NC35 battery issue.

[MotoGeorge]

I bought an NC35 about a month ago, its had an issue with the battery for while, i just need some advice on what to change/check.

Sometimes if i leave the bike for around a week without being turned on the battery goes completely dead, not even enough to cranks the starter motor, im not sure on the age of my battery, but it doesn't look new.

People like to mention drains in the loom...i have no idea where to start, so if people can guide me id be very grateful.

The bike is an import as well, so during idle, the headlights/indicators/brake lights are all on.

Sometimes ill come back to it and it will turn over and start, other times the starter motor turns but drains the last bit of power before starting up.

Thanks guys :)

George

[speedy231278]

First, I'd fully charge the battery, and then start the bike and get a multimeter set to DC to check the output from the charging system. At idle on a 35, you're looking for about 12.8V across the terminals, which is more or less the normal battery voltage. Due to the lights always being on, the charging system barely does anything in the way of charging at idle, and is more about stopping the battery discharging when you're sat at the lights... If it's less than 12.8V, then you're probably going to get into trouble pretty quick in traffic, and also there's a chance the higher speed figure will probably poor too. Once you've tested at idle, test at 5000rpm. (it can be helpful to have an extra pair of hands to do this) At 5k, you should have between 13.5 and 15.5V. The further under 13.5 the figure is, the less charging the system is doing, and if it's under 13, then you have a problem to fix. Most people seem to consider under 14 in need of improvement. Over 15.5 and you're damaging the battery.

Both being old and over charged will/can cause a battery to go flat even if it is being charged correctly. After you've test it on the bike, take it off again, make sure that it is still fully charged (you may need to top it up again), and measure the voltage at the terminals for a week or so to see how quickly it discharges. It will probably drop to around 13V quite quickly, but then settle down and hardly change at all if it is healthy. I think the figure is about 0.1% discharge per day once it has settled down. If it drops by a lot on a day by day basis, and/or goes under 12.8 or thereabouts, it is time for a new one.

You can check for on bike discharge by disconnecting the battery negative lead, and putting a multimeter set to milliamps between the terminal and the strap, with the ignition switched off. It should be a very small figure, anything significant means you have a short somewhere, or maybe you have some accessory attached like an alarm, a clock, etc, that draws current while the bike isn't being used.

See what you find, and post the results....

[Jac-al]

how can i test to see if somethin is draining power?

[bikemonkey]

There's a earth lead from the battery to the frame, undo the earth lead at the frame and set your multimeter to amps.

Positive lead of the multimeter to the negative battery lead, and negative multimeter lead to the frame.

Shouldn't get more than 0.4 really.

(I think that's how you do it, at least that's how what I remember from testing for my drain)

Anyway the fun stuff after that is finding where the drain actually is

[speedy231278]

Set to milliamps (mA) rather than amps. Drain should be virtually if not zero. I think it's been suggested 25mA or less is the norm. If it's above about 50mA then you have a draw that needs investigating. 0.4A would be a complete disaster. 50mA will apparently flatten your average bike battery in a week.

[bikemonkey]

Cheers speedy, wrote that while watching the snooker.... Bit distracted.

[speedy231278]

I get distracted watching the snooker too. Always looking out for the dribbly bloke who used to work in my office that goes with his parents to every session of the World Championship, the UK Championship and also the World Indoor Bowls Championship, every year for the last gawd knows how... lol

[MotoGeorge]

Did a V check, at idle it produces 13, but over a period of 3-4minutes drops down to 10, then a few minutes later drops to between 8/9 and shuts off. It produces between 14 and 15 (my tester doesnt give decimal points, might be time for an upgrade?) Before testing the bike ran idle for around 10-15minutes, no problem and will happily rev, as soon as I used any other electronic control (for reference I used the passing light button) it shut off again, using the last of the power left.

Going to check the earth etc soon, I'll keep it posted

[speedy231278]

I'd strongly recommend a tester that does decimal places (and Amps, and AC). You'll need to be able to read the battery voltage to at least one decimal place if you are going to test the battery when it's off the bike, preferably two. What you describe almost sounds like the charging system is unable to maintain the charge at idle (ie the bike is using more than is being produced, hence the discharge), which is not right. However, it's very hard to tell. When I was testing my bike, I found that one reg/rec I had would suddenly stop producing any output (ie the battery voltage dropped to the same as you'd find at idle) then all of a sudden it would pick up again. The other one I had did not do this.

It might be an idea to check the output from the alternator, and the connectivity from it to the reg/rec. However, I'd still check the battery, as a knackered battery can also produce weird charging results. Unfortunately, there are absolutely tons of things that can go awry and cause issues. Often, a sick battery is not the cause but an effect, so people replace the thing to find the same issue coming back a few weeks months later.

Still, as you're checking the earth, also check the alternator connector and the reg/rec connector. If you didn't already know, the alternator connector is by your right knee as you sit on the bike. It clips together through the fairing bracket, and is a right pain in the arse to get apart - which is usually also a sign of one of the major causes of charging issues; crappy wiring. I found one broken, and two badly corroded wires when I split mine, the break probably occurring when I did so. The corrosion causes extra resistance, and robs power from the circuit. The same issues happen on the reg/rec plug, which faces downwards and gets crap thrown at it (located under the left side of the seat panel). If you find any corrosion, it's time to get the wiring kit out and put new pins on. You may also find the connectors are charred from the heat caused by the extra resistance. A replica reg/rec plug and pins can be obtained on eBay from a shop in Spain. Honda do a kit for the alternator connector, but it's about £30! If you're not worried about originality, a 3 pin plug and socket kit can be obtained from eBay for a couple of quid.

[racingt]

Speedy, bike monkey, thanks for these responses. I've understood more reading this thread than all the others put together.
Cheers!