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

[nimblemotors]

Originally Posted by daddle

Ferrocement battery box? Like tile backing board?

That is an interesting idea, only downside I see is they are relatively heavy.
Having just put up a lot of it in my bath remodel even with the perlite mixed in, a 3x5 1/2in panel is quite heavy.

JackB

[nimblemotors]

I saw the Winston bankruptcy.. no surprise really, a deal to good to be true...I'm guessing that 5-year warranty is about as good as naught about now.

Cells seem to work fine though I've still not actually done anything with mine yet.

JackB

[diugo]

I suspect Balqon will handle US warranty claims thusly, as long as their doors are open: First and foremost, customer pays shipping both ways, to discourage any nuisance claims. Then, if there happens to be an old cell of the same model on the shelf, it's yours. If no old cell in stock, the amount you paid is prorated against the five years, then applied solely as a store credit for your choice of whatever they do have in stock. Your old bad cell goes on the shelf to "satisfy" a future warranty claim---or is sold as a clearance item.

This is probably why they don't publish their warranty policy.

[FlyingCloud1937]

Originally Posted by diugo

I suspect Balqon will handle US warranty claims thusly, as long as their doors are open: First and foremost, customer pays shipping both ways, to discourage any nuisance claims. Then, if there happens to be an old cell of the same model on the shelf, it's yours. If no old cell in stock, the amount you paid is prorated against the five years, then applied solely as a store credit for your choice of whatever they do have in stock. Your old bad cell goes on the shelf to "satisfy" a future warranty claim---or is sold as a clearance item.

Well, according to Balqons 10K report they are owned lock/stock and barrel by a Mr. Winston Chung, whom is Bankrupt by HK standards.

http://www.cruisersforum.com/forums/...ml#post1175293

Lloyd

[FlyingCloud1937]

Originally Posted by ebaugh

I probably invalidated the AIC interrupt warranty on my ANL fuses since I took them out of the case. But could someone explain why AIC is even a factor for this fusing? I can see where a circuit breaker could fail due to internal issues, say getting welded on the inside, but how could my ANL fuses possibly fail to open at any current level? I suppose I could vaporize both a normal interconnect and a fuse simultaneously, but I just don't understand how it could possibly ever ever fail to open. Can anyone explain?

Have you ever seen a glass fuse fail grounded?

Have you ever seen a tungsten bulb fail grounded?

I have both were backed up by other circuit protection, both could've caused a fire.

Lloyd

[Lagoon4us]

Existing now worldwide are quite a few million lead acid batteries, loosely mounted, mounted in timber, fibreglass and plastic boxes.

Those lead acids when charging give off gases that are flammable/explosive.

It is these very batteries(bombs) that Lithium are replacing.

Our house bank that we are replacing is 5 Varta 135 amp Lead Acids which are spread below a double bed in the aft cabin enclosed in plastic moulded boxes.

The interconnecting heavy battery cables would i believe weigh as much as the Lithium installation i.e. 4 x 400 amp cells.

Gone will be the gases, as too the dangerous quantities of sulphuric acid that when mixed with sea-water will create deadly chlorine gases let alone the spray on all surrounding wiring, switches etc from a battery explosion.

I've built an aluminium case that has insulated areas where there's possibility of any contact, i've incorporated fuses on both positive and negative the case has bolt down ability to the sole, the total area in plan view is .25 of a square metre.

All the boards are mounted above the cells NOT at the end of the cells where any cell movement by bulging or rupture can bring on shorting or arcing of the circuits.

The wayward bolt that may have been involved in the Boeing failure may have been there from initial construction, i.e. simply dropped?

[FlyingCloud1937]

Originally Posted by ebaugh

I probably invalidated the AIC interrupt warranty on my ANL fuses since I took them out of the case. But could someone explain why AIC is even a factor for this fusing? I can see where a circuit breaker could fail due to internal issues, say getting welded on the inside, but how could my ANL fuses possibly fail to open at any current level? I suppose I could vaporize both a normal interconnect and a fuse simultaneously, but I just don't understand how it could possibly ever ever fail to open. Can anyone explain?

A fuse can fail to closed(short circuit) just as a tungsten bulb re-plates itself, a fuse can also.

And they do, especially if the wrong fuse is used.

A fuse only serves it's purpose if it meets the job rating, otherwise it's a WAG


Lloyd

[diugo]

Originally Posted by FlyingCloud1937

Well, according to Balqons 10K report they are owned lock/stock and barrel by a Mr. Winston Chung, whom is Bankrupt by HK standards.

Just because Chung is bankrupt, doesn't mean Balqon is. Chung merely owned shares in Balqon, not Balqon itself. His shares (or a portion of them) will simply be distributed to Chung's myriad of personal creditors. Together, they may own a majority of Balqon's voting shares---but they would have to vote in a largely unified bloc to make any big corporate changes. Much easier said than done.

They could vote to liquidate Balqon's assets---but it likely owes its own creditors more than it's worth. They could vote to sell the company (to Sinopoly?) or declare Balqon's own bankruptcy---or they might see more value in actually helping the company's green agenda succeed, through changes in management, or perhaps even additional investment.

In the meantime, it will just be business as usual there.

[FlyingCloud1937]

Originally Posted by diugo

Just because Chung is bankrupt, doesn't mean Balqon is. Chung merely owned shares in Balqon, not Balqon itself. His shares (or a portion of them) will simply be distributed to Chung's myriad of personal creditors. Together, they may own a majority of Balqon's voting shares---but they would have to vote in a largely unified bloc to make any big corporate changes. Much easier said than done.

They could vote to liquidate Balqon's assets---but Balqon may well owe its own creditors more than it's worth. They could vote to declare Balqon's own bankruptcy---or see more value in actually helping the company succeed, through changes in management, or maybe even additional investment.

In the meantime, it will just be business as usual there.

actually you should read the 10K's
as 90% of investment and future business are dependent on a Mr. Winston Chung.

That would be prudent, for any investor.

L

[diugo]

Originally Posted by FlyingCloud1937

actually you should read the 10K's
as 90% of investment and future business are dependent on a Mr. Winston Chung.

Actually, I did.

[Maine Sail]

Originally Posted by diugo

This experiment is highly flawed. The fuse has resistance of its own, say five millohms. Add this to the battery's two millohms, and the maximum possible current is 13.3/.007 = 1900A, according to Ohm's Law.

The experiment mimics a "real world" installation in a boat where MRBF and ANL fuses are used often. I am using a Class T on my boat but was curious to see because I have some sub circuits that are fused with ANL which would be after the Class T..

Originally Posted by diugo

How much resistance does 15' of #8AWG add? Another 12 millohms by my reckoning. 13.3/.019 = only 700A. Not really a good test of the A.I.R.

I suspect your math does not agree with my Fluke.. I had my 1000A Fluke clamp meter around the wire in the 8GA experiment and it went into over load instantaneously when set to in-rush mode. I knew it could not handle the load but wanted to see if the 8GA wire exceeded 1000A before the fuse blew. Apparently it did.. Still the trip time was so quick the wire never even heated up. The meter is rated for 1000A DC so that is already 300A over your 700A math....?

That 8GA was but ONE of the experiments. I did that one just to see if an 8GA wire could handle a 300A fuse into a dead short circuit. I had never done anything like that before (far too small wire for the fuse on a Li bank). The wire jacket never even got warm to the touch.

The ANL's were blown on approx 3' of 2/0 wire into a dead short NOT on the 8GA wire.

Originally Posted by diugo

The fuse interrupt rating becomes more of factor as the bank voltage approaches the fuse's voltage rating---since doubling the voltage doubles the amperage.

And we are using 13.4V banks on a 32Vdc 6000 AIC rated fuse. So what is the AIC rating at 13.4V or even 12V? Cooper Bussmann does not know, because they have not tested it, I asked...

Originally Posted by diugo

One more point. A fuse is required to handle the interrupt current without exploding or catching fire, but also failing in a mechanical way that might weld its terminals together. It is also required to operate in a specific, usually very short period of time. It does so to protect connected equipment---most notably, the insulation on cabling. You can imagine that with thousands of amperes flowing right next to you, every millisecond counts when you're made of plastic.

Yep and even a 300A fuse on 15' of 8GA wire blew in such a short duration that the wire jacket never even was warm to the touch. It exceeded my 1000A clamp meters capability but the fuse still did its job even with wire FAR to small for a 300A fuse.

I will gladly blow as many ANL's as you guys want to send me. I have already done three ANL's and two MRBF fuses and they suffered no damage and all opened to protect the wire in a dead short situation..

It seems you are walking both sides of the fence on this argument. On one post you insist the ANL's don't meet the qualifications for a Li bank then in another post you state opposite arguments how my short circuit experiments were "flawed" and only reached 700A and 1900A. Well, if that is the case, then it appears that ANL and MRBF fuses seem to work fine even on a 400Ah Li bank, as they would be installed on a boat...

So do we really need Class T, or higher AIC, rated fuses..? That is the real question.....?

I'd like to have an n=25+ on the ANL's so come on guys drop them in the mail to me and I'll pop away...

[goboatingnow]

There are a number of issues here

interrupt capability is based on a test at a voltage. Hence if you are operating at a different voltage you cannot be exact in the determination. MaineSails tests are completely valid and most fuses will interrupt at far greater values then tested.

Given this is all an unregulated area and many LA systems arnt used at all, I would calmly suggest that ANL fuses are adequate.


Furthermore using an "internal resistance of a battery" to determine short circuit current is not a valid method, Battery internal resistance is a complex value and not constant, Its an equivalent resistance not an actual resistance. ( in fact its an impedance as it has a complex part).

The fact that you have X voltage drop at a particular current, means that the equivalent impedance is Y, its does not mean that is the case at all other currents.


Whereas the resistance of a wire is for all intents an purposes fixed at DC , irrespective of current or voltage.

dave

[diugo]

Originally Posted by Maine Sail

It seems you are walking both sides of the fence on this argument. On one post you insist the ANL's don't meet the qualifications for a Li bank then in another post you state opposite arguments how my short circuit experiments were "flawed" and only reached 700A and 1900A. Well, if that is the case, then it appears that ANL and MRBF fuses seem to work fine even on a 400Ah Li bank, as they would be installed on a boat...

So do we really need Class T, or higher AIC, rated fuses..? That is the real question.....?

I said simply that LFPs can easily exceed 2700A. Do you really dispute this? It is less than 7C for a 400Ah bank. This amount of current is only accomplishable by a 3.3V cell with an internal resistance of no more than 1.2 millohms. Again, not unreasonable, as large cells are spec'd by Winston to be well under 0.5 millohm---and you yourself measured one of your cells at 0.7 millohm IIRC.

I chose 2700A because I honestly believed that it was the correct DC interrupt rating for ANL fuses---based on the same datasheet downloaded from several sources.

On the other hand, you quickly claimed the 6000A rating as gospel, then in the same post, contrived an experiment to "test" this. Did any of your tests truly succeed at sending 6000A through an ANL?

If not, then the encouraging results you obtained are not earth shattering---they simply indicate the fuse behaved as advertised.

[diugo]

Originally Posted by goboatingnow

interrupt capability is based on a test at a voltage. Hence if you are operating at a different voltage you cannot be exact in the determination.

The rated voltage and interrupt rating are closely related, because ultimately, the fuse's survival is based on the power it can readily dissipate, which is a function only of its internal resistance and the square of the current passing through it.

MaineSails tests are completely valid and most fuses will interrupt at far greater values then tested.

Nonsense.

Given this is all an unregulated area and many LA systems arnt used at all, I would calmly suggest that ANL fuses are adequate.

Adequate only for sufficiently small banks where maximum current is sufficiently limited to 6000A by total circuit resistance.

Furthermore using an "internal resistance of a battery" to determine short circuit current is not a valid method, Battery internal resistance is a complex value and not constant, Its an equivalent resistance not an actual resistance. ( in fact its an impedance as it has a complex part).

More nonsense. The physical materials in a real world battery have very real "actual resistance".

Impedance is a strictly AC concept, and batteries do not normally operate under AC conditions. From a math standpoint, all the complex impedance components are all zero at zero frequency---which is what DC is.

It is common to inject an AC signal into a battery to measure its impedance and then estimate its internal resistance. Unfortunately, this method is far from exact, as it depends largely on the frequency of the signal.

[goboatingnow]

More nonsense. The physical materials in a real world battery have very real "actual resistance".

Impedance is a strictly AC concept, and batteries do not normally operate under AC conditions. From a math standpoint, all the complex impedance components are all zero at zero frequency---which is what DC is.

It is common to inject an AC signal into a battery to measure its impedance and then estimate its resistance. Unfortunately, this method is far from exact, as it depends largely on the frequency of the signal.

You need far more study firstly on DC and secondly on batteries to make such statements. Have a read of first and second order modelling of batteries for some illumination. The DC system on your boat is not a static voltage, load dumps, transients, glitches, spikes etc are all there and dynamic response is essentially a form of AC ( there is in reality no AC or DC anyway, everything is dynamic).

More nonsense. The physical materials in a real world battery have very real "actual resistance".

of course they have a resistance, its just not constant thats all

voltage droop at a battery terminal is a function of chemical combination rates, but it can be modelled as an equivalent resistance, but its not an actual static value.