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XR400 Charging Issues

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Folks,

I have a 98 xr400 that I put a tusk lighting kit on. I wanted it to have a charging system so I replaced the stock regulator with a trail tech reg/rec and left the stock stator in the bike. It is charging a Tusk lithium ion battery and running lights and a trail tech vapor. All lights are led and the headlight is an Amazon special led H3 replacement. I don't know how much power it draws but I know it is significantly less than a H3 halogen. Everything worked great for about six months and the battery was sitting right at 13.6 volts throughout the rpm range. Headlight comes on when the bike is running and the rest of the lights are on a switch. I had been charging my phone (for gps) off the battery as well. None of the stock AC system is being used anymore, except for ignition which I didn't mess with.

The problems started about a month ago, I left the phone charging off the bike for about five minutes with the bike not running and started having issues right after. Tail, blinkers and horn didn't work with the bike off and were really dim with it running, horn wouldn't do anything at all. With the bike running, the headlight would strobe at idle then cut off with any rpm increase. With the bike off, the battery read about 8 volts if I remember correctly. I replaced the battery and all was well and working proper again, (stopped charging the phone from the bike because I figured that was the problem.) Fast forward to today, got the bike all loaded up to ride the WA BDR and do one last light check. Same problem as before. With the bike idling, battery reads 13.6 volts but increase the rpm and it drops with rev increase down to about 8 volts. I happen to have my buddies XR400 set up the same way sitting in the garage so I started robbing parts off it. I swapped the reg/rec, which was working correctly on his bike and no change on my bike, same voltage readings. I stole his battery and now it's back to working properly. I'm gonna ride it anyway and hope for the best but was hoping to get some insight from you guys as to what's causing this. 

I have a couple thoughts, first is that I killed the first battery running it too low and happened to get a bad replacement battery. Second is that I'm asking too much from the stock stator running a charging system off it and batteries are dying because of it. I will hopefully be out of cell service for five days so I'm not ignoring responses, just away from the interwebs. One more thing to note is that the ignition side of things is still working as it should and hasn't changed or had any problems throughout this. Appreciate the help in advance.

Daniel

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The stock stator output is about 80 watts.

I would go over your wiring of the reg/rec into the bikes system. Trail Tech has 2 different wiring configurations for it IIRC. Which one did you use?

So I'm guessing your buddies battery you borrowed is a TT battery too? You might try a better rated battery. Some things, you get what you pay for.

Also, Lithium batteries usually require a special Lithium charger, so I don't know how a bikes charging system gets away with charging one properly without damaging it or shortening its life.

 

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I followed the wiring setup for 12v charging. I can't remember exactly how I wired it but followed the trail tech diagram. All the batteries I have used are Tusk, I called Rocky Mtn and someone there told me I could charge it from the bike, but who knows how credible they are. My next thought was to try a better/bigger battery.

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Which Tusk battery are you using?

I'm reading that the Tusk TLPF 7L battery is a 2 Ah battery. That is tiny IMO. I ran a 3.7 Ah and IT wasn't enough.

Also, I'm reading that you should make sure your regulated voltage from the reg/rec is below 15v so as not to damage the battery. Current TT reg/rec has a provision for adjusting output voltage if required. TT claims the reg/rec requires an electrical system with a floated ground. The stock XR system is not floated if I remember correctly.

https://www.trailtech.net/media/wysiwyg/pdf/010-ELV-116.pdf

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And XRs have a very noisy electrical system because of the ignition system, the noise messes up the DC regulator. Your symptoms of falling voltage with increasing rpm is typical.  A good lead acid battery filters out the noise, a failed battery will not.  To make the DC voltage regulation work on XRs wo a battery I've had to add a capacitor, a 10kmfd, 50 volt or higher will work. If you buy off ebay don't buy Chinese.  Floating ground on the charging section of the alternator helps but I've also had problems with those.
XRs float the DC section of the alternator but most only have an AC section that is internally grounded, a wiring diagram will show.  You can float an internally grounded section by disconnecting the connection to the alternator frame and running a wire out to the rectifier. 

Wire color is a good indication of the stator wiring: A single Blue wire is usually AC for headlights, 2 Yellow or a Yellow and a Pink indicate a floated ground section. 3 yellow is 3 phase out and needs a special rectifier. Power for the ignition is usually Black w/ red.

Edited by Chuck.

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I did float the ground and the tusk battery is a 2ah. I measured power consumption and everything including headlight is using 13.5 watts. I did check regulator voltage output and it is well below 15v. I like the trail tech battery but if 3.7 ah isn't enough I'll look elsewhere. I would like to keep the battery small enough to fit on top of the air box.

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