Nominally 240. But it really can be anything and I can convert it to
what I need.
Peri
------ Original Message ------
From: "Alan Arrison via EV" <ev@lists.evdl.org>
To: ev@lists.evdl.org
Cc: "Alan Arrison" <bigg...@comcast.net>
Sent: 13-Apr-20 9:48:53 PM
Subject: Re: [EVDL] custom battery
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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