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I am making a circuit which is powered by a lipo battery of 11.1V(3.7V*3). I need to check for the lipo's under-voltage so that the circuit automatically switches to a second lipo when the first one drops below the cutoff voltage. I am open to using arduino and relays but no diodes(as they lead to large power loss).

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  • \$\begingroup\$ Success will depend on how much current you draw from the battery providing the load and the hysteresis in detection. When you switch from the loaded cell to the unloaded cell ...the unloaded cell terminal voltage will rise and the loaded cell terminal voltage will drop. It might be better to simply connect your two LiPo's together to get the larger capacity. \$\endgroup\$ – Jack Creasey Jan 22 '18 at 18:38
  • \$\begingroup\$ The problem we faced in connecting the 2 batteries simultaneously was that the discharge rate of both the lipos was not the same. Also, controlling the discharge rate of the lipos externally would lead to power loss. So we were trying to explore circuits that would enable switching between two batteries. \$\endgroup\$ – user175577 Jan 23 '18 at 16:46
  • \$\begingroup\$ If either battery can fulfil your current requirement, how can there possibly be a problem with paralleling them? There could potentially be concerns if the CAPACITY of the LiPos are vastly different, but in large this is controlled by the effective output resistance of the batteries. Since the batteries (paralleled) must have the same terminal voltage, the current shares via the difference in output resistance .....so not sure what problem you see with this. \$\endgroup\$ – Jack Creasey Jan 23 '18 at 16:52
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The problem you are facing has a solution. It is called "Power Path Controllers". Please examine the following portfolio of Linear Technology (now Analog Devices) products, Power Path Controllers and Ideal Diodes, I am certain some ICs will fit your need.

It looks like this one might work for you, LTC4419.

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  • \$\begingroup\$ Thanks for recommending the IC! But we still have a problem- Our device requires a large current of around 40A. But the IC has a very low max current output. Can you suggest some way to tackle this problem? \$\endgroup\$ – user175577 Jan 25 '18 at 16:08
  • \$\begingroup\$ @user175577, if you could be more specific with your requirements, you might have a better advice here :-(. For 40 A you would need to find a controller with external transistors. Look again. \$\endgroup\$ – Ale..chenski Jan 25 '18 at 16:39

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