Motorcycle's VRLA lead acid battery shows 15.5 volts!

Hi,
A motorcycle's self-starter was not working sometimes and was working very well sometimes. I thought the battery started to damage. Or going through deep discharge. It is unusual that sometimes after driving approx 5KM, the seft-starter does not work (just makes a sound like a low voltage battery trying to start a starter motor); and sometimes works well even a first try after hours of inactivity of the motorcycle. Today I tested its voltage (Open voltage) and it was 14.8V. After an hour, tested again and now getting 15.5V? The voltage is rising itself. Now added 300mA load and tested, it is still 15.4V! Is it usual? It has already 15.5V then what would be its charging voltage?

Do I have to replace the battery or the problem is with the starter motor etc?

If it won't start it then it probably needs replacing. Was it discharged for any length of time?

Mike.

Pommie said:

Was it discharged for any length of time?

Mike.

Click to expand...

The motorcycle was normally travelling 20km a day. The battery is in 2 years of service.

It does sound as if the battery has failed. unfortunately.

As suggested, quite possibly the battery has failed - certainly motorbikes very often have really poor electrical systems, particularly as far as charging and regulation is concerned. Smaller bikes tend to be exceptionally poor, but you don't give any idea as to size, make or model - all of which could make a difference.

Was the motorbike regulator originally made for VRLA/SLA or a flooded acid battery? It looks to me like a regulator mismatch or failure (Overvoltage) and battery failure (premature failure. SLA's also need temperature-compensated charge voltages. FYI https://www.sealedperformance.com.a...2015/09/1277751263_20100627-TechManual-Lo.pdf

All batteries have a double-layer charge effect that results in a memory voltage with a fast response and a slow response time constant. Some more than others.