Most of you reading this know how enjoyable, social and educational the hobby of radio controlled vehicles is, but we often fly under the radar of the hobbies generally known to the public. As an outdoor alternative to something like video-games we think that the public deserves to know all about our hobby, so we’ll be attending a couple of public events in the next few weeks to shout all about it!
First up is the Engineering Week Public Display on Saturday 24th March at the Halifax Central Library from 9:30am until 3pm. We’ve had a stand there for last two events, and it’s a great spot to let people know about our amazing hobby. We’re back again this year so if anyone wants to stop by and talk R/C, then please do. If you’ve got family or friends that you think might like to learn about R/C then feel free to send them our way. The “Public Display” event also has other science and technology related stands to see and the library is always fun for the kids. Check out the bottom of this Engineers Nova Scotia Events Page for their details but it’s free to come and see us!
We’ve also got a stand planned for the Shearwater Spring Hobby Show on April the 7th and 8th (10am – 4pm) Saturday will see us at our typical stand of tables and an assortment of cars, but this time we’re getting a much larger area for our display on Sunday 8th at which we’ll have driving demonstrations of many more vehicles, and example R/C kit sub-assemblies for you to try your hand at building. More details to come about the Hobby Show event next week.
If you are also passionate about the R/C car hobby and would like to contribute to the broader community, then the Halifax Radio Controlled Park Society are always looking for additional committee members whether that is on the Beaver Bank park maintenance side or in the R/C promotion side. Email us on email@example.com if you’d like to help out.
And remember, our Fundraising Raffle is still going on. We’ve sold just over 130 tickets and the draw will happen at one of the the Halifax R/C Park maintenance events in Beaver Bank sometime in April or May.
So there’s lots of great information out there on the internet for newcomers to the R/C racing hobby, but this short video from Jason at Short Course World hits some really important points.
He’s definitely right that top speed isn’t that important – You’re faster when you crash less, and crashing less means practice and starting off slow (plus when you hit stuff, and you will hit stuff, you’re less likely to break stuff if you’re going slower).
There’s work in the background to try and get some more regular racing going at Halifax RC Park this coming year, with the possibility of true lap-times and an organized race-event format (i.e. 5min races, with classes to suit everyone, beginners/kids included). But that all depends upon keeping the facility open in 2018 – we still have lots of tickets for our fundraising raffle.
This is a bit of a Public Service Announcement regarding Lithium Polymer (LiPo) batteries. Over the past year I’ve purchased a couple of used RC cars that came with LiPo batteries. I didn’t need the batteries per-se, but the condition of the batteries when they arrived has made me wonder whether people really know how to properly care for them.
On the beginners page of this very website we have a section on batteries, including LiPos. It gives some basic information but I thought it’d be worth highlighting some of the critical aspects, as LiPo fires are certainly possible without the correct care.
And since the detail below is a bit wordy, here’s a quick summary:
DISCHARGING ANY INDIVIDUAL CELL BELOW 3v WILL DAMAGE IT
CHARGING ANY INDIVIDUAL CELL ABOVE 4.2v WILL DAMAGE IT.
ALWAYS BALANCE CHARGE
CHARGE AT 1C (the capacity of the battery in Amp)
CHARGE IN A LIPO SACK/BAG AND NEVER LEAVE CHARGING BATTERIES UNATTENDED
SET YOUR ESCs LOW VOLTAGE CUTOFF (LVC) >3v/cell
(Optionally use a Low Voltage Alarm (LVA) plugged into the balance port set to >3v/cell)
RECHARGE TO 3.85v/CELL FOR STORAGE or
DISCHARGE A CHARGED PACK DOWN TO 3.85v/CELL FOR STORAGE
IF A BATTERY PUFFS UP, STOP USING IT
Overview of a LiPo
A LiPo pack is one built from ‘cells’. A single cell is nominally rated at 3.7v (volts) but operates between 3v and 4.2v depending upon state-of-charge. A LiPo pack made of a single cell is referred to as 1S. Therefore a 2S pack, is a battery, made of two 1S 3.7v cells totaling a battery pack of 7.4v. Likewise a 3S pack is made of three cells giving a total voltage of 11.1v.
The cables coming from the battery will include the main Positive (+ve) and negative (-ve) wires, but also a balance lead that links to the +ve and -ve terminals of each individual cell inside. For a 2S pack, that balance lead has 3 wires allowing you (or your charger) to measure the voltage of each cell.
Charging you LiPo
There’s is one mantra here – ALWAYS ALWAYS BALANCE CHARGE. That is when the voltage of each cell within a pack is monitored while charging. You’ll need to set your charger to the number of cells (1S-6S is typical) and to connect both the main connections, and the balance connector to your charger. The majority of the ‘juice’ is fed back into the battery via the main cables, but nearing the end of the charge, the charger carefully tops up each cell separately. A LiPo is fully charged when each of the cells within it reach 4.2v. CHARGING ANY INDIVIDUAL LIPO CELL ABOVE 4.2v WILL DAMAGE IT.
As far as the charging rate goes, unless you’re totally running out of time (i.e. between heats at an important event) then it’s always best to CHARGE YOUR LIPOs AT 1C. C is a measure of capacity so if your pack is a 5000mAh (milli Amp Hour) then you charge at 5000mA = 5A. The charger begins charging at that rate until the cell voltages get nearer 4.2v and then the charging rate slows to a crawl when the charger smartly charges only the cell that needs the power. Charging is completed when each cell in the battery pack has a voltage of 4.2v. CHARGING ANY INDIVIDUAL LIPO CELL ABOVE 4.2v WILL DAMAGE IT.
Pit Tip: Charge on a non-combustible/non-meltable surface. I use an old porcelain floor tile I had lying around. Saves your workbench/window-sill if something goes wrong.
Using your LiPo
DISCHARGING ANY INDIVIDUAL LIPO CELL BELOW 3v WILL DAMAGE IT.
You should always check that your Electronic Speed Control (ESC) has it’s LiPo Low Voltage Cutoff (LVC) enabled, and that it is set to some reasonable value exceeding 3v/cell if user-switchable. Although the ESC manufacturers are trying to be helpful by letting you set it to a value of a particular voltage/cell, the LVC is actually fairly dumb since it can only MEASURE VOLTAGE ACROSS THE WHOLE BATTERY (the balance leads aren’t connected to the ESC). So even though you set the LVC to 3.0v/cell, the ESC actually decides whether you’ve plugged a 2S, 3S or whatever pack into it, and then determines the multiple of 3.0v that it’s going to cutoff at. So when you connect a 2S battery, the ESC thinks “this battery has a voltage somewhere between 6 and 8.4v so it must be a 2S and I’ll therefore cut-off when the voltage drops to 2*the user-selected value = 6v (in this case)”. It’s trying to be smart, but you can imagine that if one of the cells in this 2S pack is going bad, then the ESC won’t see a problem even if one cell was dangerously low at 2.6v and the other was totally fine at 3.5v. The ESC just sees 2.6+3.5 = 6.1v and thinks everything is fine. It’s much safer to set the LVC to something like 3.4v/cell, where a 2S pack would be cutoff at 6.8v.
There’s also a small circuit board available for around $5 called a Low Voltage Alarm (LVA). It’s connected only into the balance lead on a battery pack and is small enough to leave in your vehicle while running. Basically it’s a voltmeter with a bloody loud alarm on it, and it’s CONTINUOUSLY MEASURING THE VOLTAGE OF EACH CELL. The voltage at which the alarm sounds it user selectable, but since you’re measuring the voltage of each cell you can set it to just over 3v/cell. It’s a great fail-safe and one that could save your battery.
Storing your LiPo
If you need to leave your LiPo unused for a few days, weeks or months (you know, because it’s wet out!) then putting them safely in a storage condition will keep them lasting longer. This is something lots of people overlook – myself included when I first started using LiPo batteries. STORAGE is when each cell in the battery pack is at 3.85v. It’s just above mid-way between a full charge of 4.2v/cell, and a used battery at 3v/cell. If you’ve run your battery down to 3v/cell then you’ll need to STORAGE CHARGE TO 3.85v/cell. Most chargers have a STORAGE option, which is just like balance charging but it stops at 3.85v/cell not 4.2v/cell.
If for some reason, you didn’t fully use a charged battery, say because you smashed the front corner off your car on a rock. Then you’ll need to DISCHARGE TO THE STORAGE VOLTAGE OF 3.85v/cell. Most chargers had a discharge setting, but it takes a really long time. The single most useful piece of equipment I’ve added to my battery maintenance is a cheap ($30max) 150watt DISCHARGER/BALANCER that takes your battery pack down to 3.85v/cell, or balances mismatched cells if you forgot to balance charge. There’s lots of similar looking devices out there on eBay/Amazon, but make sure you get the one with the light-bulbs on as that’s what gives you a reasonably quick discharge rate.
Store your LiPos disconnected from your vehicles, and in a sturdy container, so they can’t get damaged or punctured.
Pit Tip: I store my LiPos inside an ammo can, with some foam washing-up sponges cut to stop the batteries moving around and banging into one another. However, do take the rubber seal out of the lid to avoid creating a pressurized bomb if one of the batteries leaks/explodes inside the can.
Taking care of your LiPos will make them last longer and keep you safe
If you have any questions, or corrections then feel free to get in touch.
We’re normally very much Halifax/Dartmouth R/C focused on halifaxrcpark.com, but for those of you interested in R/C racing slightly further afield, here’s a little report on last weekends race at Cap Pele Revolution Raceway in NB that a couple of us from your committee attended.
The race series at Cap Pele runs from May until October about once a month and draws drivers from all over the region. George puts on a great event, with Mylaps/AMB timing system (with loaner transponders for those without their own), times uploaded to LiveRC, and classes for pretty much everything out there from 1/16 electric to 1/8 nitro buggies. The track George has built in his yard is quite a challenge for the drivers with some very interesting sections that are in his own words – “made to be difficult”. There’s some bumpy washboard, a couple of sets of double-jumps, a 90° tabletop plus a neat section of moguls that when taken exactly right mean you can cut the last corner by leaping clean over the track marking.
Personally I entered 2WD electric buggy, 4WD electric Short Course Truck (SCT) and 1/8 electric buggy. After just over a 2.5hr drive, we had time for a handful of practice laps before the qualifying rounds started at about 10am. Each qualifier lasts 5min and drivers start at 1 second intervals to allow for maximum qualifying pace. Here you’re looking to complete the most laps you can in the 5min period. Making few mistakes is important as consistency is king. And it’s important to let quicker cars past as cleanly as quickly as possible. The results from the qualifiers for each class seed your start position for the finals.
Both the 2WD buggy, and 4WD SCT had enough drivers for a couple of qualifying races, and then for both a B-main (second tier) and A-main finals race. I was fortunate to qualify in 7th for both classes which meant I only had to race in the A-main. Those qualifying 8th and below, raced in the B-main with the top three from that race taking a ‘bump-up’ into the A-main. 1/8 Electric buggy had just under 10 drivers so a single A-main covered everyone. My final qualifier in 1/8 E-buggy went well and I qualified 3rd on the grid for the finals.
2WD buggies are hard to drive cleanly. They under-steer like crazy when on the throttle, and then quickly turn to over-steer under breaking as the weight transfers forward making them the most difficult to drive cleanly. After a terrible start where I dropped to the back of the field, I managed to claw my way back up to 7th before the end of the 7min long final.
4WD short course trucks are big beasts but take the bumps well. I managed to put together a handful of successive clean laps to claw my way up the field from 7th to 4th place within three laps. Some tight racing followed for a few laps after a mistake from the driver in front found me up in 3rd. I was quickly catching the racer in 2nd but a big mistake a couple of laps from the end meant I fell another 10 seconds back – not quite far enough to be caught before the end of the race. But I’d managed to secure 3rd on the podium overall which felt great. You can see the entire race details here on Live RC: http://cappelerevelutionraceway.liverc.com/results/?p=view_race_result&id=959310
1/8 E-buggy are quicker still than the SCT races, but starting high on the grid made for a less eventful first lap and keeping it clean (or at least cleaner than the guys that followed) means I didn’t even pass or become-passed by anyone for the entire race. Check out my amazingly consistent position tracker from Live RC:
Overall, I was both happy and surprised at my performance. Obviously getting some R/C practice in at Halifax R/C Park has paid off a little over the years, and I’d encourage you all to do the same. We hope to be able to put on events like this in the coming years, but its dependent on keeping the track in good condition (which is always a challenge). We need more jumps and bumps though!
We had a great time at the Shearwater Hobby Show over the weekend. Thanks to those of you that came out to say Hi and for those of you who are only seeing this because you took one of our information cards, “welcome to our website, and welcome to the hobby of R/C cars”. Unfortunately we didn’t get the chance to put on a full demonstration on Sunday morning, but we’ve been promised that nice carpeted area for 2018. Look out for details of our plans for that area sometime in March 2018.
We’re getting near to the time when track maintenance can start in earnest out at Halifax RC Park in Beaverbank, so keep checking here for more details. Many hands make light work!
If you’re scratching around for something to do this weekend then how about coming along to the Shearwater Spring Hobby Show on Saturday 8th or Sunday 9th April (this coming weekend). We’ll be there with lots of cars and trucks to see, along with a few smaller ones to try for yourself. A few more details on our post from a few weeks back.
We’re just about finished at the Halifax public library for the national engineering month show. It was a great time and driving some fun rc cars outside in the snow was fun. Good to see some of you and hope to see you all in a couple of weeks at the Shearwater hobby show.
Halifax RC Park will be joined by the Halifax RC Drifters and some trail truck guys at our annual stand at this years Shearwater Aviation Museum Hobby Show. You’ll be able to see a wide variety of RC vehicles, and we’ll again have some mini-trucks for you to try. On the Sunday morning (10am-12noon) there are plans afoot for a larger indoor RC demonstration where we’ll have a track setup on a carpeted area (postponed until 2018 – we’ve been promised!). Come and say hi and look over the wide variety of vehicle types making up this fun and lifelong hobby.
The show is located at the SeaKing Club within Shearwater Base. You’ll need ID to get through the main gates on Bonaventure Street (the same street as Shearwater Aviation Museum). Opening hours are 10-4pm Saturday and Sunday. It’s $5 per person or $12 for a family of 4. Tickets also give you access to the Aviation Museum which is a great walk around. Details from the Aviation Museum here. Exact Google maps location of the SeaKing club is here.