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Old 23-01-2013, 10:39   #1381
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by hellosailor View Post
Bob-
Thanks! I had no idea the PO4 batteries were a different voltage, never heard that mentioned before.

Dockhead-
But your example of of PO4 battery fire, isn't. The guy had PO4 batteries, he had a fire, he's got no evidence that the batteries caused the fire, as opposed to his charger, or his use of the batteries in cold weather that was clearly beyond their rating. That's like saying my refrigerator caused my house to burn down, because it was found in the remains.
I can see that a really vigilant battery make (or their distributor) might want to perform an autopsy on the remains. Or not have anything to do with it, because that might boomerang. But the only way to be sure about "cause" would be some very careful work investigating and the OP of that thread didn't take it to that degree.

Memo, add a "low temperature crowbar shutdown" switch to your charging setup.<G>
The minute it can never happen, it does.
I agree that the batteries can be used safely, but they do need to be set-up competently. With good fail-safes.
As heat is their enemy a fire caused by some other source, these are going to add fuel to the fire.

Lloyd


http://www.youtube.com/watch?feature...&v=lTHfzUY69okhttp://www.youtube.com/watch?feature...&v=lTHfzUY69ok

and a link to the website with the details http://www.ev-power.com.au/-TECHNICAL-ARTICLES-.html
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Old 23-01-2013, 15:11   #1382
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Yet another BMS fire. The other problem was quite possibly caused by Hi power cells not having a vent cap, it is just a screw in plug, if the cells weren't strapped, an over charge occurred due to a bms failure, the battery would have eventually exploded creating all sorts of potential ignition sources. The vehicle would have been full of boiled electrolyte similar to boiled petrol, and then ignited. Also keep in mind, that system was a lot more than 12v or 24v, more likely up in the hundred volts area.

T1 Terry
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Old 23-01-2013, 15:34   #1383
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by hellosailor View Post
Bob-
Thanks! I had no idea the PO4 batteries were a different voltage, never heard that mentioned before.
Yep, gave up some energy density with LiFePO4, for a more stable and safe cell. Most all charts that give cell voltages for different battery types just don't include the new LiFePO4 and its 3.2 volts. Easy mistake.

The 3.7 volt lithium cell I use in this custom built 3000 lumen flashlight is a special high C design. The same size cell of common design would do what so many seem to worry about when pushed as hard as this light pulls the amps, and that is burst into flames. I think that is where some lithium batteries get a bad rap, hobby builders going for the highest energy density without checking the C rating. Nobody here using LiFePO4 for house banks will have that concern, as the C rating is more than adequate to handle whatever an inverter could demand, coupled with the very stable chemistry of LiFePO4.


Even with these heat sinks, after 15 minutes the flashlight is almost too hot to handle, but when you need a lot of light in a small package, it fills the bill.
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Old 23-01-2013, 15:50   #1384
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

An excerpt from another forum..
N.B. I've put li-ion in inverted commas above because all lithium batteries including phosphate are li-ion batteries. Li-ion was the name given originally to the hard cell case lithium batteries with plate construction of the time. Li-ion refers to the way they work. Later a polymer construction of the cell contents was developed which enables soft cell casings, so Li-polymer refers to the construction.

Lithium iron phosphate (chemical formula LiFePO4) refers to the chemistry, so we have the silliness of three ways of naming lithium batteries!

Perhaps a more accurate way to identify is by the principal cathode material, for example: lithium-ion cobalt, lithium-ion manganese and lithium-ion iron, but that last name is very confusing and the position is being made more complicated by modern cathodes being complex compounds of numerous elements.

One day there'll be one dominant type and life will get simpler.
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Old 23-01-2013, 16:10   #1385
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I love when I tell people "I have lithium iron phosphate" batteries, most reply "lithium ion phosphate" as if to correct me. I usually just surrender at that point, and change the subject to sports or weather.
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Old 23-01-2013, 16:12   #1386
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Thanks Lagoon4us for that. I was just trying to end the "unsafe" debate on LiFePO4 cells. I'd trust these cells over LA any day.
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Old 23-01-2013, 16:29   #1387
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I really believe it's totally accepted the LiFePO4 that we are all considering/ testing /
trialling/fitted or fitting are safe, the actual engineering is what we need to get right.

So far from the thread we are weighted to not incorporating a BMS leaning more towards Loggers that alarm on hi or lo voltage of individual cells.

My view is that as a cruising boat we will not be on board constantly and our solar will constantly charge these batteries during sunlight times SO a workable disconnect is essential. Terry has described his preferred way of dealing with it but as my knowledge is not electrical i scrape to get a clear understanding.

All of us that eventually set these up on our boats will need this disconnect ability.
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Old 23-01-2013, 16:36   #1388
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

One engineering issue that needs to be worked out is how to charge LFPs without continuously charging them, as they do not like that. We've been doing this to lead acid batteries for over a hundred years now, so it'll be a hard habit to break.
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Old 23-01-2013, 16:39   #1389
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Isn't that what the regulators set for LITHIUM do? Or am i not understanding?
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Old 23-01-2013, 16:55   #1390
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I don't think I would just blindly trust a charge controller with a simple "lithium" setting---as that could actually mean lithium cobalt oxide. And even a controller with a bona fide LiFePO4 setting could employ a questionable or simplistic charge algorithm (eg hold at 3.3V/cell) that may not be concerned about maximizing the battery's lifespan.

In my specific case---where I always have lots of sun---I want it to charge up to 3.45V/cell every morning, then stop charging for the rest of day, regardless of load. I believe that scheme will work really well for me---but not necessarily anyone else.

For example, in situations where solar energy is hit and miss, the controller should use a different scheme: grabbing every available amp-hour whenever it can.
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Old 23-01-2013, 19:57   #1391
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

My system is a continuous charge, basically, it stops charging when it reaches 14v at bulk and 13.8v float. if nothing is using power then nothing comes in, as soon as there is a load the solar trys to power it, the battery makes up the shortfall, when the load finishes the solar tops up the battery and then stops charging until the voltage falls. asically the same system we used with lead acid batteries, the difference is the lower charging voltage. those that charge at 14.4v and higher are asking for cell to run away really because even if the cells were perfectly balance 14.4v is still 0.2v above fully charged. One cell only has to be 0.01Ah more charged than the others and it will run away at those charging voltages, the 0.2v from each cell equals 0.8v on top of the 3.4v when fully charged = 4.2v and a cell being damaged.
Then the safety back up system becomes a control system, cutting charge when any cell reaches 3.6v, better to have a lower charging voltage of 13.8v and the back up system just in case a cell runs away.

T1 Terry
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Old 23-01-2013, 20:28   #1392
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by diugo View Post
I don't think I would just blindly trust a charge controller with a simple "lithium" setting---as that could actually mean lithium cobalt oxide. And even a controller with a bona fide LiFePO4 setting could employ a questionable or simplistic charge algorithm (eg hold at 3.3V/cell) that may not be concerned about maximizing the battery's lifespan.

In my specific case---where I always have lots of sun---I want it to charge up to 3.45V/cell every morning, then stop charging for the rest of day, regardless of load. I believe that scheme will work really well for me---but not necessarily anyone else.

For example, in situations where solar energy is hit and miss, the controller should use a different scheme: grabbing every available amp-hour whenever it can.
Controller is MPPT so nothing's missed, i've built the panels to tilt there are 3- 230's. GSL are specialists with controllers, there are three settings that are easily set to suit our choice Nominal/High Capacity/Long Life.

They are built for LiFePO4 specifically.
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Old 23-01-2013, 20:57   #1393
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I should have quoted voltages, der...

1) Nominal - 14.60volts max.

2) Long life - 14.30volts max. We will use this setting. Maintenance is 14.10 volts

3) High - 14.80volts max
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Old 23-01-2013, 21:02   #1394
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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My system is a continuous charge, basically, it stops charging when it reaches 14v at bulk and 13.8v float. if nothing is using power then nothing comes in
Are you saying that you let your battery current fall all the way down to zero when "floating" at 13.8V? You seem to be completely ignoring the concept of charge termination current.
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Old 23-01-2013, 21:25   #1395
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Safety is no accident. LIFEPO4 have been involved in fire & each case gives up the lessons needed to make systems better. EVERY wire & control boards added must be made safe & 100% prevented from adding to fire. i.e. adding circuit board type fuses to all circuit boards & wires used for the add on circuits. Not seen any with this level of protection as yet!! CC/CV may be good for a single cell but I believe this method of charging a pack has resulted in failures about 500-800 cycles due to cell differences. The use of packs with series & parallel cells may be prefered to a one with series cells. There is still much work to be done to make sure no fires occure.
The unfolding problems for Boeing this week promps this response even though a different type of Li ion all the above still apply. I will continue to use the cells but cutoff the charge before the CV point.

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