forklift battery vs others

sc solar · December 2014

Hi.
im brand new to the forum and newish to off-grid.
i need to replace my 1st set of batteries and am considering a forklift battery.
My system is 24v and backed by 16 -6v deka 8c11. (4 series of 4)
the battery's are stamped 2nd but bought new. around 200 amps @ 6hr rate
they have been around for 5 years but not so good the last 2.
I also have small solar system that puts off 5-8kwh on good days, i mean sunny days!
and good old generator which charges via xantrex 4024 @ 110 amps dc

I can get new replacements for 100 bucks each. same deka's
or L16 2v 1100 ah interstates for around 200 bucks each (they look to be actually 6v and paralleled?)
and finally the bruiser, a 1-ton new forklift battery with a 6hr of 1000ah and 20hr of 1500ah.
that thing is just north of 3000$ bucks.

so for 2000$ i can get 20 deka batterys and around 1000ah @ 6hr
2500$ for the interstate 2v and around the same amp hours
and the forklift battery for 3250$ and also 1000ah.

so on paper it looks like i should just get the deka's? but i got everyone saying
theirs are better... I would love to get some input. especially actual experience?!?!
Its harder to find than i thought.....
I will say weight-wise that the forklift battery is a good 500-700lbs more than others and
has a better 20hr ah rating. plus 5 year warranty.
thanks all!!!!

Cariboocoot · December 2014

Re: forklift battery vs others

Welcome to the forum.

I think we should look at some possible issues as to why your batteries failed at only 5 years before going on to replacing them.

One thing: four parallel strings of batteries. Even if done 'perfectly' this can have issues with current sharing, meaning some of the batteries do more and die sooner while others do less - and die sooner.

Next, you haven't given any details on the solar regarding how big the array is and its configuration or charge controller. So we don't know if the amount of solar has been providing adequate charging or not. If those batteries are 200 Amp hour @ the 20 hour rate and there's four in parallel that is a hefty 800 Amp hours @ 24 Volts. This would need at least an 80 Amp charge controller (or two 60's, etc) and about 2500 Watts of PV minimum. If this is not the case then there has likely been some deficit charging going on.

The Xantrex 4024's charger should be adequate, but who wants to run a generator all the time?

Now here's something else to consider before buying new batteries; have you re-evaluated your load demands lately? They have a tendency to grow over time, which may have contributed to early battery death. On the other hand you may not need 800 Amp hours and so weren't getting good value for the batteries you've got. That would be about 4kW hours AC @ 25% DOD. Not an unreasonable amount of power.

As for the new battery choices ... I think you are right that those Interstate units are internally paralleled. If there's 3 caps, avoid them. I would avoid that brand anyway, as well as Trojan and Surrette, if at all possible. They all tend to have high Voltage requirements which are not easily met.

Forklift batteries are monolithic monsters and not without issues. There are some forum members who use them successfully, and some who have had difficulty.

I would evaluate the whole system as per my comments above and then try to find the standard cells (Deka/US Battery/East Penn or Crown) that fit the needs. For example there are 6 Volt batteries around 400 Amp hours which would make up the 800 Amp hour bank in two strings instead of four. There are also 2 Volt cells (single cap) which will do it in one string. But you need to know exactly what you're after first, and that the new batteries will be adequately charged by the system.

BB. · December 2014

Re: forklift battery vs others

Welcome to the forum SC!

How many watts of solar panels do you presently have and what brand/model of solar charge controller?

In general, I would seriously think about going to a higher voltage battery bank once the battery AH rating exceeds ~800 AH or so (we use 20 Hour Rates around here for our various rules of thumbs--Closer to how most off grids home use their battery banks).

I personally am not a fan of lots of paralleled batteries... One string is probably ideal, with 2-3 parallel strings being a practical maximum of paralleled batteries (cost of wiring, maintenance, cell to check for water levels, sharing of current, etc.).

3-5 years is OK life for inexpensive golf cart batteries that have been well used (not great, but not real bad either).

How have your batteries been treated? Water levels kept up with distilled water. Monitored/logged specific gravity? Checked Battery/Cell voltages (looking for open/shorted cells/batteries). Do you have a DC current clamp meter so you can measure per string battery current (are they sharing charging/discharging current well)? Is your bank wired for "equal length/resistance" wiring for each string?

If you have guests/kids come by for visits--Getting cheaper batteries is sometimes better--If they take the batteries dead (for example, while you are not there)--You have a less expensive battery bank to replace.

Always suggest that battery bank be sized to your loads... Too large of battery bank can be an expensive pain in the behind (more water & cell maintenance, need larger solar array to properly charge, etc.).

How much energy per day do you need? Are your sunny day loads much different than your dark day loads? We generally suggest a 2 day storage battery with 50% maximum discharge, or:

5,000 WH per day * 2 days * 1/0.50 max discharge * 1/24 volt battery bank = 833 AH @ 24 volt battery bank
8,000 WH per day * 2 days * 1/0.50 max discharge * 1/24 volt battery bank = 1,333 AH @ 24 volt battery bank

If your present battery bank (~940 AH @ 24 volt using the 20 Hour Rate or AKA C₂₀ rate) works well for you--I would not go any larger. especially at 24 volts.

We recommend around 5% to 13%+ rate of charge for solar power... 5% works OK for a weekend/season cabin/home. 10% minimum is recommended for a full time off grid home. ~13% rate of charge is usually the cost effective maximum for the average off grid residence (charge during the day and use power in the evening/bad weather).

940 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 1,770 Watt array minimum
940 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 3,540 Watt array nominal
940 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 4,602 Watt array "Cost Effective" maximum

Note that the largest residential charge controller is around 80 to 94 amps (Midnite classic 150) on a 24 volt battery bank... So if you go over >~10% rate of charge on a 24 volt battery bank, you would need a second (~$610 charge controller).

If you go to a 48 volt battery bank, your charge controller can manage a ~2x larger solar array (of course, you would need a new 48 VDC inverter or inverter/charger--Not cheap either).

Lots of choices here. No RIGHT answers, but lots of shades of gray.

-Bill

Photowhit · December 2014

Re: forklift battery vs others

The deka 8c11 is a agm type battery, Switching to a flooded battery will mean you'll need to check them regularly and add water when needed and equalize it they get out of balance and perhaps a maintenance equalizing monthly. Switching to a forklift/traction battery will mean missing a monthly check may expose plates and early failure! The forklift will also have a higher self discharge rate and higher water usage. I have switched to a forklift battery and have found the change not too bad, but I had been using flooded batteries previously and checking them wasn't a new experience.

The unspoken part of the equation is that the 2v cells should last 8-10 years and may go 15 when well maintained. Forklift may go 15-20 years when well maintained.

Forklift/Traction batteries demand attention compared to agm batteries. I'd suggest using a set of standard flooded batteries before making the switch to a forklift battery unless you have very good attention to detail and are very good with scheduled maintenance.

sc solar · December 2014

Re: forklift battery vs others

thanks for the info!
i wrote a long reply sunday but was logged out so lost it all!
i do have deka lead acid batteries, they say 8c11 or 9c11?, water them every 1-2 months
http://www.dekabatteries.com/assets/base/0009DekaScrubberSweeper.pdf

-photowhit. i guess im not sure what higher self discharge means?
shouldnt they be low self discharge with being how long they last?

-bb and cariboocoot. i cant upgrade to 48v now. it would be near another 4 grand so maybe in the future.
my batteries actually lasted longer than i thought. they were treated ok, but never tested each cells volts or specific gravity.
wired up ok with equal length welding cable.
Im definitely going to keep closer eye on new batteries, especially at 1st im sure...
also, thanks for being clear and throwing out some examples:)

I would estimate our watt hours usage between 4k and 7k daily. our system puts out 1500-1700 watts max for 4-6 hours and the xantrex mppt 60-150 controller tells me around 6-8kwh on sunny days. and our old batteries, even when new, would only last 1 day, then top em off with generator at night for 1-3 hours. which is why i wanna go bigger battery and solar as well

now im a bit concerned about your suggestion of not going over 800AH on 24v...
Is it really that much more efficient to have a 48v system with 750AH vs 24v system with 1500AH??
I get the charge controller @ 48V harvesting almost twice the power.
a big deficit you helped me realize is my 24 volt inverter is only good for 120v not 240v also.
I guess that always limits my charging as well..(hard to find generator with more than
a 30 amp plug and capacity @ 120v..)

another big question about this 24v forklift battery. it has a 20 hr rating of almost 1600 AH! and 6 hr of only 1000 AH. Its a common figure for a 12-125-17 battery. thats a huge difference vs my golf batterys being @ 1000AH and 800AH? is this correct?

If I can only charge @ 120 amps dc, would it take 6hrs of running my generater if i run my batteries down to 50% ?? sorry for the novice questions..

Looks like i need at least 3000 watt solar system also.....

Cariboocoot · December 2014

Re: forklift battery vs others

Couple of things to mention.

When your charge controller says "6 kW hours" that isn't how much power you've used, it's how much it has produced. If you use more than that the batteries are in a state of deficit charge. Conversely if you use less than that it's because some of what is produced for charging is lost in the charging process; it is quite normal to need 20% more power from the PV than you actually use.

Going about 800 Amp hours on any system Voltage immediately presents a problem in that the largest charge controller you can get is 80 Amps (roughly) which is 10% of 800 Amp hours. More battery needs more power and more PV, so when you hit that threshold you automatically have to shell out more money for a second controller. Going up in system Voltage where possible eliminates this problem and increases system efficiency a couple of percent (power supplied more as Voltage than current = less loss to heating).

Multiple parallel battery strings can cause problems. More so at lower Voltages than higher ones and there's no certainty that there will be problems, just the possibility.

Battery charging isn't linear. A 1000 Amp hour battery depleted to 50% SOC will not recharge as 100 Amps for 5 hours, unfortunately. Exactly how long it will take to recharge depends on the battery's efficiency and a few other factors.

You really only need to look at the 20 hour rate for RE use; that is what we use to make all the calculations and predictions. Think of it as 20 hours of the day drawing from the battery, 4 hours of the day recharging and running from solar: 24 hours in the day.

gww1 · December 2014

Re: forklift battery vs others

sc solar

You mention 6 hr and 20 hr amp hour rating. I have 48 volt fork truck that is 510 at 6 hour rate and 800 amp hour at 20 hour rate. One thing to consider is it needs to be charged with very high voltage to raise the sgs. This goes up as it gets colder. Some inverters may not like this high voltage. I have no trouble with outback inverters.
Cheers
gww

Photowhit · December 2014

Re: forklift battery vs others

sc solar wrote: »

i do have deka lead acid batteries, they say 8c11 or 9c11?, water them every 1-2 months
http://www.dekabatteries.com/assets/base/0009DekaScrubberSweeper.pdf

I couldn't get your link or any Deka to open at the moment, perhaps they are working on the site, next link down on the google search had this;

Deka 8C11 is a 6 volt 235 Ah valve regulated (VRLA) AGM battery. It is completely sealed lead acid battery with valve regulated. Valve regulated, spill proof construction allows safe operation in any position.

Perhaps that is where I got the info, but it's unlike me to take a 3rd parties word.

sc solar wrote: »

-photowhit. i guess im not sure what higher self discharge means?
shouldnt they be low self discharge with being how long they last?

How long they last in years is different in how long they stay charged with out being charged.

sc solar wrote: »

i cant upgrade to 48v now. it would be near another 4 grand so maybe in the future.

Why? If your replacing the batteries now, the additional cost is the inverter minus one of perhaps 2 additional charge controllers.

sc solar wrote: »

now im a bit concerned about your suggestion of not going over 800AH on 24v...
Is it really that much more efficient to have a 48v system with 750AH vs 24v system with 1500AH??
I get the charge controller @ 48V harvesting almost twice the power.
a big deficit you helped me realize is my 24 volt inverter is only good for 120v not 240v also.

There are certainly 24v inverters that output 240v AC

sc solar wrote: »

I guess that always limits my charging as well..(hard to find generator with more than
a 30 amp plug and capacity @ 120v..)

I'm not a generator guy, but 30 amps at 120v AC is 150amps DC in wattage, no perfect conversion, but a reasonable charge rate likely for up to a 1200Amphour battery bank.

sc solar wrote: »

another big question about this 24v forklift battery. it has a 20 hr rating of almost 1600 AH! and 6 hr of only 1000 AH. Its a common figure for a 12-125-17 battery. thats a huge difference vs my golf batterys being @ 1000AH and 800AH? is this correct?

Yep! different chemistries and plate sizes, My lift battery is 510amphours at 6hr and 804 at 20hr.

sc solar wrote: »

Looks like i need at least 3000 watt solar system also.....

For what size battery bank, 3000 would be for a 800 ah 24 volt, likely recommend around a 6000 watt array for a 1500ah 24 volt battery bank.

sc solar · December 2014

Re: forklift battery vs others

Its been raining a lot in the bay area.
havent seen the sun in 2 weeks!
got this massive battery a few days ago.
1800 pounds sure is heavy, so i hope it lasts for a long time.
i have some concerns maybe you all could help me out with.
this is a 12-125-17 battery. supposed to be 2 rows of 6 blocks or cells all in series...
it was delivered to house. and when i get it i noticed that its actually what looks like
12 -4v cells in parallel (2 banks of 6), instead of 12 -2v cells in series...
I was a little upset and bummed, but then realized i could always just turn it into 48volt!?
I still feel a little duped and wonder if this is a fair deal for this battery?

but for now, i have even more reason to go 48v.
ive been thinking also, since my inverter is about 10 years old, i can use it for
backup and this way i can configure 24v if something happens to a battery cell as well.
we have no backup right now, it would be much more assuring if we did.

supposedly my battery is 1500 Ah @ 20 hrs. @ 24v
so if i make it a 48v battery it now 750 Ah right?

i keep hearing the charge amps should be 10% of battery AH.
so 75 Amps @ 48-56 charging volts = 3600-4200 watts max?

right now, my sw 4024 inverter charges @ 120 dc amps max via generator. i have it set on 24 amps ac.
it doesnt like it when i go over 24 amps even tho inverter is programmable to 30a...
so about 2800 watts.
All @ 120v ac, no 240 volts.
so its a lot on my generators 30amp circuit, but,
I really like the fact that i can get away with using a smaller, quieter, and more efficient
generator to charge my battery when needed..
instead of a bigger 240v gen. which seems more wasteful since i can get away with
3-4kw to charge anyway?

Now, if i did pick up something like a xantrex xw 6048 which has 100 amps continuous charge current, wouldnt that be too much for my battery?
thats like 5kw.
it would be nice to cut that charge time down on these cloudy weeks tho...
or when my solar can chip in also!
since i have that 60amp charge controller i plan to max that out with the addition of the
48v system..

so thats where im at right now, might be awhile before i get that 48 volt inverter,
and plan to research all of them 1st. heard a lot of good things about outbacks even though my xantrex has done well.
thanks for the good advice!

BB. · December 2014

Re: forklift battery vs others

I don't know the details of fork lift batteries--But there are no 4 volt cells. All lead acid batteries are 2 volt cells. So--There may be something about two "integrated cells" (two caps to check water levels) being a 4 volt module????

-Bill

Cariboocoot · December 2014

Re: forklift battery vs others

Did you check this battery with a meter and see how much Voltage is available from the end terminals?

I think you meant twelve 4 Volt cells in series. There's really no such thing as a 4 Volt cell, but perhaps they are blocks of 2 Volt cells paralleled and then the twelve blocks are in series? A picture of it might make things clearer.

Yes if you reconfigure a 1500 Amp hour 24 Volt battery to 48 Volts it becomes 750 Amp hours. The 10% rate on that times minimum Voltage plus typical efficiency rating works out to (75 Amps * 48 Volts / 0.77) 4675 Watt array minimum.

Just because an XW is capable of 100 Amps doesn't mean it has to be set for that. Nor would that battery suffer from receiving that much (13% peak current - no problem).

The 60 Amp controller (3740 Watts on 48 Volts) will be at 8% and that would be a bit lean. Add more controller capacity or switch to FM80 or Classic 150 that can handle 80 Amps and panel it up full.

Outback inverters are better than Xantrex in certain key areas, such as the performance of their built-in chargers.

Rossman · December 2014

Re: forklift battery vs others

sc solar wrote: »

I guess that always limits my charging as well..(hard to find generator with more than
a 30 amp plug and capacity @ 120v..)

They actually make "cheater" cables for this (combine multiple generator outlets to one larger outlet)...like this: http://www.wisesales.com/50-amp-rv-box-adapter.html

Whether they are a good idea or would even be useful to you is another matter altogether.

sc solar · December 2014

Re: forklift battery vs others

Attachment not found.
hope this works
heres the new vs old.
it has 4 lugs per block.
12 blocks

Photowhit · December 2014

Re: forklift battery vs others

sc solar wrote: »

got this massive battery a few days ago.
1800 pounds sure is heavy, so i hope it lasts for a long time.
i have some concerns maybe you all could help me out with.
this is a 12-125-17 battery. supposed to be 2 rows of 6 blocks or cells all in series...
it was delivered to house. and when i get it i noticed that its actually what looks like
12 -4v cells in parallel (2 banks of 6), instead of 12 -2v cells in series...

Saw the picture it has 1 cell for each watering cap... 12 cell or a 24 volt battery.

The numbers 12-125-17 indicate the battery has 12(cells) - 125 amps per positive plate(6 hour rate) - 17 plates - 8 of which are positive, per cell

sc solar wrote: »

I was a little upset and bummed, but then realized i could always just turn it into 48volt!?
I still feel a little duped and wonder if this is a fair deal for this battery?

but for now, i have even more reason to go 48v.
ive been thinking also, since my inverter is about 10 years old, i can use it for
backup and this way i can configure 24v if something happens to a battery cell as well.
we have no backup right now, it would be much more assuring if we did.

Obviously you aren't going to change a 24v battery to a 48v battery, Likely the reason for the extra connectors is the possibility of higher rates of current on such a large battery.

sc solar wrote: »

supposedly my battery is 1500 Ah @ 20 hrs. @ 24v
so if i make it a 48v battery it now 750 Ah right?

i keep hearing the charge amps should be 10% of battery AH.
so 75 Amps @ 48-56 charging volts = 3600-4200 watts max?

right now, my sw 4024 inverter charges @ 120 dc amps max via generator. i have it set on 24 amps ac.
it doesnt like it when i go over 24 amps even tho inverter is programmable to 30a...
so about 2800 watts.
All @ 120v ac, no 240 volts.
so its a lot on my generators 30amp circuit, but,
I really like the fact that i can get away with using a smaller, quieter, and more efficient
generator to charge my battery when needed..
instead of a bigger 240v gen. which seems more wasteful since i can get away with
3-4kw to charge anyway?

Now, if i did pick up something like a xantrex xw 6048 which has 100 amps continuous charge current, wouldnt that be too much for my battery?
thats like 5kw.
it would be nice to cut that charge time down on these cloudy weeks tho...
or when my solar can chip in also!
since i have that 60amp charge controller i plan to max that out with the addition of the
48v system..

so thats where im at right now, might be awhile before i get that 48 volt inverter,
and plan to research all of them 1st. heard a lot of good things about outbacks even though my xantrex has done well.
thanks for the good advice!

Your stuck with a 24 volt battery now, if you want to go 48, you can return this one or add another...

sc solar · December 2014

Re: forklift battery vs others

quick question.
is it ok to connect my charge controller to my inverter @ the battery lugs?
i have 5' of welding cable connecting my battery, from terminals to inverter.
i dont see whats the difference if connect charge controller straight to batteries terminals vs 5'
away at inverter lugs?
only reason i ask is its an easier connection with configuration.
either way is doable, im more just curious.

also. i also would like to know if cell voltage and charge bulk, absorption voltages are the same
for this battery as it is for every battery?
I usually charge to 28.8, but not sure what would be 50% capacity or even 20% (which i dont want to do)
so far, i have not seen the new batterys voltage above 25.2 resting.
and turn on generator when it hits 23.8.
thanks!

BB. · December 2014

Re: forklift battery vs others

Connecting to the battery or battery bus is usually better. The battery acts like a giant filter capacitor.

When you connect to the DC input of your inverter--You have some wire resistance and inductance. It makes for a noisier electrical connection on the DC input of the inverter (120 Hz of sine squared noise from inverter).

Electrical noise has been known to confuse some charge controllers (my guess is that MPPT charge controllers would be more susceptible to "confusion").

It won't hurt anything if you try it (in general).

I could foresee some issues if you have a fuse pop or somebody opens a circuit breaker and you end up with the Charger connected directly to the inverter's input. You could end up with some damage due to voltage surges, etc.

The other down side is that the fusing for the inverter wiring is typically larger than the fusing for a charge controller (250 Amp fuse for a large AC inverter vs 80-100 amp fuse for a larger charger). You should put a second fuse/breaker between the Inverter DC wiring and the Charge Controller's DC wiring if there is a difference in wire gauge/current ratings.

And, in you also run into issues with available current--You now have the DC current added in from the charge controller (depending on size of charge controller's rated output current)--The wiring needs to be sized to carry both the battery current and the charge controller's output current to prevent wire heating in the event the inverter has an internal short circuit or is overloaded.

-Bill

Cariboocoot · December 2014

Re: forklift battery vs others

sc solar wrote: »

quick question.
is it ok to connect my charge controller to my inverter @ the battery lugs?

Don't.
Not only for the reasons Bill suggests but also because the charge controller will not stand much chance of properly measuring battery Voltage at the inverter input terminals. Load changes = Voltage changes = controller does ... whatever.

And if the inverter fuse/breaker trips; no charging from the solar.

And if you want to shut the inverter down so it draws nothing - again you lose charging.

You can start out with the standard default 24 Volt system settings, but be assured you will have to make adjustments to what suits the battery (and your system) best.

25.2 resting Voltage is not too far off what would be expected (25.5) and may be within temperature compensation range. Usually 24 Volts while under load is a guarantee of >50% SOC, but you can adjust that downwards to compensate for known loads (especially heavy ones) that need to be accommodated.

jtdiesel65 · December 2014

Re: forklift battery vs others

I have the BBI 12-125-17 1576 AH forklift bat. It's 12 2v cells in series. My lugs are in a different location in the middle of the battery on one side.

I've been using these settings for quite some time

float 27
absorb 29.6
eq 31
max absorb 3 hrs

I've more recently switched to
absorb 29.8 and absorb time 2 hrs. which then I moved to 2.5 hrs when winter hit

Seems 3 hr absorb in summer is overkill relative to SG readings, but 2 hr absorb in winter is underkill.

Gen auto start triggers
30sec 22.5v
15min 23.5v
2hr 24.3v
24hr 24.6v
Gen max charge 180 amps

I've been hitting the 2h trigger which seems to be about 65-70% range. I'm considering lowering it a small amount. Never seen the battery drop into the under 24v area.

forklift battery vs others

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