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I'm working on a project where mains voltage will sometimes be disconnected, and the system will have to run on battery for as long as possible before doing a (safe) shutdown. The desired behavior is exactly like a laptop battery system:

  1. When mains voltage is connected, charge the battery and power the system from mains
  2. When mains voltage is disconnected, power the system from the battery
  3. Prevent the battery system from supplying current when the batteries are discharged below a certain voltage (to prevent damage).

Is there a name for this type of system, or a name for the feature(s) that I should be looking for when I look at chargers? (If it matters, this system will be 12V, so I'm looking at 14.8V Lithium battery options.)

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  • $\begingroup$ are you looking for a complete working system or e.g. an IC? Most modern ICs allow charging the battery while it is under load (e.g. look here: para.maximintegrated.com/… ). As far as names I think what you're looking for is called a battery management system or simply a battery charger. $\endgroup$ – Guy Sirton Mar 30 '14 at 5:06
  • $\begingroup$ I'm not looking for any system in particular, just the terminology that's used to indicate "you can charge it while it's under load and no smoke will come out". I'm assuming that for such a system, the input voltage, output voltage, and positive battery terminal must be connected to 3 separate pins on the IC. Is that true? What are those pins called? $\endgroup$ – Ian Mar 30 '14 at 19:53
  • $\begingroup$ follow through the link I posted and look at the application notes. The typical arrangement is that the same output is fed to your system and the battery but the charging current is measured on the battery... $\endgroup$ – Guy Sirton Mar 30 '14 at 23:41
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It appears to me that you are looking for some sort of UPS (uninterruptible power supply). You should look for "load sharing" controllers.

Maybe one of these will suit your needs? http://www.mini-box.com/micro-UPS-load-sharing

Regards, Damjan

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  • $\begingroup$ I thought about UPS stuff, but they seem mostly focused on lead-acid batteries where there is no real battery management component. Does load sharing work in systems with lithium ion / lithium polymer batteries? $\endgroup$ – Ian Mar 27 '14 at 15:53
  • $\begingroup$ I see no reason why it wouldn't work. Those are no different from other power supplies in this context. microchip.com/wwwproducts/Devices.aspx?dDocName=en536670 This one for example explicitly mentions Li-Ion and LiPo. Of course, check with manufacturer when in doubt. $\endgroup$ – Damjan Dakic Mar 27 '14 at 19:55
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I found the name of the component: PMIC, or Power Management IC.

To quote from this example:

PMICs seamlessly manage power flow from various power sources (wall adapters, USB and batteries) to power loads (device systems and the charging battery), while maintaining current limits where required (such as that specified for USB). To this end, PMICs typically feature built-in PowerPath control, DC/DC conversion and battery charging functions.

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