1988 36v marathon HOT battery

[Cmartin2001]

Battery 2 is one that came with the cart. It's one of 3 that I've not replaced . I'll get some pictures next time I'm in the shop

[Cartmaster]

Listen to bronsonj and Scottyb,

As you know the cart runs, and it seems like most of your issue is with old batteries, I would suggest you go get a new pack of matched batteries and start again. The batteries are the most important part of your cart and need to be strong and healthy. I would also recommend installing all new high amp cables too.

Any testing without healthy batteries is a waste of time.

If you are concerned about the cost, just remember, a running cart these days has a pretty high value so you wont lose out even if you end up selling it working.

[bronsonj]

Originally Posted by Cmartin2001

I have purchased a new 6v battery, replaced cables with 4g. Replaced brushes. Now I hear a slight drag or hissing sound from the motor. I'm not sure if it just the new brushes or if I messed something up. It lasted about 45 seconds before it was crawling. I checked voltage and 1 battery is 4.4 and the rest are 6.3-6.5. And the jump wire from battery 1 to 2 is warm. And battery smells like rotten eggs. Battery 2 is also the 4.4 battery

Battery #2 should not be 4.4v. It's past it's useful life but it has given you what you asked. You were initially wanting to see if there was some major issue before repairing the cart. Now you know the cart works but the battery pack is shot. my guess for the buzzing noise is your brushes aren't seated yet. How bad was the commuter? Was it gouged deeply? If it wasn't too bad they'll seat themselves after a bit of use.

You said you wanted to throw a couple hundred at it per week so what you'd need to do is replace one battery each week until all 6 are new. You already have a head start with some of the 6V batteries you already purchased. Ideally you'd buy all of them at once but I understand we don't live in an ideal world...

That one cable between battery 1 and 2 is faulty or the connection is bad. Did you replace all the cables or just the ones to the new battery? If it's a new cable check to make sure the ends are bolted in tightly. Not too tight... I thought the spec was 20 or so INCH pounds, not foot pounds. Don't tighten the nuts on the battery post too hard, they're just bolts in lead so you can damage the lead and cause a hot spot which can melt the battery post. I use a quarter-inch ratchet to tighten mine when I still had lead acid batteries.

I re-read your post and the initial post said you wanted 4 to 5 hours of drive time. The pack will never give you 4+ hours of time in motion, but if you meant ride for 10 mins, stop at the store, ride for 10 mins, stop somewhere else, then you can have a 4 or 5 hour day with only an hour or 90 minutes of actual driving time in a 15 to 20 mile route. That is absolutely achievable.

[acguy_409]

I just removed and rebuilt the motor for my old 89 Marathon, and it runs better than it ever has. Cannot overstate having good clean electrical connections. There is a vendor on Ebay that has sets of 10 of the replacement solid copper motor terminal bolts, which are better than the originals. I torch/silver soldered them to the brush and field connections, and made new insulators and flat washers with a dremel tool and a sheet of 1/8" Polycarbonate from Mcmaster Carr Supply Co. Bearing was good like new, but check/change yours as required. It is a cheap trade size that is easy to find.
Reassembled and reinstalled.

NOTE: NEVER tighten the nuts down until the bolts spin in the motor housing! Likewise, if they wont come off easily, cut the wire or terminals off to prevent internal motor damage. Remember, electrical connections only pass thru the motor housing with soft insulators. If you spin the field connections, you will be buying a new motor. This is a double nut connection. Use a back up wrench on the second nut, and they only have to be moderately tightened. When you are complete, all motor, battery cables, controller, FR Switch and other terminals (except resistor if you have that type) should be cool/cold after running, and if not, you have more work to do to remove the resistance from the warm/hot area.

NOTE: The bearing retainer plate held by three small screws in the end plate can be started with an extra long screw with same thread size as as the three retainer screws. Thread the retainer plate with the long screw, then pull it up tight to start one of the others. If you have done this task, you have either created a holder or done something like this, because this part of the assembly is a freakin mystery. LOL

[Cmartin2001]

Just wanted to give everyone an update and say thanks for the help so far. I replaced another battery. And the hot cable has moved to a new location. And I'm assuming that all of these heat issues are caused by the oldest batteries. Unfortunately I don't have anywhere local with a good price on Trojans so I've been buying rural king gc2 for 139 each. I contacted plum quick and they wanted me to pull the motor and send them picture. So I did and unfortunately they do not offer an upgrade or a rebuild for my motor. So while I had it off I inspected and cleaned everything I could. There was 1 or 2 wraps of wire on the armature that were smashed in so I prayed them straight the best I could. After I reassembled everything I got the best drive I've had so far. I did notice 1 terminal was warm on an old battery, I noticed while in reverse its a bit herky jerky for lack of a better term until I'm full pedal and it smooths out just fine. Forward is smooth. The cart does sound like a vehicle from jetsons and I'm hoping that's just the new brushes. While driving my meter with alligator clips is showing around 37.6 before take off and around 32 while full speed. I checked the hot termal and that battery was dropping to around 3v while under load. It's finally starting to show some potential and speed. It seems very happy in gravel and on the road however I feel like I lose 5mph in short flat grass.

[bronsonj]

Dropping speed on grass is expected. The one bat dropping to 3v sounds like your next replacement. The pack going from 37.6 to 32v is more of a drop than you want but once you replace the rest of the old batteries it'll be healthy.

Please, please do not replace most of the batteries and deem it good enough... One or two old batteries will cause imbalances when charging and discharging and your battery pack will age much faster and will need replacement much sooner. You may see 5 to 7 years on a good pack that's well maintained (climate affects it too) but you can easily loose more than half if you have a mix-matched pack or if you don't maintain it properly. Maintenance is pretty easy, check the water levels and fill to proper levels with deionized water and if you use the cart plug it in that same day. If you don't use it for a week unplug it and plug it back in.

Glad the cart is showing potential!