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can you please post the .txt file for BCMI_L144_H180_T25_S75_280620
Do you mean you would like the source code?
If so e-mail me.

The Hex code is a few posts back..
 

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I just updated my BCM Interceptor with the new .hex file.

If I just jumper J3 Pins 1, 2, and 4 for now (and maybe do the switches later) it will allow both assist and regen except if I hit 180V or 144V, so it's pretty-much going to be safe to drive w/o any manual intervention on the part of the driver? It'd be nice to not need to mess with the SoC on OBDIIC&C all the time to manage the IMA behaviour.
 

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it will allow both assist and regen except if I hit 180V or 144V, so it's pretty-much going to be safe to drive w/o any manual intervention on the part of the driver?
That is of course assuming all your cells are very well balanced.
 

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That is of course assuming all your cells are very well balanced.
Is this not usually the case? About 2 months ago, which was after 6 months of near-daily use of the LTO setup in my 2000 Insight, I checked all 72 cells and the highest cell voltage was only about 0.02 volts above the lowest cell voltage.

I've of course read Atheos' story about how he had a cell die on him, but I've not heard much else about these cells going bad.
 

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I think they do keep well in balance, but there will always be exceptions. It's a minor risk factor we accept.

Using the LTO cell level BMS is the answer for complete peace of mind.
 

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I recently read that lithium batteries should be grid-charged using a constant voltage (CV) supply, not the constant current (CC) supply since grid charges were designed for NiMH batteries. Can someone comment please. Also can a single two-pack of LTO's (24-cells) be grid-charged with the normal CC charges set to 180V? Thanks
 

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I recently read that lithium batteries should be grid-charged using a constant voltage (CV) supply, not the constant current (CC) supply since grid charges were designed for NiMH batteries. Can someone comment please. Also can a single two-pack of LTO's (24-cells) be grid-charged with the normal CC charges set to 180V? Thanks
Lithium batteries are usually charged with a combination. Typically it's constant current charged up to a threshold and then switched to constant voltage. Generally speaking this is so you actually store the desired energy in the battery because it tends to "rebound" like a rubber band a bit. If your desired voltage was 180V and you CC charged it to 180V and let it sit for a day when you came back to it the next day you'd find the voltage of the batteries would be under 180V. Same is true for discharge, many EV owners especially in the beginning when range was limited would run out of juice not far from home (because they screwed up) and instead of calling a tow truck come back the next day and it had that little bit of juice to get home. Basically it rebounded on the downswing as well. To actually get the batteries up to the voltage you want you generally CC charge to the threshold and then CV charge until the amps drops to almost nothing. Basically, it holds the voltage steady through that rebound phase so that when you take it off the charger it'll stay at that voltage.

24 cells are fully charged at 2.7V per cell (or 64.8V). Did you mean 3-24 cell packs? That would be fully charged at 194.4V and 180V would be 2.5V per cell. If you have 72 cells you could CC charge them to 180V, 184V, or whatever under 194.4V and with a little trial and error reading the voltage if you didn't want to spend on a CV or CCCV charger you could likely get used to what the rebound swing is on the cells to make it come out to 180V when you drive the car. Likewise you could just CC charge to 180V and just deal with the little less juice when you drive since it'll have come down a bit by then. CC chargers usually shut off with dV/dt though so you'd need to know the full specs of your charger to know if dV/dt hits the threshold at the right voltage.

There are all types of grid chargers whether it's CC, CV, or CCCV depends on which one it is.
 

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<EDITED>

By my text references, CC followed by CV(CC/CV) if the cells are to be fully charged to their maximum voltage. Depending on the program in the charger, the CV phase may only be the last few tenths of a volt. The PL8 charger/discharger LTO profile switches to CV right at the end, and starts cutting back on current until the cells are at the specified maximum voltage.

CC should be fine if the shutoff is WELL short of the specified maximum and minimums for the cells. Without BMS, it is wise to stay short of the pack minimums and maximums anyway. If you try to charge a non-BMS string of cells to full spec then some of the cells will be overcharged since balance is never perfect, particularly in used cells.

When an LTO cell is full, additional current will cause the voltage to rise very quickly, and this is the reason for the CV deminishing current phase.
 

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Also, if you are charging with a typical CC grid charger, ok if away from the cell limits, you need to watch the individual cells very carefully near the cell limits. I suppose Peter's gauge would do that within accuracy needed. Same true of discharging with a manual load.

It takes a very long time to charge at the typical 330-350 mA of the typical grid charger. The first guy to build, Insightbuyer, built a special charger, which is covered early in his thread. Most of the operating range is pretty linear, so one can usually calculate the amount of time needed to approach the limits.
 

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Great explanations. I was asking two questions, the second of which was: can a single two-pack of LTO's (24-cells) be grid-charged with the normal CC charger at 180V? I know the target voltage is 64.8V; will the ~180V cc grid charger just get that 2-pack, 24-cell voltage to its goal that much quicker?
 

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I assume you are saying that the open circuit voltage of the charger is 180V. If that is the case and it is a true CC charger, then the voltage will fall immediately when it is loaded with the battery. Is this a common Insight grid charger? What is brand?

You will recall that many of us use the common Insight CC chargers for cycling of the OEM batteries. In that case, their output voltage can be quite low when the OEM battery is empty.

BUT, you do not want to charge 24 cells in series to 64.8V:eek: That is 2.7V/cell, the full cell spec, and would be the maximum IF your had perfect cell balance between the cells OR if you had a BMS controlling the charger. Neither is the case. The non-BMS operating range for these packs has been discussed many times and the consensus has been that about 2.5-2.0V/cell is the most judicious range, without benefit of BMS. That would give you a 24 cell maximum charge of 60V. Nothing above that is likely safe for the packs in a non-BMS mode.

My edited #849 and my #850 above BOTH say, "Stay away from the cell limits."
 

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I assume you are saying that the open circuit voltage of the charger is 180V. If that is the case and it is a true CC charger, then the voltage will fall immediately when it is loaded with the battery. Is this a common Insight grid charger? What is brand?

You will recall that many of us use the common Insight CC chargers for cycling of the OEM batteries. In that case, their output voltage can be quite low when the OEM battery is empty.

BUT, you do not want to charge 24 cells in series to 64.8V:eek: That is 2.7V/cell, the full cell spec, and would be the maximum IF your had perfect cell balance between the cells OR if you had a BMS controlling the charger. Neither is the case. The non-BMS operating range for these packs has been discussed many times and the consensus has been that about 2.5-2.0V is the most judicious range, without benefit of BMS. That would give you a 24 cell maximum charge of 60V. Nothing above that is likely safe for the packs in a non-BMS mode.
As Jime has said you don't want to charge up to 2.7V/cell he recommends 2.5V/cell (60V for 1 24 pack or 180V for 3 24-packs) because there is no BMS in play. Most true CC chargers either use dV/dt to shutoff or are just purely time based. To know if your charger would work and what it would do depends on what make/model it is (how many amps it does, what it shuts off at, what it's voltage range is, etc.).
 

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Thanks @jime but I think you removed useful info to me and others when you re-wrote. OK.
So I'm currently charging my pack with the ~180V charger that uses a Mean Well 350 ma CC supply that I installed into Peter's Simple Cycler charger. All cells are rising equally but still keeping the 50mV average difference on Blocks 0 & 1. I'm used to charging my NiMH cells for a bunch of hours, then everything is balanced. I'm a little afraid of trying to balance this pack with the 50 mV voltage differential since I don't know if that difference will disappear (when / if balanced). Just curious, would a 65V CV charger balance a two-pack, 24 cell pack (nominal 2.7VX24=64.8) without a BMS? What is the best way to balance a complete 72 cell LTO pack? My max PS voltage is 180V - just charge while monitoring and hopefully the low cells will charge up to the others? Doesn't sound like the best idea.
 

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No it isn't OK. I added the word "well" to say "well short of maximum" which is precisely what I meant., as an improved wording. The short and easy message is, "Don't charge a 24 cell pack above 60V until you somehow know better." Enough said??

You aren't going to balance out the trivial 50mV by doing the same thing with LTO that you do with the OEM NiMH. I'm not going through a long discussion, but it just ain't going to happen - that's not the way it works, they are different chemistries.

If you insist on balancing the two halves of the pack by charging at the terminals, then you need to charge as you are doing until the highest half-pack is at 30V. Then remove the bus bar between the two halves, replace the terminal bolts, and charge the low half VERY slightly, let them rest a hour and then repeat if necessary. Isn't the way I do it with PL8, but I think that "might" work.

You are doing a lot of unnecessary work in a haphazard way without fully understanding what your are doing. If you succeed in getting these two halves to +/- 20 mv or so, what are you going to do about the other two packs?? They will then probably be at a different voltage still.

I'm done for the day. I've written 3 detailed and thought out longish messages this afternoon, and I have better things to do.
 

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No it isn't OK. I added the word "well" to say "well short of maximum" which is precisely what I meant., as an improved wording. The short and easy message is, "Don't charge a 24 cell pack above 60V until you somehow know better." Enough said??
For sure, basically if you don't have a BMS or something actively balancing the cells in series you should not get close to 2.7V (stay at 2.5V as "fully charged). I think the confusion came into play when talking about the power supply being 180V before we started talking about Constant current chargers. 180V is 2.5V per cell on 72 cells which for a 24 pack is 60V which is your recommendation not to exceed without balancing.

The initial question seemed to be around speed and not balancing but is now clearly both. If you need speed and balancing a PL8V2 or a charger capable of delivering more amps WITH a BMS in play is required. If you drop one or the other requirements (speed or balancing) there are other options but with both requirements that's really the only option. Balancing for both is done via balance leads to each cell not via the pack end terminals.
 

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I've just bought 5 x 125A l50S fuses as they were very cheap on flea bay. $10 each.
How are these holding up for you? I just bought two to try out. If any of them have failed for you, this would be a Bad Thing for the rest of us with higher ambient temperatures and higher altitudes.
 

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All right so far but 150A or higher would be better with the +40% hack.

Don't use one if you can't tolerate possibly being stranded with a blown fuse.
 

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john asked...
What is the best way to balance a complete 72 cell LTO pack?
One cell at a time? 😅😂🤣😙

john postulated...
...just charge while monitoring and hopefully the low cells will charge up to the others? Doesn't sound like the best idea.
because the premise with grid charging a NiMH pack is that the cells that reach full charge first don't accept more charge; they stop charging and start burning the additional energy off as heat while the lesser charged cells continue to charge.

As far as I've read here, if you try to do that to LTO cells, you will damage them.

The Panasonic NiMH cells appear to be designed to do this safely, tolerating this as long as they are not allowed to heat up too much, form gas, and vent.

Honda appears to take advantage of this, I think. By that I mean that for a while I was able to watch my stick pair voltages on my cell phone change in real time using a BCM modified to output this data via Bluetooth.

I observed that if I've let my car sit a few days and the pack got out of balance, by some cells self-discharging more than others, the BMS would noticed and would do what some call a "background charge". But I observed what I thought was it charging the pack up to a higher voltage than my grid charge ended, and it would keep it there for, oh, a minute or two, pushing what probably was significantly more current than a grid charger puts out. The cells that charge first burn off the excess charge as heat while the rest continue to charge. This appeared to be an attempt to "balance" what has been determined to be an "unbalanced" pack by allowing the cells that self-discharged more to accept charge a little longer (while the others burned off that extra energy as heat). At least that's how I interpreted it.

But with LTO, yeah, I think the consensus is they can't handle that excess charge.

This article, which attempts to find a way to get more energy out of LTO cells at low temperatures by raising the charge termination voltage, suggests that beyond a certain point damage occurs, because the voltage continues to rise until "electrolyte oxidation and active material loss in the cathode" occurs.

So yeah, it doesn't just happily burn off the excess charge as heat like NiMH. And honestly, I don't think NiMH is that happy about it either, and maybe non-Panasonic cells are even less happy about it, but that's a whole 'nother thread.

And take these pronouncements with a grain of salt, because someone who has owned LTO cells for two weeks knows nothing, and for having spent my Insight time on O2 sensors and such, I know just slightly more than nothing about NiMH - :whistle:

So my joke about balancing them one cell at a time is what the BMSs do, as far as I understand. I'm actually not going to put my LTO modules into my car until I find a way to individually charge and/or discharge each cell in-car, automatically. Does that mean I am going to buy an Orion BMS? Maybe... :eek: they cost more than my car...
 

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This article talks about damage caused by overcharge events.

Something to note is that two cells with the same capacity but at different voltages - at different states of charge - their voltages will diverge faster the closer they get to the end of a charge or discharge.

Since the LTO packs already provide voltage measurements for every cell, I plan to monitor these and have an automated shut down of charging or discharging when the first cell goes beyond a set limit, to avoid damage to that cell. (talking about bench charging here.)
 
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