Author Topic: CB125S - losing the battery (Read 13230 times)

Untold · « **on:** August 22, 2013, 12:26:14 PM »

So I've got a 1975 CB125S that was converted to 12v by the OP. They had used a small 12v battery, but on the first ride I took it on, the battery ended up smoking like crazy and it melted. No big deal, because the bike runs fine without the battery. I was expecting the lights not to work, but they did!. Blinkers too!.
Although all the bulbs burnt out when I ran it without a battery.

So here's my question. The bike has no battery at all. I want to keep it that way. It runs fine. I just want my lights to work. I know they are currently wired up so that they all work off the magneto. Can I just use a 12v regulator to keep my bulbs from blowing? I'm a complete idiot when it comes to electrical stuff, and I've done some searching and everything that talks about capacitors leaves me scratching my head, and I'm not sure that's what I need for this application.

I come from the world of 70's pedal mopeds, which don't use batteries and have working lights. I've converted some of them to 12v in the past, and a regulator was all I needed. I'm just looking for confirmation that it also works this way on the 125.

Thanks,

grcamna2 · « **Reply #1 on:** August 26, 2013, 03:09:48 PM »

I'm not sure about a capacitor/regulator for your bike...,if it was me I'd fix the 12 vt. system & have a great all around night/day rider w/ working signals that actually "Blink" with the lights on at idle.I think you'll keep blowing bulbs,rectifiers,etc. if you run it w/o a battery.I know there's a member here who's done a 12 vt. conversion on his CB125S & I think it's step by step on the forum post thread called "Big Blue".I think it'll be time well spent to fix that 12 vt. system.

Untold · « **Reply #2 on:** August 26, 2013, 07:13:15 PM »

Thanks for the reply. I am leaning that way, but the bike is really chopped down to the bare bones, and I like not having to worry about mounting the battery. As it is, I'm just riding it during the day. I've got 3 other bikes, including another CB125, so this one is just a toy.

grcamna2 · « **Reply #3 on:** August 27, 2013, 10:44:03 AM »

I'd Love to find an 82' CB125S that's been sitting for a WHILE,or that needs work, complete.;that's my long range hunt.

WhyNot2 · « **Reply #4 on:** August 28, 2013, 11:43:58 AM »

As is my CB100, so I will be watching to see what you come up with.

I'll probably do the same. I still have to get the engine unstuck and bored to 50 over.

Like to see some pic of yours.

Untold · « **Reply #5 on:** August 28, 2013, 01:46:54 PM »

Here it is in it's current form, minus the battery you see under the seat. The tank is from a Cb200. Front brake converted to hydraulic.

grcamna2 · « **Reply #6 on:** August 28, 2013, 04:02:45 PM »

untold,
What are the fork tubes you're using ? I like them. & the HYDRAULIC front caliper

Untold · « **Reply #7 on:** August 28, 2013, 05:28:57 PM »

The bike already had the forks [and tank] when I got it. As far as I know, they're stock cb125 shocks, but not sure what year. I put the headlight ears on, they're from moped EBR forks. The hydraulic conversion was just copied from someone on the hondatwins.net forum.

Here's the caliper and master cylinder I used.

http://www.lifanenginepartswholesale.com/scooter-front-brake-assembly-front-brake-assembly-10-for-chinese-150cc-scooters-mopeds-p-12916.html

My bike had the stock mechanical disc brake setup, and this caliper works with the stock rotor. You'll just need to make a bracket to mount it to the fork leg. The brake line that comes with it is a little long, so I got a shorter one from Venhill on ebay. The old brake was useless, this works amazing. Better than my 550.

Untold · « **Reply #8 on:** August 28, 2013, 05:30:52 PM »

Also, the brake pads float, so the bracket does not need to. Makes it pretty easy to fab up.

Untold · « **Reply #9 on:** August 28, 2013, 05:39:11 PM »

Chopped the brake lever off of the stock throttle assembly to fit the MC and new brake lever

Stock rotor and custom bracket

grcamna2 · « **Reply #10 on:** August 30, 2013, 07:34:35 AM »

That front caliper & master cyl. look a lot like Honda XR type. Nice.

Steve_K · « **Reply #11 on:** August 30, 2013, 01:50:45 PM »

Enduros in the 70's had a problem that when the battery was gone or dead that the bulbs would burn out. The battery worked to keep the voltage from spiking when the the engine was revved. That may mean that you will need a battery or something to control voltage spikes. A post did mention a magneto and a battery does control voltage spikes.
Nice Looking bike!!
Steve

Untold · « **Reply #12 on:** August 30, 2013, 01:56:55 PM »

Thanks Steve. That's where I'm hoping I can replace the battery with a regulator of some sort. I don't really mind putting another battery on it, but I guess I would need to figure out why the first one went up in flames before I ruin a second one.

RAFster122s · « **Reply #13 on:** August 30, 2013, 09:40:35 PM »

S90 uses the battery as a huge sink to help regulate the voltage and excess charge is dumped when battery is charged. But like many/most early Honda charge systems they don't charge below 3k rpm.
Bulbs will blow as there is nothing to stop the voltage from being regulated.

Capacitor banks have been used as well as a 6v pack of D cell Nicad battery (not Ni-Mh). Some D cells are just a C cell in D cladding so, don't be fooled by that. Usually a true D would be a larger capacity cell and weigh quite a bit more and cost more.

Untold · « **Reply #14 on:** August 31, 2013, 07:33:15 AM »

Thanks. This has been converted to 12v. The battery that was on it was a 4-cell one of these:

http://www.ballisticparts.com/products/batteries/batteries.php

After a shortish ride, it started spewing smoke and hissing, so I jumped off the bike and hit the kill switch. The battery proceeded to melt, and I had to run into a convenience store and grab a pair of scissors to cut it away from the bike. What could have caused that? Was the battery just too small to handle the charging voltage? It wasn't shunting the extra power as your post suggests it should have.

RAFster122s · « **Reply #15 on:** August 31, 2013, 08:02:53 AM »

Uh, it is a lithium battery...very rare that you can cause a LiFeO4 battery to do that, they are durable and usually tolerate high discharge and charge rates well, but apparently they aren't tolerating overcharging.

Lead acid and lithium are two different animals...

Untold · « **Reply #16 on:** August 31, 2013, 08:13:43 AM »

So any idea what I should be looking at to avoid this in the future? Or should I just throw another battery in and hope it doesn't get fried?

Untold · « **Reply #17 on:** August 31, 2013, 08:15:20 AM »

If it makes a difference, the battery was hung below the seat and it was kind of rattling around when i was riding. Could that have had any affect?

grcamna2 · « **Reply #18 on:** August 31, 2013, 09:56:19 AM »

What if you bought a YTX-4BS type of little 12 VT. MC battery & put it in a custom little "battery box" that will be pleasing to the eye on your bike ?

Untold · « **Reply #19 on:** September 03, 2013, 06:58:31 PM »

I'm pretty clueless when it comes to the difference in batteries. Especially since this is a 12v conversion, so I can't rely on just finding a stock replacement.
Can someone point me to which 12v battery would be appropriate? I don't know what the different letters mean, and they all seem to be similar in size. What's the difference between YT5AL and YT5L-BS? Well, I guess I can see that they have different specs, but would either be ok for just using a kick start and trying not to blow the bulbs, and also not catch fire?

http://www.batterystuff.com/all-products-by-brand/scorpion/

RAFster122s · « **Reply #20 on:** September 03, 2013, 07:48:43 PM »

Battery bouncing around could have shorted to metal and resulted in fire.
usually the letters refer to things like terminal type, which end is positive, etc.
Battery manufacturer should have a code decoder if you can find it...at least a larger old brand should.

Quote from: Untold on September 03, 2013, 06:58:31 PM

I'm pretty clueless when it comes to the difference in batteries. Especially since this is a 12v conversion, so I can't rely on just finding a stock replacement.
Can someone point me to which 12v battery would be appropriate? I don't know what the different letters mean, and they all seem to be similar in size. What's the difference between YT5AL and YT5L-BS? Well, I guess I can see that they have different specs, but would either be ok for just using a kick start and trying not to blow the bulbs, and also not catch fire?

http://www.batterystuff.com/all-products-by-brand/scorpion/

scottly · « **Reply #21 on:** September 03, 2013, 08:40:17 PM »

Quote from: Untold on August 22, 2013, 12:26:14 PM

So I've got a 1975 CB125S that was converted to 12v by the OP.

Just how was it converted to 12V??? The tiny bikes didn't use voltage regulators; there were extra stator coils that were switched in to provide extra power when the headlight and taillight were on. Honda made a wild-assed guess as to how much power was required in each case in order to keep the battery charged without over-charging, given the lack of a proper regulator. My C200 would let the battery discharge to the point that hitting the horn button or rear brake would kill the motor. It took a while before I figured out that when the battery was dead, all I had to do was turn the headlight on, instead of limping the bike home and putting it on the charger.
YOU NEED A SHUNT REGULATOR to limit the max voltage to a safe level for both light-bulbs and batteries, regardless of which type of battery you are using.

grcamna2 · « **Reply #22 on:** September 09, 2013, 02:22:53 PM »

How's it going Untold ?

Untold · « **Reply #23 on:** September 09, 2013, 05:34:15 PM »

Haven't really gotten into it too deep yet. I think I'm just going to get an AGM battery and hope it doesn't fry like the ballistic 4-cell did. But I need to get all new bulbs. I'm way too clueless when it comes to electrical stuff to attempt anything groundbreaking.

grcamna2 · « **Reply #24 on:** September 10, 2013, 10:01:31 AM »

I'm familiar w/ that YTX4-BS because I believe it comes standard equip. on lots of bikes;it's a common 12 Vt. for small bikes.

ps. I may have the - in the battery number in the wrong place,but it's such a common batt. you'll be able to price around a little.

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Author Topic: CB125S - losing the battery (Read 13230 times)