[TriEmbed] Designing a LiFePO4 battery charger

[Carl Nobile]

Hey Charley,

We're doing ok, I'm working from home 100% of the time now.

This may not be the exact answer to your issue but it may help. Banggood
has a lot of LiIon battery protection boards. You may be able to use one of
these, it would make the actual charger a bit simpler.

https://www.banggood.com/search/liion-battery-protection.html?from=nav

~Carl


On Sat, Mar 21, 2020 at 8:17 AM Charles West via TriEmbed <
triembed at triembed.org> wrote:

> Hello all!
>
> I hope the virus hasn't affected you guys too badly.  My little family's
> been pretty much staying in our house for the last week and a half (since
> our daughter's preschool closed), but we are doing OK overall.
>
> The work on the sidewalk robot continues!  I'm in the middle of testing a
> brushless motor controller/MCU combination to drive the four hub motors
> that will be moving the Mk3 robot.  If all goes well, it will be built like
> a tank and strong enough that I could ride on it if I wanted to.
>
> The part I'm trying to figure out is battery charging/system protection.
> The motors expect 36V, so I'm putting 3 4s LiFePO4 batteries in series to
> provide it.  What I'm not really sure about is how to integrate a charger.
> Each of the batteries (batteries
> <https://www.amazon.com/gp/product/B07Q7FY8CC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1>)
> is meant to substitute for a 12V lead-acid motorcycle? battery, with its
> own built in cell balancer.  I'm hoping to charge them with power from a
> 24V DC regulator, potentially with a simple 2 terminal charging dock.
>
> The issue I'm running into is that none of the charger ICs I'm looking at
> can handle 12 cells in series (and they would probably require 40V or so if
> they did).  I'm thinking that I should be able to have a seperate charger
> IC for each battery, but I'm not entirely clear on how you would charge
> them in parallel while having them connected in series.  I'm sure you can
> do it, because my other charger does it for Lithium polymer, but I'm not
> sure what the configuration would look like.
>
> If I may ask, do you have any ideas?
>
> Thanks,
> Charlie
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-- 
-------------------------------------------------------------------------------
Carl J. Nobile (Software Engineer)
carl.nobile at gmail.com
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