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

[deckofficer]

4 of these 92 lb (about the heaviest single cell I would want to lug around) cells would sure make a great 12 volt, 1,000 a/hr house bank. At a 3000 cycle life, would be the last house bank most of us (over 40) would need in our lifetime. 12.8 kW/hr for $4400, makes having a fully electric galley possible, ditch the propane.

If your into diesel-electric hybrid propulsion like I am, then (16) of these are all you need for a 150 nm all electric range and using a 48 volt inverter that looks at galley loads as child's play, running a 1500 watt appliance with an DC amp draw of less than 30 amps. How sweet is that?

[ebaugh]

That 1000 AH bank, fully assembled, is $3450. See:

http://www.balqon.com/store.php#ecwi...&sort=priceAsc

Then select HIQAP..

[deckofficer]

Originally Posted by ebaugh

That 1000 AH bank, fully assembled, is $3450. See:

Balqon - Advanced Transportation Solution

Then select HIQAP..

That is great, thanks for that. Fully assembled and save $1000, works for me.

[deckofficer]

Originally Posted by ebaugh

That 1000 AH bank, fully assembled, is $3450. See:

Balqon - Advanced Transportation Solution

Then select HIQAP..

There is more to that site than I knew from yesterday's purchase. For my diesel-electric hybrid propulsion I can live with a 60 nm all electric range, so their fork-lift battery would be perfect, 48 volt, 400 a/hr 20kWhr with BMS and more for $7950. I won't have to roll my own.

[hellosailor]

Sweet. Speaking of diesel-electrics and fork lifts, I wonder if anyone is using lithium-whatevers in diesel electric subs? Or if any of the big fork lift makers have gone over to them?

And why one of the terminals on your batteries uses a copper fitting, while the other is silver metal?

[deckofficer]

Originally Posted by hellosailor

Sweet. Speaking of diesel-electrics and fork lifts, I wonder if anyone is using lithium-whatevers in diesel electric subs? Or if any of the big fork lift makers have gone over to them?

And why one of the terminals on your batteries uses a copper fitting, while the other is silver metal?

All modern Navy subs are nuke powered. The company that I posted about for these batteries is addressing the port pollution at our major container ports and are building electric yard tractors for moving those 60,000 container/chassis around. They also build 70 mph highway tractors and a bobtail chassis for class 6 trucking. I see in the future someone making a motorhome out of these and the owners of said electric motorhome could cruise America, stopping overnight at any RV campground that touts 50 amp service. Even if a night's stay at a swank RV campground runs $30 a night, at a charge rate of just 10kWhr, you could suck down more in electricity. Works out to free fuel for your trip. Of course if it catches on, then the RV park owners will use the meters even for overnight stays.

[hellosailor]

"All modern Navy subs are nuke powered."
Ergh, no actually. USN subs aren't what much of the world can afford, so diesel electrics are still out there being used by drug cartels and non-superpower-navies alike.

On the RV front...like you say, once the campground, or your marina, sees a couple of hundred extra kw on their electric bill, they'll find a way to start metering the electric vehicles.

There's been enough hucksterism in vehicles over the last hundred years that I don't expect EVs to be any different in the next couple of dozen. Stanley Steamers didn't explode--although Detroit convinced the nation they did. Diesel electric locomotives weren't any better than quadruple expansion steam, although GE said otherwise. And real trolleys got evicted in favor of busses with rubber tires (Firestone et al) because once the tracks and wires were gone, no one could afford to reinstall them. All major con jobs, all foisted very successfully on the rubes. Ergh, American Public.

[T1 Terry]

Originally Posted by deckofficer

2.8 volts is fully discharged, 4.0 volts equalizing so not run that high on charge very often. More than 90% of its use, holds close to 3.2 volts, so 4 in series is 12.8 volts. Besides, electric motors can be run at higher voltages as long as you do not exceed the design rpm. At my 20 amp draw, that would be less than the 0.5C rate discharge, and as you can see from the graph that battery cell will be 3.2 volts down to 3.1 volts for 80% DOD, or on the 12 volt pack 12.8 volts to 12.4 volts.


Makes ya drool, doesn't it?


One of my humble cells

Hi Rob,
Is that an actual photo of one of your cells or just a generic photo? The reason I ask, those cells with the split globe on the logo are roughly 3 yrs old, still could be unused but not factory fresh so that could account for the low price.
I have 2 x 360Ah @12v nom. battery packs made from 90Ah cells, half the older cells like in the photo and half newer style logo cells that include the Yttrium in the mix, they have been in use 24/7 since June 2011. A bit early to tell if there is any life cycle differences but at the moment they do every thing I'd hoped for, and probably more. I drag down over 200Ah overnight, recharge by solar, loads vary from 1.5C down to a trickle, they power all my refridgeration, solar hot water recyling and the house when the power goes off. The sun doesn't always shine and I've pulled them down till the inverter dropped out at 10.5v on more than one occasion and they bounce straight back as soon as the sun came out. Remarkably tough units. My future plan is to build a hybrid electric drive for my motorhome conversion, their 250HP 6 speed Alison combination looks very interesting, might make further enquiries.
You won't have any problems powering the electric boat motor with 4 of these cells, the terminal voltage remains better than 13v till 80% DoD even at close to 1C discharge so the added votage will be noriced compared to lead acid battery power.
good luck with the project and please keep us up todate.

T1 Terry

[deckofficer]

Terry,

Great info, and no, the picture is generic, I just ordered mine yesterday. It is good to hear shelf life with your older cells seems to be good. Pulling them as low as you have I guess your going without BMS. I think I might go BMS with one pack and not the other because both packs will be subjected to the same duty cycle and that would be a good "a" vs "b" test to help me decide if I want BMS for larger banks. I feel if I watch discharge and swap out at 70%~80% DOD and never over voltage on charge, then the non-BMS protected bank will do as good as the one with BMS protection.

[T1 Terry]

I just use a Junsi cell logger for the high and low cell alarm. the cells can go down to over 100% capacity if the load isn't high without the cell voltage dropping below 2.8v but once an induction motor start up load hits the voltage drops, in this case enough to produce a 10.5v inverter cut out. As soon the load drops the cell voltage recovers so the real cell killer, low voltage, doesn't occur.
The whole 80% DoD and 70% DoD could be a case of interpretation of the test results as they also give a 100% discharge cycle life. One of the lines of thought is the cells can handle 1,000 100% discharge cycles before they start to loose capacity, after 3,000 cycles they will still have 80% capacity and after 5,000 cycles 70% capacity. That would mean every cycle was down to the low voltage cut off so any cycle that doesn't go down that far is a bonus. As no one has had the cells long enough and measured the depth of each cycle it's an unknown but the way the discharge chart is set up on the Winston site lends a little weight to this theory. If you look at the top right hand chart and use 3v as the cut off you can see where the 100%, 80%, 70% and even a 60% DoD cycle capacity is listed. It's all in the interpretation :lol: Looking at Winston's test procedures there load cut off is 2.5v at a 0.5C load for cycle life and 2.5v cut off for each capacity test at 0.5C, 1C, 3C and 5C so the 100% discharge practice appears all the way through their test procedure.
I initially followed the lead that 80% was the limit for long life but I'm leaning more toward a safe voltage cut off as far as low cell and high cell volts is more the aim, stay within the 3v and 3.6v window and the cells aren't stressed.
I accidentally stressed a cell, well a few cells causing them to get the pregnant bulge, I left one on the shelf but placed the other one in another experimental pack just to see what happened. It initially had less capacity, went flat first, reach high voltage cut off first, I even accidentally dragged it down to 0.8v. It charged back up again, cycled with the others for around 2 mths and gradually it's capacity returned and it's pregnant state has reduced, something completely un expected, I was sure I'd killed it, they are tough buggers.
You do realise that Balqon is Winston Chung's US distribution arm, from the Kriss Motors White Paper,
"Chung, using proceeds from sale of his Sinopoly stock (some of his
holdings were subject to lockup restrictions and could not be sold),
purchased a controlling interest in Balqon, a struggling U.S.
manufacturer of large industrial electric vehicles, and transferred U.S.
distribution rights to this restructured entity. He also created a new brand,
Winston Battery."

You must be on a winner buying from the Chinese seller/manufacturer.


T1 Terry

[deckofficer]

Terry,

I'm just glad to support a company that is building emission free class 6 and 8 trucks. The price being lower than any place else was a nice added bonus.

[ebaugh]

Originally Posted by T1 Terry

I would not charge beyond that but at a 0.1C rate till the 3.8v was reached, then let the cells sit for 1hr and see if the voltage remains above 3.5v rested, if any cell pack doesn't hold 3.5v repeat the process. I was quite surprised just how many more Ah of charge went into the Winston cells after they reached the initial 3.5v per cell but once they had been fully charged they seem to accept charge readily all the way to 95% and stay as a pack but until then they jump around a lot, some times high, some times low compared to the others in the series group and taking up to a mth or two of daily cycling to settle down.

T1 Terry

Terry,

Just had a chance to do this in the marina. The "low" cell took about 150 AH to top off. More than 15 percent of its 1200 AH capacity. Not good, so I investigated further and discovered some questionable connections on the interconnects. There are 48 batteries and 4 screws per terminal, 2 terminals per cell or just under 400 screws! They are allen key heads, but small and you must be careful not to strip them. I think I needed to use a higher torque on assembly with a screw gun, but have now tightened them all manually. Hope that was the issue.

Anyway they were all >3.5 an hour after charging to 3.6V. There is balancing to 3.55V, so this was pretty good. After 24 hours they clustered around 3.4V, but the low cell was the same one at 3.38V. I'm going to leave it alone until I get some more cycles on it, but that may be awhile with our current cruising plans in Columbia where you spend most time at marinas....

Is 3.4V after 24 hours too high? A possible indication of overcharge?

Bob

[T1 Terry]

3.4v is fully charged not over charged, 3.4v is what you are aiming for each recharge to give you 100% capacity. There is no real harm in reaching 100% capacity each recharge nor is there any harm in not reaching 100% capacity as long as there is sufficient capacity still in the cells to carry you through to the next recharge.
I did wonder if the 4 small screws would be an advantage or a disadvantage, the small diameter doesn't give a lot of area for thread tightening so the chances of the screws coming loose are increased. There are special washers called Nordic I think and another are Norlok, they have like ratchet teeth that lock into one another... but 400 screws would equal 800 washers, good luck with that task :lol: Did you use Alminox or an equivelant anti corrosion compound between the faces after lightly sanding them to a bright finish? Well worth the effort.

T1 Terry

[ebaugh]

I did use Aluminox on the screw threads since it appears to be a stainless screw into an aluminum terminal. That's to be sure I can take it apart a year from now! They do have normal washers and lock washers on every screw. But I did not do anything special to the surfaces. All the parts were new and clean.

One of the few advantages of 48 cells is the maximum current passing an interconnect is normally limited to about 20 amps. There are about 10 of them though that are much higher, and I paid those more attention on assembly.

I attached a diagram of the battery interconnects that show where there are extra bus bars. The yellow shaded areas are 80 amp fuses. The battery manufacturer suggested these for a parallel installation. Should any cell short out, the fuses will remove the cell from the pack. The cell balancers shown were not installed, just the EMS sense board.

[T1 Terry]

Interesting, I've never hear of lithium iron cells going dead short circuit, more an annoying self discharge one as a result of abuse or loss of capacity due to the case bulging. I have seen cell packs with a copper link narrowed in the middle fitted half way through the pack to act as a high capacity fuse just in case something goes wrong with a cable or BMS or some electrical connect within the box as all the fusing is outside and the boxes are a seal unit, the dead short melts the copper link basically to act as a high rupturing fuse.
I wonder if the manufacturer is just being on the cautious side of there is known problem with those cells as they are a slightly different chemical make up. You are only the second person I have seen who are using those cells, the other one is an EV and it's still in the build stage, the caps over the terminals and the 4 screw terminals are quite distinctive and certainly separates them from the crowd.
It will be interesting to see if shallow cycling brings all the cells back together again.

T1 Terry