Battery Testing

[Westbeef]

I've been testing my battery/charging system, I just wanted to clarify my results before I go spend my ££.

This morning the bike barely started, it dropped enough power to reset the time and trip, but did fire up. I hadn't left the ignition on, I fired it up right after turning the key.

After my run to work, about 10 miles of motorway -

With the ignition off I was reading about 12.6 volts

With the ignition on and lights on full beam it dropped instantly to 11.77 and trickled down .01 every 5-10 seconds. With the lights on normal it dropped from 12.6 to 12.0

I Started the ignition and it jumped to 14.4 volts at idle and didn't move much when held at 5k rpm.

Does any of this point to a new battery, or Reg/Receiver?

[Joeman]

Battery sounds like it's not holding charge... Reg/rec sounds fine as it's supplying a good voltage.

New battery time IMO.

[Mississippi Bullfrog]

Try charging the battery first. Most people assume that if the battery is flat and you get the engine fired up then after a good long ride the battery will be fully charged. It won't. The old dynamo chargers would charge a flat battery to full capacity, modern charging systems don't. What they do very well is to quickly replace the charge used to fire up the engine, but if you started with a battery at (say) 50% charge the charge replaced will only take it to the same level. So over a time the battery drops from full charge capacity.

Most of the time we don't notice this as using the bike regularly means that the battery has sufficient charge to fire the engine - even if you check the voltage then volts and charge are different things. But if you take most bikes or cars, run them for 200 miles, then put them onto a trickle charger - you will find the charger begins to add charge to the battery. ie it wasn't a full capacity even after a 200 mile trip.

Sorry - bit long winded, but it's amazing how many perfectly good batteries get ditched when all they need is a better maintenance regime. Of course we're told these days that they are maintenance free - but the fact that you don't need to add electrolyte doesn't mean that they don't need a bit of tlc.

14.4 running is fine. 12.6 not running is fine. Dropping below 12v with the lights on suggest the battery is low on charge. If it was knackered the voltage would probably drop further and quicker. Hence I'd give it a trickle charge overnight and then see if it holds the charge.

NB A really flat battery will not take a charge off a trickle charger - if the voltage drops to 11v or lower then it has to be raised back to 12v using a very small current. I use a gell cell charger at 400Ma on really flat batteries. A couple of hours is all they need to build the voltage back to the point where a trickle charger can take over.

[Westbeef]

Try charging the battery first. Most people assume that if the battery is flat and you get the engine fired up then after a good long ride the battery will be fully charged. It won't. The old dynamo chargers would charge a flat battery to full capacity, modern charging systems don't. What they do very well is to quickly replace the charge used to fire up the engine, but if you started with a battery at (say) 50% charge the charge replaced will only take it to the same level. So over a time the battery drops from full charge capacity.

Most of the time we don't notice this as using the bike regularly means that the battery has sufficient charge to fire the engine - even if you check the voltage then volts and charge are different things. But if you take most bikes or cars, run them for 200 miles, then put them onto a trickle charger - you will find the charger begins to add charge to the battery. ie it wasn't a full capacity even after a 200 mile trip.

Sorry - bit long winded, but it's amazing how many perfectly good batteries get ditched when all they need is a better maintenance regime. Of course we're told these days that they are maintenance free - but the fact that you don't need to add electrolyte doesn't mean that they don't need a bit of tlc.

14.4 running is fine. 12.6 not running is fine. Dropping below 12v with the lights on suggest the battery is low on charge. If it was knackered the voltage would probably drop further and quicker. Hence I'd give it a trickle charge overnight and then see if it holds the charge.

NB A really flat battery will not take a charge off a trickle charger - if the voltage drops to 11v or lower then it has to be raised back to 12v using a very small current. I use a gell cell charger at 400Ma on really flat batteries. A couple of hours is all they need to build the voltage back to the point where a trickle charger can take over.

 

I have tried the trickle charge and it still plays up! Soon as I stuck it on the trickle it said 12.6v and just went onto maintain. Ill invest in a new one then

[Joeman]

NB A really flat battery will not take a charge off a trickle charger - if the voltage drops to 11v or lower then it has to be raised back to 12v using a very small current. I use a gell cell charger at 400Ma on really flat batteries. A couple of hours is all they need to build the voltage back to the point where a trickle charger can take over.

Most trickle chargers have reverse polarity protection. if the battery is really flat the voltage isn't high enough for the charger to correctly identify​ the polarity so it won't start charging.

That's why your gel cell charger is helping as it will just charge regardless of polarity getting the battery upto a voltage high enough for the trickle charger to work.

You can trick trickle chargers by putting another battery in parallel just long enough for the charge process to start after which it won't bother checking polarity again.