts: 174
Thanks AL for posting this up, Thanks Kevin for the explanation.
This is the most interesting thing I have read today. Some blaze trails, Some are glad they do!
I can go back to doing nothing now!
Dave.
Toolbuddie is offline   Reply With Quote
Old 10-10-2016, 08:54 PM   #26
Guru
 
C lectric's Avatar
 
City: Somewhere
Country: somewhere
Join Date: Oct 2007
Posts: 1,406
tfmkevin

KUDOS to you.



Thank you for the write up.
C lectric is online now   Reply With Quote
Old 10-10-2016, 11:45 PM   #27
Moderator Emeritus
 
BruceK's Avatar
 
Join Date: Oct 2011
Posts: 6,015
Quote:
Originally Posted by Bruce B View Post
Lithium batteries...
Not yet, not for me!
All I can think of is the Samsung Galaxy Note 7...Bruce
Well yes, but it could be more a Samsung issue than a LI one. I`m hearing even the replacement phones have similar problems.
Here we had numerous house fires from Samsung top load washing machines catching fire. It may not be simply an LI issue.
__________________
BruceK
Island Gypsy 36 Europa "Doriana"
Sydney Australia
BruceK is offline   Reply With Quote
Old 10-10-2016, 11:48 PM   #28
Al
Guru
 
Al's Avatar
 
City: ketchikan, Alaska
Country: usa
Vessel Name: 'SLO'~BELLE
Vessel Model: Marben-27' Flybridge Trawler Pilothouse Pocket Cruiser[
Join Date: Apr 2012
Posts: 1,210
tfmkevin- Wow!! So pleased that you have taken the time from your busy boating to contribute to the forum.It was my desire when I posted your blog.
I am so looking forward to meeting the two of you as I have with several of forum members {assuming your adding your name} on your next voyage North.
That we have passed in the night so's to speak, in different harbors during the past year and before not having done so.

Al-Ketchikan 27' Marben Pocket Cruiser
Al is online now   Reply With Quote
Old 10-11-2016, 08:46 AM   #29
Senior Member
 
Join Date: Aug 2008
Posts: 196
When I installed my LiFePO4 system a friend who was a retired CEO of a lithium mining operation preached to me the dangers of lithium. And there are truly dangers with raw lithium. But my system was proven safe before I installed it and remains so. Many, many differences between LION and LiFePO4. Just because they both contain lithium doesn't make them the same. Actually you have a better chance of burning up an alternator than you do with the cells.
folivier is offline   Reply With Quote
Old 10-11-2016, 11:51 AM   #30
Member
 
Trundlebug's Avatar
 
City: River Trent
Country: UK
Vessel Model: Profile 33
Join Date: Jul 2015
Posts: 17
I'm amazed you only have a 6 gal hot water tank, if I've understood correctly.
No wonder you're constantly having to use supplementary heating. But it's at a cost, and it's inefficient, even if it works for you.

My boat originally had a 9 US gal hw tank, which ran out after 2 people had a shower. As you also found.
So, as I had the space in the engine room I installed an additional 12 gal tank in series with the original, so now we have a total of 21 gallons of hot water, all heated by the waste heat of the engines, and it's enough for 4 showers plus dish washing, plus a wash and shave the next morning without any problem.

Because the second tank is installed in series, it means it doesn't take any longer to heat up that first bit of hot water (eg washing up after getting going, hw is available in just a few minutes) but with more time it heats up the second tank after the first is hot, and we have both hw tanks fully hot after about 2-3 hours running.

Worth considering, as it's much more efficient, although I appreciate the space taken up is probably filled by your generator (which I've always tried to avoid fitting).
Trundlebug is offline   Reply With Quote
Old 10-11-2016, 08:42 PM   #31
Guru
 
twistedtree's Avatar
 
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 2,166
Quote:
Originally Posted by folivier View Post
When I installed my LiFePO4 system a friend who was a retired CEO of a lithium mining operation preached to me the dangers of lithium. And there are truly dangers with raw lithium. But my system was proven safe before I installed it and remains so. Many, many differences between LION and LiFePO4. Just because they both contain lithium doesn't make them the same. Actually you have a better chance of burning up an alternator than you do with the cells.
Good point. That lead in conventional batteries is pretty nasty stuff too.

I think the biggest risk with LiFePO4 is that your charging protocol isn't just right any you trash your $4000 bank of batteries. For all the fussing we do over lead acid battery charging voltages, etc., they actually can take quite the licking and keep on ticking.
__________________
www.MVTanglewood.com
twistedtree is offline   Reply With Quote
Old 10-13-2016, 01:37 PM   #32
Member
 
tfmkevin's Avatar
 
City: Portland, OR
Country: USA
Vessel Name: Airship
Vessel Model: 2013 Nordic Tug 34
Join Date: Sep 2014
Posts: 19
@Trundlebug - Your two-tank system sounds interesting!

Unfortunately, there is zero available space in our Nordic Tug 34' engine room to add even a slightly larger water heater. In fact, when we eventually have to replace or service the one that's there, it will be a definite "ship in a bottle" type operation. Since our boat is 3 years from factory new, we'll probably try to get as much use as we can out of this one before we upgrade to something possibly better insulated.

One thing I am considering: Probably for safety/liability reasons, our system has a temperature regulator that limits the engine heating to 120 degrees F. If we bypass that, the water would get considerably hotter while underway. We'd be trading off the risk of potentially very hot water at some times with some electricity savings.
tfmkevin is offline   Reply With Quote
Old 10-13-2016, 04:25 PM   #33
Member
 
tfmkevin's Avatar
 
City: Portland, OR
Country: USA
Vessel Name: Airship
Vessel Model: 2013 Nordic Tug 34
Join Date: Sep 2014
Posts: 19
Way too much technical info about charging lithum

Quote:
Originally Posted by twistedtree View Post
Good point. That lead in conventional batteries is pretty nasty stuff too.

I think the biggest risk with LiFePO4 is that your charging protocol isn't just right any you trash your $4000 bank of batteries. For all the fussing we do over lead acid battery charging voltages, etc., they actually can take quite the licking and keep on ticking.
That's a VERY good point, and perhaps it warrants some explanation - at the risk of being too technical and writing way too much.

There are several things to consider when maintaining and charging LiPeFO4 batteries. The four most important are:
1 Don't allow any cell to discharge below the minimum voltage
2 Don't allow any cell to be charged at over the maximum voltage
3 Don't allow any cell to be charged at over the maximum current
4 Don't allow the battery to be exposed to excessive heat

Lithium Iron Phosphate batteries actually have a nominal cell voltage of 3.2V. To make a "12V" battery pack for a boat, we put four of these cells in series, which gives us a pack with a nominal voltage of 12.8V.

Then, (in our system) each of these sets of four cells has a capacity of 100Ah, so we have six sets of these in parallel to make a 24-cell pack with 600Ah capacity at 12.8V nominal.

It's important to remember that this is not just a "12.8V battery," though. It really is six sets of four 3.2V batteries/cells in series/parallel. That means we want those sets of 4 cells in series to be kept "balanced". I'll talk more about balancing in a minute.

The normal working voltage of a cell is in the range of 3.0-3.3V. That makes our 12V pack have a normal working voltage of 12.0-13.2V.

With that in mind, let's take the four issues one at a time:
1. "Don't allow any cell to discharge below the minimum voltage."

The minimum discharge (without damage) is about 2.5V per cell, which is 10.0 V for our array.

There are two lines of defense against over-discharge. First, all of the batteries I have seen for marine or RV use have a built-in battery management system (BMS) that automatically cuts the battery pack off if the overall pack voltage drops below some conservative value.

Our BMS cuts off our batteries at a minimum pack voltage of 11.3V (well above the 10.0V where damage would occur). If the overall voltage drops to 11.3, the system cuts the batteries off, preventing further discharge. When the BMS cuts off (and this is true for all the BMS cut-offs I describe below as well) The system lights up a red button installed in our panel. We would then diagnose and fix the problem, then press the button to reset the BMS - re-connecting the batteries. If the problem is not "fixed" pressing the button will not re-connect the batteries. To date, we have never had a BMS cutoff with our system.

Second, we program our Magnum inverter to shut off if the pack voltage drops to 11.4V (to help prevent us from ever hitting the 11.3V BMS cutoff). That way, any AC loads that might be drawing current via the inverter will be stopped before the battery hits the BMS cutoff line.

2. "Don't allow any cell to be charged at over the maximum voltage"

The maximum charge voltage is 3.65V per cell, which would be 14.6V for our array. Damage will not normally begin to occur unless charging at over 4.2V per cell for an extended period, so the "damage" threshold is around 16.8V for our pack.

There are several things we do to prevent over-voltage charging. First, the BMS is set to cut off the batteries any time the pack voltage exceeds 14.4V. So if any combination of chargers, alternators, etc - tries to drive the voltage above 14.4V, the BMS cuts off the batteries (well short of the 16.8 "damage" voltage and comfortably below the 14.6 maximum charge voltage.)

Second, we make sure that none of our charging sources will exceed the maximum voltage, because we don't want the BMS to ever go into over-voltage shut off. We charge via the engine alternator, the Magnum Inverter/Charger, and the solar controller. (The generator and shore power both charge via the Inverter/Charger).

Our engine alternator has a voltage regulator that keeps it below 14.2V. Unless the regulator fails, that should keep us below BMS cutoff voltage.

Our Magnum Inverter/Charger is programmed to charge at maximum current ("bulk" setting) up to a pack voltage of 14.0, then to switch to a constant-voltage charge ("absorb" setting) at 14.0V for a fixed period of time, then shut off ("float" setting) until the pack drops to a voltage of 13.3V. Obviously, this never allows our pack to be charged from Generator or Shore power at a voltage above 14.0.

Finally, our solar charge controller is set to charge at max current (which for solar isn't all that high), up to a pack voltage of 14.2V, then to switch to a constant-voltage 14.2 charge for a fixed period of time, or until the charge current drops below a minimum level. Then, the solar shuts off until the pack voltage drops down to 13.5V.

A couple of notes:
- As you may have noticed, stopping charge at 14.0V means our shore power never brings the pack to a full 100%.
- And, note that the solar has higher "stop" voltages and "start again" voltages than the shore power. This means that shore power will work until we are close to fully charged, then shore power cuts off and lets the "gentler" solar power finish the job. Later, when the voltage drops back after some use, the solar kicks in first - so if solar can handle the job alone, shore/generator power doesn't have to kick back in.
- If your system is set up for an "Equalize" charge (used for AGM and lead-acid batteries periodically to de-sulfate them.) It needs to be disabled. Don't confuse "Equalize" and "Balance". Lithium batteries do not require equlization. You don't want "Equalize" to kick in once per month or something and run the pack voltage up to ~15V-17V (which is the normal voltage range for "equalizing" AGM and lead-acid batteries.)

So, if we never charge the pack above the maximum pack voltage, we're all safe, right?

WRONG!

Now I'll talk about "balancing" as I mentioned above. Remember that we have four cells at 3.2V each wired in series to make 12.8V? What if ONE of those four cells drops low for some reason - to maybe 2.5V, but the rest are at the normal 3.2V. If we put a "seemingly safe" 14V charge on the whole pack, our poor little 2.5V cell isn't doing its job, so the other cells would be pushed up to over 3.8V each. That means the weak cell would cause the other three to exceed their 3.65 max charging voltage. And, over time, this effect could get worse and worse as the 3 "healthy" cells get more charge and the 1 "weak" cell gets consistently under-charged.

To prevent this, all lithium systems use "cell balancing" circuitry - which does two things: First, it slows down the charging of the highest voltage cells so that all the cells charge up together with equal voltages. Second, it sends an error to the BMS if a balancing failure is detected (meaning it was unable to balance the cells) which shuts down the whole pack.

In a modular system like ours, if one cell (of the 24 cells we have) fails and causes a balance failure, we could still remove that cell and the 3 "good" ones that are in series with it from the array, and we'd then have a fully working 500Ah battery pack (rather than the original 600Ah) as well as 3 "spare" cells. This makes for a very robust system with almost its own supply of spare parts.

3. "Don't allow any cell to be charged at over the maximum current"
The maximum charge CURRENT is usually stated as "C/1 up to 3.6V" which means that the maximum charge current is the amount that would equal the full capacity of the battery in one hour. ("Capacity divided by one") For our 600Ah pack, that means the maximum charge current would be 600A! (whoa!) Also, that means that the pack could be safely charged from zero-to-full in ONE HOUR!

That's just for "recommended" operation. The actual rating for our cells for "max charge current" is 200A per cell. Since we have 6 stacks of cells in parallel, the real "damage" threshold for our array would be a whopping 1200A!

Let's never do that! (Not even the 600A "recommended", even thought it's within spec and "safe")

We set a MUCH more conservative C/3 maximum charge current (one-third of capacity per hour) - which for our 600Ah pack would be 200A - allowing the pack to charge from zero to 100% in 3 hours.

Our Magnum Inverter/Charger has a maximum charge current of 125A, so no problem there with exceeding our 200A limit from generator or shore power.

Our (theoretical) 520W solar array would never (theoretically) exceed ~45A (520W at ~12V) so that's safe - even at the same time as the maximum 125A Inverter/Charger current. Also, we have never seen more than 30A with our solar system in the real world.

Our 150A engine alternator would not exceed our 200A limit, even with maximum solar at the same time. In practice, we've never seen more than 125A going from our engine alternator to the batteries, because the engine alternator is powering other loads at the same time.

The only combination that could exceed 200A would be if ALL 3 were at maximum at the same time - running the generator AND the engine AND the solar at high-noon in the Sahara... Then we'd be at 150 for the engine plus 125 for the Inverter/Charger plus 30 for the solar - That's just over 300A (which is still below even the 600A "recommended" max. Plus, the charging voltage required to achieve such a high current would automatically cut out both the Inverter/Charger AND the solar (because of the voltage ranges we put above) leaving only the engine alternator charging the batteries.

Whew! OK, I think we're safe.

Finally:
4. "Don't allow the battery to be exposed to excessive heat"

Don't take this to mean that lithium batteries are particularly heat sensitive. They actually do much better when hot than conventional lead-acid or AGM batteries. But, the life of the batteries is definitely most related to the temperature of the chemistry, so we want to avoid excessive heat.

Our batteries are installed in the engine room, so the ambient temperature is usually warm and fairly constant while underway. While that's not absolutely ideal, none of the temperatures in there are near what would damage the batteries.

The thing that WOULD damage the batteries is causing them to generate too much heat internally. When the batteries are fully charged, and more charge current is applied, the excess energy is dissipated as heat. That means you DO NOT want a "trickle" charge on lithium batteries when they are full. All of the "trickle" energy would act as a heater, constantly keeping your expensive batteries warmer than they should be.

As you may have noticed above, we avoid this by the way we program the various chargers - cutting off before the max "full" voltage of the lithium cells. Yes, that means that the batteries are theoretically never charged to 100% of their "chemistry" capacity. That's OK. Unlike conventional batteries, lithium batteries do not have to be regularly fully-charged. In fact, they are happier long term down in the middle of their voltage range. Most lithium manufacturers recommend 1/2 charge for "long term storage".

And, our "100%" capacity is really well below what the batteries are capable of. Quite a bit more energy could safely be stored there, but it would cause risk of premature failure. In the news recently, it appears that Samsung pushed their phone batteries too hard in their now-infamous "Note 7". We want to play it safe and get a lot of years out of our boat house batteries.

Another note on temperature - you should never charge lithium batteries if the temperature of the chemistry is below freezing. If your boat is stored out of the water, you need to be sure that nothing charges the batteries when the battery temp is likely to be below freezing, or you may want to put something like an aquarium heater pad under the batteries to keep them above freezing.

Below-freezing temperatures do not damage the batteries, but charging them when they are below freezing will cause damage.

Summary:
Overall, we tried to set up our system so that we were extremely conservative compared with the maximum/damage specs for the batteries, so that we have multiple lines of defense against problems, and so that we take into account likely component failures - without causing damage to the batteries themselves or safety issues.

We also had to be creative (with the help of a great manual from AM Solar) about setting up devices like the Inverter/Charger, the Solar Controller, and the Engine Alternator to charge lithium the right way, even though none of them have a "lithium" setting available. We are using the 3-stage "bulk", "absorb", and "float" settings (intended for AGM batteries) to get the desired behavior for our lithiums.
tfmkevin is offline   Reply With Quote
Old 10-13-2016, 05:28 PM   #34
Senior Member
 
jungpeter's Avatar
 
City: Everett
Country: US
Vessel Name: SPIRIT BEAR
Vessel Model: PACIFIC TRAWLER 40
Join Date: Mar 2013
Posts: 103
Hi TFMKEVIN,

Thanks for your article that appeared in your blog regarding your LiFePO4 battery installation. IMHO, your original blog post, and your subsequent responses to this forum, have nailed the issues in question.

Yup, there's less energy-consumptive ways to go boating than you have chosen. Using a solar shower to reduce energy use overnight, for instance. Personally, I'm with you-I don't need to practice bleeding before I go boating. Hot water, inside, on demand, sans generator, in the AM is VERY nice.

One energy user that you mention, that seems to be universally overlooked by those that boat in more urban environments is the need for on-board freezer space. IMHO, if you venture throughout the PNW, you need freezer space, both for the store-bought food, and subsistence living (crabs, prawns, fish, etc.) along the way. Freezers consume power, whether AC or DC. If you need freezer space, ya gotta pay the price. Mine is in the form of a ~$180 5.5 cu foot el-cheapo chest freezer from Lowes, running 110VAC via my inverter 24/7 (+/- its duty cycle) stored in my cockpit. Lucky me I have the room aboard. But luckier me I can fill it with fresh Halibut as well!

I've found it very difficult to determine absolute energy consumption figures on my boat (40' Pacific Trawler) for a couple of reasons. I've found that energy consumption is very much a function of environment, given that the duty cycle of almost all of my electrical "consumers" is variable day-to-day. Cold overnight? OK, so the freezer doesn't cycle so much, but perhaps my diesel heater is run more aggressively. Horseflies out? OK, freezer runs more often in the heat, but generator is running to allow use of HVAC; hence, generator easily covers the freezer deficit. Underway today? Maybe, maybe not. Depends on how I feel. Anchored up? Usually, unless I need/want to stretch my legs or re-provision in a town. And so forth. Your mileage definitely will vary by circumstance here. FYI, my boat uses two 260AH deep-cycle AGMs as a house bank, which (in general) requires ~3 hours of generator time, or ~4 hours of run time to keep near 80% topped up.

Kudos to you for recognizing that in YOUR case, with YOUR boat, and YOUR temperment/education/experience, YOUR solution works for you. Personally, I like my conveniences, and I'm willing to pay for them. I applaud you for your choices, and revealing them to others.

Regards,

Pete

ps-I was with the Roche Harbor YC gaggle that you met up with in Walker Cove last summer. Yeah, dropping the 14' Rendova upside down from the boat deck from one of our boats resulted in a real boat-rope. Nobody hurt (whew!!!) but did result in the loss of the outboard due to submersion. Poop.
jungpeter is offline   Reply With Quote
Old 10-13-2016, 09:18 PM   #35
Al
Guru
 
Al's Avatar
 
City: ketchikan, Alaska
Country: usa
Vessel Name: 'SLO'~BELLE
Vessel Model: Marben-27' Flybridge Trawler Pilothouse Pocket Cruiser[
Join Date: Apr 2012
Posts: 1,210
Quote:
Originally Posted by tfmkevin View Post

Summary:
Overall, we tried to set up our system so that we were extremely conservative compared with the maximum/damage specs for the batteries, so that we have multiple lines of defense against problems, and so that we take into account likely component failures - without causing damage to the batteries themselves or safety issues.
"Whow!!!! I have unleashed unlimited power by introducing your blog to the Forum. What a great asset and source you are becoming!!

Al-Ketchikan 27' Marben Pocket Cruiser
Al is online now   Reply With Quote
Old 10-13-2016, 10:30 PM   #36
Member
 
tfmkevin's Avatar
 
City: Portland, OR
Country: USA
Vessel Name: Airship
Vessel Model: 2013 Nordic Tug 34
Join Date: Sep 2014
Posts: 19
Quote:
Originally Posted by jungpeter View Post
Hi TFMKEVIN,

...

One energy user that you mention, that seems to be universally overlooked by those that boat in more urban environments is the need for on-board freezer space. IMHO, if you venture throughout the PNW, you need freezer space, both for the store-bought food, and subsistence living (crabs, prawns, fish, etc.) along the way. Freezers consume power, whether AC or DC. If you need freezer space, ya gotta pay the price. Mine is in the form of a ~$180 5.5 cu foot el-cheapo chest freezer from Lowes, running 110VAC via my inverter 24/7 (+/- its duty cycle) stored in my cockpit. Lucky me I have the room aboard. But luckier me I can fill it with fresh Halibut as well!
...

Regards,

Pete

ps-I was with the Roche Harbor YC gaggle that you met up with in Walker Cove last summer. Yeah, dropping the 14' Rendova upside down from the boat deck from one of our boats resulted in a real boat-rope. Nobody hurt (whew!!!) but did result in the loss of the outboard due to submersion. Poop.
Pete - VERY sorry about the dinghy incident. We were listening to that unfold on the radio as we left Walker Cove... Glad nobody was hurt!

You are absolutely correct about the freezer space issue! When you're cruising in BC or SE Alaska and there are often no stores for a week or more, you need freezer space, and freezers take considerable energy. We have a Frigibar 12V marine chest freezer on the top deck. It's efficient for a freezer, but still uses a fair amount of power. It was packed full almost our entire summer in Alaska (including some halibut, salmon, and crab we caught - as well as some BBQ we brought from home).

On a related note, I'm not so sure the "solar shower" option is even technically feasible for our region. You don't see a lot of solar showers in Alaska, and I suspect there is a reason...
tfmkevin is offline   Reply With Quote
Old 10-19-2016, 03:31 PM   #37
CMS
Veteran Member
 
City: Casco Bay
Country: USA
Join Date: Feb 2016
Posts: 63
Tfmkevin,

Good input. You have a good handle and realistic view on LFP.

Quote:
Originally Posted by tfmkevin View Post


- As you may have noticed, stopping charge at 14.0V means our shore power never brings the pack to a full 100%.


As you may have noticed above, we avoid this by the way we program the various chargers - cutting off before the max "full" voltage of the lithium cells. Yes, that means that the batteries are theoretically never charged to 100% of their "chemistry" capacity.
Be careful with thinking peak charge voltage defines SOC with LFP. Peak charge voltage does not really define 100% SOC. The lower the voltage limit the longer the CV stage is to 100% SOC and the less chance you will have of an imbalance throwing one cell into the danger zone but the battery can still attain 100% SOC at a lower peak charge voltage if the CV stage is held long enough. Problem is far too many LA charge sources are not programable and always like to hold a CV period.

A prismatic LFP cell can be charged to 100% SOC at 13.8V or 3.45VPC. If the CV duration period is kept short enough then no you won't over charge but if the voltage is in the 13.8V to 14.0V range and, the CV period held long enough, the batteries will become 100% full even if no cell ever approached the upper knee. I have an LFP bank in my shop right now that was destroyed by too long a CV period held at too high a voltage.

LFP is still very much a human assisted game with fractional C marine installations. For extended dockside use I suggest taking the LFP offline and leaving sitting at 50-60% SOC and bringing an LA battery on-line for shore side duration's.

Trying to fully automate LFP, while at the same time not floating, or keeping them at a high SOC regularly, is not something easily done with the lead acid charging technology we have today. Adapting LA charging devices to LFP is a sort of like Shrek trying to fit into Cinderella's glass slipper. His foot might cram in there but it's not really the best fit.

Below is a 100% discharge test at cycle #772. The bank is comprised of four 400Ah 2009 Thundersky/Winston cells in a 4S configuration. The pack was charged to 13.8V and current allowed to taper to 7.5A. As can be seen at a 30A load the pack delivers 432.1Ah. This after 772 cycles most of which went to 80% DOD. If I charge this same pack to 14.6V I get no more capacity out of it then I do here but I do run higher risk levels. For this video I used a camera intervalometer to capture voltage, current, time and Ah's removed on the discharger every 2 minutes.




" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350">
CMS is offline   Reply With Quote
Old 10-19-2016, 04:24 PM   #38
Guru
 
Bob Cofer's Avatar
 
City: Bellingham
Country: US
Vessel Name: Ebbtide
Vessel Model: '72 Grand Banks
Join Date: Aug 2013
Posts: 753
Kevin,

Awesome that you are a member! We will be Friday Harbor again this year for dinner at COHO and turkey on the dock, sure hope you guys can make it.

Bob & Jill
__________________
What kind of boat is that?
Bob Cofer is online now   Reply With Quote
Old 10-19-2016, 04:29 PM   #39
Member
 
tfmkevin's Avatar
 
City: Portland, OR
Country: USA
Vessel Name: Airship
Vessel Model: 2013 Nordic Tug 34
Join Date: Sep 2014
Posts: 19
CMS - great points!

Correct, voltage is not a good indicator of SoC - particularly on lithium with their very flat voltage curve.

The way we are set up to charge with our shore charger is:

"Bulk" charge until 14.0V.
Then - "Absorb" charge for 45 min at 14.0V
Then - "Float" - no charging (off)
Then - "Re-bulk" when pack voltage drops to 13.3V

This gives a pretty safe LFP profile using a conventional 3-stage charger. It doesn't keep the pack at 100% SoC. Most of the time connected to shore power the pack is sitting at a lower SoC with no charge applied.

It's not as good as keeping the pack at a "storage" SoC closer to 50%, but it's a decent compromise so you don't leave the dock with the tank half empty.
tfmkevin is offline   Reply With Quote
Old 10-19-2016, 05:00 PM   #40
CMS
Veteran Member
 
City: Casco Bay
Country: USA
Join Date: Feb 2016
Posts: 63
Quote:
Originally Posted by tfmkevin View Post
CMS - great points!

Correct, voltage is not a good indicator of SoC - particularly on lithium with their very flat voltage curve.

The way we are set up to charge with our shore charger is:

"Bulk" charge until 14.0V.
Then - "Absorb" charge for 45 min at 14.0V
Then - "Float" - no charging (off)
Then - "Re-bulk" when pack voltage drops to 13.3V

This gives a pretty safe LFP profile using a conventional 3-stage charger. It doesn't keep the pack at 100% SoC. Most of the time connected to shore power the pack is sitting at a lower SoC with no charge applied.

It's not as good as keeping the pack at a "storage" SoC closer to 50%, but it's a decent compromise so you don't leave the dock with the tank half empty.

I would much prefer to leave the dock at 50-60% SOC rather than continually re-bulking and re-absorbing an essentially full pack. 13.3V under load is only a few Ah's off 100%. Watch the video above on YouTube, make it larger, and you will see that 13.3V is extremely close to 100% SOC. A few tenths however means large differences in Ah capacity. You will note that the pack dips below 13.3V at -1.8Ah yet crosses the 50% SOC line at about 13.0V. I do not like stressing my pack by keeping it in the upper reaches. It is charged then discharged. If heading back to the mooring or a dock all charging is stopped, meaning physically turned off, at 50-60% SOC..
__________________

CMS is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 11:57 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012