Thanks to Ken Glass for his great article on how to repair Trend Airshield batteries on the cheap. I've used that to fix two of my three batteries. But while doing so I realized that I had now killed 4 very expensive Trend batteries by leaving the Airshield plugged in too long. This makes me think that the charging circuit in the helmet is pretty stupid. Combine that with wanting to charge one battery while using another and it got me going on a quick little project.
First I bought one of these Universal Smart Chargers for 2.4 - 7.2v NiMH/NiCd batteries:
from here: http://www.batteryjunction.com/unsmchfornib.html ($23)
Then I roughly (very roughly) threw together a quick holder for the Trend battery:
Which is just scrap wood glued together with a couple of pieces of wire going through two holes in back (strengthened with epoxy) and then down into two holes in the bottom and tinned:
The battery charger connects to the base using the clips that are included with the charger:
And then you set the battery into the base and plug it in.
Now you have a charger that stops charging when the battery is full AND you can charge one battery while using the other. It isn't fast (about 6 hours) but it works and the packs don't die if you forget to unplug them.
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Originally Posted by Mark Levitski
