You’ll notice if you look in the battery cavity that there are two metal contacts off to the side (one short fat one, and one tall skinny one): the reason for this is that the backlight circuit runs parallel to the rest of the circuitry and is driven only by the top battery.  Conversely, the bottom battery drives only the display (and corresponding circuits).  If you’re doing most of your timing with your Interval during daylight and not using the backlight, the battery for the backlight is probably going to have plenty of juice left on it.  The same goes for SpeedCoach Gold and StrokeCoach Surge use – if you don’t use the backlight very much, it probably has some extra energy.

As a result, if you’re in a pinch, trying to get by for a little longer without having to stop at that local electronics store, or our booth at a regatta, switching the two batteries around should help to give you a little more battery life for your NK product!

The approach for everything is similar: use logic, and a system of known variables and unknown variables to deduce what’s not working.  Specifically, taking a control unit (whether it is Cox Box or SpeedCoach) and put it in one boat to test it.  If it doesn’t work, test the same control unit in a different boat.  From here you can determine whether the unit is the cause of the issue or if it’s a boat wiring issue.  Typically with unit malfunctions we recommend calling NK Technical Support (and short a few specific diagnostic questions depending on the control unit, I still recommend this).  However, with boat wiring issues, there are some more things to look at.  Age of the wiring, and salinity of the water where you practice are two relatively important issues to consider when thinking about malfunctioning wiring.  Also it is important to inspect the wiring where it meets the connector to the control unit to be sure the wires haven’t stressed and broken at this point (plug for Cox Box or wiring harness dock for SpeedCoach).

There are some specifics I would also like to mention in the hope that they help someone: try different microphones if the problem is with a Cox Box/microphone combination; if the SpeedCoach isn’t recording splits or distance properly, check the calibration factor of the unit, as well as the impeller on your boat; and lastly, if you get confused, write things down – it always helps me to see what’s going on if I make notes as I’m working on a boat!  Good luck with your diagnostics!

If you run into any issues along the way, don’t hesitate to contact NK at techsupport@nkhome.com for help.

Anyone who has sent in a metal can style Cox Box knows that the cost to open and clean the unit and replace the battery is $145. The cost to replace the battery and repair damaged connections and parts is $245 (about half the price of the Cox Box itself). However, even if we repair failed parts, many others are still the original equipment with hours of use and even abuse. Although we give the unit a full functional check after repair, there’s no way we can guarantee that a part that wasn’t replaced won’t fail a few months later.

An analysis of Cox Boxes returned to NK in the last year showed that the majority of Cox Boxes we repaired were six to seven years old.  Most of these units were on their second trip through our shop (with steady use, sealed can Cox Box batteries provide three to four years of full capacity performance.) Many of these repairs also included a P5 and a BNC replacement, putting them at the $245 level. Many customers considered a trade-in at this point, but opted for the repair in the belief that it was the more cost-effective approach. Further analysis shows that this decision may not adequately account for the financial benefits of upgrading to the new style Cox Box.

One of our major goals with the new Cox Box was to minimize the scheduled or expected maintenance, and to maximize the years of use with no trips back to the NK shop. The user-replaceable batteries allow you to just buy a new battery pack after a few years of hard use, and the durable P2 microphone connector reduces maintenance and repairs on the Cox Box and the microphone.  And remember, when you trade up to a new Cox Box, you get a brand-new two-year warranty on the entire unit.  So, we compared the total cost of ownership over fourteen years of doing that second repair versus moving up sooner to a new Cox Box: 

As you can see, the total cost differs less than the cost of one unisuit or a few box lunches. Plus, you’ve enjoyed two more years of warranty coverage and the benefits of the new Cox Box including longer battery life, battery status indicator, ability to swap to a back-up battery, rubber bumper protection, lighter weight and full buoyancy.

While we cannot guarantee that every Cox Box will experience exactly the same life-cycle as we have outlined above, this represents the most common scenario we see with Cox Box units in typical two to three season use. We hope this illustration is helpful next time your club or school is facing the “trade-in or fix” question.

(Note also that the typical life span cost of a Cox Box and microphone is only about $100 a year for hours and hours of use.)

If you have questions about any of the products that were used to track results please feel free to contact Ben Churchill or see our entire line of Rowing products >