I have a few projects, I would like to run off 18650 batteries that will be recharging from a 12-volt battery system in my truck and motorcycle.
One, in particular is a digital horn. I'll run Arduino plugged into an little amplifier module, df-mini mp3 player to play fun HORN noises to remind drivers ahead of me that the light has turned red (for example).
I would like to run these projects from 18650 batteries, so they are nice clean power. I do not have a problem converting voltage down to 5v, I do not need help with that.
I was looking for rechargeable modules I can buy, to hook up the 18650 cell packs into 12v to constantly recharge from the main vehicle voltage, and output power to my projects. This is mainly since I want clean nice voltage without hearing engine RPM noise through the speakers, spikes or otherwise dirty power from alternator or whatever else is going on.
Can anyone give me some links, I can buy eBay, amazon or somewhere - they work, do what I need ? Or any other advice would be appreciated. Thank you.