It's a given that something under your Christmas tree has a little 'batteries not included' note no-one spotted while wrapping it up. No problem if you keep alkaline batteries in the drawer, a little more irritating if you save money with rechargeable batteries because those NiMHs you have are almost certainly pretty flat.
iGo says most rechargeable batteries discharge themselves in 90 days (there's a chemical reaction fizzing away in there, just slowly when they're not plugged into anything). It also says that's not a problem with its Green rechargeable alkaline batteries. We got out the multimeter to check.
How green are the iGo Green batteries? Actually, they're rechargables you're likely to use, because they'll have a charge when you need them.
Testing some rechargeable batteries that had been in a drawer for rather more than three months gave variable results, ranging from 0.7 to 1.2v. A full charge is 1.5v for an AA or AAA battery and that's what we measured from the iGo batteries (1.577W for a AA, 1.567 for a AAA); they arrived fully charged and two weeks later the power measurement was exactly the same.
Our older NiMH rechargeable batteries charged up to 1.469v for a AA and 1.453v for a AAA and after just a week back in the drawer that had dropped to 1.387 and 1.36v respectively. The battery that only had 0.7v was a USBCell rechargeable; the end pops off to reveal a USB connector so you can recharge it from any PC. That's handy but reduces the capacity so it charged up to hold 1.313v and in a week that dropped to 1.29v.
And a charge of 1.2v doesn't mean you'll get that much power out under load for more than a couple of minutes; a partly discharged rechargeable battery won't sustain the power it shows on the multimeter when you use it. We haven't been able to test iGo's claim that their rechargeable alkaline batteries will deliver a full charge seven years after you charge them, but when they showed a full charge, that's what we got when we plugged them in.
The difference is that the iGo batteries are alkaline batteries; the same technology as non-rechargeable batteries which also hold their full charge for a long time, but with some changes to the chemistry so you can recharge them without internal gases building up to cause them to split open (that's very likely if you recharge standard alkaline batteries and can mean leaking battery fluids or a bang, depending on the amount of energy released). You have to use the iGo charger (a NiMH charger won't deliver the correct amount of power), but this can also charge any NiMH rechargeables you have.
A full charge takes the same 12+ hours as a NiMH charger, topping up the batteries when partly charged (which extends the life of the battery, in terms of how many times you can recharge it before it stops accepting a full charge) takes a couple of hours depending on how much charge it has already. When you do give up on a battery and throw it away, you can recycle it like a standard battery and it has no mercury or cadmium to pollute.
The iGo batteries are the same price as rechargeable NiMH batteries -- £7.99 for a pack of four, £12.99 for eight -- and the four-battery wall charger costs about the same as most two-battery NiMH chargers (£15.99 with four batteries). There's also a two-battery charger you can plug into a USB port; it's small enough to be convenient for travelling although given how well these batteries hold charge you'll only need it if you know you'll use up the batteries.
The USB iGo charger
As physics doesn't allow for the concept of a free lunch, there has to be a drawback. These aren't high-capacity batteries that will power high-draw devices like the few digital cameras that still use standard batteries. But they're ideal for remote controls, game controllers, LED and Christmas lights, pocket recorders, torches, internet-connected scales and the like, and they'll still be useful for anything that needs a battery next Christmas as well.