BackPack Sprayer BP-4LiThe BP-4Li is a battery powered backpack sprayer with a 4 gallon tank and a knob that sets working pressure anywhere from 10 to 150 psi. The pump is electric, so the flow rate stays even from the first row to the last - there is no lever to keep working and no pressure fade partway down a bench. Wound up, it atomizes to a fine droplet for foliar coverage of plant growth regulators, insecticides and fungicides; wound down, it lays a coarser, lower drift spray for herbicide and sprenching work. The Makita 18 V 3.0 Ah lithium ion pack slides out and swaps in seconds, and an indicator on the unit reads remaining spray time rather than a bare charge level.There is one build on this page, so the choice that matters is where you set the pressure knob - it decides droplet size and runtime together. On a single charge the unit sprays continuously for 45 minutes in high pressure mode or 120 minutes in medium pressure mode, so backing off the pressure for coarse work more than doubles the time between battery swaps. Two nozzle heads come in the box, a tandem twin fan for banded coverage and a variable cone that runs from a stream to a fine mist, along with a spray lance and the charger. Add a second battery if you need to work past the high pressure window without stopping, since the included charger brings a pack back in 22 minutes.Specifications Tank capacity 4 gallon (15 L) Working pressure 10 to 150 psi, variable by knob Continuous spray time 45 minutes in high pressure mode; 120 minutes in medium pressure mode Battery Makita 18 V 3.0 Ah lithium ion, removable and swappable Recharge time 22 minutes with the included charger Pump Uniflow differential type, DC motor Suction rate 0.39 gal/min (1.5 L/min) Weight 11.7 lb (5.3 kg) empty Dimensions 9.8 in L x 14.6 in W x 22 in H (250 x 370 x 550 mm) Nozzle heads supplied Tandem twin fan head and variable cone head Also supplied Spray lance, battery charger, operator's manual Fuse 10 A Key Features Pressure knob covers 10 to 150 psi, so one sprayer handles fine foliar atomization and coarse herbicide work Electric pump holds an even flow rate for the whole tank - no hand pumping and no pressure fade Makita 18 V 3.0 Ah pack pulls out and swaps in seconds; spare packs are sold separately Included charger refills a pack in 22 minutes, so one spare keeps the unit running continuously Battery indicator reports remaining spray time instead of a generic charge bar Padded back panel and adjustable straps at 11.7 lb empty for full shift wear Priming bubble and tank drain for restarting after idle periods and flushing between chemicals Ideal Applications Spot treatment with plant growth regulators, insecticides and fungicides Herbicide banding along walkways and under benches Sprenching container crops at lower pressure Sanitizer application in propagation and headhouse areas Concentrated applications where wheeling out a cart sprayer is too much equipment Trial and research plots needing repeatable pressure settings Two additional nozzle options are listed separately under BP-4 Backpack Sprayer Nozzles, and the L-5 Extension Lance fits this sprayer when you need reach into a canopy.
