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Everything you need to know about LiPo batteries...

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Old 09-13-2013, 09:52 AM
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Default Everything you need to know about LiPo batteries...

I thought I'd make a post concerning the common questions raised around lipo battery ratings, cutoff and charging, for the benefit of anyone who wants to know what its all about. So without further ado...


Battery basics...

Lithium Polymer batteries were a revolution for our hobby, they offer significant benefits over their older NimH counterparts and are much lighter as well (in terms of power density/mass).

When you buy a typical lipo battery pack, it has certain characteristics which are described on the packaging...

Cells (S)... the number of cells in a pack can be expressed as 'S', for example, 1S, 2S, 3S, all the way up to 10S or even 12S for some of the really big applications, there is no theoretical limit to how many cells can be used, either in series or parallel (more about series vs parallel later). 'S' rating refers specifically to the number of cells in the pack. So a 2S pack is a 2 cell pack, etc, etc. Each cell has a nominal voltage of 3.7v.

Voltage (v)... The number of Volts the pack provides. This directly correlates to the 'S' rating. The S rating multiplied by the nominal voltage of a lipo cell (3.7v) will always give you a pack's voltage, meaning that if one (volts or 'S') is not provided, it can be discerned from the other. For example, a 7.4v pack will always be 2S, an 11.1v pack will always be 3S, and a 4S pack will always be 14.8v, etc. Note that healthy lipo packs can and will charge to up to 4.21v per cell when fully charged.

Duration/capacity (mAh)... this figure directly relates to the maximum duration of the battery in milliamp hours. A typical value for this is 5000mAh. Meaning that this battery under a constant 5000 milliamp load would last exactly one hour. Worth noting of course that 5000 milliamps is 5 amps.

C (discharge/charge/current rating)... This figure directly relates to how much current (in Amps) a battery can safely deliver. The important thing to remember about C rating, aside from the way it is calculated, which we will get to in a minute, is that it may be provided as one or two figures, 'sustained' (or continuous) and 'burst' (or peak). In most cases, both may be provided. If only one figure is provided, it may be impossible to tell whether it is intended to be the sustained or burst rating, exercise care under these circumstances.

The continuous or sustained C rating refers to the amount of current that the battery could deliver indefinitely without incurring damage. This is the main number to look at when selecting a battery for your model. The burst rating, refers to how much power the pack can theoretically provide for a short burst if required, but such loads should not be sustained for more than a few seconds. This is usually approximately double the nominal C rating, but can be lower or higher.


Calculating C rating. How does 'C' work, and what does it mean to me?...

So, let's take a specific battery as an example... A 3S, 11.1v, 5000mAh 30C battery. How do we know how many amps it can safely deliver? Simple: multiply the duration (5000mAh or 5A) by the C rating (30C). So, 5A multipled by 30C = 150A. This battery has a current rating of 150A. Burst 'C' is calculated the same way. Note that a longer duration battery does not necessarily have higher delivery potential, if it has lower C rating. Similarly, a higher C battery does not necessarily handle more current than a lower C battery of a higher duration. Both duration (mAh) and C (current handling) must be provided in order to calculate the current handling of a pack. For example, a 4000mAh pack at 100C can handle 400A. A 6000mAh pack (50% larger) at 20C can only handle 120A, a huge difference.


Charging...

When we're talking about charging a lipo battery, there are basically 2 main methods (programs in your chargers), Balance Charge, and Fast Charge (aka non-balance charge). There may be others, such as storage charge, which we'll talk about in a minute, but these two are the main ones we care about and will use more regularly. Lipo batteries which are made up of multiple cells (2S or more) need to be balanced while charged, as frequently as is convenient for the hobbyist (many would say there is never any excuse not to balance charge, and while they have a valid point of view, I think this policy is not always practical, or necessary, more on why in a minute).

There is much consternation concerning what is safe to do, not safe to do, what extends/shortens the lives of your batteries when charging. So, here's some info to allow you to make up your own minds, with my opinions thrown in for good measure. You should know that I am considered a 'careless' lipo user compared to most, but I have few problems, and can afford to replace a pack now and then.

Many batteries when you buy them, will also say at how many 'C' you can charge them (note that the charging C is almost always much lower than the discharge rating we talked about earlier, though calculated the exact same way). Typically, 1C is considered the charge rate which has the best time economy without doing damage to the cells. Some would say that if you have the time you should charge at .5C for the best battery longevity. Many batteries claim safe charging at very high C rates, but personally, I don't charge over 2C as a rule, even if they say I can. Most will limit you to 1 or 2C. Of course if your battery says 'charge at no more than 1C', then you don't charge at more than 1C (5A in our example battery, 5000mAh multiplied by 1C). Charge at high amperages at your own risk, no matter what the label on the battery states, and never forget the fire hazard that an overcharged lipo battery can represent.

In general, for RC cars, charging at 1C is considered the 'safe' charging method. Since a balance charge takes longer than a fast charge (naturally, since at the end of the cycle, the charger needs to balance the cells), a 1C balance charge would take longer than the assumed hour. In fact often taking an hour and a quarter or much longer depending on how out of balance the cells are. Personally, I charge at 1.2C generally, simply to knock off this extra balance time and get my batteries charged in an hour. So, I charge 5000mAh batteries at 6A. This usually means the charge is pretty much exactly an hour. It just makes planning easier when you have multiple batteries to charge.

So what does a balance charge do? Why is it so important? It's all about...

Last edited by Foxy; 09-13-2013 at 10:00 AM.
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Old 09-13-2013, 09:54 AM
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Cell balance and Lipo cutoff...

When we run our RC vehicles, eventually our lipo cutoff kicks in and tells us our batteries need to be changed. It is rarely the case that each cell of a 3 cell battery will have discharged at exactly the same rate (though we hope they stay pretty close, if not, then that would indicate a problem with one or more cells). So, when the cutoff kicks in, maybe one cell is now at 2.8v, maybe another is at 3.1v, maybe the third is also 3.1v. If we were to charge all three cells with the same power ('fast' charge or NON-balance charge), obviously, the highest voltage cells would fill up first, then the charger will stop, because it doesn't want to 'overfeed' the cell that is now full (that is a highly simplified analogy, it's not exactly like that, but for the layman, that explanation is good enough). So, we now have some small differences between the cells. At this point that they are only a few millivolts out, it's not really a problem, but the next time we run the car, they will become a little more out of sync, and a little more, and the same goes for each non-balance charge. Eventually it will reach a point where the cell voltages are so different, that one or more cells is being discharged way too low causing permanent damage to that cell and rendering the pack useless.

Where the 'balance' charge differs, is that when it sees the pack is starting to get full, it starts to charge each cell individually, stopping when a cell reaches peak (usually 4.19 to 4.21 volts) and moving onto the next one (or it may do it in a round-robin way, it depends on the charger). It keeps going in this fashion until it has topped up all cells and the pack is considered once again 'balanced', with all cells at as close to the same voltage as possible. If a cell gets badly out of balance, even 2 hours on the balance charge may not be long enough to correct it (most chargers have a time limit to prevent heat build up in the equipment). When the balance charge seems to go on forever, this is probably good indication that your pack is dead or dying. If this happens to a 3S or more pack, and you are handy with electronics, you could consider removing the bad cell and effectively creating a good pack with one less cell than before.

Of course it is therefore a good idea to use balance charging mostly, and I do. Mostly. It depends on circumstances. If you are in no rush, charging at home the day before a race or a big bash, always balance charge. If you are at the bash spot and about to run out of batteries, feel free to put one you just used on the charger on a normal (often called 'fast' or NON-Balance) charge, perhaps even at 2C to get it done quick (a non-balance charge at 2C will usually see the battery fully charge in about 25 minutes). You won't hurt it to do this once or twice, especially if you know the specific battery is well matched and is a well-behaved ack. I guess I don't need to say don't do this with a battery that you know is not balancing well. Even with your good packs, make sure that when you get home you balance charge it (or storage charge it - more on this later) properly. So my rule of thumb is; in the field, normal/fast (non-balance) charge at 1.5C or 2C (7.5A to 10A charge rate based on our example), and when at home, take the opportunity to balance and/or storage charge, ensuring the health of your packs.

So why is it so important to balance the cells? It's because of the permanent damage that can occur to cells that drop below a minimum voltage. The safe minimum voltage for a lipo cell is actually approximately 2.8v (remember they are nominally 3.7v per cell), but most people sensibly choose to set their cutoff at 3.0 or 3.1v per cell, some even go much higher, though I question the value of reducing your runtimes so much for the sake of a little extra longevity of a 40 buck battery. That sounds fine, I hear you say, and in theory it is, however, in practice, your ESC isn't actually cutting off at 3v per cell, it's cutting off when the pack total reaches the stated cutoff. 3v per cell in a 2 cell pack is obviously 6v, so that's what your ESC is looking out for, 6v total. If it were a 3 cell pack, 9v total, etc etc. Now let's see how this changes the game...

Let's take a real world example.... Johnny has had his Traxxas Stampede VXL for a few weeks, he got a couple of lipo batteries with it, but he doesn't know much about lipo and the cheap charger he bought isn't exactly plying him with information, so he thinks he's good doing a 'fast charge' every time. Who wouldn't? Faster is better! But what's been happening to his batteries is the following... Battery A is a 5000mAh 2S 25C pack. Unknown to Johnny, one of its cells isn't well matched to the others, as is common. So each time Johnny runs the car, one of the cells gets a bit lower than the others. Johnny's VXL speed control is programmed to cut off the power from a 2S battery at 6v, as we said above, but it isn't keeping an eye on individual cell levels, all it cares about is total voltage. Each time Johnny runs and then charges the batteries without balancing them, this mismatch gets a bit bigger. Yesterday, Johnny ran his truck as normal, but noticed that he got a little less runtime than usual. He doesn't think twice about it, goes back inside, puts the pack on charge only to be told 'Error' by the charger. Uh-oh, one of Johnny's cells has died. But Johnny had his lipo cutoff set correctly, what went wrong?

Johnny's problem comes from the weaker cell. Each time Johnny ran the truck, the cells were getting more out of balance, and this imbalance was not being corrected during the charging process because Johnny doesn't know to balance his packs. The last time he ran, the auto cutoff worked perfectly at 6v, but what nobody could see, was that in actual fact, those 6v were made up of 3.5 in one cell and 2.5 in the other. The cell that dropped to 2.5v is now dead, having dropped below the danger line of 2.8v.

That's why we balance charge when we can, cos ESCs are stupid and lipo cells are sensitive.

A quick note on Storage Charging to finish off this chapter on charging.

Most lipo chargers these days include a program called 'storage charge', and it absolutely should be used for exactly that, storage. When you know that the pack is not going to be used for a few weeks or more, you really should storage charge it. This is a charging program that will set the cell voltages to their nominal level, usually around 3.7v per cell. Lipos like to be stored at this 'mid-charge' point, and will hold this voltage for a surprisingly long time, many months. Why do we do this? Two reasons, to prevent the over discharging that we mentioned earlier, and also to prevent swelling from long periods sitting full.

We already talked about why we don't let packs get below 2.8v per cell, and the same is valid even when packs are not in use. Despite the fact that lipo batteries hold their charge for a very long time, they do slowly discharge, like all batteries which are not used. Of course this allows for the possibility that if they sit for long enough, they will discharge below the minimum level and cells will go bad. That's why we definitely don't store them empty, as it would not take long for this low limit to be reached.

The other way (storing them completely full), is less of a risk, but still invariably causes damage over time. This is actually the way that I have lost some of my lipos over the years, I tend to be lazy and not discharge them if I don't use them. This causes them to swell and damages the fine layers of material in the cells, again eventually rendering them inert. Many say that they have stored fully charged batteries for a long time, myself included, without any issues, it seems to depend on the pack. Better packs seem to survive longer, but at the end of the day, there's no need to risk it, just storage charge them when not in use and refresh that storage charge about once every two months in periods of extended disuse.

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Old 09-13-2013, 09:54 AM
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Serial vs Parallel

Serial = increases VOLTAGE (motor speed), not duration.
Parallel = increases DURATION, not voltage (motor speed).

Effectively, when you connect two batteries either in serial or in parallel, you are creating a single battery with double of one of its characteristics.

When connecting more than one battery, it is not essential, but HIGHLY advisable, to use identical packs, ideally even from the same manufacturing run if possible, to avoid major voltage mismatches. While in theory, you could use any two packs of the same characteristics (voltage and duration), the cells of one may be weaker or stronger than the other, and remember what we know about lipo cutoff? It can only see the whole battery, it can't see the individual cells, so that increases your chance of discharging one entire battery too low, while the other one carries on going. This could under extreme circumstances, be a recipe for an on-board fire. Match your packs.

So, parallel first. As stated, when we connect a battery with another in a parallel connection, what we are doing is combining the duration (mAh). Using two 2S 5000mAh 30C batteries in parallel, causes the duration to be added together, giving a battery with 10,000mAh. NO OTHER BATTERY UNIT IS AFFECTED. They are still effectively a single TWO cell battery, despite the reality being that there are now 4 physical cells, and they are still 30C

However, remember that C is an expression of duration? So now that the duration has increased, the calculated value of C has also increased. This can be a good way (provided you have space in your model) to get higher current handling alongside double duration. These 30c packs which can provide 150A each, now combine to produce a 300A current on demand. The downside to doing this of course, is space and weight in your model.

Serial on the other hand, does not affect duration OR C. It only affects VOLTAGE. Using two 2S 5000mAh 30C batteries in series gives you a single 4S battery, still of 5000mAh, still able to discharge at 150A max.

So lets recap. Parallel doubles the mAh, serial doubles the voltage (and therefore motor speed).

In general it is preferable to use a single 4S battery, than two 2S batteries in series, for reasons of charging convenience, weight, and reduction of points of failure (series adapter will add two extra connectors to your setup, unless you hard wire.

In 1/8th electric buggy (and truggy) racing you will most often see two 2S packs in series to create the 4S pack that is in-line with racing rules, this is largely because there are more ROAR (hard case, fixed dimensions) 2S packs around than approved 4S packs. While there are plenty of ROAR approved 4S packs around nowadays, they tend to be rather expensive. Non-approved 4S packs can vary quite dramatically from manufacturer to manufacturer in dimensions.

For reference, you can count on approved racing packs to be between 48 and 50mm wide, 24 to 25mm tall and 135 to 138mm long. Many battery trays are specifically designed for this size (annoying if you're not racing, as higher duration packs are often larger and more preferable for fun running).

That's the most important stuff for now, I may add to this as time goes by and I think of other things worth mentioning.


I hope you found this guide useful, and if you have a question I haven't answered, please post it and I may update the guide accordingly and credit you!

Last edited by Foxy; 09-13-2013 at 10:01 AM.
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Old 09-13-2013, 10:56 AM
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Great guide that should help alot of people! Can you sticky your own thread? lol
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Old 09-13-2013, 04:04 PM
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OMG. This is awesome. You write so brilliantly. YES! STICKY!!! +1000!!

Foxy: Who ARE you, masked man?
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Old 09-13-2013, 05:34 PM
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excellent!!!, its great to see people putting in the Extra time well above and beyond expectations to help out fellow hobbyists.
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Old 09-13-2013, 11:56 PM
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Thanks guys, appreciate it. I can sticky this if I choose and people think its worth it. Actually, I'm not all that happy with the sticky we have, so I may do a couple more guides on a few things, then replace the sticky. We'll see.
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Old 09-14-2013, 11:58 AM
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Awesome explanation....My head hurts, but awesome!
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Old 09-15-2013, 05:22 AM
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Definitely deserves a sticky!
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Old 09-15-2013, 06:26 AM
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Very good explanation and informative for those who are new to Lipos. Great job.

A point you may want to add about packs in parallel for new users though. When connecting packs in parallel it's important to make sure they are the same voltage or as close as possible, both packs fully charged would be ideal. When connecting 2 packs in parallel the voltages will try to even out the instant you connect them together. If the voltages are different one pack will be charging, the other discharging and the rate will be controlled only by the resistance of the wire and the connector. To prevent this they should also remain connected as much as possible, even during storage. In most cases this probably wouldn't do any harm, but if Johnny connect two packs whose voltages are different enough it could be.

I don't know exactly how in depth you want to go but talking about the validity of c ratings may be in order too. As I'm sure you know a 30c 5000 pack can't actually put out 150amps continuously without damage or selfdestructing and that it's more of a guide. Explaining how a vehicle may pull 120 amp spikes and how a 30c 5000 pack can keep up will probably help users avoid any problems down the road. The use of some graphs showing the amp draw of a system in a vehicle would help in this.

Just my .02, again great job.
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Old 09-15-2013, 06:48 AM
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Thanks for the tips Maj, I definitely will add something to the section on parallel use. I don't think I'll go as far as to include graphs, but I think you're right that I should mention that C ratings aren't mathematical certainties. Cheers.
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Old 09-18-2013, 01:04 PM
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so can someone tell me if the old powersupply method is okay to use for lipo chargers? apparently lipo is the new nimh - when i stopped doing RC ages ago that was thew new ordeal - im trying to get back in and looking to find out who are the leading competitors for trucks/buggys again.. before it was AE/LOSI..
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Old 09-18-2013, 01:04 PM
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also is there any type of chat room to access on the site or IRC for instance to get instant information from trusted sources
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Old 01-14-2014, 11:30 AM
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Quote:
Originally Posted by 702aefan View Post
so can someone tell me if the old powersupply method is okay to use for lipo chargers? apparently lipo is the new nimh - when i stopped doing RC ages ago that was thew new ordeal - im trying to get back in and looking to find out who are the leading competitors for trucks/buggys again.. before it was AE/LOSI..
Sorry I missed this post. In case you are still wondering, yes, many use old high wattage server computer power supplies to power lipo chargers. If anything the curernt requirements of the power supply have gone down with lipo. We don't charge at 20A any more on race day to wake our batteries up, lipos are a bit more sensitive than mAh and the penalty for screwing up is much higher. But the power density available...omg.

Losi and AE are still good brands, but the crown in most classes belongs to Xray these days in my opinion. At least in terms of kit quality and durability. Fact is they are all capable of being world champ, which one you buy comes down to preference and budget.
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Old 03-03-2014, 09:31 PM
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Excellent info.

I have a few questions regarding lipo use in, say, your basic 1/10 stadium truck. I've been flying fixed and rotary wing R/C since 1986. Did a few trucks/buggies (nitro) when the grandsons were little; they grew up, moved on, etc.

I got into e-power last year, have a half-dozen electric airplanes now, got a good idea of how to care for & feed lipos, got a Hi-Tec X4AC charger, etc., etc. IOW, I'm not a total noob at this.

I'm thinking about getting an e-ride, something simple like a Rustler, etc. But it seems like all the RTR offerings come with an NiMH battery. Now, I have lots of fond memories regarding nickle-metal-hydride batteries, but as you pointed out Lipos are where it's at today.

I thought about building a kit, therefore being able to spec out everything. But to do that right will be twice as expensive (at the very least) as a RTR. Still considering that angle, but here are my questions:

1. Can your basic RTR el cheapo ESC handle Lipos?

2. Is it really just a matter of setting the ESC for the different voltage and plugging in a Lipo, or do I need to acquire other gear in addition to the Lipo batteries?

3. Brushed or brushless? I am vaguely aware of the difference, am NOT concerned about the performance difference, just wondering if I need one or the other for Lipos. IIRC, all my plank motors are brushless out runners.

4. What's a good median size Lipo for a decent run time? I define "decent run time" as six or seven minutes of moderate driving; i.e., not hammer down the whole time. And what cell count? For instance, my larger (50 inch-plus) airplanes give me seven to eight minutes of solid power on 4S 3300/3900mAh packs. I have ZERO clue what size Lipo I need for this in a truck/buggy.

Any insight would be greatly appreciated. Dunno where this itch is coming from, but I'm gonna scratch it...

.
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Old 03-04-2014, 12:48 PM
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Answer to question #1: YES, if it SAYS it does. I think most RTRs these days, even if they come with a Nimh pack and a brushed motor, the ESC has a Lipo cutoff. Like, if you got a Rustler, the XL-5 ESC has a Lipo cutoff. Activate it, plug in your Lipo and go!

Answer to #2: YES, IF the ESC has a lipo cutoff. Otherwise, you may need a "battery alarm". This is an "external LVC" of sorts, that beeps when the lipo gets down to 3.2V/cell.

#3: Motors don't care. But these days, brushless motors can be had so cheaply, I cannot fathom why anyone would WANT a brushed motor. The ones that come with RTRs usually don't last very long anyway, as the brushes will wear out (or fall out!) and then you need to buy a new motor. Brushless motor have none of that, and can last a lifetime if properly cared for.

#4: Lipos rated at 5000mah are common now, and one of those will give you 25min run times. How many cells depends on your ride. Using the Rustler again, a 2S Lipo is fine, and it will be very fast. 3S on that car is almost un-controlable. (Unless you're just going in a straight line for speed runs)

THe other thing to consider about the RTR is that you'll also get a modern radio set. That is, 2.4ghz, no crystals, no whip antenna, no signal interference.

VERY IMPORTANT: DO NOT use NiMh batteries in a brushless system. (Particularly if your ESC is made by Castle) NiMh's voltage sags under load, unlike Lipo, and can cause ripple currents in the ESC that can damage it.
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Old 03-04-2014, 04:31 PM
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Thanks, Rob; copy all.

25 minutes??? Holy cow… works for me.

Think I'm gonna try a brushless Rustler. The LHS has some NIB, within a few bucks of Tower's price. He also has Venom 2S 5400mAh 20C sticks for $62, which matches Tower's price. These batteries have the "universal" connector goodies, so I don't have to fool around with making new charge cords.

Regarding the radio… I'm tempted to set it up on my Futaba 12Z airplane/heli radio, just to eliminate one extra thing (the car TX) to drag along to the field. Back in the day of 72/75mHz, that was a big no-no. But with 2.4gHz… who would care? If the radio with this Rustler is anything like the radios that came with the nitro trucks and buggies I had before, its absolute bottom-tier gear. Oh, I'm sure it works well enough, but… I've got several Futaba FASST park flyer receivers laying idle.

Anyway… cool, a new toy to play with and re-learn. This electric gig has rejuvenated my interest in the hobby. After almost 30 years of doing the wet-power stuff, I was close to being burned out.

.
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Old 03-04-2014, 07:33 PM
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Quote:
Originally Posted by LSP972 View Post
Thanks, Rob; copy all.

25 minutes??? Holy cow… works for me.

Think I'm gonna try a brushless Rustler. The LHS has some NIB, within a few bucks of Tower's price. He also has Venom 2S 5400mAh 20C sticks for $62, which matches Tower's price. These batteries have the "universal" connector goodies, so I don't have to fool around with making new charge cords.



.
Whoa whoa whoa....."Universal" connector? You mean the white Molex pieces of crap Tamiya still uses?? DITCH "EM, immediately. They cannot handle the current (amps) that Lipo can supply and brushless motors can draw. They WILL melt. I strongly suggest Traxxas conectors, or a type called EC-3. High current, easy to work with. Pick what you like (likely Traxxas since you're getting a Rustler VXL) but Tamiya connectors have no business on any decent brushless system. IMHO.
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Old 03-04-2014, 07:50 PM
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Originally Posted by LSP972 View Post
Thanks, Rob; copy all.

25 minutes??? Holy cow… works for me.

Think I'm gonna try a brushless Rustler. The LHS has some NIB, within a few bucks of Tower's price. He also has Venom 2S 5400mAh 20C sticks for $62, which matches Tower's price. These batteries have the "universal" connector goodies, so I don't have to fool around with making new charge cords.

Regarding the radio… I'm tempted to set it up on my Futaba 12Z airplane/heli radio, just to eliminate one extra thing (the car TX) to drag along to the field. Back in the day of 72/75mHz, that was a big no-no. But with 2.4gHz… who would care? If the radio with this Rustler is anything like the radios that came with the nitro trucks and buggies I had before, its absolute bottom-tier gear. Oh, I'm sure it works well enough, but… I've got several Futaba FASST park flyer receivers laying idle.

Anyway… cool, a new toy to play with and re-learn. This electric gig has rejuvenated my interest in the hobby. After almost 30 years of doing the wet-power stuff, I was close to being burned out.

.
I've heard of guys using "stick" radios for cars. If that's what yer comfy with, why not? And true, the RTR radios don't have many adjustment options some folks consider essential, but they do indeed do the job, and some actually DO come with more advanced features, these days.

That price is normal retail for that battery. I think 20C is a little conservative. I have found, despite theoretical calculations, that if a motor system draws a lot of power from a battery, and that pack strains to deliver it, the pack heats up, and heat is bad in electronics. I'd be happier to see you get 30C. Check out the Gens Ace brand at HobbyPartz.com . Comparable battery for 20% less.

It is pretty amazing the advancement in electric motor and battery systems for RC. The advent of affordable and safe LIPO battery tech, and brushless motor systems that rival nitro power has given e-powered RC a real boost in the last 5 years. Glad you're discovering a new aspect of an old hobby! Welcome.
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Old 03-04-2014, 07:59 PM
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No, not those miserable Tamiya jobs. I remember them from the time I built a BlackFoot; mechanical speed control and all. In fact, the memory of that experience (fun build, but the resulting model's performance was... Lackluster) was what convinced me to go RTR this time.

These are "adaptive" adapters, designed to be compatible with Dean's, EC3, and Traxxas. The battery has a Traxxas connector; one of these adapters goes between it and your charge connector if different. My airplane battery connectors are divided between EC3 and Sermos, so I'll be able to use charge leads I already have made up.

My original plan was to make everything the same, i.e. the Sermos/Anderson Power Pole connectors. But I started with a couple of Horizon airplanes, hence the EC3 connectors. Those are a PITA to separate, but ever since that kid showed me the trick with the snap ring pliers... Not so much of a pain anymore.

Anyway, thanks for the concern, but I'm on track.

.
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Old 03-04-2014, 08:38 PM
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I'd be happier to see you get 30C.

.
Me too. Not an option at the LHS; he's got 20C or 40C. And I kinda-sorta agreed to the cash price for the kit and three 20C sticks he quoted me.

Basically, I'm going to need to be careful in grass, make sure the motor doesn't load up too much.

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Old 03-05-2014, 05:46 AM
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No, not those miserable Tamiya jobs. I remember them from the time I built a BlackFoot; mechanical speed control and all. In fact, the memory of that experience (fun build, but the resulting model's performance was... Lackluster) was what convinced me to go RTR this time.

These are "adaptive" adapters, designed to be compatible with Dean's, EC3, and Traxxas. The battery has a Traxxas connector; one of these adapters goes between it and your charge connector if different. My airplane battery connectors are divided between EC3 and Sermos, so I'll be able to use charge leads I already have made up.

My original plan was to make everything the same, i.e. the Sermos/Anderson Power Pole connectors. But I started with a couple of Horizon airplanes, hence the EC3 connectors. Those are a PITA to separate, but ever since that kid showed me the trick with the snap ring pliers... Not so much of a pain anymore.

Anyway, thanks for the concern, but I'm on track.

.
First those "adaptive" connectors that Venom batteries come with are a pain. I bought a Venom for my nephew and put on the Traxxas connector that it comes with and it wouldn't work right with real Traxxas connectors. It was so tight trying to plug into the esc that it couldn't be plugged in all the way. I ended up just cutting it off and putting a real Traxxas connector on it as there was no way to fix the Venom one to work correctly.

Second thing about Venom Lipos is they aren't very good. They are more expensive than Turnigy and are not as good. Every Venom Lipo I've seen eventually puffed. My nephews Venom 4s 5000mah pack puffed within 3 months after bein run in a 1/8 buggy geared for 40mph. That's a setup that shouldn't have pushed the pack hard at all and temps were fine it's just junk. We had a couple other Venom 3s with similar results and I've seen so many puffed Venoms at my LHS I'll never touch one again.

Just my .02 cents.

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Old 03-05-2014, 12:05 PM
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Well, guess I'll find out directly. FWIW, these Venom batteries have Traxxas connectors; I'm going to use the "adapters" to charge only.

I am aware of the less-expensive battery packs, but two things keep me from trying them; first, you generally get what you pay for... IOW, cheap batteries are just that. Second, I have zero intention of allowing some overseas vendor such as HobbyKing to add me to their legion of unhappy customers. Yeah, I know there are a lot of happy customers. I also know a lot of folks who ride around without a seatbelt and "haven't had a problem".

I may yet try the less-expensive sticks; I'm still relatively new to the electric game and have a lot to learn.

Again... we'll see. Thanks for the input.

.
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Old 03-05-2014, 05:13 PM
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BTW, Rob; those 2S 5400 sticks are $49. The three cell sticks are $62. I got three of the 2S to start with.

The adapter plugs seem to work well. They are a bit of a PITA to swap, as the fit is pretty close. If it gets to be too much of a chore, I'll just change everything to the APPs.

I charged one, and its now getting a storage charge since I have no idea when I'll actually need it. Got some other stuff to do before I'm ready to run the car. At any rate, the X4 has no complaints with the arrangement, so maybe all is well.

Another question: It appears that the ESC has an on/off switch. Any problem with leaving it "on" if I need to stop driving for a while before exhausting the battery down to 20%? I know not to store the car with a battery hooked up; but I can see times when I won't drive a full 20+ minutes at one "sitting"… for instance, I might need to stop to help another flyer, answer a question, participate in a conversation, etc. I realize I must leave the TX on too (but if I can adapt that 4200mAh 6V pack, per the other thread, that won't be a concern). I'm just wondering about the ESC getting cooked with no load on it. The switch is inacessible with the body on, of course.

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Old 03-06-2014, 12:38 AM
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There's nothing to worry about. You won't damage the esc if you stop and leave the battery connected and esc switched on.
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