Hi Charlie! Jenny, Emily and I are well and happy.
Your circuit made me chuckle, 'cause when I was thinking of your earlier
posting I was going to share the scheme I intended to use for charging a
capacitor with a string of microbial fuel cells by switching then
between parallel and series connections. But that was at silly low
currents were analog multiplexer chips would work. But the prototype was
using relays. If you're interested I could dig up the schematic.
Definitely the Rube Goldberg approach with relays, though, but your "one
battery at a time" requirement would make it simpler. :-)
Your schematic implies wanting to just charge one battery at a time, but
I can't see your circuit working past an initial point. But I think it's
in the right direction. (Nit: your schematic symbols are for some kind
of very generic FET transistor and I'm sure you'd be using high current
ones with body diodes, right? Bigger nit: if there were part numbers we
could more easily reason about the wiring).
So numbering the transistors from left to right as Q1-5, then with Q2
and Q3 off but the others on, that's "normal mode", right? With Q1-3 off
but Q4 and 5 on a lower voltage could charge the third battery. But I
don't see how you go beyond there with this circuit.
Or am I misunderstanding this? At a minimum you'd have to arrange for
your single-battery charging voltage to reach the positive sides of the
first two batteries, right? So maybe have Q6 and Q7 between the right
side supply and the "positive side" of Q1 and Q3, using the Q3 and Q5 to
disconnect paths as needed and then perhaps a Q8 and Q9 to select
between running the system to conduct the higher "all in series" battery
voltage to the load and the lower, charger voltage to the one of three
batteries. That is, a SPDT switch above the rightmost net going upwards
in your schematic.
Alternatively, figure out how laptop batteries are handled. They seem to
be always one big series connection, but maybe the extra connection pins
we see are for this same approach? I have no clue about that.
-Pete
On 3/22/20 1:09 PM, Charles West via TriEmbed wrote:
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 <[email protected]
<mailto:[email protected]>> 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
<[email protected] <mailto:[email protected]>> 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: [email protected]
<mailto:[email protected]>
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:[email protected]
<mailto:[email protected]>?subject=unsubscribe
--
-------------------------------------------------------------------------------
Carl J. Nobile (Software Engineer)
[email protected] <mailto:[email protected]>
-------------------------------------------------------------------------------
_______________________________________________
Triangle, NC Embedded Computing mailing list
To post message: [email protected]
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:[email protected]?subject=unsubscribe
_______________________________________________
Triangle, NC Embedded Computing mailing list
To post message: [email protected]
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:[email protected]?subject=unsubscribe
