[TriEmbed] Designing a LiFePO4 battery charger

[Charles West]

Hey Carl!

I'm glad to hear that you are doing well.  The 12v batteries have built in
balancers/protection.  It's isolation for charger that I'm trying to figure
out.  I think I have a potential solution (
https://drive.google.com/file/d/1JxSStAuKn-OMZUCreYQjGUVy5fR2ADpU/view?usp=sharing)
with the NMOSFETs between each battery needing a high side driver.  The
idea is that when the batteries are operating normally, you turn on the
between battery mosfets and disable the to ground mosfets, then inverse for
charging.

Does that make sense to you guys?

Thanks,
Charlie

On Sat, Mar 21, 2020 at 4:42 PM Carl Nobile <carl.nobile at gmail.com> wrote:

> 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
>> _______________________________________________
>> Triangle, NC Embedded Computing mailing list
>>
>> To post message: TriEmbed at triembed.org
>> List info:
>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>> TriEmbed web site: http://TriEmbed.org
>> To unsubscribe, click link and send a blank message: mailto:
>> unsubscribe-TriEmbed at bitser.net?subject=unsubscribe
>>
>>
>
> --
>
> -------------------------------------------------------------------------------
> Carl J. Nobile (Software Engineer)
> carl.nobile at gmail.com
>
> -------------------------------------------------------------------------------
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20200322/10a4d627/attachment.htm>