Smaller battery for relocation (6v on a cb125j).

[manox]

Hi, im a complete newbie when it comes to bikes with engines (worked on push bikes and cars for years, but finally got myself a bike).

Im building a mini cafe racer from a honda cb125j, which has been stripped down and started to be put back together.

Question is (an im sure its been raised before), but is it possible to run a smaller battery than the standard 6v block? Im wanting to relocate the battery to give the bike a cleaner look.

Ive read bits about converting to a 12v system, but if theres another route (ie Easier and cheaper), it'd be tons better.
Is it a case of finding a smaller battery with the same voltage and amp per hour capacity?
If anyone can help, i'd be very much appriciative as this subject is doing my bloody nut in!

[MickC]

[MickC]

Something just crawled up the back of my mind, does it have a kick start?. If so it is possible to do away with the battery. Here's a link to a page that will give you the general principle:

https://www.porkersusa.com/tech_tip_articles/electrical_run_without_a_battery.html
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Previous: CG125,XS250 (converted to 400),Z250A, GPZ550, Norton Commando, XS500, 78 Laverda Jota, GPZ1100,Harris bonneville, XV750 (mono shock),TR1

[zombie_dave]

[manox]

Its a 78 CB125j, with a kickstart and currently runs 6v (i believe its always been a 6v system.

The no battery thing does sound like a good idea, but im looking at the simplist way hopefully.

The idea is that im getting rid of the air filter housing and with that the battery strap/ casing.

Ive seen tons of bikes running smaller batteries, but no real guide or explanation how its done!

Cheers for all your help! Keep it coming please!

[zombie_dave]

[robocog]

if you are running lights I would suggest researching putting a suitable capacitor in place of your battery -Its something that is required for proper regulation/rectification AFAICT
(unless your lighting is also AC?)

I have a CG125 that I'm still giving the cafe treatment to
I found that I was blowing bulbs if the bike was revved and the indicators simply would not work without a battery or at least a capacitor where the battery was

Got a thumping gert capacitor off ebay for not much money and I will be going with this on my project...though I may downsize it if I cannot polish it up and make a feature of it

Before playing - please read up on capacitors though- they can be lethal if handled or fed incorrectly!

Regards
Rob
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Needs a bigger garage...

[manox]

Cheers Rob, Good advice that i will now spend the weekend researching. I will be running lights, indicators, horn etc as its a road bike, but only will use these when the bikes running.

Excuse my naivety but it sounds like a straight forward job of replacing the battery with a suitable capacitator and wiring it in line where the battery should be?

Is there any other mods needed?

genuinely excited if this is the route, as it will make the bike look so much cleaner and save some weight!

Big thanks!

[robocog]

Its all I have done with mine- no other mods to the loom
Took battery off, and put a big capacitor in its place, hey presto no more blown bulbs and indicators all work (engine running only of course)

PLEASE heed my words of caution though and research before hand

Capacitors will pass all available energy pretty much instantaneously unlike a lead/acid battery and are more than capable of killing a person and can go bang with a LOT of force and should be treated with absolute respect unless you know 100% they are completely dischared
I'm going to keep the lights on permanently so its always discharged when the bike is not actually running just in case curious fingers find their way across the terminals

I have not run the bike for any great length of time with the cap in place - but it didn't get warm last I ran the bike up with it in place whilst I tested the lights and indicators

If the reg rect goes bad I suppose it /could/ be possible to overwhelm it (feeding it wild AC direct from the genny??) and be oblivious till it goes bang

It does have a fuse in line with it and I may put a fuse on each terminal for paranoias sake

I also intend mounting it with the vent pointing well away from fleshy bits as well!

Regards
Rob
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Needs a bigger garage...

[robocog]

https://www.bikechatforums.com/viewtopic.php?t=189514&highlight=batteryless

That was my initial post and the susequent discussions

TLDR;
mine is a 1/3 of a Farad and 40V, physically inbetween a can of coke and a small can of redbull in size and /seems/ to work OK so far for my experiments- my project bike is not yet on the road so only has had very limited testing!!!

Regards
Rob
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Needs a bigger garage...

[Teflon-Mike]

Battery acts as charge reservoir; capacitor acts as charge damper.
Imagine a capacitor as a spring in a brake line; transmits the force but takes out any shock in the line; where a reservoir would accumulate pressure and let it be used for longer.

I have 6v electric Yamaha DT, and am messing around with a 12v pit bike regulator, to convert to 12v. Generator is supposed to chuck out enough volts, and using both coils, the charge circuit and direct lighting circuit, ought to provide enough amps to keep small 12v battery charged to power 12v lights without the low rev 'drop of' direct lights suffer, while 12v offers more compatability for modern upgrades like LED's to lower power demand and make more juice available; possibly even a PIR headlamp for more light without less amps still.

This may be possible on the CB125 single's generator.

Alternatively; sticking with 6v, knowing 6v systems of old, even with a battery low rev lamp dimming is a pain. Many bikes of the era ran 'direct lights' so they didn't get any top up from the battery so were entirely dependent on genny revs for volts; battery only powered occassional equipment like horn and indicators.

Using a 6v regulator, possibly from an early 6v CB200 Benley, and routing direct light circuit and charge circuit through it to charge a battery to power all equipment, including lights, would be a good move, and make electrics more reliable.

Another alternative, still being toyed with for the DT, is if the genny and pit-bike regulator dont prove good enough to convcert to 12v... going 12v 'low amp' conversion anyway, using LED bulbs for indicators, dash tell-tales, side, tail & stop lamp, and a solid state low consumption indicator flasher, and a 35W PIR headlamp, and running the system 'Total Loss', having two batteries; one on the bike, one on charge in the house!

Lights dont HAVE to be self sufficient....

On a 78 model bike; you also don't HAVE to have indicators, and need only have the brake lamp work of one brake lever.

Two types of battery commonly out there

Standard batteries are wet acid filled. They have to be mounted terminals to the top or the acid sloshes out through vents.

'Sealed' batteries are often wet acid filled, but unvented. These tend not to have the charge/discharge rating of vented batteries, and are not usually reccomended for bikes or cars. Competition bikes and cars often use Sealed 'Gel' batteries that have an acidic gelly (yes basically you make a jelly like you would for a trifle of kids birthday party, but with sulphuric acid rather than water! And fill the battery with it!) More stable, can be mounted in any orientation to suit, and wont slosh acid. But expensive.

For your wants, I would sugest that a sealed, preferably gel-cell battery, of the same or greater amp-hour capacity, would be more suitable. You can find a place to site it to convenience, and tilt it to suit. Meanwhile, need not be bigger than original; external dimensions can be smaller on modern batteries.

If you are not putting heavy charge or discharge rates on the battery; if you have currently a direct lighting system, battery charged by excess genny amps at a trickle to power indies and horn, you probably could get away with a 6v 'sealed' burglar alarm battery; these are fairly cheap on e-bay, but check Maplins for specs and dimensions; they are designed to hawve very long service lifes, typically around ten years, but with very low charge and discharge rates, sat in a box on the side of a house providing independent suply for a lamp and claxon if the alarm goies off and the mains supply is cut. They are commonly de-rated for consumer products; thier life expectancy shortened, exceeding the specified charge and discharge rates, for use in things like car battery 'booster' packs, or kids ride on toys and stuff; Charge rates exponentailly reduce battery life, so double the charge/discharge current, battery life drops by a quarter, BUT, you can go quite a long way before you are down to the one or two years 'life' of a conventional bike battery.

If you want least-fuzz, solution, keeping the electrics 'as standard' but able to put battery where you like; I think this is what I would suggest as most suitable; Burglar Alarm battery in the 3-5Ah capacity range your CB-J battery is likely to be in, probably barely any difference in price to the OE spec wet & vented battery.

Depends how adventurouse you want to get; BUT do have a think about going 12v. With low wattage LED's sucking milli-amps instead of amps, you can make a small capacity 12v battery last a long time, even if you run it 'total loss'; and you have far more scope to start choosing from far more 'standard' 12v equipment, thats often better and or cheaper than whats available in now rarely used 6v components.
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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?'

[manox]

Mike, you know your stuff! I've had to read that twice, but it's been fantastic.
Like I said, I want a relatively fuss free swap as I've got my work cut out getting this bike together (it's a first bike to pass my test on, and eager to get riding).
So searching for a sealed unit with similar ah (or does it have to be the same?) and same voltage. I know there is a sealed direct replacement, however they are exactly the same size as the oem (so defeating the point of this thread a bit).


So a battery like you suggested off a burglar alarm/kids toy would be a plug, play, tuck away job? I'm happy to replace it yearly as it's going to be a dry rider, not a daily whip. If so, I want to buy you many pints as you've solved it!

I'm used to cars where this kind of stuff isn't so crucial. Every days a school day!

Thanks mate

[Noxious89123]

You can get small + light 12v LiPo batteries for race bikes that are much smaller than a normal lead acid battery. Rather pricey though!
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