Battery not Charging - High output Alternator?

[beardyweirdy@me.com_imp]

After stopping for a break in Le Touquet, on a very cold run from London, the CB wouldn't turn the starter over. I bumped it and after a 30 min run to the hotel, running high revs, it was fine again and started off the button.

My battery is 2 1/2 years old. The bike is run regularly but not left hooked up to a charger and lives outside. It's winter in the U.K. And getting a bit nippy...
I was riding with a pillion, both running heated jackets and gloves, and I was charging my phone.

Obviously, I wasn't surprised that the battery took a hit. It's probably getting a bit old, it's cold and we were drawing lots of power. It's just that we had done that before without problems and we did the same on the way home. The bike has started on the button since.

What I think caused us the problem was the slow, lazy ride from the ferry to Le Touquet. We were plodding along the coast road and dawdling thru the towns. Running low revs, as we were two up and taking it super easy.

I've heard before, don't know where and if it's true, that Honda Alternaters don't output much below 3 -3.5k revs. Anyone know if this is right?

I'm thinking that I'll change the Battery now anyway, as it's getting on and it's the season for trouble. I also wondered about updating the alternator? Anyone done this or know of an alternative? I've fitted high output alternators to Brit bikes before but never thought I'd need more on the Honda. Also, it's not necercerily more, but more at low revs....

With a new battery, it all could be fine, but I'm going to be in this situation again and bumping the bike, fully loaded isn't something I fancy doing regularly.

Anybody been down this road?

[the Ferret]

Beardy I have heard for years that the alt starts putting energy back into the battery at 2500 pms. If that is actually true, I can't say, but I assume there is some point where it happens. If you are using 2 sets of electrics and charging a phone at the same time, it may require a lot of rpms to resupply lol

[LongRanger_imp]

The amperage draw of your electric gear (x2!) simply exceeded the alternator's capacity, leading to battery discharge. It even happens on BMW's with 600 Ah alternators (I'll bet the CB's is about half that size).

[the Ferret]

I think I read output is 336W somewhere.

[beardyweirdy@me.com_imp]

No doubt!! I accept that and half expected a bit of battery trouble...

After it failed I ran a gear lower to keep the revs up. Battery recharged and all was fine. I'd say that it's a given that at low RPM the alt won't be making as much current as it is when its spinning faster. The output in the manual is mesured at 5k, so I'm guessing that's peak and less than that below.

With a low reving bike like the CB it won't be getting much peak power and I'll bet some bikes on the forum hardly ever see 5k.

It might be easier just to run the bike in a lower gear, on the odd occasion I'm running all the heating and keep the revs up.
216w and 18amps for the clothes
+ phone charger ??
+ lights and bike power étal
Definitely running close to the edge at peak...
I need more power!!! Always the way...

[kmoney_imp]

Swapping to an LED headlight is an easy way to free up some wattage. Not a real solution, but gives you some overhead.

[LongRanger_imp]

Unless bikes are designed to support the use of high-draw accessories (vests, jackets, gloves, lights, etc.), I've noticed that alternators generally have sufficient capacity to maintain the battery and operate the ECU, fuel injection and ABS, but really not much else, at least not for an extended period. On my K1200RS, which has a huge alternator, simply using an electric vest (85W) with the heated grips on their highest setting and the headlight on high beam is enough to discharge the battery in short order. The police version of BMW bikes have a second battery to support the flashing lights, strobes, sirens, radio, etc.

[curlyjoe_imp]

I think I read output is 336W somewhere.

Yes, according to the '13 service manual, the capacity of the alternator is 336 watts at 5000 rpm.

[curlyjoe_imp]

[url=http://www.yuasabatteries.com/faqs.php?action=1&id=30]Testing a 12 volt battery and charging system with a voltmeter.

The last test is to read voltage while the engine is running at various RPMs and voltage should read between 13.8 and 14.5. It might be a good idea to turn on all the accessories too and monitor voltage while running at RPM range you typically ride at.

[Cormanus]

Good link. Thanks curlyjoe.