Aquion Energy up and coming battery....opinions please

[northerner]

Sizing for Aquion Batteries

Sizing an off grid system for Aquion batteries should work out to be fairly close to sizing for flooded lead acid batteries. You would size your bank for an average daily depth of discharge of between about 20 to 50 percent DOD, depending on individual preferences.

For example: if you require a 20 kwh bank of lead acid batteries to run your system, a 20 kwh bank of AHI batteries should also be sufficient to run your system. The only case where you may decide to oversize the storage a little more, is if you have very peak loads or very high peak charging currents. For many off grid systems, that shouldn't apply.

Also, battery life at 25% DOD per day works out to be very close to that where you discharge to 50% over 2 days, or 75% over 3 days for that matter. Overall battery life is based on calendar life, not just cycle life. When you go to 75% DOD, your getting 3 days use whereas at 25% DOD, only 1 day use.

[northerner]

You keep moving the target, which makes it very difficult to have a discussion. A few posts back you were talking about designing for 25-50% DOD. And well you should be - you suggested earlier I believe that at 25%, AHI goes 12,000 cycles. At 80% it is 4000 cycles. So I went for the gold ring - 25% DOD.

Let's take your route and go 50% DOD at two days of autonomy. What will that cost me, $35,000-40,000 for 6000 pounds of batteries? Now this is an improvement. And my generator run time will be 8 hours every two days. Unacceptable. Not an option today. Will it live to see another day? There is no way to tell right now. If you are willing to take a gamble, I wish you luck.

I was referring to daily DOD and the cost for various depth of discharges is quite linear, so makes it little difference to the overall life versus how much usage the bank sees.

When you size a bank, you always use the daily average DOD for your calculations. But, you also need to consider the maximum DOD when looking at various battery chemistry's.

With lead acid you generally target a 20-30% daily depth of discharge and many will take the bank only to 50% DOD. Occasionally you can take it down to 80% DOD, but will affect overall battery life if done on a regular basis.

With AHI batteries, a 25-50% daily depth of discharge is quite desirable. Depends on how much autonomy you want, and what your loads and charging currents are? You can go to about 80% DOD without affecting the overall life significantly (unlike FLA's) on a regular basis.

Look again at the calculations I made for you in the previous post. This bank (stack of 16) S20 batteries should give you an average 25% daily DOD. You still have 3 days of autonomy, as you can take it down to about 80% DOD total. Total cost is $18400, not anywhere near the $35-40,000 your mentioning. At an average daily DOD, you should get about 12,000 cycles (to 80% capacity) overall, despite the fact that you use the 3 days of autonomy. It would still average about 25% DOD per day!

With 16 stacks you can charge with the generator (or solar) at anywhere up to 9.5 amps per stack x 16 stacks = 152 amps x 48 volts = over 7,200 watts. So this pack would be able to accept 152 amps of charging current, which is sufficient to get it recharged in a reasonable time.

[Living Large]

A 25% DOD daily does give you 3 days of autonomy, as that will allow you to go down to 75% DOD total.

Ri will affect the efficiency with heavier currents. Only the difference in efficiency will be a factor in increasing generator run time, and would be negligible as mentioned if you sized your battery accordingly.

You keep moving the target, which makes it very difficult to have a discussion. A few posts back you were talking about designing for 25-50% DOD. And well you should be - you suggested earlier I believe that at 25%, AHI goes 12,000 cycles. At 80% it is 4000 cycles. So I went for the gold ring - 25% DOD.

Let's take your route and go 50% DOD at two days of autonomy. What will that cost me, $35,000-40,000 for 6000 pounds of batteries? Now this is an improvement. And my generator run time will be 8 hours every two days. Unacceptable. Not an option today. Will it live to see another day? There is no way to tell right now. If you are willing to take a gamble, I wish you luck.

EDIT I realized after I went to do something else I had made an error, and simply changed 3 days of autonomy to 2 at 25% DOD. If I want to go to 50% DOD, and I used the suggested 16 stacks at around $18-19,000 I would cut my available cycles from 12,000 to 6000, and have to charge every other day instead of every 3 days for about 9 hours. It still is not feasible.

[northerner]

If I were confusing stacks and modules, my numbers would differ a lot more. I need 3 days of autonomy. 3 x $18,400 = $55,200. The only difference between my $45,000 and $55,200 is I was cheating and using 3 of their standard module of *12* stacks, which I was quoted something like $15,000 to have shipped.

By your calculations, I am looking at over 2 tons of battery. By mine, 4-1/2 tons. Either way I think that is roughly an order of magnitude larger than LFP.

I have made it crystal clear why I am concerned about Ri. Generator run time - very important for an off-grid application. I never mentioned large loads.

A 25% DOD daily does give you 3 days of autonomy, as that will allow you to go down to 75% DOD total.

Ri will affect the efficiency with heavier currents. Only the difference in efficiency will be a factor in increasing generator run time, and would be negligible as mentioned if you sized your battery accordingly.

[Living Large]

It sounds like your mixing stacks with modules. If your daily usage is 150 ah per day, at 48 volts is 7.2 kwh per day. One Aquion S20 stack, which retails for $1150 US, will provide 2.36 kwh per day. If you factor in the 85% return efficiency plus inverter loss it would be 2.36 kwh x 0.85 RTE x 0.90 inverter loss = 1.8 kwh. One stack will provide 1.8 kwh of usable energy at a 20 hour rate.

So for 7.2 kwh to equal 25% DOD, 7.2 kwh/ 0.25 = 28.8 kwh total usable. Thus you would need 28.8 kwh/1.8 kwh = 16 stacks total x $1150 = $18,400 cost for the bank to give you an average 25% DOD per day.

If you put in only 4 amps per stack, that is 4 x 16 = 64 amps @ 48volts which is over 3000 watts. At 4 amps per stack the RTE (round trip efficiency) is over 85%. For the maximum loads it would be about the same as the maximum charging current. You could go to 9.5 amps per stack x 16 = 152 amps max @ 40v = about 6000 watts max for input with solar and for load handling. Note that RTE drops to a little over 70%, and this is where the internal resistance factors in.

These batteries are not meant to handle really heavy loads or charging currents, but if you size the bank properly, should work for many off grid users.

If I were confusing stacks and modules, my numbers would differ a lot more. I need 3 days of autonomy. 3 x $18,400 = $55,200. The only difference between my $45,000 and $55,200 is I was cheating and using 3 of their standard module of *12* stacks, which I was quoted something like $15,000 to have shipped.

By your calculations, I am looking at over 2 tons of battery. By mine, 4-1/2 tons. Either way I think that is roughly an order of magnitude larger than LFP.

I have made it crystal clear why I am concerned about Ri. Generator run time - very important for an off-grid application. I never mentioned large loads.

[northerner]

OK, I am just about done here. I will use about 150Ah a day. At 25%, I need an 0082 bank for each day. That is 3 banks, at $15,000 a bank. Each one weighs 3100 pounds. So I need to spend $45,000 for 9,300 pounds of battery.

If that isn't daunting enough, let's see what happens every 3 days. I need to put in 450 Ah. According to Dereck's analysis, I can charge these 3 banks at maybe 40A. That is 11 hours.

All this at a price of $45,000. Did you see internal resistance in the Aquion specs?

It sounds like your mixing stacks with modules. If your daily usage is 150 ah per day, at 48 volts is 7.2 kwh per day. One Aquion S20 stack, which retails for $1150 US, will provide 2.36 kwh per day. If you factor in the 85% return efficiency plus inverter loss it would be 2.36 kwh x 0.85 RTE x 0.90 inverter loss = 1.8 kwh. One stack will provide 1.8 kwh of usable energy at a 20 hour rate.

So for 7.2 kwh to equal 25% DOD, 7.2 kwh/ 0.25 = 28.8 kwh total usable. Thus you would need 28.8 kwh/1.8 kwh = 16 stacks total x $1150 = $18,400 cost for the bank to give you an average 25% DOD per day.

If you put in only 4 amps per stack, that is 4 x 16 = 64 amps @ 48volts which is over 3000 watts. At 4 amps per stack the RTE (round trip efficiency) is over 85%. For the maximum loads it would be about the same as the maximum charging current. You could go to 9.5 amps per stack x 16 = 152 amps max @ 40v = about 6000 watts max for input with solar and for load handling. Note that RTE drops to a little over 70%, and this is where the internal resistance factors in.

These batteries are not meant to handle really heavy loads or charging currents, but if you size the bank properly, should work for many off grid users.

[Living Large]

If you size your bank accordingly then recharging won't be an issue. What is your daily usage expected to be and what will the highest load be on your proposed system?

OK, I am just about done here. I will use about 150Ah a day. At 25%, I need an 0082 bank for each day. That is 3 banks, at $15,000 a bank. Each one weighs 3100 pounds. So I need to spend $45,000 for 9,300 pounds of battery.

If that isn't daunting enough, let's see what happens every 3 days. I need to put in 450 Ah. According to Dereck's analysis, I can charge these 3 banks at maybe 40A. That is 11 hours.

All this at a price of $45,000. Did you see internal resistance in the Aquion specs?

[northerner]

I have a question. Did the specs the company put out include the internal resistance? Dereck calculated it to be 75 milliohms for a 48V 540Ah bank, which is huge: http://www.solarpaneltalk.com/showth...atteries/page3

This is a large part of why I can't use this battery - I'd be running my generator for many hours for each recharge for months each year - and possibly year round because charging in general will be a real challenge.

If you size your bank accordingly then recharging won't be an issue. What is your daily usage expected to be and what will the highest load be on your proposed system?

[northerner]

I have run the numbers. You yourself said they are too expensive, but you are also saying they are more cost effective. I guess that is if I am willing to believe they last 10 years and I am willing to take out a mortgage now. But the warranty is 2 years. For me they don't add up at all. I am planning a low insolation in winter location, and need at least 3 days of backup. With the Aquion battery, I would need to add extra capacity simply because I can't use a good portion of the energy storage at lower than 42V. So now when I go to charge using my generator, I'll have to run it for 8-12 hours. Fuel costs and maintaining the generator has to be added to your comparison.

Contrast this to LFP, where I only have to run the generator maybe 3-4 hours. And I don't need to provide an entire room to store them and have a hoist on hand in case they need to be moved. Maybe your application fits - mine didn't. LFP looks far better for me, by adding the proper provisions needed to keep from ruining them. Before AHI I would go to FLA, which would add maintenance add weight, and take away some risk. I did like what I saw first with AHI. The last straw was the 30-59V window.

As I mentioned, up front cost with AHI will likely be higher than FLA or LFP batteries. When you factor in total cost of ownership, and if the specs that the company post hold true, will be lower after factoring in cycle life.

If you are not willing to take the risk, and have issues with the warranty, then best to shop else where. These batteries are not for everyone as has been mentioned previously.

With my setup, I have generator run time in winter, irregardless of how much storage I have. I run the generator for an average of 3-5 hours nearly everyday for about a 2 month period.

The Aquion batteries should be sized to allow between a 25% and 50% DOD on average, which will allow for higher load handling. There is really no difference with other chemistry's. FLA is recommended 20-30% DOD and LFP is recommended 35% DOD. LFP's have a slight advantage with higher overall efficiency, but that is not enough to overcome the overall cost savings with AHI.

[Living Large]

The specs the company put out, providing they hold true, indicate that this battery will potentially give a very long cycle life, and lower overall cost.

I have a question. Did the specs the company put out include the internal resistance? Dereck calculated it to be 75 milliohms for a 48V 540Ah bank, which is huge: http://www.solarpaneltalk.com/showth...atteries/page3

This is a large part of why I can't use this battery - I'd be running my generator for many hours for each recharge for months each year - and possibly year round because charging in general will be a real challenge.

[Living Large]

The specs the company put out, providing they hold true, indicate that this battery will potentially give a very long cycle life, and lower overall cost.

Do the costing of $ per kwh factoring in cycle life yourself if your not convinced. No other battery out there is more cost effective at current prices!

I have run the numbers. You yourself said they are too expensive, but you are also saying they are more cost effective. I guess that is if I am willing to believe they last 10 years and I am willing to take out a mortgage now. But the warranty is 2 years. For me they don't add up at all. I am planning a low insolation in winter location, and need at least 3 days of backup. With the Aquion battery, I would need to add extra capacity simply because I can't use a good portion of the energy storage at lower than 42V. So now when I go to charge using my generator, I'll have to run it for 8-12 hours. Fuel costs and maintaining the generator has to be added to your comparison.

Contrast this to LFP, where I only have to run the generator maybe 3-4 hours. And I don't need to provide an entire room to store them and have a hoist on hand in case they need to be moved. Maybe your application fits - mine didn't. LFP looks far better for me, by adding the proper provisions needed to keep from ruining them. Before AHI I would go to FLA, which would add maintenance add weight, and take away some risk. I did like what I saw first with AHI. The last straw was the 30-59V window.

[Sunking]

I personally haven't seen the battery perform and that is why I asked new users to chime in with their experience with the Aquion batteries.

Don't hold your breath waiting. Well heck even if you breath, you will still be dead before anyone chimes in.

[northerner]

Where have you seen the battery perform?

I personally haven't seen the battery perform and that is why I asked new users to chime in with their experience with the Aquion batteries.

Aquion has sent out stacks for independent testing and that is the performance I quoted about. The specs the company put out, providing they hold true, indicate that this battery will potentially give a very long cycle life, and lower overall cost.

Do the costing of $ per kwh factoring in cycle life yourself if your not convinced. No other battery out there is more cost effective at current prices!

[Living Large]

I have seen that this battery does perform and I'm not concerned about long term warranties. The only thing I would like to see is a further reduction in price, something which is scheduled to happen in time.

Where have you seen the battery perform?

[Living Large]

Think you have a typo in the Quote field. Those are not my words.

Dereck - there is a formatting error in post #110 by northerner, which caused the editor to incorrectly attribute you as the author. While the editor indeed incorrectly attributes my reply to you, I was replying to to northerner, which you can easily see by looking back. I will post another, and see if I can correct it.