Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rating: Thread Rating: 33 votes, 4.82 average. Display Modes
Old 16-09-2016, 20:29   #5371
Registered User

Join Date: Feb 2014
Location: Sydney
Posts: 196
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

lifepo4 kickstarter - http://www.kickstarter.com/projects/...it/description

What do people think?

I don't currently have a boat but expect to get a 40 foot cat as a liveaboard in the next 2 years. I am an industrial electrician and refrigeration mechanic. i will most definitely be looking for something to enable 8 hours of air con off battery.
__________________

__________________
Moonos is offline   Reply With Quote
Old 17-09-2016, 09:12   #5372
Registered User
 
toddedger's Avatar

Join Date: Mar 2012
Location: Michigan
Boat: Morgan 27
Posts: 192
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Personally I think solar charge control and BMS in the same box is a bad idea for boats.
__________________

__________________
toddedger is online now   Reply With Quote
Old 17-09-2016, 09:27   #5373
Registered User
 
NahanniV's Avatar

Join Date: Mar 2011
Location: On the Boat
Boat: Finnsailer 38
Posts: 1,027
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by toddedger View Post
Personally I think solar charge control and BMS in the same box is a bad idea for boats.
Do you have a particular reason ?
__________________
NahanniV is offline   Reply With Quote
Old 17-09-2016, 10:50   #5374
Registered User

Join Date: Jan 2011
Location: BC Canada
Boat: Marples 37
Posts: 46
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by toddedger View Post
Personally I think solar charge control and BMS in the same box is a bad idea for boats.
I'm not sure why this would be, I've often wondered why this hasn't been done before.

With LiPos need for no float charge it seems logical for the controller to bulk charge switch to absorb then when down to a set low amp flow switch off and reset the amp counter to 100%

If it's disconnecting the charge when full it would be taking the place of the BMS anyway.

Adding a low voltage disconnect would seem to cover all the possibilities.
__________________
CGirvan is offline   Reply With Quote
Old 17-09-2016, 11:10   #5375
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2014
Location: Anacortes
Boat: previous - Whitby 42 new - Goldenwave 44
Posts: 1,571
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Is there a reasonable way to filter out high voltage ripple from solar controllers? It would be nice if it were built in to a controller but with LA no so important.
__________________
exMaggieDrum is offline   Reply With Quote
Old 17-09-2016, 12:53   #5376
Registered User
 
toddedger's Avatar

Join Date: Mar 2012
Location: Michigan
Boat: Morgan 27
Posts: 192
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

The concept is to have charging sources self regulate and shut down at a certain voltage, and if they fail to do that the the BMS steps in as a safety factor. If you put it all in one box and it fails then what? I use separate solar controllers for each solar panel, if one panel gets shaded the others are still putting out full capacity. If one controller goes down it doesn't take the rest of the system down. I have a lot more faith in a controller made by a company with a track record of making controllers. I would not recommend using a newly designed controlle/BMS for a cabin in the woods let alone a boat sailing in the middle of nowhere, but that's just my personal opinion.
__________________
toddedger is online now   Reply With Quote
Old 20-09-2016, 18:00   #5377
Marine Service Provider
 
OceanSeaSpray's Avatar

Join Date: Aug 2013
Location: New Zealand
Boat: Custom 13m aluminium sloop
Posts: 361
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Merging BMS and charge management is what I have done. My BMS fully controls solar charging and it eliminated all of the crazy issues arising from trying to use so-called charge controllers that keep doing the opposite of what they should - like starting a new cycle every morning when the light comes up. I throw them out almost systematically now.

The only qualified piece of gear to make charging decisions in a LFP system is the BMS, because it should have access to current, cell voltages, SoC etc, unlike the wannabe charge controllers.
This doesn't mean that voltage regulation can't or shouldn't be implemented externally, which is not the same as charge control.

I don't see a conflict between protection and issuing charge control signals. The power is still switched/regulated outside the BMS and the protection function is independent.
In the case of solar, if the array is matched to the battery voltage, switching it in and out gives excellent performance and charge control capability.

It has been so successful that I am about to build the prototype for a second generation of the hardware and the key difference is a lot more and much smarter battery management capability, including and especially for charge/discharge control.
__________________
"The case for elimination: the only equipment that never needs maintenance and never breaks down is the one you don't have on board."
OceanSeaSpray is offline   Reply With Quote
Old 21-09-2016, 09:28   #5378
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2014
Location: Anacortes
Boat: previous - Whitby 42 new - Goldenwave 44
Posts: 1,571
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by OceanSeaSpray View Post
Merging BMS and charge management is what I have done. My BMS fully controls solar charging and it eliminated all of the crazy issues arising from trying to use so-called charge controllers that keep doing the opposite of what they should - like starting a new cycle every morning when the light comes up. I throw them out almost systematically now.

The only qualified piece of gear to make charging decisions in a LFP system is the BMS, because it should have access to current, cell voltages, SoC etc, unlike the wannabe charge controllers.
This doesn't mean that voltage regulation can't or shouldn't be implemented externally, which is not the same as charge control.

I don't see a conflict between protection and issuing charge control signals. The power is still switched/regulated outside the BMS and the protection function is independent.
In the case of solar, if the array is matched to the battery voltage, switching it in and out gives excellent performance and charge control capability.

It has been so successful that I am about to build the prototype for a second generation of the hardware and the key difference is a lot more and much smarter battery management capability, including and especially for charge/discharge control.
My plan, and hope, is to build out my total system as you state. Good points. Could not agree more about the separation of control and protection. Some have done away with the protection part and just rely on the control part. I don't feel that brave, as you do not. I have had too many problems with my own and customers various types of charge controllers to put full faith in them always behaving nice.
__________________
exMaggieDrum is offline   Reply With Quote
Old 21-09-2016, 09:44   #5379
Registered User

Join Date: Jan 2015
Location: Victoria BC
Boat: 1980 Hunter 36
Posts: 468
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Wouldn't having the BMS and charge controllers seperate give you more redundancy?

My plan is to have the charge controllers all programmed to stop charging at 3.5/14 and then have the HVC in the BMS set at 3.6/14.4 in case something goes wrong (with no auto balance)

This also allows me to have separate charge controllers for the different solar positions on the boat
__________________
S/V Gudgeon
www.gudgeonblog.ca
alctel is offline   Reply With Quote
Old 23-09-2016, 21:38   #5380
Registered User

Join Date: Jun 2010
Location: Easton, MD
Boat: Catalina 22 Capri
Posts: 692
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

There has been considerable discussion of the proper voltage to charge LiFePO4 batteries. The manufacturers say to charge at 3.65V per cell. That is probably fine as long as the cells are connected in parallel. That way none of the cells will exceed 3.65V. It would be nice to be able to easily charge them that way without having to rewire the battery. That would essentially balance the cells also. Any ideas?
__________________
kmacdonald is online now   Reply With Quote
Old 24-09-2016, 06:04   #5381
Commercial Member
 
CharlieJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: St. Petersburg, FL
Boat: Gulfstar Long Range Trawler; 53'; BearBoat
Posts: 815
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

3.65VPC will unnecessarily stress the LFP cells and will lead to premature failure. A better plan is to charge them to about 0.9C and then stop charging. For most cell manufacturers, 0.9C corresponds to a charging voltage of from 3.35VPC to 3.45VPC.

I highly recommend MaineSail's excellent blog: LiFePO4 Batteries - Thoughts & Musings Photo Gallery by Compass Marine How To at pbase.com
__________________
Charlie Johnson
JTB Marine Corporation
"The Devil is in the details and so is salvation."
CharlieJ is offline   Reply With Quote
Old 24-09-2016, 10:34   #5382
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2014
Location: Anacortes
Boat: previous - Whitby 42 new - Goldenwave 44
Posts: 1,571
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by kmacdonald View Post
There has been considerable discussion of the proper voltage to charge LiFePO4 batteries. The manufacturers say to charge at 3.65V per cell. That is probably fine as long as the cells are connected in parallel. That way none of the cells will exceed 3.65V. It would be nice to be able to easily charge them that way without having to rewire the battery. That would essentially balance the cells also. Any ideas?
My understanding is that 365v is the maximum charge voltage, not the best. It seems the consensus on here is that the best routine "full" charge voltage is much less than this. I am top balancing my new cells to 3.65v but I hope to not push them that high in service, ever. See other sources as noted.
__________________
exMaggieDrum is offline   Reply With Quote
Old 24-09-2016, 14:33   #5383
Marine Service Provider
 
OceanSeaSpray's Avatar

Join Date: Aug 2013
Location: New Zealand
Boat: Custom 13m aluminium sloop
Posts: 361
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by CharlieJ View Post
3.65VPC will unnecessarily stress the LFP cells and will lead to premature failure. A better plan is to charge them to about 0.9C and then stop charging. For most cell manufacturers, 0.9C corresponds to a charging voltage of from 3.35VPC to 3.45VPC.

I highly recommend MaineSail's excellent blog: LiFePO4 Batteries - Thoughts & Musings Photo Gallery by Compass Marine How To at pbase.com
It is a misconception to believe that SoC can be controlled using voltage. 3.4V will still charge a LFP cell to 100% given enough time and 3.3V will struggle to achieve 30% no matter what. The transition is so steep that it makes voltage unusable.



The data for the graph came from a published experiment by Powerstream, which I plotted in a different and much more interesting way some time ago while looking at the characteristics of LFP cells.

What would better control SoC is using the combination of end voltage and residual current, but since SLA charge controllers are completely unable to deal with it, all the LFP systems discussed here rely on a fragile balance between "settings" and a necessary consumption to try and work more or less acceptably most of the time.
This balance is easily upset if something changes, like leaving the boat for a time or going from summer to winter.

This is what quickly led me to moving away from using any kind of independent solar charge controller. I now have one control wire going from the BMS to a solid-state switch and no settings at all. Charging LFPs is in fact a part of battery management and this is ultimately inescapable.
__________________
"The case for elimination: the only equipment that never needs maintenance and never breaks down is the one you don't have on board."
OceanSeaSpray is offline   Reply With Quote
Old 26-09-2016, 11:28   #5384
Registered User
 
thomasow's Avatar

Join Date: Dec 2011
Location: Salish Sea & North
Boat: Monk/McQueen 45' - 1961 Trawler
Posts: 28
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

The concerns of voltage-only charge termination is not restricted to LFP deployments, FLA/SLA technology also presents several compromises when using voltage-only as a termination method, chiefly chronic undercharging. Traditionally charging sources would get around this via extending time-based charging cycles – relying on the battery to accept slight overcharging with minimal damage (perhaps increased water consumption in the case of FLA – SLA needs to be careful here). But of course LFP technology cannot do this.

Truth is, for most all battery technologies monitoring the acceptance amps in combination with voltage is truly one of the best way to reliable charge a battery w/o damaging it. It is why 3 years ago I developed the open source Alternator Regulator that includes current monitoring/regulation capabilities.

Which brings up another interesting topic: There is the question of ‘What to do about Float’ with FLP batteries. Many point to ‘Disable everything’, which is certainly in line with the common EV usage model of charge then discharge, but that usage pattern is not how house batteries are used. We do not often have the pure Charge and then Discharge states. Example: supporting a washer/dryer while underway via an inverter; is nice to let the alternator carry that load vs. depleting the ‘fully charged’ battery before we anchor for the evening.

Recently have been looking at active regulation of the battery current. Rather then a voltage set point for ‘float’ regulate instead to a current set point. Specifically 0A. So when the FLP battery reaches its fully charged state, we then manage the alternator to a 0A net current into/out of the battery – while still being able to support existing house loads. Of course voltage is still monitored, but it typically is well under the ‘recommended float voltage’. Early tests seem promising, and I am curious of others thoughts on this approach.
__________________
Viking Star
45' Monk Sr. / McQueen
mvVikingStar.blogspot.com
thomasow is offline   Reply With Quote
Old 26-09-2016, 11:55   #5385
Registered User

Join Date: Sep 2009
Location: Blue Hill, Maine
Boat: 32' Bob Baker/Joel White Cutter (One-off wood)
Posts: 154
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Regulating to 0A is an interesting idea. I imagine it would work better if the battery was only 95% charged. Harder to monitor charge acceptance on a full battery, perhaps? I do a similar thing by floating to 13.3V with our LiFePO4 bank. Not quite the same, but what my regulator is capable of and we rarely do long runs anyway.
__________________

__________________
marujo.sortudo is offline   Reply With Quote
Reply

Tags
battery, lifepo4, LiFePO4 Batteries, sailing

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
LiFePO4 Batteries - Okay Tear Me Apart ;-) jallum Electrical: Batteries, Generators & Solar 395 03-12-2015 13:19
Voltage drop under load, amps read 99% ?? VVD Electrical: Batteries, Generators & Solar 25 28-06-2011 16:25


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:54.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.