Charging a bike battery off a car?

[Teflon-Mike]

The reason to avoid jump-starting a bike off a car, is that a car's alternator has an inbuilt regulator/rectifier and can deliver a lot of amps, at anything up to around 17.5v.

A Motorcycle generator usually has a separate regulator rectifier, and is designed to clip volts at approx 15v

If you connect a car alternator to a bike battery, in the bike, then the bikes charging system ca see the full 17v supplied by the car's alternator, and he Bike's Reg/Rect will then try and regulate that, back to 14v.... and die in the attempt!

Its a HONDA... with a the notorious Honda Regulator-Rectifier......

Personally I think that their reputation for fragility is grossly exaggerated, and that an awful lot of supposedly dead Honda Reg/Rects aren't an endemic weakness but crappy connectors and over loaded wires etc, but even so, they are NOT the toughest cookie in the tin.... is it worth the risk?

Far safer and often an awful lot easier to get crocodile clips onto diddy bike battery terminals, to remove battery from bike, and charge on the floor or in the footwell, off jump-leads, if you have to use a car to charge it... or take it indoors and do it off a mains supply where its warm.

BUT!!! Why is battery flat to start with? This is a symptom, not the disease.

Full-Time headlamps don't help; but most common cause of quck-flat batteies is often not the charging system, but the starter.

When a starter motor starts to get tired, the carbon brushes will have left a lot of carbon dust around the armature, this can alone make the circuit higher resistance than t should be, and try sucking more amps than it should, but shorting between contacts t can let other windings in the starter try drawing current too, to make magnet that is working against, rather than for, spinning starter, so starter gets slow, and tries drawing wapping current through the extra windings... that extra current over-loads thin braid straps to the brushes, making them higher resistance, so too possibly wires to the starter, all adding to the load put on the battery, with a solenoid possibly arcing along the way, also going high resistance as the area of contact actually in contact is reduced by pits or scorching on them, and you have the start of a vicious circle.

Bike battery is rated at what, maybe 12Ah. That's a nominal rating, that it can supply, or accept 12A for one hour; A starter motor s likely to draw something n the region of 90A, which s far in excess of the battery's nominal rating; it can tolerate it, only because the start up load is relatively brief, only a few seconds.... But as a starter system gets tired, so the button time tends to increase as its held longer till the motor catches.

Now, the 'Deep-Cycle-Discharge', can start to see the battery degrade much more rapidly, as the electrolyte is effectively 'boiled' by such high currents, begged for ever longer duration, and the vicious-circle accelerates...

Tired battery struggles to spin lazy starter, extended button time is used, starter not spinning so fast wears out more carbon brush, makes more dust, gets even lazier, battery starts to loose charge capacity, and is reluctant to spin starter so fast or so long, button time gets even longer, and so it goes on...

Battery is usually the first thing blamed and replaced. New battery holds more charge, spins lazy starter up better and faster, 'seems' like the problem has been fixed... only degraded starter system is just doing to the new battery what it did to the old, ad that too, starts to break down and loose charge capacity, rapidly....

A-N-D.. faced with another duff battery that seems to not hold charge, the charging system gets the blame.... Cos its a HONDA! And the regulator must be duff and have fried the new battery, mustn't it?

Meanwhile [add Sean-Bean accent!] "Wintah iz commin!"... weather is colder, electrolyte in battery is cold, oil is thicker, petrol less want to evaporate, engines are harder to start....

Autumn, sees leisure bikes layed up and stck on an optimate to hide the problem... every-day rider's start to suffer and the weather exacerbate underlying starter/battery 'problems'... and new batteries get demanded, and reg/recs blamed, as bike spends more time grnding through heavy traffic in the dark, not getting thrashed so often giving revs a chance to wack some extra charge back in the bank... and you have another vicious-circle on your hands!

To wit!

1/ for safety & convenience remove battery from bike to charge; either off jump-leads from a car, or on the bench off a battery charger. It's just easier and safer and saves answering silly questions later. (or buying expensive new regulators!)

2/ buggered battery syndrome; so often not cause of problem but symptom.

3/ Before blaming the charging system; elimnate the starting system!

Reconditioning a starter, as far as pulling it, cleaning the contractor plate, and if needs replacing the brushes is not all that hard or expensive. Brushes ae probably about a tenner. it of sand-paper and some grease, and probably less time to do than wait for attery to charge off a bench charger!

Solenoids are now often sealed for life and a more expensive possibly £25 replacement; (older ones especially on Hondas can be quite nice Frankensteins lab style heavy brass contacts that can be strpped and cleaned up with a file ad sand-paper).. but a good precaution.

Leads take moments to undo at the contacts, clean, re-attatch and water-proof with vaseline. But take tme to check earth paths; the starter earthing through its mounting, the earth braid between engine and frame, and the battery connections.

If you look at a car, the starter motor usually has its own earth strap on one of the mount bolts, that gives a direct high-amp earth often direct to the battery, rather than rely on more covoluted path through the engine block and the strap between the cylinder head and bulkhead.... such assertive earth return is no bad mod for a bike....

That lot sussed and eliminating possibilities, a new battery stands a chance of not dying an early death, and IF there's a charging problem, that being more easily identified.

Even if there is an underlying charging fault, starting will be a heck of a lot easier and battery life longer, and your chances of having to bench or jump a flattery a lot less, so its all 'good stuff'.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Pete.]

[Ted]

I'm struggling to quote small sections as I'm on a phone, but Mike are you saying the safest way WOULD be to charge the battery in the footwell of the car on the move?


My only real option on mains charging is grabbing a cheap bike maintenance charger, and parking the bike in the fire escape stairwell of a shared parking structure, where there is a plug socket.


Battery is flat due to starting the bike to move it / load into vans, but not riding it.
____________________
'07 Honda CBF500 / '93 Vauxhall Astra (www.fb.com/2wdOffRoader) / '04 Vauxhall Movano
Projects: '81 Honda CX500 x2 / '85 Land Rover One-Ten / ...plus many horticultural things.
||| Bike Test: DAS: PASSED 13/02/2009 ||| Car Test: PASSED 22/05/2005 |||

[doggone]

Not convinced a car alternator supplies at higher voltage, but it has more amps.
It's still a 12V system and if anything cars have more computery things that won't like out of range voltage.
If everything is charging normally it should be at 14.8V

[Rogerborg]

[Polarbear]

You are overthinking it. Just charge it of whatever 12v charging source you have. Anything that charges a 12v battery at a 'normal' rate will be fine.

Anything's better than leaving it flat, nothing fucks a lead acid battery better than that.
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Triumph Trophy Launch Edition

[Teflon-Mike]

[P.]

Mate, at the cost of a new battery... I'd do that rather than trust a Teflon.

[Ted]

[Ted]

[haroman666]

I'm not too up-to-speed on why you can't buy a charger, remove the battery and then charge it?

If it's purely to jump start it, then yeah, jump from the car battery. A non-running car will jump a dead bike perfectly fine: Even a 1000cc V-Twin (Source; I've done it).

But to save all of this seemingly avoidable arse-ache: buy charger, charge battery, ride bike. Profit?
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The mistresses: 2000 Honda CBR600f, 2000 Honda VTR1000

[Baffler186]

[G]

[Ted]

The issue is the wife, yes. No fireproof blanket in there, but the landlords have given us free contents insurance for when the place falls/burns down.
____________________
'07 Honda CBF500 / '93 Vauxhall Astra (www.fb.com/2wdOffRoader) / '04 Vauxhall Movano
Projects: '81 Honda CX500 x2 / '85 Land Rover One-Ten / ...plus many horticultural things.
||| Bike Test: DAS: PASSED 13/02/2009 ||| Car Test: PASSED 22/05/2005 |||

[Northern Monkey]

Why don't you just jump start it off the car, then go and ride it.

Pretty much any option will work with the exception of what ever Tef recommended.
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Fisty: after polishing the tank with the glistenng beads of sweat from my full hot scrotum, I filled the headrace bearings with 10cc of my manmilk

[P.]

If it helps your Mrs to stop being a fag, my bike, in its entirety is in my living room. Fuel + battery still there, key in ignition. I occasionally sit on it and make noises.

A battery being on charge is going to be zero risk, less of a risk than turning a light switch on. Stop being a fanny

[Nobby the Bastard]

[Ste]

[Ted]

[Rogerborg]

[Ste]

[Nobby the Bastard]

[Mr Hammers]

The only real solution to your problem is to either man up, or get yourselves to Relate.

That's at Ted, btw, not Roger and Ste...
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A Guide To Powerbands

[Ste]

Ya piece of crap.

[haroman666]