I realize this is a very obscure question so bare with me. I am trying to help a friend who is in a wheelchair to charge her cellphone from the batteries on her wheelchair. I picked up for her a small power invertor with usb so her cell phone can be charged. The model is designed to run off the cigarette lighter in the car, which is 12 V. The chair is powered by 2 x 12V in series (according to the website). I am asking if I can shunt the power inverter over one of the 12 V batteries. Will this significantly affect performance, charging, and battery life?

Thanks
jordan.vince

 

I think you can connect the inverter to one of the 12v batteries and not notice the tiny amount of power it will suck to charge a cell phone. Of course, thousands of people will immediately say that this will unbalance the charging of the batteries, so, add a switch to swap which battery you charge the phone from. Double pole, double throw would work.

If you're really smart, you can connect to the 24 volt level and use a regulator to reduce the voltage to 12V. It wastes more power, but draws evenly from both batteries.

 

Thank you for your thoughts on the matter. You have given me some food for thought.

jordan.vince

 

Just tap 12 V from one of the wheelchair batteries and connect there the cell phone charger for automobile use. You can mount a cigarette lighter socket also. The battery will not notice the tiny amount being 'borrowed'. Forget about a power inverter, and no 'modifications' are needed.

 

Me, I'd use a 7805 regulator IC, powered off the 24V supply for simplicity, to provide a 5V USB socket (power only). That way, the user has a versatile onboard 5V supply that can charge a cellphone, iPod, whatever.

The 7805 will need good heat sinking to be able to provide useful charging current. If a 12v supply is readily available, use that and much less heat sinking will be needed. I just have my 7805 screwed to the inside of an Altoids tin, for use in the car. It gets hot to the touch when charging my Blackberry, but it's lasted several years now.