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Discussion Starter #61
It's nothing. Glad to help:)
 

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What is a "pain scraper"? Fingers getting slow?
 

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Discussion Starter #64
It's nothing. Glad to help:)
Since the "can" was ripped at the top, I was able to measure with a caliper. The terminal depth is about .250" with an error of maybe +/- .008. Seems to me to be useless for drilling, given the softness of the material. Included is the very slight (.005" +/- "pad") on top of the terminal.

I think that these terminals were designed specifically for spot welding and that nothing else is going to work. I can't actually envision how they even did that.

I would send you the "top" in an envelope but I suspect the battery is still active and could provide some nice sparks if treated roughly.

I think that if one wanted to reconfigure the basic wiring of the pack, the best hope would probably be to cut the bus bars in the middle, bend them upward somewhat and spot weld to the bar halves. JMO.

From terminal voltage, the cell, though ripped open, is still charged. I would discharge it, completely disassemble it, and provide an autopsy if I could figure and effective means of discharging it. I don't want to short the terminals because it seems to me that that could cause massive damage.

I wonder if pouring distilled water into the open cell would bleed off the charge? I might have a resistor which could perhaps be soldered to the terminals???
 

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I think that if one wanted to reconfigure the basic wiring of the pack, the best hope would probably be to cut the bus bars in the middle, bend them upward somewhat and spot weld to the bar halves. JMO.
My 1st attempt of such on 3-12-20 .. I'd like to get the cut a bit cleaner.
85800
 

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Discussion Starter #66
Hey, great minds;)

If one could bend the bus bar halves closer to the spot well, there would be more room for spot welding.
 

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Hey, great minds;)

If one could bend the bus bar halves closer to the spot well, there would be more room for spot welding.
yup
85801

85802
 
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My 1st attempt of such on 3-12-20 .. I'd like to get the cut a bit cleaner.
View attachment 85800
Something like this:


will give you a very clean cut.

Dremel tool are great. They also have all sorts of little grinders and cutting wheels that would help you debur those tabs quickly. I prefer the carbide stuff for metal work because it lasts longer than the hardware store stuff since that stuff is for wood mostly.
 

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Since the "can" was ripped at the top, I was able to measure with a caliper. The terminal depth is about .250" with an error of maybe +/- .008. Seems to me to be useless for drilling, given the softness of the material. Included is the very slight (.005" +/- "pad") on top of the terminal.

I think that these terminals were designed specifically for spot welding and that nothing else is going to work. I can't actually envision how they even did that.

I would send you the "top" in an envelope but I suspect the battery is still active and could provide some nice sparks if treated roughly.

I think that if one wanted to reconfigure the basic wiring of the pack, the best hope would probably be to cut the bus bars in the middle, bend them upward somewhat and spot weld to the bar halves. JMO.

From terminal voltage, the cell, though ripped open, is still charged. I would discharge it, completely disassemble it, and provide an autopsy if I could figure and effective means of discharging it. I don't want to short the terminals because it seems to me that that could cause massive damage.

I wonder if pouring distilled water into the open cell would bleed off the charge? I might have a resistor which could perhaps be soldered to the terminals???
Thank you so much! Looks like I can go slightly deeper than my current tapped packs but not much deeper (again my use is for solar so no vibration concern). When I order more packs I'll have to think about the spot welding route. I played with the tabs I have lying around weeks ago and nickel strips do spot weld to them fine. Since I had enough spare tabs lying around though I tried spot welding two together directly and at least for my spot welder which usually gets up to around 600 amps I had no luck. The tabs are .5mm thick so it just didn't get hot enough. doubling up thinner pure nickel strips was fine though.

Soldering a resistor to the tabs since they are nickel plated was doable but I'm not sure about the terminals. I thought insightbuyer tried that and was unsuccessful and could only to the tabs but maybe my memory is wrong.
 

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Dremel tool are great.
yup , I have one .. and I agree .. very useful tool .. and I had considered trying it on the next one .. but .. I had some concerns about using it when I did that 1st one:

Grinding (instead of cutting) will make a bunch of airborne fine (conductive) metal dust .. I could try to cover everything else while grinding .. but still a small con.

Lost / shortened tab .. Cutting (snips) does not reduce the length of the metal tab .. but grinding will reduce / shorten the metal by a little more than the thickness of the grinding wheel .. I guessed it would loose around ~1/8" .. might not matter , but , a small con.

if I don't think of a cleaner cutting method I'm happier with .. I might try to dremel grinding eventually.
 

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Discussion Starter #71
I would use some sort of Dremel saw, not the grinding tools. The saws will produce metal debris, but not nearly as dusty. Most of the saws are thin, like 1/32, but check as you shop. You could carefully blow away the debris between steps.
 

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20 inch pounds (1.75 ft lbs) is well short of the typical 8 ft lbs that most automotive batteries recommend so I would assume tapping is a no go in a car but you guys would know better than me at what you need for all that vibration.
Yeah, that would seem pretty shaky for an automotive application. I got the cell fully discharged so, give some off time, I'll do a tear down with pictures.
 

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Yeah, that would seem pretty shaky for an automotive application. I got the cell fully discharged so, give some off time, I'll do a tear down with pictures.
Something seems to have gone wrong with a moderator edit, when I get time later today I'll try and put my original data back.
 

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Discussion Starter #74
Sorry, nothing is wrong with the system, I screwed up your data by hitting the wrong button. Gotta be more careful or they might take my buttons away. Repost what you can of it:oops:
 

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Sorry, nothing is wrong with the system, I screwed up your data by hitting the wrong button. Gotta be more careful or they might take my buttons away. Repost what you can of it:oops:
No worries it happens. Tapping data below:

I messed around with a 6061 aluminum bar and the fit pack terminals yesterday. I'm using 10-24 threaded rods so for a 1/4 inch terminal that's a max of 6 threads if perfect (so most times you have 4 or 5 threads to torque against). On the practice bar the highest torque before the underlying terminal stripped was 26 inch pounds (just over 2 ft lbs) and was using steel threaded rods. Whether it was 6 threads (.25" deep), 5 threads, or 4 threads (.16" deep) had very little difference on stripping torque value so it's best to not worry about puncturing through the battery terminals and give yourself a little leeway and go a bit more shallow than .25".

When I moved over to the fit packs I could feel on my beam torque wrench that ever so slightly the terminals seemed very slightly softer than the 6061 practice bar so the terminal is likely 6101 highly conductive aluminum. As far as torque though it had little impact. Since even with steel the torque values aren't very high, I switched over to aluminum rods so that corrosion isn't a concern and so that if you ever do make a mistake its the rod that strips and not the battery terminal. With an aluminum rod on the battery 20 inch pounds of torque is the max before stripping the rod (1.75 ft lbs). For a stationary application the difference is so slight vs steel that I would recommend using aluminum rods and being ok with 4 threads of grab with using nylock nuts.

In an automotive application though 1.75 ft lbs of torque is shaky with all the vibration in the car. Tapping is likely not recommended for the car, only for something stationary like solar. You could probably increase the stripping torque a bit by using 10-32 threads or going larger like 12-24 but based on everything I saw it's not going to get you close to the 8 ft lbs of torque most automotive batteries recommend. The weak link is the soft battery terminal and since the terminal is 7mm long x 14mm wide you can't go anywhere near large enough to get close to 8 ft lbs. Leaving the tabs in place and either spot welding nickel strips to them or bolting to the tabs is likely the correct course of action if you are rearranging the pack in a car like for the starting battery Jime did.
 

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Discussion Starter #76
Ok, just a quick summary update on performance. The 5 cell LTO has been installed for about a month now and is working quite well. With the DVCT wire cut, the battery is operating at about 13.85-14V when the car is running. Since the operating point is right on the steep part of the charge curve, then the voltage changes fairly rapidly under operation, i.e. at around 2.8V/cell, it only takes a small amount of current to make a big change in battery voltage. Again, it doesn't take much parasitic load from two days of parking to drag the battery down to 13.2-13.4V, or the much more linear part of the charge curve.

I have no idea if I'm shortening battery life by operating the cells at this voltage point. I do have the 6 cell version on the bench, but have not tested that yet. I think I would want to find a way to somehow approximate the battery current before installing the 6 cell. With 6 cells, the operating point will be well within the linear part of the charge curve and the low internal resistance cells can adsorb considerable current over long periods, relative to what the lead acid battery does.
 
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Hey Jime, I always intended to do this and actually cut half my pack without much issues to see if it was possible. Why I never went through with it was at the time I didn't know you can adjust so easily the cars DC/DC converter. At that time I didn't like the Insights charging voltage as it was either too low or too high. Now that I see you can easily adjust this voltage it makes sense to do this modification.

What I am going to do is use 6 cells, and I think the 13.85 voltage is reasonable and actually may be a better voltage for long term use.

What I am going to add is a small DC/DC converter, 200 volts to 15 volt (adjustable) DC/DC converter that I will hook up to my 12 volt battery with a diode. This will be able to always keep the battery pack at 13.50 volts with the car on or off and I will not have to worry about parasitic load and dead batteries. It will also act as a backup just in case anything happens to my battery I can run the car off this smaller DC/DC converter.

Basically the car will charge the pack to 14 volts during use, but then my DC/DC converter will only kick in if the car LTO drops below 13.50 volts, so it will hardly be used.
 

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What do you guys think of Hooking up a dedicated DC/DC converter to the battery, with a diode, as a backup protection?

Something like a meanwell HRP-100 series.

Data Sheet:

Its light weight, only 1 lbs, and small enough to find a spot in the IMA battery compartment.
Has constant current limiting.
Adjustable voltage output
DC voltage input from 120 volts to 370 volts DC.
Has only a .5w no load power consumption, this draws very little current when sitting hooked up to your LTO pack, nothing to worry about unless you are letting the car sit for a couple of months.

You could always put a switch on it to turn it on/off when needed. You would never have to worry about a dead or low battery ever again.
 

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I'm going to have a 7 amp DC/DC converter connected directly from my 200 volt LTO pack to my 12 volt pack that will be replaced with a 6 cell LTO pack. This is just as a backup / emergency DC/DC converter to only keep the 12 volt charged when the car is off.

With just a quick look at the diode and power supply, do you see any obvious issues with using this setup?

Meanwell HRP-100-15

15Amp 200 Volt rectifier

Thanks
I don't see any obvious serious issues...... However.

You def need a switch with a big warning light in the hv input to turn the dc-dc on/off properly.

I killed my $8000 solar van lithium pack twelve years ago by leaving a converter turned on for a week. A very expensive lesson.

If you don't have a switch etc and are relying on the fact the 12V is charged for the converter to go into shutdown or low power mode that's very risky IMO. Ideally you should have an automatic low pack voltage cutoff as well.

If a cell in your 12V fails or you leave the car lights on etc the converter will simply burn up the energy in your main LTO pack trying to feed the 12V and possibly kill it..

It's also dodgy if you disconnect the 12v battery, then depending on how you connect the dc-dc the car 12v system might still be powered by your dc-dc being active.

Finally

Assuming the rectifier diode is on the PSU output you don't need a 200V part or anything fancy.

A 50V 10A rating is enough.
 

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I've knocked something up today for testing later.

Assembled basic 4 x20ah A123 cells into a pack for in car testing.

Also fitted with little voltage monitor for checking balance.
The monitor has a 2.7V audible alarm as well.

Amazingly these cells unused and untouched for over 5 years still had almost identical terminal voltages of 3.3V

I riveted the tabs together today as soldering dissimilar metals was incredibly difficult the last time I tried even using super deadly flux and a 100w iron.

 
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