Smaller battery getting hot on 20+ minute rides

No eBay APP ID and/or Cert ID defined in Kunena configurationHello everyone, I recently got my 80 kz650 up and on the road. I went with a smaller battery I purchased off ebay. Model UB1222. Now the stock battery was an 11 amp/hr battery and the one I put in is a 2.2 amp/hr. I am kickstart only, no cluster/dummy lights. Just headlight, front turn signals, and led tail with integrated blinkers.

Ive read on how people are using batteries as small as 1.5 amp/hr and they work just fine. So I figured the 2.2 would work just perfect. Any ideas as to why it gets so warm/hot then?

Here is an ebay link to the battery I bought:

did u change voltage reg ????

Probably your charging system is allowing the voltage to get a little bit too high. This is a common problem if your regualtor has a brown wire to it.

What happens is that your fuse holders get dirty and you lose voltage to your ignition switch. This in turn sends a lowered voltage to the regulator, which senses the battery voltage as being low even when it is not. So the regulator compensates by increasing teh battery voltage. This makes it get hot because it's pumping too much current through the battery.

To fix it, you have to clean the fuse holders and contacts in the path from battery to ignition switch to regulator. This will have a lot to do with the brown wire, which is usually the main switched hot wire in the bike.

The other possibility is that the regulator is bad, but that is a little less common than the voltage-loss issue. It's free to clean connectors, so that should be tried first.

If the wiring is really hashed, then you may need to replace a few wires.

The first thing you should do is measure the voltage on the battery while it's revving with lights on etc. If it's higher than 14.3v or so, you may have too much voltage for a small battery.

Even if the charging system maxes out at 14.3, we may have to drop it a little for such a small battery. (14.3 is an average DC reading, instantaneous voltage may spike as high as 15 or 16v, but won't show up on the meter, which is why I recommend a possible lower voltage.)

Measure the battery voltage in the bike with the engine held at about 3000 RPM. If it is 14V, the reg is working right. If it is above 14.5V, it is overcharging the battery and cooking it.

It's also possible the internal impedance of such a small battery is just too high and the alternator output is causing excessive ripple voltage on it. Most people don't realize the battery also serves as a "filter capacitor" in the system to smooth the DC pulses. If it is too small, too much ripple and that can cause problems.