<div dir="ltr">Charlie,<div><br></div><div>As Pete mentioned, isolating the two power sources using Shottky diodes inline with each power source is a good way to go if you can spare the diode drop (and lost useable voltage range) on the battery pack. The article below goes into more detail on configurations of OR-ing diode configurations and using active diodes (controlled MOSFETs) to reduce the voltage drop when running from a battery pack.</div><div><a href="https://www.maximintegrated.com/content/dam/files/design/technical-documents/design-solutions/ds50-cut-your-losses-with-an-ideal-diode.pdf">https://www.maximintegrated.com/content/dam/files/design/technical-documents/design-solutions/ds50-cut-your-losses-with-an-ideal-diode.pdf</a></div><div><br></div><div>Several vendors offer active diodes or smart diodes for use in power OR-ing or solar panel applications. The TI SM74611 looks like it might fit the bill. One of those for each power source and your sources are isolated with a forward voltage drop of 26mV at 8A. <br></div><div><a href="https://www.digikey.com/product-detail/en/texas-instruments/SM74611KTTR/296-35688-1-ND/3911155">https://www.digikey.com/product-detail/en/texas-instruments/SM74611KTTR/296-35688-1-ND/3911155</a> <br></div><div><br></div><div>Good luck!</div><div>Shane</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Feb 18, 2020 at 1:17 PM Pete Soper via TriEmbed <<a href="mailto:triembed@triembed.org" target="_blank">triembed@triembed.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>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.<br>
</p>
<p>-Pete<br>
</p>
<div>On 2/18/20 1:10 PM, Charles West via
TriEmbed wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>Hello!</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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?</div>
<div><br>
</div>
<div>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. <br>
</div>
<div><br>
</div>
<div>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? <br>
</div>
<div><br>
</div>
<div>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?</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Charlie<br>
</div>
</div>
<br>
<fieldset></fieldset>
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