Recharging whisperer in spring after winter shutdown

I buy a new whisperer every year (on my 4th year now). I also try to charge the old ones each year. I set them in the direct sun. At night I put them under a direct indoor light source. This year they have been charging for a little over 4 weeks now. This gives them enough power to run for 7-10 seconds. As the watering season where I live is only about 4.5 months, this means that every whisperer only lasts me 4.5 months. It's a pretty expensive solution at this rate. 

Is my experience common? Has anyone gotten a whisperer to work after being stored over the winter (and I do charge then fully before turning them off for the winter)?  I assume the internal rechargeable batteries just aren't that good. Has any one had any experience changing the batteries?

Answer From Jacques

37
Jacques
Updated at 2021-05-28 22:24:14 UTC
I've only had my system for two years, but I have 4 whisperers throughout the yard. I've only had to have one replaced, rma throu Netro. I just leave mine in the yard throughout the winter. This keeps them charged, for the most part, and they're ready to go for the following season come spring. 
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3
Ken Wiens
2021-05-30 00:39:45 UTC  
I'm a little reluctant to leave them out in the winter. I'm in Calgary (Canada) and we will get periods of -30C and lots of snow. That's a bit much for most batteries