Mechanical voltage regulator adjustment?

[bluedragon]

I've just fitted a new mechanical voltage regulator (YES...they are still made!!) to my Dynastart. Although the Dynastart was completely reconditioned a few months ago by LSUK, they couldn't do much to overhaul the old Bosch regulator. They did however find a alternative Dynastart regulator in a catalogue and ordered this for me. The difference is amazing (in fact too amazing)...the Dynastart now wants to pump nearly 16V at 15A even into nearly fully charged batteries! Something is not right here...in fact I'm wondering if the 14V / 17A spec on the regulator means it's for 14V systems (are there such things??). Anyway, today, in the best tradition of messing with things I took the cover off and played with the adjustment screw on the regulator coil. Quarter of a turn clockwise has dropped the voltage and current to much more sensible levels. So, my question is - how does one choose the correct set voltage and under what conditions. My inclination would be to set the voltage to give a few amps to a fully charged battery at normal cruising engine speed, and ensure that this voltage is somewhere around 14.5V (certainly not above 15V). Does anyone have a more precise method I could use?

My batteries are a) Car battery - 65AH standard type for diesel cars from Halfords used for cranking and glowplug only b) deep cycle / start combination battery sold for boats as the service battery (75AH). These are linked via a voltage sensitive relay set at 13.6V at present. Both batteries are less than one year old and appear still in good condition.

 

[William_H]

I reckon you have pretty well got it right. it might depend a bit on how much motoring you do. If you do a lot then a lower voltage would be better but if only short runs then higher voltage is better. i would consider 13.8 as low and 14.6 as high. The higher voltage will see faster charge but al;so pssibly electrolyte loss due to boiling. A lower voltage will see less charge and less electrolyte loss. The 2 or 3 amps whne fully charged into 2 batteries sounds good to me. regards olewill

 

[boatmike]

I endorse all you say but the 2 or 3 amps when fully charged is a bit high perhaps.
Dont change it until you have had a good run with ther engine and ensured that they are in fact fully charged though because they probably aren't yet

 

[halcyon]

Once you have a fixed / regulated voltage, the current will taper off as the charge comes up, to millamps. Most cars run around 14.5 volt all day, look at hours run by a car, and hours run by your engine.
Dynastarts are regulated at 15 volt, partly due to the fact that any service loads, on the car i.e. wipers, would drop the volatgeand you never saw 15 volt. Your 15 volt is then a top end max figure, also a lead acid battery to fully charge needs around 15.6 volt. So your 15.0 volt was not that bad, though 15.6 would not be used for daily charging without a very good monitoring / control system.
Glad to hear you appear to be sorted, if you turn the adjusting screw clockwise you increase your trip in volts, anti-clockwise to reduce it.

Brian

 

[onenyala]

This is not directly relevant however perhaps any dynastart freaks out there could give me some information.
I have two Volvo MD1Bs, one on the boat and one I bought on the net as a spare. Both have dynastarters.
The flywheels on both of the engines are of course identical but the pulley wheels are of different diameters with the result that the speed of rotatation of the armatures differs by about 20%.
Unfortunately both of the dynastarters are on the boat at the moment so I dont have the exact measurements but the figures are some thing like

Engine High Idling Speed 2400rpm
Flywheel diameter 15"
Pulley 1 diameter 2.5" = 15/2.5 x 2400 = 14400rpm
Pulley 2 diameter 3.0" = 15/3.0 x 2400 = 12000rpm

Anybody any idea what is the diameter of the works fitted pulley ?
At what rpm would the armature disintegrate.
What is the result to the output of over reving the dynastarter.

 

[bluedragon]

Thanks guys...everything you've said makes sense. Good suggestions.

 

[bluedragon]

Onenyala - I can measure mine tomorrow if it would help, but my fast idle is probably more like 400 rpm, not 2400!! From what I've observed, the faster they turn the higher the voltage (that's where the regulator comes in). If in doubt, I'd use the larger pulley first and see if this gives you what you need.

 

[onenyala]

I look forward to your reply.
In the MD1B hand book it gives two 'idle' speeds - high and low these are 2700rpm & 600rpm. I guess these speeds are out of gear. I timed the rpm on my spare engine which I have had running in the garage and it revs at full throtle at about 2400rpm not under load and about 600rpm under tick over
In line with your advice I am using the dynastart with the larger pulley wheel on the engine which is in the boat. Nevertheless when I bought the No.2 engine it arrived with the dynastart with the smaller pulley in working order so it seems not to make a difference. It does seem a bit scary to have the armature rotating at about 18000rpm the centrifugal force must be enormous !