Newb Asks: Can we charge a BMW PHEV single cell module with a bench power supply? Topic is solved

[Gregski]

In this thread we ask and hopefully answer the question: Can we take one of the BMW plug in hybrid 60 volt cell modules and charge it using a dime a dozen 300 watt 60 volt 5 amp bench power supply?

won't you please follow along...

[Gregski]

So a little background: I bought a 2018 BMW 530e battery pack for $900 bones on eBay last year. I know nothing about BMWs but I think that's something called a 5 series, anywho that car comes with a six pack of these modules like so

[Gregski]

We can source a similar pack from the 740e and the X5, the 330e aka it's little brother comes with the same modules but only five of them


X5 pack

330e pack

[Gregski]

alright, enuff of the Captain Obvious, so as per the sticker two posts up, my back ie the 530e six module one states it is 351.36 volts, we do some quick maths here (take that number and divide it by six modules) giving us 58.56 volts per module

and just to level set on the naming convention, right or wrong (and please correct me if I am wrong)

the big box I call the battery pack (our larger unit of measurement), inside of it there are six cell modules, inside of these modules are cells (the lower unit of measurement as far as I am concerned)

[Gregski]

Now I have two different bench power supplies (trust me I'm not bragging) they are both 300 watts, however one is 30 volts and 10 amps and the second one is 60 volts and 5 amps. So, can anyone chime in and tell us why we couldn't or could we use the 30 volt 10 amp bench power supply to charge one of these modules, I mean they are both the same power rating? are they not

[arber333]

Edit: speaking about 60V unit...
Nothing wrong with that assumption. But without some voltage controlled relay you would be charging at CV constant voltage. E.g. you would set 64V (as that is 16S value of 4V per cell) and your device will charge at 5A first. As you get closer to 64V psu will drop amps to keep the same voltage. And that equalization can take a long time.
Still i wouldnt just leave the device connected and go to sleep...

What i did was to buy a 5A 16S ebike/scooter charger which is CC constant current and i use it to charge 16S modules up to some 4V per cell. This one stops charging as it sees 65V on the battery.

I can use it to charge 12S module too, but i wouldnt dare leaving it without supervision since it would have no way of stopping from overcharging the 12S module.

[arber333]

So, can anyone chime in and tell us why we couldn't or could we use the 30 volt 10 amp bench power supply to charge one of these modules....

Well for one the insides of the 30V unit will most likely fold under higher voltage. If not you will get a OV err.. overvoltage error which will stop the unit.

Go with 60V unit not less..

[Gregski]

Edit: speaking about 60V unit...
Nothing wrong with that assumption. But without some voltage controlled relay you would be charging at CV constant voltage. E.g. you would set 64V (as that is 16S value of 4V per cell) and your device will charge at 5A first. As you get closer to 64V psu will drop amps to keep the same voltage. And that equalization can take a long time.
Still i wouldnt just leave the device connected and go to sleep...

thank you for your feedback as always, question for you if my bench power supply maxes out at 60 volts then I am unable to set it to 64, were you thinking of using a different bench power supply to reach that magic number?

[Gregski]

alright time for some homework, there are two generations of this battery pack up until mid 2019 it was the 3.0 technology version called SP06 and starting in July 2019 it was replaced with the next version called the SP41, we will focus on the SP06 in this thread (because that's what I have) I wish I had the other one

[arber333]

Edit: speaking about 60V unit...
Nothing wrong with that assumption. But without some voltage controlled relay you would be charging at CV constant voltage. E.g. you would set 64V (as that is 16S value of 4V per cell) and your device will charge at 5A first. As you get closer to 64V psu will drop amps to keep the same voltage. And that equalization can take a long time.
Still i wouldnt just leave the device connected and go to sleep...

thank you for your feedback as always, question for you if my bench power supply maxes out at 60 volts then I am unable to set it to 64, were you thinking of using a different bench power supply to reach that magic number?

Hah, usually those power units max out at 63Vdc so you can still use them up to that point. But again i would suggest you to buy a 16S charger for your modules.
https://www.aliexpress.com/item/1005003 ... 4821%21sea

https://www.aliexpress.com/item/3298857 ... 1597%21sea

Or something with more omph!
https://www.aliexpress.com/item/1005004 ... 6192%21sea

Later on you can buy 5A charger for 1S if you need to rebalance single cells in your pack.

[Gregski]

more maths, so per the specs above (you can take it or leave it, ha ha) we can charge the entire pack up to 398 volts, so if we divide that by six modules, we get 66.33 volts per module, good to know, but keep in mind our bench power supply only goes to 60 volts

ok now lets compute the lowest value, so we take 269 volts and divide that by six modules and we get 44.83 volts so that's our floor, now something I learned a while back using a regular acid car battery that first of all although we call it a 12 volt battery it is really made up of six cells of about 2.1 volts each so it's really 12.6 volts and just Googling around to confirm, at 11.9 volts it is considered dead, (yes I know we are comparing apples and bowling bowls here in terms of battery technology) but the point I am trying to make is that a battery is not dead when it reads 0 volts, regardless of what kind it is

so...

66 volts = fully charged
45 volts = kaput

[Gregski]

Edit: speaking about 60V unit...
Nothing wrong with that assumption. But without some voltage controlled relay you would be charging at CV constant voltage. E.g. you would set 64V (as that is 16S value of 4V per cell) and your device will charge at 5A first. As you get closer to 64V psu will drop amps to keep the same voltage. And that equalization can take a long time.
Still i wouldnt just leave the device connected and go to sleep...

thank you for your feedback as always, question for you if my bench power supply maxes out at 60 volts then I am unable to set it to 64, were you thinking of using a different bench power supply to reach that magic number?

Hah, usually those power units max out at 63Vdc so you can still use them up to that point. But again i would suggest you to buy a 16S charger for your modules.
https://www.aliexpress.com/item/1005003 ... 4821%21sea

https://www.aliexpress.com/item/3298857 ... 1597%21sea

Or something with more omph!
https://www.aliexpress.com/item/1005004 ... 6192%21sea

Later on you can buy 5A charger for 1S if you need to rebalance single cells in your pack.

thank you so much (especially for taking the time to provide direct links) this is exactly why I started this thread, it is to vet all these options

I am still going to try charging with this bench power supply but now I know not to leave it on over night, ha ha

[arber333]

There is a way to up the voltage my padawan, though it lies on the edge of shadow....

If you wire TWO yes TWO power supplies in series, your battery will see it as a single source. PSU1+ to battery+, PSU1- to PSU2+ and PSU2- to battery-. If you have two PSUs of the same rating is the best, but not limited to. As long as you set the current under the level of LOWEST rated unit.
I wouldnt recommend it though since those PSUs output PWM and that can have unpredictable results. Allways supervise that kind of twisted application!

[Gregski]

There is a way to up the voltage my padawan, though it lies on the edge of shadow....

If you wire TWO yes TWO power supplies in series, your battery will see it as a single source. PSU1+ to battery+, PSU1- to PSU2+ and PSU2- to battery-. If you have two PSUs of the same rating is the best, but not limited to. As long as you set the current under the level of LOWEST rated unit.
I wouldnt recommend it though since those PSUs output PWM and that can have unpredictable results. Allways supervise that kind of twisted application!

danger I sense in your method... go on!

yoda.jpg (11.71 KiB) Viewed 9217 times

[Gregski]

assuming nothing we begin with a gently PSU tutorial

[Gregski]

Still i wouldnt just leave the device connected and go to sleep...

ok, need a point of clarification, if my PSU maxes out at 60.5 volts (I just confirmed with a volt meter) and this cell module can be charged up to 66 volts, why can't I leave it charging over night? it will never get to 66 volts, so essentially it will end up trickle charging no?

[arber333]

Still i wouldnt just leave the device connected and go to sleep...

ok, need a point of clarification, if my PSU maxes out at 60.5 volts (I just confirmed with a volt meter) and this cell module can be charged up to 66 volts, why can't I leave it charging over night? it will never get to 66 volts, so essentially it will end up trickle charging no?

Ah in that case OK. You shouldnt have a problem except if several of your cells would be heavily unbalanced.

[mjc506]

How much do you trust your PSU not to go 'pop' and start dumping rectified mains into that BMW module?

The likelyhood is low, but do consider how much energy is stored within that shoebox-sized lump of battery. You could probably calculate how hot it could possibly get if all that energy turned into heat for some reason...

[Gregski]

How much do you trust your PSU not to go 'pop' and start dumping rectified mains into that BMW module?

The likelyhood is low, but do consider how much energy is stored within that shoebox-sized lump of battery. You could probably calculate how hot it could possibly get if all that energy turned into heat for some reason...

wouldn't a pair of 5 amp fuses, on one each on the PSU leads running to the battery module address that

[Gregski]

alright so lets baseline this cell module aka "shoebox" ha ha

57.9 volts

do some quick math 57.9 times six modules puts us at 347.4 volts for the entire pack

[Gregski]

now this is where things get interesting (pronounced: confusing) I hooked up one of them cheap Chinese DC 12V 24V 36V 48V 72V Battery Meter, Battery Capacity Voltage Monitor Gauge Indicator, Lead-Acid & Lithium ion Battery Tester, for Golf Cart RV Marine Boat Club Car Motorcycle - With Alarm, Green

it read a bit higher at 58.1 volts (but that's not the issue/concern) the part that it thinks it is fully 100% charged is since that only puts the pack at 348.6 volts not even at the 351.36 nominal???

FYI I did not go out and purchase this monitor for this battery it's just something I had laying around from a solar panel project.

[Gregski]

commencing the experiment, charging at max voltage with Constant Current capped at 1 amp (baby steps)

I love these Killer Whale as I call 'em inline Alternating Current meters and I prefer the genuine KILL A WATT units over the generic knock offs with multi buttons where you have to press the same button over and over to toggle through a function, I'm a simple man I want Volts I press the Volts button, I want Amps, I press the Amps button, etc. (I wish I could find a US 240 volt version of one of these, holler at me if you know of one)

so here we are pulling 1.15 amps AC at 120 volts from "the wall"

this translates to 1 amp DC at 58.2 volts (via the power of the flux capacitor I guess)

looks like my Chinese power meter decided to play ball and report the same voltage as the bench power supply, nice going little guy, nicely done

[Gregski]

what do you say we go crazy and double our amperacis input

so this is interesting, from what I watched on YouTube (and we're talking minutes of research...) I expected the volts to drop as the current went up, I mean did Georg lie to us or what I thought a law was a law

ok so now we are pulling 2.03 AC amps from the wall

[remy_martian]

"I expected the volts to drop as the current went up, I mean did Georg lie to us or what I thought a law was a law"

Voltage across a resistor increases with current per Georg Ohm's Law.

Go watch a Youtube video about Gustav Kirchhoff's Law if you want to be qualified to expect voltage drops.

You can't practice law if you've only read about one law in your career.

[Gregski]

and here's what the numbers looked like at 3 amps DC

so we were pulling 2.9 amps AC (from the wall)

and the battery voltage read 58.3