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Old 02-19-2018, 09:18 AM   #11
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Hi, Thanks,in your first post the last two pictures did not want to open for me. In your response to me that picture did open.

Ok with 8 modules in parallel are you going to interconnect the individual cells also. It would simplify your bms system a lot. This is easy to do with a Nissan leaf pack. ( have one of those also in my other DIY electric car) but more tricky with the volt hardware.


We use the 2013 generation volt battery. so ours are 48 volt and 24 volt modules Also the bms modules are on top of each battery module.

Looking forward on how you are going to reconnect the battery tabs after you have separated them.

on the volt bms some people working on it on the ev sites. We are not that far yet in our reverse engineering. We have modified the hardware of one bms module with leds. so we can visually see if a cell is balancing but did not do a test yet.

later j
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Old 02-19-2018, 09:54 AM   #12
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Quote:
Originally Posted by joeblack5 View Post
Hi, Thanks,in your first post the last two pictures did not want to open for me. In your response to me that picture did open.

Ok with 8 modules in parallel are you going to interconnect the individual cells also. It would simplify your bms system a lot. This is easy to do with a Nissan leaf pack. ( have one of those also in my other DIY electric car) but more tricky with the volt hardware.

We use the 2013 generation volt battery. so ours are 48 volt and 24 volt modules Also the bms modules are on top of each battery module.

Looking forward on how you are going to reconnect the battery tabs after you have separated them.

on the volt bms some people working on it on the ev sites. We are not that far yet in our reverse engineering. We have modified the hardware of one bms module with leds. so we can visually see if a cell is balancing but did not do a test yet.
Thank you for the feedback. So your work with the earlier Volt battery pack may still help.

Not completely sure I understand your comment:

"Ok with 8 modules in parallel are you going to interconnect the individual cells also. It would simplify your bms system a lot. "

I do plan to have eight 48V batt modules in parallel, each with 12 cells. And I do intend to monitor each of those cells. Is that what you are getting at?

As for reconnecting the batt tabs, I won't be touching any of the welds. My initial concept for the three each 16 cell modules is to cut a single busbar on each isolating 4 cells, then hard wiring those three orphan sets of 4 cells... Simple right (he said sarcastically)?
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Old 02-19-2018, 10:51 AM   #13
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Yes , monitoring all the cells individually is what i was curious about. The gent in the youtube video you mentioned that uses the nissan leaf cells does it different. He connects the cells with the busbars so that they become one. Then he only has to monitor the cells that are in series..

Yes, that "simple right" is the key sentence. cutting them Ok but re connecting to these tabs for high current without exceeding the current densities of the tabs will be exciting. The tabs are welded over a large surface area as to spread out the current over the whole area . It will be cool to see how your solution will develop.

What do you think is under the little black dots on the printed circuit board? micro fuses?

Later j
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Old 02-21-2018, 12:52 PM   #14
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Originally Posted by joeblack5 View Post
Yes , monitoring all the cells individually is what i was curious about. The gent in the youtube video you mentioned that uses the nissan leaf cells does it different. He connects the cells with the busbars so that they become one. Then he only has to monitor the cells that are in series..

Yes, that "simple right" is the key sentence. cutting them Ok but re connecting to these tabs for high current without exceeding the current densities of the tabs will be exciting. The tabs are welded over a large surface area as to spread out the current over the whole area . It will be cool to see how your solution will develop.

What do you think is under the little black dots on the printed circuit board? micro fuses?
The youtube gent with the Leaf batteries is Juan and the "Beginning From This Morning" coach conversion. I noticed he didn't seem to have as many BMS leads as I seemed he should (or could...)

I am not yet sure what the "little black dots" on the white boards are for. However I do intend to use those boards, and the plugs on the boards. I plan to use the orange connectors from the Volt harness to make BMSinterconnect pigtails.

It sure would be nice to find a wiring diagram for the gen2 Volt BMS. I "think" I understand the pin outs on those connectors but I'd like to be certain before I start poking around those terminals.


I am currently exploring designs for the "tab" connections. Again my goal is to keep it simple but effective. Although, as I read these posts, none of this sounds very simple...
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Old 02-21-2018, 01:01 PM   #15
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LEAF batteries were air cooled and had big issues when they got hot with degradation.. Volt batteries were liquid cooled and many with 1st gen volts have nearly 0 degradation even after 7 years of owning the cars...

keep them climate controlled!!! heat will ruin them... the volt would activate it's A/C compressor and cool the liquid coolant circulating in the pack if they got too hot.. it happened more than once when charging my volt in the summer daytime.. so i took to charging it in morning before i drove it rather than after i parked it..

chevy only discharged it to 15-20% and to a max of 80-85% to keep its longevity.. and it works... LEAF allowed more charge capacity for better range at the sacrifice of Longevity.. I wouldve took the charge controller and inverter too.. its a nice 1500-2000 watt continuous inverter running off the DC batteries to give you a nice 12 volt source... Volt's charge congtroller works very well .. then again charging from solar you may have no use for it..
-Christopher
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Old 02-21-2018, 03:12 PM   #16
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LEAF batteries were air cooled and had big issues when they got hot with degradation.. Volt batteries were liquid cooled and many with 1st gen volts have nearly 0 degradation even after 7 years of owning the cars...

keep them climate controlled!!! heat will ruin them... the volt would activate it's A/C compressor and cool the liquid coolant circulating in the pack if they got too hot.. it happened more than once when charging my volt in the summer daytime.. so i took to charging it in morning before i drove it rather than after i parked it..

chevy only discharged it to 15-20% and to a max of 80-85% to keep its longevity.. and it works... LEAF allowed more charge capacity for better range at the sacrifice of Longevity.. I wouldve took the charge controller and inverter too.. its a nice 1500-2000 watt continuous inverter running off the DC batteries to give you a nice 12 volt source... Volt's charge congtroller works very well .. then again charging from solar you may have no use for it..
-Christopher
CK, good gauge on the Leaf/Volt batteris and heat. I intend to keep the batteries in a vented enclosure in the living space of the bus. I have read that the batteries will live happily there?

The salvage yard had two 2017 Volts. I wonder if they still have the parts you mention. However, as both they were IIHS crash test cars, those parts may be trashed...
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Old 02-21-2018, 04:48 PM   #17
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some of that stuff was in the back but yeah the left front houses a good bit of the charging infrastructure.. the car was specifically designed to not puncture the battery pack so your pack will be fine. as for the battery temperature... rate of charge and discharge determines most the temperature of the batteries.. I was charging mine at a rate of 3.3 Kw. (the Gen 1 volts didnt have 6.6 kw chargong even though L2 supported it. ).. my car A/C would come on with the car in the garage to cool the batteries.. since that pack was enclosed and wasnt designed to cool itself with air, there was more a need for the liquid cooling .. my guess is how packed in there the cells are plays a part in it, since you are modding the packs you may be able to provide some air cooling.. or keep the packs together and use a simple coolant / air heat exchanger.. before the car would engage the A/C compressor for battery cooling.. it would turn on the piump and the front fan (there was a battery coolant radiator on the front).. {ironically one of the first things to be destroyed in even the most minor crash}...

my car sprung a small leak in the battery cooling loop and it put me along side of the road waiting on a hook.. the car wouldmt even function in gas engine mode.. after about 20 minutes of waiting on the tow listening to the radio, the car complained its 12 volt battery was low and shut everything off. so it had completely disengaged the 360 volt altogether.. GM takes battery cooling crazy serious.. my guess is they didnt want to replace any packs under warranty. or deal with complaints from the likes of early electric cars with battery degradation so they went all serious on BMS and Thermal Management.. the SOC was a big one. .. my pack in my 2013 was 16 Kwh, they used 10Kwh of it.. I think they increased it to like 10.5 in 2014 to boost the all battery miles to make a benchmark of some type.. I dont know much about your Gen volt but from what I have heard they are just as anal about the battery on it..

the intrigue of an electric car had left me when it came time to trade my 2013.. {when I got it free chargers were everywhere and almost no one using them... so I didnt pay hardly at all. unless I happened to charge at home.. now most of that is gone... chargers are crowded and are expensive..}..

-Christopher
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Old 02-21-2018, 06:38 PM   #18
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I only charged mine at home, there did not seem to be many chargers in Cincinnati when I had the leaf, still do not seem to be many for my E-golf, the one I found so far had a ridiculous price per hour
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Old 02-22-2018, 11:36 PM   #19
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2017 Chevy Volt Battery Pack

When you connect cells in parallel, then put those into a single series string you only need to monitor / balance each set of parallel cells in the string once. The cells connected in parallel by definition have to all be at the same voltage.

Juan is using 7 sets of 7 modules in parallel. Each Leaf module contains 2s2p cells, with a center tap available for monitoring / balancing. So he only needs 15 lines to the BMS for the 14 ďcellsĒ in series. Iím doing 8 sets of 6 in parallel (60v nominal) so Iíll need 17 lines to the BMS for the 16 cells. If I had configured the other way, with 6 separate strings of 8 modules in series I would have to have something like 86 wires to the BMS to monitor balance all 96 cells independently, 14 x 6 internal taps plus the parallel top and bottom connections. If there is even such a thing as a single BMS that can handle 96 cells in multiple strings. More likely Iíd need separate 16s bms for each string. Most BMSes require every cell tap to be higher in voltage than the one below it. Putting the lower voltage higher up the chain to start the next string will at best confuse it, and usually blow something up by putting -48v across a device thatís meant for something like 0-5v of a single cell.

Hope that all makes sense.

Still in testing on the bench, but hereís the setup going into my Skoolie.



And a look at the bus bar arrangement and temporary BMS taps. When my Batrium comes in the monitor boards will mount directly to each block of parallel modules.



Rob




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Old 02-22-2018, 11:44 PM   #20
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