91 EZGO Marathon very weak

[scottyb]

More like the new smart phone which changes what you type to what it thinks you should say.

[cbordea]

ok, instead of borrowing a 6V battery from my neighbor, I pulled out my weak battery and another battery and put a 12V deep cycle marine battery in. I drove it around a few minutes and it seems much improved. I think I will just pick up another battery and I think that will resolve the issue.

[cbordea]

ok, I purchased a new battery and charged everything up and the cart seems to be working normally again.

I still don't think my charger is charging correctly. We ran the cart a good bit Friday evening and the charger ran all night Friday night and Saturday we rode it a little bit but the charger would never turn off. If I recall correctly the charger usually ramps up to like 30 amps for a period of time and then tapers off to 10 amps after a little while. I don't think the charger is ramping up to the 30 amps and is just charging at 10 amps and is taking a really long time to charge the batteries. Is there a way I can check to see if the charger is outputting correctly? My meter on the charger reads 10 amps whether the charger is on or not. It did kick up to 30amps before my fuse blew. I don't know now if the meter is bad or if the charger is never ramping up to 30 amps.
I checked the battery pack while charging and the red/black wire on the charger while charging and they were the same (38.6 or whatever it was).

I used my multi-meter to try to check the amps from the charger by hopping from each terminal on the meter. I'm not sure if that will actually work or if I have to bypass the meter to check the amps but the amps were 0.0. Any help would be greatly appreciated.

[JohnnieB]

Sounds like your charger's Ammeter is stuck at 10A, but it may be putting out the normal number of Amps.

Attach your DVM's test leads to the main terminals on the battery pack and monitor the pack voltage while charging.

The initial voltage will be whatever the pack was discharged to before it was put on charge.
After the charger starts, the voltage should increase into the 41 - 42 volt range within about 30 minute. Then it will climb more slowly into the 44 - 46 volt range and the charger will shut off.

What is the pack voltage before the charger is connected?
What is the pack voltage 30 minutes after the charger turns on
What is the pack voltage 6 hours after the charger turns on, or if it shuts off sooner, what is the pack voltage immediately before/after is shuts off.

----------
Also, to measure amps, the meter has to be inserted into the circuit and it is very unlikely your handheld Multimeter has an ammeter rage high enough to measure your charger's output current.

[cbordea]

ok, the charger was on all night.
I disconnected it this morning.
about an hr later I went out and the pack voltage was 38.8.
I connected the charger and checked again after 30 minutes and it was 39.8

With the voltage of 38.8 I would have expected the charger to come on for a few minutes and then shut off.

[JohnnieB]

Originally Posted by cbordea

ok, the charger was on all night.
I disconnected it this morning.
about an hr later I went out and the pack voltage was 38.8.
I connected the charger and checked again after 30 minutes and it was 39.8

With the voltage of 38.8 I would have expected the charger to come on for a few minutes and then shut off.

If the charger was charging and the pack voltage being 38.8V about an hour after the charger was disconnected, the 36V battery pack is not anywhere near fully charged.

There are three separate sets of voltages that come into play when dealing with golf cart battery packs:
1. On-Charge voltage: Voltage that only exists when a charge current is flowing through the batteries.
This voltage will climb up to somewhere in the 2.45 to 2.79VPC (Volts per Cell) range, which is 44.1V to 50.2V for a 36V battery pack.

2. Under-Load voltage: Voltage that only exists when the discharging current is flowing through the batteries.
It is best not to load the battery pack lower than 1.75VPC (31.5V for a 36V pack) and never drop below 1.5VPC (27.0V for a 36V pack) since that is where irreversible physical damage to the plates starts occurring.

3. At-Rest voltage: The voltage that exists approximately 12 hours after the charging current ceases to flow or approximately half an hour after the discharging current cease to flow.
Basically, the acid in the electrolyte in close proximity to the plates becomes more concentrated when charging and less concentrated when discharging, so until the concentration equalizes thought the cell, the voltage readings will be artificially high, or low, and not reflect the true SoC (State of Charge) of the cell or battery or battery pack.

-------------

However, the individual batteries should all have close to the same voltage all the time.

What is the pack voltage and what are the individual battery voltages?
All seven voltage measurements taken within about 5 minutes of each other

[cbordea]

ok my pack is reading 38.7
all my batts are at 6.5 except one that is 6.4 and the brand new one is 6.3.
When I put the new one in the pack on Saturday, I charged it separately to about 96% which is about where the others were.
We used the cart a good bit Saturday afternoon.
I charged it all night Saturday.
We used the cart some Sunday, likely drove it 2 miles.
We've used the cart very little since Sunday but the charger won't shut off.

[JohnnieB]

Roughly, how long had the batteries be resting when those voltage readings were taken?

A fully charged 36V battery pack should read 38.2V after resting 12 hours.

--------------

Sounds like you have a 6V charger, if so charge the new battery and the one that reads 6.4V until they reach an On-Charge voltage of 7.5V.

That should bring all six batteries within 0.1V of each other. Or at least closer to being a balanced pack so that they can be charged in series by the 36V charger.

--------------

Unplug charger from cart while it is charging batteries.
Does transformer stop humming, or does it continue to hum?

If it stops humming, then the control board is shutting off the charger like it should.

[cbordea]

the charger shuts off if you unplug it from the cart.
I'll go back and charge each battery individually to make sure they are fully charged and read and on-charge voltage of 7.5.

I appreciate your patience helping me on this.

[TreeBass]

Did this get resolved?