Introduction
After some problems with my IB3600 Stick Packs and after they fell apart I decided I would start searching high and low for the best Sub-C NiMh cells money could buy. I've been racing electrics for a few months now, and I am set to race them for a long time, so I thought it would work out better if I got some top-notch cells.
My first idea was IB4200 WC matched cells, rated as the best cells money could buy. After hours of research looking through websites and racing forums I came to the conclusion that this is not true, and they are apparently extremely fussy to look after and the newest batch are only good for 10 cycles before the performance diminishes drastically. I then found http://www.rcracechat.com/ and spent hours in the Cells / Chargers section to see what the top national drivers on there used. Some people were complaining about the IB4200 WC cells, whilst others were praising them, but at £40 a pack it would take me a while to get the extra money I needed.
I was then directed to the East Power (EP) 4200mAh cells, which are BRCA legal. I found, through many forums, that these cells were rivalling, if not beating, the IB4200 WC cells. So I spent another few hours shopping around when I came across http://www.demonpowerproducts.co.uk/...
In Depth View
A fully assembled set of matched EP4200 cells with just wires (no connectors) will set you back £32.85 here in the UK. To good to be true I hear you say? Well, that's the first thing that came to my mind as well, yet a lot of people from various forums have purchased their EP4200 cells from Demon and are over the moon with them.
After the weekend, I wake up to find a nice brown package sitting on the floor in my porch hiding behind some R/C touring cars. I quickly hurdle over my hauler bag, grab the package, and jump back, dashing into the living room to open it. The first thing I noticed when I opened the bag was how well protected its contents were. The package was lined with bubble wrap and the contents were packed in tightly with more bubble wrap. I unwrapped everything to find 3 perfect sets of EP4200 cells, all with rather impressive matching labels (the numbers were impressive, no artwork here) and nicely assembled with silver connecting bars and high quality silicone wires. I had requested for them not to include connectors, as I already had Deans connectors to solder on. Each battery pack was neatly presented in its own clear plastic bag so that it didn't short out during transport. One thing I would have liked to see was re-sealable bags, so that I wouldn't have to buy a battery storage box. I quickly solder the connectors on with my soldering iron, ready for the next step: charging. The cells are already matched and cycled from the factory, meaning they are ready to charge and use right out of the box. In all 3 battery packs, each cell is matched to 1.30V, which is an absolutely outstanding number for cells that are pretty much unheard of.
After the first pack finished charging, I locked and loaded them into my car, plugged them in, and turned on the transmitter and Mamba. I took the car outside, placed in at the end of my driveway, and blipped the throttle. The car whizzed off the line like I had never experienced (granted, I had never had the priviledge of testing high-performance cells before, just IB3600 Stick Packs). The car ran for a good 6 minutes without any loss of punch whatsoever. Things ended with a nice head-on into a curb, and I cracked the servo. So I brought the car back in to assess the damage, although there were no major breakages elsewhere. I had charged the cells at 5A, ran them hard for around 6 minutes, and when the pack came off the car it was no hotter than when it had come off the charger! But the final proof would come that night with the racing. I was entered in the Unlimited 2WD class, which meant that anything goes except LiPo batteries. My setup was a B4 with a Mamba Max 5700 and the EP4200 cells.
I started the night with all three of the packs fully charged, and arrived at the track to find it almost empty. So I unpacked, put one set of cells in the car and went out with my friend. He was also running a B4 with an 11x2 motor. Last week, his car was slightly slower than mine down the straights, but this week there was a huge difference. The way this car pulls away now is phenomenal! The first round of the race, I was still getting used to everything, so I finished 3rd overall. With 5 heats after mine I had plenty of time to play with the car to try and get it to come out of the corners properly to show the true colours of these cells. For the second round, I had just re-peaked the second battery pack, which gave me even more punch, thus enabling me to finish only 2 laps before a lower eye on of the rear shocks gave way. The third round saw still no driver improvement, but as noted by several spectators, my car was the quickest on the track (which it certainly wasn't last week). The final saw some driver improvement on my behalf and I managed 2nd.
As I didn't check what the cells were taking in when I first charged them, this is what pack #1 took in after 12 minutes of run time and overnight storage - 9.486V and 3084mAh. So it's fair to say that these packs can hold a fair bit of juice! On a discharge cycle at 1A from fully charged down to 5.4V per pack, the cells were kicking out 4876mAh and my charge couldn't get them fully down to 5.4V (they insisted on 5.9V for some reason!).
Summary
As you have probably realised, I am really fond of these cells, and I would gladly recommend them! I am sure you will notice a difference over almost any other cells you have tried. I know I was impressed by the labels, and everyone else was as well, so I am sure you will be too!