Shunt mod for XB-700Li

I was planning on relocatin the 10amp fuse Xtreme told me was in the controller. I didn't find any fuse inside the controllor. Crap what a bunch of wasted effort.
Not wanting to have wasted teh time I thought....hmmmm shunt mod time!
Here are a few pics of what DIDN'T work. Works fine without load but with a load the system kills power presumably becasue of over current.

Some notes for you though.....
there are 12 mosfets inside. 4 for each phase - nice.
The caps are rated at 63V -- marginal if someone upgrades with extra battery.
There is a thermistor -- not sure if to protect from heat or maybe in my case over current.

Here is a look. If you look closely between the 4th nad 5th caps you will see 2 shunts.

Here is a look at the bottom:

I didn't have 16 gauge steel and didn't sacrifice a hanger -- maybe a should have. I put in a 2 1/2" 12 gauge house wire. I mounted on the back and slipped a small piece of csrdboard between the wire and the new shunt.

After putting back together and doing basic heat / smoke test with the back wheel raised I felt I was ready for a test spin.
I got about 40 feet when system totally shut down. after waiting a few minutes I could repower the system. Bottom line I tried several times and ended up taking the shunt out so I could keep scooting.
Guess I need to get a little more precise. Make a few measurements then get a calculator out.

Anyone have ideas on what appears to be a thermister in the pic above? I'm wonderign if that might be part of the current limiter......

Have a good one. Happy scoot.
Thom

I guess you didn't fry the controller, it just doesn't work with the shunt (a short really) in place. It sounds like there may be a thermal shut down to protect the FETs (which is a good thing). Perhaps you could consider ordering an XB600 controller, and shunt mod it, since it appears to be able to handle more current (lots of us have installed the shunt mod in the XB600 controller).

Just an idea. I am glad you didn't fry your controller. Slower is better than nothing.

Tom

The shunt mod you did would have allowed your controller to furnish unlimited power to your bike.... not good when using lithium batteries. My guess is that the XB-700Li controller has some sort of limiter which also protects the battery pack against a short cirtuit. Without some kind of protection like this, you would run the risk of an explosion in your battery pack.
If you want to try to increase your power with a shunt mod, I would suggest that you use a piece of a miniature paper clip (the kind that are about 1 1/4 inch long). The wire used for these paper clips is approximately 19 gage. Straighten out the paper clip and cut off a piece about 1.6 inches long. Insulate 1.2 inches of it with teflon shrink tubing, and solder the bare ends across the bottom of your board between the two ends of the shunt. This piece of wire will have about 0.005 ohms resistance, which will allow your current limiter to work. The 1 inch or so of copper wire you used would have had virtually no resistance, thereby making your current limiter inoperative. Take a look at my website at:
http://bergerweb.net/xb500/technical.shtml#resistance
Here you will find some information about choosing the proper length of steel or copper wire to do your shunt mod.

Richardb, Do you really believe that the shunt mod can be done to this controller? What about increasing top speed? Different motor(1500 watt)and controller? I am open to suggestions. thanks,Randel Hanford Ca.

Well? pleeeeeeeease! Randel Hanford Ca.

Well, I figure somebody has to do it, so I am looking to purchase another controler to mod so I'm not dead in the water, I'm not sure sure when I can do it, will try to keep you posted,stil trying to figure out this supposedly 56 voltage lighting system? ecrasyman doesn't have a controller to supply 12 volt lighting. Can someone throw me another bone? Dogman?Reikeman? Someone? Grandpa? Thanks! Randel Hanford California

Randel,

The best way I know how to do this is with a DC to DC Converter. Here is a place to start. There are several converters here to choose from, if I had some information I could narrow the answer to a few modules which would do the job. Just remember if you want to add any other options, cellphone charger plug, MP3 player, or what ever, you will need to be sure the DC to DC Converter can handle the extra load. There are other places to purchase these devices I have given this link so you can see a variety of modules.

Grandpa Chas S.

There is a guy who has a 72V to 12V 9Amp DC-DC converter that is real nice. I installed one in my 72V system and havent had any problems at all. He can be reached at outolunchcruisin [at] gmail.com.

I would totally try your advice about shunt modding the xb700li but what if the same thing happened to my scooter as what happened to the first guy? Could you get a higher amperage controller and still use it with this scooter?

I wish my xb700li was faster maybe I'd enjoy it, just having these lithium batteries makes it kind of dangerous to mod out!

I'm still considering the 700Li, because my XB-600 is long in the tooth and getting old. However, if the speed difference isn't much and there's less ability to customize (i.e., shunt, convert, et.) I might stick with my old horse a little longer. Until the 700Li is cracked wide open. I do like the battery system, though. My SLA batteries are pretty damn heavy and won't do the same distance.

What kind of power would I want to take from the battery to be safe? They say the xb600 takes 700 watts from the batteries at a time? would that mean the xb700li uses 800w? How will I know what kind of shunt to use according to the table on http://bergerweb.net/xb500/technical.shtml#resistance ?

I'm assuming if I was to make a shunt that let in a little more power then the original one it would allow it to get more power from the batteries faster, but if it takes too much from the battery too fast, the battery can explode?

So I think what I'm going to do next time I open up my xb700li is to add a little bit of solder to a leg of the shunt to increase the resistance and to add a little more power to my scooter, but not too much as to make my batteries explode by drawing unlimited current with a traditional xb600 style shunt... Does this sound safe?