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VXR Racing LiPo Receiver Pack (LRX-211300) (22/05/2006)
- By:
- Glenn M. Cauley
The Future is Now
One of the reasons we (okay… I) got into this great sport is that we are fascinated and enamoured with high-performance, technological products. As RC cars have continued to evolve into their present-day state of “engineering marvels,” so too have all the supporting products created by innovative companies.
Case in point…
VXR Racing is one of the leaders in RC-focused Lithium Polymer (LiPo) technology, offering leading-edge products to the RC industry. Much to my delight, and surely for other 1/8 on-road nitro car racers around the world, their latest product is a brand-new LiPo receiver pack that was designed to fit the Serpent 960 race car (and others).
For more information, check out the VXR Racing Web site at www.vxrracing.com.
Just the Facts, Ma’am…
Here are some of the specs on VXR Racing’s new LRX 211300 LiPo Receiver Pack:
• Cells: High-capacity, high-performance lithium polymer cells
• Configuration: 2S1P (2 cells in series, 1 parallel path)
• Voltage: 7.4V nominal / 8.4V fully charged
• Capacity: 1300mAh
• Size (mm): 83L x 28W x 13H
• Mass: 61g
Previously, the LRX-211000 pack was the logical choice of LiPo receiver pack for the S960, with 1000mAh capacity and more squarish (shorter, wider) dimensions. The release of the new LRX-211300 saw a pack with increased capacity (1300mAh), and its longer, narrower dimensions are closer to the shape of the S960’s stock 5-cell 2/3A pack.
www.vxrracingusa.com/prodM_rcvr_211300_LiPo.htm
A Brief Background on LiPo
Borrowing from the informative VXR Racing site, here are some of the differences between LiPo batteries and NiCd/NiMH batteries:
“LiPo cells have roughly 4x times the energy density of NiCd or NiMH cells. Ounce for ounce, LiPo batteries can have lower resistance and a flatter discharge curve than the best NiCd or NiMH cells in the market. In other words, in the same application the weight of LiPo batteries could be 4x lighter compared to conventional NiCd or NiMH cells.
Another obvious advantage of LiPo over NiCd or NiMH is that LiPo does not have memory effect; you could run the cell half-way down and then charge it back to full capacity without any issues. In fact, you are encouraged to do so for your LiPo cells. In a NiCd or NiMH cell, you will get the most power out of the cell right after charging, and NiCd or NiMH will decrease in power and charge capacity over time and use. For LiPo, it is the total opposite; full-charge capacity will be maintained for 1 month without any problems. Therefore, if you know you will be racing in a month's time, you could charge the battery at your convenience weeks before racing.
For NiCd or NiMH, one cell is 1.2 volts, and when you put 5 cells together in series, it will produce 6.0 volts. For LiPo cells, each cell is 3.7 volts; by putting 2 cells together in series, it will produce 7.4 volts.”
IMPORTANT Reading
With the introduction of LiPo technology, there are some important things to know before deciding to use these leading-edge products.
The information in VXR Racing’s FAQ (frequently asked questions) section should be considered as required reading before “getting into LiPo.”
www.vxrracingusa.com/faq.htm
Here are a few highlights:
• You MUST use a LiPo battery charger to charge LiPo packs; you CANNOT use a NiCd/NiMH charger
• Care must be taken when charging and using LiPo packs
• When using the LRX-211300 pack in the S960, you must use VXR Racing’s 5A Switching Voltage Regulator (LVR-5000)
“What Does This Mean For Me?”
By this point, some of you may be thinking, “Okay, all these specs look impressive on paper, but what does this really mean for me?”
Well, besides knowing that you are using some of the coolest products on the planet, here are some compelling reasons for using the LRX-211300 LiPo receiver pack:
• Much lighter weight compared to 5-cell 2/3A NiMH pack (need we say more?)
• Much more consistent energy output to servos
• High capacity (1300mAh) for improved runtimes
• Low pack height means you can drop the fuel tank lower… instant CG lowering
Lighter, Smaller, Faster
This is ALWAYS a good combination to have in an RC car, where grams and millimetres make a big difference on the racetrack.
While I did not have a scale to compare the masses of the stock 5-cell 2/3A NiMH pack and VXR’s LiPo pack, just by holding the packs in your hands the difference is very obvious.
Holding the lightweight LiPo pack after hefting the heavier NiMH pack is like holding a small bag of air… the LiPo pack weighs THAT much less.
The Voltage Regulator Advantage
Where VXR Racing really shines is in their ability to harness and regulate the awesome power of their LiPo packs. To use the LRX-211300 LiPo pack in an RC car like the S960, you must use the LVR-5000 5A Switching Voltage Regulator.
Although the LiPo pack’s nominal voltage is 7.4V, its fully-charged 8.4V output exceeds the safety level of most receivers and servos on the market. For that reason, the LiPo pack must be used with the LVR-5000 5A Switching Voltage Regulator to reduce the battery voltage to a safe level for the electronics.
An added bonus of using the switching voltage regulator is that it ensures consistency in servo torque and speed; steering and throttle/brake servo performance stays consistent all the way through. Why? The regulator maintains a constant voltage (6.7V) at any level of current draw, up to 5A.
In comparison, when using a stock NiMH receiver pack, as soon as there is current draw (servo movement) the supplied voltage drops, which causes a change in speed and holding power of the servos, ultimately affecting response to transmitter inputs. And on a lightning-fast 1/8 on-road car like the S960, having quick response to transmitter inputs is vital.
The voltage regulator also provides a visual indication of the charge condition of your LiPo pack, via a green/red LED indicator. The green LED lights when power is on, and the red LED lights when the LiPo pack voltage goes down to 6.2V and below. It is important to note that over-discharging a LiPo pack (below 6.0V) may damage the cells; when the red LED lights, this indicates that it is time to stop and charge the pack.
www.vxrracingusa.com/prodM_regulator_lvr-5000.htm
High Capacity — Going the Distance
With today’s advanced digital servo technology, the benefits gained from faster, more powerful servos are offset by increased power consumption. With races sometimes lasting up to 1 hour or more, the need for higher-capacity receiver packs has become paramount to avoid premature dumping.
The LRX-211300 LiPo receiver pack offers great voltage characteristics AND high capacity: 7.4V (nominal) and 1300mAh. When you factor in the voltage regulation of 6.7V, runtime concerns become a non-issue.
Lower CG
After I installed the LiPo pack in my S960, I was astonished to see a HUGE gap between the pack and the fuel tank. With the lower height of the LiPo pack, I was able to lower the S960’s fuel tank by a full 4mm… I could have dropped it 5mm if I had really wanted to.
In the pictures to the right, the top picture shows the height difference between the LiPo pack (left) and stock 2/3A NiMH pack (right). The lower picture shows the LiPo pack mounted in my S960… notice how low the fuel tank is now.
Can you say, “lower CG?”
Mount ‘Er Up
Installing the LiPo pack my S960 was no more complicated than installing a stock 5-cell 2/3A pack. With the smaller dimensions of the LiPo pack, you also now have the opportunity to fine-tune the position of the LiPo pack on the battery mounting plate.
I opted to use Serpent’s new closed graphite battery plate (903188). This new battery plate does not have cell cut-outs, which of course are not needed when using the flat LiPo pack. The lack of holes also prevents debris and stones from damaging the underside of the battery pack.
Wiring the LiPo pack into the electronics calls for only minor concessions:
• The tiny, lightweight voltage regulator must also be installed
• Mechanical on/off switch only… no soft-touch electrical switch
• At the time that I wrote this article, the LVR-5000 voltage regulator is compatible only with Spektrum 2.4GHz modules and Futaba PCM. However, VXR Racing is diligently moving forward to engineer a switching voltage regulator that is compatible with all radio systems.
I used a custom graphite tray to mount both my personal transponder and voltage regulator to my S960. Some double-sided servo tape and zip ties made sure everything will stay secure.
And While We’re At It…
With all the coolness of the new LRX-211300 LiPo pack, I couldn’t stop there.
VXR Racing also offers some other great LiPo products to suit any RC application. Here are other products I am using:
• LRX-0500 LiPo receiver pack – great for qualifiers! 2S1P, 7.4V, 500mAh, only 23g, and tiny dimensions
• LTS-0001 LiPo transmitter pack for my Airtronics M8 – 3S1P, 11.1V, 800mAh, 86g, 3~4hr runtime… and it slides right into place!
Summary
VXR Racing’s new LRX-211300 Lithium Polymer Receiver Pack is the perfect receiver pack for my Serpent 960 — as well as other 1/10th and 1/8th nitro cars that currently use a 5-cell 2/3A (NiCd or NiMH) receiver pack.
In my opinion, the long list of PROs of using this fantastic new LiPo receiver pack far outweigh the few concessions that come with switching to leading-edge LiPo technology.
I eagerly look forward to racing my S960 this season with VXR Racing aboard.
IMPORTANT NOTE
It bears saying once again that you MUST educate yourself about LiPo technology and VXR Racing products to properly and safely use these great products.
VXR Racing LRX-211300
5-cell 2/3A pack vs. LiPo pack
LVR-5000 5A Switching
Lower pack = lower fuel tank = lower CG
Mounted regulator
LRX-0500 and LTS-0001
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