PowerMaster Battery Junction (PBJ) Board Overview/User Guide
Thank you for purchasing the NoBS Batteries PowerMaster Battery Junction board! This small ‘Battery Hub’ removes and replaces all of the high impedance components and connections in your aircrafts primary battery system. This eliminates RC system switches, 18-22g battery & extension cabling and all those astonishingly high-impedance FJ/JRUniv connectors.. with one simple junction board. You will need ONE PBJ for EACH battery pack you put onboard your aircraft.
Overview
When I started this company 25 years ago I never envisioned that privately-owned radio-controlled model aircraft would get quite so large. 1/3rd Scale and ½ Scale models are now as common as our 1/5 & ¼ Scale models of the 1980’s & 90’s. With this massive increase in size and weight comes greatly increased current demands on your battery system. Further, with the advent of lithium-based battery systems we are seeing more and larger battery packs commonly replacing the ‘A’ and Cub-C sized nickel cadmium & nickel metal hydride battery packs that were favored for Giant Scale Rx, Ignition, ECU’s & servo applications 20 years ago. We were very proud to introduce A123 LiFe battery systems to the RC community back in 2006. They’ve performed magnificently for two decades now as a primary source power for Giant Scale RC and they continue to do so today. They certainly proved themselves up to the task of dealing with the demands of what was formally the norm of Giant Scale operations… but these new, even larger & heavier birds have completely out-grown the ‘old standards’. Commonly used RC system plugs and connectors (Fj/JRUniv, etc) and their accompanying 22-20g Chargeport Slide Switches simply are not up to the loading and current demands on the primary power legs of today’s 1/3 scale & larger projects. These massive aircraft have also exposed the inadequacies in our support equipment, presenting challenges with regards to Battery Access, Removal, Storage & Fast Field Charging. Todays ‘Smart’ Radio gear, Power Expander Boards and Power Hubs like Futaba’s DLPH - and any system employing ‘Digital Switches’ - demand a battery system configuration that can meet their significant current demands and overcome their unique shortcomings.
Common Issues with Very Large Radio Controlled Aircraft (VLRCA’s)
near to or over 55 Pounds
• High Power System Impedance producing ‘Brown Out’ type failures during moments of maximum servo or accessory loading.. sudden flap deployments, electric landing gear jammed, stalled servo, etc.
• Constant Current Drain issues depleting (and wrecking) packs left connected to the radio gear usually caused by difficulty in accessing the packs primary or charge connector.
• Cell Checks/Balance Charging in Plane. the inability to quicky and easily check cell balance and state of charge – if you can’t quickly and easily check your packs.. you likely won’t do it routinely.
• REAL Fast Field Charging .. if your pack is cabled with 18-20g cabling with standard system connectors (Fj/JRUniv) your charge rate is strictly limited to what those connectors can ‘handle’.. push more than 3 amps continuous thru them - you will melt the plugs.
• Inappropriate Cabling and Connectors & Switches.. If your bird’s servo loading outstrips the 3 amp current limitations of the FJ/JRUniversal connectors present in your normal R/C system standard configuration batteries & switches in flight.. the results are usually an unsightly divot in the field with small parts of your project scattered around it.
• ‘Common Ground’ issues. This is an annoying intermittent issue that confuses the charger and creates faults, forcing you to charge the packs one-at-a-time and at rates less than 2.5 amps
Lets look at these in order…
1st; ‘Impedance’ aka ‘Resistance’. It’s the ‘baseline’ to check when we’re concerned about the effects of voltage-drop when loads are applied. It’s like a golf score; the lower the number, the better. We’ll use our own A123 2500 ‘Combo’ pack with 20g Combo Cabling running thru our ‘Combo Switch’ as the ‘baseline’. This configuration checks in with 125mOhms resistance. The pack by itself, no switch.. 71mOhms. This is not an issue in most 1/5 scale warbirds or ¼ scale WW1 type projects, this setup as a Parallel Pack system has been doing the job without issue for decades. However, when the project becomes massive.. so do the current demands. Let’s compare the above system with our new PowerMaster line of packs.. For this application we build the pack with doubled ¼” wide nickel straps, 16 welds per cell, per side. Then we cabled it w/14g wire and low-loss plugs (XT-60/IC3/Deans, etc). The new PowerMaster 2600 pack BY ITSELF reads 15mOhms. Taking it further, we then designed the PBJ for minimum losses with ¼” wide copper traces & used XT-60’s for power delivery. The PBJ adds just 4 mOhms. Yes; FOUR mOhms to the battery system impedance. The whole PowerMaster System, “Soup to Nuts” is just 19mOhms. Compared to 125mOhms resistance in a ‘normal’ RC battery system. Impedance Issues… SOLVED
Next; Constant Current Drain. This one is insidious... for two decades now, the biggest killer of Lithium Systems is ‘run-flat’. Over-discharging the packs just wrecks them. If you install our PBJ where you can quickly & easily see and reach it inside the aircraft then you can just as quickly disconnect the battery from ALL devices. You can do it one-handed. Eyes closed. And KNOW your system is OFF. Completely and totally OFF. No ‘Switch’ required... YOU are the ‘switch’. Constant Current Drain Issues: SOLVED! State of Charge & Cell Checks. The PBJ enables one-handed FAST checks with your Checker via the small fixed ‘Univ Charge Port’ right in the middle of the PBJ. Easy to see, easy to reach means you WILL check it before you fly because you CAN easily check it. One-handed… but we recommend you open your eyes for the actual ‘cell check’ part. We even build a ‘Checker’ Harness that’ll make our favorite Checkers much more useful. Count this one as ‘Solved’ as well. Fast Field Charging that's NOT Fast! We’ve built our entire PowerMaster System around moving current where it needs to go QUICKLY. An A123 pack, charged at 10amps continuous will get slightly warm to the touch towards the end of the charge. So, that’s your maximum Fast-Charge rate. It’s a heck of a lot better than the 3amp rate limit imposed by those goofly little JR/FJ type connectors. In keeping with that, our custom configured PowerMaster charger cabling is 14g from front to back. And, we built it as a ‘single lead’ balance charge cord, very much like our original ‘Combo Charger Cord’ for the smaller birds. A half-depleted pair of 2600 packs can be both charged at the same time at 10 amps; takes under 10 minutes. Finally, the word ‘Fast’ is actually FAST in the often used but not very often realized monicker “Fast Field Charging”. This one I’ve been wanting to solve for some time… and now it is!
Common Ground Issues. Multi-Port Chargers are very prolific and popular these days.. unfortunately, when run at high output current, charging two packs at the same time in the plane with most of them would often trigger a charger ‘fault’ of one kind or another, constantly forcing you back to the charger to reset and re-enable the charge routine. Common ground issues are often encountered between 2 slide switches that don’t disconnect ground or signal and/or 2 Rx’s or the PE (Power Expander) being in the ‘field of view’ of the charger when charging via a switch chargeport. The PowerMaster System eliminates the switch and isolates the Rx’s and the power expander from the view of the charger. To Fast Field charge your packs via the PBJ you COMPLETELY DISCONNECT the PBJ’s output by simply unplugging the PE (Power Expander) supply cable from the PBJ in order to charge… because THAT’s the port on the PBJ you use to charge thru! For our EXTENSIVE testing routines we’ve focused on Hitec’s latest RDX2/200w charger. Run from a 12 volt source, charging two packs at the same time via both ports at 10 amps. Over the course of 50+ cycles, charging both packs in the plane at the same time… not a single fault. I’ll have to wait and see tho.. there’s a lot of chargers out there, but I suspect that this issue is largely SOLVED as well.
1st; ‘Impedance’ aka ‘Resistance’. It’s the ‘baseline’ to check when we’re concerned about the effects of voltage-drop when loads are applied. It’s like a golf score; the lower the number, the better. We’ll use our own A123 2500 ‘Combo’ pack with 20g Combo Cabling running thru our ‘Combo Switch’ as the ‘baseline’. This configuration checks in with 125mOhms resistance. The pack by itself, no switch.. 71mOhms. This is not an issue in most 1/5 scale warbirds or ¼ scale WW1 type projects, this setup as a Parallel Pack system has been doing the job without issue for decades. However, when the project becomes massive.. so do the current demands. Let’s compare the above system with our new PowerMaster line of packs.. For this application we build the pack with doubled ¼” wide nickel straps, 16 welds per cell, per side. Then we cabled it w/14g wire and low-loss plugs (XT-60/IC3/Deans, etc). The new PowerMaster 2600 pack BY ITSELF reads 15mOhms. Taking it further, we then designed the PBJ for minimum losses with ¼” wide copper traces & used XT-60’s for power delivery. The PBJ adds just 4 mOhms. Yes; FOUR mOhms to the battery system impedance. The whole PowerMaster System, “Soup to Nuts” is just 19mOhms. Compared to 125mOhms resistance in a ‘normal’ RC battery system. Impedance Issues… SOLVED
Next; Constant Current Drain. This one is insidious... for two decades now, the biggest killer of Lithium Systems is ‘run-flat’. Over-discharging the packs just wrecks them. If you install our PBJ where you can quickly & easily see and reach it inside the aircraft then you can just as quickly disconnect the battery from ALL devices. You can do it one-handed. Eyes closed. And KNOW your system is OFF. Completely and totally OFF. No ‘Switch’ required... YOU are the ‘switch’. Constant Current Drain Issues: SOLVED! State of Charge & Cell Checks. The PBJ enables one-handed FAST checks with your Checker via the small fixed ‘Univ Charge Port’ right in the middle of the PBJ. Easy to see, easy to reach means you WILL check it before you fly because you CAN easily check it. One-handed… but we recommend you open your eyes for the actual ‘cell check’ part. We even build a ‘Checker’ Harness that’ll make our favorite Checkers much more useful. Count this one as ‘Solved’ as well. Fast Field Charging that's NOT Fast! We’ve built our entire PowerMaster System around moving current where it needs to go QUICKLY. An A123 pack, charged at 10amps continuous will get slightly warm to the touch towards the end of the charge. So, that’s your maximum Fast-Charge rate. It’s a heck of a lot better than the 3amp rate limit imposed by those goofly little JR/FJ type connectors. In keeping with that, our custom configured PowerMaster charger cabling is 14g from front to back. And, we built it as a ‘single lead’ balance charge cord, very much like our original ‘Combo Charger Cord’ for the smaller birds. A half-depleted pair of 2600 packs can be both charged at the same time at 10 amps; takes under 10 minutes. Finally, the word ‘Fast’ is actually FAST in the often used but not very often realized monicker “Fast Field Charging”. This one I’ve been wanting to solve for some time… and now it is!
Common Ground Issues. Multi-Port Chargers are very prolific and popular these days.. unfortunately, when run at high output current, charging two packs at the same time in the plane with most of them would often trigger a charger ‘fault’ of one kind or another, constantly forcing you back to the charger to reset and re-enable the charge routine. Common ground issues are often encountered between 2 slide switches that don’t disconnect ground or signal and/or 2 Rx’s or the PE (Power Expander) being in the ‘field of view’ of the charger when charging via a switch chargeport. The PowerMaster System eliminates the switch and isolates the Rx’s and the power expander from the view of the charger. To Fast Field charge your packs via the PBJ you COMPLETELY DISCONNECT the PBJ’s output by simply unplugging the PE (Power Expander) supply cable from the PBJ in order to charge… because THAT’s the port on the PBJ you use to charge thru! For our EXTENSIVE testing routines we’ve focused on Hitec’s latest RDX2/200w charger. Run from a 12 volt source, charging two packs at the same time via both ports at 10 amps. Over the course of 50+ cycles, charging both packs in the plane at the same time… not a single fault. I’ll have to wait and see tho.. there’s a lot of chargers out there, but I suspect that this issue is largely SOLVED as well.
System Installation Considerations & Priorities
• First & Formost!! As in real estate, the key is Location, Location, Location… your battery system breaks down into three components. Your packs, your PBJ and your ‘Load’ (Power Expander, DLPH, etc). To get the most out of your battery system you will need to prioritize the PBJ’s location; it should be the 1st thing ‘laid out’ on your project. Place it where you can reach it quickly and easily… it is going to be your ‘Master Disconnect’ & primary power connection and in-plane cell check and charging hub. Hiding it defeats its prime function. Put it where you can quickly lay your hand on it, preferably in plain view. When scale detailing in your cockpit becomes the obstacle to placement, set it up under a folding or magnetic seat or removeable ‘floorboard’ that lifts away. The mount surface should be strong enough to support the ‘wiggling’ of high current plugs in & out of their ports.
•
• Next, the Batteries. Depending on whose packs you are using, weight is just not the prime consideration for placement in VLRCA’s (Very Large RC Aircraft). In a 50 POUND aircraft (800 ounces) a pair of 8 ounce batteries (NoBS 2500ma A123’s) just do not present themselves as the serious ‘weight factor/CG modifier’ that they would be in a 1/5 scale project. For you incessant and obsessive weight watchers, consider this: The long leads create additional voltage drop & increase system impedance. Worse: 3 feet of 14g wire weighs more than the damn battery! Lastly; DON’T build the packs into a ‘field’ inaccessible location. If you need to spend 45 minutes removing a windshield and dashboard to just to get at an underperforming pack then you have certainly put them in the wrong place😊
•
• The ‘Load’: Your Power Expander & Rx’s. This is your ‘Radio Room’… it’s where your DLPH or Power Expander, your Rx’s and Telemetry gear would be located. Accessibility for this gear is not quite as crucial as the PBJ’s placement, most of the stuff in this area, if it needs attention, would be accessed when the plane is in some state of ‘teardown’ (wings off or fuselage upside & down in a cradle, etc.).
Installation Options - Flush Mount -OR- Surface Mount
The PBJ is 2.5” square and can be “Flush Mounted” or “Surface Mounted”. For the ‘Flush” installation you’ll need a 2 ¼” hole saw to provide the hole for the majority of the PBJ’s cabling and circuitry along with a ‘drum rasp’ to mill out the ‘ear’ where the 22g balance plugs exit. (Hint: run the hole saw in reverse, at low speed to keep from getting a ragged hole in light ply surfaces). We provide the PBJ with a LitePly hole template & spacer plate so the input and output ports of the PBJ stand slightly ‘proud’ on the mounting surface. Use standard servo screws to lock it down. Currently included with your PBJ is a ‘Surface Mount’ kit (that's the two birch ply blocks in your PBJ package) that allows you to install it standing about ¾” above the mount surface. No messy hole hacking and Dremel shredding required 😉 PBJ Limitations: This version is limited to 2S Lithium (LiPo, LiFe, LiIon & LiHV) packs.. although you’d be able to connect a 3S or 4S pack, you’d not be able to check or balance charge the individual cells. We’ve tested the PBJ at 35 amps continuous on a 4S LiPo pack without significant heat buildup on the PBJ board.. the 14g cabling and Anderson connectors in the test rig showed slightly MORE temp increase than the board.
Typical Usage • Cell Check Port The Small port in the middle of the PBJ is your spot to plug in your Cell Checker. It’s there in the middle so you can find it by touch. It’s where you’d plug in your Checker’s FJ/JR Univ Female to JST-XH adapter cable to eyeball your packs individual cell voltages and the packs resting state of charge. • Master Disconnect & Charge Port This is the PBJ’s yellow XT-60 bulkhead plug socket. The PBJ ships standard with your choice of 14g Extension cable with a matching XT-60 male to whatever plug your Power Expander uses. Here’s where it’s rational to fiddle with lengths if need be. What ships as ‘standard’ with the PBJ is a 12” long 14g XT-60 Extension. Optional lengths and ‘load side’ connectors to mate with your P.E. Board are available. We also have available a ‘PowerMaster Field Charge Combo Cable’. It’s @ 3ft long, 14g and permits you to do SINGLE CABLE high-rate field & balance charging with.. it plugs into the same ports. • BATTERY IN - XT-60i This is the ‘orange’ pack input port. It’s got the same ‘footprint’ that a standard yellow XT-60 pack-side plug needs with one little addition… a ‘third’ contact. This allows us to build the pack with a single ‘Combo Lead’, eliminating a separate balance lead and permits in-plane balance charging and Fast charging. • The 22g Female lead and the JST-XH Female lead These are there because I feel the PBJ is too important as a must have device to make it ‘exclusively’ for our packs alone. The folks that need to (or elect to) use the PBJ with our ‘conventionally cabled’ A123 packs -OR- with common LiPoly packs. These may have either a JR/Univ male balance lead or a JST-XH balance lead and a separate 16/14/12g power lead. The orange plug on the PBJ is compatible with a conventional yellow XT-60 pack side plug. Those two ‘dangling’ leads (FJ/JRUniv & JST-XH) are there so ANY pack can be used on the PBJ as well. A 2 cell LiPoly w/XT-60 power plug is easily compatible with the orange XT-60i on the PBJ. You’d connect the LiPo’s JST-XH plug into our dangling JST-XH Female and the PBJ becomes fully compatible with anybody’s 2s LiPo’s… with all the advantages enjoyed when using the PBJ with our PowerMaster Series 6.6v A123 packs.
IN CLOSING..
Whats Next: We’ve got a Master Disconnect board in development that’s the same physical dimensions as our A123 Combo Switch body. It’ll be an excellent way to quickly upgrade an existing 1/4-1/3 scale project, eliminating all the FJ/JR Univ connectors in the Power Leg of an existing A123 Combo install. It won’t have quite the current handling capability as the above PBJ but it will be a good pick for birds between 25-50 pounds. We should have it ready for y’all by March. This will likely be the last project that Gunny & I as a team will get to introduce to you folks that ‘Fly Big & Bold’… I’m in my mid-70’s now & slowing down a bit & expect to ‘hang up my spurs’ soon. So, I encourage y’all to toss a ‘Thanks!’ Gunny’s way when you see him.. he gets out a lot more than I do. He is the Principal over at Aviation Concepts RC… & this and just about all the other ‘great idea’s’ I’ve had over the past 3 decades became reality thanks to his unique genius, his beautiful kit designs and the unmatched RC gear & equipment fabrication shops he has built. Thanks, Gunnar. U da Man.
Steve Anthony NoBS Batteries, January 15, 2026 www.hangtimes.com
The PBJ is 2.5” square and can be “Flush Mounted” or “Surface Mounted”. For the ‘Flush” installation you’ll need a 2 ¼” hole saw to provide the hole for the majority of the PBJ’s cabling and circuitry along with a ‘drum rasp’ to mill out the ‘ear’ where the 22g balance plugs exit. (Hint: run the hole saw in reverse, at low speed to keep from getting a ragged hole in light ply surfaces). We provide the PBJ with a LitePly hole template & spacer plate so the input and output ports of the PBJ stand slightly ‘proud’ on the mounting surface. Use standard servo screws to lock it down. Currently included with your PBJ is a ‘Surface Mount’ kit (that's the two birch ply blocks in your PBJ package) that allows you to install it standing about ¾” above the mount surface. No messy hole hacking and Dremel shredding required 😉 PBJ Limitations: This version is limited to 2S Lithium (LiPo, LiFe, LiIon & LiHV) packs.. although you’d be able to connect a 3S or 4S pack, you’d not be able to check or balance charge the individual cells. We’ve tested the PBJ at 35 amps continuous on a 4S LiPo pack without significant heat buildup on the PBJ board.. the 14g cabling and Anderson connectors in the test rig showed slightly MORE temp increase than the board.
Typical Usage • Cell Check Port The Small port in the middle of the PBJ is your spot to plug in your Cell Checker. It’s there in the middle so you can find it by touch. It’s where you’d plug in your Checker’s FJ/JR Univ Female to JST-XH adapter cable to eyeball your packs individual cell voltages and the packs resting state of charge. • Master Disconnect & Charge Port This is the PBJ’s yellow XT-60 bulkhead plug socket. The PBJ ships standard with your choice of 14g Extension cable with a matching XT-60 male to whatever plug your Power Expander uses. Here’s where it’s rational to fiddle with lengths if need be. What ships as ‘standard’ with the PBJ is a 12” long 14g XT-60 Extension. Optional lengths and ‘load side’ connectors to mate with your P.E. Board are available. We also have available a ‘PowerMaster Field Charge Combo Cable’. It’s @ 3ft long, 14g and permits you to do SINGLE CABLE high-rate field & balance charging with.. it plugs into the same ports. • BATTERY IN - XT-60i This is the ‘orange’ pack input port. It’s got the same ‘footprint’ that a standard yellow XT-60 pack-side plug needs with one little addition… a ‘third’ contact. This allows us to build the pack with a single ‘Combo Lead’, eliminating a separate balance lead and permits in-plane balance charging and Fast charging. • The 22g Female lead and the JST-XH Female lead These are there because I feel the PBJ is too important as a must have device to make it ‘exclusively’ for our packs alone. The folks that need to (or elect to) use the PBJ with our ‘conventionally cabled’ A123 packs -OR- with common LiPoly packs. These may have either a JR/Univ male balance lead or a JST-XH balance lead and a separate 16/14/12g power lead. The orange plug on the PBJ is compatible with a conventional yellow XT-60 pack side plug. Those two ‘dangling’ leads (FJ/JRUniv & JST-XH) are there so ANY pack can be used on the PBJ as well. A 2 cell LiPoly w/XT-60 power plug is easily compatible with the orange XT-60i on the PBJ. You’d connect the LiPo’s JST-XH plug into our dangling JST-XH Female and the PBJ becomes fully compatible with anybody’s 2s LiPo’s… with all the advantages enjoyed when using the PBJ with our PowerMaster Series 6.6v A123 packs.
IN CLOSING..
Whats Next: We’ve got a Master Disconnect board in development that’s the same physical dimensions as our A123 Combo Switch body. It’ll be an excellent way to quickly upgrade an existing 1/4-1/3 scale project, eliminating all the FJ/JR Univ connectors in the Power Leg of an existing A123 Combo install. It won’t have quite the current handling capability as the above PBJ but it will be a good pick for birds between 25-50 pounds. We should have it ready for y’all by March. This will likely be the last project that Gunny & I as a team will get to introduce to you folks that ‘Fly Big & Bold’… I’m in my mid-70’s now & slowing down a bit & expect to ‘hang up my spurs’ soon. So, I encourage y’all to toss a ‘Thanks!’ Gunny’s way when you see him.. he gets out a lot more than I do. He is the Principal over at Aviation Concepts RC… & this and just about all the other ‘great idea’s’ I’ve had over the past 3 decades became reality thanks to his unique genius, his beautiful kit designs and the unmatched RC gear & equipment fabrication shops he has built. Thanks, Gunnar. U da Man.
Steve Anthony NoBS Batteries, January 15, 2026 www.hangtimes.com
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