[TriEmbed] Battery charging while under load

Pete Soper pete at soper.us
Tue Feb 18 12:17:36 CST 2020


You typically use a schottky diode that can handle the current with a 
low voltage drop to keep current from flowing in an unintended 
direction. It isn't immediately obvious how your batteries could go flat 
with the charger connected and the system running, but an ammeter can 
help you determine how much current is going where in the various 
scenarios. Maybe the charger is being tricked into turning off? Hard to 
guess.

-Pete

On 2/18/20 1:10 PM, Charles West via TriEmbed wrote:
> Hello!
>
> I'm still working on my robot project and I'm starting to make 
> tentative steps toward something other people could actually use.  
> There are a few open problems remaining, but there is one in 
> particular I was wondering if you guys might have any ideas for.
>
> How do you make a LIPO battery system that acts like your laptop?  In 
> particular, how can you make it so you can run your system off of 
> adaptor power when it is plugged in/charge the battery and then 
> automatically switch to battery power when the adaptor power is removed?
>
> I've tried in the past just leaving my system plugged in while the 
> battery was charging with an external charger.  The result was dead 
> LIPOs.
>
> The typical LIPO pack has 2 thick wires coming out with all of the 
> cells (3 or 4 in my case) in series and a smaller JST connector which 
> exposes each of the cells in parallel.  My first thought is that you 
> could have your adaptor voltage higher than the battery series voltage 
> and use one or more reverse current protection circuits to make the 
> battery stop discharging in that case and apply power to the charger.  
> Does that make sense as an approach?
>
> They also have battery management ICs (such as the Maxim line) which 
> include charging, but I'm not sure if they can handle the level of 
> current that the motors could draw.  What do you guys think?
>
> Thanks,
> Charlie
>
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