I Believe the problem is fixed THANKS TO ALL THE HELP on this site. Finally had the tools to lift the battery out. Total four batteries in series, used a hydrometer to check electrolyte levels then filled batteries to just above cells. One cell was about 0.050 different from the rest. Placed that low cell battery on a charger at 8 volts at High amps setting with a cart charger. Watched and checked every 30 -40 minutes. After 9 hours level in that one cell was back to a reading of 1.32 on the hydrometer but batteries were warm. Let battery cool over night, level down to 1.26,charged the other three with the cart charger and then installed it back into pack. Total voltage reading output now is 25.7 volts. There was no charger inside the battery pack. Unit was bought used. Turned key on and battery reading read on handle read 100 percent and all the controls are still working. Ran for a while and placed back in charging mode. Output from charger was now reading 26.8volts. Problem was low water level and one cell far off from others. Will run for a couple of weeks and then recheck electrolyte levels.
On another blog I was informed that the battery under voltage at power amplifier B+ connection will present a fault code at 17V. and the truck functions are allowed unless the voltage drops below 13V.

Thank you again for all the help.

Will check back soon.

It's sold as a kit...4 batteries and charger together. Drop it right in as one unit. Not worth buying a charger and single battery. Gel are less reliable, but lead acid need frequent water top ups and fail if battery is too low.

Thanks for the information you are sharing. I will get the battery pack out to see if it is wet or gel and check the electrolyte levels.

although lawnmower batteries obviously would not work well in this application they did prove the truck is operating as it should once they were connected. The BDI reset and everything went back to normal. You can now rule out any problem with the lift itself.
Now back to the charger and batteries....

To check to see if the charger is going to start charging correctly you can take some jumper cables and connect the charger to those lawnmower batteries in a 24v configuration and turn the charger on
(ONLY BRIEFLY), just long enough to see if the charger is going to ramp up and try to charge them.

If you see the voltage jump up to what you would expect to see on the normal batteries (26v or higher) then you can verify the charger is working.
Do not leave the charger on those smaller batteries very long, just long enough to see what the charger is going to do. You could damage those smaller batteries if you leave the charger on them too long.

The reason i say to try this trick is that i have seen batteries that were so damaged they would not let the charger work correctly and the appearance of what the charger is doing in charge mode is a deceiving symptom the batteries are causing making you think the charger is also bad due to the lack of output voltage caused by the damaged batteries prohibiting the chargers output because of their internal damage most likely an open cell or something. One tell tell sign is to look at the battery(s) themselves, if the sides of the battery(s) are bulging any like they are swelled up that would be a strong indicator.

So... if you get good output from the charger using those smaller batteries then its just the batteries in the lift battery pack being bad.
If the charger does not charge correctly during that test then it also has a problem and needs to be repaired.

If you wind up replacing the batteries keep this in mind, replace them with the same type battery that is in the lift. DO NOT cheap out and try to buy a cheaper knockoff of whats in there. They have to be a specific amp rate and type to run correctly and to interface with the charger correctly. If they are lead acid, replace them with lead acid type, if they are AGM type then replace them with AGM type. If they are lead acid type do not try and go with AGM type because the charger might not be capable of charging AGM batteries and visa versa... an AGM charger may not charge a lead acid battery correctly either. It's just easier to stay with what you have. :o)

good luck

Will pull batteries when I get the forklift running. Placed two lawn mower batteries in series to get 26 volts. Touched the leads and turned unit on then off. Thanks the 26 volts did take it out of the battery save phase. Connected Battery pack up and on the handle battery percentage read 100 percent. disconnected waited 5 minutes and reconnected still read 100 percent and no green light flashing. Everything worked lift, forward and back, emer. brake all worked. Ran it for 15 minutes and percentage still read 100. Have a truck coming in tomorrow to see how long it will last. I'll keep an eye on the percentage and leave it charging again tonight. Battery voltage from the charging unit seemed low to me also. Do not know if this charger phases up (increase voltage) Had VOM meter attached to Batt cables and voltage was still 24.5 VDC

Again any and all advise is greatly appreciated. Thanks to all that replied back. What's my next step?

that's way too low. battery charger needs 26 or more volts to charge the battery. Do you have gel pack batteries or lead acid?

Before I go at what voltage does the Batt light on the handle start flashing indicating a low battery?

Ok made it back and Battery voltage was 24.8 volts with charger connected and 24.5 v with charger disconnected.

Thank you and will check voltage again. Plugged the old Battery into another cart and it ran fine. I placed it on the charger overnight and will check it today. Charger has no meter except a light that changes from red for start, yellow 80 and green 100. Fan was running when I left. I do thank you for the reply.

and by all means, check the charger and make sure it is actually charging the battery.
don't just plug it in and walk off expecting it to be working... wait for it to start, then get a vom and check and make sure.
usually if you hear it turn on and see it on the charger display then you can verify it is on and charging.
if all this is happening then you probably have a bad battery.

24.3 volts is dead. If you swap batteries, they must be fully charged at 25.4 to swing the status back to 100%. Once a battery shows dead, only a fully charged battery will let the truck lift again.
Get a fully charged battery before any more diagnosing. A battery fresh off the charger is best