Author Topic: Is there a fix for the wimpy GM battery Battery Management System?  (Read 6664 times)

Offline OCD

  • Confirmed
  • Magic Undergrad
  • ***
  • Posts: 62
Hi All:

After running the 48 volt 10 amp/hr GM battery pack through it's paces, I'm a bit disappointed to find that the BMS kicks out with the power of the 1000 watt MPIII. I was actually hoping to use these packs with controllers larger than 1000 watts. I have a V-power 20 amp pack that costs about $100 more than the 48v 10a GM one, but it obviously has a higher rated BMS as it doesn't cut out under the load of my 3000 watt controller. Has anyone found a 35-50amp BMS that would fit inside the GM case to replace the wimpy 25amp one? I can't see this battery being reliable at power levels over 500 watts. I'm not happy that I spent $1200 on two batteries that will not reliably supply the motors as sold by GM without running two in parallel which would effectively give me 20amp/hr with 50amp BMS (combined). There is no indication anywhere on any GM site that these batteries are not up to the task. I mean really, I'm sure it wouldn't kill the cells if there was a 35amp BMS in these from the factory.  :o

(the other) Alan

Offline Morgen 3Eman

  • Confirmed
  • PhD. Magic
  • ******
  • Posts: 620
Re: Is there a fix for the wimpy GM battery Battery Management System?
« Reply #1 on: November 11, 2014, 11:35:12 PM »
Hi, the other Alan

I'm kind of surprised at your experience, because when I had an analog ammeter on my trike I would routinely peg it hard and long at something over 60 Amps….(Lyen/MP3)

TTFN,
Dennis

Offline Bikemad

  • Global Moderator
  • Professor
  • PhD. Magic
  • ******
  • Posts: 5,337
Re: Is there a fix for the wimpy GM battery Battery Management System?
« Reply #2 on: November 12, 2014, 12:20:03 PM »
I discovered the same current limitation on my GM 48V10Ah LiFePo4 battery:

The 10Ah LiFePO4 cells are rated for 30 Amps continuous and 50 Amps peak current, but I seem to recall that the BMS is limited to 30 Amps. 


I have carried out a quick check using my modified MPII, and my new 48V 10Ah GM battery only delivers 31.21 Amps maximum @ 46V (1,433 Watts) yet my knackered 4.5 year old 14S 5Ah LiPo pack (without a BMS) is able to deliver 38.53 Amps maximum @ 42V (1,618 Watts). So I guess the BMS on the GM battery is holding back the current.


My MP4 usually draws a maximum of 30 Amps when using my LiPo pack with no BMS to restrict it.

If the GM battery can supply more than 30 Amps, it should not cut out unless the voltage of one of the cells falls below the lower voltage limit.

You could swap the existing BMS for a high current BMS like this:

BMS-LFP-PCM-SMT-System-16S-16x-3-2V-eBike-Battery-16x-3V/221172143478][/url][/acronym]

But if you are pulling more than 30 Amps continuous from the pack, I suspect the cells would start to suffer.

Alan
 

Offline Morgen 3Eman

  • Confirmed
  • PhD. Magic
  • ******
  • Posts: 620
Re: Is there a fix for the wimpy GM battery Battery Management System?
« Reply #3 on: November 13, 2014, 01:46:15 AM »
So is my BMS faulty?

Dennis

Offline OCD

  • Confirmed
  • Magic Undergrad
  • ***
  • Posts: 62
Re: Is there a fix for the wimpy GM battery Battery Management System?
« Reply #4 on: November 13, 2014, 02:50:42 PM »
 I know it's not just me, there is another GM 48 volt 10amp user not far from me complaining about the same thing. It's not hard to open the battery case and change a BMS (although a decent one likely won't fit the space inside) but that will of course void the warranty. The cells are rated at 50 amp max so you'd think a 30 amp BMS would have been fine to put in the first place. I don't have a cycle analyst to measure the actual current draw and realize this likely wouldn't happen with the MPIII if I were pedalling at the time, it mainly shows when I'm riding my drift trike or trying to use on a bike with a 1500 watt controller. I realize running two batteries in parallel would solve the problem but that adds more weight/cost than I wanted. Nice to know I'm not the only one experiencing this problem. I know I have a lead thumb...

(the other) Alan

Offline Hastings

  • Confirmed
  • Magic Undergrad
  • ***
  • Posts: 61
Re: Is there a fix for the wimpy GM battery Battery Management System?
« Reply #5 on: November 16, 2014, 09:11:47 AM »
Try Ping batteries new BMS, it is quite unwimpy...

They have picture on their home page http://www.pingbattery.com/

here is the specs you neeed:

http://www.pingbattery.com/blog/whats-new-on-v5-lifepo4-bms-battery-management-system/


Offline OCD

  • Confirmed
  • Magic Undergrad
  • ***
  • Posts: 62
Re: Is there a fix for the wimpy GM battery Battery Management System?
« Reply #6 on: June 15, 2015, 06:51:47 PM »
The cure is to connect two in parallel if you want to run a 3000 watt 80 amp controller.


Offline e-lmer

  • Technical Officer
  • Master of Magic
  • ******
  • Posts: 450
    • My page
Re: Is there a fix for the wimpy GM battery Battery Management System?
« Reply #7 on: June 19, 2015, 07:18:01 PM »

Just to make sure I understand, are talking about pulling
(48V * 50A = ) 2400 Watts through a 1000 Watt motor?

That can't end well.

Offline OCD

  • Confirmed
  • Magic Undergrad
  • ***
  • Posts: 62
Re: Is there a fix for the wimpy GM battery Battery Management System?
« Reply #8 on: June 28, 2015, 06:03:48 PM »
Actually the controller is rated for 80 amps which would tip things well over the 3000 watt (peak) mark. If you can run the motor hard and still put your hand on it, it'll hold up. I've been running a 3000 watt 80 amp Greentime controllers with Pro 901 motors for a couple of years with no problems, if things get too hot you could always drill some cooling holes in the side plates but I haven't needed that yet.

(the other) Alan  8)