Just wanted to drop a note to say these busbars are continuing to perform well. I'm so happy I got these. My IR's continue to be amazing and the Orion BMS continues to report that the "State of Health" of the battery is 99% which it never did before (because it saw such variation in the IRs). The pack has cycled down to 15% at least twice since my last report so it's undergone a large amount of movement (remember, I have a spring compression fixture) and everything continues to perform perfectly.
Cinergi's 28 kWh / 4 kW Solar / 10 kW inverter RV build
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Ho yea, i was pretty sure it was the way to go
Cinergi's 28 kWh / 4 kW Solar / 10 kW inverter RV build
That you did not seen any problems with rigid busbars do not prove that there isn't any. You also haven't proven that there is ..... to me, it seems logical that flexible bus bars would be the best solution ... but not if they don't meet other criteria. It seems kind of bold to come on a...
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I got the same flexible bussbar that you have and very happy with them.
Ho yea, i was pretty sure it was the way to go
Cinergi's 28 kWh / 4 kW Solar / 10 kW inverter RV build
That you did not seen any problems with rigid busbars do not prove that there isn't any. You also haven't proven that there is ..... to me, it seems logical that flexible bus bars would be the best solution ... but not if they don't meet other criteria. It seems kind of bold to come on a...
I got the same flexible bussbar that you have and very happy with them.
hehe yeah... the problem that it caused was different than everyone assumed (e.g. flexing the innards of the cell and causing damage) -- but rather causing busbar <-> cell terminal contact failure because the bus bar was sliding around underneath a properly-torqued bolt.
Hedges
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Good. I never believed that DC vs. AC somehow needed a braid, or needed a solid busbar.
Connectors. The least reliable component in electrical/electronic systems.
I've always though almost-finger-tight nuts on a single stud per connection was inviting problems. I like positive anti-rotation solutions.
Connectors. The least reliable component in electrical/electronic systems.
I've always though almost-finger-tight nuts on a single stud per connection was inviting problems. I like positive anti-rotation solutions.
Purple thread locking ? Rated for 7N.m and if you do not put much it's lower. And i would add some security paint for visual safety
Hedges
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Thread lock would keep a nut from rotating under vibration, but not resist much external force.
Equipment is normally assembled with multiple bolts/studs, and that provides anti-rotation (e.g. of a wheel on hub.)
A few electrical terminals have multiple bolts, but many, like main lugs on a breaker panel, just have one. The act of torquing screw to secure wire causes lug to turn under stud.
A few welded terminals on LiFePO4 batteries have dual studs. Some battery banks have multiple batteries in parallel, so busbars can't turn (except by multiple batteries moving.) But batteries are heavy and expand, so will try to move in mobile and fixed installations.
Cables off last battery, if tugged on, would rotate and overpower any threadlock. I think it is best they are limber (so thermal expansion doesn't move them) an secured against being moved.
As someone noted, serrated nuts could cause material to deform and settle. I've seen how aluminum cooking pots rub oxide off each other while driving. Connections and parts have to be sufficiently secure they don't move from vibration, or they will loosen. If not something like aluminum with its non-conductive oxide, spring-loaded connections could work. Welded busbars, formed to allow some compliance (the originally intended implementation for these cells) seems good.
Equipment is normally assembled with multiple bolts/studs, and that provides anti-rotation (e.g. of a wheel on hub.)
A few electrical terminals have multiple bolts, but many, like main lugs on a breaker panel, just have one. The act of torquing screw to secure wire causes lug to turn under stud.
A few welded terminals on LiFePO4 batteries have dual studs. Some battery banks have multiple batteries in parallel, so busbars can't turn (except by multiple batteries moving.) But batteries are heavy and expand, so will try to move in mobile and fixed installations.
Cables off last battery, if tugged on, would rotate and overpower any threadlock. I think it is best they are limber (so thermal expansion doesn't move them) an secured against being moved.
As someone noted, serrated nuts could cause material to deform and settle. I've seen how aluminum cooking pots rub oxide off each other while driving. Connections and parts have to be sufficiently secure they don't move from vibration, or they will loosen. If not something like aluminum with its non-conductive oxide, spring-loaded connections could work. Welded busbars, formed to allow some compliance (the originally intended implementation for these cells) seems good.
Hooo nice to know, the torque should be something like 7 or 8 N.m if i remember correctly from Eve doc, i can see those nuts been losen by successive expansion/contraction and vibrations. And losen nuts are no good .. :D
An other advantage of flexible bussbars ...
.Thread locks comes in different "strenght", if you put red on the whole thread, it will be very hard to disasemble .... like VERY..
I agree with you, one stud poorly prevent rotation, but two successive cells act like 2 studs (if cells are properly constrained) so the problem only arise for first and last conenctors which are both "alone".
I know i've used some red loctite thread lock (just a drop on each) and some security paint to visually see if one nut as gone lose.
Hedges
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Hooo nice to know, the torque should be something like 7 or 8 N.m if i remember correctly from Eve doc, i can see those nuts been losen by successive expansion/contraction and vibrations. And losen nuts are no good .. :D
An other advantage of flexible bussbars ...
If I remember correctly, people said 8 nm was the documented strength of the bond between terminal and case - lots of people mistook it for recommended tightness and stripped the thread.
The (original) cells were not engineered to have threaded connections, and some back-alley "machinist" drilled and tapped them with hand tools.
The terminals are pure aluminum, not an alloy meant for mechanical strength. Welding was the only proper connection. Now some are available with welded on terminals. But I don't know if those were a suitable alloy, and I don't think they had a plating layer to prevent corrosion, still just bare aluminum with native oxide. And people have shown that the packaging was not modified with a pocket in padding for the terminals. Stacked on top of each other, the batteries arrived with the welded-on terminals bent. Something about them now being reshipped with boxes on their sides to avoid that. The DIY market is still an afterthought.
Correct - the EVE specs do not specify the proper bolt torque. I no longer remember the proper number but it's a LOT less than the max rotational force that the specs called for.
From Eve documentation :
You are right, the limit seems to be the mechanical limit, so ... i would say 5N.m should be ok.
Hedges
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Was that torque on a thread in the aluminum?
Do you have a different figure for torque on a nut, onto a stud, threaded into the aluminum?
(I figure that would be just the shear strength of the aluminum threads. May or may not be different; could just avoid wear.)
Do you have a different figure for torque on a nut, onto a stud, threaded into the aluminum?
(I figure that would be just the shear strength of the aluminum threads. May or may not be different; could just avoid wear.)
Generally speaking, about 85% of the torque on a fastener goes to overcome friction, and the remainder goes to adding clamping force. Friction is split between friction between the nutface (or bolt face if tightening the bolt side), and thread friction.
Clamping force (pullout force), is determined by tightening torque, minus the nut face friction, and thread friction. Then you multiply by the pitch. This is a pretty long equation, so for zinc plated steel fasteners of common pitches, its often simplified to T=KFd(1-L/100). This is approximate, but its within the error factor of most torque wrenches for zinc plated steel.
For a great quality thread in soft aluminum, I would say 4NM for well lubricated threads. But given the quality of some of these tap jobs, I would say 3.5NM to be safe. A helicoil could probably go to 5NM. On my last pack, I did 3.5NM, which felt pretty close to the limit, the last 10 degrees didn't seem to be increasing in torque in the same linear fashion, which tends to make spidey senses tingle.
So the interface materials do matter, especially for dry threads. In this case, you would want to secure the stud with a threadlocker, and torque the nut itself.
At low torques, friction isn't as linear, and for materials like stainless, it can be "sticky". To make the calculations simpler, its best to lubricate the threads. A threadlocker serves as a basic lubricant at low torques (prior to cure).
I'm still in CT ... COLD ... and I'm using electric for heat as much as possible (mostly the heat pump). I'm burning 40+ kWh/day. Yeah, way past what I can produce haha. My batteries haven't sat at 100% for weeks. So I plugged in and let it hit 100% .. I had almost 200mv of drift ... which took 4 days to correct. Something tells me that, all things being equal, two batteries (instead of parallel cells) wouldn't have run into this ... I wish that were an easy thing for me to try. Not to mention double the balancing current by having two BMS'es instead of one. Oh well -- not like it caused an operational issue; the CANBUS comms properly limited my charging voltage so I didn't trigger HVD.
Still have great IR balance between all the cells with the new bus bars!
I'll be in Florida in mid December... looking forward to better sun angle!
Still have great IR balance between all the cells with the new bus bars!
I'll be in Florida in mid December... looking forward to better sun angle!
Oh, I forgot to mention that I also downsized my generator from the champion dual fuel 3400 to the honda 2200i with propane conversion kit. Runs my system just fine. I've only needed a generator once and I wanted to put a bike rack on the back of the RV instead of the cargo carrier with the generator. The 2200i easily goes into the basement storage area. propane conversion was pretty easy, too.
Hello,
I'm curious, but ... you're living in a camping car if i remember correctly, i'm pretty surprised by the energy you're burning every day ... 40kWh is a lot...
What are your high consumption appliances to have an idea ? And what kind of temperatures you got outside/inside ?
I'm kind the oposite in term of consumption, I will live this winter in a shed that is 20m2 (insulated with 15cm straw) and i'm roughfly burning ... 3kW per day (1kW just by the inverter.... and 2kW of real usage) BUT i do not heat at all (well .. some days when i'm hill or if i feel weak, i use a small ceramic 1000W heater, then consumption explode of course), today i got 5°C outside, it's 16°C inside and it's comfortable.
If you got 2x16 cells, like yuo suggested ... 2 pack of 16 and 2 BMS seems the best way to me, as you said .. twice the amp possible, possibility to remove one pack if you need to work on it (andersen connector after BMS), it's clearly more versatile. And as you mentionned each cells would be able to balance. Problem is that it need some work and if it's cold oustide it may not be the best moment .. :D
