Which battery is best for solar?

[xsnrg]

It would seem that introducing Li into the equation greatly complicates the whole set up compared to just a AHI, where the SOC really doesn't matter.  You would lose out on almost all of the benefits of the AHI stack in doing so.  BCS, SOC tolerances, temperature concerns, etc. adds a lot of complexity and monitoring needs that the AHI just doesn't have.  For the money and the worry, I would lean towards another S20 or two to make sure the current flow is there in the lower SOC areas of the curve.

$.02 of course.  I sure would like to see more AHI stories!

[North of 56]

It would seem that introducing Li into the equation greatly complicates the whole set up compared to just a AHI, where the SOC really doesn't matter.  You would lose out on almost all of the benefits of the AHI stack in doing so.  BCS, SOC tolerances, temperature concerns, etc. adds a lot of complexity and monitoring needs that the AHI just doesn't have.  For the money and the worry, I would lean towards another S20 or two to make sure the current flow is there in the lower SOC areas of the curve.

Not sure how bad the voltage sag issue is with AHI with loads and at a lower SOC, but have a feeling that voltage drop could be a real PIA. Should only take a small LiFePo4 pack to deal with the problem, and voltage set points and a simple BMS monitor in place to protect it, is all that's needed.

If the LFP is just used on a more occasional basis, then issues with the user overseeing the balancing and monitoring of the cells won't be so intrusive, providing it's set up to operate in a safe range. Plus, if you ever did have a problem with the cells, it wouldn't be an absolute disaster! It's either that or limit DOD, which limits usable storage, and could mean more frequent generator run time, and perhaps having to deal with the inverter kicking out with loads?

Of course, setting it up would be a DIY project requiring some relatively simple circuit design and implementation, so may not be the best option for everyone. Anyway, that's my 2 cents.

[mike90045]

I too,  think that adding LFP batteries to the mix will greatly complicate the system and lower overall reliability. (BMS failure points, yadda yadda yadda.)

With my NiFe, I oversized the bank to allow for the IR losses, but the liquid batteries are so high, that more parallel banks my cost too much.  I like the idea of the genset powering up to handle larger loads, and do a bit of recharge at the same time.

[North of 56]

I too,  think that adding LFP batteries to the mix will greatly complicate the system and lower overall reliability. (BMS failure points, yadda yadda yadda.)

With my NiFe, I oversized the bank to allow for the IR losses, but the liquid batteries are so high, that more parallel banks my cost too much.  I like the idea of the genset powering up to handle larger loads, and do a bit of recharge at the same time.

I have to run the generator in winter irregardless, but from about mid February to mid October I have practically zero run time, so having the extra boost to get through cloudy days could work well with AHI batteries. It's either that or significantly over sizing the bank, which could be very expensive!

At least this small LiFePo4 bank would be relatively inexpensive, and can be run for long periods maintenance free, if set up properly.

[Westbranch]

N/56...  what about the inverse setup, a slightly larger Li as the main bank sized  to run all small loads and the AHI to kick in when doing heavy work?  Just a thought....

[North of 56]

N/56...  what about the inverse setup, a slightly larger Li as the main bank sized  to run all small loads and the AHI to kick in when doing heavy work?  Just a thought....

I figure that the AHI will have the best overall cost performance, and for efficiency, is best suited to lighter loads. LFP is better suited to handling heavier loads efficiently. With my system, loads are light most of the time and are only heavy on occasion, thus the reason to boost with the LFP when needed, but run economically with lighter loads the majority of the time.

[xsnrg]

Battery tech is jumping forward in all sorts of directions.  It is a good time to be a battery nerd.  Here is another company working hard on storage:

http://www.eosenergystorage.com/technology/

[Westbranch]

And another one using capacitors in the cell... http://www.ecoult.com/?_cldee=ZXJpYy5qb2hhbnNlbkBzaGF3LmNh

UltraBattery® â€" a completely new class of advanced lead-acid battery technology.

[mobywile]

Y'Know, I am a flooded kinda guy.  I would LOVE to experience the Trojan 2v RE cells.  They have the guts for a guy like me.  Seems that we could run these babies down to, like, crap, and still have thousands of cycles left.  Not the most "high-tech", but real Mac Trucks.  One of my customers has bought a set of used 4v Trojans and, other than need ing a trio of young toughs to carry the suckers, is loving them to death.  Just old-guy 6V talkin' here.....
Moby

[vtmaps]

Y'Know, I am a flooded kinda guy.  I would LOVE to experience the Trojan 2v RE cells.

Those are at the very bottom of my list of desirable batteries.  The reason is that each 2-volt cell is actually three 2-volt cells in parallel.  Three times as many cells to water.

Trojan does make some high quality 2-volt single cell batteries in their Industrial line, but the 2-volt cells in their RE line makes very little sense to me.  Someone must be buying them or they wouldn't make them...

--vtMaps

[xsnrg]

Alt-E has some more documentation up on the AHI stacks:  http://www.altestore.com/store/Deep-Cycle-Batteries/Batteries-Saltwater-Technology/Aquion-Energy-S20-Pre-wired-Battery-Stack-51Ah48V/p11629/

I built a spreadsheet to help me understand the temperature charging characteristics.  The 59v at 5A at 30C makes sense, but when you figure out the ramp rate on how temperature affects charging, it seems to be a higher rate for the AHI vs lead acid.  Thankfully there is a lot of adjustment room in a Midnite controller.  They do break it down into bulk/absorb/float speak, which is nice.

[russ_drinkwater]

A stupid question perhaps.
Can the 48 volt aquin batteries packs be split into 24 volt as they appear to be plug and play?
And any updates of their usage and costs.

[Halfcrazy]

A stupid question perhaps.
Can the 48 volt aquin batteries packs be split into 24 volt as they appear to be plug and play?
And any updates of their usage and costs.

yes they use standard MC4 connectors. I have them on several 24v systems and a couple 12v systems

[toothy]

I'm not sure the company recommends splitting the stacks. I'm pretty sure it's frowned upon. However, it looks like they should be divisible easily.

Use and cost..... I'm happy so far. My fla Rolls bank drove me crazy because I worried about them, probably more than I should have. They don't seem to really like the cold, capacity wise. Full sun a few times a month for more than a few minutes would really be nice and probably help my capacity issues.

If your system is such that you may ever need gen back-up I would say it has to be auto start. Or you have to be OK with low voltage disconnects because they fall off a cliff at the lower voltages. YMMV

Wade