[Hackability] battery voltages in mobility scooters

[Zach]

Thanks Susan, this could be very useful!
  One of the hangups I'm finding with the BQ2013H is sourcing the 0.005 ohm 10W resistor.  I can only find suitable ones on Digikey for $3 each + ship... itll be something like $10 just for that part.  
Also, the max battery capacity is measured at 15Ah, which means it will work for Liz's scooter but not my main one.  Liz, would you want the circuit after I'm done building it?  It makes the most sense for you to use it :)
Other than that, it's very very badass.

I also did another scooter hack last night at NB, and a very useful one I think.  My forward/reverse pot comes loose over time with its shitty set screw, resulting in me moving slowly backwards when I put the key in.  The only way to fix it is to disassemble the whole thing and reset the screw...which is a serious pain in the arse to do every so often.  The fix?  Wire in a parallel externally adjustable 50k trimmer pot.  It was Jake's idea, and it works great :)

Also got a schem for using the LM3914 with a 24v lead acid battery I can upload here if people want a simple 10-LED volt gauge for the chairs.  Its pretty nice.

Zach




----- Original Message -----
From: Susan Werner <heinousbutch at gmail.com>
To: Zach <organic_unity at yahoo.com>
Cc: hackability at lists.noisebridge.net
Sent: Wednesday, August 29, 2012 1:56 PM
Subject: Re: [Hackability] battery voltages in mobility scooters

Oooh, thanks. That's useful information. Can you give me contact information 
for John? I'd just like to ask before I commit to a certain design.

This might be of interest -- it's a fully analog (so no microcontroller needed!)
power and current monitor that's very easy to use: 
http://www.linear.com/product/LT2940

-- 
Susan

On Aug 29 13:41, Zach wrote:
> Hey Susan,
>   I've never seen a scooter with over 24v....it would be very rare to find.  John is a good person to ask (with the scooter shop).
> 
> Great news:  Got the Bq2013H chips in the mail and after some intense datasheet work I have finally calculated all the set values and parts for our application.  See attached schematic.  I'll update my webpage soon with more details.
> 
> I'm going to build the circuit and test within the week and if it works we can get on designing a PCB board for it!  One downside I've realized is that it works with a max battery capacity of 15Ah (according to the site anyway), which means it will work for most scooters but might not be the best for the especially big ones.  But we'll see.
> 
> --- On Wed, 8/29/12, Susan Werner <heinousbutch at gmail.com> wrote:
> 
> > From: Susan Werner <heinousbutch at gmail.com>
> > Subject: [Hackability] battery voltages in mobility scooters
> > To: hackability at lists.noisebridge.net
> > Date: Wednesday, August 29, 2012, 4:05 AM
> > I'm working on a DC-DC converter /
> > battery charger circuit with Liz to act as a
> > regenerative brake for mobility scooters, and it's an
> > explicit goal for the 
> > design to be easily adaptable on different models. I've a
> > question -- what is 
> > the highest battery voltage commonly used? I need this
> > information in order to 
> > properly select the DC-DC converter controller and the power
> > transistors for 
> > the DC-DC converter. I know 24 volts is a voltage that's
> > used (two 12V 
> > batteries in series), but are there any mobility scooters
> > that use higher 
> > battery voltages? Are there any that use voltages that are
> > higher than say,
> > 36 volts? The end goal is to have a model-agnostic
> > regenerative brake 
> > controller that needs minimum customization (beyond, of
> > course, desired 
> > voltage output) for each individual installation.
> > 
> > Also, if you'd like to get involved, let me or Liz know! 
> > 
> > -- 
> > Susan
> >