i searched... there were a couple threads, but nothing substantial... and they were old. let's do this right. with this thread title, any search will pull this up. OK, let's get started. i'm taking the electric jump... and i'm craving info. i have posts all over this forum, and i am getting a slew of great info. now let's get the batteries out of the way... i am sold on LiPo / Li-Ion. so... let's start there.
CHARGERS
after doing a little digging, i think i want this:
good buy? good all around charger?
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BALANCERS
now... what exactly is a balancer for? are they necessary? if and when i need one, i would be going with:
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as for BATTERIES...
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:whack: if there's any info people could give here, that'd be great. i'll update the original post as needed to keep it pertinent, relevant, and current!
CHARGERS
after doing a little digging, i think i want this:
i will soon be owning a mini-T, which i will be taking brushless (2s, 1000-2000 mah), and eventually, i will have my E-Revo (4s, 6000-8000 mah), so that charger can handle both.MaxAmps.com said:Of course, the AC/DC part means that you can charge directly from an AC wall supply while at home or from a 12V DC battery/power supply.
- Charges NIMH, NICD, and Lipoly
- This is our best all around AC/DC charger
- 1-14 NIMH-NICD and 1-5 Lipoly Cells
- Up to 5 amp charge rate
- Comes with data port
price ~ $120
good buy? good all around charger?
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BALANCERS
now... what exactly is a balancer for? are they necessary? if and when i need one, i would be going with:
good buy? good all around balancer?MaxAmps.com said:price ~ $50
- 2-6 cell smart balancer
- Network 2 units together for 2-12 cell balancing
- Comes with 2S & 3S Adapters. Others available seperately.
Shawn_Palmer from RC Car Action Forum said:Balancing, and more specifically the NEED to balance is a hotly contested subject right now. In my experience and opinion, if a pack (especially just a 2 or 3 cell car pack) actually requires balancing during any time during it's lifespan, you'd do well to look into another brand. That's a harsh viewpoint, and may not be shared by many openly, but it's my honest opinion from working with many many brands for many many years.
Basically, you can view balancing a lipo pack like a continuing process of matching NiMH cells. NiMH cells are manufactured by the billions and due to this large scale of production economy, each and every one is slightly different. Just about everyone is familiar with the process of starting with a large sample group of NiMH cells and matching their internal resistance (voltage under load) and runtime. There are very few factories producing just a few brands of these cells, so the same process needs to be used for all of them. Lipos are a little different. There are dozens of factories producing hundreds of brand names of lipo cells, and they vary radically in both performance and safety. The same brand name may even source cells from several different factories! Making sure the pack containing multiple cells will perform consistently with the cells inside "in balance" ovedr time is an issue that is totally dependent on the individual pack. As stated above - some you’ll never have to worry about, some you’ll NEED to worry about from day one.
Since we’re naming names here, I’ll lay it all right out on the table. Kokam America uses a patented construction process and an almost entirely automated manufacturing line. They are also the only lipo brand I’m aware of that actually owns it’s own factories, so the brand and the factory are actually one in the same. Due to these unique features, each and every cell off the line actually IS the same as all the rest. Kokam’s main business is supplying the aerospace industry (both private and government projects) and remains the only "hobby active" lipo factory I'm aware of that can make that claim. In my own experience, Kokam packs will provide a full cycle life without becoming imbalanced as long as they are not abused. Combined with their non-flame chemistry and excellent output performance, it’s easy to see why Kokam is the brand of choice for my own personal vehicles. The only downside to the Kokam line of packs is their price compared to other brands (and in this case - you really DO get what you pay for), and the lack of a pack that fits the 18T and similar vehicles.
A close second are the Apogee Magnum packs. Apogee is the only brand I’m aware of that truly factory matches the cells within each of its packs. The manufacturing process may not be quite as consistent as Kokam, but it’s made up for by an extra step before pack assembly. Apogee Magnum packs will also provide a full cycle life without worry of balancing as long as they are not abused. I’ve used and recommended Apogee brand packs for both surface and aircraft since the inception of the company, and continue to do so to this day. Apogee was the first to provide a non-flame chemistry pack specifically for the car market (the Magnum 3800mah) and now offers a great Magnum RC18T/B pack.
Tanic packs have recently introduced an excellent and elegant solution for the car market. Tanic has provided some of the highest performance lipos to the market for many years now. They have recently become compatible with the CellPro automatic balancing charger for a true and easy "Plug and Play" solution and thus have become an excellent entry point for thousands of racers to safely experience all the benefits of lipo power. Balancing is performed each and every time the pack is charged (via the CellPro charger) which virtually guarantees the pack will deliver a full and balanced cycle life to the user. Along with an ESC or external device to provide a proper cutoff voltage, there is almost no chance of damaging the packs. It’s no wonder these packs and charging systems are so popular in the newly emerging lipo racing market right now.
As far as charging through the balancing connector - if you do, there are caveats. First - only charge at an extremely low charge rate - say no more than 0.5A regardless of the capacity of the pack. Second - use of the balancing connector requires a matching connector to plug into an external balancing device (Kokam Lipolizer, AstroFlight blinky). CONSULT THE PACK MANUFACTURER/DEALER for advice as to what balancer device to use, and when/how to use it for your brand of pack.
As a general rule, ALWAYS charge and discharge through the main (heavy guage pos and neg) battery leads just like you would for a NiCad/NiMH pack. Balancers all work in different ways, and some you can charge with, and some you cannot. I'd recommend using packs from the list above, and then not worrying about having to balance them at all.
One of the main Lipo brand folks and I discussed the balancing ports on their packs a while back, and he dubbed them the "PPP" ports. "PPP" standing for Paranoid Placation Ports. In other words - they are only there to satisfy the few overly concerned folks, and largely go not only unused, but aren't even recommended to be used from the factory brand itself.
So basically - with good packs in the first place, don't worry about it.
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as for BATTERIES...
sweetdiesel said:Lipo pack companies have much more competition now than they did a year or two ago. Just a sample of companies that have good packs are Maxamps, Apogee, Flightpower, Kokam, Orion, and Thunder Power. I'm sure there are other good brands. Least expensive are maxamps, the most expensive are Flightpower. [...] Like anything you get what you pay for, if you can afford to buy well now, it will be money well spent. I'd stay away from no name ebay packs, their C rates often do not live up to
what is printed on the label.
and...
Low Kv rated motor systems that use high cell counts are more desirable than high Kv/low cell counts for a few reasons. The higher voltage system will run cooler and more efficiently than a lower Kv system. There is also more starting torque with a low Kv motor. The drawback is that running a higher cell count means more weight from the batteries. It's also more expensive because high cell count batteries cost more money. Trying to find a happy medium between cell count, weight and efficiency is key to a good system.
Shawn_Palmer from RC Car Action Forum said:Voltage
The # of cells in the pack determines voltage. Each cell is 4.2v fully charged. Most folks are comfortable with the fact that each cell in a NiMH/NiCad pack is around 1.5v fully charged, and the same principles apply to lipos.
6 NiXX cells = around 9.0v fully peaked, and pack rated as 7.2v (1.2v/cell) as its "nominal" voltage. 2 lipo cells = 8.4v fully charged, and pack rated as 7.4v (3.7v/cell) as its "nominal" voltage. 3 lipo cells = 12.6v fully charged, and pack rated as 11.1v (3.7v/cell) as its "nominal" voltage.
As you can see, "nominal" voltage is fairly arbitrary in both cases, as it's neither the fully charged voltage, nor the fully discharged voltage, but somewhere in the middle.
Current output capability
Lipos are commonly rated as "10C" or "15C" or "20C". The "C" stands for the capacity of the pack in Mah (milliamp hours). The "10, 15, and 20" stand for how many times of the capacity the pack can deliver continuously in amps.
So a 3800mah pack rated at 10C can deliver 38A continuously. A 3800mah pack rated at 20C can deliver 76A continuously.
"Ratings" can be misleading however. Apogee, Kokam, Orion, Peak and Tanic all have an impeccable record of their products standing up to what they SAY they will deliver.
So what does this have to do with anything? Well, lipos are subject to the same rules of performance as any other battery. They are still an electron storage device - just in a different package and configuration than you're used to seeing. The main parameter controlling a battery's performance is internal resistance. The lower the internal resistance, the more amps (speed/punch) it can deliver, the higher the voltage (speed/punch) it will maintain during that delivery and the cooler it will be at the end of the delivery.
So the above "10C" 3800mah pack would give lower top speed, less punch, and be hotter at the end of a run than the "20C" 3800mah pack. The exact same run will also use more mah from the 10C pack than it would from the 20C pack.
So the (actual) "C" rating of a battery is important to know, but what else affects performance?
Mah Capacity
One of the most interesting things about lipos is that as the Mah of the pack goes up - so does the output performance. As above - a 10C 3800mah pack can do 38A. If we parallel two of those packs together to make one 7600mah pack, we can then get 76A from it. From the above, we know that the more amps the pack is capable of, the more speed and punch are available, and at a lower pack temperature. So ideally, we'd want to run the most mah that can fit in the car, and have that pack be "rated" for the highest reliable "C" rating we can find. This maximizes speed and punch, and minimizes heat within the pack.
Just like you wouldn't want to run the GP1100 pack from your 18th scale car in your 10th scale car, you wouldn't want to run too small of a lipo for the performance that you want.
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:whack: if there's any info people could give here, that'd be great. i'll update the original post as needed to keep it pertinent, relevant, and current!
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