99 ezgo txt slow speed and slower going up hills

[Jmack14]

your first thing there "1)very bad idea to feed amps to a stalled motor" what do you mean? did I say that I did that or are you just warning me?

on the 3) thing even while driving at full throttle it never gets above that is that still normal?
I totally understand the thing of carts going uphill(this is not a hill it is a slight incline and carts speed is 2-3 mph i should have clarified the hill thing) slow down but I'm telling you I have drove others and this is not right

tires call for 15 psi max and that's what i have in them

[scottyb]

I'm thinking this just may be a bad F&R switch.

[JohnnieB]

Originally Posted by Jmack14

your first thing there "1)very bad idea to feed amps to a stalled motor" what do you mean? did I say that I did that or are you just warning me?

on the 3) thing even while driving at full throttle it never gets above that is that still normal?
I totally understand the thing of carts going uphill(this is not a hill it is a slight incline and carts speed is 2-3 mph i should have clarified the hill thing) slow down but I'm telling you I have drove others and this is not right

tires call for 15 psi max and that's what i have in them

You effectively said that. "1)With batteries all connected and cart against wood block to create a small load, all batteries were holding above 5.9 volts individually."
If the cart is against a wood block, the motor is stalled.

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At full throttle, you should have whatever the battery pack voltage is at the time between M- and B+. If not, there is a problem and it could be anything from a bad controller to a bad throttle to a bad battery pack to bad high current cables to a bad F/R switch to name a few possibilities.

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Good that the tires are 15 PSI. Those ought to get you closer to theoretical speed.

[Jmack14]

it would be nice scottyb anyway to test

[yurtle]

An under load reading is more in line with what the batteries see. You gave us a pack voltage while climbing the slight hill. Assuming you have a DMM, hook it up to each battery while climbing the hill.

[Jmack14]

i understand what you mean now johnnieb

that voltage never gets above 16-18 volts between B+ and M- so i have tried my controller in a working cart as well and still performs like its suppose to in that cart, batteries keep checking out ok, cables all appear to be ok and are not getting hot due to high resistance(i assume they would if resistance was there?) anyway to test f and r switch?
is there an available wiring diagram for this cart?

[Jmack14]

Originally Posted by yurtle

An under load reading is more in line with what the batteries see. You gave us a pack voltage while climbing the slight hill. Assuming you have a DMM, hook it up to each battery while climbing the hill.

5 0f the 6 tested out under load going up incline 5.79-5.83
1 of 6 tested out under load going up incline 5.65-5.69

doesn't seem like much difference to me your thought?

[yurtle]

JohnnyB is more of a battery expert than me. While the batteries are more than .1 volts different, I don't think you have a dead cell, as the difference would likely be more.

Since we don't know how steep your hill is, I can't comment on whether the voltage is OK.

Charge them, then measure them all 12 hours after the charge is complete. As to checking the FNR, see the terminals are hot after a run. In fact, check all cable ends after a run, for heat. It's possible to have a weak connection, and have the heat localized at the end, and not the cable itself.

[JohnnieB]

Originally Posted by Jmack14

i understand what you mean now johnnieb

that voltage never gets above 16-18 volts between B+ and M- so i have tried my controller in a working cart as well and still performs like its suppose to in that cart, batteries keep checking out ok, cables all appear to be ok and are not getting hot due to high resistance(i assume they would if resistance was there?) anyway to test f and r switch?
is there an available wiring diagram for this cart?

Attached is a schematic for your cart with the high current circuit highlighted. The F/R is shown in F.
Also attached is a block diagram of a typical series drive controller. Not the same model as you have, but they all work about the same.

The speed control element (a dozen or so MOSFETs in parallel) are located between B- and M-, so at 0% throttle there should be battery pack voltage between them and at 100% throttle there should be Zero volts between them. (MOSFETs are not perfect conductors, so there actually will be in the neighborhood of 0.1V per 100A of current flow at 100% throttle.)

Conversely, from M- to B+, you should get 0V at 0% throttle and (almost) 100% of battery pack voltage at 100% throttle.

The battery pack current enters the F/R switch on stud A, goes through some contacts to D. The voltage from M- to A and D ought to be identical and be at battery pack voltage.

From D, the current goes through the motor's field windings (Stator) and back to stud B. Current is flowing, so the voltage now is roughly 1/2 of the pack voltage, and the voltage on C ought to be the same as what is on B.


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Sounds like you have an understanding of resistance producing heat.
All cables and connections intrinsically have resistance, so they all warm up some when high current passes through them, but we try to keep the unavoidable resistant to a minimum and use 4Ga cable with controllers up to about 500A and 2Ga for 500A and above.

If a cable gets more than about 10°F above ambient, it is bad or too small.

[JohnnieB]

Originally Posted by Jmack14

5 0f the 6 tested out under load going up incline 5.79-5.83
1 of 6 tested out under load going up incline 5.65-5.69

doesn't seem like much difference to me your thought?

In an earlier post, you said the no load voltage on the battery pack was 37.58V, so you new batteries are only about 85% charged. (SoC chart attached - What brand batteries do you have? The chart is for Trojan and clones)

The relatively minor voltage difference between batteries only mean the battery pack needs to be equalized. A bad cell is typically about a 2V difference.

Once they have been equalized (IE: 0.1V or less between batteries.) the difference at-rest and under-load ought to be close to the same.

The thing about equalization is that the pack is charged in series, so a mix of batteries with slightly higher voltages and slightly lower voltages don't all end up with the same level of charge if the charger shutoff is based on pack voltage. And the imbalance gets worse as time goes on if not corrected.