DIY Electric Car Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
108 Posts
Discussion Starter #1
So I'm beginning to get my traction batteries balanced and ready to wire but I have a question. My batteries are these:

http://www.techdirectclub.com/lot-of-9-samsung-module-5s-car-golf-cart-bosch-battery-5-cell-18-5vdc-1-1kwh-10c/

And I have 18 of them that I will wire to make a 30S3P pack (120V 180AHr). The wire in the car now is 2/0 between the battery leads and controller (car is currently on lead acid pack of 96V).

A. Should I run the new batteries in a 5S3P first and then series those together? Or run a 30S and then parallel the strings only at the top?

B. If the jumper length is short, less than 4" long, I should be okay to run a 4 awg wire, yes? My battery studs are M6 and there isn't room to run 2/0. If I split the load evenly across the packs, there won't be more than say 200A peak through each string.

Thanks!
 

Attachments

·
Registered
Joined
·
733 Posts
So I'm beginning to get my traction batteries balanced and ready to wire but I have a question. My batteries are these:

http://www.techdirectclub.com/lot-of-9-samsung-module-5s-car-golf-cart-bosch-battery-5-cell-18-5vdc-1-1kwh-10c/

And I have 18 of them that I will wire to make a 30S3P pack (120V 180AHr). The wire in the car now is 2/0 between the battery leads and controller (car is currently on lead acid pack of 96V).

A. Should I run the new batteries in a 5S3P first and then series those together? Or run a 30S and then parallel the strings only at the top?

B. If the jumper length is short, less than 4" long, I should be okay to run a 4 awg wire, yes? My battery studs are M6 and there isn't room to run 2/0. If I split the load evenly across the packs, there won't be more than say 200A peak through each string.

Thanks!
4 awg is probably too small for your app. Set up a few cells with the peak load and check it out. You'll probably need to fab and set up buss bars. The more pressing task, as I see it if the voltages are as written on the box flaps, is to quickly parallel cells and slowly bring them up to near the max V. With the wide V spread, there may be some bad cells. If there's any way to run them through some charge/discharge cycles- even better. At least you'll find out before they're put in a pack.
 

·
Registered
Joined
·
108 Posts
Discussion Starter #3
Yes, those voltages on the boxes are how they were delivered. I now have two groups of 6 each at the same voltage (one group at 20.4V, the other at 19.4)and have been using a 24VDC switchmode power supply charging these up to the 20.4 volt level, which is the highest voltage that was delivered. I'll get these all at the same level and then do a discharge, measuring as I go. I really hope I don't have any bad cells but I have only checked pack voltage, not cell voltage.

And I just discovered today that these are Fiat 500e batteries.
http://www.diyelectriccar.com/forums/showthread.php/fiat-500e-battery-modules-170329.html
 

·
Registered
Joined
·
1,476 Posts
i'm trying to visualize the battery layout that would allow jumper wires of only 4" length, but can't really see it. But what would be the total length of jumpers within any given string subject to the peak 200A--2 ft, 3 ft?

4AWG has a resistance of about 250 microOhms per foot, so it would drop about 50 mV per foot and waste 10W as heat. So even with say 3 ft of jumpers you would only drop about .15 V in the wire, and loose 30W in heat, all this for the length of time you operate at the 200A peak. Unless you plan to race or drive with an awful heavy foot i don't think you will be seeing 200A often and the 4 AWG would be okay.

i used 4AWG jumpers that varied from 5 to 10 ft long in a big linear motor and put several thousand amps thru them for 10 seconds with no fusing of the wire, so it can handle quite a bit for a short time. my 2¢
 

·
Registered
Joined
·
108 Posts
Discussion Starter #5
Thanks. My controller is 600A and I'll have three banks of batteries, so 200A per bank peak. My batteries have their posts on opposite corners so for the most part, the leads will be very short. All the long leads will be bigger gauge.
 
1 - 5 of 5 Posts
Top