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Discussion Starter · #1 ·
I have 4 battery packs at 127 volts and each is ~50 amp-hours.
I am trying to achieve ~200 amp-hours at 127 volts and I have them wired as shown.
Please let me know if I need to clarify what I am asking.
THanks
Bob
My questions are,
1) Will the shunt work where it is, or do I need to move all the negative connections to go through the shunt and then to the controller?

2)Should the positive connections be to the battery and then to the contactor, or is the positive connection as it is ok.

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I have 4 battery packs at 127 volts and each is ~50 amp-hours.
I am trying to achieve ~200 amp-hours at 127 volts and I have them wired as shown.
To do that, you need all four packs in parallel, and that is what your diagram shows... so far, so good.

My questions are,
1) Will the shunt work where it is, or do I need to move all the negative connections to go through the shunt and then to the controller?

2)Should the positive connections be to the battery and then to the contactor, or is the positive connection as it is ok.
  1. The shunt won't work because only the current from the lower two packs goes through it.
  2. The contactor will work because the path of all current from all paths goes through it.
The emergency disconnect won't work properly because only the current from the lower two packs goes through it, as cricketo mentioned.

You didn't ask, but the packs outlined in orange don't make sense. They each appear to consist of three modules, presumably 42 V and 50 Ah each and intended to be connected in series, but the middle module in each pack is backwards in each pack, so neither one would work.
 

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I don't understand your diagram.

All four of your cell modules need to be connected in parallel. They're not. Draw that first to form a "pack" that has one outgoing +/- pair of connections.

The disconnect goes between the pack and everything else connected to the pack (of four parallel modules). There also needs to be a fuse in that leg unless there's a girl/man in the fire brigade you're trying to meet up with.

The contactor then needs to switch that fused, disconnectable, leg on and off to the controller and any other HV stuff. That includes a DC-DC battery charger for your 12V.

Shunt placement depends on what current you want to measure. Charging current? Controller current? Both?
 

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I don't understand your diagram.

All four of your cell modules need to be connected in parallel. They're not.
The diagram is a bit of a mess, but all of the positive pack terminals are connected together, and all of the negative pack terminals are connected together, so the packs are indeed in parallel.

Part of the confusion comes from building the battery up from four packs (or blocks, or whatever you want to call them), with two of the packs being comprised of three modules each and the others looking like a single module each.
 

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Discussion Starter · #6 ·
Thanks for all the feedback, and the packs are a combination of Chevy VOLT and Smart4two batteries that is why the odd configuration. I moved the shunt so that is done, I will work on setting up the emergency kill later this week.
Bob
 

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Thanks for all the feedback, and the packs are a combination of Chevy VOLT and Smart4two batteries that is why the odd configuration. I moved the shunt so that is done, I will work on setting up the emergency kill later this week.
Bob
If they are Volt 12S modules, they run 45 volts nominally; three in series would be a 36S and 135 Vnominal set.
There were four generations of Smart ForTwo ED, each one with a different battery... none 36S as far as I can tell. What year or generation are these? Do you have a link to the source?

Do you have an updated diagram, with the shunt changed and the Volt module connections fixed?
 

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Discussion Starter · #8 ·
If they are Volt 12S modules, they run 45 volts nominally; three in series would be a 36S and 135 Vnominal set.
There were four generations of Smart ForTwo ED, each one with a different battery... none 36S as far as I can tell. What year or generation are these? Do you have a link to the source?

Do you have an updated diagram, with the shunt changed and the Volt module connections fixed?
Here are the specs on the Smart battery pack, I am running two of the three and they each are 31S .
 

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The Volt module strings haven't been fixed yet...
  • this is three modules in series: [+ -][+ -][+ -]
  • this is what you have: [+ -][- +][+ -]

Here are the specs on the Smart battery pack, I am running two of the three and they each are 31S .
That's the ED3, from the W452 (2012-2016) generation of ForTwo. The modules are 31S (115 Vnominal), with similar chemistry and thus voltage per cell to the Chevrolet Volt pack, so there's no way you can reasonably run them in parallel with the 36S (135 Vnominal) Volt module strings.
 

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Discussion Starter · #10 ·
The Volt module strings haven't been fixed yet.


That's the ED3, from the W452 (2012-2016) generation of ForTwo. The modules are 31S (115 Vnominal), with similar chemistry and thus voltage per cell to the Chevrolet Volt pack, so there's no way you can reasonably run them in parallel with the 36S (135 Vnominal) Volt module strings.
Won't the VOLT cells only charge to the same limits as the Smart battery? If the chemistry is the same and the charger set for the lower voltage cells it should be fine. I have the pack charging to 127 volts based on the Elcon battery charger algorithm.

What is the issue or danger of running them in parallel, if I need to I will find either more Smart or VOLT batteries to make the setup safer?

Bob
 

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Won't the VOLT cells only charge to the same limits as the Smart battery? If the chemistry is the same and the charger set for the lower voltage cells it should be fine. I have the pack charging to 127 volts based on the Elcon battery charger algorithm.

What is the issue or danger of running them in parallel, if I need to I will find either more Smart or VOLT batteries to make the setup safer?

Bob

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Won't the VOLT cells only charge to the same limits as the Smart battery? If the chemistry is the same and the charger set for the lower voltage cells it should be fine. I have the pack charging to 127 volts based on the Elcon battery charger algorithm.

What is the issue or danger of running them in parallel, if I need to I will find either more Smart or VOLT batteries to make the setup safer?
At 127 volts, the 36 cells of the Volt modules will be at 3.52 volts per cell, which is well under the nominal voltage so substantially less than half charged. The overall voltage of each pack or string is identical, because they are all paralleled together. At that same 127 volts, the 31 cells of the Smart modules will be at 4.1 volts per cell, which is nearly fully charged. Operate them together, and before you have used half of the charge in the Smart modules the Volt modules will be completely discharged and in danger of being damaged if you try to go any further. At about half-charged the Smart modules will be at 3.7 V/cell or 115 V, which for the Volt modules will be 3.19 V/cell... and the energy.gov report for the 2013 Volt says the minimum is 3.0 V/cell.

This is why dissimilar cells or different numbers in series of similar cells are never run in parallel.

Yes, getting more of one type of module and abandoning the idea of connecting dissimilar modules in parallel is the logical solution. You could modify one Volt module per string (pack) to remove 5 cell groups so you have 31S in each, matching the Smart modules. You could also use separate contactors for a Volt pack and a Smart pack, and use or charge only one at a time, but I think that's a miserable kludge.
 

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Discussion Starter · #16 ·
At 127 volts, the 36 cells of the Volt modules will be at 3.52 volts per cell, which is well under the nominal voltage so substantially less than half charged. The overall voltage of each pack or string is identical, because they are all paralleled together. At that same 127 volts, the 31 cells of the Smart modules will be at 4.1 volts per cell, which is nearly fully charged. Operate them together, and before you have used half of the charge in the Smart modules the Volt modules will be completely discharged and in danger of being damaged if you try to go any further. At about half-charged the Smart modules will be at 3.7 V/cell or 115 V, which for the Volt modules will be 3.19 V/cell... and the energy.gov report for the 2013 Volt says the minimum is 3.0 V/cell.

This is why dissimilar cells or different numbers in series of similar cells are never run in parallel.

Yes, getting more of one type of module and abandoning the idea of connecting dissimilar modules in parallel is the logical solution. You could modify one Volt module per string (pack) to remove 5 cell groups so you have 31S in each, matching the Smart modules. You could also use separate contactors for a Volt pack and a Smart pack, and use or charge only one at a time, but I think that's a miserable kludge.
Thanks for the explanation and I will look into these options.
 

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Discussion Starter · #17 ·
At 127 volts, the 36 cells of the Volt modules will be at 3.52 volts per cell, which is well under the nominal voltage so substantially less than half charged. The overall voltage of each pack or string is identical, because they are all paralleled together. At that same 127 volts, the 31 cells of the Smart modules will be at 4.1 volts per cell, which is nearly fully charged. Operate them together, and before you have used half of the charge in the Smart modules the Volt modules will be completely discharged and in danger of being damaged if you try to go any further. At about half-charged the Smart modules will be at 3.7 V/cell or 115 V, which for the Volt modules will be 3.19 V/cell... and the energy.gov report for the 2013 Volt says the minimum is 3.0 V/cell.

This is why dissimilar cells or different numbers in series of similar cells are never run in parallel.

Yes, getting more of one type of module and abandoning the idea of connecting dissimilar modules in parallel is the logical solution. You could modify one Volt module per string (pack) to remove 5 cell groups so you have 31S in each, matching the Smart modules. You could also use separate contactors for a Volt pack and a Smart pack, and use or charge only one at a time, but I think that's a miserable kludge.
I was looking at the spec on the VOLT modules I am running to make my packs and this site has them rated as:

1) Chevy Volt 6s3p battery module, nominal voltage is 22.2volts to 24volts, 45AH = Total 1kw of power. Fully charged 25.2volts. Recommend to only charge up to 4.0-4.1volts per cells to prolong life and discharge down to 3.0v-3.3volts.

2) Chevy Volt 12s3p battery module, nominal voltage is 45volts to 48volts, 45AH = Total 2kw of power. Fully charged 48volts - 50volts. Recommend to only charge up to 4.0-4.1volts per cells to prolong life and discharge down to 3.5-3.7volts.

I have a 24 + the two 48 volts all in parellel which = 25.2 + 50 + 50 = 125.2

I am still looking into the other options as I wouldn't mind 2 contactors and building a 144 volt battery to run the car on on addition to the 127 volt.
 

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I was looking at the spec on the VOLT modules I am running to make my packs and this site has them rated as:

1) Chevy Volt 6s3p battery module, nominal voltage is 22.2volts to 24volts, 45AH = Total 1kw of power. Fully charged 25.2volts. Recommend to only charge up to 4.0-4.1volts per cells to prolong life and discharge down to 3.0v-3.3volts.

2) Chevy Volt 12s3p battery module, nominal voltage is 45volts to 48volts, 45AH = Total 2kw of power. Fully charged 48volts - 50volts. Recommend to only charge up to 4.0-4.1volts per cells to prolong life and discharge down to 3.5-3.7volts.
That's about 1 kWh of energy (not kW of power) for the 6S3P module, and about 2 kWh of energy (not kW of power) for the 12S3P module.

Yes, the high limits of the voltage range look generally reasonable. The voltage per cell is the same regardless of how many are connected, so they are the same between the two modules - there is no reason to have different low limits for the two module sizes.

The nominal voltages are not 24 V and 48 V. People like to call them that because they think all batteries should be a multiple of 12 volts, but they're just not.

This is a handy GM overview of the Volt batteries (both generations; you are looking at the first generation): VOLT_BATTERY.pdf

I have a 24 + the two 48 volts all in parellel which = 25.2 + 50 + 50 = 125.2
As already noted, voltages add when modules are connected in series. Two 12S3P (at 45 V each) plus one 6S3P (at 22.5 V) all in series would have a nominal voltage of 112.5 V; fully charged at 4.0 to 4.1 V would be 120 to 123 V.
 
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