A decent charger will save you a fortune in potential airframe breaks
I want to explain how a good quality charger will one day save your model. If you’re expecting an explanation of how batteries work then you’ll be disappointed, as I tend to commit to memory only the facts that I need to know. I don’t need to know about the chemical reactions within battery cells, but I do need to know how to look after them properly and what signs to observe in their charging / conditioning process.
TERMINAL REASONING
Batteries are funny old things, and I reckon that more models are lost through battery failure than anything else. Sometimes it’s hard to identify the cause of a model’s demise and we usually put it down to radio failure or interference; this could indeed be the case but it’s far more likely to be battery failure that shuts a model’s system down.
Examining the wreckage of a clubmate’s aeroplane a while back, we chatted over the likely causes of the crash. Radio failure was at the top of the list and this seemed like the most obvious reason given the lack of any alternative theories suggested by the wreckage. However, something made me pick up the Rx battery pack, still encased in foam and hidden from view. I peeled back the foam a little and noticed that the pack was an odd shape. Removing the foam completely revealed a badly misshapen standard 4-cell pack. A cell had burst, and although still connected it was clear that whilst the voltage had possibly been close to normal, the capacity of the pack was compromised and quickly failed under load. The cell would have burst during the charging process and not been noticed, neither visually nor through a simple voltage check, before flying. It was a lesson for both of us, so I decided it was time to get to know my batteries a little better.
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Prior to this experience I did what most flyers do: build a model, carefully fit the servos, Rx and battery and then pack them away with foam and forget about them until the model had served its useful purpose. During this time the battery would be hidden away in the dark, unseen and untested despite being the heart of the model’s wellbeing. I would fly the model once a week, normally on a Sunday morning, and give it a good 24-hour charge the day before. The charge would be administered whether the battery needed it or not and, irrespective of the number of flights I had on the day, a similar charge would be re-administered the following week. The battery would never be fully discharged, and although I generally replaced them every 24 months their capacity was never tested during these periods. A quick check with a voltmeter before a flight would confirm that all was okay, and off I went.
It was only when I started to immerse myself in electric flight that the difference between voltage and capacity really became apparent. I started to charge my electric flight packs with a greater awareness of their nature and I began to view the Rx batteries in my i.c. models with a new awareness of their properties.
ULTRA 30
The Ultra Duo Plus 30 will last you a model flying lifetime
Which brings us to the aforementioned ‘black box’. Last year I decided to join the Li-Po revolution; these new cells are difficult to ignore when their power-to-weight capabilities are considered, and eventually every electric flyer will find themselves buying a Li-Po pack. This means buying a charger that can handle them; NiCad / NiMH chargers simply won’t suffice, unless you like starting fires! Dedicated Li-Po chargers are pretty cheap and can be purchased for as little as £20 – 30, but I wanted a unit that would do more than just charge cells. I wanted to know what was going on under the cell casings and take better care of them.
There’s no such thing as a cheap, good battery care unit. Graupner’s Ultramat 25 has a single charging outlet and costs £85 whilst the higher specification, dual outlet Ultra Duo Plus 30 will relieve you of £120. For that sort of money you could buy another model or a good engine, take your loved one out for the night or redecorate half of your lounge. But do you need another model yet? Haven’t you wined and dined her enough recently? Don’t answer that one! Won’t the lounge do for another year? Isn’t it better to take more care of the models you already have? Let’s have a look at the benefits a good battery care unit will bring by looking, first, at its primary functions:
* Charging A unit like this will charge all battery types: NiCad, NiMH, Li-Ion and Li-Po, as well as sealed lead-acid. It’s important to check the number of cells a unit can handle, although the range-topping Ultramat 30 can charge 1-30 NiCad / NiMH cells and 1-10 Lithium cells. Most chargers are delta peak detection units, where the battery state is monitored whilst charging takes place. The LCD display will show time elapsed, pack voltage, number of amps delivered and the charging rate.
* Discharging / Conditioning Cycling battery packs is a good thing to do. Although the ‘memory effect’ phenomenon is still debated, it’s generally accepted that cells that aren’t fully cycled may eventually not discharge properly due to their embedded historic pattern of use. A good charger like the Ultramat will discharge and then fully re-charge a pack in one operation, an excellent feature and especially useful for refreshing a pack that hasn’t been used for a while. The charger will allow charge and discharge parameters to be set.
* Capacity Test The unit will fully charge a pack and then discharge it to a pre-determined level, and at the end of the process the screen will display the pack’s capacity.
* Balancing A useful feature for new packs, which inevitably require several cycles to become fully optimised. The unit will ‘even up’ the condition of the cells and therefore maximise the pack’s capacity.
LI-POs MADE EASY
I’d seen and read all there was on the subject of Lithium Polymer batteries before I bought my first pack. I’d read the warnings and seen the picture of cells igniting, so it was with some trepidation that I hooked a pack up to the charger for the first time. Of course, in reality, I needn’t have worried.
The Ultra 30 makes charging Li-Pos so easy. Simply select the Li-Po charging program and enter the pack’s capacity using the negative (-) and positive (+) keys. Connect the pack to the charger, whereupon it will detect the number of cells in the pack and display that number on the screen. If the charger has detected correctly (and I’ve never known it not to), then press the start button and away it goes. The charger sets the 1C charge rate from the capacity entered and from here reflects the process status on the display. This, I have to tell you, is very reassuring. Safety is always paramount and I charge my Li-Pos in the garage with the cells in a Pyrex dish, fire extinguisher nearby. Mind you, to be honest these precautions seem extreme, such is the ease with which the Ultramat handles Li-Pos. There may come a day when a simple operator error (say, entering an incorrect capacity) leads to a problem so I’ll go on being careful, but in my experience using Li-Pos is simplicity itself.
SETTINGS
Chargers like the Ultra Duo Plus 30 have a number of custom features. For example the NiCad delta peak trigger voltage can be adjusted, the safety timer and (in most programmes) charging rate can be adjusted, and so on. Whats more, the state of the 12V power source for the charger can be checked as charging is in progress. The Ultramat 30 has a second set of charge outlet sockets, which can only be used to charge 4 – 8 cell NiCad / NiMH cells, therefore making the unit perfect for conditioning both Tx and Rx packs prior to flight. I suppose it would be handy to charge two Li-Pos at once but, quite honestly, I think I’d rather monitor just one Li-Po at a time!
WELL?
I hope I’ve managed to convince you about what an important piece of kit this is. One thing’s for sure, I wouldn’t be without my Ultramat 30 – it’s quickly become an indispensable part of my flight set-up, allowing me to see what’s going on under the surface of my batteries. A great reassurance when flying, so if something goes wrong I can at least rule the batteries out of the equation. However there’s one ever-present variable that no form of electronics will ever overcome, something that is truly a ‘loose cannon’ in our hobby and likely to terminate a model for no apparent reason… the pilot!
The Ultra Duo Plus 30 is available from Motors & Rotors (01923 465712).
