Radical RC Cycler FAQ’s

Occasionally a battery pack will be returned to me. The customer will tell me it does not check up to snuff on their cycler. I always replace the battery under warranty — I want you to be happy — and I always cycle the pack on one of my regularly calibrated ACE Digipace 1 units. In each case, the battery is in fact good. Usually the customer is using a Hobbico Accucycle. Here is one of the letters I have exchanged. I am happy to warrant your batteries, but please take time to check your cycler before returning a pack. Even if you don’t have a warranty concern, it is a good idea to check your cycler from time to time. The letter below outlines how to do it.

The Letter

Dave’s Reply

John, I have warranted about 4 packs in the last month — never from a crash, but from not cycling up to par. Every one of them was using a Hobbico Accucycle. Every pack tested perfect upon return. Hobbico cyclers are not very good. Many of them discharge at a significantly higher rate than they say, so they give you a false bad-pack reading. Maybe it’s because Hobbico (Tower) likes to sell batteries, I don’t know, but I presume it’s because their stuff is built by the lowest bidder they can find — not much quality control. I use and recommend ACE products. I don’t sell these, so know this is a genuine opinion and not a sales pitch.

I have a good digital amp meter that I use to check the calibration on my cyclers. They do slip adjustment and need recalibrating from time to time — it is not always a sign of inferior quality. A cycler has to be kept right up to snuff at all times. You wouldn’t want your doctor using a faulty heart monitor, and your battery is a required organ just the same.

Get a Good Meter

If you don’t own a good digital amp and volt meter, you might want to think about getting one. This way you can verify what your charger is telling you from time to time. And I don’t mean the $20–$40 cheapies — think about getting the best you can for around $100 and you’ll probably get a good one. If you have a friend in electronic repair, you can check it against his good Fluke meter to see if it’s accurate.

Check the Discharge Cutoff Voltage

Your discharge function should kick over to charge when the pack has reached 1 to 1.1 volts per cell. There’s only a few mAh difference in this adjustment as it falls from 1.1 to 1 in seconds. However, if your charger is cutting off at 1.12 or more (I know it sounds picky, but it’s a big difference), then your cycler is building a memory into the pack. If it’s cutting off below 1 volt per cell, it could ruin a pack. Make this test by patching into the battery pack or wiring harness and taking the measurement while it’s being discharged. You can’t pop the pack off when you see it kick over and measure it then — it’s the voltage under the discharge load that we want to know. If the number is too high, you’re getting false bad readings; if it’s too low, you can ruin or damage a pack.

Verify the True Discharge Rate

Put your amp meter in line with a pack. Make a harness or set of jumpers so one leg of the charge has to go through the meter to get to the pack. Be careful to set the meter correctly — if you have it set at the 50mah range, you could blow a resistor and ruin that range. Set it at the closest range to 300mah or more. Note the discharge rate when you first start discharge on a full pack, in the middle, and at the end of discharge. It should be exactly the same (within 1%) no matter the pack voltage as its state of charge declines. If it’s higher than 250 (what the Accucycle is telling you) then you’ll get lower-than-reality readings and tend to fault a pack too early. If it’s below 250, you’ll get much-better-than-reality readings and tend to use packs too long. Once you know the number, it’s OK if it’s 220 or 275 or whatever — with the true number known you can plug it into your equation and get the true capacity of your pack. That’s what you really want to know.

You need to know the true capacity of the pack if you’re going to be accurate on the 80% rule. For me, I get rid of them long before they’re down to 80%, and always replace a pack no matter how good it rates if it’s 3 years old. Many do this every year. I think that’s a little excessive, but everyone has their own opinion on batteries.

Probably these Hobbico cyclers are just all over the scale — some right on, some high, and some low. Of course, if a customer cycles an 1800 pack and gets 2045 out of it, they just think they got a special good pack and never contact me. I only hear about the low-reading units, for that reason. But I get just as suspicious of my cyclers if one reads very much too high.

With your cycler in line to test the discharge rate, you can also test the charge function. Use the same principle and note the number at low battery, mid charge, and full charge to see it’s staying the same.

Calculating a Full Charge

You have to put at least 140% into a NiCad to fill it up. I always figure 160% so I have a little safety margin to make up for inaccuracies and packs with slightly different personalities.

Once you know the true charge rate of your charger, you can figure out by the 140% rule how full you were getting your pack.

A Word on Factory-Rated Packs

Many factory radio packs are rated 50 to 100 mAh below the true cell size. Some will be tricked and think that because the factory pack cycles right at rated capacity the cycler must be OK. This is no way to test your cycler. Manufacturers cheat the number down a little to sucker people into using marginal packs and not returning for warranty. Not saying they all do it, but I’ve seen it many times.

And last of all — you could just have a bum pack. I have yet to take one back that did test bad, but I’m sure there will be a first time. I don’t expect to sell hundreds of packs and every one be perfect. Providing warranty service is just part of being in business.

I hope I didn’t tell you too much of what you already knew. You could be an expert and I’d have no way of knowing — I just wanted to cover all the basics. It’s important to determine the exact reason for any failure to be sure it doesn’t happen again. If you don’t have the expertise or equipment to check your Accucycle, you can send it to me. I’ll check it out and give you the numbers, and could return it with your new pack.

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