Recharging battery while idle

Afan

Afan

... and this is my real name.
Joined
Jun 2, 2014
Messages
521
Location
Urbandale, IA
Bike
1998 ST1100
STOC #
8832
On this website http://www.st-1100.com/st1100-battery.html I found a statement
"... By the way, the ST1100 alternator will only start charging the battery once the rpm exceeds 2000... "
Really?!? So, "idleing" my bike every 2-3 days to recharge the battery didn't do anything?!?
:(
 
I will not speak to the absolute factual basis of the 2000 rpm before charging occurs but it may be a waste of gas to let the bike idle thinking it will charge the battery to any significant degree. The real test is to put a voltmeter on the battery before and after your bike idle period of time. I expect you will find little change other than the liquid molecules heated up and you get some reactive voltage from the heating. Check the voltage again after the bike has cooled down and I expect you may find your voltage reading the same or maybe slightly less than before you started the idle.
Depending on the condition of your battery, starting the bike takes a certain amount of volts and amps. That will draw the battery down some and the recovery is not likely to happen very quickly at idle, if at all. The lights and ABS (if ABS is on the bike) take a certain amount of power and the bike at idle is maybe supplying enough power for those items at most. I expect others more knowledgeable about the specifics of the ST1100 alternator and output range can comment.
 
A lot of variables to try and make that determination. Best bet is to measure voltage. If you are above 13v you are charging the battery.

But on another note, you shouldn't need to run the bike that frequently if just keeping the battery topped off.
 
Get a battery tender to keep your battery maintained, quit wasting gas and fouling the plugs by letting it idle for an extended period of time. It wouldn't surprise me if the 2000 rpm stated in your original post is correct. I remember the procedure described in the shop manual for my GS850 specified checking the charging system with the bike running at 5000 rpm with no electrical load. If I remember correctly, I had to remove the headlight fuse when checking the alternator output. I don't recall what the procedure is for checking the alternator on the ST1300, it's been a while since I've done it.
 
Don B said:
Get a battery tender to keep your battery maintained, quit wasting gas and fouling the plugs by letting it idle for an extended period of time
Click to expand...
Working on it just now. :)
Thanks.
 
Agree with all the above. Even a cage battery won't be charged significantly at idle. I remember a few times being told that to charge up a cage battery go for a trip on the highway for about 20 miles or more. If the bike battery is too low to start the engine until letting go of the starter button then the battery is not holding much of a charge or there is some constant drain somewhere. Based on our earlier conversation offline I would say battery replacement is due real soon. But to get it to where it will start the bike it is best to put a battery maintainer on it like the Battery Tender or some other maintainer that runs a multistage charging routine. IOW- not just a trickle charger block. A maintainer is really good to have anyway. I have both the charger to bring up a totally dead battery and a maintainer for keeping a battery in top shape through months of non-use. A maintainer also can be connected and left connected to a battery without issue... unlike a simple charger that would cook the battery if left connected.
 
rjs987 said:
...to charge up a cage battery go for a trip on the highway for about 20 miles or more...
Click to expand...
Isn't that more in the > 4 hours region?
IMHO would 20 miles only bring charge for 1 maybe 2 cranks... varying with the operated electrical parasites, headlights, high beams, heated handles, etc...
 
I remember reading about the amps it takes to start the bike and roughly 20 minutes of driving the bike to put the battery where it was on the volts/amp scale before it was started.
Also starting your bike sporadically in the winter lets cold moist air in the crankcase and mixing it with the oil.
I feel it does more harm than good.
A good sign of moisture in your oil is milky oil inside the valve covers.
 
I guess that could be a few hours ride/drive rather than just 20 minutes. It really depends how high you keep the rpm during the ride. I just wouldn't like it as much in a cage as on the bike. :)
 
Ditto on many motorcycles will not charge at idle. I think that scenario mostly occurs on the bikes with primitive charging circuits - permanent magnet armature spinning in the stator with a regulator/ rectifier shorting excess current to ground. That's the system on my 2007 Aero and with the factory voltage regulator, it would not charge at idle and the lights got dimmer when stopped. I found a common mod for those bikes is to replace the factory SCR based regulator/ rectifier with a MOSFET unit. I did that and it does indeed make a great improvement and now my Aero charges fine at idle. :) Here's a video I made after the upfit.

https://www.youtube.com/watch?v=82bdvdwr60E

I suspect bikes like the STs which have rotating EM field alternators and proper voltage regulators already do a sufficient job. I know my ST1300 does charge fine at idle (13.6 -13.8V, at 87F) but it is stock with no additional draws. That said, no doubt even on the ST, it would take longer at idle to replace the charge depleted by a start cycle than it would take at higher revs.
 
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