It’s seems it’s a fact of life that you end carrying around a variety of battery powered gadgets nowadays, cameras, GPS receivers, flash units and the like so you end up carrying their support stuff as well which is basically batteries. I’ve had a Canon A95 camera for years powered by AA batteries and very quickly started to use rechargeable batteries for it because it looked like buying normal disposable batteries was going to be both expensive and environmentally damaging. More recently I’ve got a Garmin Oregon 550t GPS receiver as an update for an older Garmin Etrex Vista Cx both of which use AA cells. I’ve been buying Energizer NiMH AA rechargeable batteries for a while and I’ve accumulated 16 of them along with 18 other assorted AA and AAA NiMH cells, I’ve probably got more but it was those 34 cells I found when I made a quick search the other day.

batteries….

NiMH is an abbreviation of nickel-metal hydride and is a rechargeable battery technology that’s largely replaced nickel-cadmium (NiCd) cells in common use basically because the NiMH cells can have two or three times the capacity of the older NiCd cells. Normal, disposable, batteries are based on a reaction of zinc and manganese dioxide (Zn/MnO2) and are generally known as alkaline cells and nearly always are not rechargeable.

Typically you can buy AA NiMH cells with capacities ranging from 1100 mAh to 2900 mAh, this measure (milliampere-hour) gives you an indication of how much power the cell stores. An imperfect analogy would be that it’s similar to a measure of the capacity of a petrol tank on a car, how far your car will go on a single tank obviously depends on the size of the tank along with simple issues such as if you’re filling the tank when you refill or only half-filling it and of course how efficient your car is! Basically, the higher the number of of mAh your battery holds when you put it in the the GPS, for example, then the longer the GPS will last.

NiMH batteries are particularly good for electronic gadgets compared to alkaline batteries because of their very flat discharge curve. An alkaline battery typically delivers 1.5v when new but that quickly degrades and can fall below 1.0v or even to the point where chemical damage is caused to the cell. By contrast a new, freshly charged NiMH cell will deliver 1.4V or 1.45V initially but then will run for 80% of the discharge cycle at this level.

You can look at this two ways, for example in a torch you’ll see it potentially brighter with an alkaline cell initially but the light will fade fairly quickly and ultimately it will fade to nothing while a NiMH cell will start slightly less bright but then remain pretty much constant until the battery runs down. Another application though is in the sort of electronic gadgets that require consistent voltage levels to provide clock cycles on processor chips or to control access to memory devices, here you’ll get a short life from an alkaline cell as it will drop below a useful voltage fairly quickly while the NiMH cell providing the required voltage level lasts longer.

While I’m on the subject I ought to mention avalanche transceivers, it’s frequently quoted that they cannot use rechargeable batteries without any reason being given. The problem is that they often use crude battery meters which measure terminal voltage to give an indication of battery strength/life. This works well with alkaline batteries which have a consistent discharge rate with voltage but doesn’t work with NiMH which have this flatter discharge rate. This accounts for the rather breathless accounts you hear from people who describe how their transceiver suddenly went from showing 80-90% battery strength to 0-20% in a few minutes while using rechargeable batteries. So I’d suggest it turns out your transceiver actually runs rather well on modern rechargeable batteries doing it’s main business but because you cannot measure how much power you’ve got managing batteries with NiMH in this application is too problematic and potentially very dangerous. This applies equally to clever modern cells such as the the newer lithium batteries, a discharge curve that’s ideal for gadgets in principle but problematic in this particular application.

my batteries…

I’ve noticed a couple of times recently that I’m getting a variation in the time I’m able to run the Oregon GPS before switching apparently identical batteries around, it’s not too serious and I always have some spares but I’d begun to think I needed to identify these weaker cells and replace or retire them. The only other tool I have to measure the batteries is a simple little battery test which measures the voltage on the (unloaded) terminals. This isn’t very good for NiMH cells, this feature of NiMH where they’re delivering high voltages for about 80% of the discharge cycle means a terminal voltage reading is hard to interpret.

When I started to look around for replacements I came across the idea of getting a battery conditioner or a more sophisticated charger which might revive some of the batteries. And that’s how I found the BC900, it’s sold under a couple of different names but generally keeps the model number BC900. The one I have is German and badged as Technoline but La Crosse also have the same unit.

This little gadget is pretty feature packed and it’s hard to know where to start. The highlights are :

• Works with all NiCd and NiMH “AA” and “AAA” Rechargeable Batteries
• LCD shows capacity for each battery when charging is complete
• Charges AA & AAA rechargeable batteries simultaneously
• Will not charge defective batteries
• Select different charging current for each channel
• Automatically switches to trickle charge when charging is complete to ensure maximum battery capacity
• Overheat detection to protect over-charging
• Charge Mode (charging current)
• Discharge Mode (discharging current)
• Refresh Mode (time elapsed)
• Test Mode (accumulated capacity)
• Input Voltage for AC/DC Adapter:100-240 VAC
• Charging Current Range:200 mA – 1800 mA

The normal Energizer charger I have isn’t so bad but it’s pretty basic compared to this, the Energizer basically pumps a standard current in to all cells at the same time regardless of their state. It works on a timer so it shuts off after 8.5 hours to prevent serious overcharging but in fact I can calculate that the 2500mAh cells I’m using will actually charge in around 6.9 hours.

The BC900 has four modes of operation, charge, discharge, test and refresh. Charge and discharge do what you’d expect with the feature that the power can be varied so cells can be slow charged or rapid charged as required.

The most interesting mode, for me, is the refresh mode. Basically this charges and discharges the individual cells repeatedly until no increase in charge is registered. Not only does this refresh your cell but you can identify the weak cells. This does take several days continuous running to achieve of course. What we’re trying to defeat here is what’s commonly known as a memory effect but more properly is termed as a voltage depression, this is the situation where repeated charging while only partially discharged reduces capacity. Repeated charge/discharge cycles ought to fix this.

If you look at the two photo’s above you can see what happened when I refreshed a set of 4 cells. The cell on the left seems to have a problem, in one display you see that while three cells have charges of 2.33 – 2.38 Ah, or around 90% of new capacity, the one on the left is only at 1.921 Ah despite being charged for the same time (around 77%). Even the terminal voltage isn’t quite as good and the difference here would have been too subtle to detect on my battery meter.

The first thing I realize is that I want to keep track of this data, my first thought is to write some PHP code and use a MySQL database but I resist the urge and figure that for 34 cells a spreadsheet will probably be good enough. This is an excerpt of the table :

I’ve used some conditional formatting in the spreadsheet to calculate charge in relation to the original charge and color code anything over 90% as being good, 80-90% as marginal or yellow (not shown) and below 80% as red or below standard. Obviously what I’ve also done is stick little labels on all the cells so I can identify them. My plan is to refresh cells once or twice a year and monitor the capacities to more suitably make sets of similar capacity and to retire any cell that’s below a reasonable standard.

In fact, I still think this weak cell might be rescuable. I’ll no doubt have some more in a similar state so I’ll put them on charge/discharge cycles and see if some life can breathed back into them.

So far I’ve run the charge at the default level which is 200 mA, that’s pretty conservative though and you ought to be able to charge at a rate between 0.5C and C (where C is the capacity) so in this case the rate of 1000 mA is possibly appropriate, it’s certainly going to be much quicker. The problem here is that I’m worried about heat generation, there’s an over-temperature setting but I’d rather not overheat the cells or have the over-temperature trigger without a full charge to the cells. There are some downsides to using a low charge rate with some cells, the smart charger can detect an end of charge signal which is stronger at higher charge rates, some BC-900 users report charges not terminating when using 200 mA charging. That’s not happened to me, the charge is terminating and the batteries are cool to the touch, I’ll probably step up to a 500 mA charge rate which should significantly reduce the refresh time.

conclusion….

I’d say this is a great bit of kit, it’s certainly ideal for the outdoor gear geek but it’s a good way to manage the ever increasing number of batteries we seem to carry. How this genuinely works for cost is hard to say, it’s around £40-45 to buy the unit while a set of 2000+ mAh AA NiMH cells is £8-10 so you need to rescue a few cells before you get payback that way. Another angle though is convenience, if you’re on a trip then taking a couple of good sets of cells is better than taking 4 or 5 sets that might be marginal, it’s obviously lighter but it’s easier than keep trying to charge sets of cells all the time when you may not have access to mains power.

I think if you matched sets of cells together, labelled them up, tried to always fully discharge them and used a clever charger than always discharged you could save a small cost compared to the BC900 but it would be rather inconvenient.

I was also satisfied to see that my guess about having some slightly defective cells in my collection was proven by the first set I placed in the BC900 so it confirmed it was a good idea to buy the BC900 for me.

An update to my post of a few days back, I’ve done some more testing with this which reveals some interesting things but sadly not anything that gives me a working installation.

First, I tried to install the current version in Windows XP and Window 7. In Windows 7 my system just crashed totally which is a first, so SwissTopo have actually managed to produce some software that give me my first ever Windows 7 system crash which is not a great first really.

In Windows XP I was able to use the current installer and then install sector one of the Swiss Map 25 followed by Swiss Map 50 and to run the software. But, I found the exact same problem I had with printing on the Mac was also occurring on XP. In some ways this isn’t surprising, it’s basically the exact same software running through an interpreter but, on the other hand, I’d thought the problem was due to an external conflict so it seems odd the conflict exists on two entirely different operating systems. My XP installation is pretty scaled down, I only installed it recently in a VMware virtual machine so there’s no accumulated rubbish on the machine and there’s no installed applications apart from Microsoft Money and Firefox.

Odd though it seems I reasoned it might well be possible for this conflict to be on both platforms, there’s some common things between them, for example I’ve got Mozilla Firefox installed on both systems and, particularly interestingly, some Adobe components like Flash plugins and Acrobat. However, removing those things from the XP system doesn’t really change the problem so I tried another approach.

If, on Windows XP, I use the install disk for Swiss Map 25 sector One which is software version 1.0.3 build 54 then it works OK running the software from the disk without installing it. This is about as old as the Swiss Map software gets, I think it’s the initial version in fact. I then installed this version onto my XP system and found it still worked satisfactorily.

That’s not as useful as it seemed though, I need to install the Swiss Map 50 maps which requires a later version. The SwissTopo website is confused about this, they claim that version 1.2.3 (Build 87) is the first released version that supports Swiss Map 50 but the DVD actually ships 1.2.1 (Build 85) which is supposedly an unreleased, internal version. Regardless of that confusion in turns out that 1.2.1 (Build 85) doesn’t work.

Although this is interesting I can’t find a way to use the information to be able to actually print all the maps I need. It looks like it’s unlikely there’s any workaround I can make on my systems to get printing to work for both Swiss Map 25 and 50. But, it does look there’s an issue the SwissTopo could address if they were motivated to do so, if it works on version 1.0.3 build 54 and doesn’t work sometime after 1.2.1 (Build 85) then, in a nutshell, they’ve broken something along the way with their packaging and they ought to be able to fix it.

In terms of support, I reported this back on the 29th April, a few days later (3rd May) I got a mail suggesting I try removing a file (smusrpre.smp) which seems to be their standard response to pretty much any problem. I was away so I didn’t reply until the 7th May to report that removing this file didn’t work. I didn’t get a response from that or from the followup I sent late on 10th May.