Hitchcocks Forum

Thanks for the replies; I forgot to add I fitted electronic ignition to the bullet I reversed the battery polarity on...
Have I knackered the unit?
The bike starts alright with battery connections the right way but dies when putting the lights on..
And why would the brake light bulb holder point give a 12v reading on brake light activation and not when the bulb is in the holder, that won't light up??
Thanks for advice..
Greg.

It is possible you have damaged the battery by connecting it up the wrong way. With the battery disconnected check the voltage directly across the terminals and also check the polarity of the battery is correct and hasn't itself become reversed. Not something I've come across myself but apparently it is possible after charging the wrong way round. My bet though will be a damaged rectifier/ regulator so if the battery is OK then check the alternator output and regualtor/ rectifier output as per our hosts technical guide. As for the bulb leave that until you are sure the rest is ok. Might have simply blown it by the damaged rectifier/ regulator.

Hi Greg, most electrical item nowadays have a diode/s on the power leads that prevent damage due to wrong polarity connection. The reason you can measure 12V is that you are measuring ELECTROMOTIVE FORCE which is the voltage potential available when no current is flowing in a circuit. Some minute current is drawn by the meter but it is so tiny hardly any voltage is lost along the wires. However, if you have a high resistance in that wiring, and attempt to draw a largish current, a voltage drop will occur due to V=I/R. So if the resistance of the brake light circuit is very high then the bulbp will attempt to draw current but the voltage available will be reduced to an amount insufficient to light the bulb. So it seems you have a very high resistance in your wiring or you have a very high resistance inside your battery which means it is only fit for the dump.....although I know of ways to revive them.....but that is another lengthy topic.

OOOPS!: V = I x R (Volts = Amps X Resistance in Ohms)

Interestingly or not (depending on your point of view) v=I/r is also the way you establish the quality of an investment v value =I investment over R return. Sorry total off topic but true none the less.

Hi guys-------- just to say}--- The Enfield may be rubbish but you sure meet some quality folk on this site !!!!! SIMON, that formula can also be applied to the actual OWNERSHIP of your Enfield, thus }--- If V = The value of your bike to you ( cash, emotive, poser, etc.)------- I = The total investment you have put into that ownership ( Purchase, club membership, shopping at Mr H's, posing ),-------- and R = The total amount of actual riding hours (or miles) and posing,---------- it can be seen that the main factor appears to be}--------------- we tend to "pose" with our bikes more than anything else !! How many times has that "Certain old Chap" in Tesco's car park or in the Petrol station or when out riding--- come over to you and started off with }---" I used to ride one of those " OR " Do they still make them then ??" --- So you see that formula does apply to us owners as well.... Just try varying each unit, greater or lesser, to get a result.... SORRY GREG, to back-up LES's input----- you have an electrical SUPPLY at the tail lamp holder ( That's the VOLTS that you are seeing)but there is not enough ENERGY (Amps) with this to light up the bulb.... LES, back in the day I remember one of our local battery suppliers offered a service whereby they would drain the old electrolyte and re-fill with fresh...worked ok if none of the cells were shorted out by accumulated (note the electrical pun ??) dross at the bottom, but cost almost as much as a new battery.... Srewth, look at the time !! Cylinder head to fit and road test before this week end. ta-ra !!

I can't see that draining the electolyte and refilling with fresh would have any long term benefit. The problem with old batteries is sulphation building up on the plates reducing the electrolyte's ability to react with them. To some extent this can be removed by repeatedly putting the battery under load until it reaches a point just above being flat and then recharging. This will restore the battery's capacity to store charge over time. Replacing the electrolyte will temporarily raise the specific gravity of the acid of the battery to that of the fresh acid but it will soon go down as full charging will not be possible through the sulphation. Once a battery has got to this state though the plates are probably breaking up and liable to short so you might as well go and buy a new one, preferably a gel filled one!

Hello FRANK---------- yes, quite so. I wasn't for one minute advocating that GREG actually do that; indeed I make the point that it cost almost the same as a new battery and was only of any use if the plates hadn't sulphated unduly. It was usually offered as a quickie, short-term fix... I agree with you, a nice new GEL battery as a Christmas "treat" and an apology for that belated Bullet of his.

Not impressed with gel batteries, I have found them to be worse than lead acid. I have 4 here that have failed in the last 12 months they show 12 volts but won't light a globe. Glass matt seem a lot better and cost about the same

I think the battery is going to have to be pretty duff if it can't supply the load to at least get a glow from the stop light, and if Greg is getting 12v at the holder it suggests that the battery is not that bad. Since the stop light is the only light to be mentioned I presume the rest are working ok ? Perhaps the stop light fault is a seperate issue present before the battery reversal, and only noticed when checking over all the electrics after that was corrected? Greg, it will be interesting to get the final result!