Who has experience with (blue) aluminum cells in a mobile system?

[BiduleOhm]

Yep, that would definitely be a factor, but the offset is pretty constant so my guess is that calibration is the biggest factor here.

And yes, heating up air is a lot easier than eating up pretty much anything else, it has a much lower heat capacity.

 

[Sgt Raven]

It's likely the calibration of the temp sensors.

That's like my 2 different DMMs. They are reading 0.011 difference between the 2.
Which one is correct, or is either of them? Both have 3 1/2 displays....
If we weren't on quarantine, I'd take them over to a friend who has a bench full of "calibrated" test equipment for his design work.

 

[BiduleOhm]

Yeah 3 1/2 digits DMM are really bad for accuracy, but they are cheap and make great sacrificial meters when you want to measure things who might destroy the meter...

 

[Sojourner1]

Here is what the 1 of 20 senseboard looks like, front & back.

A couple components of the EMS (energy management system) of Elite GBS batteries which comes as a package.
*CPU: Central hub of the system, powered by 12 volts DC, controls alarm output signals, measures current, calculates state of charge, outputs video signal, detects ground fault conditions.

*Four cell sense board string x5 daisy chained, simple easy installation connected to the prismatic cells, measures voltage and temperature of each cell, performs cell balancing.

On the display screen there's the cell voltage/ temp screen or switch to the battery pack voltage, charge/ discharging current, SOC.

GBS uses a per cell sense boards for voltage and temperature, top balancing per cell shunts, a system shunt for current monitoring and coulomb counting (BMS) and 2 high current protective relays.
**Over voltage (highest cell is over 3.8V after a 3 second delay)
** Under voltage (lowest cell is below 2.8V after a 30 second delay)
** Over current (current exceeds 10C for 10 seconds)
**Over temperature (highest cell exceeds 150°F or 65°C)
**Under temperature (lowest cell is below 32°F or 0°C, charging is not allowed)
**Ground fault (There is a high voltage leakage greater than 2mA to the chassis pin)
**Unmanaged cells (The programmed number of cells does not equal the number of cells read)

 

[Sgt Raven]

Yeah 3 1/2 digits DMM are really bad for accuracy, but they are cheap and make great sacrificial meters when you want to measure things who might destroy the meter...

4-5 years ago I was looking at 5 1/2 or 6 1/2 bench DMMs on Craigslist and there was whole bunch of them. I wanted one with 4 wire ohm capability. I kinda got away from what I was doing and didn't buy one..... Now I'm back at it and the glut is gone...

 

[Dzl]

Yep, that would definitely be a factor, but the offset is pretty constant so my guess is that calibration is the biggest factor here.

And yes, heating up air is a lot easier than eating up pretty much anything else, it has a much lower heat capacity.

I have been kicking around an idea in my head for a while now about designing a semi-passively heated/cooled insulated battery compartment, using the losses of the SCC, Inverter, Converter, and other electronics, to heat the space in the winter, and a small PC exhaust fan that only kicks on when the exterior ambient temperature is above a certain threshold, and a small intake fan that make use of extended contact with cool thermal mass (possibly the vehicle frame rail) to slightly lower the intake air temp in the summer (based on this passive green building technique).

Not sure how effective it would be in practice, but I like the idea of reclaiming and harnessing the efficiency losses of the various electrical components.

 

[BiduleOhm]

Here is what the 1 of 20 senseboard looks like, front & back.

That poor little R8, left alone in the dark and the cold, away from its friends...

Ok, just joking a bit here ?

4-5 years ago I was looking at 5 1/2 or 6 1/2 bench DMMs on Craigslist and there was whole bunch of them. I wanted one with 4 wire ohm capability. I kinda got away from what I was doing and didn't buy one..... Now I'm back at it and the glut is gone...

A 4 1/2 digits (20 kcounts) handheld DMM is fine for 99.99 % of what you'll be doing. My main DMM is a Metrix MX-59HD which is 50 kcount, 0.1 % and TRMS. I'd like to have a 6 1/2 or 7 1/2 bench DMM one day but for now I have other priorities money wise.

I have been kicking around an idea in my head for a while now about designing a semi-passively heated/cooled insulated battery compartment, using the losses of the SCC, Inverter, Converter, and other electronics, to heat the space in the winter, and a small PC exhaust fan that only kicks on when the exterior ambient temperature is above a certain threshold, and a small intake fan that make use of extended contact with cool thermal mass (possibly the vehicle frame rail) to slightly lower the intake air temp in the summer (based on this passive green building technique).

Not sure how effective it would be in practice, but I like the idea of reclaiming and harnessing the efficiency losses of the various electrical components.

You can totally do that, you just need to insulate the whole compartment instead of just the battery. BTW, if you need to rely on fans just put two of them, one on each other, because a fan will fail sooner or later... I know it'll suck twice the power for little to no additional airflow but you have redundancy that way

 

[Sgt Raven]

A 4 1/2 digits (20 kcounts) handheld DMM is fine for 99.99 % of what you'll be doing. My main DMM is a Metrix MX-59HD which is 50 kcount, 0.1 % and TRMS. I'd like to have a 6 1/2 or 7 1/2 bench DMM one day but for now I have other priorities money wise.

Back then I was Vaping, building my own coils at 0.20 ohms or less and using a mechanical Mod, which is just a battery and a switch.. Going down that low, you needed accurate ohm reading in Milliohms... When you're working with 0.1XX ohms, accuracy become important so you don't turn a 18650 into a torch or bomb.... Then the Regulated Box Mods came out and took over the sub-ohm Vaping scene and I didn't need a Milliohm meter anymore...

 

[BiduleOhm]

I would have made a precision current source and mesured the voltage, then Ohm's law.

 

[Sgt Raven]

I would have made a precision current source and measured the voltage, then Ohm's law.

Like this? I have the parts and PC Board, just needed the digital panel meter and a couple of switches...
Lost interest before I got it soldered up...
Since joining here and getting back into it, I'm planning on putting it together, too..
Now that I bought a Soldering Station, I have all the tools I need for it.....

 

[BiduleOhm]

I would not qualify a LM317 + trimpots as precision (between the long term drift and the tempco...) but yep, that would work

Also the LM317 will be very limited current wise, 5 or 10 A would be better for your application.

 

[Sgt Raven]

I would not qualify a LM317 + trimpots as precision (between the long term drift and the tempco...) but yep, that would work

Also the LM317 will be very limited current wise, 5 or 10 A would be better for your application.

The guy who designed the circuit and I got the parts from gave me a high quality low ohm resistor to use when I calibrate the system.

 

[BiduleOhm]

Well, you can always calibrate the circuit before each measurement but that will get annoying pretty quickly...

 

[Sgt Raven]

Well, you can always calibrate the circuit before each measurement but that will get annoying pretty quickly...

I just figure it's a lot better than my 3 1/2 DMM 2 wire ohm meter. I'd probably calibrate it when I first start the days work....

 

[BiduleOhm]

Yep, you can probably achieve 1 % short term accuracy.

 

[Sojourner1]

Here are some readings from consecutive days back in November 2018 where outside temps where in 32f +/- range. I wasn't as religious about recording the ambient temps like now. Also there was no supplemental heating going into the compartment other than what was generated by the IC, I added 2" foam board on the walls where I could. This also gives an idea of what my late fall to early spring PSOC living on the batteries are like when solar charging is shorter time period. If I used the generator it's for a couple hours to just put a hold over charge into the batteries.





Solar production during that period. The morning SOC is read after there is power being produced by solar, evening is read when solar production has stopped and using batteries. Times are in military format.(0536 is 5:36am, 1730 is 5:30pm)

 

[sduser]

Bumping this as this thread seems most relevant to my question. I am installing 70-100Ah @ 12V in a off road vehicle subject to higher vibration (washboard road, etc). I have limited space to work with. I purchased a few of the Valence U1-12RT but now I am thinking I want more capacity than two of those will offer.

After reading through this thread and others I am considering 4 of the 100Ah CALB or Al prismatic cells and making my own battery. I really like the robustness of the Fortune cells, but initially passed on them because they were too tall. However now I see the 60Ah fortune cells and based on rough measurements I think I can fit 8 of them end to end in a 4S2P configuration and only need one BMS.

8 of these cells:

Affordable Electric Vehicle Batteries & Components from Electric Car Parts Company

Electric Car Parts Company is your one-stop-shop for affordable electric vehicle parts and components including batteries. Shop our selection and order now!

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Configured like this


I am also concerned about the effects of vibration on the BMS. The BMS would most likely be secured to the end of cell 1.

Thoughts on how this would hold up in a vehicle?

 

[ghostwriter66]

Bumping this as this thread seems most relevant to my question. I am installing 70-100Ah @ 12V in a off road vehicle subject to higher vibration (washboard road, etc). I have limited space to work with. I purchased a few of the Valence U1-12RT but now I am thinking I want more capacity than two of those will offer.

After reading through this thread and others I am considering 4 of the 100Ah CALB or Al prismatic cells and making my own battery. I really like the robustness of the Fortune cells, but initially passed on them because they were too tall. However now I see the 60Ah fortune cells and based on rough measurements I think I can fit 8 of them end to end in a 4S2P configuration and only need one BMS.

8 of these cells:

Affordable Electric Vehicle Batteries & Components from Electric Car Parts Company

Electric Car Parts Company is your one-stop-shop for affordable electric vehicle parts and components including batteries. Shop our selection and order now!

www.electriccarpartscompany.com

Configured like this
View attachment 16979

I am also concerned about the effects of vibration on the BMS. The BMS would most likely be secured to the end of cell 1.

Thoughts on how this would hold up in a vehicle?

Just wrap the BMS in foam or something spongy ... as for off road 280 is the largest you should use -- anything larger the stuff inside just is to heavy to absorb being tossed around ...

 

[sduser]

Just wrap the BMS in foam or something spongy ...

That's a good idea thanks. I was thinking the B- and C- soldered connections.

 

[Sgt Raven]

That's a good idea thanks. I was thinking the B- and C- soldered connections.

The soldered connections on the Smart BMS w/BT are the last place I would expect a failure. If you watch OverKillSolar's video on changing the 10AWG cables to 8AWG, you will see how robust that connection is.