FJRiders.com

Since I have the bike all apart and recently had a Battery failure on a trip. What should the voltage at the Battery be When running the bike at a decent engine speed? Thanks.
Tim

Without getting all scientific...... I have a digital voltmeter connected to my fusebox, and anything above 2500 rpm should pretty much be fully charging at 14, 14.1 (14.2 if you're lucky). Officially, the service manual says the charging voltage should be 14V @ 5000 rpm, but in reality it will develop full charging voltage way before that.

You really need to know that the battery is properly charged first. If you can, ideally you would trickle charge the replacement battery over night. Ideally battery voltage should be checked at 70º F, the resting voltage can be lower with lower air temp.

A few minutes after starting, with no electrical load other than the normal motorcycle electrical system or very minor extra loads like a GPS or MP3 player -- at idle speed you should measure >14.0 volts, 14.4 would be ideal.

If you are concerned about your voltage regulator you should really make the readings right at the voltage regulator. On the Gen II it is on the back of the engine, under a heat shield. First, with the engine running at idle, with the gray connector disconnected you should read 14.4 - 14.6 volts directly across the exposed R/R terminals. With the gray connector plugged in, back probe the connector with the engine at idle and no extra loads on the electrical system, read 14.2 - 14.5 volts.

<extra notes>

A Datel may not show true battery voltage, nor may some DMM show true battery voltage. The voltage you read can, and probably will be different with different brands of DMM. All motorcycle engines cause electrical 'noise' which is a small AC signal riding on top of the battery's 12 volts. This noise confuses a DMM and causes flickering or erroneous readings. If you readings are off by 0.1 to 0.2 at the battery, with the engine running don't sweat it. Checking directly off of the R/R eliminates this possible source of reading error.

On more than one occasion I have had Forum people call and ask me to help them with troubleshooting but first I had them do a quick check of their DMM and we found that the DMM battery was nearly dead and causing bad readings.

I think the bike's OEM AGM battery needs about 14.7 volts for a proper charge.
Splitting hairs between 14.1 and 14.7 volts.

Could just be a crook battery or a cheaper non OEM spec one.
Remember that the bike needs a good CCA rated battery.

If your getting above 14.1V, not a problem with the charging circuit.

Some battery manufactures tend to be over zealous with their CCA claims.

Hahahaha I have a Keithley 2100 6-1/2 digit voltmeter that went through cal recently. I am reading never more than 13.8 and if I add any load it drops to 13.2.(like my extra driving lights. or my heated Jacket) not both. this is at the battery. Thanks for the info.

Wellalrightynow. You need to perform a stator check. With the black connector removed from the R/R, meter set to AC volts and a range selected to read up to 75 volts you are ready to test. At idle measure any three pins to any three pins. The absolute voltage isn't really so important as the voltage readings should be within 1-2 volts of each other. At 5k rpm you should be reading >50 volts (could be closer to 70 volts) and again the criteria should be each reading within 2-3 volts of the others. Typically, if the problem is a bad stator the reading will be either very close and good or one reading will be wildly wrong. If all readings are nearly the same shut off the engine and ohm from each stator terminal to ground on at least a 10 meg scale. All readings should be nearly infinite. I'm time pressed right now but can supply better information later.

cool thanks. this is the info I need. I can handle checking. I have megohm meter also if I need to really check the thing....

Awesome, Tim, when you get yours sorted out come over to the house and help me with the TDM

clocklaw wrote:Awesome, Tim, when you get yours sorted out come over to the house and help me with the TDM

I really need to move... We used to be neighbors?

Name Etc. wrote:

clocklaw wrote:Awesome, Tim, when you get yours sorted out come over to the house and help me with the TDM

I really need to move... We used to be neighbors?

I remember you telling me that....in other words it is time for you to come home!

Over on that other forum....dcarver has a great thread about his charging system troubles. The condensed version is: The RR wiring is barely adequate.

After I added a volt meter I was disappointed to only see 13.8 on a good day. This was before adding heated gear or lights.
Anyway, Jack over at Roadstercycle (http://www.roadstercycle.com/" onclick="window.open(this.href);return false;) offers an upgraded RR harness for our bikes. The price is fair, delivery is fast and Jack was a pleasure to deal with.
It got mine up to 14.2 (sometimes 14.3). As an added bonus, the leftover wiring is perfect to power a fuzeblock under the seat.

That's very interesting....I'm going to send him an e-mail to talk about my TDM. Thanks Chuck!

clocklaw wrote:That's very interesting....I'm going to send him an e-mail to talk about my TDM. Thanks Chuck!

true story. If it is just wire problem. . . I am running a bigger wire from the Battery to my accessory Fuse Block than the R&R has going to the bike. I May just tie them together. I used a very fine 10 gauge Aircraft grade wire. It will handle it. but I am going to check that all is ok before wasting my time.
If I can locate the right connector I will build my own. all the wiring looks small on this bike and I think was also the cause of the spider meltdowns on the Gen2?

The OEM wire gauge is sufficient (with almost no head-room left) for the capability of the electrical distribution system. Where you start loosing tens of millivolts here and there is through the wire to connector pin connections, pin to pin connections and passing through fuses and switches. I have gone through a couple of FJR electrical systems using a voltage drop investigation and found the biggest problem isn't voltage being lost from one end of a wire to the other end, it has been lost at junctions and through the main fuse. When an electrical system is providing 40-50 amps even tiny resistances begin to cause significant voltage drops. When the electrical system is drawing 40 amps just 0.01 ohms can cause a 0.4 volt drop. Do not loose sight that the voltage drops happen in both the positive and negative circuits and add together in the series circuit between the battery and ground.

If the output of the regulator is 14.4 volts when the gray connector is connected but the voltage at the battery is <14.0 volts then you may want to pursue the harness. Another event that occurs with resistance is an increase in electrical system noise. I would *love* to look at an electrical system with a big voltage drop between the R/R and the battery with an oscilloscope and see what the true voltage is. The condition of the battery will also play a role in how much electrical noise is present.

ionbeam wrote:The OEM wire gauge is sufficient (with almost no head-room left) for the capability of the electrical distribution system. Where you start loosing tens of millivolts here and there is through the wire to connector pin connections, pin to pin connections and passing through fuses and switches. I have gone through a couple of FJR electrical systems using a voltage drop investigation and found the biggest problem isn't voltage being lost from one end of a wire to the other end, it has been lost at junctions and through the main fuse. When an electrical system is providing 40-50 amps even tiny resistances begin to cause significant voltage drops. Do not loose sight that the voltage drops happen in both the positive and negative circuits and add together in the series circuit between the battery and ground.

If the output of the regulator is 14.4 volts when the gray connector is connected but the voltage at the battery is <14.0 volts then you may want to pursue the harness. Another event that occurs with resistance is an increase in electrical system noise. I would *love* to look at an electrical system with a big voltage drop between the R/R and the battery with an oscilloscope and see what the true voltage is. The condition of the battery will also play a role in how much electrical noise is present.

Want me to take home the scope and do some screen shots for you? my fluke Scopemeter has the capability to do that. Unless I just decide its ok and just want to go ride the damn thing. I still haven't gotten all my parts for the stupid vacuum leak... half of them came today.

Name Etc. wrote:Want me to take home the scope and do some screen shots for you? my fluke Scopemeter has the capability to do that. Unless I just decide its ok and just want to go ride the damn thing. I still haven't gotten all my parts for the stupid vacuum leak... half of them came today.

It may be interesting to take a look at your electrical system if there is a big voltage drop between the R/R and the battery. When I looked at my electrical system with my old 'n shitty 'scope AC coupled, this is what I found floating on top of the 14.x volts:



IIRC, the scope was set for 100 mV/cm. Unlike today's 'scopes where we take digital screen shots, this was the best I could do with my antique. I recommend to run the 'scope off of internal battery or isolate the scope from earth ground and connect the scope probe ground directly to the battery neg. terminal to get a true picture of the noise.

ionbeam wrote:You really need to know that the battery is properly charged first. If you can, ideally you would trickle charge the replacement battery over night. Ideally battery voltage should be checked at 70º F, the resting voltage can be lower with lower air temp.

A few minutes after starting, with no electrical load other than the normal motorcycle electrical system or very minor extra loads like a GPS or MP3 player -- at idle speed you should measure >14.0 volts, 14.4 would be ideal.

If you are concerned about your voltage regulator you should really make the readings right at the voltage regulator. On the Gen II it is on the back of the engine, under a heat shield. First, with the engine running at idle, with the gray connector disconnected you should read 14.4 - 14.6 volts directly across the exposed R/R terminals. With the gray connector plugged in, back probe the connector with the engine at idle and no extra loads on the electrical system, read 14.2 - 14.5 volts.

<extra notes>

A Datel may not show true battery voltage, nor may some DMM show true battery voltage. The voltage you read can, and probably will be different with different brands of DMM. All motorcycle engines cause electrical 'noise' which is a small AC signal riding on top of the battery's 12 volts. This noise confuses a DMM and causes flickering or erroneous readings. If you readings are off by 0.1 to 0.2 at the battery, with the engine running don't sweat it. Checking directly off of the R/R eliminates this possible source of reading error.

On more than one occasion I have had Forum people call and ask me to help them with troubleshooting but first I had them do a quick check of their DMM and we found that the DMM battery was nearly dead and causing bad readings.

Ok, I checked regulator with no extras engine idle connector off. 15.3 volts. Plugged it in and checked at the connector back side 13.5

clocklaw wrote:Awesome, Tim, when you get yours sorted out come over to the house and help me with the TDM

mine too please

Ok so where does the battery go to ground frame/motor. I wanna check that. I got 14.4 back side of regulator connector. The first time I used a ground on frame. I'm pretty sure there is resistance between frame Battery and grounds.

Name Etc. wrote:Ok so where does the battery go to ground frame/motor. I wanna check that. I got 14.4 back side of regulator connector. The first time I used a ground on frame. I'm pretty sure there is resistance between frame Battery and grounds.

Edit: The Gen II anatomy is different enough that I no longer have confidence that all of the following is true anymore.

The 14 ga black R/R wire goes to a stud on the starter relay where it joins with the heavy gauge black battery wire. The starter relay is at the rider's end of the battery. There is also an engine ground wire at the front, lower right corner of the engine behind the exhaust headers. Using a couple of long socket wrench extensions and either a wobble socket or a universal it is just possible to access the connection without having to remove anything.