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wiring up for a heated jacket

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wiring up for a heated jacket

Posted by robert_tuck at January 31. 2017

I have a gerbing heated jacket which is wired up to the battery and works , although a bit optomistic with a 1960 12v 99 and RM15? alternator.As the bike attempts to compensate the ampmeter goes beserk and will probably frighten itself to death.I'm thinking that I would like to see what is really happening and the meter needs to show the nett result . I think I should take the feed off the rectifier to ampmeter wire?.I did simplify the wiring 20 years ago and the charging probably bypasses the PSR8 switch which means less to go wrong.The jacket is radio controlled and keeps me warm on the lowest setting so probably only using 20/30w.

Re: wiring up for a heated jacket

Posted by david_evans at January 31. 2017

To show whether the alternator is keeping ahead of the game you could fit a small digital voltmeter across the battery. I have one on a Commando that is taken from the feed to the light switch and then earth. It effectively shows the state of the battery and if the alternator is coping then you would expect to see a steady voltage around the 13v mark. If it starts to drop, start switching things off. I have a fat wire running the length of the bike dealing with earth rather than the frame. (how does electricity complete a circuit through the headstock bearings covered in grease?)

Re: wiring up for a heated jacket

Posted by les_howard at January 31. 2017

Yes Robert. If you want to monitor the total balance* of power being used, the jacket wire should be on the same side of the Ammeter that is fed from the rectifiers output (as you suggest).

The other side of the ammeter should feed the battery only or any other electrical item you want constantly connected to the battery without showing its current consumption on the ammeter when in use...(not recommended but sometimes the stop lamp is wired this way)

* The sum difference of the alternators output and the batteries output (or charging current)  vs the consumption of the bikes electrical loading.

Also note that the bikes ammeter is only there to indicate what current the BATTERY is receiving or giving out...NOT the generator's power output.

Les

Re: wiring up for a heated jacket

Posted by robert_tuck at February 01. 2017

Hi les, Yes the ampmeter is mostly showing the alternator output (which is a bit distracting,and alarming!)  After 20 years use I'm surprised to see the needle so far across the gauge ,thought the old alts are supposed to be feeble. Its powering coil ignition ,a Boyer box, indicators, a 40/50 watt H/L. and now a heated jacket. I'm expecting a big escape of Lucas smoke anytime. Re rigging the jacket feed from the rectifier output should give a better idea of the power balance (if there is one). The jacket has connections for heated gloves, do I dare??.

Re: wiring up for a heated jacket

Posted by les_howard at February 01. 2017

Don't worry about overloading the Lucas alternator as their "drooping" voltage characteristics means they can even drive a short circuit without heating up too much. In fact some wiring systems deliberately short out some coils to lower the magnetic flux across the other coils to reduce the power produced in them. So you will either have enough power to heat the jacket and gloves or not and this will be shown on the ammeter as a discharge from the battery if the alternator fails to produce enough power to balance the load, but no damage done to the electrics...as long as the wiring can handle the drain current that is....you can fit a safety fuse.........Les

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