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Help for design of a battery management system

Hello,
I'm an inventor trying to prototype a PCB for a consumer electronics invention that would use a rechargeable battery (such as Lithium-Ion).  Since your company sells battery management chips, I was looking for some technical guidance and design advice.
Attached is the sketch of the concept as I understand it.  I'd like to have multiple options to deliver the charging or powering voltage (USB, Micro-USB, etc..., so the incoming voltage would be be 5V).  Then this would feed into a battery management chip that would monitor the status of the battery and charge it if necessary.  As for the battery itself, it will provide an input to a regulator to step down to 3.3V for standard electronic components.  At certain times, an output from the electronics will open up a transistor that connects the battery to a motor that can run on 5V - 12V.  So the nominal battery voltage can be anywhere in that range, but I'm leaning towards something like this.  As an optional function, I'd like the system to also be able to charge an external device off of the battery through a USB connector.
So my questions are:
1) Does one battery management chip generally fulfill all requirements (overcharge protection, etc...) for safety certification of a consumer electronics device?  Additionally, can the same chip also monitor battery life?
2) Do you carry a battery management IC that can support multiple charging inputs from two different connectors and switch between which one is available?
3) Do you carry a battery management IC that can step up a 5V input voltage to charge a battery with a higher nominal voltage?  Or in the case of the linked battery pack, how should that be charged?  As one 7.2 V cell?  Or another way?
4) Is it possible for a battery management IC to charge an external device through the same port that it can be charged through?  Or would that require a separate port, as I have in my sketch?  Would that port require an "output" battery management system to make sure it's not drawing too much from the battery, or is a 5V regulator to a USB PCB connector like I have the right way to do it?
5) Do you have any recommendations for any other rechargeable Lithium Ion battery or battery pack that would fit these specifications?  The motor can draw 500 mA - 1A at peak startup and around 200 mA when running, and I'm hoping to get somewhere between 2-5 Ah out of the battery.
Given these specifications, do you have any battery management IC/battery combinations that would work?  At this stage, I'd only be prototyping, but this will hopefully lead to much larger production runs.
Thanks,
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  • Thanks for the detailed response.  For simplicity now, I think I'll nix the option of charging another device, as well as running on the USB power.  I want to focus on the basic function of charging and monitoring a Li-Ion battery.  Two Li-Ion batteries in series (7.2 V) should be the voltage I need, I won't need to go higher.

    So one question I just want to make sure of, if I buy a battery pack like this one, where the two cells are in series and you can't monitor the middle point, are the batteries likely to go bad quicker than if there was battery balancing?

    Assuming I can still use that battery pack, I looked at some of the great resources you sent me, and came across the LTC2943 and LTC2943-1.  They seem made for measuring exactly the kind of battery pack I want, and the last page in their datasheets led me to the LTC1732-8.4, which also seems like the perfect charger, except it can't run on USB voltage.  Are there any chargers that run on 5V but will charge 8.2V battery packs?  I think something like the LT1512 or LT1513 should work right, although it would be a bit more complicated because I need to design the external components for the charging profile I want.  I think the only circuit I'd need would be that one on the last page of of the LTC2943 datasheets but with one of those chargers instead? Unless there's a chip that does both charging and gauging, but I'm assuming that would be rare for one that can take a 5V input and charge 8.2V.  Are there any chargers or gauges that monitor temperature also?

    If buying the battery packs like that are worse for the battery and it would be better to get two separate cells, then I'd look into that.  Is it common to find a charger that will also balance the 2 cells (keeping in mind I want it to run on 5V also)?

    Also, as a battery monitoring novice, I see that the LTC2943 will give my microcontroller all the information I'd want to know about the battery - the voltage, current, charge accumulation, etc...  But how do I take that information and conclude a percentage "battery life" from all that information?

    Thank you very much!

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  • Thanks for the detailed response.  For simplicity now, I think I'll nix the option of charging another device, as well as running on the USB power.  I want to focus on the basic function of charging and monitoring a Li-Ion battery.  Two Li-Ion batteries in series (7.2 V) should be the voltage I need, I won't need to go higher.

    So one question I just want to make sure of, if I buy a battery pack like this one, where the two cells are in series and you can't monitor the middle point, are the batteries likely to go bad quicker than if there was battery balancing?

    Assuming I can still use that battery pack, I looked at some of the great resources you sent me, and came across the LTC2943 and LTC2943-1.  They seem made for measuring exactly the kind of battery pack I want, and the last page in their datasheets led me to the LTC1732-8.4, which also seems like the perfect charger, except it can't run on USB voltage.  Are there any chargers that run on 5V but will charge 8.2V battery packs?  I think something like the LT1512 or LT1513 should work right, although it would be a bit more complicated because I need to design the external components for the charging profile I want.  I think the only circuit I'd need would be that one on the last page of of the LTC2943 datasheets but with one of those chargers instead? Unless there's a chip that does both charging and gauging, but I'm assuming that would be rare for one that can take a 5V input and charge 8.2V.  Are there any chargers or gauges that monitor temperature also?

    If buying the battery packs like that are worse for the battery and it would be better to get two separate cells, then I'd look into that.  Is it common to find a charger that will also balance the 2 cells (keeping in mind I want it to run on 5V also)?

    Also, as a battery monitoring novice, I see that the LTC2943 will give my microcontroller all the information I'd want to know about the battery - the voltage, current, charge accumulation, etc...  But how do I take that information and conclude a percentage "battery life" from all that information?

    Thank you very much!

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