That sounds like almost super-capacitor territory. What voltage is needed?
Designing and implementing a BMS is something even EE's have trouble with.
However, if the voltage is low enough, it makes it much easier.
Al
On 4/14/2020 12:33 AM, Peri Hartman via EV wrote:
Hi,
I need a battery with about 150Wh and a discharge rate of 8kW for up
to a minute or so. I've spent a few hours searching and there doesn't
seem to be anything on the market that fits this. There are, of
course, higher capacity batteries that can deliver 8kW, but that's not
what I'm after.
This isn't for an EV, so I suppose this is somewhat off topic,
although BMSs are a relevant topic to EVs. It's for a home appliance
that I'm prototyping.
I'm pretty sure I can find affordable cells that I can put together to
do this, but then I'm stuck with a custom BMS. I suspect that's the
route I'm going to have to take. So, let's talk about that.
Each cell (or group of parallel cells) needs a monitoring circuit (is
there a name for this?). And theses monitors need to communicate with
a BMS. I'm less concerned about designing the BMS as I think I can use
an arduino and do it in software. The arduino can control the charger,
too. I can revisit this later. But for the monitors, I need to get it
right. Since the battery will be in the house, it cannot cause a fire.
Ever. Of course, I will have over temperature sensors which shut off
the charger and shut off the load.
Here's what I think each monitor's role is, based on what I've read on
EVDL over the years and some common sense :)
- cell over voltage
- cell under voltage
- cell over current
- cell temperature
In all of the above the circuit should shunt the cell.
In addition, the monitor should constantly report the cell voltage,
current, and temp to the BMS.
If there's something reliable I can buy, at a reasonable price, that's
my first choice. Otherwise, I guess it's getting someone to help
design and fabricate these.
I would be grateful for your suggestions.
Peri
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