Re: (ET) Aaargghh!!!!

This begs the question then - why did I get sparking when closing the main power disconnect if the charger is permanently connected? That can't be right. Let me check the service manual....

it shows the ground side of the charger being permanently connected to the negative side of the battery (through CB-1), but the positive side is connected through the main power disconnect switch.

I figured it had to be that way. Many years ago I once accidentally "charged" the tractor without realizing the main disconnect switch was open, and a day or two later when I was ready to mow I discovered the battery pack was uncharged. Then I noticed the open disconnect.

From: jlantonucci comcast net <jlantonucci comcast net>
Sent: Thursday, May 25, 2017 6:20 PM
To: lists freerangeelectric com; elec-trak cosmos phy tufts edu
Subject: Re: (ET) Aaargghh!!!!

The charger is hard wired to the battery pack like Jim said. Turning off the power disconnect does not disconnect it - you have to disconect the wire at the rear batteries. I've had a fireworks show more than once...

------ Original message------

From: Jim Coate

Date: Thu, May 25, 2017 4:56 PM

To: elec-trak cosmos phy tufts edu;

Subject:Re: (ET) Aaargghh!!!!

The capacitor and diodes in the charger are the common failure points. A fairly easy replacement. Unless actually possessed, by mice in the case of Elec-Traks. I've seen chargers where the mice chewed off all the insulation of the wires and interesting things then happen. Several feet of heat-shrink tubing and a hot-air gun to the rescue and new parts as needed.

NOTE: the wiring harness (9-pin plastic body with 5 pins actually used) only disconnects wall power between the timer and the input to the transformer. To disconnect the charger from the battery pack, you need to remove the stair-step black metal piece with the timer assembly that covers the band resistors ("toaster") behind the headlights. Then reach way down and unscrew two nuts (think socket extension) and remove the two wires that drop down under the frame. Be sure to insulate the ends of those wires if the batteries are still installed.

http://electrictractorstore.com/index.php?main_page=product_info&products_id=172
http://electrictractorstore.com/index.php?main_page=product_info&products_id=61
http://electrictractorstore.com/index.php?main_page=product_info&products_id=62

On 5/24/17 8:29 PM, Briggs, Michael wrote:

I think my E15 knows I've replaced it with a robotic lawnmower and am planning on selling it. It's trying to sabotage itself.

Let me explain.

When I got home, I used the better multimeter I brought home from work to measure the voltage of the batteries. The pack read 37.5 volts (3 days after it was last charged). A bit lower than ideal, so I figured I'd charge it for a while this evening and measure again in the morning.

I turned on the power strip I keep the charger plugged into, and noticed the charger sounded "different". After a couple of seconds, the breaker on the power strip tripped and the charger shut off. That seemed odd, so I decided to check things out. While doing so, I noticed that I had left the tractor's main power disconnect turned off (I think I turned it off yesterday or the day before when cleaning up the connections on card 1). So I said to myself "self, you should probably go ahead and turn that back on" - without thinking it through (after all, something had just tripped a breaker on the power strip powering the charger).

As soon as I turn the main power disconnect back on, there was a "ffffftttt!" sound and a little spark from the charger area, and the release of some magic smoke. I immediately shut it back off, and said to myself "&*#%!!!!!!!".

I haven't had time to do any diagnostics yet, since I had to start making dinner. I disconnected the charger from the tractor (unplugged its harness), and turned the main disconnect back on, and everything there seems fine - but obviously something is amiss with the charger. I didn't do any fiddling with it. What's weird is that having the charger ON didn't make any sparking or release any magic smoke - it just sounded different (almost like something was rattling), and tripped a breaker.

The magic smoke was released (from the charger) when the charger was *off*. It's been over 10 years since I did anything with the charger, so I can't remember how it's all wired up. The behavior seems consistent with some kind of short in the charger - but why would that matter when the charger is off? Hmmm.... the harness must have the + and - ends of the battery in two of the connections (so the charger can charge the battery) - I'm guessing those must have shorted together. I'll check for continuity between those tomorrow.

Anyway - this thing seems to be trying hard to keep me from selling it....

In case the charger is fried - does anyone sell rebuilt ones?

Thanks,

Mike

Michael S. Briggs, PhD

UNH Physics Department

(603) 862-2828
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