Battery Changeout - DIY Electric Car Forums
Go Back  

DIY Electric Car Forums > EV Conversions and Builds > Batteries and Charging

Register Blogs FAQ Members List Social Groups Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Display Modes
  #1  
Old 06-13-2017, 05:58 AM
Sylent Green Sylent Green is offline
Junior Member
 
Join Date: Dec 2013
Location: Orlando FL
Posts: 18
Sylent Green is on a distinguished road
Default Battery Changeout

Upon recent recharge of my battery pack, I discovered I had...issues.
I was running 18- 12V 20AH AGMs in a 6s3p 72V configuration.
The reason for this arrangement was for space considerations on my electric motorcycle.

While charging I noticed that one of my three modules was receiving almost no current, and when I started checking for an open somewhere, I found voltage levels (with and without the charger connected) that were mystifying.

Even after disconnecting the parallel connections, I was measuring voltage from one module to the other and to the chassis! No wiring problems were found.

Apparently one of my AGMs sprung a leak and this turned my whole system into a conductor.

Long story even longer, I now want to change to a different type of battery, and the consensus seems to be to use a modified Leaf or Volt battery.

This means I need to learn the acronyms you all toss about, and get a clearer picture of "C", "BMS", advantages and disadvantages of specific series/parallel configurations, and ways to manage the high voltage chargers (that I would like to have on-board)


The information that I have on this does not align with what I see on the forum, but the reality of my experience does.

http://www.diyelectriccar.com/forums/showthread.php/interesting-controller-behavior-184561.html.

I would like to end up with over 70V and more than 50AH, but I'm not married to anything, In fact I just changed my motor from a SepEx (shunt) to a series wound, and I am not ruling out AC.

In the end, I would like to be able to go 10 miles with a top speed of about 50mph and an average cruising speed of 35-45 mph. Stop and go.
Reply With Quote
Sponsored Links
Advertisement
 
  #2  
Old 06-13-2017, 06:29 AM
hmincr hmincr is offline
Senior Member
 
Join Date: Jan 2012
Posts: 193
hmincr is an unknown quantity at this point
Default Re: Battery Changeout

PM sent to your inbox.
Reply With Quote
  #3  
Old 06-19-2017, 08:13 AM
Sylent Green Sylent Green is offline
Junior Member
 
Join Date: Dec 2013
Location: Orlando FL
Posts: 18
Sylent Green is on a distinguished road
Default Re: Battery Changeout

I was wondering why I got no replies to my post , so I re-read it and realized that I did not actually ask any questions

I did look through the battery forum a bit ( did not read all of it, there is a lot) and do not see what I want.

Specifically:
What are the dimensions and available power from an individual leaf or volt module?

I have serious space concerns.

Is it reasonable to expect to be able to make or adapt a BMS (if I understand the term correctly) to whatever voltage level/ battery configuration I end up with? ( I do have a BS/EET degree, but recent experience has proven that to be inadequate in this realm)

The performance with my system proved inadequate at 72V 60AH (350A controller) with AGMs.

I have been told that any series/parallel configuration with a given number of batteries will behave the same, but this does not seem logical to me and I was wondering if experience proved or disproved this theory.

In other words, if I have 18 - 12V batteries connected to give 72V, there will be more than one mechanical configuration that achieves this.

Will they all have the same behavior?

Enough questions for now.

Kendrick
Reply With Quote
 
  #4  
Old 06-19-2017, 04:08 PM
BatteryGuy BatteryGuy is offline
Junior Member
 
Join Date: May 2017
Posts: 16
BatteryGuy is an unknown quantity at this point
Default Re: Battery Changeout

I can help you with new Volt and Focus batteries. Provide a ph# and I will call you.
Reply With Quote
  #5  
Old 06-19-2017, 09:39 PM
brian_ brian_ is offline
Senior Member
 
Join Date: Feb 2017
Posts: 264
brian_ is on a distinguished road
Default Re: Battery Changeout

Quote:
Originally Posted by Sylent Green View Post
What are the dimensions and available power from an individual leaf or volt module?
This page lists original Leaf battery specs: http://www.electricvehiclewiki.com/Battery_specs
It isn't authoritative, but it does provide sources.
Reply With Quote
  #6  
Old 06-19-2017, 09:56 PM
brian_ brian_ is offline
Senior Member
 
Join Date: Feb 2017
Posts: 264
brian_ is on a distinguished road
Default Re: Battery Changeout

Quote:
Originally Posted by Sylent Green View Post
I have been told that any series/parallel configuration with a given number of batteries will behave the same, but this does not seem logical to me and I was wondering if experience proved or disproved this theory.

In other words, if I have 18 - 12V batteries connected to give 72V, there will be more than one mechanical configuration that achieves this.

Will they all have the same behavior?
Yes, they will be the same... as long as no cell fails and all cells behave identically. The reasons for choosing specific configurations (for a given nominal battery system voltage and cell size/shape) are not about the performance of the system under ideal conditions, but are about:
  • packaging
  • the effect of individual cell failures
  • the effect of variations in cell performance
  • the complexity of the battery management system required
... and maybe some other factor that I haven't thought of.

In any valid configuration, each cell is not "aware" of where it sits in the system. Each one adds one cell worth of voltage to the current passing through it; each cell is passing the current that a single cell can deliver at that voltage. As a result, the overall effect doesn't depend on the specific configuration.


Also, I suggest thinking of combining "cells", not "batteries". A battery is, by definition, a group of cells; the 12-volt (nominal) lead-acid batteries are indeed batteries (with six cells each), but if you re-configure a pack from a production EV you may be dealing with individual cells. Smaller groupings of cells (such as the four-cell group of the Leaf) are usually called "modules", even though they are legitimately batteries; at least in this forum the term battery seems to be reserved for the complete set of cells.
Reply With Quote
  #7  
Old 06-20-2017, 05:26 AM
Sylent Green Sylent Green is offline
Junior Member
 
Join Date: Dec 2013
Location: Orlando FL
Posts: 18
Sylent Green is on a distinguished road
Default Re: Battery Changeout

Thanks Brian, this helps.
Reply With Quote
Reply

Share or Bookmark this

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

 
Support DIY Electric Car
Sponsors

All times are GMT -6. The time now is 08:22 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Ad Management by RedTyger