A DIY Power Wall ???

[Sunking]

Isn't that common knowledge? All other things being equal ... cycle life, from lowest to highest is ... FLA < AGM < Li-Ion < LiFePo ...

I mean ... you might be right in saying that FLA can have 1000 at 1/4 the cost ... but then doesn't a GOOD LFP have 3000-5000 cycles? Essentially, 4 times the cost for 4 times the life?

I'm definitely still learning, so am keen to see some good solid data on all of the battery options ... it's sometimes hard to separate the chaff from the wheat when it comes to data on batteries it seems?

If you were to bother to look at the actual battery manufacture specs, you would know only 1 claims to last 1000 cycles, while top of the line FLA batteries run as high as 5000 cycles. So much for make believe science.

The best LFP battery money can buy is A123 Systems, and they only claim 1000 cycles but fail to provide anything more than a 1 year warranty. A123 Systems batteries will run you $1.50 per watt hour. On the other hand a top of the line Trojan Industrial battery will provide 3000 cycles @ 80% DoD and comes with a 10-year warranty and cost on the order of $0.20 per watt hour.

So if you were to take say a 6-volt 400 AH Trojan Industrial battery gives you 2400 watt hours of capacity and will cost you roughly $500 with a 10-year warranty. Want that in a quality 6 volt 400 AH LFP battery? That will cost you $3600 plus you will need to fabricate a case and use an expensive BMS to make it work so in the end cost you about $4000 with a meaningless 1-year warranty.

So I say go for the LFP, you deserve it and will learn something.

[thastinger]

RE: The "fire" in message #12 ( two posts above )

What is the "fire code" for the Power Wall?
Must it be installed on a non-flammable wall - like brick?
What if it is mounted outside on a vinyl sided house with a wood substrate = major fire hazard?
The Insurance companies will have a problem with this increase risk.
They hate anything that increases their risk of lost profits, and rightly so.

Are these PowerWalls ever installed inside the home - in the living quarters? in the basement?
It look like a significant amount of toxic smoke & fumes were released.

If each cell is individually fused, then how did the first cell catch fire, as seen in message #12 ?
If the individual fuse did not blow then one or more the cell(s) overheated while operating at "normal" amps.
So then the Temperature Sensor, if there is one, failed too?
At some high temperature, the circuit should have opened and stopped all charging amps or discharging amps, long before the ignition point?
Is it possible for a cell to continue in thermal run-away, even after the circuit is opened?

You can't (cheaply) monitor the temperature of each and every cell, so this seems to be very risky in hot weather.

Does it make more sense, from a safety point of view (increased cost), for each cell to fully protect itself from volts, amps & heat ?
Then the manufacturer can add another layer of safety to the battery pack as whole.

If this passed inspection then it must be UL Approved".
I wonder how UL tested these battery packs?

Regardless of what "code" may say, by asking the question I assume you already know that it is a good idea or at least couldn't hurt. Since I'm only at my off-grid location, my CC and inverter are installed on a Durock sheet with an Durock cover, never hurts to go beyond code requirements.

[SunEagle]

Ignoring the obvious logical fallacy, I do understand your point ... though the logical fallacy is hard to ignore.

Again, actual hard data is useful to see.

If you compare the stated data from a battery manufacturers you can find that a slightly more expensive battery will yield a higher cycle rate then the cheaper battery. While that is not really hard data it is a starting point. On the other side, just because a manufacturer makes a statement on it's product that data is not always 100% true.

If you are looking for hard data your best bet is to perform the tests yourself. At least you know the data collected is true and not embellished by someone trying to sell you something.

[derekisastro]

The problem is all batteries can be abused which will shorten their life.

Would rather pay more for batteries that may die sooner then expected or less for batteries that have a good track record and will last as long as you designed for?

Ignoring the obvious logical fallacy, I do understand your point ... though the logical fallacy is hard to ignore.

Again, actual hard data is useful to see.

[SunEagle]

Isn't that common knowledge? All other things being equal ... cycle life, from lowest to highest is ... FLA < AGM < Li-Ion < LiFePo ...

I mean ... you might be right in saying that FLA can have 1000 at 1/4 the cost ... but then doesn't a GOOD LFP have 3000-5000 cycles? Essentially, 4 times the cost for 4 times the life?

I'm definitely still learning, so am keen to see some good solid data on all of the battery options ... it's sometimes hard to separate the chaff from the wheat when it comes to data on batteries it seems?

The problem is all batteries can be abused which will shorten their life.

Would rather pay more for batteries that may die sooner then expected or less for batteries that have a good track record and will last as long as you designed for?

[derekisastro]

Who told you that?

A good FLA battery can easily do over 1000 cycles, and cost 1/4 that of LFP.

Isn't that common knowledge? All other things being equal ... cycle life, from lowest to highest is ... FLA < AGM < Li-Ion < LiFePo ...

I mean ... you might be right in saying that FLA can have 1000 at 1/4 the cost ... but then doesn't a GOOD LFP have 3000-5000 cycles? Essentially, 4 times the cost for 4 times the life?

I'm definitely still learning, so am keen to see some good solid data on all of the battery options ... it's sometimes hard to separate the chaff from the wheat when it comes to data on batteries it seems?

[Paul Land]

Using iMax B6, each cycle takes at least 10 hours to complete. Multiply that by 20 sticks and you can quickly see that reconditioning the entire pack will take 25 days of round-the-clock reconditioning.

[Paul Land]

It's a great project. To have success you need to test and mate batts by using 1-100 Imax RC chargers.It takes charge/discharge cycling to restore batts memory it can take weeks to cycle for optimum memory. Once batts have balanced SOC there good to go. Any batts out of spec at this time are bad. ev charger.jpg

[Sunking]

Especially if you consider LiFePO4's ... the lifecycle there is huge?

Who told you that?

A good FLA battery can easily do over 1000 cycles, and cost 1/4 that of LFP.

[jflorey2]

That's a decent price! Are they flooded or AGM style? It seems that the 6V, 210Ah ones are flooded? Also, what's the cycle life on them? Maybe 3-500 cycles (best case scenario)?

Flooded. As SE mentions, you can get ~1000 cycles out of them if you baby them. On an installation down here I was getting ~600 cycles without too much babying. But keep in mind you will probably destroy them quickly as you learn.

The cycle life still potentially has implications for "cost"? I could see that with lithium, even used, the cycle life is some factor better than LA? Even a factor of just 2 or 3 times greater life cycle implies a 1/2 or 1/3 cost right? Though I guess this assumes that you can get 1000+ life cycles on lithium (possible if treated well?). . . . Especially if you consider LiFePO4's ... the lifecycle there is huge?

Again, getting 2000 potential cycles out of a battery doesn't mean much if you kill them after 100 cycles (due to overdischarge, bad BMS settings, charging while cold, uncorrected imbalance etc)

[SunEagle]

Especially if you consider LiFePO4's ... the lifecycle there is huge?

I believe the Trojan T105 have a cycle life of about 2000 to 50% DOD and I saw something about 1200 cycles for the Costco equivalent which isn't bad for low cost FLA type

[derekisastro]

Especially if you consider LiFePO4's ... the lifecycle there is huge?

[derekisastro]

Powerwall is about the cheapest out there, and it's still expensive.

If money is your concern, Costco T105's give you 1.3kwhr per battery for $100 each. And when you destroy them, 1) they will usually not catch on fire, 2) they will be easy to dispose of (lead recycling is a mature industry) and 3) they will be a very cheap way to learn.

That's a decent price! Are they flooded or AGM style? It seems that the 6V, 210Ah ones are flooded? Also, what's the cycle life on them? Maybe 3-500 cycles (best case scenario)?

The cycle life still potentially has implications for "cost"? I could see that with lithium, even used, the cycle life is some factor better than LA? Even a factor of just 2 or 3 times greater life cycle implies a 1/2 or 1/3 cost right? Though I guess this assumes that you can get 1000+ life cycles on lithium (possible if treated well?). Interesting things to calculate.

[jflorey2]

I know I am a little late to the party on this one but can you link some options? Or do you mean non-lithium based options that are cheaper? And even of the lithium options, are there cheaper new options or are you talking cheaper other used options?

Powerwall is about the cheapest out there, and it's still expensive.

If money is your concern, Costco T105's give you 1.3kwhr per battery for $100 each. And when you destroy them, 1) they will usually not catch on fire, 2) they will be easy to dispose of (lead recycling is a mature industry) and 3) they will be a very cheap way to learn.

[derekisastro]

The question is - why would you do that? There are plenty of batteries out there that are a lot cheaper than the above would cost.

I know I am a little late to the party on this one but can you link some options? Or do you mean non-lithium based options that are cheaper? And even of the lithium options, are there cheaper new options or are you talking cheaper other used options?

Thanks!