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Old 29-11-2012, 16:46   #661
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

My two cents. I don't think it is ever a good idea to be on the cutting edge of technology on a cruising boat in any area. You want mature technology that is well understood all over the world and can be fixed anywhere. If you have plenty of money and time, and like to play with technology instead of cruising, have at it.
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Old 29-11-2012, 17:33   #662
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Wow Terry , that actually makes sense. I have read a quite a few posts in this thread and from what I have read I will call you the Guru so 13.8 v it is . I understand that this is a new technology , and one that I have not used so all i can do is trust someone that has . Thanks so much for the help , I will keep you updated . Making the call tomorrow. 13.8 v

This is my little setup , its inside a soundproof inclosure now .

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Old 29-11-2012, 17:49   #663

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

Terry-
The thoery about just playing in the middle of the charging range has, as you say, some strong support. Lenovo and other computer makers have been cycling their LiOn batteries that way for 6+ years. Their BMS typically can be user-set to either keep a 100% charge on the battery, or to let it float down to about 94% then bring it back to about 98% (and I'm sure those number are off, they're from memory) and supposedly doing that will "significantly" extend the battery life.
And then I think it was Honda or Toyota that said a few years ago, they cycle the much heavier packs in their hybrids from something like 60-85%, REALLY staying away from both ends of the charge cycle. Apparently this minimizes the physical movement of chemicals in the battery, and that translates into "moves less, wears out less".

Typhoon-
Since you have the external sense option I guess it doesn't matter to ask whether their alternators run blind or sense through the charge wire normally. (Delco used to do that, they switched the output from "charge" to 'sense' electronically back in the 70's.)
But you might want to ask if they have a thermal compensation available, a thermal sense lead that gets mounted on the battery and tells the alternator to throttle back when the battery is getting too hot.
If the output voltage is factory-adjustable only, there's still a fairly common kludge that you can discuss with them. You set the alternator for the lowest voltage that you will want, and then you can switch a diode into the sense lead to create a small voltage drop (typically 0.2-0.3v) which fools the regulator, causing it to put out slightly higher voltage on demand that way. That's oversimplifying a bit, but they will be familiar with it. Voltage selection/stepping depends on the diode choice. There are of course other slightly more complicated options to give you better control, including just going to an external regulator with battery thermal sensing, etc.
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Old 29-11-2012, 18:05   #664
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Terry, are you saying that charging to 14v will damage our cells, even if the amps are low? In my case, our solar charger will top off the batteries at or above 14v (depending on settings). The max it can put out is 15 amps, so less than .04c.

We just installed a new wind gen, which has an external controller, which also controls solar. We already have a 120w panel on the Sunsaver MPPT 15, and this new wind/solar (PWM) will have two, 85w panels. This controller is digitally controllable as to the voltage when it cuts out (brakes wind gen). I don't want them fighting each other, ie the voltage of one cutting out the other. I am thinking to have this cut out at 14.1?

Chris
The truth is there is little data available for constant charging or "float". The electric vehicle guys have the most experience with the batteries, and they charge to 3.6 or 3.65V per cell till current falls to .05C of the bank and stop charging. But our charging profiles are not the same. Especially with wind, solar, or passage making under power, we don't stop charging. What is the right value?

I've seen where Calb says 3.4V max per cell on "float" and my cell manufacturer (GBS) suggested 3.35V max for my cells on float. So somehow, I think the voltage for a 12V pack needs to drop to 13.6 or less once the charge current reaches .05C. Above that, I think you may be impacting cycle life.

Maybe one day we will learn more, but I'm trying to be conservative, and since the pack capacity is not changed much, I think the lower values make sense.
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Old 29-11-2012, 18:14   #665
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

The full time charging voltage should not be much higher than 3.45v per cell, if the boost voltage is 14v and then drops back to 13.8v float it will be fine, the voltage climb in these cells once they are full, 3.4v, is rapid so the time in over voltage is short, no individual cell or part of the cell will go over 3.4v until all the cells within that pack are over 3.4v under normal charging conditions.
The 0.05v is enough to evenly distribute the charge through all the cells, once a cell reaches 3.4v it's voltage will climb, the easier path is to another cell with lower voltage, once all the cells are at 3.4v in that parallel string the voltage can climb higher than 3.4v in any cell but again, reasonably evenly, Kirchoff's Law Kirchhoff's circuit laws - Wikipedia, the free encyclopedia. An even spread of 3.45v across all the parallel cells and all those sets in series in a 4 cell 12v pack equals 13.8v, 0.05v x 5 amps =0.25w, not much heat generation there and the 5 amps is about as much as will trickle across the cell packs doing the last top up bit till they are all full if the voltage limited to 3.45v per cell, even if it was 100 amps it's only 5w, still not much heating energy but if you brought that up to 3.6v per cell then the 100 amps becomes 20w heating energy in each cell, now you are starting to asking for trouble over an extended period, 4v per cell, the advertised max, 0.6v over voltage x 100 amps, 60w, they will boil fairly quickly at that rate. There isn't much electrolyte in each cell, maybe a tablespoon depending on size, could be a bit more in some brands but it wouldn't be much more, it's expensive stuff, it makes up a large part of the cost of the cell, the other materials are measured in micron thickness.

As far as new technology, only to the boating fraternity, Nasa were confident enough to use it on the Mars rover mission and there wasn't anyone up there to tinker with it. It was designed to last 90 days I think, that was back in 2003, it's still going with a strong battery pack, you couldn't get a much more hostile environment than that. Sure they were hand picked cells to get a near perfectly balance pack but's still just solar charged on a planet shrouded in dust storms, and it's has a heater element stuck in the on position so it drains the batteries over night. They have suffered one severe discharge but recovered. http://en.wikipedia.org/wiki/Opportunity_rover#Fall_2012

T1 Terry
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Old 29-11-2012, 18:36   #666
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

As far as heat sensing in lithium ferrous cells, mainly used to detect excessively high discharge rates in electric vehicles, I doubt anyone would look for more than 3C from a house battery pack as our battery packs are big capacity but low voltage, EV stuff is small capacity but high voltage, the total watt hrs are the same but the characteristics are quite different. 3C from a 40Ah cell is only 120 amps but 3C from a 200Ah cell is 600 amps.
Cell voltage will rise well before cell temp rises when charging so cell voltage is the one to monitor. I recommend using a Junsi cell log8 from the hobby shops (around $28 for data recording unit) and link an alarm and cut out relay to the alarm port. If a cell reaches 3.6v stop charging for a period of time and let it settle, then resume charging. We use a simple J Car timer kit set for 6 mins, not an issue with solar but an alternator would need another load path like a shunt load such as a water heater element or charge via the lead acid starter battery so the alternator sees the voltage rise in the lead acid battery and throttles back it's output current. The heater element suits solar charging better as there is no motor running to heat the shower water but the start battery is an easy solution in a motor generator set up, an air cooled gen set is the acceptation, a heater element works well for these.

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Old 03-12-2012, 23:48   #667
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

After 3 1/2 months they finally arrived. Notice the serious banding due to the cells ability for huge discharge and ultra fast charging causes bulging. These cells with their cycle life will out live me. This is one of two packs I bought, the other still in the garage. 31 lbs and can store enough energy to propel the kayak 30+ miles per pack.


Cells generally receive a 50% charge at the factory in China. 3 of the 4 cells read 3.32 volts, the one on the far left was 3.31 volts. Only 1/100th of a volt difference.


Pack voltage


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Old 04-12-2012, 00:05   #668
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Nice Bob, now you wouldn't be sitting an equivalent set of 'Trojans' on your desk!!!!
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Old 04-12-2012, 00:14   #669
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Nice Bob, now you wouldn't be sitting an equivalent set of 'Trojans' on your desk!!!!
You got that right. 25 years ago I used L16's on a regular basis for off grid. That was before 700 a-hr 2 volt AGM cells and as everyone on this thread knows, long before LiFePO4. These are my 1st and gives me a warm feeling knowing they will outlast me. With the cycle life, they are the cheapest battery you can buy, but on this thread I'm preaching to the choir.
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Old 04-12-2012, 01:25   #670
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Good post deckofficer. Glad to hear you finally recieved your batteries.

Well illustrated with photos.

Thanks

John

Looking foward to your project Frank.
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Old 04-12-2012, 01:37   #671
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Thanks John. Balqon was sorry my order got delayed. They go above the norm for packaging for shipment to the tune of a 34 lb wooden shipping box and closed cell packing sheets to insure no movement.
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Old 04-12-2012, 01:38   #672
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi Bob,
I've sent you a PM.

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Old 04-12-2012, 01:51   #673
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Terry,

I just rechecked balqon's site and though they aren't saying they are selling 3 year old Thunder Sky batteries, their quoted cycle life is 2000 @ 80% DOD. I just wonder what the going price for new Winston cells vs the older TS cells I wound up getting?
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Old 04-12-2012, 01:51   #674
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

John
Still awaiting the metalwork so i can mount my panels, it should be here in a week and a half, panels at same time.
Bought a new BEP Monitor that doesn't seem to want to work.
We are going back to Gladdie for xmas so upon our return we shall be flat out. I intend taking the monitor back at same time.
Cheers Frank.
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Old 04-12-2012, 03:49   #675
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Terry,

I just rechecked balqon's site and though they aren't saying they are selling 3 year old Thunder Sky batteries, their quoted cycle life is 2000 @ 80% DOD. I just wonder what the going price for new Winston cells vs the older TS cells I wound up getting?
That was a really hard PM to send as you were so excited about your new cells but I couldn't have lived with myself if I hadn't at least let you know.
On the Balqon site they show a photo of the old cells but they list them as LYP cells and clearly the part number on the cells in your photo say LFP, that's false advertising, no idea what the rules in the US are but in Aust that's hanging offence just about, a garunteed replacement with the correct goods or full refund, no questions asked.
the price for the mewest LYP cells in Aust is AU$1.40Ah so the 100Ah cells would be AU$140.

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