Charging batteries is surprisingly thrilling…

…when you have the Technoline i-charger (aka La Crosse BC 900).

Refresh mode

One of its best tricks is “refresh” mode, which I shall explain to you. I have many old rechargeable batteries that I had given up as lost causes, as their capacities had dropped to nearly zero. Upon placing the battery in the charger and selecting “refresh”, the charger firstly fully discharges the battery, measuring its capacity as it goes. When the battery is empty (the voltage drops below 0.9V), it then fully recharges the battery (using minus delta voltage detection to tell when the battery is full) and repeats the process. The capacity measurement is compared to the measurement from the previous cycle, and if it has increased, then the cycle repeats again.

It takes a long time, but it actually works. It’s very satisfying to return to the charger and see that a battery that had a 100mAh capacity this morning now has over 1200mAh, and is still rising.

Other remarks

The device has one small shortcoming – if a battery is inserted that has a very low voltage (below about 0.5V, which can happen if a discharged battery is left for a long time) the i-charger will not detect it. The solution is to pop it into a common “unintelligent” charger for a few minutes to get the voltage up. You can then put it back into the i-charger and proceed as normal.

You can select charging currents between 200 and 1000 mA (or up to 1800 if you are only charging two batteries). This gives you the flexibility of fast charging when you are in a hurry, or slow charging at all other times. If you try to charge a battery above its rated maximum and it overheats, the system will shut off the current to that compartment until it has cooled down.

The four compartments can all work independently, so you can swap batteries in and out as appropriate. When a battery is full, it will be switched to trickle-charge to keep it topped up.

Each compartment has its own readout on the LCD screen, which can display the battery’s voltage, the charging/discharging current, the elapsed time since charging/discharging began, and the capacity in mAh.

The consequences of owning a “real” battery charger

My interest in rechargeable batteries has been goaded by the acquisition of this charger. I used to be shy of using rechargeables because I found them unreliable, and so I would usually fall back to good old alkalines. The more batteries that a device requires, the simpler it is to just grab a handful of fresh alkalines, because you can be relatively certain that they all have more or less the same capacity. In a device that takes 4 AA batteries, if one of them has a fraction of the capacity of the others, then you’re headed for misery, and it can be difficult to find out which one is the source of the problem. And even if you do manage to isolate the duff battery, it’s hard to know whether to justify throw it away or not. Maybe it’s not really dead? Maybe it’s just sleeping.

None of that matters now. With the i-charger’s LCD display, I now have a fairly good idea of the condition of each battery. I’m now going through all my old batteries, using the refresh mode to get them back up to their rated capacities. If they won’t recover, then I can add them to the “discard” pile with confidence.

I’m planning to greatly reduce my dependence upon alkaline batteries. Now that I’ve brought some old ones back to life, I have a fairly good stash, and whenever I have the need to replace the batteries in a device in future, I’ll always ask myself “can I use rechargeables in this?”

Can I use rechargeables in this?

Modern NiMH batteries have capacities of 1300 – 2900 mAh, which is roughly the same as alkaline batteries. Back in the days when we were using 650mAh NiCd batteries, you could get much more life out of a decent Duracell, but that is no longer an issue.

However, rechargeable batteries do have a few drawbacks compared to alkalines. Firstly, they only supply 80% of the voltage of an alkaline. This is usually not an issue, but in some devices that take a large number of batteries in series (for instance, a torch), the voltage drop is problematic.

Secondly, they have a self-discharge rate. So in low-drain appliances that you would expect to be able to leave batteries in for a long time (television remote control is the most obvious example) you would find that you don’t get the lifespan that you would hope for. This is an inconvenience in most situations, and life-threatening in others (hello, smoke alarms).

Thirdly, if you attempt to continue to draw current from a rechargeable battery after it is discharged, it may get damaged. Electronic devices like cameras will automatically turn themselves off when the battery is discharged, so we don’t have to worry about this. But “dumb” devices like torches won’t do this. It’s not a problem if you take the batteries out when the light begins to dim, but it’s possible to forget.

It’s not cheap

It may seem that way. You can buy battery chargers for £30 less. Maybe you’ve got one already. But take into account all the batteries that I have managed to rescue already (probably nearly £20 worth already). And take into account all the batteries that will avoid a nasty fate in the future. And take into account the pleasure that I have discovered in charging batteries. For me, it’s the right decision.