forklift battery sizing and prolonging life

kava · January 2019

Hello, I have never used a forum before and I am VERY new to solar but I found some great information here and thought I would join. I am in the process of desiging my solar system and am looking for advice/confirmation for the system I plan to purchase. After a TON of research I have decided to go with a forklift battery, new, 24-85-13. It is 48v 804ah with an automatic watering system on it as an added safety but do not plan to rely on it. I will have 14 panels Axitec 360watt mono 60 cell. Has anyone heard of the Sol-Ark? It is the reason I have decided to go solar. It is EMP proof and a nice all-in-one unit that makes things more simple for me. The house is pretty efficient and looking at my PGE bill it seems I use 10-16 kwh in a day when not running the air-conditioner (about $120/month). I do not plan to size my system to handle the HVAC. The Sol-Ark is able to be grid-tied, hybrid or off-grid. I will use it in a hybrid mode unless the grid is down. After seeing how it all works out I may go off-grid in the future. I also have an 8kw generator that will plug right into the Sol-Ark for auto start if/when needed.

OK...now for my questions.

Is my system sized ok for my battery?

I am confused by the battery manufactures information. Will I get more life out of my battery in a "float" or do I need to always discharge way down to 80% and then all the way back up to avoid having lots of cycles and wearing out faster. Does a charge to maintain "float" not count as a cycle? I want this battery to last a LONG time which why I am going with a lift battery.

Do I have enough panels for my use? I am in California zip code 95648 and the location is FULL sun, all day.

I may want to run another well pump and a mini-split air conditioner in the future if the system is able.

Goal: to be as self sufficient as possible

Sol-Ark info attached:

Photowhit · January 2019

kava said:

...I have decided to go with a forklift battery, new, 24-85-13. It is 48v 804ah...

Sounds like you have gone to GB's web site and are using their inflated numbers for forklift batteries.

The 24-85-13 battery can be read as 24 cells - 85 amps per positive plate(6 hour rate) - 13 cells (6 of which are positive plates. So that is a 510 amp hour 48 volt battery. GB over estimates the capacity of the batteries at the 20 hour rate. They use a multiplier of about 1.6, more accurately this should be about 1.3(maybe less 1.2 or 1.25) So 510 x 1.3 = 663 amps at a 20 hours rate.

While different alloys will have a bit different capacities over different discharge rates, here are a couple examples;
L16RE-2V

HUP Solar 1

Rolls 2 YS 31P (most optimistic I found with a multiplier of just over 1.4)

mcgivor · January 2019

@kava Welcome to the forum

When designing a system, it's better to decide on what it's ultimate purpose will be, building for use with grid support is vastly different from a full time off grid setup. A backup system requires a much smaller battery bank, the description of components would, by rough calculation be marginal as a full time off grid system given loads described , generator support would more than likely be needed, especially during December January http://solarelectricityhandbook.com/solar-irradiance.html using Sacramento as closest location. For grid supported backup it's fine, as long as solar can be used to support loads when the battery is fully charged.

To answer question of if PV is suitable for the battery, a defined purpose of use is needed.

A battery always in float is a battery wasted IMHO, they do die of old age irrespective of cycles, so use it or loose it.

There is some merit to dischargeing to say 80% state of charge, which I assume is what was meant, this allows charging to stir the electrolyte to prevent electrolyte stratification, more common in tall cells, which lift cells are.

Won't preach about grid being far cheaper as I've no knowledge of the intent.

mcnutt13579 · January 2019

I agree with the overinflated battery 20 hr rate claim. With these type [Chinese] batteries we just use the 6 hour rate as the stated amount available to the occupant. Increase the 6 hr rate by 20% for a realistic 20 hr rate, then take 80% DoD and you are right back to the 6 hr rate basically as your net capacity. But they do seem like an OK battery as far as it goes, much better than L16s for lifespan in cycling applications. Not sure about standby application but flooded batteries are multiple times tougher than any other lead-acid construction.

Common sense says get them full and keep them full. The people that really work them are the people that need to replace them.

As for inverter brand, common sense says stick with the common ones. There is always some new manufacturer hanging out a shingle but the old ones, designed by people that we know, are Xantrex, Outback, SMA, soon to be Midnite, and Magnum (with reservation)

Vic · January 2019

mcnutt.., said, " ... With these type [Chinese] batteries ... " so, are you saying that Giant and perhaps other Forklift batteries ARE Chinese ?

Seems to me, that designing one's life around the possibility of EMPs can create some problems.

Agree with mcnutt.., stick with power equipment from manufacturers that have been at it for a long time, with good history of solid products and customer support.

Could not find a manual for that Sol-Ark product. The details matter, but the info on their site seems mostly Marketing.

IMO, Vic

mcnutt13579 · January 2019

I know for a fact that some of the cheaper [priced] fork lift style batteries are Chinese. I don't know about Giant specifically, never even seen one of them. But several off-brand manufacturers are using the same model numbers, same spec sheets and the same overinflated 20 hour rates. So I suspect they may be similar products to each other. I also can say that they have been giving excellent service despite any reservation of their origin. Their cost is hard to beat. No reason to use L16s any more as far as I am concerned. The Chinese batteries "might" fail. It seems like L16s are just about guaranteed to fail. Can't stand them.

Vic · January 2019

OK, Thanks mcnutt..

Many folks do buy Floor Scrubber batteries and the like, which have seemed to be on the inexpensive end of L-16s, but, at least these batteries do seem to be real deep-cycles.

Thanks for the info ... have been tempted to try a Forklift battery, because of the prices ... Vic

kava · January 2019

Thank you for all the responses!

Photowhit - I have never had the AH rating explained like that. Great information.

Vic - did you see the attachment I sent with my first blog? I will add the full manual here - see attached

Mcgivor - I would like the solar system to be capable of going off grid at which time my batteries and generator will be used regularly. I am on the grid now and will not disconnect so I will be reverse from most people with my solar being my primary source and the grid as a backup (unless it is down). I don't know if it will be better for the battery to keep it in float or just use it. Some things I have read say to discharge almost to the "red" which is using 80% of capacity (this is to cycle less and keep the battery able to take a full charge). Other places say only use the top 20-30%. Other others say stay in float. so??? What makes the lift battery last the longest? The reason for staying on the grid is pretty much for air-conditioning and shop equipment and because I am not confident enough yet to let it go. My current electric bill is exceptionally low....saving money is not the goal, being independent is for so so many reasons....

Will my system be able to charge the forklift battery?
Is 510ah enough for my use most of the time?

softdown · January 2019

Only problem I have with forklift batteries is that moving them indoors can be exceedingly difficult and occasionally dangerous. I jumped in the right direction twice when my tall and skinny 1650 pound 24 volt battery fell over in the sand and snow. An experience I will not soon forget.

Seems like the battery in question will be very heavy.

On the grid and buying a huge, expensive battery?

BB. · January 2019

Since forklift batteries tend to be a bit less efficient and have higher self discharge (especially as they get towards end of life), I would suggest rounding up on your array size (5% what you think you need, go 10%. 10% up to 13%+...).

-Bill

WaterWheel · January 2019

As to the question as to how deep/often to cycle a LA battery the less deeply you cycle the battery the longer it will last within reason. Never cycling a battery will allow the electrolyte to stratify hurting the battery if it goes on for too long.    This is especially true for tall batteries like forklift and L-16 batteries.

Also consider that if you only drain the battery to 90% SOC (state of charge) when recharging the battery the electrolyte may not bubble enough to mix the electrolyte well. You want to drain the battery down to 80% at least once a month so it gets a hard charge bubbling and stirring the electrolyte.

Regularly draining (cycling) a LA battery to 80% SOC seems to be the generally agreed to maximize battery use at a fairly reasonable battery wear rate.

Get and use a hydrometer weekly the 1st two months recording the results, after that you can check SGs monthly. With that automatic waterer installed that may be a little more work to do.    Learn your batteries SGs and how they change as the battery discharges and then recharges. That's how you fine tune your charge controller settings through the seasons and years.

If as more knowledgeable people here have suggested your forklift batteries are close to a 660 amp/hr at the 20 hr rate and keeping in mind that that forklift batteries tend to be a little harder to charge I'd still have say that you've got enough panels to charge at over a C/9 rate which is fine.

If instead you're saving the battery for a SHTF event I'd suggest charging the battery fully, let it sit for 2-4 weeks before applying a load to drop the battery down to 80% SOC and then recharging with a hard charge stirring the electrolyte.

mcnutt13579 · January 2019

softdown said:

Only problem I have with forklift batteries is that moving them indoors can be exceedingly difficult and occasionally dangerous. I jumped in the right direction twice when my tall and skinny 1650 pound 24 volt battery fell over in the sand and snow. An experience I will not soon forget.

Seems like the battery in question will be very heavy.

On the grid and buying a huge, expensive battery?

Yes they are heavy. They are wide enough that tipping over is not really a major concern so pipes and rollers are usually good enough. Or just rent a machine for part of the day. If the batteries are that deep indoors then you need to rethink your arrangement. Batteries need to be changed and good batteries are hard to move by hand. That's all there is to it.

11 years vs. 4 years by one manufacturer who makes both kinds. Our experience is that the spread is probably even wider than that in real life.

softdown · January 2019

BB. said:

Since forklift batteries tend to be a bit less efficient and have higher self discharge (especially as they get towards end of life), I would suggest rounding up on your array size (5% what you think you need, go 10%. 10% up to 13%+...).

-Bill

I suspect that the higher self discharge rate is caused by pure lead rather than the more common and economical lead plus calcium battery. Pure lead batteries are often called "high performance" and sell for significantly more. Yet forklift batteries hold their own in the value battle. Likely due to the economies of manufacturing on a larger scale - economies of scale.

As far as I know, Photowit and I are the forklift battery users here. If they were not so difficult to move they would likely enjoy more popularity.

softdown · January 2019

mcnutt13579 said:

softdown said:

Only problem I have with forklift batteries is that moving them indoors can be exceedingly difficult and occasionally dangerous. I jumped in the right direction twice when my tall and skinny 1650 pound 24 volt battery fell over in the sand and snow. An experience I will not soon forget.

Seems like the battery in question will be very heavy.

On the grid and buying a huge, expensive battery?

Yes they are heavy. They are wide enough that tipping over is not really a major concern so pipes and rollers are usually good enough. Or just rent a machine for part of the day. If the batteries are that deep indoors then you need to rethink your arrangement. Batteries need to be changed and good batteries are hard to move by hand. That's all there is to it.

11 years vs. 4 years by one manufacturer who makes both kinds. Our experience is that the spread is probably even wider than that in real life.

Yes - 48 volt batteries have a base that is twice as wide and multiples safer to move. I could possibly flip my 1650 pound 24 volt battery over by hand - on a good/bad day.

The 11 years vs 4 years seems a wee spectacular if the battery weight is similar. Batteries are frequently touted as being made with some magical pixie dust that board users continue to be mystified by.

I still don't see much difference between forklift batteries and the large 2 volt cells that one of our active members/solar engineers almost always sells. Yet that member claims 5-7 years normal lifespan as I recall. I believe his customers tend to have larger homes thus being heavier users.

kava · January 2019

softdown said:

BB. said:

Since forklift batteries tend to be a bit less efficient and have higher self discharge (especially as they get towards end of life), I would suggest rounding up on your array size (5% what you think you need, go 10%. 10% up to 13%+...).

-Bill

I suspect that the higher self discharge rate is caused by pure lead rather than the more common and economical lead plus calcium battery. Pure lead batteries are often called "high performance" and sell for significantly more. Yet forklift batteries hold their own in the value battle. Likely due to the economies of manufacturing on a larger scale - economies of scale.

As far as I know, Photowit and I are the forklift battery users here. If they were not so difficult to move they would likely enjoy more popularity.

WaterWheel said:

As to the question as to how deep/often to cycle a LA battery the less deeply you cycle the battery the longer it will last within reason. Never cycling a battery will allow the electrolyte to stratify hurting the battery if it goes on for too long.    This is especially true for tall batteries like forklift and L-16 batteries.

Also consider that if you only drain the battery to 90% SOC (state of charge) when recharging the battery the electrolyte may not bubble enough to mix the electrolyte well. You want to drain the battery down to 80% at least once a month so it gets a hard charge bubbling and stirring the electrolyte.

Regularly draining (cycling) a LA battery to 80% SOC seems to be the generally agreed to maximize battery use at a fairly reasonable battery wear rate.

Get and use a hydrometer weekly the 1st two months recording the results, after that you can check SGs monthly. With that automatic waterer installed that may be a little more work to do.    Learn your batteries SGs and how they change as the battery discharges and then recharges. That's how you fine tune your charge controller settings through the seasons and years.

If as more knowledgeable people here have suggested your forklift batteries are close to a 660 amp/hr at the 20 hr rate and keeping in mind that that forklift batteries tend to be a little harder to charge I'd still have say that you've got enough panels to charge at over a C/9 rate which is fine.

If instead you're saving the battery for a SHTF event I'd suggest charging the battery fully, let it sit for 2-4 weeks before applying a load to drop the battery down to 80% SOC and then recharging with a hard charge stirring the electrolyte.

Photowit and Softdown - Thank you for the great information about forklift batteries. We are ranchers and have the means to move the massive battery and using heavy equipment and rollers was the plan. I just can't stand the idea of spending what seems to me could equate to $1000/yr on batteries(or more) due to the short life span of the ones marketed for solar. I am very optomistic and dream of my forklift battery lasting 15-20 years maybe longer with a rebuild or two. That's more like $300/yr.

WaterWheel - Thank you for answering many questions for me. I have to learn more about the self watering system and see how difficult it will make it to check the specific gravity of the cells and maybe add it later in the game instead. The Sol-Ark will allow me to make and adjust settings to do exactly as you have described. I will watch it very closely at first to get to know how the battery is responding - as you have suggested. I do have the ability to add more panels I just don't know how to calculate the need...

BB. said:

Since forklift batteries tend to be a bit less efficient and have higher self discharge (especially as they get towards end of life), I would suggest rounding up on your array size (5% what you think you need, go 10%. 10% up to 13%+...).

-Bill

Bill - I am sorry for asking such a stupid question but when you say "because the batteries have a high self discharge" -" therefore I need to size my array larger"...I don't understand. I do have the array sized larger than my current average power useage...I think. My PGE bill shows 10-16 KWh per day. and the array would be 360 X 14 = 5k....I think? I am still very confused by the math and power vs. usage. I also don't understand how to determine my battery need. I would like at least one days worth of battery, more would be nice because I would rather not run the generator. Assume no grid power available and a cloudy winter sky....how long will my battery last before it is at 50%DOD (the lowest I would want to go if only 3-4 times a year and only if I had to). Do I need more panels?

softdown · January 2019

Since you are equipped to move the forklift battery, I see no great reason to buy another type.

As for "rebuilding" the battery, or almost any other mainstream large battery, I am not aware of that feasibility. Lots of scams out there, a couple of which I have invested and learned from. I have seen used forklift batteries for sale in a "rebuilt" condition. Odd that no poster here seems to be aware of methodology for rebuilding under performing battery cells.

One can replace bad cells with the right equipment, a forklift being the best equipment for this endeavor. I have used an engine lift and an aluminum alloy hay hook with a dull tip. The aluminum straightened enough to be usable yet retained enough curvature to hold unto the cell being lifted. Use oil on the battery cell sides "early and often" when trying to lift out a bad cell.

Estragon · January 2019

Assuming a 24v bank with ~500ah, that's 24x500 = 12kwh. 50% max depth of discharge is 6kwh. If your usage is 10-16kwh/day, your autonomy will be ~ half a day.

10-16kwh/day is on the high side for off-grid though, so IMHO it might make sense to review loads for better efficiency and/or alternate power sources (eg gas range, water heater, etc., instead of electric).

mcnutt13579 · January 2019

softdown said:

mcnutt13579 said:

softdown said:

Only problem I have with forklift batteries is that moving them indoors can be exceedingly difficult and occasionally dangerous. I jumped in the right direction twice when my tall and skinny 1650 pound 24 volt battery fell over in the sand and snow. An experience I will not soon forget.

Seems like the battery in question will be very heavy.

On the grid and buying a huge, expensive battery?

Yes they are heavy. They are wide enough that tipping over is not really a major concern so pipes and rollers are usually good enough. Or just rent a machine for part of the day. If the batteries are that deep indoors then you need to rethink your arrangement. Batteries need to be changed and good batteries are hard to move by hand. That's all there is to it.

11 years vs. 4 years by one manufacturer who makes both kinds. Our experience is that the spread is probably even wider than that in real life.

Yes - 48 volt batteries have a base that is twice as wide and multiples safer to move. I could possibly flip my 1650 pound 24 volt battery over by hand - on a good/bad day.

The 11 years vs 4 years seems a wee spectacular if the battery weight is similar. Batteries are frequently touted as being made with some magical pixie dust that board users continue to be mystified by.

I still don't see much difference between forklift batteries and the large 2 volt cells that one of our active members/solar engineers almost always sells. Yet that member claims 5-7 years normal lifespan as I recall. I believe his customers tend to have larger homes thus being heavier users.

We only have one customer with the huge plastic 4 volt Rolls type cells. They also appear to be a good battery. Just not enough breadth of experience here. I am sure they are expensive. Chinese forklift battery "might" be more bang for the buck but the 4 volt cells can be moved with a hand truck.

Or you can get Solar Ones. They are the gold standard here. You move them close to their destination, unbolt them, disassemble them from the trays and put them back when they are inside.

I am just talking down on L16 and similar batteries. Not the Rolls. Just look at manufacturers specs for cycles @ depth of discharge on an L16 vs a forklift battery. And we have reason to believe the L16 mfrs. might be overstating all their numbers a little. They seemed to last longer in the "olden days". Now they just stink.

The 11 years vs 4 years was from manufacturers specs at 30% DoD. And it mirrors our experience.

mcnutt13579 · January 2019

Another comment. With forklift batteries you get to choose whatever size you want and maintain *one* single string. No more battery string balance issues.

Vic · January 2019

Hi kava,

Did look at the Ark-Sol Manual, just did not see it on their site.

Personally, suggest that you be very, very ... very careful in dealing with this apparently new-to-solar vendor.

Designing Grid Interactive power systems is difficult. Many very experienced companies who have done these types of systems have had a number of problems getting things to work well (Schneider in particular).

After looking at that manual for some time, could not find the degree to which the user could change charge voltages, and saw no reference to just how the Absorb stage is terminated (time or current).

Forklift batteries generally need higher Absorb, EQ and Float voltages than traditional Default settings for Lead Acid batteries. If the Ark-Sol allows the user to set these voltages, it would be good to know their rnages, Absorb termination means and range of settings, Temperature compensation values, and so on ... details matter in this.

Will look at the manual, again, and will look for some detailed specifications as well.

In looking at the Disclaimers in the early pages of the Manual, do not recall having seen clauses like (a) and (b). Are they saying that THEY cannot be trusted to have reliable and honest information?

"Disclaimer UNLESS SPECIFICALLY AGREED TO IN WRITING, SOL-ARK: (a) MAKES NO WARRANTY AS TO THE ACCURACY, SUFFICIENCY OR SUITABILITY OF ANY TECHNICAL OR OTHER INFORMATION PROVIDED IN ITS MANUALS OR OTHER DOCUMENTATION. (b) ASSUMES NO RESPONSIBILITY OR LIABILITY FOR LOSS OR DAMAGE, WHETHER DIRECT, INDIRECT, CONSEQUENTIAL OR INCIDENTAL, WHICH MIGHT ARISE OUT OF THE USE OF SUCH INFORMATION. THE USE OF ANY SUCH INFORMATION WILL BE ENTIRELY AT THE USER’S RISK ..."
(possible copyright Portable Solar LLC).So, PLEASE be very, very careful ... seems to me that there is a lot of Marketing Fluff, and perhaps Hype.If any of us experience an EMP event, it is quite probable that most of us will have many other problems than just those with our power systems. It is unclear to what extent Ark-Sol products do anything to actually deal with EMP.Just some more attitude. Good Luck, Vic (oops, a Font change ...).

Photowhit · January 2019

softdown said:

I suspect that the higher self discharge rate is caused by pure lead rather than the more common and economical lead plus calcium battery. Pure lead batteries are often called "high performance"

There are no 'pure lead' batteries that are standard flooded batteries, as far as I know.

Only a few agm type batteries use pure lead in tight sandwiches. Lead needs to be alloyed to withstand even minor vibrations over time. Car batteries in the US are Lead Calcium in some other parts of the world Lead Selenium is used and has a better deep cycling ability. Here in the USA Lead antimony is the alloy of choice for deep cycle batteries.

While Forklift do have advantages in longevity, they also require regular maintenance. Equalizing monthly or even every couple weeks.

NAWS has sold Crown Forklift batteries and I would post a link to it if I could go to their web site, for some reason I have inadvertently setup as off limits on this computer. They say it's not uncommon for the Crown forklift batteries to last 20 years in off grid use.

As to the warnings about 'short cycling' forklift batteries, I think this is important information when they are used for a forklift! Mainly wanting to prevent people from putting on a charger in between shifts rather than fully and completely charging them. I choose to ignore it rather than discharging my battery below 70% of so.

BB. · January 2019

Here is Crown's website:

http://www.crownbattery.com/products

And, it appears that our host Northern Arizona Wind & Sun no longer carries Crown:

https://www.solar-electric.com/residential/batteries-battery-storage.html

-Bill

softdown · January 2019

Photowhit said:

softdown said:

I suspect that the higher self discharge rate is caused by pure lead rather than the more common and economical lead plus calcium battery. Pure lead batteries are often called "high performance"

There are no 'pure lead' batteries that are standard flooded batteries, as far as I know.

Only a few agm type batteries use pure lead in tight sandwiches. Lead needs to be alloyed to withstand even minor vibrations over time. Car batteries in the US are Lead Calcium in some other parts of the world Lead Selenium is used and has a better deep cycling ability. Here in the USA Lead antimony is the alloy of choice for deep cycle batteries.

While Forklift do have advantages in longevity, they also require regular maintenance. Equalizing monthly or even every couple weeks.

NAWS has sold Crown Forklift batteries and I would post a link to it if I could go to their web site, for some reason I have inadvertently setup as off limits on this computer. They say it's not uncommon for the Crown forklift batteries to last 20 years in off grid use.

As to the warnings about 'short cycling' forklift batteries, I think this is important information when they are used for a forklift! Mainly wanting to prevent people from putting on a charger in between shifts rather than fully and completely charging them. I choose to ignore it rather than discharging my battery below 70% of so.

Interesting in that I have read of pure lead batteries many times, that includes the batteries in my own solar installation. The truth may be somewhere in between your and my understanding.

http://enersys-japan.com/documents/technical "Pure lead offers excellent service life."

An internet search for pure lead batteries yields a large array of possibilities. Though it is true that pure lead is too soft for the thick plates found in forklift and solar batteries. The better ones would seem to employ an alloy with superior properties to the inexpensive metal - calcium that dominates the industry.

Just recently learned that calcium is a metal. "An alkaline earth metal, calcium is a reactive pale yellow metal that forms a dark oxide-nitride layer when exposed to air."

softdown · January 2019

http://enersys-japan.com/documents/technical

Page 7 explains different plate types with longevity explanations. Your browser may show this as 10/32 however.

Seems that pasted plate is the most economical and common - by far. With a far shorter lifespan than available via other manufacturing techniques.

All this time I had thought that mineral quality/purity was the most important variant. According to my link, it may be manufacturing technique:
Plante
Tubular
Pasted plate
Rod plate

forklift battery sizing and prolonging life

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