G19 climbs well in reverse but stalls in forward

[sgwriter]

1998 Yamaha G19 with new batteries and lots of power is occasionally losing power (only a second or less at a time - feels like I tapped the brake) while driving at normal speed. I may drive a couple of miles without this happening. One time after several of these hesitations it slowly lost power completely and died. I came back to it a couple of hours later and started poking around. I toggled the Run/Tow switch and tried the accelerator again. It worked, and I drove home without a problem.

Since then it hasn't died completely, but it still hesitates occasionally at full speed and at slow speeds it doesn't want to climb - in forward - at least not consistently. It will stall out. Depending on the hill, I may be able to push with my left leg and it may start rolling fast enough to regain power. Seems to have NO problem climbing with power in reverse.

Diagnosis?

[cgtech]

Likely batteries. Get us pack voltage when the failure happens. You can carefully stick your meter probes in the charge port to get a reading while driving.

[sgwriter]

Thanks for the reply, cgtech.

Pardon my ignorance, but wouldn't it take as much battery power to climb in reverse as it would in forward?

If it is battery related -- and they are fairly new -- would the symptoms suggest a poor connection somewhere? Maybe a loose one that would make the problem intermittent? If so, where would you suspect? I've cleaned the main posts going from the batteries.

Thanks.

[cgtech]

The controller operates in "limited max power/speed" mode in reverse. This reduces the demands on the power source.

[sgwriter]

Thanks. I'm new at all of this. I'll look into getting a voltage meter and figuring out what, when, and where to test. As well as what the readings indicate . . .

[sgwriter]

One additional piece of info. The climbing problem FEELS like a torque problem, like trying to make a car start in third gear -- from a dead stop -- and go uphill. Sometimes it will find the right "gear" and climb without a problem; sometimes it won't. But it has never failed to climb in reverse.

I'm never out long enough to let the battery power indicator fall below the halfway mark. It rarely gets below 70% before recharging fully.

[cgtech]

Still need voltages. I never base anything on the readings of the "10-led bar graph meter". Those meters are only ~ ("air-quotes accurate") accurate on a perfect battery pack, not worth a thing on a worn out pack, or one with a individual failing battery.