Traction vs. Stationary FLAs

[stephendv]

What are the differences between FLA traction batteries (e.g. for forklifts) and stationary FLA batteries for use in backup, telecom and solar applications? The former are usually called "PzS" batteries and the latter "OPzS" (in Europe anyway). I know many on the forum are quite happy with their used traction batteries - would you still consider them a good buy if they were new and more expensive?

The traction bats also seem to have a choice between thinner plates but more of them, or fewer thicker plates for the same given capacity. (The total amount of material in the electrodes stays about the same). The Battery FAQ says thicker is better, but does it take the number of plates into account?

I don't know enough about how batteries work to compare, but here's an example from the same manufacturer for 2V 810Ah (C10) cells of type OPzS and PzS:

Stationary:
- 7 OPzS 811Ah with 7 plates, 42kg without electrolyte, 60kg with.

Traction:
- 9 PzS 810Ah with 9 plates, 37kg without electrolyte, 46kg with
- 5 PzS 750Ah with 5 plates 31kg without electrolyte, 41kg with
- 10 PzS 800Ah with 10 plates 35kg and 44kg

The stationary batts are heavier even though they're rated to the same capacity (I double checked, they are all rated at C10). Then there's also a difference in the amount of electrolyte in the cell: almost double in the stationary batts!

I think market forces will always keep the traction batts at a lower price than the more specialized stationary ones, so the question is - if you had to spend good money on new FLA batts, would you still consider traction ones?

[BB.]

You really need to look at the specification sheets for each battery...

Some will take lots of deep cycling (like traction batteries) but need a fair amount of service (adding water, etc.) and they may have a more limited life time (years in service). Also, Fork Lift and Traction batteries seem to "waste" more energy in charging (heating and equalization) and seem to probably have more self discharge losses--especially after the batteries get well aged (and some batteries are intended for "standby" operation--little cycling except in "emergencies").

The other extreme (Telecom Batteries) can use less water, have incredibly large cycle numbers and 40 years of life in service... However, they may only be designed for cycling from 100% to 85% (no deep cycling) to get those incredible lifetime numbers.

Lots of "hand waving" here--but that is what I have seen when looking through specifications and reading about user experiences in the past.

The different types of batteries have the place--And it is important that your usage not fall outside their operational envelope.

Throw AGMs (sealed) batteries into the mix--and there is a lot to choose from. Since batteries are expensive to ship--checking with your local battery distributors for their recommendations and what they stock would be a good idea (if you can get the same batteries 7-10 years later--you don't have to reconfigure you battery bank hardware).

-Bill

[icarus]

Traction batteries are subject to significant vibration and (I would guess as I don't know!) that the plates might be thicker as a result. They are also subject to much more regular cycling.

Stationary telecom batteries may go their entire service live never having been cycled significantly.

Tony

[Cariboocoot]

Cost and availability should be considered too. Every type of battery has its advantages and disadvantages. Deep cycles don't produce 'quick surge' current like automotive batteries. But auto batteries will fail rapidly in the AE application's repeated deep discharge/recharge. Telecom batteries being rated for only 25% DOD, which may do on a solar power system. But ...
Most of the time you'll find the electro-motive force batteries are easy to obtain, relatively inexpensive, and will do the job well - including standing up to 'abuse' such as occasional 50% DOD or slightly incorrect charging voltages.

[stephendv]

Just to clarify that both types of battery I'm talking about here are deep cycle, vented, flood lead acid's. (Sometimes terms like 'telecom batteries' could refer to FLAs, GELs and AGMs).
I had an interesting chat with a manufacturer this morning - he says that in principle the electrical and chemical properties of the batteries are identical, the main difference is that the traction batteries are limited in size and so can't hold as much electrolyte - therefore they'll need more topping up. Also, as Icarus was saying, the tractions are mechanically more robust to handle vibration and movement.

BUT because they produce many more traction batteries, the price will always be lower than the stationaries - and the difference in price could mean that I could afford a bigger capacity traction battery, with the caveat that I'll have to water it more.
Life expectancy characteristics is the same for both types (from the same manufacturer and assuming they're both well looked after).

[Dave Sparks]

In Marine the batteries from Surrette are built for healing (tilting off axis) and do have a little less electrolyte capacity do to the extra material to protect the battery from vibration as well as keep the electrolyte over the plate while healing.

In your design take a look at the 2V cells these folks are coming out with. Trojan also has them. I don't know if 1000ah @2V on the 20 hour rate is the right capacity for you but take a peak!

[stephendv]

Thanks for the input guys. Just an update that I've received a quote for the traction and stationary batts from the same company:
- Tractions are 30% less than the same capacity stationaries
- Tractions are 50% less than the same capacity Rolls Surrette 5000

On another note, some of the traction manufacturers also sell electrolyte circulation kits with their bats (which seems to be just a pump that pumps air into the electrolyte to mix it up). One manufacturer claims 20% more efficient charging using this system and longer life (because the plates wear away evenly rather than wearing down on only one part because of stratified electrolyte). I guess it's also advantages as you don't have to do equalisation charges as often.

Anyone use systems like these? Or DIY versions of them?

[Dave Sparks]

It is my opinion that all aftermarket equipment that is sold for batteries is just a waste of money. Bubblers, desufators and anything else that is not sold by the battery manufacturer is probably a waste of money.

If you have never lived offgrid before I would tell you to buy the best. Others will tell you to buy a "training" set of batteries but if the system is well thought out it will just be duplication of effort.

You will get what you pay for and this is especially true with batteries. Living offgrid has plenty of challenge so batteries should not make being successful more of a challenge.

[stephendv]

Hi Dave, yes I was originally going to go directly for the Surrette's because of their reputation, but money is tight and I really want to stretch my euro as far as it'll go. So while I'll grant that the Surrettes are probably 'better' than the tractions, it's a question of how much better? With the quotes I have, they'd have to last exactly twice as long to be worth it - which I find hard to believe given how well other off-gridders are doing on used sets of traction bats.

I may be speaking out of my a$$ here, but I don't think there can be that much difference between batteries using the exact same technology. These traction bats are tubular plate flooded lead acids designed for deep cycling up to 80% with antimony added to the plates. Different manufacturers could bring out products that differ in maybe a few percentage points - but a 50% difference is hard to swallow.
While I don't want to complicate my off-grid adventure, I _do_ want value for money, especially when I could invest it in other balance of system components, like a bigger PV array.

In the case of this particular traction manufacturer, the air bubbling kit is actually sold by them as part of the battery system, details in their leaflet (under Airlift): http://www.sunlight.gr/Uploads/PZS.pdf

[Dave Sparks]

The model I am talking about is the S1380 and it is a 4000 series L16. It is near 1050 AH @ 20hour rate. This is easy to move, well 117 pounds is never easy but this is where I draw the line for my customers.

Oh yea, I think there is a huge difference and expect 10 to 15 years life out of what I buy. You know what? I get it and I have before!

PS apples and oranges. Make sure you are comparing the same charge rates. We use C20 for solar!