I still have the standard battery on my bike and a little while ago was having cold starting problems, even though I was keeping charge topped up with trickle charger. I was relaying my starting woes to a friend who for many years was in the electronics business but in retirement now tinkers with classic bikes. He didn't want to recommend a battery but offered the following advice:
All batteries are poor at conducting large amounts of charge when cold as they are designed to be at there most efficient when they are warm, and this may be as little as just a few degrees higher than the ambient temperature. So trying to draw full power from a battery when it is cold (especially when it has been left for a while) is going to be a shock and the battery will be sluggish.
With all his bikes (&scars) over many years experience he always puts some a small load on the battery first to encourage it to warm up, like putting the lights on for a few seconds to draw a current through the battery so the cells warm, he will then turn them off before cranking the starter over. He told me he has never failed to get sufficient charge to crank a bike over, even when a battery isn't at its best. To be honest I was somewhat dubious, as I have always been of the option that you never put any extra loads on a battery before cranking the starter so you have the fullest charge possible?
But I thought I'd give it a go and it worked, I purposely didn't put my battery on the charger for a week, knowing that it wouldn't be at its best, turned the ignition on, turned the lights on, did up my helmet, turned the lights off and hey presto bike turned over as if it was freshly charged!
On reflection there must be something in this as I have a car with auto lights and it always starts better in the dark when the lights come on first!
Not sure if this helps anyone, but it is something that seems to have worked for me and could save me replacing my battery in the immediate future.