[cbrbob]

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.

 

[cbrbob]

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

 

[cbrbob]

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 .

https://www.energy.gov/sites/prod/files/2015/02/f19/batterySmart5544.pdf

 

[cbrbob]

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

 

[cbrbob]

I don't think popcorn is necessary, I am asking to learn. This is my first conversion and open to suggestions and input, if I don't ask I may never know.

 

[cbrbob]

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.

 

[cbrbob]

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.

 

[cbrbob]

Shouldn't <in parallel> be <In series>?
Later floyd

I think you are correct, my diagram is wrong. the two Volt packs are supposed to be in series and all the tied batteries are wired in parallel to achieve the amp-hours.
BOb

 

[cbrbob]

I think it is all wired right, here is a picture of the Battery meter.