Announcement

Collapse
No announcement yet.

Batteries connection

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • lkruper
    replied
    Originally posted by inetdog View Post
    You are going down a useful road, but you are being careless with your units, which will make the results less useful to others.
    You are trying to calculate the cost per kWh not per kW. If you make that change pretty much globally in all your posts on the subject it will help.

    Also, you need to make sure that those two Trojan batteries can deliver the power you need (in kW) and the energy you need daily (in kWH) before the comparison is complete.
    What depth of discharge are you using per cycle? And are those 6V or 12V batteries?
    Ah, I see you did add that information.
    You used 50% DOD. I have a hard time believing that you will still get 1200 cycles at that DOD in real world use, but Trojan should be pretty trustworthy and there has been time for them to run those actual tests rather than extrapolating the results.

    50% DOD for loads over, say, a 5 hour period, is going to discharge the battery at an average rate consistent with C[SUB]10[/SUB] rather than C[SUB]20[/SUB], so Sunking's point is well taken.

    And you have neglected to allow for the fact that you must put back more energy into the batteries than you take out (and are paying for, even if at the night rates) and are limited in available solar hours, so recharging from 50% DOD in one day is not going to happen either with solar, but could happen with storage.

    If your super off peak rate is .11 per kWh and you have to overbuy by 120%, and your battery storage cost is .17 per kWh then the sell back rate would have to be .11 x 1.2 + .17 = 30.2 (or higher) to make it worthwhile.
    Thanks, that is not the first time I have shortened kWh to kW. I have fixed my posts. I got the 1200 from the link Sunking gave me at -> http://www.trojanbattery.com/markets...ble-energy-re/ I agree that there is risk in batteries, however in this case, since the batteries will be charged with grid power at night, the recharging is not dependent upon the weather and should be quite reproducible.

    My point also was not that the numbers are dependent upon 2 T105s but to make the calculation easier to follow. It should be scalable to any size battery bank.

    I agree that I have not fine tuned the analysis to account for charging and inverter inefficiencies, but I am rather taken aback at how much SCE would be charging me for TOU during peak times as well as how little they charge at below baseline at night, effectively 1 cent per kWh.

    Initially my goal was to show that if one cherry picks the highest rates with a small system, that the batteries could be more than paid for by the difference. Now I am not sure if that is the extent of it. It may be that more of a system could at least break even depending on the load with the desired benefit of also ending up with a UPS of sorts for a good portion of a residence, paid for by the difference in TOU rates. After all, the delta is '46 cents - battery cost' up to the baseline.

    A simple system might be:
    [LEFT]
    Timer -> Charger -> Battery Bank -> Inverter -> transfer switch - > electrical panel

    where the timer only runs the Charger at the time period of the lowest rate. [/LEFT]

    I will probably look at more specifics in either my home or cabin to see if it really makes sense for me to consider this at all.

    ###
    Found Trojan T-105-RE on sale in San Diego for $125. That calculates to 11.57 cents / kWh. It is of interest that even Industrial does not have as good a price ratio (eg IND17-6V @ 17 cents / kWh)
    ###

    $$$
    Added Cost for Inverter and Charger (prorated them for 10 years - $744) so that now the cost per kWh is 12.44 cents. This is based on a sale price if T-106-RE at $125
    $$$

    ###
    My baseline is 13.8 kWh which for TOU would allow charging for 10 hours at 1 cent / kWh. This brings the cost of battery-produced power to 13.44 cents / kWh
    ###

    My tier 1 is 14.496 kWh. This gives me a surplus of about 1 cent / kWh.

    My conclusion is that the risk of premature failure of batteries or electronics outweighs any slight cost benefit and does not compensate for the labor of battery maintenance.

    Leave a comment:


  • inetdog
    replied
    Originally posted by lkruper View Post
    It's NOT something I am terribly interested in doing, but I calculate that 2 Trojan 105 batteries cost $280 and if they give 1200 cycles will produce 1620 kW in their lifetime. That comes out to 0.17 per kW. I am still checking my calculations, but at my baseline I can get a kW at 0.01 and use it during the day when it would cost me 0.46 or at 0.30. Still checking my calcs....
    You are going down a useful road, but you are being careless with your units, which will make the results less useful to others.
    You are trying to calculate the cost per kWh not per kW. If you make that change pretty much globally in all your posts on the subject it will help.

    Also, you need to make sure that those two Trojan batteries can deliver the power you need (in kW) and the energy you need daily (in kWH) before the comparison is complete.
    What depth of discharge are you using per cycle? And are those 6V or 12V batteries?
    Ah, I see you did add that information.
    You used 50% DOD. I have a hard time believing that you will still get 1200 cycles at that DOD in real world use, but Trojan should be pretty trustworthy and there has been time for them to run those actual tests rather than extrapolating the results.

    50% DOD for loads over, say, a 5 hour period, is going to discharge the battery at an average rate consistent with C[SUB]10[/SUB] rather than C[SUB]20[/SUB], so Sunking's point is well taken.

    And you have neglected to allow for the fact that you must put back more energy into the batteries than you take out (and are paying for, even if at the night rates) and are limited in available solar hours, so recharging from 50% DOD in one day is not going to happen either with solar, but could happen with storage.

    If your super off peak rate is .11 per kWh and you have to overbuy by 120%, and your battery storage cost is .17 per kWh then the sell back rate would have to be .11 x 1.2 + .17 = 30.2 (or higher) to make it worthwhile.
    Last edited by inetdog; 09-25-2015, 12:37 AM.

    Leave a comment:


  • lkruper
    replied
    Originally posted by Sunking View Post
    Are you assuming Peukert losses. You loads can never exceed 130 watts or 11 amps of battery current at any time. That same 225 AH battery is 140 AH at C/6.
    The calculation was done to simply show the cost per kWh of 17 cents. I can charge at night for 1 cent per kWh and discharge during peak hours when it would cost me 46 cents per kWh.
    Last edited by lkruper; 09-25-2015, 12:19 PM. Reason: Mistake on cycles for L16RE-2V removed

    Leave a comment:


  • Sunking
    replied
    Originally posted by lkruper View Post
    I am still checking my calculations, but:

    Trojan T-105 get 1200 cycles @ 50% DOD
    Cost of 2 batteries = $280
    At 50% DOD the bank gives 1.35 kW / day
    1.35 kW X 1200 cycles = 1620 kW lifetime
    $280 / 1620 kW = 17 cents / kW

    Did I do that right?
    Are you assuming Peukert losses. You loads can never exceed 130 watts or 11 amps of battery current at any time. That same 225 AH battery is 140 AH at C/6.

    Leave a comment:


  • lkruper
    replied
    Originally posted by Sunking View Post
    So what. Battery power will cost you 60-cents and higher per Kwh in the USA.

    Taking the case to Hawaii where electricity cost more does not wash either. Yep electricity cost twice as much as the mainland in Hawaii, so do the batteries, panels, controllers, racking, wiring and everything else. Same piss poor scale you cannot win.
    I am still checking my calculations, but:

    Trojan T-105 get 1200 cycles @ 50% DOD
    Cost of 2 batteries = $280
    At 50% DOD the bank gives 1.35 kWh / day
    1.35 kWh X 1200 cycles = 1620 kWh lifetime
    $280 / 1620 kWh = 17 cents / kWh

    Did I do that right?
    Last edited by lkruper; 09-25-2015, 12:56 AM. Reason: Fixed units ... kW to kWh

    Leave a comment:


  • Sunking
    replied
    Originally posted by lkruper View Post
    My tiers are 0.15, 0.19, 0.26 and 0.31. When we get +100 temps for a month or more in a row, I make it into tier 4.
    So what. Battery power will cost you 60-cents and higher per Kwh in the USA.

    Taking the case to Hawaii where electricity cost more does not wash either. Yep electricity cost twice as much as the mainland in Hawaii, so do the batteries, panels, controllers, racking, wiring and everything else. Same piss poor scale you cannot win.

    Leave a comment:


  • lkruper
    replied
    Originally posted by paulcheung View Post
    If the battery cost $0.50 per kwh, how do you save money even if you get the night energy for free? What we try to do is load shifting, we use a lot of power when the sun is shinning and use very little at night so the battery bank don't have to be as large as it should and therefor cut down the cost of the battery per kwh.

    It's NOT something I am terribly interested in doing, but I calculate that 2 Trojan 105 batteries cost $280 and if they give 1200 cycles will produce 1620 kW in their lifetime. That comes out to 0.17 per kW. I am still checking my calculations, but at my baseline I can get a kW at 0.01 and use it during the day when it would cost me 0.46 or at 0.30. Still checking my calcs....

    Leave a comment:


  • paulcheung
    replied
    Originally posted by lkruper View Post
    I am trying to understand the CA TOU from SCE, and it looks like in the lowest tier the cost is 11 cents / kW but with baseline it is minus 10 cents so that the cost is 1 cent per kW (at night). So my cost to run a theoretical 100w load during waking hours (say 14) is $15.00 per month and virtually free if all run at the lowest tier. So if I could charge batteries at night and run during the day I can offload the cost. That is 42 kW per month.
    If the battery cost $0.50 per kwh, how do you save money even if you get the night energy for free? What we try to do is load shifting, we use a lot of power when the sun is shinning and use very little at night so the battery bank don't have to be as large as it should and therefor cut down the cost of the battery per kwh.

    Leave a comment:


  • lkruper
    replied
    Originally posted by SunEagle View Post
    I see that can get expensive even getting power from your POCO.

    Still I would point out that the cost of an energy storage system cost may be a lot more then compared to finding low priority items in your home to turn off so you get back to a lower tier would be much less expensive.

    It comes down to which is the highest priority. Being able to run all your electrical equipment when you want to or saving money on your electric bill.

    I am not saying turning off electrical appliances would be easy but if the high cost of an electric bill is hard to handle then maybe not running all the tvs, lights and AC system at the same time is something that could be handled.
    I am trying to understand the CA TOU from SCE, and it looks like in the lowest tier the cost is 11 cents / kW but with baseline it is minus 10 cents so that the cost is 1 cent per kW (at night). So my cost to run a theoretical 100w load during waking hours (say 14) is $15.00 per month and virtually free if all run at the lowest tier. So if I could charge batteries at night and run during the day I can offload the cost. That is 42 kW per month.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by lkruper View Post
    My tiers are 0.15, 0.19, 0.26 and 0.31. When we get +100 temps for a month or more in a row, I make it into tier 4.
    I see that can get expensive even getting power from your POCO.

    Still I would point out that the cost of an energy storage system cost may be a lot more then compared to finding low priority items in your home to turn off so you get back to a lower tier would be much less expensive.

    It comes down to which is the highest priority. Being able to run all your electrical equipment when you want to or saving money on your electric bill.

    I am not saying turning off electrical appliances would be easy but if the high cost of an electric bill is hard to handle then maybe not running all the tvs, lights and AC system at the same time is something that could be handled.

    Leave a comment:


  • lkruper
    replied
    Originally posted by SunEagle View Post
    I agree. That for some people in the US, like Hawaii and CA the cost of electric at the higher tiers make energy storage look better. But for most of the US the cost of storage is still way too high except if you are totally off grid and then it doesn't matter since you can't purchase from a POCO.

    If energy storage is important then finding the right chemistry (including LiFePO4) should be considered as long as you take into account the cost and longevity of the system.
    My tiers are 0.15, 0.19, 0.26 and 0.31. When we get +100 temps for a month or more in a row, I make it into tier 4.

    Leave a comment:


  • SunEagle
    replied
    Originally posted by lkruper View Post
    I think there may be some circumstances where batteries could make sense in a very limited scope. Say for example if someone is getting into the higher tiers during the month because of air conditioning in a hot climate. If they had a very small system that was primarily used for backup and then generated power during times when they would be reducing tier4, a case could be made for recouping the money. But I agree, there is no way to generate one's own power cheaper, on the average, than the POCO.

    What do you think?
    I agree. That for some people in the US, like Hawaii and CA the cost of electric at the higher tiers make energy storage look better. But for most of the US the cost of storage is still way too high except if you are totally off grid and then it doesn't matter since you can't purchase from a POCO.

    If energy storage is important then finding the right chemistry (including LiFePO4) should be considered as long as you take into account the cost and longevity of the system.

    Leave a comment:


  • lkruper
    replied
    Originally posted by SunEagle View Post
    I just did the calculation with only the battery cost. There is also the cost of the pv panels, battery charger, DC to AC inverter along with cabling and fusing. So the up front cost will be much more than 3 times the cost of purchasing power from my utility. And a 200Ah battery may cost me only $300 today it will be more in 5 years. The costs keep adding up.

    I am lucky because my power quality is pretty good. But the chance of it stopping is high during bad weather. Then I would use an emergency generator which will provide me much more power than a battery system for much less cost including the fuel to run it.

    You may have a different situation with your electric cost and power quality but in my opinion you will still end up spending a lot more for a solar/battery system then just purchasing power from your utility.
    I think there may be some circumstances where batteries could make sense in a very limited scope. Say for example if someone is getting into the higher tiers during the month because of air conditioning in a hot climate. If they had a very small system that was primarily used for backup and then generated power during times when they would be reducing tier4, a case could be made for recouping the money. But I agree, there is no way to generate one's own power cheaper, on the average, than the POCO.

    What do you think?

    Leave a comment:


  • PNjunction
    replied
    OH kill me now!

    In one paragraph, you've just pushed about 40 of my hot-buttons with speculative investor-bait. It's all been covered before in other threads.

    Why does everyone feel like it's ok to [b]derail a subforum for lifepo4[/b] with every other conceivable chemistry out there?

    It's rude, and quite frankly BORING.

    Leave a comment:


  • jkirkebo
    replied
    Originally posted by Sunking View Post
    Batteries are a very mature product. It is called inflation. Anything you buy today will cost more 5 years from now.
    FLA and AGM is a mature product. Not much happening in LiFePO4 either. But the cost for the other lithium-chemistries (NCA,NMC etc.) is dropping like a rock. The PowerWall is introduced at $3000 for the daily cycle version, my guess is that this price will be halved in a few years and larger versions being available for even lower price per kWh. Competitors are launching similar products in spades. Mainly targeted at grid-tie applications but surely off-grid users will move in the same direction.

    In 10 years I doubt anyone will be buying new lead acid banks.

    Leave a comment:

Working...
X