My nc21 started failing to proceed about a week ago but I wasn't able to aford a replacment battery untill today, when I took it off it was deformed with bulged out sidewalls and generaly looked like it had melted!
I have replaced it now with a regular acid type one (rob hunter) battery and runs as it always did!

But I'm worried the new battery might end up deformed as well, what causes this to happen is it normal if a battery is fully flat then recharged quickly ie a 2 hour ride at about 5-7000 rpm?
Or could it be more than just a replacment battery that's now required?

it could just have been a knakerd battery, or it could be reg/rec fault.

if its the later your new battery wont last long.

id say test your reg/rec get a multimeter and follow the guide on here.

2nd post


viewtopic.php?f=10&t=26309&p=187528&hil ... ec#p187528

just checked the voltage at battery at idle 15 volts and goes up to 19+ when revved up, so i presume new reg rec!
any ideas if the nc24 ones the same as the 21's?

Just did a search for regulator rectifiers and turns out the part numbers are the same for the reg rec as the vt250 and cbr400 and nc24 wounder how many other models share these parts!
Also the vt250's reg rec has a heat sync so might last longer!
Is a part number enough info to place an order or should i go for the one specificly aimed at nc21s?

Deformed battery with bulging sides is from exposure to heat, you reg/ rec has been cooking your battery!

Vfr400/tbird wrote:My nc21 started failing to proceed about a week ago but I wasn't able to aford a replacment battery untill today, when I took it off it was deformed with bulged out sidewalls and generaly looked like it had melted!

You were lucky it didn't go bang and take yer arse off... the casing expanded because the electrolyte has boiled up and the battery vent tube was blocked...

It's new rectifier time. The NC21 ones are crap and too small, when mine went I replaced it with one from a Yam R6 - there's ample explanations of how to do it on this forum.
viewtopic.php?f=24&t=13921 is a good start...

You might have killed the new battery too.

Anything longer than a few minutes at that high voltage and you will do irreparable damage to the battery.. this will cause it to no longer take as good charge (even thoguh it might still work ok)

This is why the reg-rec dies in the first place.

Explanation

The standard Honda reg-recs arn't super-heavy duty. Most bikes, especially in the UK arn't used very often and the batteries live a hard life... being left in freezing cold... ran to almost flat and never kept charged (an optimate works wonders)

All of this sulphates the battery up, this means it can't take as good a charge as a healthy batery.. this happens over time too, generally a few years but neglect above makes thsi problem happen a lot quicker.

The reg/rec has to burn off excessive charge as heat! this cooks the reg/rec and it breaks down and either stops charging the battery or over-chrages it and boils away the battery.

Firstly: Replace the battery with a brand new one.. fill it with acid if its a wet type (wll be for NC2x) and follow the appropriate break-in procedure (this is usually a LONG slow charge with a proper bike charger)

Use an R6 reg/rec.. there extra heavy duty and your battery will likely give out before the reg/rec.. there easy to wire up.. you need a 1999-2005 model a 2nd hand one can be had for around 20gbp from ebay.

You need to cut the existing plug off and solder spade connectors on, crimp is no good, needs to be soldered.

Tanya.co.uk are the cheapest place i found for good batteies.. a VARTA batterys is only around 20 gbp.

You need a YB9L-B battery

Can I fit the r6 reg to a nc21 or is primerly nc30s this mod applies to?

I have an R6 reg/rec fitted to my NC21, it's not on the road yet but I don't expect any problems (after my original one died and left me bump starting my bike for a year...) Get one from eBay, connect it as the posts on this forum suggest, and Bob's your uncle. Your biggest problem will be deciding where to mount it...

People are fitting them to all makes and models of bikes, not just Hondas, so I don't think you'll have a problem with it. I think it's taken over as the reg/rec of choice for general modification (it used to be a Superdream one if you were wiring a bike from scratch)