dcs voltage drop when tow/run switch on run

[mwerlinger]

I have a 1997 dcs that i just purchased. I know my way around electrical a bit, but have never worked on a cart. I traced the wires to make sure they are hooked up right, and have good voltage at my batteries. The problem is when i put the tow/run switch to "run", the voltage reads nothing on the solenoid and then eventually works its way up to half of what the batteries read when the switch is in "tow". BTW the cart does nothing. Can you please tell me where i need to be looking first? Thanks!

[JohnnieB]

Welcome to BGW.

Check out the Sticky: Labeled DCS Troubleshooting at top of this forum. (One menu level up from where we are now)

There is a wiring diagram if you don't have one.
More important, open the two attached .PDF files.

[mwerlinger]

I've got the diagrams already. I'm really wondering if the controller gets power and then sends regulated power to some components or if power just travels to it after batteries send the power to the separate components. The voltage drop is confusing as heck to me. Maybe I should check again for grounded wires. I did see a post that said they put the volt meter on the frame and that told them they had a problem.

[JohnnieB]

For starters:
1. What is your battery pack voltage? If it is less than 38.2V, the battery is not fully charged.
2. There are FOUR terminals on the solenoid. Which one of the four are you attaching the "+" Lead of your DVM to and where is the "-" Lead attached.
3. There is NOT a step in the troubleshooting procedure(s) that makes a voltage measurements with the Run/Tow switch in the Tow position.

Do yourself a favor and just make the seven voltage measurements listed in the file DCS.PDF.
When your cart is working, the ghost voltage will most likely vanish anyway.

Note: All the measurements in the DCS,PDF file are referenced to B- at the battery and when it says 36V in the circle, it really means whatever your battery voltage (B+) is.

FWIW:
The current paths highlighted in RED on the last seven pages in the file "DCS.PDF" shows that everything except the motor and throttle (ITS) are powered directly from the battery.

Unless the frame is grounded (Tied to B-) and a control wire is shorting out on it, a grounded frame is more of a safety issue than an operational one.

[mwerlinger]

Thanks I'll look at those last pages a little better. It's just strange. I've been working with the batteries a little over 30 volts. I've separated them into 12 volt pairs for reconditioning. All pairs are between 11.5 - 12 volts. So when I hook them up I'm losing a little. I am hooking my dvm to the battery side and the B- terminal. What kills me is when I flip the switch to run, I start out with like 4 or 5 volts and I can watch the voltage start climbing real slowly. The highest I've measured is 15.6 volts. That was after letting the thing sit forever.

[scottyb]

The cart will not run on 15v. In fact DCS carts have a well know short fall. That is they smoke the speed control in low voltage situations... low voltage being 30v. I would never try to operate it with less than 37v in the pack.

[mwerlinger]

Well I will give them a good charge and hope I didn't blow anything up. If I did, looks like I'll be putting a new controller in. What an expensive lesson lol

[JohnnieB]

Attached is a chart showing open circuit voltages vs State of Charge. As you see, 30V for a 36V battery pack is completely off the bottom of the chart.
Basically, what you've got is six plastic boxes containing lead and sulfuric acid that weigh about 60 pounds each. Whether they are batteries or not, is open to interpretation.
They are batteries because they have a voltage across the poles, but so is a potato with a couple pieces of dissimilar metals stuck into it and potato cells might make a better battery than what you've got.

On the brighter side, with the additional information provided, I can answer your original question.
With the Run/Tow switch in the Tow position, the controller draws no current so the "Battery" has no load. When the switch is toggled into the Run position, the controller draw enough current to drop the 'Battery's" voltage to zero, or near zero. The time it takes for the voltage to rise is a RC Time Constant determined by internal resistance of the depleted batteries and the capacitance within the controller. There are a couple other factors involved, but that is the bulk of it.

Can your batteries be saved? I don't know. If they only came up to 11.5-12.0v per pair when they were charged with a 12v charger, I doubt it.

Also on the brighter side, that set of batteries might not have had enough power to blow the controller. I'd wait until I had a set of batteries good enough to troubleshoot with before I bought a new controller.

[scottyb]

Basically this is why the DCS system was upgraded to the PDS system. The PDS has a low voltage lockout somewhere around 26v and roll away protection.
Whenever you see a DCS cart with bad batteries and a stock controller, chances are 50/50 it needs batteries and a control.

[mwerlinger]

In the event that I need a controller, would you reccomed an upgrade to pds or there is bound to be a dcs controller that will shut itself off these days?