We’ve seen a lot of discussion about single pack layouts vs. dual pack layouts. We researched both and concluded without any doubt that a single pack provides the best path to a perfectly balanced vehicle.
Dual Pack Layout: Yes, the batteries on a dual pack layout are balanced, but only with each other. Up front on the left side you have the motor (340-400g). On the right side you have a servo, receiver, and an ESC. All of those together add up to ~165g. That’s a 175-235g discrepancy. That’s a 6.25 – 8.4 ounce difference. That will definitely have consequences on the track. Sometimes the ESC is placed atop the center diff or behind the center diff above the batteries. This throws off the balance even further by lightening the right side more and negates the COG benefit of a dual pack layout. Additionally, dual pack layouts have too much weight in the back of the vehicle resulting in sluggish on-power performance and reduced corner speed. Dual packs are cumbersome – you have to change two packs, charge two packs, wire two packs, etc. They are heavier than single packs (of the same capacity) and don’t always discharge evenly the way a single pack would since they are charged separately. There is no option for mechanical brakes or the Traktion Drive / Elektri-Clutch slipper systems.
Single pack is the way to go!
Single Pack Layout: While a single pack layout doesn’t LOOK as balanced, it is actually much better balanced than a dual pack layout. On the battery side you have only the battery (450-600g). There are a lot of newer lightweight 4s packs available now. For example, ProTek RC makes a killer 4s/4100mah/70C pack that weighs ~480g. There are also lighter 4s packs available. But back to the point, the battery is balanced by the motor, servo, ESC, and RX on the other side (505g). The difference in this case is about 25g – less than an ounce! You could very easily choose a motor and battery setup that would be even closer. Wiring is simplified, battery changes are easier, charging is easier, and the single pack is going to discharge more uniformly than 2 separately charged packs. The car is lighter as a result of less wire and only one battery case.
If you want to run mechanical brakes, no problem. Just choose a lighter battery or a heavier motor to get the balance right. In the pictures below you can see how well balanced the EB48 really is. In the first pic, the front-right wheel is 30g heavier than the left. In the second pic, the rear-left is 10g heavier than the right. A net difference of 20g. NOTE: we tried to get a single pic with all 4 scales visible, but it would not focus correctly, but these are the real measurements, we have nothing to hide :).
According to the pictures above we have the following:
RIGHT SIDE: 1679.5g (50.3%)
LEFT SIDE: 1659.2 (49.7%)
FRONT: 1609.3g (48.2%)
REAR: 1729.4g (51.8%)
TOTAL: 3338.7g (no body)
Equipment used: Tekin 2050kv T8, Castle MMP, Airtronics MT4 receiver, capacitor, Venom 4s/5000/50C.
More explanation: Where the weight is located on the chassis obviously matters. The pack in the pics is ~590g, but it is so close to the center line of the chassis that it has less of an effect than the motor does on the overall weight balance. The motor is just a few millimeters further off center. This is why the car is balanced with a heavier pack and a lighter overall right side. In dual pack layouts, we’ve seen the motor is further from the center than on the EB48. This has the effect of making the motor side even heavier (more out of balance).
Conclusion: We hope this clears up some of the misconceptions about the balance of dual pack layouts. We don’t know for sure, but we can almost guarantee that we’ve spent more hours on 1/8th Electric R&D than any other company in RC. Superior weight balance of a single pack layout is one of the things we’ve learned (and tested) over the years. The EB48 represents what we believe to be the optimal layout for this class.
Stay tuned for more articles.
p.s. Another quick note about a single pack layout – Lightweight setups are easily achieved by using a single 2s lipo battery and a smaller Pro4 motor. On a dual pack layout, if you wanted to configure with a single 2s lipo, the car would once again be out of balance. So the single pack layout is also very versatile.