91 EZGO Marathon very weak

[cbordea]

thanks for the updates. I'll check those things out when my MM arrives.
My charger is a Lestronic II

[cbordea]

so I checked my pack and it read 37.4v.
I checked each battery and they all read 6.4 or 6.5.
One of the batteries reads 5.7. I disconnected it from the pack and put my single charger on it and it read about 44%.

I think I will try recharging them all individually again and starting over.

I havent' had the chance to check the voltage at the charger and pack or the controller yet. Going to charge them all back up and repeat the tests.

all the batteries are from mid 2011 except one.
had one battery damaged from falling out of the battery tray and I replaced it with a "good one" that my neighbor gave me. That is the battery with the odd reading. it was working fine up until my charger fuses blew. I'm wondering if that odd battery is what is causing the problem.

I'll get the pack charged back up and see what happens.

[cbordea]

Originally Posted by JohnnieB

When your DVM arrives, measure the pack voltage about 12 hours after the charger shuts off automatically. It should be 38.2V for a fully charged 36V battery pack.

I'm hooking up the charger and I'm going to check this again.

Originally Posted by JohnnieB

To check if the charger is sensing the true pack voltage, measure the voltage on the red and black wires going into the control board while the charger is putting out several amps and then measure the pack voltage while charger is still putting out the same number of amps. The two voltages should be identical.

I see the black wire on the control board but I don't see the red wire. Where would the red wire be going to/from?

Originally Posted by JohnnieB

---------
To check the controller, measure the the pack voltage and the voltage between the B- and M- terminals on the controller when the pedal is pushed just far enough for the solenoid to click. Both voltages should be identical.

the voltages are the same. One thing I noticed is that my pedal needs "adjusting" because the solenoid is always engaged. I started adjusting it during lunch but will finish that later. I don't think that would explain the weakness.

Another thing I noticed is I charged the pack the other day individually.
After getting them all to a full charge, I put the 36V charger on the pack.
Saturday morning I moved the cart out of the garage to work on my truck. Saturday afternoon I pulled the cart back in. When I put the charger on the "weak" battery, it was like 45%. I had literally only driven the cart about 100 feet. One of the other batteries, the one right next to the "weak battery" was also down pretty well. The other batteries in the pack were all at about 95%.

With one battery seemingly a little weak, would that make the cart feel weak?
My neighbor has a cart, I might try to borrow a good battery from him. I hate having mis-matched batteries in a cart.

[JohnnieB]

Attached is a schematic of a Lestronic II with the battery sense wires highlighted.

Several times, you've mentioned connecting a charger to a single battery and getting a % reading. Percent of what?
Unless the charger is designed for deep cycle batteries, I would trust any meter on it except an ammeter, or a voltmeter.

Yes, a weak battery will most definitely make a cart feel weak.
Attached is a simplified schematic of a series motor drive system.
Please note that there is a single current path that goes through everything.
Anything and everything in that single current path can and will effect cart performance.

[cbordea]

Originally Posted by JohnnieB

Attached is a schematic of a Lestronic II with the battery sense wires highlighted.

Several times, you've mentioned connecting a charger to a single battery and getting a % reading. Percent of what?
Unless the charger is designed for deep cycle batteries, I would trust any meter on it except an ammeter, or a voltmeter.

My charger is for deep cycle marine batteries. It will charge 12 or 6 volt.
The LED indicator cycles between the battery voltage and the % charged.

Originally Posted by JohnnieB

Yes, a weak battery will most definitely make a cart feel weak.
Attached is a simplified schematic of a series motor drive system.
Please note that there is a single current path that goes through everything.
Anything and everything in that single current path can and will effect cart performance.

oK, I was thinking that if the weak battery was fully charged that it would seem pretty strong to begin with but maybe not last as long. I may try to borrow a good battery from a neighbor's cart to see if that battery is causing the problems.


I think I can also figure out now which wires to check on my Lester II.

Many thanks!

[cbordea]

Originally Posted by JohnnieB

To check if the charger is sensing the true pack voltage, measure the voltage on the red and black wires going into the control board while the charger is putting out several amps and then measure the pack voltage while charger is still putting out the same number of amps. The two voltages should be identical.

ok, I was able to check the voltage at the charger at the red and black wires and it toggled between 38.4 and 38.5. When I checked the voltage at the pack while charging I see the same voltage.

So it sounds like the charger is working and the controller is working and the remaining fault is either the questionable battery or the motor itself.

I'll try to borrow a good battery and verify if that is the problem or not.

Is there an easy way to verify if the motor is still good? The motor is only a few months old.

[JohnnieB]

Originally Posted by cbordea

1. ok, I was able to check the voltage at the charger at the red and black wires and it toggled between 38.4 and 38.5. When I checked the voltage at the pack while charging I see the same voltage.

2. So it sounds like the charger is working and the controller is working and the remaining fault is either the questionable battery or the motor itself.

I'll try to borrow a good battery and verify if that is the problem or not.

3. Is there an easy way to verify if the motor is still good? The motor is only a few months old.

1. I'd check the individual battery voltages while on charge and replace the one or ones that are lower than the rest.

2. The battery isn't questionable, it is bad.

3. The motor is checked every time the cart is driven. If the cart moves, chances are the motor is good. It may not be perfect, but it is working.

An analogy would by speculating whether a car's engine was defective when the fuel tank was empty.
If the fuel tank had fuel in it, the engine would be working normally.
Your cart has a defective battery pack, fix it and the other problems will go away, or at least become real rather than speculative.

[yurtle]

Smarta$$ warning:

Originally Posted by JohnnieB

Unless the charger is designed for deep cycle batteries, I would trust any meter on it except an ammeter, or a voltmeter.

I think he meant wouldn't.

[JohnnieB]

Originally Posted by yurtle

Smarta$$ warning:



I think he meant wouldn't.

I've got to get a better keyboard, this one sends what I type rather than what I mean.

Thanks for the proofreading yurtle.

[yurtle]

I got your back.

EDIT: Unlike spell-unchecker.