Using batteries instead of V2G

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alozzy

Well-known member
Joined
Jan 20, 2017
Messages
2,616
Location
Vancouver, BC
[MOD: This off-topic discussion split from https://mynissanleaf.com/viewtopic.php?f=37&t=32772&p=615034#p615034]


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BAsrican said:
Wow. How cool.

So is this modification going to remove/replace the CHAdeMO port, or will this add in an extra (3rd port) for more charging options? Just wondering, because I've heard cool things about future V2G capabilities that seem to rely on CHAdeMO, so it might be worth keeping it for that.

A decent quality LiFePO4 server rack battery pack, with BMS, can be purchased for under $300 per kWh now. These packs can be directly wired to an inverter, or connected together in parallel then connected to an inverter, for even more capacity. They also last way longer than lithium ion packs and are much safer.

For anyone who has time of use electric utility rates and wants to save money, the small investment needed to store enough electricity (ie 5 kWh) to take advantage of lower rates available during off peak hours is a no brainer.

These LiFePO4 packs are equally good as an emergency power source, as cheap and cleaner (and a lot less noisy) than a gas powered generator.

So, why bother with V2G, which will shorten the life span of the LEAF's pack?
 
alozzy said:
For anyone who has time of use electric utility rates and wants to save money, the small investment needed to store enough electricity (ie 5 kWh) to take advantage of lower rates available during off peak hours is a no brainer.

I'd like to see the math. Remember to include the installation and BOS costs
 
SageBrush said:
alozzy said:
For anyone who has time of use electric utility rates and wants to save money, the small investment needed to store enough electricity (ie 5 kWh) to take advantage of lower rates available during off peak hours is a no brainer.

I'd like to see the math. Remember to include the installation and BOS costs
Right. If this were truly economical you would see the electric utilities doing this at scale.
 
SageBrush said:
alozzy said:
For anyone who has time of use electric utility rates and wants to save money, the small investment needed to store enough electricity (ie 5 kWh) to take advantage of lower rates available during off peak hours is a no brainer.

I'd like to see the math. Remember to include the installation and BOS costs

Obviously, there's the additional cost of an inverter and transfer switch, etc but all-in-one units like the MPP Solar LV6548 make that pretty straight forward and reasonably inexpensive as a basic setup and even provide a solar charge controller. It helps to have a friend who's an electrician too, to inspect the work and provide free advice :)
 
alozzy said:
SageBrush said:
alozzy said:
For anyone who has time of use electric utility rates and wants to save money, the small investment needed to store enough electricity (ie 5 kWh) to take advantage of lower rates available during off peak hours is a no brainer.

I'd like to see the math. Remember to include the installation and BOS costs

Obviously, there's the additional cost of an inverter and transfer switch, etc but all-in-one units like the MPP Solar LV6548 make that pretty straight forward and reasonably inexpensive as a basic setup and even provide a solar charge controller. It helps to have a friend who's an electrician too, to inspect the work and provide free advice :)

Sorry, that is not a cost work-up that demonstrates that storage is a 'no brainer' compared to paying peak rates. Would you like to be more specific ? Like this:

Cost of hardware
Cost of storage
Cost of BOS
Cost of permitting and electrician
Savings of off-peak Vs peak per kWh
Cumulative kWh arbitraged over the life of the system
Opportunity cost/financing cost
 
SageBrush said:
alozzy said:
SageBrush said:
I'd like to see the math. Remember to include the installation and BOS costs

Obviously, there's the additional cost of an inverter and transfer switch, etc but all-in-one units like the MPP Solar LV6548 make that pretty straight forward and reasonably inexpensive as a basic setup and even provide a solar charge controller. It helps to have a friend who's an electrician too, to inspect the work and provide free advice :)

Sorry, that is not a cost work-up that demonstrates that storage is a 'no brainer' compared to paying peak rates. Would you like to be more specific ? Like this:

Cost of hardware
Cost of storage
Cost of BOS
Cost of permitting and electrician
Savings of off-peak Vs peak per kWh
Cumulative kWh arbitraged over the life of the system
Opportunity cost/financing cost

Put in the time yourself if you want to figure that out, if you are genuinely interested. I know you aren't though, because you are only interested in trolling here to get a rise out of people. I'm not going to bite this time, I'm tired of dealing with you.
 
alozzy said:
SageBrush said:
Sorry, that is not a cost work-up that demonstrates that storage is a 'no brainer' compared to paying peak rates. Would you like to be more specific ? Like this:

Cost of hardware
Cost of storage
Cost of BOS
Cost of permitting and electrician
Savings of off-peak Vs peak per kWh
Cumulative kWh arbitraged over the life of the system
Opportunity cost/financing cost

Put in the time yourself if you want to figure that out, if you are genuinely interested. I know you aren't though, because you are only interested in trolling here to get a rise out of people. I'm not going to bite this time, I'm tired of dealing with you.
You convinced me. You do not know wtf you are talking about.
 
I will take a stab at the calculation using my time-of-use with demand charge residential rates:
Assume 5 kW air conditioner load to run without drawing peak power (5 hours on peak each weekday at 50% duty cycle):

5 kW * 2.5 hrs = 12.5 kWh
12.5 kWh * $300/kWh = $3,750 for battery purchase plus say $3,000 for inverter/charger system yields estimated $6,750 purchase cost without considering permit and installation fees

Assume summer demand charge of $20/kW (1 hour peak demand) and difference between on-peak and off-peak energy rate of $0.02/kWh ($0.08/kWh on peak and $0.06/kWh off peak). Demand reduction of 5 kW would save $100 per month. At 90% round trip efficiency for inverter and charger system (probably less than that realistically), 13.9 kWh off peak energy would be required to replace the 12.5 kWh on peak energy used each day.
13.9 kWh * $0.06 = $0.83 per day energy cost off peak
12.5 kWh * $0.08 = $1.00 per day energy cost on peak
22 days * $0.17 = $3.74 per month in reduced energy cost so total cost saving would be $103.74 per month
$6750 / $103.74 = 65.07 months
Without including interest on investment or operation/maintenance cost it would take over 65 summer months to break even. My winter demand charges are lower and there is no need for heating during late afternoon/early evening so there would be no saving during those months. Therefore, it would take almost 11 years for me to break even assuming there were no equipment repair/replacement costs and the interest rate was 0%. This also assumes full discharge cycles of the battery so actual battery capacity would need to be larger.

(Edited to change from 30 days to 22 days on peak per month since weekends are off peak.)
 
Really though. Why not use AGM batteries. They are a fraction of the cost. Not sure how it would pay out in the long run.

We have a 2 KW UPS with AGM batteries for critical loads like fridge and entertainment centre and furnace motor. We use a 2 KW inverter/charger. It is pass through so always online. BC hydro is the same price all day so no advantage other than backup. Works well though.
 
webeleafowners said:
Really though. Why not use AGM batteries. They are a fraction of the cost. Not sure how it would pay out in the long run.

We have a 2 KW UPS with AGM batteries for critical loads like fridge and entertainment centre and furnace motor. We use a 2 KW inverter/charger. It is pass through so always online. BC hydro is the same price all day so no advantage other than backup. Works well though.
I can say from experience that even the best AGM batteries won't last long enough with daily use, but work fine for backup power that is used occasionally. I've had a solar / wind mill setup for over a decade now and I'm still on the original LiFePO4 batteries I started with. AGM batteries have a cycle life in the low hundreds and unless you buy enough to fill a house, you can't get enough cycle life to make the investment worthwhile for energy storage. The AGM batteries (when a lot were still made in the USA) I purchased would last about 1 to 2 years before going bad (cycle life limitation). I got them replaced under a 3 year warranty, but they only lasted another 2 years and warranty wasn't going to replace them again. The LiFePO4 batteries are still in use today with about 80% of their original capacity still.
 
And, of course, the AGM batteries are limited to providing roughly 50% of their rated capacity, while the lithium batteries can provide 80% of their rated capacity, with little or no harm.
 
knightmb said:
webeleafowners said:
Really though. Why not use AGM batteries. They are a fraction of the cost. Not sure how it would pay out in the long run.

We have a 2 KW UPS with AGM batteries for critical loads like fridge and entertainment centre and furnace motor. We use a 2 KW inverter/charger. It is pass through so always online. BC hydro is the same price all day so no advantage other than backup. Works well though.
I can say from experience that even the best AGM batteries won't last long enough with daily use, but work fine for backup power that is used occasionally. I've had a solar / wind mill setup for over a decade now and I'm still on the original LiFePO4 batteries I started with. AGM batteries have a cycle life in the low hundreds and unless you buy enough to fill a house, you can't get enough cycle life to make the investment worthwhile for energy storage. The AGM batteries (when a lot were still made in the USA) I purchased would last about 1 to 2 years before going bad (cycle life limitation). I got them replaced under a 3 year warranty, but they only lasted another 2 years and warranty wasn't going to replace them again. The LiFePO4 batteries are still in use today with about 80% of their original capacity still.

Well that’s informative. I think what you are saying is that in my use as backup storage they are a good choice, but as a daily cycle kind of use Lifepo4 is a better way to go. Yes?

Thanks.
 
Well that’s informative. I think what you are saying is that in my use as backup storage they are a good choice, but as a daily cycle kind of use Lifepo4 is a better way to go. Yes?

Yes, that's what we both are saying. LiFePo4 batteries are very stable and long-lived if not abused. If you use them, though, you have to re-learn the voltage chart, because the lower middle of the lead-acid voltage range is "near dead" and "dead" for LFP batteries. 12.8 volts is the lowest you want to run them for any length of time. That means they need a LFP-specific charger and/or maintainer. I will be trying the "Noco Genius" smart maintainer on my new LiFePo4 sump pump battery. It's supposed to provide a higher voltage for lithium batteries. I'll post the results next year. I'm hoping that it will keep the battery at about 90% SOC, instead of the 100% that the charger that came with the battery provides.
 
I wasn't actually talking about a full blown off grid solar project, but this will put the ROI in perspective:

https://www.youtube.com/watch?v=m8R6TeTkb5k
 
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