Phillip the only answer to your question is a massive no the machine would never pass a loler inspection in the uk without the correct specification/weight battery in it and like it or not the truck legally requires a 12 monthly loler carried out by a competent person. The battery in an electric fork lift truck is part of the ballast needed to safely lift the rated load. Fit a lower different capacity battery in the truck and have an accident and your the one in court on a manslaughter charge mate

Swoop; Totally agree with you. For whatever it is worth, let someone get hurt on this lift , lawyers will get involved and the can of worms the insurance companies will open up on you will cost you more than the money you saved not using the proper battery type and weight.

philip_m,
the one thing you guys that want to put these smaller batteries into trucks that normally take these large industrial batteries are not considering is that you're not taking into consideration that the battery is also a counterweight. If you try and put these smaller batteries in you deminish the trucks ability to pick up a rated load. The stability of the machine is severely compromised when you do this.
Also in todays control systems they are designed to run on a specific amp rating versus the voltage and these systems are very sensitive to the fluctuations caused by using such a small array of batteries. Even though you may get the truck to run voltage wise, the battery array's amp load is not sustainable using these small cells and the control system sees this and will fault out in most cases because of the wrong type of battery.
But as i said at first, the MOST important fact the truck stability, you NEED the weight from the battery to keep the truck stable when lifting loads.
If you're just building a battery pack to move the machine around then it MIGHT work for that, but don't use it for your normal power source fulltime.

Your best bet is to get the old battery (if you still have it) reconditioned.
And a note about reconditioned batteries is that they are not going to be like a NEW battery and you will still be prone to dealing with any weak cells that were deemed good at the time of reconditioning that would be prone to fail at a later time. Any cell in a battery no matter how big or small are only designed to be charged and discharged a certain number of times, anything you get after that fact will be based on how well it has been maintained over time. They ALL will fail eventually once they reach and or go past their cycle time.
In short, a reconditioned battery is just buying a bit more 'uncertain' time is all.

I have a 72 volt forklift and was thinking of putting 6 12 v 110 amp leisure batteries in it. Would that work

Swoop223 is spot on folks.
A set of deep cycle batteries are OK to put on a cart & move lifts around the shop or into trailers but that is all - we did all the time when I wholesaled used lifts. The run time/charge wasn't all that good ~3 hours ( primarily driving). The cart was set to pick up 24v, 36v & 48 v. Plus, occassionally a battery would explode from over charging so we put a lexan shield over the top.
I would hate to say in front of a judge & jury - I made these unauthorized modifications to save money... you loose and maybe more than money.
Shade tree/backyard engineering has hurt & killed folks & there is no such thing as a planned accident. Jacked up pick-up trucks roll over all the time. I knew two young men that lost their lives when there "Cool" truck left the road.

i would not recommend ANY of these backyard alternatives for batteries. These lifts are designed specifically for a certain type of battery and these batteries are also factored into the counterweight properties of the truck. If you try anything other than factory recommended batteries you are asking for a whole sleu of problems and putting yourself at high risk for injury and damaging the lift as well.
You may look at the cost of a battery for this truck and think its too much but look at the cost of any lawsuits, insurance claims and medical expenses and property damage or even a life taken that may occur because of things that will happen due to your negligence and unwillingness to install the right batteries because of cost?

This is a no brainer fellas....
Put the right battery(s) in your trucks so you can sleep at night knowing everything is safer and working as it should be.

A set of 6 deep cycle golf cart batteries might be a way to go for a bit more weight and run time.

Good thing I did not post seeking approval. I am posting simply to show an alternative to expensive batteries and chargers for us lift users not needing a huge investment to move small loads around the shop. As far as battery life is concerned I talked to the experts at batteries plus and explained the use. My lift draws around 25 amps which is well below what three 4 D. Agm batteries can put out without overheating. These batteries are good for over 1000. Charging cycles. I have been using this for a while now and disagree about backyard engineering being history. Some of us have made a nice living out of such engineering. You should see what my tractor can do.

You will have issues down the - those batteries do not have that amp hour capacity that an industrial batteries has - those batteries will have a shortened life real soon. When the motors are under load - lift, tilt, side shift steering and drive function they will draw down the amps of the battery quickly and the battery voltage will drop below 36 v (undervoltage condition) and electrical & electronic components will over heat, brushes wear, etc.
Realtive to safety & potential liabilities & OSHA - no one on here will approve what you are doing -you are on your own. The days of back yard engineering are history - gotta' follow what the manufactuerer says and say not to do.
Good luck

I have a similar situation but my lift is 36 volts. I bought 3 of the AGM 4D batteries from batteries plus and hooked them together with heavy duty top post terminals. I can operate for a couple of hours with no noticeable decrease. I added cement blocks to make up for the loss of counterweight since the old battery pack was 1800 lbs. I now have about 800lbs. I am mindful of this and am careful. However it is very stable and I use it for 2000. loads and less most of the time. I bought a maring 36 volt charger for 199. and it keeps it charged and ready to go. I have been very happy with this fix and it works for my shop very well

Hi There
Are you looking for good deal?
If you're used to work with 1 to 500 forklifts....
We can offer to cut down on expenses at least 50% into batteries.
Plz feel free to send email at philippe dot alan at gmail dot com

The lift I was refering to is only used 3 to 4 times a week to unload a truck.I have a clark standup and normaly only run it 15 to 20 min when I use it,pull a engine lift car to check brakes,rotate tires ect.So I did asume if it was at your home you wont use it much.I do have correct battery in mine and dont know the range of the one I was telling about.It will at least last long enough to unload a truck.

often, to move a forklift around the shop or test motors, pumps or controllers, it is fine to use multi 12 v auto batteries in series to provide the correct voltage, and yes, they only last a short time compared to an industrial motive battery.

I have a customer running 1 lift on 4 12 car batterys with junk in the compartment.Has batterys hooked to charge with a 24 volt charger.Firts 2 then 2nd 2.We dont work on that one so I dont know anything about it as far as paper work is involved.The Junk is for extra ballest by the way.Been running 2 or 3 years that way.

Yeah, counterweight shouldn't be too much of a problem. This is at home, so no osha and I won't be lifting too much in the heavy department. I'm just wondering if the batteries will over heat or work for a short time. The 4d battery is intended for boats I think and I'm not sure what the deep cycle version is for, but it is much bigger than a car battery -20" long by 5.5" wide by 10" tall. I don't think car batteries will do the job, but no one seems to know about these larger ones.
Thanks,
Mark