Re: Battery Balancer
- Nice work Wolf.
I noticed on your site that you went to BB 5.0 with your bot. My team
and I were at 5.0 as well with 64 Wedge (now Max Wedge). Small world!!
We've moved into self balancing scooters and EV's these days.
Almost all of the OSMC motor controls for the bots were based on Atmel
processors. While I cannot write code to safe my life, I have burned a
million of them in the course of motor control repairs that I use to do.
Anyway, it's exciting to see a potential BMS for our vehicles coming
Watch out for EMI. I highly recommend using shielded inductors.
--- In firstname.lastname@example.org, "Wolf" <wolf@...> wrote:
> I worked on the battery balancer some more:
> Its now moved from the simulation realm to the bread board realm:
> Its a simple, single inductor, discontinuous, switch mode, buck boost
> convertor running at 250Khz.
> Currenly I am using one of my 16 channel servo controller boards to
> measure the voltage of each battery and generate the PWM signals to
> the MOSFETs.
> Using the ATmega on board 10-bit ADC convertor only gives about a 15mV
> resolution... which is plenty for testing. :)
> Atmel has a new Xmega micro that has a 12-bit ADC... that would be
> 4mV resolution... which might be overkill.
> Which does bring up a good question: how balanced is balanced?
> Here we have the right battery at 12.10V and the left battery at 12.08V
> and the balencer is pumping 130mA from right to left.
> There is a 20mV difference in voltage, but the system has a
> only 15mV... so it falls in and out of being equal, which results in the
> 130mA current. If the balancer where to turn off now, the voltage on the
> right battery would rise slightly due to the balancer load being
> and the voltage on the left battery would fall slightly due to the
> balancing current being removed.
> The balancer will continue in this state untill both voltages are equal
> and there is no longer any current flow.
> Now, to give it a work out, I added a battery charger to the battey
> Now the right battery is at 12.34V and the left is at 12.10V so
there is a
> balancing current of 680mA.
> I was shooting for a 1 Amp max balance current, but the max is around
> 700mA when I start to saturate my inductor and start running into
> continuous mode. This means I need a bigger (more current) inductor. ;)
> I figure that 1 Amp is pleanty since, if you had unbalanced batteries...
> 24 amp-hours could be transfered each day. And if your batteries are
> out of balance each day, then you need to replace them. ;)
> Anyway, more pics are here:
> Next step is to get in some more bigger inductors to play with and
> the linear regulator powering the micro with a small switching power
> supply to lower the quiescent current. Chose a final (cheeper) micro
> controller. Lay out a circuit board. Do more testing.
> Longer term stuff:
> Get the CAN bus up and running. Write a nice touch screen visual
> so I can see all the voltages of all my batteries and what they are
> Sure you can buy already excisting battery balancers out there...
> is more fun! :D
There are a number of chargers out there that use the high frequency
method. Without breaking the bank and getting some versatility Black
and Decker has some 3 stage, temp compensating models, that they call
"Smart Chargers". Fairly capable processor controlled and the better
ones let you select flooded, gel or agm.
I have a couple of them and they are consistent. The weakest point in
their design seems to be the little cooling fan and I have gotten one
replacement via the 5 year warranty as a result of the fan wearing out.
You can use them on your other vehicles and not just the EV so they
give you a bit more versatility if needed.
--- In email@example.com, "Jeff" <Catoauto@...> wrote:
> The batteries I purchased were Interstate deep cycle AGM's DCM 0090
group 27. I guess before I purchased them I should have done more
research. They did come with a 1 year warranty and they did not charge
me for the 2 batteries they replaced.
> The charger in my 97 Force is a BC3300 (NLG412B). I do not know how
to change any of the settings on it so it is in its original charge
> Where is a good place to get a charger that will charge the AGM's
properly one at a time and do an equalization charge?
> Jeff Nichols
> 1997 Force
> [Non-text portions of this message have been removed]