Search found 388 matches

by francisco.shi
Tue, 07 Apr 2020, 18:53
Forum: Members Machines
Topic: 4Springs' Brumby
Replies: 316
Views: 54780

Re: 4Springs' Brumby

I had a thought that perhaps the problem is that the aluminium from the pouch is touching something. Then it will conduct some current which will damage the pouch. So I had a check of the cells in the pack from a year ago and had a look and the way the aluminium plates from the cooling system hold t...
by francisco.shi
Tue, 07 Apr 2020, 10:44
Forum: Members Machines
Topic: 4Springs' Brumby
Replies: 316
Views: 54780

Re: 4Springs' Brumby

Can you tell me how many cells are leaking?
by francisco.shi
Tue, 07 Apr 2020, 06:39
Forum: Members Machines
Topic: 4Springs' Brumby
Replies: 316
Views: 54780

Re: 4Springs' Brumby

It is a 60 cell pack.
I have sent the pictures to the cell supplier and I am waiting for a reply. They are on holidays until tomorrow. I will keep you updated.
by francisco.shi
Mon, 06 Apr 2020, 19:54
Forum: Members Machines
Topic: 4Springs' Brumby
Replies: 316
Views: 54780

Re: 4Springs' Brumby

I run the cells for at least 10 cycles at 1C from 4.2v to 3.0v and at least 4 cycles at 2C. This was when I was checking the capacity. After that I have used for energy storage for a battery tester but at very low C rates. The battery tester cycles NiMH prius cells. It is mainly used for recovering ...
by francisco.shi
Sun, 05 Apr 2020, 19:50
Forum: Members Machines
Topic: 4Springs' Brumby
Replies: 316
Views: 54780

Re: 4Springs' Brumby

I have had a pack of these cells assembled for over a year and didn't have any leak and they still seem to be working fine. I can not explain why you are having such a high failure rate. Is there any chance you could have pulled the tabs while tightening the bolts and damaged the inside?
by francisco.shi
Sat, 04 Apr 2020, 13:23
Forum: Members Machines
Topic: Brendon_m Moke
Replies: 188
Views: 23992

Re: Brendon_m Moke

You can add another 20kg worth of batteries.
by francisco.shi
Sat, 28 Mar 2020, 11:31
Forum: Members Machines
Topic: 4Springs' Brumby
Replies: 316
Views: 54780

Re: 4Springs' Brumby

I did exactly the same as you but I use the board as a heatsink for the power transistor. So I will have to relocate the sensor. 15853659623345810300733166448637.jpg I even called the sensor TH1 :lol: 15853660539928946359089787843007.jpg My plan is to run the balancing all the time. If the cells tra...
by francisco.shi
Fri, 27 Mar 2020, 04:51
Forum: Members Machines
Topic: 4Springs' Brumby
Replies: 316
Views: 54780

Re: 4Springs' Brumby

This is what i did on my board but i found that when the bypass is running it warms up the board and that causes the sensor to detect a higher temperature. I placed the sensor very close to the contact and far away from. The hot parts of the bypass circuitry but it still detects a few degrees higher...
by francisco.shi
Fri, 27 Mar 2020, 04:43
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 176
Views: 23142

Re: Francisco's Electric Pajero

That is correct. The batteries were not fully charged. The way the BMS is setup it will keep the cells balanced at any voltage no matter if the pack is charging or discharging. Because the bypass energy is recovered I can balance at any time without losing range if anything I will gain range because...
by francisco.shi
Wed, 25 Mar 2020, 19:11
Forum: Members Machines
Topic: 4Springs' Brumby
Replies: 316
Views: 54780

Re: 4Springs' Brumby

How did you attached the temperature sensors?
When I did some testing for the first time I found that if the contact overheats the tab conducts the heat to the cell quite efficiently.
by francisco.shi
Wed, 25 Mar 2020, 12:23
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 176
Views: 23142

Re: Francisco's Electric Pajero

4.2v is supposed to be full. The bypass circuit dumps the energy at the pack's terminal. So I can balance at any time. The way the balancing works is the master works out the average voltage of all the cells and it sets the target voltage to that value. Then if the difference between the max cell vo...
by francisco.shi
Tue, 24 Mar 2020, 20:01
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 443
Views: 71206

Re: Low cost BMS

My calibration compensates for scale and offset. I take a measurement at one known voltage then at a different known voltage and from that I work out a scale and offset. I have also made a setup to do it automatically. It is too much trouble to do it by hand. In my case the master calculates the cor...
by francisco.shi
Tue, 24 Mar 2020, 19:58
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 443
Views: 71206

Re: Low cost BMS

Do the nodes turn off or go into some low power mode to avoid discharging the battery when not being used? At 40% that means you generally bypass at about 0.24A? After doing the balancing yesterday I am starting to think that maybe 5A is an overkill. I have also dropped the max current to about 3A. ...
by francisco.shi
Tue, 24 Mar 2020, 05:16
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 443
Views: 71206

Re: Low cost BMS

How much is your bypass current?
by francisco.shi
Tue, 24 Mar 2020, 05:15
Forum: Batteries, charging, management and monitoring
Topic: Low cost BMS
Replies: 443
Views: 71206

Re: Low cost BMS

I was working on my BMS yesterday and was working thru the same problems as you, just dealt with them in a different way. https://forums.aeva.asn.au/viewtopic.php?p=78179#p78179 I do a two point calibration and the master is the one that does all the calculations. In my BMS the nodes have very simpl...
by francisco.shi
Mon, 23 Mar 2020, 21:46
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 176
Views: 23142

Re: Francisco's Electric Pajero

I have been working on the BMS today. I got 4 modules I have been using for testing to make sure there are no mistakes in the boards. I was assembling and calibrating the modules in sets of 5. Here are some pictures of the boards in a subpanel. 15849701403783566395928291262880.jpg 158497010783070813...
by francisco.shi
Thu, 12 Mar 2020, 17:47
Forum: Batteries, charging, management and monitoring
Topic: E63 LG 63Ah NCM battery group buy
Replies: 35
Views: 5442

Re: E63 LG 63Ah NCM battery group buy

I am going to get more cells in case anyone wants to get some.
If anyone is interested please let me know.
by francisco.shi
Thu, 05 Mar 2020, 09:01
Forum: Members Machines
Topic: Brendon_m Moke
Replies: 188
Views: 23992

Re: Brendon_m Moke

The pajero is 2400kg, has 4 really wide high profile tyres, two right angle diffs and a limited slip diff on the back. The back is also very square.
So I am starting to be (very) concerned. I am just hoping that the 60kph consumption will not be too high.
by francisco.shi
Sun, 01 Mar 2020, 11:21
Forum: Members Machines
Topic: Brendon_m Moke
Replies: 188
Views: 23992

Re: Brendon_m Moke

I am starting to worry about how much power the Pajero will need at 100kph.
by francisco.shi
Sun, 01 Mar 2020, 10:54
Forum: Electric motors and controllers
Topic: questions regarding rewinding and stator insulation
Replies: 16
Views: 1459

Re: questions regarding rewinding and stator insulation

Roughly speaking if you halve the number of turns you will get the same rpm at half the voltage. What you should aim is to put as much wire in the slots as you can possibly fit. The reason for the cardboard/plastic inserts is for ease of manufacture and to reduce cost. The paper/plastic will stop th...
by francisco.shi
Thu, 27 Feb 2020, 06:01
Forum: General EV Discussion
Topic: Tesla using LFP in China
Replies: 16
Views: 1283

Re: Tesla using LFP in China

Pouch cells are much easier to cool and pack. My battery pack complete with case is 380 kg for a 70kwh pack. That is 184wh/kg for the complete battery including the case. It has about 10 times the cooling efficiency and 1/3 of the internal resistance (including busbars and interconnects) of the Tesl...
by francisco.shi
Wed, 26 Feb 2020, 05:10
Forum: General EV Discussion
Topic: Tesla using LFP in China
Replies: 16
Views: 1283

Re: Tesla using LFP in China

It also seems they are going to use pouch cells instead of cylindrical.
The reason appears to be better backing density.
If they think the total pack energy density will be similar then the cylindrical cells must be doing very poorly compared to pouch for packing effecienty.
by francisco.shi
Sun, 16 Feb 2020, 04:59
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 176
Views: 23142

Re: Francisco's Electric Pajero

About the quietness the inverter is running at 7khz and surprisingly there is no 7khz noise coming from the motor. I was very surprised. However when I lift the wheels and run it there is a lot more noise from the diff gears than I was expecting. I have to wait and see how noisy it is once it is dri...
by francisco.shi
Sat, 15 Feb 2020, 16:32
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 604
Views: 63341

Re: Prelude conversion project - some questions

Any chance the charger or DC-DC converter for 12v may be causing the problem?
by francisco.shi
Wed, 12 Feb 2020, 04:01
Forum: General EV Discussion
Topic: Aussie electric vehicle sales triple in 2019
Replies: 15
Views: 1382

Re: Aussie electric vehicle sales triple in 2019

My guess is that an electric drive train excluding the battery is considerably cheaper than an ICE drive train (engine + transmission + exhaust etc) so it seems the price we are paying is the price of the original ICE car + the price of all the electrics. No discount for not having the ICE.