Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 22-10-2018, 20:21   #121
Registered User
 
rgleason's Avatar

Join Date: Mar 2012
Location: Boston, MA
Boat: 1981 Bristol 32 Sloop
Posts: 17,537
Images: 2
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

CatNewBee wrote:

Quote:
REC BMS a modular, pre-configured BMS, is not 500€. It is 205,00€ including one temp Sensor.

Cable set 25€
They can pre-set desired threshold values for shunt

Second temp sensor (optional) 6.50€.
Shipping (25€)

Taxes
Total 270...300€

Touch display 130€ - not necessary, but nice.
PC- Software plus Adapter cable (USB/Serial) adds 55€ not necessary,

empowers you to tweak all settings.

The complete system with software and shipping and without the display and shunt was around 320€, with display 440€, but ask them for a current price list.
Is the correct system the REC active BMS for 4 cells?

Is the PC with RS-485 used to view/set values and history? How often do you find it necessary? Is Canbus necessary? Good to have?


I see now from the wiring diagram, that two separate relays for charge and discharge are opened by the BMS.


Now I need to know what does Stop Charging (Regulator?)
and Stop Dishcharging? (BMS?)
rgleason is offline   Reply With Quote
Old 22-10-2018, 20:38   #122
Registered User

Join Date: Sep 2015
Posts: 445
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by Delfin View Post
I asked a similar question above regarding what seemed to be a divergence of opinion on whether balancing was necessary or desirable as a routine matter or not...
Sorry, I missed the question I think.

My opinion is that whether balancing is necessary is statistical in nature. It's 100% necessary if you want to charge up to the very tip-top of your pack's capacity for some reason.

Otherwise, it's necessary if you have a cell that behaves substantially differently than the others. We have evidence of lots of packs with no need to balance after years. Tesla's BMS only balances at the top, and tons of their drivers have data showing they don't even do one a "range charge" (= high SOC) to trigger balancing, either. It's obvious that lithium chemistries can behave well enough to not require it, at least for intervals that are so long that a manual intervention wouldn't be onerous once in a blue moon.

Now, is balancing desirable? That seems more subjective, and here I would argue that no house/ESS pack should want to have to rebalance, even if you already own a BMS that's capable of it. Obviously, we'd all prefer ideal cells that never need balancing. But, if we don't have those perfect ones, a very good second best is just to charge to a level that doesn't demand re-balance. That's good for other reasons, since we know that keeping batteries at very high SOC is not so great for them.

Others will argue that it's not a substantial enough lifecycle cost to justify not doing it, and they can make the case for having "the maximum" energy available.

But, personally, I would just oversize the battery by 5 or 10% and avoid the question entirely. Then no re-balancing is needed.

My 2c; you get what you pay for!
nebster is offline   Reply With Quote
Old 22-10-2018, 20:54   #123
cruiser

Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

That 5-10% is not even range of error for most House bank use cases.

Should be building in a lot more reserve capacity than that anyway for unpredictable scenarios.

If you hardly ever use it, the shallower cycling gives you greater cycle longevity anyway.
john61ct is offline   Reply With Quote
Old 22-10-2018, 21:11   #124
Registered User

Join Date: Sep 2015
Posts: 445
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by john61ct View Post
That 5-10% is not even range of error for most House bank use cases.
I don't know what that means, but I disagree anyway. See below.

Quote:
Should be building in a lot more reserve capacity than that anyway for unpredictable scenarios.
That's certainly a suggestion that might make sense in some cases, but it is not relevant with respect to my comments.

By the way, what kind of reserve capacity did you decide to build in for your pack?

Quote:
If you hardly ever use it, the shallower cycling gives you greater cycle longevity anyway.
It took you three sentences, but finally there is one that we can all agree with.


What I meant by over-provisioning 5 to 10% is:

1. Size your pack for your needs and desires. (Desired DOD, "reserve capacity", usable energy, etc.) Then,

2a. Use a standard top-rebalancing BMS.

OR

2b. Increase capacity another 5-10%, and no rebalancing will be necessary.
nebster is offline   Reply With Quote
Old 22-10-2018, 23:27   #125
Registered User
 
CatNewBee's Avatar

Join Date: Aug 2017
Boat: Lagoon 400S2
Posts: 3,755
Images: 3
Re: Revised Bank Regimen

Quote:
Originally Posted by rgleason View Post
CatNewBee preferred values
  • Start Balancing: 3,4V
  • OVP: 3,85V
  • UVP: 2,7V delayed for high loads
  • Acceptable difference: 0.02V (no balancing for small imbalances)
  • Balancing Current 3.5A (up to 15W per cell), there is a temp sensor on the board and a contact for a fan to cool the board if necessary.
Nope, this are not my preferred values, but the factory values pre-set in the Litrade one-board BMS for Winston cells.

One reason I was coughing up more money and buying the REC ABMS was the opportunity to set all voltages, thresholds, hysteresis settings etc. myself. I use other values.



My Solar controller is set during the summer to Absorption 14.3V; Float: 13.6V.
For Storage / when I leave the vessel for some time I use Solar settings Absorption 13.8V, FLOAT 13.4V

There is a difference of 0.1V on the measurement readings on the Victron smart solar to the BMS / Pack Voltage readings, so in fact all values are absolute : 14.2 (3.55V) / 13.5 (3.375V) in normal operation and 13.7 (3.425V) /13.3 (3.325V) in storage.

Most settings can be set on the UI (see picture), but there are more settings you can modify by the command line interface.

The settings for the charging thresholds are done on the chargers, not on the BMS, the BMS only manages to keep the cells equal and to disconnect if failures of other components occure.
Attached Thumbnails
Click image for larger version

Name:	REC-Settings.JPG
Views:	783
Size:	81.3 KB
ID:	179486  
CatNewBee is offline   Reply With Quote
Old 22-10-2018, 23:47   #126
Registered User
 
Delfin's Avatar

Join Date: Aug 2010
Location: Anacortes, WA
Boat: 55' Romsdal
Posts: 2,103
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by nebster View Post
Sorry, I missed the question I think.

My opinion is that whether balancing is necessary is statistical in nature. It's 100% necessary if you want to charge up to the very tip-top of your pack's capacity for some reason.

Otherwise, it's necessary if you have a cell that behaves substantially differently than the others. We have evidence of lots of packs with no need to balance after years. Tesla's BMS only balances at the top, and tons of their drivers have data showing they don't even do one a "range charge" (= high SOC) to trigger balancing, either. It's obvious that lithium chemistries can behave well enough to not require it, at least for intervals that are so long that a manual intervention wouldn't be onerous once in a blue moon.

Now, is balancing desirable? That seems more subjective, and here I would argue that no house/ESS pack should want to have to rebalance, even if you already own a BMS that's capable of it. Obviously, we'd all prefer ideal cells that never need balancing. But, if we don't have those perfect ones, a very good second best is just to charge to a level that doesn't demand re-balance. That's good for other reasons, since we know that keeping batteries at very high SOC is not so great for them.

Others will argue that it's not a substantial enough lifecycle cost to justify not doing it, and they can make the case for having "the maximum" energy available.

But, personally, I would just oversize the battery by 5 or 10% and avoid the question entirely. Then no re-balancing is needed.

My 2c; you get what you pay for!
That is very helpful, thank you.
Delfin is offline   Reply With Quote
Old 22-10-2018, 23:50   #127
Registered User
 
Delfin's Avatar

Join Date: Aug 2010
Location: Anacortes, WA
Boat: 55' Romsdal
Posts: 2,103
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by nebster View Post
I don't know what that means, but I disagree anyway. See below.



That's certainly a suggestion that might make sense in some cases, but it is not relevant with respect to my comments.

By the way, what kind of reserve capacity did you decide to build in for your pack?



It took you three sentences, but finally there is one that we can all agree with.


What I meant by over-provisioning 5 to 10% is:

1. Size your pack for your needs and desires. (Desired DOD, "reserve capacity", usable energy, etc.) Then,

2a. Use a standard top-rebalancing BMS.

OR

2b. Increase capacity another 5-10%, and no rebalancing will be necessary.
B was my choice, with the BMS as a failsafe.
Delfin is offline   Reply With Quote
Old 23-10-2018, 00:02   #128
Registered User
 
CatNewBee's Avatar

Join Date: Aug 2017
Boat: Lagoon 400S2
Posts: 3,755
Images: 3
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by rgleason View Post
CatNewBee wrote:


Is the correct system the REC active BMS for 4 cells?

Is the PC with RS-485 used to view/set values and history? How often do you find it necessary? Is Canbus necessary? Good to have?


I see now from the wiring diagram, that two separate relays for charge and discharge are opened by the BMS.


Now I need to know what does Stop Charging (Regulator?)
and Stop Dishcharging? (BMS?)
The PC interface RS-485 is only for tweaking the parameters, you can also use it for monitoring or even running command line commands to change hidden variables, like shunt configuration, reset / pre-set of counters, adjusting/calibrating shunt parameters, setting delta values for maximum acceptable cell voltage differences, setting thresholds for the second set of outputs (custom programming), checking what cells are currently balancing etc. There is a documentation what commands are possible and how to read the results. So you can integrate the system in your own monitoring if you want to.

Thje RS-485 is also used as Interface for the optional touch screen monitor and is automatically included in the cabling option, also the CAN bus interface and the temp sensors. The cabling is bult on your specification, so ask for a fully connected interface cable with the optional temp sensor (+6.50€) and all relay contacts / opto-couplers pre-wired!

CAN bus can be handy with the new REC firmware to integrate into Victron Inverter/charger or Victron GX interfaces as a third option beside the relay contacts and the opto-couplers. It was not ready / tested as I buld my system, but I know other customer to appreciate this interface. It is included and pre-wired, so no additional costs.

The relays are opened and closed by the BMS, there are 2 relays with three isolated contacts each, one is the common contact and then there is a NC / NO contact per relay, so it switches from common-NC to common-NO to allow charging (respective discharging on the other relay) and from common-NO to common-NC do stop charging (respective drop loads).

The opto-couplers are open on stop charging/stop loads, and closed when charging / loads ere enabled. The BMS does a test on startup on the interfaces and enables them after the boot process.

As described before this relays / opto-coupler and CAN signals are like fuses and engage only if other system fail.

Charging and discharging is controlled by the charge controllers and the onboard monitoring systems based on whatever parameters they have if available. Each charger has its own charge profile. I have added a Victron BMVto allow unregulated sources charge the LFP bank at preset SOC ranges, so this is an example for an additional regulator.

I also use the opto-coupler outputs to control the Victron Quattro with different settings than the OVP / UVP signals, because it is a combi-device and is both a charge source and a load. I do disable the inverter earlier than the protection level of the BMS, so I do have 200Ah capacity left for board electronics when the inverter is disabled by the BMS, what allows me to comfortably sail at night with running fridges and all stuff until next day the solar re-charges. But this is my personal setting.

You can do the same by using the CAN interface.

And I disagree, that balancing is not necessary. Unbalanced cells cannot be safely used with gear that regulates on battery voltage.
It is essential for a healthy and long lasting battery to keep the cells balanced. But it is your money, some prefer to learn the hard way.

Most LFP installation do not fail because of charging to high SOC, but because of unbalanced cells that run away.
CatNewBee is offline   Reply With Quote
Old 23-10-2018, 05:57   #129
cruiser

Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by nebster View Post
Increase capacity another 5-10%, and no rebalancing will be necessary.
Yes we do agree on that.

My point is that capacity sizing isn't that precise, the bank should already be sized so that the user is rarely going below say 20%, or even 40%, in some use cases 60% anyway.

For example mostly-solar, very variable conditions, I size for 3-4 days usage. If the owner does not mind using ICE charging when needed, that may be 2-3 days instead.

In which case the extra 5-10% is unneeded.

In the opposite scenario, ICE charging is convenient or frequently running for other purposes anyway, then bank size really doesn't matter, plenty power always at hand and SoC never need drop that low.
john61ct is offline   Reply With Quote
Old 23-10-2018, 10:50   #130
Registered User

Join Date: Feb 2015
Posts: 1,225
Images: 1
Re: Revised Bank Regimen

Quote:
Originally Posted by CatNewBee View Post
Nope, this are not my preferred values, but the factory values pre-set in the Litrade one-board BMS for Winston cells.

One reason I was coughing up more money and buying the REC ABMS was the opportunity to set all voltages, thresholds, hysteresis settings etc. myself. I use other values.



My Solar controller is set during the summer to Absorption 14.3V; Float: 13.6V.
For Storage / when I leave the vessel for some time I use Solar settings Absorption 13.8V, FLOAT 13.4V

There is a difference of 0.1V on the measurement readings on the Victron smart solar to the BMS / Pack Voltage readings, so in fact all values are absolute : 14.2 (3.55V) / 13.5 (3.375V) in normal operation and 13.7 (3.425V) /13.3 (3.325V) in storage.

Most settings can be set on the UI (see picture), but there are more settings you can modify by the command line interface.

The settings for the charging thresholds are done on the chargers, not on the BMS, the BMS only manages to keep the cells equal and to disconnect if failures of other components occure.

That's a very comprehensive BMS. What's the rough cost?
__________________
www.MVTanglewood.com
tanglewood is offline   Reply With Quote
Old 23-10-2018, 11:22   #131
cruiser

Join Date: Feb 2012
Location: Half Moon Bay, CA, USA
Boat: 1963 Pearson Ariel, Hull 75
Posts: 1,111
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by john61ct View Post
Yes we do agree on that.

My point is that capacity sizing isn't that precise, the bank should already be sized so that the user is rarely going below say 20%, or even 40%, in some use cases 60% anyway.

For example mostly-solar, very variable conditions, I size for 3-4 days usage. If the owner does not mind using ICE charging when needed, that may be 2-3 days instead.

In which case the extra 5-10% is unneeded.

In the opposite scenario, ICE charging is convenient or frequently running for other purposes anyway, then bank size really doesn't matter, plenty power always at hand and SoC never need drop that low.
I agree. Much of the complexity of lithium technology is intended for squeezing that last AH out of the battery, at the expense of reduced battery life and dependence on complex BMS systems (that are still evolving). It's appropriate for electric vehicles. That complexity is unnecessary for partial SOC charge/discharge applications. It's still good practice to use only about 50% of a lithium's capacity, just like you've done with lead acid batteries. You still get all the advantages of lithium, with less weight.
Cpt Pat is offline   Reply With Quote
Old 23-10-2018, 11:44   #132
cruiser

Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by Cpt Pat View Post
It's still good practice to use only about 50% of a lithium's capacity, just like you've done with lead acid batteries. You still get all the advantages of lithium, with less weight.
You aren't wrong, but that might be overstating it a bit - we get controversy over this even wrt lead too!

LFP being **such** a bigger up-front investment, people really don't want to "oversize" any more than needed.

And how much that is varies from case to case.

> Much of the complexity of lithium technology is intended for squeezing that last AH out of the battery, at the expense of reduced battery life and dependence on complex BMS systems (that are still evolving). It's appropriate for electric vehicles. That complexity is unnecessary for partial SOC charge/discharge applications.

Absolutely, the dominance of military and EV usage needs is really what drives the industry and its "standards" which often are just not relevant for gentle House cycling.
john61ct is offline   Reply With Quote
Old 23-10-2018, 12:05   #133
Registered User
 
CatNewBee's Avatar

Join Date: Aug 2017
Boat: Lagoon 400S2
Posts: 3,755
Images: 3
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

I am not wondering, that many DIY LFP fail.

It is ignorance paired with saving on the wrong end and a overestimation of the own ability to monitor a battery systems manualy.

It did not work with less comlex FLA and will definitely fail with LFP. Maybe not in the first year, maybe not in the second...

But good luck! The second battery will be properly protected.
__________________
Lagoon 400S2 refit for cruising: LiFeYPO4, solar and electric galley...
CatNewBee is offline   Reply With Quote
Old 23-10-2018, 12:11   #134
Registered User
 
CatNewBee's Avatar

Join Date: Aug 2017
Boat: Lagoon 400S2
Posts: 3,755
Images: 3
Re: Revised Bank Regimen

Quote:
Originally Posted by tanglewood View Post
That's a very comprehensive BMS. What's the rough cost?
It depends on the components you need.
Just look some posts back, there I have stated all the prices for the components.

I have the whole shebang with second temp sensor, software and display around 500€ including shipping and taxes, but the core is just around 220€ factory pre-set to your desired parameters.

You also probably need the solenoids, that are the most expensive parts, but you"ll need them anyway.
__________________
Lagoon 400S2 refit for cruising: LiFeYPO4, solar and electric galley...
CatNewBee is offline   Reply With Quote
Old 23-10-2018, 13:43   #135
Registered User

Join Date: Sep 2015
Posts: 445
Re: Good thesis on preserving the life of LiFePo4 lithium batteries

Quote:
Originally Posted by CatNewBee View Post
It is essential for a healthy and long lasting battery to keep the cells balanced.
We have direct evidence of numerous packs that stay healthy over a long period without any additional balancing after commissioning.

So, you can disagree, but your premise is wrong.
nebster is offline   Reply With Quote
Reply

Tags
lifepo4

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Lithium Werks merges Valance Batteries and Super B Batteries BigBeakie Lithium Power Systems 0 03-09-2018 06:42
For Sale: Sinopoly LifePo4 Lithium Ion Batteries 200AH SVFairIsle General Classifieds (no boats) 15 16-02-2018 14:25
Tesla Doubles Life Span of Lithium Batteries zboss Electrical: Batteries, Generators & Solar 1 14-05-2017 02:19
Monitoring LiFePO4 Lithium Batteries sparrowhawk1 Electrical: Batteries, Generators & Solar 80 30-04-2015 17:56
liFePO4 lithium as house batteries sparrowhawk1 Electrical: Batteries, Generators & Solar 11 01-02-2014 12:22

Advertise Here


All times are GMT -7. The time now is 08:25.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.