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Hot swap controller

cc85

Apr 25, 2013
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Apr 25, 2013
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Hello, I am trying to design a controller to manage three batteries that can be inserted and removed at any time and the power output is unaffected while there is at least one battery connected.

For two of the batteries there are buttons that have to be pressed before they can be removed so for those I understand how to make it work.

I am using mosfet transistors to turn power sources on and off so I can measure the voltage of each battery independently. This is controlled using an Arduino.

For the other battery which is higher capacity but the same voltage doesn't have a switch and can just be pulled out. So I was thinking can I have that and one of the batteries (if present) connected together in parallel so it the higher capacity battery is removed then it will default to the other battery. I don't want any one battery charging any others as this can give unexpected depletion of batteries. Can I use diodes for this or will it give too much heat dissipation under large loads?

Or is there a much better way of doing this?

Thanks for any help!
 

Harald Kapp

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Nov 17, 2011
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Don't connect batteries in parallel without some protection. When you insert a fully charged battery next to a discharged battery, a very high current will flow and possibly destroy one or both batteries.
A very simple means of connecting batteries in parallel is by using Schottky diodes to decouple the batteries at the cost of a small voltage drop (~0.3V).

You may want to have a look at this thread with a very similar topic.
 

cc85

Apr 25, 2013
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Apr 25, 2013
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Thank you Harald! Makes sense. I will look through that thread now.
 
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