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Old 11-01-2013, 14:49   #1006
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Finally got a chance to sneak into the shop and take some initial measurements.

Initial Cell Voltages - Fluke 179 DVM
Cell #1 = 3.275V
Cell #2 = 3.297V
Cell #3 = 3.285V
Cell #4 = 3.281V

Wired in parallel @ 15 minutes pack voltage 3.284V



I am measuring the current between batteries and it is moving between the cells at a high of about .59A to Cell #1.


Current to cell #4 started out at about 0.4A and is down to 0.18A:



Here is cell #4 taking 0.4A and the parallel bank voltage of 3.284V:


I plan to leave them in parallel over the weekend at least...... I will occasionally monitor the current flow between cells.


I am VERY glad I ordered the extra jumpers as well the bolts and washers. If ordering from Balquon be sure to order these items. These bolts are not a size I have kicking around and take a 7/8" wrench....
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Old 11-01-2013, 14:59   #1007
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

nice pics and nice test gear

dave
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Old 11-01-2013, 15:03   #1008
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Doug,

I like these cells. I've never had such a flat voltage curve during discharge from 5% DOD to 80% DOD. I'm glad I bought an e-xpert battery monitor that I can program for the w-hr of my bank because you won't know by voltage drop, there isn't any. It uses a shunt, so knows wattage pulled and then calculates for the "fuel" gauge display. Without it, I would never know when I'm at 80% DOD where you get good cycle life vs energy used.

As to the psychedelic load, just visualize that shining on the main sail at night. A nice safety feature should you find yourself sharing the same body of water as deputy sheriff Russell Perdock. Google his name if you don't know what I mean.
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Old 11-01-2013, 15:06   #1009
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Nice picture of a 3.2 volt 1,600 a-hr battery. lol
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Old 11-01-2013, 18:57   #1010
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by Maine Sail View Post

I plan to leave them in parallel over the weekend at least...... I will occasionally monitor the current flow between cells.
Do you plan to charge or discharge them while paralleled ?
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Old 11-01-2013, 21:04   #1011
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by NahanniV View Post
Do you plan to charge or discharge them while paralleled ?
Once the current has stopped flowing between batteries they will get charged in parallel. At 11:00 PM, about 6 hours after wiring them in parallel, there is still a few tenths of an amp moving between cells..

I have an adjustable bench top power supply for charging this bank in parallel, though at 1600Ah it will take some time.. No rush though.. Before I wire up the BMS I am sure these will get played with a lot in terms of top and bottom balancing just for the sake of experimentation. I specifically bought these batteries for the learning experience.

I also plan to wire up a load test for them with a low voltage cut. Ah's will be counted with a programmed battery monitor with the Peukert set to 1.0!!! Never in my wildest dreams did I ever think a battery for a boat would have a 1.0 Peukert... Cool stuff...

Oh and I think I will have only slightly more than the cost of equal Ah AGM batteries into this project by the time I am done..
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Old 11-01-2013, 21:16   #1012
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Maine Sail,

Never caught your name. I don't think these cells respect Mr. Peukert at all. Before I took you up on the adjustable PS, I tried to bottom balance by shorting automotive jumper cables across the high cells. Probably 2~3 C, pulled voltage down maybe 0.02 volt under that load.

When I only got 980 w-hr out of the first cycle before one cell dropped, I was a bit concerned that I didn't get the 1280 w-hr with that light C load. This time around I'm at 1200 w-hr and all the cells are still at 3.27 volts and still going. It is 8:30 here, hope it gets to 100% DOD before bedtime so I can hook in parallel and charge with the PS.
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Old 11-01-2013, 21:56   #1013

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

Just heard today that one of the many small incidents bedeviling the new Boeing 787 was apparently a fire in a lithium ion battery. Indicating that Boeing likes lithium, and, that even Boeing can't quite figure out how to handle it.

Then again, here we are maybe fifty thousand years after fire was invented, and we're still having problems with that.
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Old 11-01-2013, 21:58   #1014
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Well, it is a good weight savings for the Dreamliner.
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Old 12-01-2013, 03:10   #1015
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Anyone know how a lithium batt fire could be put out on a boat? I read it took 40 mins to extingush on the 787.
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Old 12-01-2013, 04:32   #1016
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What Li Technology was in the Boeing. You have to be careful as Li ferrous is different.


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Old 12-01-2013, 04:43   #1017
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Dave, you were faster
I read a number of reports on this incident and they lack this piece of information about the specific chemistry of cells used by Boeing. FAA requirements do not state this either. https://www.federalregister.gov/arti...y-installation

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Old 12-01-2013, 04:54   #1018
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Sounds like LiPO.


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Old 12-01-2013, 05:13   #1019
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Yes, which does not say much. The 'PO' part means 'polymer', which refers to the fact, that the Lithium-salt electrolyte is not contained in an organic solvent but in a solid polymer composite.

Still, no indication whether it was Li-Fe, Li-Co or Li-Mn. These are different beasts.
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Old 12-01-2013, 11:29   #1020
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Once balanced, these cells exceed their rating. My packs are small, (2) 12 volt 100 amp. They should produce 1280 w-hr, but on one of the early cycles produced 980 w-hr. Last night it was so late I stopped when they dropped from 3.27 (all cells) to 3.26. Not much of a drop but at that time they had given 1350 w-hr.

Charging now for the first time in parallel for the good bottom balance. At the rate of charge, should take the whole weekend.

I didn't want to un-band the cells so couldn't make the nice and clean connections that Maine Sail made using his extra buss bars, but used 6 gauge and jumpers to do the same thing.


2nd battery on the load while the other is being slowly charged in parallel.


The variable power supply rated at a max output of 300 watts is twice the size and weight of the charger which is rated at 750 watts.
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