Tenergy batteries

[extrafu]

Hello,

Anyone has experience with Tenergy LiFePO4 batteries? Their 3.2V 130Ah is quite well priced (at 150$ per battery).

Their specs seem along the lines of others: http://www.all-battery.com/datasheet/30265_DS.pdf

Thanks!

[SunEagle]

If you do the math on that battery a 12volt system would require 4 of those 130Ah 3.2v units at $150 each or $600 total

The life span is rated at 2000 cycles using 80% capacity for each cycle. So that is 130Ah x 80% x 12v = 1250 watt hours for each cycle.

If you get 2000 cycles that comes to 2000 x 1250 wh / 1000 = 2500kWh.

So the cost to generate power from that system is roughly $600 / 2500kWh ~$0.24/kWh.

Now that price of $600 does not include a charger, panels, racking, inverter, wiring, overcurrent protection and misc hardware but at least the batteries could be worth it if you can off set a higher cost / kWh than that calculated 24 cents/ kWh.

[extrafu]

Thanks SunEagle for your answer! I agree with your math - but this is for a completely off-grid house + garage - where bringing electricity would cost about 50K$...

[Wy_White_Wolf]

$150 / (3.2v * 130AH)= $360 per KWH of storage.

I can get Trojan L-16s for about $320

$320 / (6V * 420AH) = $127 per KWH of storage

How is that reasonably priced?

WWW

[SunEagle]

Thanks SunEagle for your answer! I agree with your math - but this is for a completely off-grid house + garage - where bringing electricity would cost about 50K$...

I agree that $50k is a little hard to swallow but unless the price of batteries comes way down you can eat up a lot of money every 5 years due to having to replace that system.

Each person needs to perform their own calculations when it comes to using a solar / battery off grid system or connect to the grid.

At today's prices an off grid system that covers the electrical needs of most families needs may cost close to $100k initially and then the added cost to replace the battery system every 5 years.

[extrafu]

I agree that $50k is a little hard to swallow but unless the price of batteries comes way down you can eat up a lot of money every 5 years due to having to replace that system.

Each person needs to perform their own calculations when it comes to using a solar / battery off grid system or connect to the grid.

At today's prices an off grid system that covers the electrical needs of most families needs may cost close to $100k initially and then the added cost to replace the battery system every 5 years.

Yep - I know I must be careful. I estimate the equipment cost at about 40k$ for having a complete off-grid system, including labor to put that in place. That excludes the generator and heating system which would be required even if I go grid-tie. I do NOT anticipate spending 40k$ and being done with it for many years. I expect that what I would normally pay to the power company will be spent on system maintenance and updates (new batteries, replacing broken panels, MPPT inverters, etc.) over time.

Of course I don't have yet any experience but I don't think I would need to replace all batteries every 5 years. Some of them, sure thing. I plan to use about 7 to 8kWh per day, and I plan on having a 27kWh battery bank. If I aim for 70% DOD, that is 19kWh of usable power, almost 3 days. I plan to have enough solar panels to charge the whole bank in one sunny day. 70% DOD usually increases the lifespan to 3000 cycles.

Say at worst I go 70% DOD every 2 days, that gives me 6000 days in front of me or a bit more than 16 years.

Of course, all that is numbers based on manufacturers specifications... time will tell me

[SunEagle]

Yep - I know I must be careful. I estimate the equipment cost at about 40k$ for having a complete off-grid system, including labor to put that in place. That excludes the generator and heating system which would be required even if I go grid-tie. I do NOT anticipate spending 40k$ and being done with it for many years. I expect that what I would normally pay to the power company will be spent on system maintenance and updates (new batteries, replacing broken panels, MPPT inverters, etc.) over time.

Of course I don't have yet any experience but I don't think I would need to replace all batteries every 5 years. Some of them, sure thing. I plan to use about 7 to 8kWh per day, and I plan on having a 27kWh battery bank. If I aim for 70% DOD, that is 19kWh of usable power, almost 3 days. I plan to have enough solar panels to charge the whole bank in one sunny day. 70% DOD usually increases the lifespan to 3000 cycles.

Say at worst I go 70% DOD every 2 days, that gives me 6000 days in front of me or a bit more than 16 years.

Of course, all that is numbers based on manufacturers specifications... time will tell me

Maybe. I would not bank on expecting any battery to last for 6000 cycles. But hey it is your money. Good luck.

[extrafu]

Maybe. I would not bank on expecting any battery to last for 6000 cycles. But hey it is your money. Good luck.

It might be a stupid question but how to properly interpret a cycle? Say (hypothetically) it takes 50 minutes to go 80% DOD and 10 minutes to charge a battery, that is 24 cycles per day. With 2,000 cycles at 80% DOD, in 3 months the battery is toasted based on the specs. But what happens when it takes 2 days to go to 80% DOD?

[jflorey2]

Of course I don't have yet any experience but I don't think I would need to replace all batteries every 5 years. Some of them, sure thing.

Generally it is a very bad idea to just replace some batteries in a lead acid battery bank.

I plan to use about 7 to 8kWh per day, and I plan on having a 27kWh battery bank. If I aim for 70% DOD, that is 19kWh of usable power, almost 3 days. I plan to have enough solar panels to charge the whole bank in one sunny day. 70% DOD usually increases the lifespan to 3000 cycles.

Say at worst I go 70% DOD every 2 days, that gives me 6000 days in front of me or a bit more than 16 years.

Doesn't quite work like that. Even batteries that are floated forever (never cycled) die over time. That's why UPS systems need regular battery replacements even if they are never used.

[extrafu]

Generally it is a very bad idea to just replace some batteries in a lead acid battery bank.

I plan on using LiFePO4 batteries. What you said might apply as well.

Thanks!

[extrafu]

I found this interesting piece of information from Apple's website (http://www.apple.com/uk/batteries/why-lithium-ion/) about Lithium ion batteries and cycles. I know it's the same as LiFePO4 but what they say is interesting: "For instance, you might use 75 per cent of your battery’s capacity one day, then recharge it fully overnight. If you use 25 per cent the next day, you will have discharged a total of 100 per cent, and the two days will add up to one charge cycle."

[jflorey2]

I found this interesting piece of information from Apple's website (http://www.apple.com/uk/batteries/why-lithium-ion/) about Lithium ion batteries and cycles. I know it's the same as LiFePO4 but what they say is interesting: "For instance, you might use 75 per cent of your battery’s capacity one day, then recharge it fully overnight. If you use 25 per cent the next day, you will have discharged a total of 100 per cent, and the two days will add up to one charge cycle."

Again, lithium ion batteries die over time. Even if you never discharge it, the battery will not last 10 years.

[SunEagle]

It might be a stupid question but how to properly interpret a cycle? Say (hypothetically) it takes 50 minutes to go 80% DOD and 10 minutes to charge a battery, that is 24 cycles per day. With 2,000 cycles at 80% DOD, in 3 months the battery is toasted based on the specs. But what happens when it takes 2 days to go to 80% DOD?

A cycle is usually defined as a 24 hour period.

Even if it took you 2 days to go to 80% DOD the battery is still slowly dying because it is not fully charged. For that matter once a battery is sold the life's clock starts to tick. How it is charged and discharged can help you get more than the MFG stated cycle life but unless you have purchased a very big battery system for a very small load the chances are when the days or "cycles" add up to full your batteries will not be able to get back to 100% nameplate charge. Sure it will still work but it is considered used up per the MFG.

Maybe someday a battery will be able to live for 4000 cycles using 80% of its nameplate charge but as far as I have heard no one has made a battery yet to live that long under "real life" conditions.

[extrafu]

A cycle is usually defined as a 24 hour period.

Even if it took you 2 days to go to 80% DOD the battery is still slowly dying because it is not fully charged. For that matter once a battery is sold the life's clock starts to tick. How it is charged and discharged can help you get more than the MFG stated cycle life but unless you have purchased a very big battery system for a very small load the chances are when the days or "cycles" add up to full your batteries will not be able to get back to 100% nameplate charge. Sure it will still work but it is considered used up per the MFG.

Maybe someday a battery will be able to live for 4000 cycles using 80% of its nameplate charge but as far as I have heard no one has made a battery yet to live that long under "real life" conditions.

Lithium titanate cells maybe? One thing I have faith in is technology keeps improving, costs around it keeps going down so if my pack lasts 10 years, most likely by then far better technologies at the right price will be available. After all, LiFePO4 batteries were virtually non-existent 5 years ago.

[SunEagle]

Lithium titanate cells maybe? One thing I have faith in is technology keeps improving, costs around it keeps going down so if my pack lasts 10 years, most likely by then far better technologies at the right price will be available. After all, LiFePO4 batteries were virtually non-existent 5 years ago.

I also hope that better battery technology is discovered and marketed for much less than what is available now. More than likely it will be some chemistry with Lithium involved.