DISCLAIMER....
I am not a battery or electronics expert..... the following is just my guess
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Wet cell batteries (the ones that you have to add water as the electrolyte gets low) have an advantage over a gel cell or maintenance free batteries..... they make their own 'capacity'. (I would have said voltage or current, but I'm sure there would be some popcicle out there that would want to argue the point.)
The lead and acid generate their own capacity all by themselves.

Gel cell batteries want a charging voltage equal to or greater than their own. That is why they don't get charged in the old enduros. The charging voltage delivered from some of the stators is around 2v (and xx amps).

I believe modern chargers use constant current charging.... the old enduros have nothing to regulate the charging current or voltage.

So when you put in a sealed gel cell in an old enduro, you will have to keep it on an external battery charger. If the normal charging voltage is LESS THAN the battery voltage, it won't keep it charged.

You could possibly use the lighting wires to charge it and maybe even convert to an all battery backed up bike.





Or you could buy one of those electronic devices that will convert your whole bike to 12v AND eliminate your battery. It also provides more HP output and traction on wet roads. They also claim to make you more attractive, but I don't know if that can be documented...

Thanks DEET.
A 12v electronic ignition system is on order from Rex's Speed Shop. I have had good experience of his products.
Increased attractiveness in my case is impossible I assure you...

Not sure if its possible or probably isn't if battery is mounted parallel to the bike rather than crossways--but--could it be fitted so the breather fitting is uphill when on the sidestand. Is the battery filled to the top rather than the high mark when on the level. I'm probably wrong but i would've thought if the regulator was hooked to the yellow [that's the single wire ac regulator not rectifier] then it would limit everything coming off the lighting/charging coils as they're all interconnected & yellow wire rules as highest output therefore they're all limited to the regulator whatever its limit--say 7.5volts no matter how hard you rev it with lights on or off. If hooked to the blue it'll only help with lights on. Food for thought & put me right if i'm wrong.

Yes its mounted "fore and aft" so no joy there. As it happens its a case of "they all do that sir"
12v conversion on order. This will also have the benefit of having ignition advance, something the points system does not have.
I will start a seperate post on install it. Or even update my blog and link to that...
www.rexs-speedshop.com/product/dt250-twi...th-12-volt-lighting/

So any electrical engineers out there please excuse my oversimplification.

I have played around with batteries and battery charging for many years. There is one hard, fast rule: The charging voltage must exceed the battery voltage for any current (amps) to flow into the battery. This is not some "theory". It is something I have measured and observed using voltmeters, ammeters, and various battery charging sources (including a variable voltage charger that delivers constant current to a battery)

Voltage is similar to pressure. Amps are similar to a measurement of flow.

Using a tire as a analogy... If a tire has 10 psi in it and you want to put in more air, your air source used to fill the tire will need to exceed 10 psi. If your air source has 11 psi, the tire will fill very slowly... even if your air tank is 2000 gallons and you are using a 2 inch diameter fill hose... the flow of air from the tank to the tire will still be very slow if the difference in pressure is only 1 psi.

As the pressure in the tire increases and gets closer to the pressure in the fill hose, the flow of air slows more and more. And when the tire pressure gets up to the 11 psi in the fill hose and tank? The flow of air into the tire will stop. It does not matter how much air volume is still in the tank, if the pressure is not higher than what is in the tire, none of that air will flow into to tire.

Now say your tank is 2000 gallons and has 2000 psi and you have a huge fill hose and tire valve and hook it to a tire that has working pressure of 30 psi and a maximum pressure of 100 psi... the flow of air into the tire will be very fast and in a split second the tire will overfill and explode.

That's exactly how battery charging works. The charging voltage (pressure) must be higher than the battery voltage for any current to flow into the battery. The higher the voltage, the more current flow (amps) will go into the battery and the faster it will charge... up to the current limit of the charger and wiring.

As the battery charges, the battery voltage goes up. If the battery charger is a "constant voltage" type, then as the voltage ("pressure") in the battery increases, the current flow (amps) into the battery decreases. When the voltage in the battery equals the voltage coming out of the charger, charging stops, just like how a tire would stop filling when the pressure in the fill hose equals the pressure in the tire.

If you have a battery charger capable of putting out 2000 amps set with the output voltage set exactly at 6 volts hooked to a battery that measures exactly 6 volts, none of those 2000 available amps will flow into the battery. Raise the charging voltage, and the current will start to flow... raise the charging voltage to 2000 volts with 2000 amps available current through some very large wires, and the little 6 volt battery will explode in a split second... just like the tire did.

Hope that makes sense.

Ck to see if someone has hooked up the WHITE wire from mag harness. GREEN is normal charge wire, white is used only if battery is in a low state of charge IE short lo rpm rides. The white uses the entire length of charge coil hence increased output.

Wow thats what I call a comprehensive reply, thanks!

I dont think the white wire option is possible on the 250B. Here is the wiring diagram of the circuits from the Yamaha workshop manual, mine is wired the same. Standard loom no changes. There is a white wire but its in use as standard as far as the rectifier then its red to the battery.

I think that I'm right in saying that it was the earlier bikes up to about 1973 that had the white wire for extra charging capacity. Certainly my 1974 DT360A doesn't have it.

Your right, later DT's do not (as per schematic) have the white higher rate wire.