What are the pros and cons of using forklift batteries with solar ?

Johann · October 2016

Right now it it is a thinking process, but I like to research it to figure out what I will do and I still like to get the info about the pros and cons before I get things rolling.

I may be able to get a used 36volt 800 ah forklift battery for about $200 from where I work. Is this a good price?
The battery was in daily use until 1 month ago when the forklift itself broke and it did not have any problems with the battery as far as I know.

How many watts of panels does such a battery need to keep it alive? This will be pretty much a standby system or does a forklift battery need to be cycled ever so often?
I know that 36 volt is not common, so I was thinking to turn part of the battery into a 24 volt system and the rest into a 12 volt system to power some other stuff ?
Would anybody know the possible weight of that battery?

Any thoughts and comments would be appreciated.

mike95490 · October 2016

Sounds like a sweet deal, IF the battery has been getting charged once a week.
Forklift batteries are not the most efficient, and have higher loss than "off grid" batteries,
They are often tall, and generally, to prevent stratification, you need to charge at 10% of cell capacity, so 800 ah would need 80a to keep the cells healthy since they are not being sloshed around in a forklift. Need to be able to provide 80A for at least 2 hours, not just 20 minutes at solar noon,
80a @ 45v = 3600 w harvest @ 80% = 4500 well aimed watts of PV That's going to need 2 charge controllers most likely.

BB. · October 2016

Look for Discussions and Comments from user Adas:

http://forum.solar-electric.com/profile/adas

Have not heard from him for quite a while, but he has been doing exactly that. Taking used forklift batteries and taking his fabrication business off grid in Hawaii. He also would get a 36 volt battery and slice out bad cells/reconnect into a 24 volt battery.

He was very happy with the results.

-Bill

softdown · October 2016

Their self discharge rate seems to be higher than regular batteries. They can be quite dangerous to move due to their height and weight. Built to last....that is probably their best feature. May get 15-20 years out of a good forklift battery.

Also....the lead plates go almost to the top of the cell. So keeping the water levels up is more important. Really recommend medium height water miser caps. The shorter caps probably will not clear everything.

If I did it over again, I would consider getting two ~600 pound 24 volt forklift batteries. Bigger would be much better if you can safely move them. I live alone and do not relish having a falling battery trap me. Looking at the Ah capacities however...I would have to figure out a way to install the ~1100 pound 24 volt batteries.

Perhaps someone here has figured out a way to safely move forklift batteries around?

softdown · October 2016

Thinking more about this...what about the economics of a 2200 pound 48 volt forklift battery installed outdoors with an insulated, shaded, and fireproofed shed around it?

Once flipped over my 1650 pound 24 volt forklift battery while moving it in icy and sandy outdoor conditions. I jumped in the right direction....so I am still here to post about the possible dangers of 24 volt forklift battery transportation. 24 volt is singled out because they have a base 1/2 the size of 48 volt banks....and are quite easy to push or accidentally lay over while moving.

FWIW....flattened 3/4" copper pipe makes a highly efficient "bus bar". The aforementioned Adas said this pipe could be insulated with 3/4" pvc...which he then heated to make a tight fit.....as memory serves.

For the original poster....I think you are on the right track with the 24 volt and 12 volt solution. I would try to avoid slicing up the 36 volt battery bank more than I had to. Cobbled connections are rarely as good as factory connections. Molten lead/tin can be hard to control when larger amounts are used. Plus you have the possibility of melting the plastic on the battery cell cases.

Johann · October 2016

Thank you all for your comments.
What should the charging voltages be. Is it like a normal flooded deep cycle battery?
I need to check if my el cheapo controllers can be adjusted to it?
Do forklift batteries ave the same freeze points as flooded batteries, since it may sit outside under cover like my current batteries.

softdown, I think that the weight may be around 2,000-3,000 lbs. for a 36 volt battery, does this sound about right?
A 36 volt is not so easy to turn over, but there is always a possibility. The cell arrangement as far as I remember is 3 cells wide and 6 cells long. And usually I do all my work by myself also.

I got a question. What do water miser caps do?

mike, Yes that battery got used almost every day and charged at 3rd shift for 8-10 hours every say. The last month, it did not get charged and it did not get used. I need to see to get it charged when I get back to work.

BB, thank you for the link. I am still reading the posts there.

BB. · October 2016

Check with the battery manufacturer for specific charging voltages--But flooded cell forklift batteries are lead acid and (overall) have the same characteristics of our "standard" flooded cell L.A. batteries (other than they typically use more distilled water and have higher self discharge, on average). They should be charged at 10% minimum rate of charge.

Water Miser caps just have small plastic balls inside them that give more surface area for electrolyte mist to collect on them and allow the condensate to drip back into the battery cell. They do not do anything regarding water loss as Hydrogen+Oxygen (other than less the dry gas escape to the atmosphere).

-Bill

Dave Angelini · October 2016

If you have a family and are offgrid, that depends on power, a used battery that is of unknown quality it a big mistake to do in winter.
These batteries are for an advanced user who is flexible and has the time to kill.
At the minimum you should have another bank and a plan on what to do if this all goes south.

softdown · October 2016

After charging, check the voltage and specific gravity of each cell. The beauty of the forklift battery is that bad cells can still be replaced. If the cell voltage is less than 2.1 volts right after charging....I would probably call it a weak cell. Specific gravity is a more useful measurement in all likelihood. Seems (S.G.) to be more temperature dependent in my experience.

Problem is that they may decide to keep the battery if they figure out it is OK. Forklift batteries have a scrap value of ~.17/pound. So you can't really lose financially.

Johann · October 2016

Dave Angelini said:

If you have a family and are offgrid, that depends on power, a used battery that is of unknown quality it a big mistake to do in winter.
These batteries are for an advanced user who is flexible and has the time to kill.
At the minimum you should have another bank and a plan on what to do if this all goes south.

.

Thanks,
This battery was used daily at the same company I work for until one month ago when the lift croaked on a mechanical issue that the company won't fix because it cost more than what they think is worth to fix it. I know it means not much that a forklift ran of the battery all day long, it still could have a fault since it is used. The battery will not fit anything else they have and they replaced that broken forklift with an newer used one that has 48 volts.

Thank you for the warnings, something to think about it and to mention.
I have another bank, but it is on the way to go go south, that is mostly why I am interested in that $200 battery. ( Not to much to lose).
I have other ways to charge it, if needed.

Johann · October 2016

softdown said:

After charging, check the voltage and specific gravity of each cell. The beauty of the forklift battery is that bad cells can still be replaced. If the cell voltage is less than 2.1 volts right after charging....I would probably call it a weak cell. Specific gravity is a more useful measurement in all likelihood. Seems (S.G.) to be more temperature dependent in my experience.

Problem is that they may decide to keep the battery if they figure out it is OK. Forklift batteries have a scrap value of ~.17/pound. So you can't really lose financially.

I am on a mini vacation right now, but I will find out in few days what happen. That old lift been sitting there for 1 month already, I am sure it will be there for a few more days. That battery will not fit anything else they have as far as I know. I must say that the company scrapped ( gave away) a perfectly good battery about 4 years ago, that was discharged with an dump load and charged every 2 weeks for 6 month.
What tester do you use? I did not have to use one yet, for the AGM batteries I have.

Thank you for the information.

Photowhit · October 2016

If you have the means and place to move it, give it a try. You can buy a fair quality glass hydrometer at an auto parts store for $10, you would do well to check it out against a known good hydrometer, sometimes the scale can be placed incorrectly.

More about the actual use of a forklift battery. They will be fine outside, I moved mine (1100 lbs 24 v) to a wooden platform I had built and leveled, then built a wood box around it. It's been fine for @4 years there.

They do take a bit more care, equalizing monthly is normal and some recommend every 2 weeks. This is one reason they use more distilled water than other types of batteries. Most suggest charging at a bit higher voltage, I am just maginally above what I used for golfcart batteries.

I don't worry about equalizing when they are in heavy use during the summer. I would only equalizing at those high temps if I had extreme problems/issues. They have a huge discharge/recharge during the summer months and living outside, even in the shade they will get warm. We have an increasingly longer summer here, Missouri, and if we get a normal couple days of cool weather I will try to squeeze in an equalizing, I do have and would suggest you have a temperature sensor for your charge controller!

Mine has only about 3/8ths of an inch above the splash guards. Water Miser caps have reduced the amount of distilled water I've needed to add.

They have a bit of a different voltage drop with heavy loads, hard to describe, but my voltage will drop noticeably with even a sub 1/20th of capacity load, say 600watts maybe 25 amps out of a 640 Amp hour battery, but then it will hold close even with 3x that load (breaking into drawing more than 1/20th). At first I thought I had a weak cell or 2 but It has continued to have this behavior, someone else confirmed a similar behavior, or I wouldn't post this, I have a cell that I believe was poisoned(I worked security at the place of my residence). This is my first forklift/traction battery.

Johann · October 2016

Photowhit,
Thank you for your post
Would this hydrometer from our sponsor be good enough? It is temperature compensated.
I was thinking to pour a concrete pad and put bricks or cement blocks around it with an hinged top if I get the forklift battery. This way the temperature inside that '' box '' would be more stable and cooler in the summer I hope, and would be more fire resistance.

Vic · October 2016

Johann said:

Photowhit,
Thank you for your post
Would this hydrometer from our sponsor be good enough? It is temperature compensated.
I was thinking to pour a concrete pad and put bricks or cement blocks around it with an hinged top if I get the forklift battery. This way the temperature inside that '' box '' would be more stable and cooler in the summer I hope, and would be more fire resistance.

Hi Johann,

MidNite distributes the Hydovolt Hydrometer in North America. I like and respect MidNite.

However, did buy three Hydrovolt Hydros, when MidNite first started distributing them. Am unable to get consistent, repeatable readings with them. Usually upon taking a sample, the rotating scales hang up, and the hydro needs a bit of a rap, to get the scales to move.

For a forklift battery, the too short sample tube would probably not be an issue. But, for Surrette 5000 series batteries, the sample tube should be about twice the length on the Hydrovolt hydros that I have.

Still prefer all glass Hydrometers, like the Freas Glassworks ones, without colored scales. The Sponsor of this site used to carry Freas Hydrometers, but they have not had them for some years. Believe that Freas will sell direct to the consumer, presently, with a US$ 40.00 minimum order.

Believe that the Freas units in use here are the No. 1. The ones that I am using have glass "nubs" on the large diameter portion of the float. These help keep the float from hanging up on the outer tube.

Agree with Photowhit, that an all glass Hydro from an Auto Parts store can be perfectly adequate.

Opinions differ, but would suggest getting two or three Hydrometers, and test each of them to see the variation in readings.

If I had to choose a new battery bank, might try a forklift battery, but still might just buy another set of Surrette 5000 series batteries -- quite a bit more expensive that a lift battery, but they are really designed for off grid RE-charged service.

Hate to share reservations on a product that MN sells, but, the above is just my experiences.
FWIW, Vic

Photowhit · October 2016

I have the HydroVolt Hydrometer (the Midnite import) and have not had too much of a problem with it, It does want to hang at times, but glass hydrometers also hang or collect bubbles. I don't think it would be bad to have a glass hydrometer, O'Riely's AUto Parts sell one for $6-7. I had a nice lab type glass and can't find it, I always worried about breaking it, It's perhaps twice as long as the Auto Part hydrometers.

I would likely point people to the HydroVolt, but understand Vic's hesitations. Having built in temperature compensations is nice. I would not recommend the plastic Auto Parts Hydrometers, though part of that is from having no experience with them.

I would worry about shade more than the mass, though I've often threatened to make a small berm shelter for my lift battery. If you pour a slab, you might want to do a 'drill' down below frost level on each side of the platform to stabilize the pad. I've always thought you had to do a footer al the way around, but people here in Missouri often do just drill down below frost line every 4 - 6 feet and pour the slab/fill the drills all at once. I've heard this from people I trust, but I have no personal experience with this...

Johann · October 2016

Vic said:

Johann said:

Photowhit,
Thank you for your post
Would this hydrometer from our sponsor be good enough? It is temperature compensated.
I was thinking to pour a concrete pad and put bricks or cement blocks around it with an hinged top if I get the forklift battery. This way the temperature inside that '' box '' would be more stable and cooler in the summer I hope, and would be more fire resistance.

Hi Johann,
MidNite distributes the Hydovolt Hydrometer in North America. I like and respect MidNite.
However, did buy three Hydrovolt Hydros, when MidNite first started distributing them. Am unable to get consistent, repeatable readings with them.   Usually upon taking a sample, the rotating scales hang up, and the hydro needs a bit of a rap, to get the scales to move.
For a forklift battery, the too short sample tube would probably not be an issue.   But, for Surrette 5000 series batteries, the sample tube should be about twice the length on the Hydrovolt hydros that I have.
Still prefer all glass Hydrometers, like the Freas Glassworks ones, without colored scales. The Sponsor of this site used to carry Freas Hydrometers, but they have not had them for some years.   Believe that Freas will sell direct to the consumer, presently, with a US$ 40.00 minimum order.
Believe that the Freas units in use here are the No. 1.   The ones that I am using have glass "nubs" on the large diameter portion of the float. These help keep the float from hanging up on the outer tube.
Agree with Photowhit, that an all glass Hydro from an Auto Parts store can be perfectly adequate.
Opinions differ, but would suggest getting two or three Hydrometers, and test each of them to see the variation in readings.
If I had to choose a new battery bank, might try a forklift battery,   but still might just buy another set of Surrette 5000 series batteries -- quite a bit more expensive that a lift battery, but they are really designed for off grid RE-charged service.
Hate to share reservations on a product that MN sells, but, the above is just my experiences.
FWIW, Vic

I looked into the glass tube style and I thought that they are cheaply made. Years ago I had only testers with glass tubes like the ones for antifreeze and others, but that was eons ago and they made them big and the glass was thick. But they never failed.

After reading this, I may have to reconsider. I do not mind spending more, but I only like to spend my money once if possible and the quality got to be there.

I noticed that some of the glass styles are also temperature compensated. Is it necessary that the hydro tester is temperature compensated? Would the test result be very different if it is not temperature compensated?

Thank you for your comment,

softdown · October 2016

I'd worry more about keeping the battery happy than the nuances of various hydrometer "technologies." Even an el cheapo will find bad cells and that is your main concern.

I live in a cool environ so I don't have to follow my own advice. If I lived in a hotter environ, I would probably dig a hole that kept ~ 90% of the battery below ground level. Then I would pour cement for the base and insulate the sides to keep water and ice away from the battery case. I would also insulate around the remainer of the battery. This will add years to your batteries life.

People like to say that I build "doomsday" structures. I think stuff should last for 100 years. Why not?

Engine hoists and a chain work well for hoisting forklift batteries in a steel case.

Photowhit · October 2016

softdown said:

Engine hoists and a chain work well for hoisting forklift batteries in a steel case.

Please be careful on this last statement, a 650-800AH 36 volt battery is likely to weight 3000+lbs, not a lot of 3000+lb engines, even once lifted it wouldn't move very easy, a grain of sand might be an insurmountable obstacle!

softdown · October 2016

Some engine hoists are rated for one ton, others for two ton. They can be rented I believe. Moving 3000 pounds will take *thorough* preparations.

BB. · October 2016

I used to move 2,000 to 5,000 lb equipment as a "hobby"--Do not take short cuts (and do not stand or put your hands under loads) as they can kill you. Tying the stuff down properly in a trailer, etc.... All important.

-Bill

softdown · October 2016

softdown said:

I'd worry more about keeping the battery happy than the nuances of various hydrometer "technologies." Even an el cheapo will find bad cells and that is your main concern.

I live in a cool environ so I don't have to follow my own advice. If I lived in a hotter environ, I would probably dig a hole that kept ~ 90% of the battery below ground level. Then I would pour cement for the base and insulate the sides to keep water and ice away from the battery case. I would also insulate around the remainer of the battery. This will add years to your batteries life.

People like to say that I build "doomsday" structures. I think stuff should last for 100 years. Why not?

Engine hoists and a chain work well for hoisting forklift batteries in a steel case.

Is this cooling hole a bad idea? This group is usually too polite to disagree.

Photowhit · October 2016

I don't have a big problem with it, it's much like the berm shelter, that I have talked about doing. Using the earths' constant temperatures a few feet down to help cool the battery. Some places, I would worry about water intrusion. I've lived in Florida, not really possible there, and Missouri, which it could work if well protected.

BB. · October 2016

From an post of mine in a different discussion:

One of the really neat/handy rules of thumb I learned in Engineering Math class (was one of the first "real world" Calculus problems that was not related to mass/volume/moment arms) was this rule of thumb. For every 10C increase in temperature, the "thing" will age 2x faster. For every 10C decrease in temperature, the thing will last 2x longer (i.e., 20C cooler, 2x2=4 times longer).

We really see this with our Canadian friends. They sub freezing winters and cabins unused, their "cheap batteries" can last 8+ years (compared to 3-5 years typical in warmer climates).

Assume life of battery is based on 25C--Then at 35C (95F), the batteries will "age" 2x faster that that temperature.

For example, here is a nice graphic (for Virginia) that shows soil temperature swings vs depth:

Ground Temperatures as a Function of Location, Season, and Depth

Image: http://www.builditsolar.com/Projects/Cooling/amplitude-vs-depth.gif

If you need a "root cellar" for storing foods--That might be a good second justification for going deep.

Ralph Day · October 2016

I think the chain hoist statement was refering to removing and replacing cells (especially removing) from the forklift battery main case. Of course, in an industrial setting the infrastructure for hoisting a battery whole would exist for maintenance.

Ralph

softdown · October 2016

A foreseeable problem with tucking batteries into a "cool spot" is losing the ability to keep an eye on things. "Out of sight, out of mind?" However....the increases in longevity are noteworthy.

A lot of solar batteries are put in uninsulated sheds where the temperature may exceed 100 F. A bad plan to be sure.

One may wonder how car batteries lasts for five years, sometimes more, in such an adverse environment. They rarely get significantly discharged is my guess.

What are the pros and cons of using forklift batteries with solar ?

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