The perfect lithium battery box?

[Silver-Fox]

You need four cells to build a 300Ah battery, not just one, but still exceptional VFM if you are modestly competent with some simple assembly work…

Ahh thanks.

So not cheap but as you say good vfm

Think I need pictures and guidance like airfix or Lego

 

[MisterB]

Ahh thanks.

So not cheap but as you say good vfm

Think I need pictures and guidance like airfix or Lego

 

[Silver-Fox]

What Carpmart says. It needs 4 cells, a BMS board and some cables at a bare minimum then it is just crimping cables and assembly.
BUT there are plenty of places to screw it up and cause yourself issues. I have no idea of anyone's knowledge level when posting so...

If you are even mildly interested watch a lot of videos and if you still have questions perhaps it is not a DIY project for you.

If it were lead acid I would be suggesting having a go. But a shorted lithium battery is no joke at all.

My background is, I was a sparky by trade originally and an electronics engineer. I was also an electronics hobbyist from a very young age and a Radio amateur from 14.
My first job was at a transformer factory at 15 where I dealt with live wires with Extremely high voltages with big current capacities.
Although my memory of some of the technical details are fading and my knowledge of recent regulation are behind the times. I still retain enough knowledge and experience to be able to do this safely for myself.

I will try to be as detailed as possible when I start building. But it isn't likely to be until next week.

That special deal on the battery cells was an absolute cracker.

I’m reasonably handy, mech engineer by apprenticeship and retrained as a chippy.

I can rewire a house etc.
Plumbing isn’t an issue.
I do all mine and the families cars.

This battery building is probably lack of confidence more than ability
Like most things once you’ve had a go it all becomes clear

 

[Silver-Fox]

Thanks

Evening viewing

 

[Gromett]

It depends what you connect to it, when you turn it on for example connecting it to a 5kva inverter, the inrush current to fill the capacitors will trigger the sort circuit protection in the bms. I go in bms settings and change that to a double value, turn on the inverter, and then re instate the setting for short circuit in the bms.
It is very sensitive on large capacitors.

From memory the inrush current is more an issue for the solid state electronics and fuses rather than the contacts in a DC switch?

Disconnecting a full load on DC is an issue for the switch not the electronics?

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[Gromett]

I’m reasonably handy, mech engineer by apprenticeship and retrained as a chippy.

I can rewire a house etc.
Plumbing isn’t an issue.
I do all mine and the families cars.

This battery building is probably lack of confidence more than ability
Like most things once you’ve had a go it all becomes clear

In that case have at it .

 

[Jimbohorlicks]

Easy when all the bits are premade and just fit together.

 

[Gromett]

The batteries just arrived. First impressions.

VERY well matched cell voltages are
3.270V
3.270V
3.270V
3.271V

Smaller than I thought they would be even having looked a tape measure with the measurements in hand.
Heavier than I expect but still lower than a 110AH lead acid I think.

Only one minor concern. The QR codes have been physically scratched off. Is this normal for Envision B cells Raul do you know?

 

[hchris]

I have been watching this thread with interest I wondered what are your thoughts on the Fogstar kit in the video.
I have worked on and repaired woodworking and engineering machine controls for many years so I think I would be capable of building from scratch but the kit seems a easy way.
Thanks Chris

 

[Gromett]

I have been watching this thread with interest I wondered what are your thoughts on the Fogstar kit in the video.
I have worked on and repaired woodworking and engineering machine controls for many years so I think I would be capable of building from scratch but the kit seems a easy way.
Thanks Chris

I don't think you save that much money buying a kit?

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[Carpmart]

The batteries just arrived. First impressions.

VERY well matched cell voltages are
3.270V
3.270V
3.270V
3.271V

Smaller than I thought they would be even having looked a tape measure with the measurements in hand.
Heavier than I expect but still lower than a 110AH lead acid I think.

Only one minor concern. The QR codes have been physically scratched off. Is this normal for Envision B cells Raul do you know?

Have you tested the IR of each cell? That’s the part it’s key to have matched.

I’m not home to measure my cells for another month, but was wondering if the Fogster 280 enclosure EVE battery box would actually work with the 315 cells? With actual measurements (not published) to hand, could you have a check please?

280Ah ABS Empty DIY Cell Case

280ah LiFePO4 empty (ABS) cell case, holds four 280ah cells and a BMS, for DIY lithium battery builds. Next day delivery. Low prices - Fogstar UK.

www.fogstar.co.uk

 

[Gromett]

Have you tested the IR of each cell? That’s the part it’s key to have matched.

I’m not home to measure my cells for another month, but was wondering if the Fogster 280 enclosure EVE battery box would actually work with the 315 cells? With actual measurements (not published) to hand, could you have a check please?

280Ah ABS Empty DIY Cell Case

280ah LiFePO4 empty (ABS) cell case, holds four 280ah cells and a BMS, for DIY lithium battery builds. Next day delivery. Low prices - Fogstar UK.

www.fogstar.co.uk

I don't believe my multimeter can measure the internal resistance of a cell.

I don't know on the 280ah vs 305Ah question sorry.

 

[Raul]

Only one minor concern. The QR codes have been physically scratched off. Is this normal for Envision B cells @Raul do you know?

Yes QR scratched on B grades, but with a little sticker stating the actual capacity.
EVE's do keep the QR, with a capital B in it.
Resistance, I measured 0.18-0.2 miliohms each. EVE grade A measured 16-18 miliohms, slightly better but more dosh.
I do use a proprietary battery resistance meter with sensing leads, 4 wires, so is pretty close to accurate.

 

[Carpmart]

I don't believe my multimeter can measure the internal resistance of a cell.

I don't know on the 280ah vs 305Ah question sorry.

You mentioned the cells are physically smaller dimensions than you expected… would you mind stating what are actual dimensions please?

 

[Jimbohorlicks]

The batteries just arrived. First impressions.

VERY well matched cell voltages are
3.270V
3.270V
3.270V
3.271V

Smaller than I thought they would be even having looked a tape measure with the measurements in hand.
Heavier than I expect but still lower than a 110AH lead acid I think.

Only one minor concern. The QR codes have been physically scratched off. Is this normal for Envision B cells Raul do you know?

Did they come with anything else. Bus bars ? Etc.

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[Carpmart]

Did they come with anything else. Bus bars ? Etc.

Yes Jim, they come with bars and nuts to build up a pack from the individual cells…

 

[Gromett]

You mentioned the cells are physically smaller dimensions than you expected… would you mind stating what are actual dimensions please?

I had a tape measure out on my desk and plotted out the dimension in my mind.
The actual physical size just looks smaller than I imagined but were accurate to the spec.

 

[Gromett]

Did they come with anything else. Bus bars ? Etc.

An envelope with these in. herald_400rl was correct in post #13. I thought they only came when ordered separately or with full kits.
Nice to be wrong on this. Even nicer that they are shrink wrapped.

They are 2mm x 20mm. I got a file to the end of one and they are solid copper with what appears to be a pretty decent nickel coating.

I am pleasantly impressed with them.

 

[herald_400rl]

An envelope with these in. herald_400rl was correct in post #13. I thought they only came when ordered separately or with full kits.
Nice to be wrong on this. Even nicer that they are shrink wrapped.

The are 2mm x 20mm. I got a file to the end of one and they are solid copper with what appears to be a pretty decent nickel coating.

I am pleasantly impressed with them.

View attachment 1052667

I got some washers and split rings to stop the nuts rattling off, not tried to attach yet but I'm not 100% sure they'll fully latch before 8nm of torque is applied so might be useless.
I've also got some bars coming that are made of 2 x 1mm plates that have a little flex, I think that might stop the terminals breaking if it moves more than it should vs the terminals being expected to take all the shock as they'll be held solid with the provided bars.

 

[Carpmart]

I got some washers and split rings to stop the nuts rattling off, not tried to attach yet but I'm not 100% sure they'll fully latch before 8nm of torque is applied so might be useless.
I've also got some bars coming that are made of 2 x 1mm plates that have a little flex, I think that might stop the terminals breaking if it moves more than it should vs the terminals being expected to take all the shock as they'll be held solid with the provided bars.

You could use conductive thread lock when torqued up… it’s more like a two part epoxy, but would give you peace of mind…

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[Gromett]

You could use conductive thread lock when torqued up… it’s more like a two part epoxy, but would give you peace of mind…

Do you use anything? Split rings, thread lock etc?

I wasn't going to, I was just going to torque them correctly hence my new toy above.

Raul what do you do?

 

[Raul]

@Raul what do you do?

A bag of spring washers from screwfix and a bag of 6mm crimps for the bms leads. Nothing else, no torque, I use a very short 1/4" ratchet and I'm about 5-6nm, without forcing the ratchet, just tighten with two fingers. As long as is tight and marked with a pen, that way I know I haven't missed any.

I do have a torque screwdriver that I use in consumer units to torque the MCB's, as thats in the regs now, but I have a fairly good feel now for 5nm. No lube no grease no sprays, just let it be

In the JK bms app at the bottom of the status screen, you will have live resistance for the bms leads. If one is loose or bad contact it will reflect in the app:
Look at this screen and the resistance values, torqued by hand.

3 out of 4 are at 0.051 miliohms and one at cell 3 is 0.050 miliohms.
You wont get that with a cheap torque wrench.

 

[Gromett]

A bag of spring washers from screwfix and a bag of 6mm crimps for the bms leads. Nothing else, no torque, I use a very short 1/4" ratchet and I'm about 5-6nm, without forcing the ratchet, just tighten with two fingers. As long as is tight and marked with a pen, that way I know I haven't missed any.

I do have a torque screwdriver that I use in consumer units to torque the MCB's, as thats in the regs now, but I have a fairly good feel now for 5nm. No lube no grease no sprays, just let it be

In the JK bms app at the bottom of the status screen, you will have live resistance for the bms leads. If one is loose or bad contact it will reflect in the app:
Look at this screen and the resistance values, torqued by hand. View attachment 1052722

3 out of 4 are at 0.051 miliohms and one at cell 3 is 0.050 miliohms.
You wont get that with a cheap torque wrench.

I have not used a torque wrench for electrical work yet so I need to get the feel for what XNm is


I am not sure I am clear on what you do? Do you use an M6 bolt to hold the bars on, then the BMS terminal then a split washer and another nut?

 

[Gromett]

PS: I have always operated under the impression that you use a serated flange nut OR a split washer not both?

 

[Raul]

I have not used a torque wrench for electrical work yet so I need to get the feel for what XNm is


I am not sure I am clear on what you do? Do you use an M6 bolt to hold the bars on, then the BMS terminal then a split washer and another nut?

First use the bus bars to create the series connections of the cells. No need for any bolts as these cells have studs. After the bus bars, you are left with two terminals: one negative on cell no 1 takes the lug from the bms wires ( batyery side). The positive terminal ( cell4) takes another lug, where you gonna take it further to your fuse-breaker-switch etc. After that place all your crimped bms balancing and power leads ( 4 balance - 2 for power) to the relevant cells and terminals. After the bms leads, place a spring washer followed by the nut. If you dont like the serated nut, replace them with normal or nylon lock if you wish. Preferably stainless steel.

PS: I have always operated under the impression that you use a serated flange nut OR a split washer not both?

The reason you can't use the serated directly, is because the nut goes on top of the bms leads, that have fragile ring terminals. Its best to have a thin washer over this rings, and spring is even better. It holds down a good contact.

Have a browse through my media content, I have posted several photos with some of my builds, picture speaks a thousand words.

If you still want some fresh pictures with the 12v pack, when I get home next week I can post some.

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[StillGoing]

...hoping the the Fogstar beta turns out well non of the other aps allow viewing more than one at a time ( unless u know different)

Have a look at the POWERBELY app. It’s supports multiple batteries in series or parallel.

 

[oldiesontour]

Have a look at the POWERBELY app. It’s supports multiple batteries in series or parallel.

Thanks I'll give it a go in the morning

 

[Gromett]

First use the bus bars to create the series connections of the cells. No need for any bolts as these cells have studs.

I mispoke. I meant nut not bolt. Doh!! I should know better.

After the bus bars, you are left with two terminals: one negative on cell no 1 takes the lug from the bms wires ( batyery side). The positive terminal ( cell4) takes another lug, where you gonna take it further to your fuse-breaker-switch etc. After that place all your crimped bms balancing and power leads ( 4 balance - 2 for power) to the relevant cells and terminals. After the bms leads, place a spring washer followed by the nut. If you dont like the serated nut, replace them with normal or nylon lock if you wish. Preferably stainless steel.

I understand how to wire it. I was confused a little by your explanation. It seemed you were saying you were putting a nut on to hold the main cable/ bar, then the bms lead then another nut. Seemed odd to me? Sorry If I misunderstood.
I have two plans to try out.
1. Put the bar on then then the bms wires held on with a serrated flange bolt.
2. Drill and tap a smaller (M4? perhaps?) hole in the bar to fit the BMS wire to. I quite like this idea as I am not a fan of stacking lugs.

Anyway I personally would avoid nyloc nuts like the plague in any electrical situation. Any heat and they can lose their effectiveness increasing resistance and can enter a death loop. More heat, they get looser, more looser = more resistance = more heat etc etc.
And a melted nyloc is also a bugger to get off. In situations where I would want to use a nyloc but it is electrical I would alway err on the side of caution and use lock nuts. I love Nyloc's for anything mechanical but not on high current electrical stuff.

I prefer serrated flange nuts to a normal nut and a split/spring washer. Seems to get a much better contact surface area and is just as good at preventing it loosening. Split/spring washers only seem to come into their own once you get to M10 and over size. Below that they seem to compress fully flat at the right tightness If they are not fully flattened at any size then you are relying on the pointy bits digging in to a hard surface not the friction of the entire circumference. If they are fully flattened they appear to lose their effectiveness until they start coming undone. So they basically only become effective once they start loosening. I suppose in that respect they are a safety belt. whereas the serrated flanged nut grips tight the full circumference and digs in nicely (in the good quality ones) in multiple place all the way round.

The reason you can't use the serated directly, is because the nut goes on top of the bms leads, that have fragile ring terminals. Its best to have a thin washer over this rings, and spring is even better. It holds down a good contact.

Hmm, I will have to do some tests with the torque wrench. I have never had any problems with ring terminals and serrated flange nuts?

I can see some interesting tests coming up

Have a browse through my media content, I have posted several photos with some of my builds, picture speaks a thousand words.

I will have a browse this weekend.

If you still want some fresh pictures with the 12v pack, when I get home next week I can post some.

Thanks for the offer. I am more than curious

 

[Gromett]

Raul I couldn't remember the details last night. But I did a bit of searching today and this jogged my memory. It is called the Junker test.

Junker test - Wikipedia

en.wikipedia.org

I was 17/18 years old when I first heard about this and was taught not to use split washers.

I just tried to find some details and this is the best I could find quickly. It's an interesting read even if it doesn't convince you.

https://www.boltscience.com/pages/self-loosening-of-threaded-fasteners.pdf

I will be sticking with serrated flange nuts where I can

 

[herald_400rl]

Raul I couldn't remember the details last night. But I did a bit of searching today and this jogged my memory. It is called the Junker test.

Junker test - Wikipedia

en.wikipedia.org

I was 17/18 years old when I first heard about this and was taught not to use split washers.

I just tried to find some details and this is the best I could find quickly. It's an interesting read even if it doesn't convince you.

https://www.boltscience.com/pages/self-loosening-of-threaded-fasteners.pdf

I will be sticking with serrated flange nuts where I can

Interesting Gromett, I've got both on my list (one will be purchased). Makes sense that if split-rings wiggle loose a bit their contact patch is reduced but given they're sat on a washer and the busbar is pressed hard against the bottom of the threaded bar/terminal, is there likely to be much in the way of conductivity via the top of the bar through the split ring?

I'll go the same route as you, and am considering a jam nut vs nyloc.

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