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BATTERY
- Thread starter MAINEXSER
- Start date
I totally agree with Jim and Marty on this one. As soon as the alternator output DC voltage exceeds 12.6 volts, there is no way the battery can deliver any power to the system. After all, there is one positive and one negative lead to it, and the current cannot flow in two directions simultaneously. A lead-acid battery has a fully charged voltage of 12.6 V. If the system voltage is more than 12.6 V, the battery is either receiving charge, or just sitting there fully charged.
Any battery large enough to reliably get the engine running, could be considered large enough. Then electric start, parking lights etc. can increase the required capacity.
One way to visualize it is two parallel batteries. One will always be some amount higher than the other if measured independently. With the two in parallel that one will be trying to charge the other -- but two batteries in parallel give more current, which proves both are discharging, not just one. Replace one of the batteries with a power supply and nothing has changed electrically. The power supply hasn't removed the battery from the circuit somehow. A charging circuit is a power supply connected in parallel to a battery.
The generator works to keep the battery charged, so the original question is what characteristics of the battery demand what from generator? Does a little battery or a broken battery or etc. make it work more, like a parallel resistor would? One way to get some insight into that question is to do a Thevenin analysis of the circuit, which is something for young, energetic people. Speaking of energy...
No, it doesn't "prove both are discharging." Jeeze... you really need to go back and reread basic electrical theory. One energy source has a higher potential (alt) than the other (batt). The one with the higher energy potential (14v) will send energy to the lower potential (12v). One gives, the other gets. The alt charges the battery. The battery is charging... lesse... how many ways can I put this..... the battery gets fuller, not emptier. As long as the alternator has the higher energy potential, the battery ain't givin' up jack shit.
The OP asked a question so he could better understand what battery he could use. Quit messin' up his mind with absolute bullshit.
You want to make this a discussion, start one in the Garage where we can laugh at you there without affecting @MAINEXSER 's understanding of basic electricity.
... or just let it go for pete's sake.
This is about a generator and mechanical regulator but it covers the theory in simple terms.
Yeah.... simple would be good.
Two batteries, each with current capacity of 1. In parallel you have a current capacity of 2. If both aren't discharging, then where does the extra current magically come from. This reminds me of discussions I had in the workplace and they eventually send the other guy to go count parts in bins. I don't know why I attract them but I do. Always been a mystery to me.
Fer fucks sake... one last try (promise 
)
They ain't fuckin' balanced!!!
One has a higher potential than the other. The one with the higher potential will always supply the other.
) They ain't fuckin' balanced!!!
One has a higher potential than the other. The one with the higher potential will always supply the other.
^Yes, one will always charge the other. But that one can't supply current beyond the current it can supply. The current beyond what that battery can supply, which you can measure, is coming from the battery you think is just along for the ride. It's extremely counter-intuitive to some apparently
Glad you could clear that up for us.
A little early in the day ain't it?
I'm done. See ya.
WRONG! The battery needs to "receive back" whatever amount of energy that was drained from it during the startup process. This is totally independent of the size of the battery. You could even argue that a larger battery would have self-discharged MORE energy during a long period of not riding the bike than a smaller battery would. So would in fact be a larger burden on the alternator.
Guys, obviously I made a boo boo on this one... The other day I was visualizing it my head and doing something like a nodal analysis and saw the two "voltage sources" paralleled and went on. But this isn't a valid way to connect two voltage sources of different voltages. An exception is some batteries can be paralleled this way because of their chemistry. In the case of a power supply in parallel with a lead-acid battery, the battery won't be a contributor as long as the voltage there is above the voltage of the battery if it was out of the circuit (open circuit voltage). The re-think was triggered by a superior being reminding that current can't flow into and out of the battery at the same time...and of course the battery has a lower voltage. There is a question of battery characteristics needed to remove the ripple from the generator output.
There's no need to explain it to us.... we already knew that.
Another 2 pages of bickering...........Funny when it was happening to me, was to blame. One common denominator in this.
Caught'ya!
A possible problem with a small battery and the stock electronic ignition is that the TCI demands at least 12 volts to do it's job, With a tiny battery it won't take long on a bike that hasn't fired yet for the ignition and rotor loads to lower the battery voltage and sparks will quit happening.
Prolly ANY lead acid battery is enough to act as an electrical shock absorber, dampening voltage spikes in a dirty electrical environment helping to protect fairly delicate electronics.
Since the OP's question points to the bike design. A few more points, The factory bolted the TCI to the massive rubber mounted battery box, for good reason; to isolate the old school circuit board from engine vibration,it's also located away from heat sources.
Remove the TCI from the bike before any arc type welding, eddy currants can grenade the electronics.
Most "simplified wiring diagrams" ignore ground wiring. Providing copper wire ground connections between battery negative, frame, engine, triple trees, and handle bar is not optional on a bike you expect to operate reliably.
sleddog83
XS650 Addict
Well now that that is all sorted. The TCI module by itself has very minimal electrical requirements. Most of the circuitry runs on 8.2 volt regulator. I have tested my boards reliably down to 11 volts on the bench. I did measure the current draw one time. I believe it was around 100 -200 mA. The module circuitry could probably run on a lesser voltage, but the power hungry component is the ignition coil not the tci module. You will stop getting a good spark out of the ignition coil at 11v. For starting a TCI equipped bike, my best guess, would be that if you are not using the starter, and the bike is in good running condition, with a minimal static load, you should be able to start it with a smaller battery. Best to also wire in a headlamp power switch though. You may also want to do some tests, looking for a strong spark.
