michaelplogue
10 kW
I'd be more worried about trying to pry a bad cell out that had been glued a bit too well....
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PSI -- LiFePo4 -- Testing.. 1 ... 2... Testing..
- Thread starter Ypedal
- Start date
AndyH
10 kW
michaelplogue said:
Expanding foam is sticky stuff... Maybe give the cells a loose wrap of plastic food wrap before foaming them.
What would put the least amount of stress on the cell terminals over time - isolating the plastic end plates from the cell, or locking the entire assembly into one stuck mass?
Ypedal
100 TW
Heh... oh the Great Stuff...... what a mess i made. but i learned something !! :wink:
The smooth surface of the shrink wrap sticks just enough to keep the cells from spinning around but will easily peel off cleanly.
When i bolted the side plates on the cells.. i forgot to add the 10 gauge power wires so i popped off one side, and drilled holes to access the centre of the cells.. bolted the plastic platet back on.. and shook the foam can..
Wwwooooooshshhh.. squirt squirt.. man.. this stuff expands like mad.. a dab will do you.. and i went overboard...
So much so that the foam oozed out the ends and filled in the gaps between the cells and copper straps.. filling the ends.. at first i thought " Cool !! "... then i thought.. " Oh crap.. i wonder if this stuff is conductive when it's wet :lol: "...
Well.. the cells never got hot .. or even warm.. so no major shorts.. I let all that settle dry up.. then ... crap.... no power at the power wires...
The foam pushed the side plates and crept in between the copper straps and battery bolts.. I had to rip the foam away from the ends and remove the plastic ends to clean out the foam...grrrr.. it looked so nice and solid..
Oh well.. glad i only did this on Pack 1 !!
The smooth surface of the shrink wrap sticks just enough to keep the cells from spinning around but will easily peel off cleanly.
When i bolted the side plates on the cells.. i forgot to add the 10 gauge power wires so i popped off one side, and drilled holes to access the centre of the cells.. bolted the plastic platet back on.. and shook the foam can..
Wwwooooooshshhh.. squirt squirt.. man.. this stuff expands like mad.. a dab will do you.. and i went overboard...
So much so that the foam oozed out the ends and filled in the gaps between the cells and copper straps.. filling the ends.. at first i thought " Cool !! "... then i thought.. " Oh crap.. i wonder if this stuff is conductive when it's wet :lol: "...
Well.. the cells never got hot .. or even warm.. so no major shorts.. I let all that settle dry up.. then ... crap.... no power at the power wires...
The foam pushed the side plates and crept in between the copper straps and battery bolts.. I had to rip the foam away from the ends and remove the plastic ends to clean out the foam...grrrr.. it looked so nice and solid..
Oh well.. glad i only did this on Pack 1 !!
michaelplogue
10 kW
Ypedal
100 TW
Just got back from the post office !!
12 x Soneil 24v 5 amp chargers ! ( Using 2 of these to charge my chopper will be AWSOME !!! instead of my current 16 chargers for a 2 amp charge. will still be handy for ballancing tho !.)
12 x Soneil 24v 5 amp chargers ! ( Using 2 of these to charge my chopper will be AWSOME !!! instead of my current 16 chargers for a 2 amp charge. will still be handy for ballancing tho !.)
Ypedal
100 TW
Plastic box, with fan..
I kinda like the metal units but they are heavier and fall harder.. Draining the packs now to test the chargers tonight !!
I kinda like the metal units but they are heavier and fall harder.. Draining the packs now to test the chargers tonight !!
Ypedal
100 TW
Red 10 gauge wires installed !
Ypedal
100 TW
Just the right amount of ooze between the cells..
Ypedal
100 TW
Before i had to rip it out.. it was all white, and tight.
Still. the foam does what it does and supports the cells..
If the pack is assembled in a way the cells can twist in any way, the threaded nuts will loosen on one end or the other, it's very important that the cells be secured , one way or another.
The 2nd pack i'm considering hot glue or silicone, but i don't like the idea of the heat generated by the hot glue gun on the cell walls, and it can be hard to seperate the cells.. silicone is another option, hmmm..
Still. the foam does what it does and supports the cells..
If the pack is assembled in a way the cells can twist in any way, the threaded nuts will loosen on one end or the other, it's very important that the cells be secured , one way or another.
The 2nd pack i'm considering hot glue or silicone, but i don't like the idea of the heat generated by the hot glue gun on the cell walls, and it can be hard to seperate the cells.. silicone is another option, hmmm..
johnrobholmes
10 MW
I would vote silicon.
marty
10 MW
I say hot melt glue. Easy to use and dries fast.
Ypedal
100 TW
Testing the Soneil chargers, yeah baby.. yeah !!!
Starts at 4.8 amps, but as it warms up, tappers down to 4.6, all the way up to exactly 29.0v then the current drops down gradually to 0.3 amps then the light goes green.. and the voltage drops to 27.7v as the light stays green and the amps trickle to keep the voltage to 27.7v .. All good !
The internal fan is nice and quiet, hottest spot on the charger is near the fan exit, up to 45 celcius, but nothing like the cheaper chinese 2 amp units i've tested.. even the voltphreaks newest batch will get into the 50 + celcius .. :lol:
Starts at 4.8 amps, but as it warms up, tappers down to 4.6, all the way up to exactly 29.0v then the current drops down gradually to 0.3 amps then the light goes green.. and the voltage drops to 27.7v as the light stays green and the amps trickle to keep the voltage to 27.7v .. All good !
The internal fan is nice and quiet, hottest spot on the charger is near the fan exit, up to 45 celcius, but nothing like the cheaper chinese 2 amp units i've tested.. even the voltphreaks newest batch will get into the 50 + celcius .. :lol:
AndyH
10 kW
That came out pretty good! I had visions of globs hanging out all over the place...sorta the urethane version of Big Momma. :lol:
Takemehome
1 kW
Ypedal said:
What about silicone on the nuts and prevent loosening and accidental short circuit at the same time ?
recumbent
100 kW
What about glueing the cells body together first, then attach the leads. This way vibration won't loosen, or stress the connections. And omit the plastic end pieces altogether, then shink-wrap it. Of course this is easy for me to say because I've never seen the cells in person, so to speak.
Ypedal
100 TW
After some thought, the cells get subjected to more heat during the shrink wrap process than the hot glue will do to them, so out with the hot glue gun !! ( ps: Don't use hot glue on nicad packs, they get hot enough during charge/discharge to make the glue runny.. horrible mess )
The pack feels solid, you can tell when you pick it up that it's one solid mass.
Now..... this means.. Tomorrow .. Road Test !!!!
The pack feels solid, you can tell when you pick it up that it's one solid mass.
Now..... this means.. Tomorrow .. Road Test !!!!
Ypedal
100 TW
GGoodrum said:
That sentence has been engraved in my brain since the day i read it.. being ever so careful not to overdo it...
I've been wrenching for many years, plenty of experience turning bolts on antique Honda trikes, i've developped a pretty good " Clicker Elbow " . Looking at the diameter of the stud, i was confident i was not going to snap any with the force i was applying...
Assembled all 16 cells, a few times already, and before leaving for today's 1st ride i re-checked all the nuts and was on the 15th stud when disaster happened......
The darn things are HOLLOW !!!!
GGoodrum
1 MW
Oh, bummer.
I was able to fix the one I had, because there is actually a 3mm threaded rod that I think is used to mount the stud. I cut back part of the remaining stud, exposing a few mm of the 3mm portion. I then screwed on the borken off part, threaded a nut over the joint, and then epoxied it in place.Seemed to work fine.
I was able to fix the one I had, because there is actually a 3mm threaded rod that I think is used to mount the stud. I cut back part of the remaining stud, exposing a few mm of the 3mm portion. I then screwed on the borken off part, threaded a nut over the joint, and then epoxied it in place.Seemed to work fine.
Ypedal
100 TW
Ohh.. good thinking !! ( better than what i was about to do.. :wink: )
One interesting note to this, once it snapped off, i got the ever familiar smell of Solvent !
When i first got my LiMn and 12ah green square LiFE cells, i kept getting a wiff of strong solvent odor, i figured it had to be the heat shrink rubber smell, but in fact it's the cells venting solvents !
The PSI cells do not smell at all until you pull a bonehead act like i just did, all the other cells except the " Ping " style foil pouches have this smell at all times, specially strong if the packs are boxed air tight for a while..
I have no idea what this means for the other cells that vent like this, if you can smell it, it's evaporating, what happens once they dry up ? or how long can this take ? do you slow down the process if the cells are sealed ? all questions i'll know in time.
--
RIDE #1 !!!
The plastic ends on the packs hold the copper strips tight against the brass nut on the cells, so i ventured out for a ride after taping the whole pack for added pressure and needing to go for a ride really bad...
Loaded the backpack, grabbed the BMX ( rear wheel 5304 in a 20", with a modded controller using 4110 fets and a max amp set to about 50 amps !! )
On a 35 amp controller, my 48v 24ah Duct Tape pack just crumbles down to lvc within seconds..
On a 35 amp controller, my 12ah square cells maintain 48v under load, and at the 5ah mark start to dip down to 45v under load, but it all works pretty well.. the cells stay cool to barely warm...
On the 50 amp Controller, the 12ah square cells get pretty hot, on hard acceleration will dip down to 45v fresh off the charger, inside the backpack these cells get too hot for comfort, in a metal box mounted to flowing air inside the frame of the chopper however they would manage.... but be at their max..
The PSI cells on the bmx are better performers, absolutley, fresh off the charger, 55 amps on the CA meter, front wheel in the air and smile on my face.. i went for a 25 km rip around town.. 48v 10ah of PSI cells are lighter than the 12ah 48v square cells, every lb counts when you have them on your back..
Q: How did they do ?
A: Great !
I need to recalibrate this CA meter, i know i'm close, but i'll report back once i double check the numbers with an inline CA ..
Used 7 ah and all cells at rest read 3.248v to 3.251v.. pack voltage on level ground holding 48v + .. dipping down to 45v at 50+ amps at the end of the ride..
So far so good !!!!
One interesting note to this, once it snapped off, i got the ever familiar smell of Solvent !
When i first got my LiMn and 12ah green square LiFE cells, i kept getting a wiff of strong solvent odor, i figured it had to be the heat shrink rubber smell, but in fact it's the cells venting solvents !
The PSI cells do not smell at all until you pull a bonehead act like i just did, all the other cells except the " Ping " style foil pouches have this smell at all times, specially strong if the packs are boxed air tight for a while..
I have no idea what this means for the other cells that vent like this, if you can smell it, it's evaporating, what happens once they dry up ? or how long can this take ? do you slow down the process if the cells are sealed ? all questions i'll know in time.
--
RIDE #1 !!!
The plastic ends on the packs hold the copper strips tight against the brass nut on the cells, so i ventured out for a ride after taping the whole pack for added pressure and needing to go for a ride really bad...
Loaded the backpack, grabbed the BMX ( rear wheel 5304 in a 20", with a modded controller using 4110 fets and a max amp set to about 50 amps !! )
On a 35 amp controller, my 48v 24ah Duct Tape pack just crumbles down to lvc within seconds..
On a 35 amp controller, my 12ah square cells maintain 48v under load, and at the 5ah mark start to dip down to 45v under load, but it all works pretty well.. the cells stay cool to barely warm...
On the 50 amp Controller, the 12ah square cells get pretty hot, on hard acceleration will dip down to 45v fresh off the charger, inside the backpack these cells get too hot for comfort, in a metal box mounted to flowing air inside the frame of the chopper however they would manage.... but be at their max..
The PSI cells on the bmx are better performers, absolutley, fresh off the charger, 55 amps on the CA meter, front wheel in the air and smile on my face.. i went for a 25 km rip around town.. 48v 10ah of PSI cells are lighter than the 12ah 48v square cells, every lb counts when you have them on your back..
Q: How did they do ?
A: Great !
I need to recalibrate this CA meter, i know i'm close, but i'll report back once i double check the numbers with an inline CA ..
Used 7 ah and all cells at rest read 3.248v to 3.251v.. pack voltage on level ground holding 48v + .. dipping down to 45v at 50+ amps at the end of the ride..
So far so good !!!!
dnmun
1 PW
bummer, if it is hollow, maybe cut threads on the inside and use a thread cut from a screw inside as a dowel, use the anticorrosive gel if you use a copper thread.
i disagree with don, i thought the urethane was just too much volume and i see no reason not to use it, i would vote for minimal urethane, just enough to cover about a square inch on the end of the cylindrical surface.
i am still thinking that the reason the headway 5P pack was failing was because large mechanical stresses are applied to the cell caps because everything was so stiff connecting the end caps together, any twist in pack is applied to the cell caps. so i would stick with flexible straps, soft copper and no need for super thick connections since copper is very conductive so even thin copper conducts major current, and less stress can be exerted through the sheet than stiff connectors, same is true with the plastic end plates you have screwed everything to here. i would worry it can apply the same stress directly to the end cap.
i would vote suspend the cells from the outside cylinder ends from the plastic by adhesion through the urethane foam dollop, keeping the end cap open as much as possible, and where the threaded portion goes through the plastic, have a soft collar or empty space around the shaft so no vibration from the plastic goes into the cap, and then connect with lightest of copper strip with a flex hinge ridge stamped in them halfway, then 2 nuts, or instead of tightening nuts on the exposed aluminum thread stud, using a threaded coupling of brass, using antioxidation gel, screwed down the entire length of the stud on the end of the cell. the outer end of this coupling will then have female threads exposed to the outside end, and when you thread a screw down the barrel of the coupling, it will lock the coupling onto the stud when the screw drives against the end of the stud inside the coupling. imagine this screw has a nut on it which captures the connection strap between the head of the screw and the nut, loosely snugged up under the strap so it holds it in place while you tighten the screw into the coupling to lock it in place, then hold the head of the screw and tighten the nut under the strap squeezing it up against the screw head and not down onto the end of the coupling. unlimited number of removals without inducing metal failure in the aluminum threaded stud.
since the threads would separate the connection from the cell cap/stud then you could most likely solder the strap onto the screw cap very quickly and use a good heatsink close to the cell body. maybe even wrap the base of the coupling with loose cloth or paper towel to trap cooling water for the heatsink while soldering, hot and fast on the end, just a dollop sloped over the edge of the screw head onto the connector strap, no need for a huge flow of solder, imo.
my ideas are all meant to hang the cell from the cylindrical body, rather than the stud, but the suspension would be through the plastic end plates, not the body/body contact. and at the same time eliminate any mechanical forces applied to the end cap.
if the adhesion through the foam is just around the ends it will also make it easier to get the cell out later since there is no adhesion deeper down along the cell to cut out later, so one cell could be plucked right out of the middle of the pack, easily almost. the holes you drilled in the plastic for the foam injection would allow a burnishing,or hooked, cutting type tool to reach through to scrape away the foam adhering the end plate to the cells. if you later need to replace the cell, just use a hole saw to cut open the plastic end plate, from just one end and pluck the cell out by itself, to keep it simple. and then you don't lose too much structural strength during the repair/replacement. you could glue the plug back in place when the new cell went in, using the same foam as the holds the cell in place.
BOL, also i'm sorry the halifax herald never talked to you and justin for the last leg of the trip back then when i emailed you warning that they might. i wasted 2 days of emailing their news desk, all they could think to ask was "when will he arrive?" what a way to run a newspaper. it's only news if you can get it on a schedule. what a shame.
i think the solvent is thionyl chloride, which transports the lithium ions in solution. anybody know?
i disagree with don, i thought the urethane was just too much volume and i see no reason not to use it, i would vote for minimal urethane, just enough to cover about a square inch on the end of the cylindrical surface.
i am still thinking that the reason the headway 5P pack was failing was because large mechanical stresses are applied to the cell caps because everything was so stiff connecting the end caps together, any twist in pack is applied to the cell caps. so i would stick with flexible straps, soft copper and no need for super thick connections since copper is very conductive so even thin copper conducts major current, and less stress can be exerted through the sheet than stiff connectors, same is true with the plastic end plates you have screwed everything to here. i would worry it can apply the same stress directly to the end cap.
i would vote suspend the cells from the outside cylinder ends from the plastic by adhesion through the urethane foam dollop, keeping the end cap open as much as possible, and where the threaded portion goes through the plastic, have a soft collar or empty space around the shaft so no vibration from the plastic goes into the cap, and then connect with lightest of copper strip with a flex hinge ridge stamped in them halfway, then 2 nuts, or instead of tightening nuts on the exposed aluminum thread stud, using a threaded coupling of brass, using antioxidation gel, screwed down the entire length of the stud on the end of the cell. the outer end of this coupling will then have female threads exposed to the outside end, and when you thread a screw down the barrel of the coupling, it will lock the coupling onto the stud when the screw drives against the end of the stud inside the coupling. imagine this screw has a nut on it which captures the connection strap between the head of the screw and the nut, loosely snugged up under the strap so it holds it in place while you tighten the screw into the coupling to lock it in place, then hold the head of the screw and tighten the nut under the strap squeezing it up against the screw head and not down onto the end of the coupling. unlimited number of removals without inducing metal failure in the aluminum threaded stud.
since the threads would separate the connection from the cell cap/stud then you could most likely solder the strap onto the screw cap very quickly and use a good heatsink close to the cell body. maybe even wrap the base of the coupling with loose cloth or paper towel to trap cooling water for the heatsink while soldering, hot and fast on the end, just a dollop sloped over the edge of the screw head onto the connector strap, no need for a huge flow of solder, imo.
my ideas are all meant to hang the cell from the cylindrical body, rather than the stud, but the suspension would be through the plastic end plates, not the body/body contact. and at the same time eliminate any mechanical forces applied to the end cap.
if the adhesion through the foam is just around the ends it will also make it easier to get the cell out later since there is no adhesion deeper down along the cell to cut out later, so one cell could be plucked right out of the middle of the pack, easily almost. the holes you drilled in the plastic for the foam injection would allow a burnishing,or hooked, cutting type tool to reach through to scrape away the foam adhering the end plate to the cells. if you later need to replace the cell, just use a hole saw to cut open the plastic end plate, from just one end and pluck the cell out by itself, to keep it simple. and then you don't lose too much structural strength during the repair/replacement. you could glue the plug back in place when the new cell went in, using the same foam as the holds the cell in place.
BOL, also i'm sorry the halifax herald never talked to you and justin for the last leg of the trip back then when i emailed you warning that they might. i wasted 2 days of emailing their news desk, all they could think to ask was "when will he arrive?" what a way to run a newspaper. it's only news if you can get it on a schedule. what a shame.
i think the solvent is thionyl chloride, which transports the lithium ions in solution. anybody know?
Ypedal
100 TW
Thanks for the thoughts.. ! I welcome any and all suggestions ..
Agreed on supporting the pack by the cell ends, i should receive the molded plastic end caps from PSI in a few weeks, this will be a big part of the puzzle solved..
Winter is just around the corner here, today was about the nicest day of the year, leaves are falling, forest is just awsome to ride around in, leaves make for a slippery trail !!
Recharged with CA inline, packs took 8.5ah in.. ( the CA on the BMX said 7.6ah used ), i need to lower the shunt resistance value on the bmx's CA a bit..
I considered building a star shaped pattern and then fill them with silicone to create spacers, would be a fun project but the Hot Glue works like a charm so far.. I tested one strip with silicone but takes too long to dry, and is too soft even once cured.
All good fun ! 8)
About Justin, i aproached a rep from the local Times and Transcript at one point abuot a week before he got here, started to explain the brief details and i got the cold " go away and quit bothering me " look..unreal. We got some Youtube footage and pictures to keep the memory alive and it's all good in the end, cuz this is just the beginning ! :wink:
Agreed on supporting the pack by the cell ends, i should receive the molded plastic end caps from PSI in a few weeks, this will be a big part of the puzzle solved..
Winter is just around the corner here, today was about the nicest day of the year, leaves are falling, forest is just awsome to ride around in, leaves make for a slippery trail !!
Recharged with CA inline, packs took 8.5ah in.. ( the CA on the BMX said 7.6ah used ), i need to lower the shunt resistance value on the bmx's CA a bit..
I considered building a star shaped pattern and then fill them with silicone to create spacers, would be a fun project but the Hot Glue works like a charm so far.. I tested one strip with silicone but takes too long to dry, and is too soft even once cured.
All good fun ! 8)
About Justin, i aproached a rep from the local Times and Transcript at one point abuot a week before he got here, started to explain the brief details and i got the cold " go away and quit bothering me " look..unreal. We got some Youtube footage and pictures to keep the memory alive and it's all good in the end, cuz this is just the beginning ! :wink:
MitchJi
10 MW
Ypedal said:
Hi Gaston,
I'd be concerned that the cells would rotate and the studs would not.
I have two questions. I think the nominal voltage is 3.3V and the cut off is 2.1V. So a 12s pack would start off at about 39v but at the cutoff voltage the pack would be 24V. Thats a huge drop! What percent of the pack is discharged at a more reasonable voltage, something like 2.5V or better yet 2.8V?
Also this isn't a PSI related question but what is the significance of the "internal resistance" specification?
Thanks!
Mitch
Ypedal
100 TW
Hello Mitch !! ( ps : I received the NuVinci !! THANK YOU !!! )
The internal resistance is directly related to how many amps the cell can provide before the voltage sags under load, the more the resistance, the bigger the sag, and the more heat it creates when drained quickly...
The cell rotating is the reason for glueing them all together into a solid mass.. ! Along with preventing them from bumping into each other from vibrations. When you hit a bump, you want the entire " Pack " to move as one, if some of the cells move and others don't, it will lead to premature problems !!
The internal resistance is directly related to how many amps the cell can provide before the voltage sags under load, the more the resistance, the bigger the sag, and the more heat it creates when drained quickly...
The cell rotating is the reason for glueing them all together into a solid mass.. ! Along with preventing them from bumping into each other from vibrations. When you hit a bump, you want the entire " Pack " to move as one, if some of the cells move and others don't, it will lead to premature problems !!
ZapPat
10 kW
I don't want to pick apart your post, Ypedal, but just so that people don't get confused about internal resistance I wanted to clarify a bit. I think it's just a translation thing, but the actual voltage sag you get is directly proportinal to the batteries internal resistance and is not an ON/OFF thing (just as you explained very well after the bold/italic part: "the more the resistance, the bigger the sag, and the more heat it creates when drained quickly").Ypedal said:
So Ypedal's nice BMI cells will display voltage sag half as much as the newest headway cells, or about a quarter of my ping battery. Thus, my Ping battery's voltage sag is just over 1V per 10A, or just over 110milli-ohms resistance for a 16-cell pack.
Also, internal resistance changes as the battery discharges, and better quality cells will keep a lower internal resistance for a longer time (ie down to 90-95%), letting you get better power almost right down to the end of discharge.
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