Hangcha can supply complete solution to upgrade lead-acid battery forklift to new energy powered (LiFePo4) , feel free to contact with me , give your old forklift second life.

The little bit of resistance in the cables will make no difference. You probably need at least 4AWG wire for that size battery. The larger the better as long as they do not get pinched.

Should all the interconnect wires be the same length or should longer ones be twice as thick to make sure they do not add resistance in series? These are either going to fit in a square or two over, two under on a vented shelf with all precautions against shorts, etc. These batteries were well maintained and used in a cleaning machine since 2017. They are out of service because the new cleaning machine takes a different battery type. All voltages measured good. I paid €75 each. New cost is €469 each. Before this my choices were solar deep cycle 12v 55ah for €76 each x 4 or 12v 100ah EFB for €73 each x 4. I was not happy with either option. I just got very lucky. I rented a car and drove six hours round-trip to get these. They are quality and suited for the task. I'll provide an update when they are installed and working or not, but I cannot imagine why they would not work.

I will try to get her to take them back to the city in winter so they can be maintained.

I would think they would work fine. You will need to do something about the long idle times. The batteries should be used and recharged at least once or twice a month.

Well, I might have a solution. But I really do not know for sure. The label on the original battery reads "Capacity 5h: 174Ah." I just found a deal for 4 6V 180Ah Solar Deep Cycle Sonnenshein GF 6 180 batteries for $99 each. That would give 24 V at 180Ah. Should work, right? Anyone know if I can use the 24V charger of the forklift battery for these in series?

The only real option would be the one that would hold charge for a long period of time sitting idle. I am not familiar with "solar" batteries.

Hi, i didn't make it clear that my original post was considering two sets of two batteries in a series parallel array. One set is advertised for use in solar systems and "forklifts" and would yield 4*55ah @ 24V. The other set is advertised as EFB Stop-Start but also says it's good for forklifts. That array would be 4*100ah @24V. The solar battery claims it can be in an idle state for two years if everything is disconnected. It may be possible to periodically charg either array but that issue can be deferred. I am more interested to know if I should use the solar or the EFB.

You are also not taking into consideration the effect of the batteries sitting for most of a year. Any lead acid battery will sulfate when left sitting for long periods of time. The only real option for this type of use is a Lithium Ion battery. Also your AH calculations are not correct. If you put 2 batteries in series you do not gain AH, you gain voltage. When batteries are put in parallel you gain AH not voltage. So if you put 2 12 volt batteries that are 100 AH in parallel you get 12 volt 200 AH. If the same batteries are put in series, you get 24 volt 100AH.

Thank you kindly for your informative reply There's a bit more to this which appears in a post which seems to have been lost. I only need a few hours runtime two or three times a year, if that. This will be used by the elderly widow of a sculptor to move around some of her husband's very heavy art materials. She used to drive a forklift, so no problem there. About the charger, this was a lead acid system from 1984 which I think nthey acquired in the mid 90's. So, would the best battery choice for me be lead acid deep cycle solar batteries? She certainly cannot afford AGM. I still am not sure if the solar batteries at 55ah would be more compatible with the charger than the 100ah EFB batteries which also claim to be forklift friendly in their literature. What do you think? Solar @55Ah for 220Ah@24v or EFB @100Ah for 24v@400?

You have the right concept but just may have picked the wrong type of battery.
There are 2 types of batteries that are used in industrial applications for smaller walk behind/rider lifts
-industrial type encased single battery that utilizes several cells encased in a box (these are the common type battery used which can be lead acid or non-spillable maintenance free AGM type)
-also there are battery packs which consist of multiple battery's hooked in series or parallel together to create the voltage desired which in most cases is a 24v battery pack. Champion manufacture's these and are common in the pallet jacks and walk behind stacker units and other small lifts used today.

The latter uses deep cycle batteries which is what i assume you are trying to make here. Do not use standard automotive starting batteries, they are not designed for long duration power drain like the deep cycle batteries are. Most battery packs utilize group 31 batteries which is the standard size used in battery packs. They can be either lead acid or AGM. Exide makes a good group 31 battery that is good for these applications called an MC31 or XMC31, the MC31 is lead acid and the XMC31 is an AGM type.
If you want to know more about these you can google exide mc31 or go here and read up on them:
(remove the spaces from the link below and paste it in your browser url bar to go to the site)
ht tps :// w w w.deepcyclemarinebattery. com/reviews/exide-mc-31-and-xmc-31-megacycle-agm-200-sealed-maintenance-free-agm-marine-batteries. html

Note: there is a difference between these two when it comes to charging and the charger needs to be able to support the charging cycle as both do not charge the same way. Just make sure the charger you use supports charging AGM batteries if you decide to use those.