Hitchcocks Forum

Mysterious Voltage


Just bought a 2004 500 Bullet. It had been SORNED in a damp garage for 18 Months and had a flat battery. I piggy backed another battery across the terminals of the flat battery and 2 or 3 kicks later the engine fired and ran fine with 18 month old petrol!!!


After a few minutes I disconnected the new battery assuming the old battery would have enough charge in it to keep the engine going. No luck, the engine stopped.


After taking the seat off found it had been fitted with a Mk 4 Boyer electronic ignition and a Boyer power box. With a new charged battery fitted, I tried all the electrics, sidelights, horn, indicators, brake lights, all OK.

Started engine, unplugged the power box and checked across the two violet wires from the alternator. The voltage was about 30Vac so OK.
Checked DC voltage from power box about 14Volts so OK.


Checked at the battery and volts were down to about 12.4, no amount of revving would give more volts.


Ammeter only shows negative volts, flicks down when indicators are put on.


So in short, it all works except the battery wont charge.


Why not, Help please.


Regards Fred


Ps checked as many earths as I could find but surely if all the lights work then the earths are OK

you say new battery fitted. Would that be a newly bought battery or one you already had. The reason I ask is that with the volts you're quoting it seems that the Battery is u/s. Put the battery on charge overnight, disconnect in the morning, leave for about half hour then check the voltage. And post findings here please. Not unknown for a new battery to be faulty, happened to me last year.

I think he said he piggybacked the battery, and the engine stopped after he removed the new (piggybacked) one.



If a lead acid battery went flat and was still in storage for some time, then it is probably knackered. You may be able revive it a little, but it looks like you may well need to replace it.

It could also be the powerbox will not work under load I.e. when connected in circuit. I've had this on my Interceptor 1a. which had exactly the same symptoms as you describe (30v from alternator, 14v from pb when disconnected but only 12v across battery when everything reconnected.)
In my case I sent it back to Boyer for testing and they supplied a replacement F.O.C.

I'm not happy with the last 2 Powerboxes I have fitted I won't fit them anymore, I'm looking for something else

Hi Beesa new battery charged & left 36hrs and volts were still 12.83V.
Even the old battery held a charge of over 12.8V after a couple of charge & discharge cycles with an Optimate 4. Both batts are Gel batts.
Wish I hadn’t bought the new Batt, still a spare battery is always useful.




Rancid & Norm—This is the first time I’ve heard anything against the PowerBox. All I’ve read on this site previously has nothing but praise for the PowerBox.

So what to do? Go back to an old Regulator and Rectifier or buy another PowerBox?



Regards Hot and bemused Fred

Fred, I'm actually a fan of said powerbox and have fitted them to ten bikes ( both mine and others I've re-wired) but I have had one fail. If you know someone else with a powerbox equipped bike you could try sustitution or give Boyer a ring and see if they will test it for you. Failing that there are cheaper reg/rectifiers available but these don't have the large capacitor the powerbox uses and will not therefore start a bike with a dead battery.

Freddy, One if fitted to a Meteor that I fitted a 3 wire stator to that gives good A/C voltage but it only puts about 12.7 into the battery and the other one I fitted to a Super Meteor with a 4 wire stator and it just puts a flat 14.5 into the battery regardless of the revs. I now have disconnected 3 of the stator coils,still 14.5 at the battery but by running with the lights on all the time we have reduced the battery charge rate down to just under 13 volts. I emailed Boyer about it but they just said that 14.5 volts at idle was fine but I'm not prepared to cook a battery

Other single phase reg/rectifiers with built in capacitors are available, eg the Sparx SPX023, sadly not sold by our hosts, so you'll have to Google for it (other search engines are also available).

A.

Update—Just had another go at it. Swapped the power Box over to my other Bullet and battery charged up just fine, so power Box all OK.

.



WHAT do I check next?

.

How to check the alternater, bearing in mind I have already tested and found 30V AC at the socket going to the Power Box.

.

Or what wiring to check, again bearing in mind that all the lights etc work fine off of the battery

What am I doing wrong?