My batteries keep dying and won't recharge!

Thanks for trying to convince to me switch to 12V I guess, but I think I will have to stick with the 6 V system for now or at least until I gain the knowledge needed to do a conversion.

You need someone who can show how to diagnose an electrical system. System voltage is not the problem, either the connections are not allow free flow of current, or the generator is not re-chargeing the battery after starting.
Does this truck have an ammeter? What does it show when the engine is running? What year/model is the truck? the 50's are when the voltage std changed.
A cheap digital voltmeter would be a good start, Wal-mart or a hardware store should have one. CHeck the battery voltage AT THE BATTERY TEMINALS themselves while trying to crank, it will show if the battery is low or if a bad connection is preventing current to get to the starter. Once the engine is started, it will show if the charging system is working.
My 6 volts last just as long as my 12 volt batteries, around 9-10 years in starting duty. Even my deep cycles last, and they are cycled every night to a deep dis-charge. Don't jump to the conclusion that a dis-charged battery is the battery's fault.
As mentioned 12 volt cables WILL NOT DO for a 6 volt system. YOu need 00 or better yet 000 gauge cable (lower the number the bigger the cable) most 12 volt cables are 6 or 4 gauge
Also there are many sizes and capacities of 6 volt batteries just as there are in 12 volt. Make sure that you are buying the correct size. Group 2 is what I use in my K-7 with the original battery box and a Group 4 in my K-7 that had the battery box enlarged. A group 1 is for VW bug's and the like and would struggle with a 6 cyl. Measure your battery box and check it against the battery groups dimensions.
You wouldn't expect a Honda Civic battery to crank a Semi tractor, don't expect too small a capacity 6 volt to crank a 6 cyl.

Thank you! I think my dad has a voltage tester I can borrow so I will have to try that sometime. I have not had the truck running long enough to look at the Ammeter. I just got it running last fall and it takes everything the battery has to keep the engine running just for a few minutes. Does this mean that I might have the wrong size 6 volt battery like you were saying?

Or could I use an 8 volt battery only 6 volt system? My truck is a 1950 l110 by the way.

The 8V thing is frowned upon around here. You're jumping from anachronistic to just plain bizarre.

Short answer is no, you'll be right back where you are now.
The long answer is: a 6 volt battery requires 7.2 volt to charge properly, way below the 8.8 volts of a "8" volt at rest. To charge an 8 volt you need 9.75 volts, way too high for 6 volt stuff, and no 8 volt stuff is made. Stick with 6 or go to 12 with a 12 to 6 convertor for the gauges and heater.
6 volt works, I have started my K-7 below 0 on six volt with no block heater.
lead acid batteries are 2.2 volts per cell at rest, and considered dis charged at 2 volts per cell. A 6 volt battery is really 6.6, a 12 volt is 13.2 volts.
An 8 volt battery is the worse of both worlds.

Quote: .....”no 8 volt stuff is made.”
Correction: I have a 48 volt golf cart sitting out in my shop with six 8 volt batteries connected in series for the 48 volt total. I could go to Sams or any golf cart outlet and pick up 8 volt batteries all day long. They do exist. And for those with 36 volt carts, 6 volt batteries and cables can be purchased as well. The difference being golf cart vs automotive. Certainly there must be some differences.

CB said: and no 8 volt stuff is made. I think "stuff" refers to anything beyond the battery. Your golf cart may run nicely on 4, 12 volt batteries.
6X8 = 48 and 4X12 = 48. I wonder if the Energiser Bunny and a set of pedals could power your cart.

Quote: .....”no 8 volt stuff is made.”
Correction: I have a 48 volt golf cart sitting out in my shop with six 8 volt batteries connected in series for the 48 volt total. I could go to Sams or any golf cart outlet and pick up 8 volt batteries all day long. They do exist. And for those with 36 volt carts, 6 volt batteries and cables can be purchased as well. The difference being golf cart vs automotive. Certainly there must be some differences.

II was refering to the truck in question, The most common use for 8 volt batteries in groups of 3 for a 32 volt system. Quite common back before the REA and also on board ships. There was a lot of 32 volt stuff made back before the 60's. No idea why 32 volt was chose over 36 (which could be 3 12's or 6 six volts)
Worked on a lot of 24 and 48 volt things as well, but has nothing to do with trucks.

I opted for the 8 volt battery in my KB-6 for the cranking power . Really tight rings in a new motor ,Also all new electrical componants and it has been doing fine for about 5000 miles and around 3 years . I think that when I concidered it , I thought of the trickle chargers I have used at other times . Let the frowning begin !!