LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[PacificGreen]

Originally Posted by roetter

Hi PacificGreen
Not a big loss but I realize how bad lead acid batteries are when you draw a lot of power. I will go back to Lithium in time.

Wow. What a project on your boat. Besides the 48V bank do you have a small 12V bank for all the small stuff? I would need to drive electric winches and the windlass on 12V plus the usual small stuff with it. I guess small 12V Lithium battery could do that if you have a good DC-DC charger.

I use a 120v to 12v 15amp converter to power all of the 12v. I have also a 12v battery charger that I can use to charge a 12v battery say for the 9.9 yamaha if that gets run down.

[PacificGreen]

Originally Posted by autumnbreeze27

4 x 400ah batteries. Here's a pic. It's always bugged me that I didn't know any tech details of the BMS. Will see what I can look up on miniBMS.

Here I found the documentation in the attachment called the HiQap BMS which still appears to be when I inspected it mostly a miniBMS system with the addition of what they call a BMU board that controls the contactor relay and checks and rechecks voltages of cells to avoid disconnects when at all possible.

I had initially thought it would be simialar to the QanBuSS system and might have a display of sorts but I ground out trying to figure out how to make that happen with CAN hi lo pins.

Mine came at 48v and I had a separate enclosure for the relays as in the attachement. Here it did arrive with the minibms board potted in black. Under the cage I found the BMU and examined it on a number of occasions.

[OceanSeaSpray]

Originally Posted by bill good

Tested a couple of days ago @ 75% SOC all 12 cells max difference 0.001V (3.289V). Pretty good for the time in service.

Spectacularly meaningless. For the N-th time, there is no point whatsoever in comparing cell voltages on the flat of the SOC curve. They always read "within 1mV".
If you want to get an idea of cell balance, charge to full and measure at the end of the charge cycle when the voltage is at least 3.5V/cell and the current is way down. Then you will see differences.

A guy called last week, no BMS, battery at 14.0V, one cell at 3.83V! He was also telling me a while ago how beautifully balanced his cells always were... in the mid-range.
Problems only show once the cells are getting near-fully absorbed.

Also 75% SOC and 3.289V simply don't compute at all... that would be more like 40% SOC if your voltage is accurate.

[SV THIRD DAY]

Originally Posted by OceanSeaSpray

If you want to get an idea of cell balance, charge to full and measure at the end of the charge cycle when the voltage is at least 3.5V/cell and the current is way down.

Problems only show once the cells are getting near-fully absorbed.

For the N-time...why would someone take their LiFePO4 batteries to near-fully absorbed anyway.

Sound like old school Lead Acid thinking to me....

[OceanSeaSpray]

Originally Posted by SV THIRD DAY

For the N-time...why would someone take their LiFePO4 batteries to near-fully absorbed anyway.

Sound like old school Lead Acid thinking to me....

Even more funny when coming from a guy who has been doing it on a daily basis... Just go back to your old posts telling us of your gear set to 13.7V with no current flowing into your battery. That's fully absorbed. Let's see: here and here. 2 years later and still learned nothing.

Now I could add something about replacing lead-acid thinking with "no thinking", but in the interest of some peace and quiet...

[SV THIRD DAY]

Just a little correction...that's 3yrs of a 400AH bank...no BMS...no capacity loss...no drama.

Actually there is another correction. Let me help you with a little Math.
13.7v on your battery bank is 3.425v per cell...that my friend is not overcharging by anyone's LiFePO4 standards.

I know it's hard for a BMS pusher to cope with...but math is math, voltage is voltage and simplicity rules the day.

Now back to your regularly scheduled program of LiFePO4 panic and over engineering.


But wait....
Lets use this opportunity to comment on all this talk and worry about cell balancing, as if its life and death because it isn't. What...heretic right...wrong.

As long as you stop charging based on your highest cell and then start charging before your lowest cell gets into the danger zone what's the big deal of them being out of balance...nothing. (remember the 90%-10% rule) You just lose a little capacity, but the way this balance issue is preached it makes it sound like you will blow yourself up or fry your battery bank....BS. I've been running two 400AH banks one on the boat as real life and one as a test bank and I have to chuckle at times at how people over-panic about these batteries making them sound way more complicated than they really are. In my opinion, a cruiser that could take proper care of their lead is dead bank can handle LiFePO4, you just have to know the rules and follow them. You can buy a BMS to follow these rules for you or do it manually...that's up to you.

[bill good]

Oceanseaspray
My aim is to better the 70% capacity over 7 yrs. This is what was predicted for electric cars which use the battery a little differently that us for house batteries. There is little data for "house batteries" & their use as such. I have a small 24ah life as a starter battery on one engine & a 40 ah life on the other engine & that installation has passed the lead TBF points. There is quite a bit in the install that I would not bore you with.

If it is not broke I will find something to work on!!

[OceanSeaSpray]

Originally Posted by SV THIRD DAY

Let me help you with a little Math.
13.7v on your battery bank is 3.425v per cell...that my friend is not overcharging by anyone's LiFePO4 standards.

I know it's hard for a BMS pusher to cope with...but math is math, voltage is voltage and simplicity rules the day.

One-stage CI: the flat curve of constant ignorance, my friend. Always talking, never learning anything: here it was, not long ago.

BMS?? Oh yes. I have built two hardware prototypes by now, the second with many improvements.

[SV THIRD DAY]

Originally Posted by OceanSeaSpray

One-stage CI: the flat curve of constant ignorance, my friend. Always talking, never learning anything: here it was, not long ago.

BMS?? Oh yes. I have built two hardware prototypes by now, the second with many improvements.

Oh I remember it...I just don't agree with the assumption behind it on how a cruising Boat uses and more importantly charges their battery bank, as if always attached to shore power.

Every once in a while someone will tell me that my water maker can't work the way it does because they made a spreadsheet and it won't work on paper, they are an "engineer" of course. That's what I'm getting here when I'm told what I've been doing now for 3yrs (and know dozens of cruisers doing the same) won't work or will have ill effects. So I'm asked to believe a guy on the internet that popped up with 300 or so posts VS my real life experience and test data. It's nothing personal against you...but I'll take my data and real world experience at this point in the game.

Cheers...
I gotta go call the Hazmat Response team to save me from my LiFePO4 battery explosion and core meltdown....

[OceanSeaSpray]

Originally Posted by bill good

Oceanseaspray
My aim is to better the 70% capacity over 7 yrs. This is what was predicted for electric cars which use the battery a little differently that us for house batteries. There is little data for "house batteries" & their use as such. I have a small 24ah life as a starter battery on one engine & a 40 ah life on the other engine & that installation has passed the lead TBF points. There is quite a bit in the install that I would not bore you with.

If it is not broke I will find something to work on!!

Nothing wrong with that for sure... my comment was general because measuring the cells on the flat is something lots of people do all the time, but you can't draw any conclusions from it.

I said that if you want to check balance, then you need to fully charge to see something. I seldom fully charge, but partial cycles only end up causing memory effects, so I don't mind charging a bit more at times.

If I run the engine long enough, then I end up almost fully charging because of my controller that tracks the current taper before terminating. It might happen a few times a year and it gives me those "maintenance" cycles.

[PacificGreen]

Upon further examining my BMS used on my batteries and the methods of charging, maintaining, and using my batteries I have decided that additional expenditures are required.

During the last week or two the discussions have caused me to research more on different components to upgrade my system. With the addition of the trolling motor that arrived a few days back I now realize that I can no longer be going about this method of charging in an uncontrolled manner especially if using gps anchor for a day or two at a time.

I discovered 123smartbms and the extended module to that. This is probably going to solve many charging questions and provide what I had lacked with the original bms system. I may very well be able to install this system on top of my existing system as well. Waiting to hear back from them. My current BMS has cell boards on the negative posts.

The 123smartbms cell boards sit on the positive terminals of all the batteries in the bank with an in board towards the negative end of the bank and an out board at the positive end of the bank. Dual 400amp current sensors track current out and in from the charge discharge source. So finally this will provide the bigger picture that until now I could only ever have an approximation of.

The extended module functionality also appears to be able to control Elcon can enabled chargers on the fly from their application that runs on windows. This would be a bonus as so far I've avoided the Elcon chargers because of the programming aspect of them. So far as I know there is only one other solution from EVTV that allows for programmatically changing the cc/cv values on the fly for Elcon chargers.

If everything checks out I hope to order a both a 16 board system for my 48v bank and another one to manage my 36v bank. Then I'll have to acquire both a 48v elcon and 36v elcon charger. This will in turn provide the ability to monitor the bms remotely anywhere in the world.

Previously I ran both my banks with a hands on approach and one without a BMS. The smaller one without the BMS comprised of 16 calb72cam cells was constantly out of sync due in part to post loading on the first cell or bad cells as I purchased the batteries used. After replacing what I thought were the bad cells and remixing I know I can not control this bank without a bms.

My bigger bank 48v 16 400ah winston cells can with a potted marine pcb components and actually a very robust HVC/LVC bms that did exactly as described. It was a good contrast to learn the differences between the two and to see what can go wrong and right. Now I only want information especially in regards to generated solar input at my fingertips and reliable state of charge numbers instead of approximations. I can't do that without upgrading my BMS.

[svGenesis]

In the very near future i'm need to build a 500-600Ah bank. can anyone recommend a good supplier of the batteries. (12-200Ah 3.2v)

[john61ct]

DIY?

ev west is good if you want CALB

[pacific_voyager]

Just as an aside, the quote "Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote" was not written by Ben Franklin, but by Marvin Simkins of the L.A. Times

http://tinyurl.com/j66mdyk

[Hkalan]

Hello,

I have an opportunity to pick up 16 Winston Cells 3.2v 1,000Ah from a local battery distributor that is closing its doors in a few months. Price is too good to pass !!

I don't read allot about the higher Ah cells, and curious of what the "cons" would be.

My 400Ah Calb cells are the bee's knees. But I cannot find any major discussions on higher Ah cells.

Would appreciate any feedback !

Alan