Mini battery or batteryless

[Guest]

Gentlemen, your advice if you please.I'm currently restoring a gs850 that I rescued from the scrappies. I'm turning it into a cafe racer and want to clean up the mid section where the battery resides. I have two options:1, mini battery tucked in the tail. Does anyone have any experience in such things? The bike starts well on the kickstart so I'm happy to reduce the wiring loom substantially and just have the battery run lights etc. if I go down this route and get a smaller, less powerful battery will it get cooked by the charging system. Any suggestions on what batteries would be suitable.2. Battery less. I have no experience in this system but like the idea. I'm happy to build a new loom to keep it totally simple. But would like your honest opinions on pros and cons. Bear in mind this bike is not a daily ride. I live in the south of France where it's warm and dry and will be riding it for joy only. Maybe even a show or two if I'm happy with the results.Thanks for your help in advance.Martin

[Steve]

Evidently you have a '79 model. (The only year with a kick-start.)

A battery is necessary for proper running, the voltage regulator needs a reference point. For your purpose, a sealed battery would be somewhat mandatory. An AGM battery (that is a construction type, not a brand) would work well. They have better-than-average power for their size, so you could use a smaller battery, especially if you limit use of the electric starter.

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[greenie]

Thanks Steve, a really useful starting point.

[Brendan W]

The regulator rectifiier unit may be the original shunt type. I would consider replacing it with a modern series type to reduce the level of cooking going on.
Well worth searching the material here on that topic and rewiring of the charging system. Transformed my bike and even cured 'carburettor' problems

[greenie]

If I buy an AGM battery smaller in size do I need to worry about the chsrging system cooking it. What's the minimum amp hours I should go for? Will it affect any other system on the bike?

[Brendan W]

If I buy an AGM battery smaller in size do I need to worry about the chsrging system cooking it. What's the minimum amp hours I should go for? Will it affect any other system on the bike?

The shunt regulated system runs flat out all the time and dumps the excess into the stator coils cooking the oil. Having headlights on all the time helps but it's far from ideal. A small battery and no electric start will make this worse. A series regulated system is smart enough to 'switch off' the generator when the battery says enough.
In theory it shouldn't matter how small the battery. If you are not going to use the electric start, disconnect it. I can't imagine a small battery being happy if accidentally asked to put out a lot of current - I would expect the voltage to drop to there not being enough left to make a decent spark. I could only guess that 5 Ah would be enough to supply the few Amps needed for the ignition system when kickstarting. I'm sure some of the Cafe guys will know better from personal experience.

[JTGS850GL]

Evidently you have a '79 model. (The only year with a kick-start.)

A battery is necessary for proper running, the voltage regulator needs a reference point.

Actually the battery is needed in order to suppress noise spikes. The regulator doesn't need any external voltage reference. It basically sees the battery as a large capacitor and noise filter. Without some capacitance in the system the output from the R/R is very noisy and could cause damage to the electronics. Namely the igniter on your model. There are self regulated Lithium Ion batteries that are much higher density and smaller packaged that would work fine you your application. Just make sure that the charge characteristics are compatible with a lead acid battery. Shorai and Skyrich are companies that sells them. There are several and others can chime in.

[posplayr]

Actually the battery is needed in order to suppress noise spikes. The regulator doesn't need any external voltage reference. It basically sees the battery as a large capacitor and noise filter. Without some capacitance in the system the output from the R/R is very noisy and could cause damage to the electronics. Namely the igniter on your model. There are self regulated Lithium Ion batteries that are much higher density and smaller packaged that would work fine you your application. Just make sure that the charge characteristics are compatible with a lead acid battery. Shorai and Skyrich are companies that sells them. There are several and others can chime in.

++ on that

[greenie]

Brilliant info thanks very much.
if I therefore replace the rectifier for a series version I can use a smaller battery without the starter motor?
am I getting this right?
i could in theory loose the whole starter wiring. I know this sounds mad but I'd like it to be as clean as possible so any excess wiring I can loose would be a benefit.

[JTGS850GL]

Yes you can use the series R/R in place of the stock unit and it will help your stator live longer, but series v/s shunt has little bearing on the size of the battery used. It's current draw not capacity that determines how much current is being shunted. Once fully charged a battery draws very little current in order to maintain it. Accessories, ignition and lighting have a much higher impact.

If you were going the minimalist approach then I would lean toward a series R/R (SH775) only because you wont have as much current draw on things like running and indicator lights. The series unit will do a better job at lower current loads.

In reality the headlight and ignition system are the largest current draws in the system (minus the starter motor of course) and if you plan on not deleting either of those then the impact would be minimal. You could go with what you have now, assuming that the charging system is still in good working order, but I like the added longevity of using the SH775.

[greenie]

Brilliant JTgs850, thanks so much for the reply. I'll look into an sh775 and probably build a new
loom.

[posplayr]

In reality the headlight and ignition system are the largest current draws in the system (minus the starter motor of course) and if you plan on not deleting either of those then the impact would be minimal. You could go with what you have now, assuming that the charging system is still in good working order, but I like the added longevity of using the SH775.

I have measured the standard circuit loads nominally as follows:

Highest load is SIGNAL. With tail light, brakes and blinker current varies between 5 to 9 amps(peak when blinker is on; 5 amps the rest of the time)
Middle load is HEADLAMP is 5 amps constant
Lowest is IGNITION the average is about 3 amps.

By switching all of your SIGNAL lamps to LED you drop your load down to about (IIRC) 1/8 of the incandescent bulb currents or 5/8 amp to 9/8 amps (respectively for LEDs).

You can get LED bulbs for most of the signals pretty inexpensively (I got mine on AMAZON). After some experimentation I swapped out all of mine on my ED.
The SERIES R/R prevents additional stator load as would happen with the SHUNT type R/R. This also reduces the total current running through my SSPB. (or your fuse box)

[greenie]

More great info thanks.
ill start building the loom and let you know how it goes. Not that there will be much there at this rate.

[posplayr]

More great info thanks.
ill start building the loom and let you know how it goes. Not that there will be much there at this rate.

If you search under my handle you will find a minimum schematic ; look for "550 bobber"

[JTGS850GL]

I have measured the standard circuit loads nominally as follows:

Highest load is SIGNAL. With tail light, brakes and blinker current varies between 5 to 9 amps(peak when blinker is on; 5 amps the rest of the time)
Middle load is HEADLAMP is 5 amps constant
Lowest is IGNITION the average is about 3 amps.

By switching all of your SIGNAL lamps to LED you drop your load down to about (IIRC) 1/8 of the incandescent bulb currents or 5/8 amp to 9/8 amps (respectively for LEDs).

You can get LED bulbs for most of the signals pretty inexpensively (I got mine on AMAZON). After some experimentation I swapped out all of mine on my ED.
The SERIES R/R prevents additional stator load as would happen with the SHUNT type R/R. This also reduces the total current running through my SSPB. (or your fuse box)

Good information. Assumed that the headlamp would draw more then the signal lights. Depends on wattage used though. I tend to go on the bright side with a 100/80 watt H4. Please don't tell the DOT. Agreed that the need for a series R/R goes up as current demand goes down.