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post #1 of 50 Old 09-30-2018, 04:45 PM Thread Starter
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Lithium DIY

All these talks about Lithium conversions made me want to try one. Voltronix kit is nice, but quite a bit spendy, and offers way more range than I need. Why pay
extra for something I won't use ?

I had some conversations here with other forum members to figure out the direction. One thing I wanted to avoid is having to reprogram Sevcon, since
cheap Canbus adapters are nowhere to be found, and "old sevcon software" thread turned into some kind of joke. So I wanted to try to match the Lithium power
pack to the factory Sevcon programming, and figure out the charging problem later.

For the Lithium cells Nissan Leaf modules are quite nice, and I may end up using them, but there one can either do 14S or 16S configurations, which could
be either too little or too much. So instead I decided to do a trial run with a small pack built out of Ford C-Max hybrid cells.

Those are 5.5Ah (or so) cells made by Panasonic. They are rated at 150A continuous discharge (at least that's what the seller claimed), and for both the
discharge current and capacity reasons I decided to go with 4 modules, 15 cells each (switching to 14 later depending on findings).

Below are the pics of the build. Next step is to send the DeltaQ charger for reprogramming to get a correct charging profile going on, and then I can
start doing some range tests. I haven't removed the lead-acid batteries to test for worst case (loaded) scenario. Also note the use of improvised parts -
trying to make it cost efficient

















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Last edited by cricketo; 09-30-2018 at 04:48 PM.
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post #2 of 50 Old 09-30-2018, 10:00 PM
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On the topic of improvised parts:

- I have used the copper pipes squashed flat, drilled and crimped for cable lugs. My crimper (chinese knockoff) works well with the copper since it is nice and soft. The best (least heat) connection between these improvised lugs, that I have experimentally found, is to stack a flat washer on your stud (or bolt), then stack 2 or more lugs all touching each other, then another flat washer, a lock washer, and finally a nylon lock nut. Tighten the lock nut until the lock washer starts to compress but stop before the washer is completely flat. Not sure why. Just an experimental result.

On the number of cells in your pack:

- If your charger is charging to 55.4V, 14S sounds like a good number of cells for your pack. Wasn't it the low end that dictated 15S? If the SEVCON cuts out at 44V, 14S gives you 3.14V per cell. That's leaving some battery capacity on the table. Your 15S makes the SEVCON drop out (if 44V is right) at 2.93V so it should perform until your BMS decides to shut you down. Without the hesitation that I was seeing.
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post #3 of 50 Old 09-30-2018, 10:41 PM Thread Starter
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I think you're right. I did a few runs today with 14s and 15s configurations, and 14s performed quite well. At one point it got charged to 100%, probably caught it before charger went into trickle mode ?
Either way, I did two trips, 1.2-1.3 miles, spending about 40% of the charge each time. Difficult terrain, some uphill. That's while still carrying 700lb of lead-acid batteries. Fun thing about having a small
pack like this is that it charges back up extremely fast So next step is charger programming and dropping dead weight. Will post an update.

More thermals right after the last trip:





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post #4 of 50 Old 10-01-2018, 09:09 AM
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Quote:
Originally Posted by cricketo View Post
More thermals right after the last trip:
I like the temperature reference on this camera. Can you post the brand and model number?

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post #5 of 50 Old 10-01-2018, 10:21 AM Thread Starter
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Therm-App (https://therm-app.com/therm-app/) is the brand. It's a bit spendy in comparison to Flir and Seek Thermal, but it has way better image quality for the money, and
has ability to replace optics.
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post #6 of 50 Old 10-01-2018, 02:41 PM
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You really cant discharge any 5+ah cell at 150a. Seriously you should aim at around a 3c max discharge. Not 60c, which is what you would have to achieve if your controller was pulling 300a under heavy load. there are no cells made that will deliver 30+c continuously, and to get any usable range you should aim for at least 160ah . If lifepo4 (3.3v nominal)then 16 cells. You must have some form of BMS to monitor the pack and deal with over voltage / charging as they age, and under voltage under load.

There are good reasons why conversions cost as much as they do.

Please note poor crimps are one of the biggest causes of failure and fire. Proper crimps and a crimping tool are not expensive. They are also plated which helps to ensure no corrosion at the joints. Dont solder any of the main power cables, if you get resistance and heat you can get the joints to come apart.

Also dont forget to constrain your cells, They must be stopped from swelling as once they swell they will lose capacity very quickly.

Good luck with the project. But always remember that the vehicle must be safe when left on its own charging, and when being operated by someone who has no idea whats in it and that they have to watch out for low cell voltages.
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post #7 of 50 Old 10-02-2018, 12:23 AM Thread Starter
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Quote:
You really cant discharge any 5+ah cell at 150a. Seriously you should aim at around a 3c max discharge. Not 60c, which is what you would have to achieve if your controller was pulling 300a under heavy load.
I found the government report for that vehicle - https://www.energy.gov/sites/prod/fi...yC-Max3817.pdf

It has a 7.6kW pack made out of 84 cells, with a 310.8v pack voltage (nominal) - it appears it's a 84s configuration, without anything paralleled. The doc the goes to state :

Quote:
The Medium PHEV battery target performance goals of 37 kW discharge power and
25 kW charge power are shown as a dashed line.
So the pack is designed to discharge at up to 37kW. At nominal voltage that is 119.35A, which is the current on each cell due to pack's series configuration.
In my case there are 4 cells in parallel, meaning the pack is capable of handling at least ~480A of current. 119.35A though is likely not the cell rating,
and I am more inclined to think stated 150A by the seller is actually accurate, though I haven't found the official spec sheet from the Panasonic yet.

So the report above doesn't really stress peak vs continuous discharge, but I found another one :

https://avt.inl.gov/sites/default/fi...-maxenergi.pdf

This one uses 50.2kW figure for peak draw from the battery. Given the same configuration in 2013 vehicle, that's 161A draw per cell...

Basically, it is a certain different game here when relying on cells made for some electric vehicles with specs significantly exceeding the needs of the Ranger
due to sometimes order of magnitude more powerful drivetrains. One of the things I am trying to do here is to figure out a simple way of achieving the
conversion with reasonable results.

I also have another update on the project: just got the Lithium algorithms programmed into the charger. It now supports the following:

#67: 49.2V
#128: 54.7V
#211: 55.44V
#163: 57V
#53: 58.392V
#123: 59.88V
#164: 60.792V
#135: 62.256V
#177: 65.688V

If anyone is interested in that, shoot me a message and I will share the contact info for the shop that does the programming.
With so many options it is now possible to chose between 12, 14 and 16 series configurations. Last one may require DC-DC converter replacement,
but apparently they can be had for as little as $80.

Good reminder about the crimps and stuff - I took certain calculated shortcuts, but I'm very diligent otherwise.
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post #8 of 50 Old 10-02-2018, 12:51 PM
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If the pack is 7.6kwh (thats not 7.6kw which is a power figure not a storage capacity) and with a constant voltage of 310v, a 37kw discharge rate would give approximately a 5 c discharge (c being the nominal Ah of the pack). So if the cells are as you stated earlier 5+ah, then thats less than 30a peak.If the pack is 7.6kwh divide that by 310v and you get an ah of the cells of 24.5. So if your cells are 5+ah the the pack must have at least 4 in parallel to get the ah,which means each parallel string of approx 25ah could at 5 c do 125a discharge. Thats achievable. You really cant get normal cells of 5+ah to discharge at 150a.
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post #9 of 50 Old 10-02-2018, 01:51 PM Thread Starter
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Correct me if I'm wrong, but I think you're arriving at incorrect results by using C-rate as a way to determine discharge current. Given it is a rate, it is tied to time, and specifically to 1 hour. So yes, drawing 7.6kw for an hour will amount to 1C discharge. Drawing 37kW is not 5C though - it is 5 times 5c, because the pack will last only for 12 minutes at such power draw.

That's where going by basic I = P/V is less confusing, it gives the answer to the instant current value instead of the rate of any kind.

With that said, I think I pulled the specs on the wrong vehicle - cells I have are from HEV, not from PHEV. I will have to follow up on that.
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post #10 of 50 Old 10-02-2018, 02:12 PM Thread Starter
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Yep, here are there correct specs:

https://www.energy.gov/sites/prod/fi...yC-Max8698.pdf

281.2 nominal voltage, 76 cells, 25kW power draw. That is 88.9A.

Last edited by cricketo; 10-02-2018 at 02:17 PM.
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