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Started with LiMn (Bosch 36V tool batteries). Reliable but a bit heavy and bulky. Still great for the tools Evolved to very many Zippy LiPos, not always the best cared for. Very portable and constantly improving in capacity and lower prices. Like the US warehouses HobbyKing now stocks regularly.
Year-old SLA are still going strong, 2500 miles, 250 cycles; available funds will determine replacement chemistry, I am fine going with SLA again. Easily recycled, ease of use and charging, rugged, predictable, safe, and cheap! (I am an analog person in a digital world)