Onboard charger.

2074 Views 12 Replies 3 Participants Last post by brian_, Nov 30, 2020

Krash.32766

Discussion Starter · Nov 29, 2020

I have 1967 VW Beatle that I am converting to electric. I have a D&D 72V DC Motor, Alltrax Controller SPM 72400, contactor is SW 180 with coil Suppression Diode and pre charge resistor. Batteries are out of 2013 Chevy Volt(lithium cobalt) have 6-72 Volt Packs that run the car.

I am having a hard time trying to find an onboard charger that will work with my system. I hope you guys can help? I was looking at your TSM2500 and was wondering if this will work>? I am looking for something that will work in normal 110V household outlet.

1-72 pack have: 18cells
3 KWh each
70 AH
Average/nominal charge 3.8VDC

Any help recommendations with Charger/BMS would be appreciated.

Im new to the EV Build and need assistance/direction on chargers & BMS? Thanks

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brian_

· #2 · Nov 29, 2020

I'm puzzled where the 70 AH value comes from. The first-generation Volt modules have about 45 Ah capacity (from roughly 15 Ah cells paralleled in threes), resulting in about 3 kWh for an 18S 67 V combination (and 16 kWh for the whole 96S 360 V battery); to get any other amp-hour capacity you would need to modify the welded cell tab connections or parallel modules.

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Krash.32766

Discussion Starter · #3 · Nov 29, 2020

brian_ said:
I'm puzzled where the 70 AH value comes from. The first-generation Volt modules have about 45 Ah capacity (from roughly 15 Ah cells paralleled in threes), resulting in about 3 kWh for an 18S 67 V combination (and 16 kWh for the whole 96S 360 V battery); to get any other amp-hour capacity you would need to modify the welded cell tab connections or parallel modules.

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Krash.32766

Discussion Starter · #4 · Nov 29, 2020

I’m new to this and still learning. I have 72v. 1-48V and 1-24v together I thought that was the proper AH. It is 3kwh.

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brian_

· #5 · Nov 29, 2020

Krash.32766 said:
I’m new to this and still learning. I have 72v. 1-48V and 1-24v together I thought that was the proper AH. It is 3kwh.

Okay... but where did you get that 70 Ah value? If a battery has a nominal voltage of 72 V (which this doesn't, but we'll get to that) and a nominal energy storage of 3 kWh, then it must have an amp-hour capacity of
3,000 Wh / 72 V = 41.7 Ah
because one amp flowing from a battery at one volt is one watt of power. Either the voltage, or the amp-hour capacity, or the energy capacity is incorrect.

Many people refer to the 12S modules as "48 volt", but that would be the fully charged voltage (4.0 V/cell), not the nominal voltage (somewhere between fully charged and fully discharged) of 3.75 V/cell. The GM specs for this battery (like most modern EV batteries) say that the battery, with 96 groups of cells in series, has a nominal voltage of about 360 V, so
360 V / 96 cell groups = 3.75 V/cell
... which is about the 3.8 V that you are expecting.

So the 12S3P modules (12 groups of 3 cells) have a nominal voltage of 12 cell groups * 3.75 V/cell = 45 V, and
the 6S3P modules (6 groups of 3 cells) have a nominal voltage of 6 cell groups * 3.75 V/cell = 22.5 V
Yes, they will need 48 V and 24 V to charge fully, so the charger needs to be able to deliver about 72 V if you combine those two modules in series. That part is right.

As described in a useful GM publication 2016 Chevrolet Volt Battery System, the entire first-generation Volt battery has

Usable Energy 10.2 – 11.2 kWh
Total Energy 16.0 – 17.1 kWh

Depending on where in the range your particular battery falls, and whether you are counting the entire capacity or what the Volt actually uses, that's 28.3 Ah to 47.5 Ah, and normally the full capacity is reported and the Volt battery is considered to have a 16 kWh energy capacity, so that's 44.4 Ah.

With 44.4 Ah capacity and 67.5 V nominal voltage, the combination of the two modules has an energy capacity of
44.4 Ah * 67.5 V = 3 kWh
so that energy capacity value is right, too.

But when you're charging this combination of modules, from fully discharged to fully charged, you need to deliver about 45 Ah, not 70 Ah.

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brian_

· #6 · Nov 29, 2020

Krash.32766 said:
I hope you guys can help? I was looking at your TSM2500 and was wondering if this will work>? I am looking for something that will work in normal 110V household outlet...

Presumably this was originally written as a query to the manufacturer of a charger, and presumably that was Thunderstruck:
TSM2500 and Charge Controller

The description says that you can program the specific output voltage that you want. The chart on that web page says that the "110Vac" and nominally 72 V output model can put out up to 25 amps, but at anything above 60 volts the current will be reduced because it is limited to 1.5 kW (since it is designed for a 15 amp AC supply, which is a "normal 110V household outlet"). By 72 volts it will be down to 20.8 amps at the most.

It would take at least a couple of hours to fully charge a 72 V 44 Ah module set, and more than 12 hours to charge your entire set of six sets of modules... of course, since you have 18 kWh of battery and the charger is limited to 1.5 kW.

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Krash.32766

Discussion Starter · #7 · Nov 29, 2020

brian_ said:
Presumably this was originally written as a query to the manufacturer of a charger, and presumably that was Thunderstruck:
TSM2500 and Charge Controller

The description says that you can program the specific output voltage that you want. The chart on that web page says that the "110Vac" and nominally 72 V output model can put out up to 25 amps, but at anything above 60 volts the current will be reduced because it is limited to 1.5 kW (since it is designed for a 15 amp AC supply, which is a "normal 110V household outlet"). By 72 volts it will be down to 20.8 amps at the most.

It would take at least a couple of hours to fully charge a 72 V 44 Ah module set, and more than 12 hours to charge your entire set of six sets of modules... of course, since you have 18 kWh of battery and the charger is limited to 1.5 kW.

That’s a lot of information. I see a big learning curve ahead. So if I get a charger that is 72V and a 3kw that should improve my charging time. BMS will help in overcharging. Now I need to find something that will work in this parameters. Any suggestions on a charger and BMS for this set up?

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Krash.32766

Discussion Starter · #8 · Nov 29, 2020

Krash.32766 said:
That’s a lot of information. I see a big learning curve ahead. So if I get a charger that is 72V and a 3kw that should improve my charging time. BMS will help in overcharging. Now I need to find something that will work in this parameters. Any suggestions on a charger and BMS for this set up?

From my undertanding the Thunderstruck charger and BMS will work but living in Canada with exchange rate and shipping it’s getting up their in price. I’m looking for a different option and also to help understand/learn for next build.

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remy_martian

· #9 · Nov 29, 2020

Krash.32766 said:
I’m new to this and still learning. I have 72v. 1-48V and 1-24v together I thought that was the proper AH. It is 3kwh.

You realize that's about 12-15 miles of range? In warm weather.

With no accessories running. Zero miles if you have a/c

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Krash.32766

Discussion Starter · #10 · Nov 30, 2020

remy_martian said:
You realize that's about 12-15 miles of range? In warm weather.

With no accessories running. Zero miles if you have a/c

I have 4 packs running at the moment get 60kms now. Thinking with all 6 90-100kms.

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brian_

· #11 · Nov 30, 2020

Krash.32766 said:
So if I get a charger that is 72V and a 3kw that should improve my charging time. BMS will help in overcharging.

Yes, double the charger power - which will require a 240 V supply circuit - will cut charging time roughly in half. That part is reasonably straightforward.

The job of the BMS includes telling the charger what current to charge at and when to stop.

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remy_martian

· #12 · Nov 30, 2020

So each "pack" (actually "module"....pack is the whole shebang) is 3kW, then

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brian_

· #13 · Nov 30, 2020

remy_martian said:
So each "pack" (actually "module"....pack is the whole shebang) is 3kW, then

It's not one module, as each 3 kWh 67 V portion is a combination of two modules in series (12S3P 2 kWh 45 V module plus 6S3P 1 kWh 22.5 V module for 18S3P in combination). If that combination is in its own enclosure, it's a pack.

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