Just beginning to diagnose mine but I got stalled when my lithium battery went dead......
Thought about putting a car battery in and trying that because once it wouldn't start at work and my wife came to pick me up and she brought the jumper cables. Hooked it up and it started like it was 70degrees outside (instantly)....
REST ASSURED, IF I GET THIS FIGURED OUT, I WILL SHARE IT EVERYWHERE I KNOW SO THAT NOBODY HAS TO GO THROUGH THIS. It's an aching feeling I get when the scoot is down.
Thanks to Stig for starting this up.
Wayne,
I believe you know the answer to your problem. Not enough power from your new battery in cold temps. If it in your words 'started like it was 70degrees outside' while hooked up to jumper cables and the wife's car. It looks like you have discovered it takes more power to start your 500 in cold weather than what your battery is able to putout.
First, I ruled out any thing that has to be plugged in dipstick warmer, any type of warming tape or blanket as not practical.
I have some ideas and they do hit the pocketbook.
You could buy the largest, most powerful Yuasa Battery that will fit. At this point I would only buy from Yuasa themselves. Not Amazon or E-bay just to avoid and chance of knockoffs from china. OR
Buy a Micro-Start small portable jump starter from Antigravity Batteries. Because I have read about these being counterfeited in china and sold on both Amazon and e-bay, I would only buy directly from Antigravity Batteries own website.
On my 500 I had connection for a float charger, I don't remember if you have one too. I would make the same style of connection for the Micro-Start, so that when the need happens you just plug in and start her up.
Yes it is a pain, but then you have the Micro-Start for your cars too.
Either way you're going to spend over $100.