I’m truly no electrician, but when I received my new electric wheelchair a few years ago, I asked my orthopedic technician whether he could attach a USB connection to the wheelchair battery to enable me to charge my smart phone.
My question fascinated him, but also left him a bit unsure, and so he replied:
No, that’s not possible. The electric current used is not the same.
He tried to explain in more detail, but with my rather basic knowledge gleaned from schoolroom physics, he suspected that I wouldn’t grasp what he was saying. At the same time, I didn’t want to be satisfied with a “No” and therefore I asked him whether he couldn’t just attach a cigarette lighter, like the one found in cars, to the battery.
I was surprised when he responded without hesitation that there would be no problem doing that.
Well, I still don’t know why it is not possible to have a direct USB port when there is no problem with a cigarette lighter, but an electronic store will sell regular USB connections for cigarette lighters in cars. So I bought one for € 5 and am now able to re-charge my smart phone with the wheelchair battery without a problem.
By the way, at conferences and trade shows this is a great hit. More times than I could count I have now lent my connection to trade-fair visitors desperate to access electricity.
And my wheelchair battery doesn’t suffer from this in the least. Compared to the wheelchair’s electric motor, a smart phone needs so little power that it hardly signifies.