Can I charge my phone with a power bank that's 10 years old?

Lithium batteries lose capacity after about 300-500 charge cycles, so a decade-old power bank is definitely running on fumes - it might only hold 50-60% of what it originally could. The real risk nobody mentions much is that old batteries can swell or fail unpredictably, and if it's been sitting in a drawer the whole time, you won't know how unstable it's become until you actually try using it. Technically it might still trickle-charge your phone, but honestly I'd grab a new one for the sake of not having a potential fire hazard in your bag.

Does it still hold any charge at all? If it does, sure, you can technically use it - but honestly I'd be cautious about leaving it plugged in overnight or unattended. Batteries that old can develop internal issues that aren't obvious until something goes wrong, and I've had a sketchy old power bank get uncomfortably warm while charging my phone once, which was enough to make me toss it. If it works fine in short bursts, it's probably okay for emergencies, but if you're relying on it regularly, grabbing a new one is worth the peace of mind.

If it still charges at all, go ahead and use it for emergencies - just don't expect much juice. The real trick is testing it safely first: charge it fully, let it sit for a day unplugged, then see how much it actually delivers to your phone. That'll tell you if it's worth keeping around or if the battery's basically cooked. If it gets warm while charging your phone, that's your sign to toss it.

The safest move is to charge it somewhere you can keep an eye on it, not stuffed in a drawer or under your bed while you sleep. I had an old power bank sitting around for ages and eventually gave it a try - it still worked but held maybe a quarter of what it used to, which honestly wasn't worth the desk space. Since you're thinking about using it, I'd say test it first by giving it a full charge and seeing how many times it can actually top up your phone before it's drained. If it barely makes a dent, you know it's time to replace it.

The big thing folks often miss is that even if it charges your phone, an old battery can be unpredictable - it might work fine one day and then overheat or cut out mid-charge the next. Your phone's actually pretty safe from damage, but the power bank itself is the wild card, so test it on something you don't mind babysitting rather than leaving it unattended.

Don't rely on it as your main charger, and definitely don't leave it plugged in unattended for hours. I tried using an old one I found in a drawer a while back - it still technically worked but the charge dropped so fast I basically got nothing useful out of it, and the thing got weirdly warm. Your best move is test it in short bursts during the day to see if it holds anything at all, but honestly for the price of a new one these days, you're probably better off just replacing it and not worrying about whether the battery might do something weird.