Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 12-09-2013, 15:49   #316
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,019
Quote:
Originally Posted by vRUN View Post
READ AGAIN!
Think about when the relay will be closed. The diode is not in circuit then. Relay can be closed when battery is charging, when charger is off and when charger cannot maintain house voltage. Most of the time the diode is not conducting.

Also, read up on Schottky diodes. Much less drop than regular silicon.
__________________

__________________
transmitterdan is offline   Reply With Quote
Old 12-09-2013, 16:07   #317
Registered User

Join Date: May 2013
Posts: 59
Re: Lithium Batteries (for the rest of us)

Quote:
Originally Posted by dlentz View Post
There is NO diode involved. (Your assumption). ...
Anyway I'm with Lagoon , my fridge is happily working away, while I'm away. Simple.
Dwain
Enjoy your beer
...draw your circuit until monday
__________________

__________________
vRUN is offline   Reply With Quote
Old 12-09-2013, 16:10   #318
Registered User

Join Date: May 2013
Posts: 59
Re: Lithium Batteries (for the rest of us)

Quote:
Originally Posted by transmitterdan View Post
Also, read up on Schottky diodes.
If you make proposals like that be reminded that it always pays off if you:
Click on things that appear blue

I'm out
__________________
vRUN is offline   Reply With Quote
Old 12-09-2013, 16:15   #319
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,019
Re: Lithium Batteries (for the rest of us)

Quote:
Originally Posted by Lagoon4us View Post
Once again a thread has become way too technical and somewhat argumentative, i'm enjoying the beer cooled by my fridge, powered by our simplistic Lithium cell arrangement, charged by the sun, goodnight Zeus and thank you.......What would i know?
Cheers all.
I wish LI wasn't technical but unfortunately it is to some extent and that either interests someone or it doesn't. I'm sorry that I may have annoyed you. It was not my or anyone else's intention I'm sure.

I don't think anyone is suggesting that you are doing something wrong. But not everyone can install LI as you have done. Many (most?) boaters leave their boats plugged in at the dock for extended periods and/or they have multiple sources of charging 24/7. Some would argue that the typical boater doesn't really need LI batteries and they might be right. But LI has many advantages over LA. Unfortunately 90%+ don't warm up to the idea of replacing their alternators and existing charger/inverter systems or having to "watch" their batteries like a hawk. If LI had a reasonably priced (i.e. low tech) plug-n-play installation that worked with existing charge sources the adoption rate would go up orders of magnitude. Prices might fall and everyone would be better off.

I believe you and others have proved in this thread that constant or even periodic maintenance balancing is not required. That's a big deal in my view. This discussion has pretty much convinced me that it might be easier than many think for LI to meet the needs of 90%+ of full time and weekend cruisers. A "simple" device that inserts between the charge bus and the battery that easily handled multiple conventional charging sources might get traction among many more boaters. I think discussions that could lead to mainstreaming LI is the original intent of this thread and a good thing.
__________________
transmitterdan is offline   Reply With Quote
Old 12-09-2013, 17:10   #320
Registered User
 
deckofficer's Avatar

Join Date: Feb 2011
Location: Northern and Southern California
Boat: too many
Posts: 4,198
Images: 4
Re: Lithium Batteries (for the rest of us)

I think I'm on the verge of learning something new that will correct possible false impressions I have with our LiFePO4 cells. Wouldn't be the first time that the expertise on this forum has straightened me out. Heck, Bill has straightened me out a lot on HF antennas and signal propagation.

Here is what I "think" I know, so experts chime in and correct me.

1.) I don't think it was by accident that our cell's nominal voltage is 3.25. I would think that chemistry tweaks could move the nominal voltage up or down for a small range. A fully charged LA 12 volt battery will show a voltage of 12.95 volts. 4 X 3.25 = 13.00 volts. So, other than charge acceptance rates being higher for LiFePO4, forcing us to beef up our alternators, charge cables, regulators, what changes do we need for our charging sources?

2.) Over voltage (above 4.0) and under voltage (below 2.8) is the only factors of concern for long cycle life in our sub 1C useage. Cells being out of balance would only be a concern if any cell goes too high during charge or too low during discharge.

3.) Because of 1 and 2 above, I think our cells are close to drop in replacements for LA, am I wrong in this assumption?
__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
http://tbuckets.lefora.com/
deckofficer is offline   Reply With Quote
Old 12-09-2013, 18:14   #321
Marine Service Provider
 
OceanSeaSpray's Avatar

Join Date: Aug 2013
Location: New Zealand
Boat: Custom 13m aluminium sloop
Posts: 414
Re: Lithium Batteries (for the rest of us)

Power path considerations are not a substitute for stopping charging, it still need to be done regardless, so the point is not all that relevant.
In order for a cell to charge, the voltage supplied must exceed the open circuit voltage of the cell + the polarisation voltage, so arguably any system that "floats" lower than the open circuit voltage of the bank effectively switches off charging. 100% SOC for most LiFePO4 cells seems to mean about 3.42V/cell, this is at rest and left disconnected for an hour or so.

Power path comes into play when you want to use external power without drawing onto the battery, i.e. laptop plugged in. There is a range of problems trying to do this on board, first because solar sources are not voltage regulated and alternator sources would get disconnected when loads are switched off. It is not really practical. You would find 21VDC on the power path output at times etc.

Manufacturers seem to recommend 50-60% SOC for long-term storage, so this suggests "floating" the bank down to a low reconnect voltage. The only challenge is making sure that the controller will indeed leave the bank alone for weeks, and not start a cycle every morning for example in the case of a solar system. Then it would just self-discharge at some 3%/month until the time comes to recharge and the strategy would basically minimise cycling.
It also means there would be a need to get out of that "maintenance" mode when the boat is going to be used again.
__________________
OceanSeaSpray is offline   Reply With Quote
Old 12-09-2013, 18:34   #322
Marine Service Provider
 
OceanSeaSpray's Avatar

Join Date: Aug 2013
Location: New Zealand
Boat: Custom 13m aluminium sloop
Posts: 414
Re: Lithium Batteries (for the rest of us)

A little while ago I mentioned the idea of creating a simple BMS board and I did some work in this direction. I have now designed the circuit, the board measures 163x80mm at the moment. It targets 4-cell systems.

I am still working on some aspects like reducing component count, housing etc, but the functional specification is detailed below.
Functional Specification

Inputs

4 independent differential voltage inputs for monitoring of cell voltages, 2 wires per cell.
2 independent temperature inputs for monitoring cell temperatures, one sensor sandwiched between each pair of cells.
Up to 3 independent power supply inputs available for the control board.
Outputs

Alternator control/charge disable solid-state contact. Interrupts any +12V supply provided, 6-10A capacity
External alarm. Solid-state contact closing a circuit to ground in case of alarm condition.
Load disconnect solid state switch, on-board switch capacity configurable between 10 and 90A depending on hardware installed.
Functions

Over-Voltage Protection

Any cell exceeding a voltage threshold adjustable between 3.36V and 4.25V disables charging, automatically re-enabled once maximum cell voltage has dropped by at least 0.2V.
Under-Voltage Protection / Load Disconnect

Any cell reaching a low voltage threshold adjustable between 1.82V and 2.48V triggers a load disconnect, automatically reconnecting once cell voltage has increased by 1V or more.
Low Voltage Alarm

Any cell reaching a low voltage threshold adjustable between 2.42V and 3.08V triggers a low voltage alarm, automatically resetting once cell voltage has increased by 0.1V or more.
Cell Short Circuit Protection

Any cell reaching a low voltage threshold of 1.37V disables charging, automatically re-enabled once minimum cell voltage has risen to at least 1.86V.
Cell High-Temperature Protection

Any temperature sensor reading above a high temperature threshold adjustable between 36˚C and 66˚C (97˚F and 151˚F) disables charging, automatically re-enabled once maximum cell voltage has dropped by 6˚C at 50˚C (11˚F at 122˚F), delta increases with temperature.
Temperature Sensor Break Detection

Sensor break results in a visual indication. Sensor short circuit causes a high-temperature alarm.
Display

8 status LEDs, intermittent flash for reduced power consumption.
1. Cell over-voltage
2. Cell low voltage alarm
3. Cell under-voltage load disconnect
4. Cell short-circuit
5. Cell high temperature
6. Charge disable (in parallel with alarm condition)
7. Temperature sensor break
8. Active (power on)
Alarm Conditions

· Cell over-voltage
· Cell low voltage (before load disconnect)
· Cell high temperature
On-board alarming through piezo buzzer, cuts out with load disconnect. Behaviour of external alarm devices connected to alarm contact output depends on where they are fed from.
Failure Modes

Monitoring Board Power Failure

Charge enabled, load disconnected.
Supply Reverse Polarity

Protected.
Supply Overvoltage

Fuse blow above 18VDC input voltage.
Charge Control Output Overload

Fused to disable charging.
External Alarm Output Overload

Fused.
Load Disconnect Switch

Unfused. Connected loads shall be protected externally.
__________________
OceanSeaSpray is offline   Reply With Quote
Old 12-09-2013, 19:48   #323
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
OceanSea,

Looks like you have been busy!

I considered a custom board around some IC's, but being a technician not a EE designing circuit boards was a limiting factor. Plus there was the problem of needing to sell a hundred or so to make the production costs worthwhile if I figured out the PCB design, got the board produced, debugged it and then figured out who could produce the finished product with components.

The DIY market at the moment has the "House Power BMS", the Junsi logger and not much else. Both are good products, but limited in customizability and functionality. One is designed for the RC market and hard to even call a BMS, but it will perform that function if properly configured and tested.

I sent my email via private mail. Be happy to talk specifics there, or on a thread for us bit heads....

Bob
__________________
ebaugh is offline   Reply With Quote
Old 12-09-2013, 19:48   #324
Registered User
 
familycruisers's Avatar

Join Date: Aug 2011
Location: On the boat
Boat: Westerly Centaur. 26'
Posts: 500
Send a message via Skype™ to familycruisers
Re: Lithium Batteries (for the rest of us)

Question, my spec sheet says max charge voltage 3.65 , nominal 3.2 and max discharge 2.5
Wouldn't that mean charging to 14.6v ?(potentially if you can monitor individual cell voltages) , 12.8 being nominal, and 10 v being dead pack
__________________
familycruisers is offline   Reply With Quote
Old 12-09-2013, 20:32   #325
Registered User
 
7h3gr1ng0's Avatar

Join Date: Sep 2013
Location: Canada presently, but considering other options.
Boat: Something seaworthy but haven't decided yet.
Posts: 12
Re: Lithium Batteries (for the rest of us)

Of possible relevance and interest in relation to this thread...

LiFePo4 may be the latest in battery technology, however, if you are looking for longevity, and a battery that will tolerate “abuse”, it is not necessarily the best. In 1901, Thomas Edison had developed a battery for use in the first automobiles, which in fact were electric at the time. Although only in it's early stages of development, the chemistry of his revolutionary new battery was, and is, superior to anything that is widely marketed as a deep cycle battery today.

The Edison Storage Battery Company manufactured and sold these American made batteries up until 1975. In 1972, Exide Battery corporation bought the company and stopped production of Edison's battery only a few years later. But I hear they're making a come back. The chemistry was, and is; Nickel Iron (NiFe). nickel iron battery information
__________________
7h3gr1ng0 is offline   Reply With Quote
Old 13-09-2013, 04:35   #326
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Re: Lithium Batteries (for the rest of us)

Quote:
Originally Posted by ebaugh View Post
Dave,

Is the attached what you are suggesting?
Yes in a simplistic way
__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Old 13-09-2013, 04:39   #327
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
Quote:
Originally Posted by 7h3gr1ng0 View Post
Of possible relevance and interest in relation to this thread...

LiFePo4 may be the latest in battery technology, however, if you are looking for longevity, and a battery that will tolerate “abuse”, it is not necessarily the best. In 1901, Thomas Edison had developed a battery for use in the first automobiles, which in fact were electric at the time. Although only in it's early stages of development, the chemistry of his revolutionary new battery was, and is, superior to anything that is widely marketed as a deep cycle battery today.

The Edison Storage Battery Company manufactured and sold these American made batteries up until 1975. In 1972, Exide Battery corporation bought the company and stopped production of Edison's battery only a few years later. But I hear they're making a come back. The chemistry was, and is; Nickel Iron (NiFe). nickel iron battery information
Interesting. The Chinese manufacturer of those cells provides quite a bit of data. It looked like it would take a minimum 3000 Ah bank to power an inverter at 1500 watts. But if kept at 20 degrees C, it would do it a long time.
__________________
ebaugh is offline   Reply With Quote
Old 13-09-2013, 04:41   #328
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
Quote:
Originally Posted by goboatingnow View Post

Yes in a simplistic way
I'm a simple guy...just wanted to make sure I had the concept.
__________________
ebaugh is offline   Reply With Quote
Old 13-09-2013, 04:56   #329
Marine Service Provider
 
Maine Sail's Avatar

Join Date: Jan 2007
Location: Maine
Boat: CS-36T - Cupecoy
Posts: 3,060
Re: Lithium Batteries (for the rest of us)

Quote:
Originally Posted by familycruisers View Post
Question, my spec sheet says max charge voltage 3.65 , nominal 3.2 and max discharge 2.5
Wouldn't that mean charging to 14.6v ?(potentially if you can monitor individual cell voltages) , 12.8 being nominal, and 10 v being dead pack

We have no idea what cells you have but here's my guess.. 3.65V is likely your absolute max charge voltage and into the upper knee. It likely leaves no room for error...

My cells say max 4.0V on the Chinese spec sheet but the manufacturer advised absolutely no higher than 3.8VPC. I was also advised that 3.8V was only ever to be used for closely monitored top balancing or severe shortening of cycle life could occur..

In daily use we charge to 13.8V / 3.45VPC and this leaves a safety margin and some room for error or some top end room for a cell imbalance.... 13.8V to 5A or less of accepted current gets us to within +/- 10Ah of absolute chuck full... I will give up that 7-10Ah of capacity to stay out of the danger zone any day of the week....
__________________
Marine How To Articles
Maine Sail is offline   Reply With Quote
Old 13-09-2013, 05:26   #330
Nearly an old salt
 
goboatingnow's Avatar

Cruisers Forum Supporter

Join Date: Jun 2009
Posts: 13,649
Images: 3
Re: Lithium Batteries (for the rest of us)

WHat we must be very careful in evaluating LI large prismatics i.e. the

" dude my beer is cold the system works" pseudo science. ( with apologies to whoever said that type of thing).

Firstly we have very little reliable data on the life cycle of large prismatic Li formats, hell we are only building up data on small format Li as it is. The EE industry is replete with Li issues, most of which resulted in unexpected premature cell death

heres a amatuer blog KA7OEI's blog: Problems with Lithium Iron Phosphate (LiFePO4) Batteries

etc etc

One only has to follow the progression in IC Li charge controllers to see the way the thinking has changed in a relatively short time.

It will be a sorry person , whose "beer' isnt "cold" in two years time and down a $5000 investment.


So lets review what the industry ( small Li charging) is saying and doing for best practice (its an area I actively design in). This is current best practice and of course you may not be able to implement that and the consequences may or may not be obvious .

Nor am I trying to frighten people off, I personally think Li is great . Ive just finished two designs with them in it.

So to summarise

1. Voltage stress is a key factor in determining reliable life and capacity , you pick you charge cut-off appropriately . HVC and LVC also are needed to avoid damage.

2. Float charging or maintenance charging is not regarded as a good idea, The theory seems to suggest that maintaining any electrical field , cause Ion movement and in effect "works the battery". Chargers should be disconnected after charge cutoff has been reached. Dont make the mistake of analysing Li in La(Pb) terms , very very different process at work.

3. The charger reengagement point ( ie the voltage where the charger reconnects) seems to be a hotly debated point. Some bring the charger in at about 80% of cuttoff, others try to ensure the battery does a full or near full discharge.

4. "mini-cycles" causes problems as they use up the expected life cycles to some or greater extent. Mini cycles are typically caused in load sharing environments or where , the battery is effectively under constant demand and recharging occurs very regularly ( like in solar charging) .

5. Temperature plays and important part in Li life. extremes cause lower life, below freezing is very problematic

6. Load sharing causes mini cycles, which reduces life times, especially where high peak , short duration currents are being supplied by the battery in a load sharing situation. The battery should if possible be isolated from the power source in that the power source should not cause charging to occur.


NOW, lets look at what we got in terms of existing boat charging sources and examine the issues

1. Smart LA orientated chargers, also used as a power source.

In my mind this is the biggest culprit as its often the source that is left active for long periods. Most people in marinas have teh battery on 24/7 with it supplying the boats loads in parallel to the battery.

Without modifications, a 3 stage charger is quite unsuited to Li charging.

Most chargers when the boat is being used are load sharing with typically more then float voltages being applied, this is causing mini cycles, we can only wait and see what effect it has on life cycles.

Ebaugh , I believe saw 15% reduction in capacity after 1 year, That if continued could change the cost equations.

2.Solar

AGain this is a problematic method of charging Li, As my definition it tends to be connected for long periods, dropping in and out of the circuit. Theres no easy answer to solar and Li

3. Genny, ALternators etc,

Much less of an issue as they tend to used solely as a recharger and then shut down. good match for Li. ( assuming cutoffs appropriate etc).


Does that mean a system today with standard chargers, solars and Alernators can be made to work, yes, is it optimum , no , what will the effect be, Time will tell. ( but it might be an expensive lesson)


My own view , is that Li should be justified for its recharge,discharge , storage and use reasons, BUT not on life times. Justifying the cost because based on flimsy data that suggests you'll get 10 years or something , given our state of knowledge and the less then optimum usage environment is very silly

ie , dont justify Li on cost with the present state of knowledge.

After that YMMV.

enjoy the cold ones.

Dave
__________________

__________________
Check out my new blog on smart boat technology, networking and gadgets for the connected sailor! - http://smartboats.tumblr.com
goboatingnow is offline   Reply With Quote
Reply

Tags
paracelle

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
I Only Have Two Batteries - Which Batteries Should I Use? LifesAnAdventure Electrical: Batteries, Generators & Solar 11 04-06-2014 19:29
Eliminating a Battery Isolator R_C Electrical: Batteries, Generators & Solar 21 19-09-2013 03:42
Lithium Batteries in Handheld VHF Sets Dockhead Marine Electronics 10 26-10-2011 21:52
Killed Batteries ? Dockhead Electrical: Batteries, Generators & Solar 31 27-08-2011 05:14
Voltage drop under load, amps read 99% ?? VVD Electrical: Batteries, Generators & Solar 25 28-06-2011 16:25



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 08:48.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.