[swoozle]

I've reconfigured a Volt pack into two parallel strings of 3 45V modules and 1 22V module (2 separate 42S3P strings).

Is there any advantage or disadvantage to making parallel connections between the two strings at the module terminals?

See attachment.

 

[swoozle]

The battery heater/temp sensor outlet thread is apparently the same as a 3/4 garden hose thread (3/4-11.5NH). It's easy to find a hose-barb / threaded adapter. This one happens to be nylon and with a little thread removal seems to hold the o-ring just fine, though I have yet to pressure test it.

 

[BogdanT]

I've reconfigured a Volt pack into two parallel strings of 3 45V modules and 1 22V module (2 separate 42S3P strings).

Is there any advantage or disadvantage to making parallel connections between the two strings at the module terminals?

See attachment.

Is it just me or you shouldn't parallel between modules for your setup. You will destroy the 6s as it's only 22.5V, others are 45V

 

[swoozle]

Is it just me or you shouldn't parallel between modules for your setup. You will destroy the 6s as it's only 22.5V, others are 45V

At each parallel connection the voltage is the same.

 

[brian_]

Is it just me or you shouldn't parallel between modules for your setup. You will destroy the 6s as it's only 22.5V, others are 45V

Are you confusing parallel and series?

• The 6s modules are in parallel only with each other, so they see the same voltage and there is no problem.
• Of course the 6s modules are in series with 12 s modules, but all modules have the same capacity (all cells identical and 3 parallel cells in every module) so the fact that they pass the same current is appropriate.

 

[BogdanT]

Sorry guys, I swear I saw a 6S in parallel with a 12S. But there's no such thing, so I should probably stop posting before I have my coffee in the morning.

 

[arber333]

Are you confusing parallel and series?

• The 6s modules are in parallel only with each other, so they see the same voltage and there is no problem.
• Of course the 6s modules are in series with 12 s modules, but all modules have the same capacity (all cells identical and 3 parallel cells in every module) so the fact that they pass the same current is appropriate.

Theoreticaly it should be good, BUT reality can make us fools. The 12S modules have higher potential than 6S and as such have higher tendency for voltage to vary during acceleration/regen. dU means dI and so there could be some amps flying inside cell connections unaccounted for. Maybe it would be a good idea to also parallel individual cells to lower dU between modules.

I have one Ampera battery and after i convert my car i intend to add another one to have 32kWh of energy. How i will do it is still not clear to me. I would rather not take apart this very sturdy system. But space and parelelling consideration may demand i take apart the cells and connect them first in paralell and then in series for 96S6P battery.

If you can demonstrate that as you propose in plan B is good, i can try the same.

 

[swoozle]

I'm going to use an ADC to monitor module temps with the built-in thermistors. Are there practical limits/guidelines for running the sensing wires?

Like will I be ok with a 3' wire run from the modules to the ADC?
Is it adequate to twist the pair or does it need to be shielded?

 

[Emyr]

I'm going to use an ADC to monitor module temps with the built-in thermistors. Are there practical limits/guidelines for running the sensing wires?

Like will I be ok with a 3' wire run from the modules to the ADC?
Is it adequate to twist the pair or does it need to be shielded?

It's generally better to have shorter analogue sections and longer digital sections than vice versa so you don't have to take account of voltage drop and noise between the sensor and the ADC.

 

[swoozle]

I'm going to use an ADC to monitor module temps with the built-in thermistors. Are there practical limits/guidelines for running the sensing wires?

Like will I be ok with a 3' wire run from the modules to the ADC?
Is it adequate to twist the pair or does it need to be shielded?

To answer my own question:
https://electrical-engineering-portal.com/thermistor-motor-protection

"Some practical recommendations for the type of cables that should be used are as follows:

Distances ≤ 20 m – Standard parallel cable is acceptable
Distances ≥ 20 m, ≤100 m – Twisted pair cable is necessary
Distances ≥ 100 m – Screened twisted pair (STP) cable is necessary
High level of interference – Screened twisted pair (STP) cable is necessary
The screen should be earthed at one end only."

 

[inwo]

Of course it's better to parallel connect. Impossible to maintain long term balance without connecting as in bottom drawing.
Best is to connect cell to cell parallel, then there are only 42 cells to watch.



https://www.ebay.com/itm/232719725165

 

[arber333]

So using the stock LG BMS system (as a complete setup) is very straight forward, just connect power and a 500kbps CAN receiver (diagrams are in this thread somewhere.) The BMS automatically spits out voltage and current data for the whole pack CAN ID 0x210 and individual cell voltages in CAN ID 0x200, 0x202, 0x204, 0x206. I should draw a diagram on how the data is packed in to the bits since it is rather tricky to explain, if you charge/discharge the pack and watch the binary data the boundaries are very clear... just binary values counting basically. Look for the bits that toggle the most they are the LSB's and the rest falls into place fast.

If however you just want to use one BMS sub-module then that is harder, I have kinda worked out part of that communication process on 125kbps CAN but that involves writing CAN packets and gets complicated fast. At this time I have decided using the whole thing as one pack works fine for my UPS backup (with a 360v to 12v DC to DC) and breaking it down in to smaller modules would take time I would rather spend on other activities

I am trying to use complete Volt/Ampera battery with BMS.
Can you describe where in msg 0x210 is the voltage of complete pack? Also the pack current? I would need that for EVTVdue BMS/Charger/Alarm controller.
Do you have any references to other values?
Do you know maybe if Volt BMS ever balances cells?
Is there automatic balancing command? Is there a command to switch charger off? Is there a command to reduce power to car?

tnx

Arber

 

[Thomasa]

In my 3 year , 8000 mile, 750 charge experience: you are being too paranoid.

I pull 400 amps for 6 minutes on monster hill. Longer if I get caught at the red light 1/2 way up. The pack temp rises ten degrees.

Figure 10% reduction in everything when they are below 60 f. I DONT cool when ambient is below 60f seems like a waste.

My $0.02 YMMV

 

[electricsailor]

Question; I'm using a 7 Kw group of Volt batteries and might have overcharged them. I'm measuring 4.63 volts from most of the cells. Is that too high?

 

[arber333]

Question; I'm using a 7 Kw group of Volt batteries and might have overcharged them. I'm measuring 4.63 volts from most of the cells. Is that too high?

Discharge the whole group at once to cca 3.8V per cell! The longer you keep cells so high the worst the damage will be.

A

 

[jon volk]

Having stumbled my way through this whole thread, there is still something I am a bit unclear on. If I use the Volt battery pack as configured from the factory, does the main BMS require any external input if you are just letting it maintain the individual cells. I understand the connections required to read the CAN messages, but is it essentially internally powered and autonomous in its normal day to day function? I hope it makes sense what Im asking.

 

[swoozle]

Not to ignore your question, but I don't know the answer. I'm going to use just the slaves since my pack is chopped up.

Another question: why have the number of volt packs on car-part.com dropped to almost none? When I started looking in July-ish there were a dozen (and I picked one up). Now there are very few to none. Is it seasonal? I need another.

 

[piotrsko]

Because everybody and their brother are buying them for cheap solar storage.

They also didn't make a million Volts, and the people who tend to wreck cars have been pretty much been weeded out by now.

Waiting IS.

 

[Mandres]

Would it be ok to run these modules mounted upside down (with the terminals pointed towards the ground)?

They'll fit into my motorcycle frame much easier if I can stagger the modules one up, one down so that the cooling passages nestle together.



Do pouch cells care which way they're mounted?

 

[brian_]

Would it be ok to run these modules mounted upside down (with the terminals pointed towards the ground)?

An extreme example of packing Volt modules into a car is the work mfor100 has done in his 911 RSR with Tesla Motor...; the module mounting arrangements for front and rear are shown in post #51 and post #80.

Do pouch cells care which way they're mounted?

I can't think of any reason why orientation would matter to the cells. Structure and cooling arrangements for the modules might be more of a concern, although that 911 shows that that they don't need to be upright.