Aquion update

OffGrider · June 2015

Well it has been 7 months now with our 24 AHI S10 stacks running our 9 room guesthouse here in Hawaii. Our installer came to check how we were doing and everything is doing great! Since we haven't run past 60% SOC we have only had 32 cycles. around 4.5 cycles / month=54 cyclles/year. Aquion claims 3000 cycles @ 100% DOD and 6000 cycles @ 50% DOD. Could that mean our batteries will be around for 100 years?

Overall there are no complaints. No voltage sags turning off things. We did get down to 8% SOC when we had 5 raincloudy days. We generated enough power during the day to keep us even, but @ night we used about 20%. At that time we did have a full house and we were using the 1600w sauna and jacuzzi at least 1 hour per night. My wife also was using the dehydrator to dry bananas.

So for us, Aquions are working out Great! Yes they did cost an arm and 2 legs, but we are expecting a 35% tax credit for this year. There has been no maintenance routine, our eu7000is which was concerted to propane has not been used yet. Best off all no electric bill.

Aloha,

Offgrider

inetdog · June 2015

Thanks for the update!

kaipo_boy · June 2015

What island are you on?

Brlux · June 2015

Thanks for sharing. Do you have any pictures of your system you can post?

I am having a hard time following this "Since we haven't run past 60% SOC we have only had 32 cycles. around 4.5 cycles / month=54 cyclles/year."

Don't you go through cycle every day?

zoneblue · June 2015

OffGrider wrote: »

Since we haven't run past 60% SOC we have only had 32 cycles. around 4.5 cycles / month=54 cyclles/year. Aquion claims 3000 cycles @ 100% DOD and 6000 cycles @ 50% DOD. Could that mean our batteries will be around for 100 years?

A cycle is every charge and discharge, doesnt matter how much. Off grid, one day = 1 cycle. 100 years not gona happen, sorry! Your 50-60% SOC daily cycles indicates 6000/365 or 16 year life. However we dont know about calendar life.

OffGrider wrote: »

We did get down to 8% SOC when we had 5 raincloudy days.

8% SOC is very low. This would not be recomended for any battery in general as the risk of reverse charging low cells is high. Maybe the aquions dont care, dunno. What kind of monitoring system do you have in place. As you are one of the first users of these cells wed all appreciate any data you can supply.

Edit: for others see related posts at:
http://www.solarpaneltalk.com/showth...-AHI-batteries
http://forum.solar-electric.com/foru...ut-this-set-up

zoneblue · June 2015

So theres a bit more info out there now about these. Interesting battery.

-A stack is a group of 8 series cells with a stack nominal voltage of 48V.
-Terminal voltage has a wide range from 58V to 30V.
-Internal resistance is very high, in the order of 75 m ohm
-charge and discharge current limited / fused to 15A/(20A latest) per stack. (about 0.2C₂₀ )
-Capacity 48Ah at C₂₀. (20Ah at 10A rate, 45Ah at 4A rate (800Wh / 2000Wh)
-lower 20% unusable by most inverters.(40V lvd)
-cycle life 4000 cycles to 80%
-charge cycle effciency 85%
-self discharge 15%/month at 20*C (kinda high)
-safe operation temperature: -5*C to 40*C
-bms: none in stack and optional. Says it not needed.
-dont mind: partial SOC operation; 0% SOC. (reverse charge?)
-dont like: overcharge leads to electrolyte loss and high temp chemistry damage.
-dont like: freezing, leads to permanent chemistry damage.
-Volume 100 litres
-Weight 110 kgs.

Designing around these quirky specs yeilds (for our setup) something like:
Storage required: 5000Wh. At about 1200Wh per stack 4 stacks required.
Charge current: 40A. 3 stacks required.
Peak discharge rate: 90A. At 15A per stack, 6 stacks required.

Hence peak inverter draw is the limiting factor determining the number of stacks. 6 stacks gives us:
- usuble capacity 10kWh, compared to 9kW of AGM
- volume: 600L, about 4 times the AGM
- weight: 660kg, about 2.5 times the AGM
- floorspace, about the same
- life: maybe twice AGM, maybe...
- cost: 6 stacks is USD7000 + 800 freight, compared to USD1600 for the AGM.
http://www.altestore.com/store/Deep-...ck-48V/p11629/

Ive marked up a few comments on your excellent battery graphs. Attachment not found.

inetdog · June 2015

I think that a stack is actually a string of 8 multi-cell batteries, not 8 cells.
A single cell voltage of 6V is unlikely.

zoneblue · June 2015

Either way the configuration involves series cells, and yet the manufacturer says 0% SOC is acceptable. This can only mean one thing that some series cells get reverse charged. You will always have high cells and low cells. How do they cope with that? The specs explicitly say there is no electronics in the stacks.

inetdog · June 2015

zoneblue wrote: »

Either way the configuration involves series cells, and yet the manufacturer says 0% SOC is acceptable. This can only mean one thing that some series cells get reverse charged. You will always have high cells and low cells. How do they cope with that? The specs explicitly say there is no electronics in the stacks.

I think that you will find that:
A. 0% SOC by their definition is still a high enough voltage to greatly reduce the chance of reversing a low cell. You must provide external low voltage cutoff to protect the stack, just no cell level BMS.
B. The chemistry may tolerate cell reversal. I have not seen any info on this though.

By industry standards, 0% SOC just means the low voltage cutoff at which they measure and guarantee overall cell capacity. It does not mean extracting the last ounce of chemical energy from the cell. For example, an Li battery will have some 20% of its chemical energy still available at 0% SOC, but if you continue to discharge it beyond that point it will no longer be safely rechargeable with a conventional charger.

OffGrider · June 2015

Aloha, This is info from our Battery Monitor. As you can see the number of cycles is 34. zoneblue mentioned one cycle= 1 day. I don't think so. After battery gives up 1000Ah, this is considered a cycle.

zoneblue · June 2015

Thats just the comboxs way of indicating total throughput. However the industry uses a series of ratings for cycle life based on %DOD. You can see from the manual for the s10/s20s that they are rated for 3000 cycles at 100% DOD, 4000 cycles at 80% DOD, 6000 cycles to 50% DOD etc. Theres usually a graph for this but the publically available information for the aquions is restricted. You also have to factor calender life. Good luck with those cells and do let us know how they go over time.

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