Newegg has the Battery Tender Jr. #021-0123 12V Battery Charger (Newegg) – $20.99 after $5 coupon code BT0216 (exp. 6/30). Free expedited shipping (3-5 days).
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FP (+47) @ same price on 4/21/18.
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$25+ @ Amazon WM, etc. Google Shopping search link here .
"The Battery Tender® Jr. offers much more than a trickle charger could offer. It has a brain. It’s lightweight, compact, and fully automatic; very easy to use, especially in small spaces. It will keep your battery fully charged so that it is ready to go when you are!"
– Perfect for all lead-acid, flooded or sealed maintenance free batteries (AGM and gel cell).
-Complete 4-step charging program (Initialization, Bulk Charge, Absorption Mode, Float Mode).
-Automatically switches to float / maintenance voltage after fully charging the battery.
-If the battery voltage drops too far under load, full charger output power resumes.
-Solid state two color LED indicates stage of charger.
-Spark proof.
-Reverse polarity protected.
-12′ output cord.
-5 year warranty