2nd gen Honda Insight parallel portable plugin hybrid battery pack build thread

[RedDevil]

Cobb had no trouble feeding his pack with 2 kW constantly, but 4 kW caused problems when driving slow.
I believe that was because the IMA system has no way to spend 4 kW on average when driving slow, so the voltage must have risen too much.

So it looks that whatever the current does, if the voltage is good the system will not cause trouble. And if it does I can reset the codes with my UltraGauge.
I would not have to worry about that, as in my setup the current strength will depend on the voltage drop compared to the parallel pack voltage. When driving slow the IMA voltage should float around the base voltage of the parallel pack, and the current would be low.

[RedDevil]

I just bought 36 of these cells, 3 metal boxes to take 12 of them each, wires, nuts, 6 Anderson connectors, 3 36 Volt chargers, 3 BMSs, etc.

The BMSes are 12 cell 55 Amp cutoff top balancing type. And of the not yet in stock, will be sent in a fortnight type
But there is enough to prepare and test before I get to mount them.

Splitting the pack in 3 may seem strange, but we could not get a 36 cell BMS with the proper specs. Also the 12 cell subpacks are a lot easier to carry and safer to handle than one 36 cell pack, and they can shed any heat they'd produce easier.

The steel cell boxes are relatively heavy and quite sturdy. The lid has a recess where the wires pass through and the charge connectors can be mounted. The boxes are (just) big enough for 16 12 Ah cells, but I need a divisor of 36.
12 cells leave ample space for the BMS, padding and short protection.

While these BMSes are not designed to switch voltages of 117 Volt combined, the fact is that the packs are matched against the IMA pack which should always be in a range between 90 and 122 Volt, but most likely 105 to 117. That should be 30 to 41 Volt, and 35 to 39 Volt per cell block. Values a BMS should be able to handle.
Even if the blocks would not mach charge it is unlikely any of them, held in threesome against the IMA battery, would see extremely over 45 or below 0 Volt.

No pictures yet, the stuff is in boxes in the boot; I'll unpack it tomorrow well away from my offspring's little and unruly fingers.

[RedDevil]

First commute with the batteries in the back yesterday; I almost broke my best commute FE ever.
A good sign.
If they can do that while still in their shipping package, imagine what they'd do when hooked up to the car

Magnets schmagnets, duct tape a LFP battey to your fuel line

[RedDevil]

Back home again (bought the batteries on holiday, went to work and tend&mend my house a few days, then joined my family again for the last part) and finally some time to check on what I dragged in.

The cells. 16 here, the other 20 in the unopened box below. Couldn't find my Fluke while in the flurry of reorganizing the house and domesticating the kids so not tested anything yet.



Leads with Anderson connectors, one pair for each 36V battery pack.
Copper nuts, connecting plates (to be stacked double for lower resistance), crash resistant steel boxes with padding and lining, charge connectors with a lid.
The boxes were designed for 16 of these cells but there's little room for the BMS board then. I needed a divisor of 36 so 12 was logical, and there is room to spare now.



3 '36 Volt' (43.8) 3 Ampere chargers should be able to fully charge them in 4 hours.



Still waiting for the BMSes to arrive, plus I would like some additional googads as a twin line kill switch, LED volt meters on the car and each battery and some proper wire protection.

Meanwhile I'm to design a way to safely lodge those 3 boxes in the rear void behind the IMA battery. I might just make a couple of plates, one high, one low, covering the whole with 3 box sized holes so they stay put. Preferably in alu sheeting, pop rivets on the seams etc. so it kinda looks like a commercial off-the-shelf drop-in installation.
Oh, I really need something like a company logo; Cow&Chicken's pantless guy getting hit by a lightning bolt in the pantless part or so, but done in a subtle way, of course.

[RedDevil]

The BMSes have been sent, I expect them in tomorrow.

Meanwhile I found my Fluke and tested the chargers and cells. Just a quick voltage check, no load testing.

All the 3 chargers tested 43.7 Volt. They seem evenly matched, which is nice.

The 36 cells all had 3.36 Volt +/- 0.02. 3.37 and 3.36 were most common.
That was a bit higher than I expected, but then they were charged to max before shipping and probably still are; they'd drop off to 3.2something if they lost even a few % of their charge.

For fun I tried to test fit the battery boxes in the foam filler, and to my surprise they almost did!

If I dent the foam ever so slightly they would.

But I want better ventilation around the boxes and obviously the cables will have to go somewhere, so I'd have to tear up some of the foam then.
Better leave it intact and make my own dedicated battery box frame.

The good news is that there should be ample room for the batteries and what not, even with the boot floor in place and set at its lowest position!
A PHEV conversion that does not reduce practical luggage space, seems like I can charge my cake and eat it after all

Now I made a quick drawing of the connection scheme.
I left out the contactor, fuse, volt meters etc, just the basics here.


The 6 Anderson connectors are identical and obviously fit each other.
Which got me worried, what if I, or anyone else that ever gets hands on these, would accidentally connect two that weren't supposed to be connected?

First, the order in which the batteries hook up to the car is not important.
It would not even be important if the voltages were not equal, just as long as the total voltage is right.
It is just a series string. So any car connector can be connected to any battery connector.

If the battery connectors get hooked up to each other, then they will share their voltage. If one is charged to a higher voltage than the other, they will start evening out. It wouldn't kill the batteries.
The nice thing about Anderson connectors is that you need to turn them 180 degrees to interconnect, so when the plus is on the right for one connector it is too for the opposing connector; because that needs to be turned upside down to connect, undoing the mirroring effect.

But danger lurks when the Anderson connectors on the car get connected.
If for instance the left and middle connect then the right connector would have the full car IMA system voltage on it.
And if the outer two get connected, the middle one would have the full voltage with the wrong polarity!
The simple yet elegant solution is to bolt those 3 connectors to the car.
Anderson connectors even have holes and nut locking cavities for easy fixture. I'll put them to good use.

[RedDevil]

BMS (3x) are in!


It looks like it is neatly constructed and it is actually quite heavy.
The white thing is a temp sensor, shutting off at 90°C


Especially fit for my Lithium-Iron-Polonium (instead of LiFePO4) batteries
At last, a nuclear energy powered car

Now I wonder what I could use best to wire up all the individual cells.
I was thinking of using old computer hard disk flat-cable, pairing the strands to minimize the chance of one strand breaking and unbalancing the cells.
Good idea, or bad? Fire away!

[RedDevil]

Got the lid off the IMA battery again, to check on the terminals and see if my connectors would fit.

Hooked it up with my Fluke, flipped the switch, keyed on and there it is.
Mind the red wire is on the negative pole. Hence the minus in the display


I can only mount the (flat) connectors by bending them. The terminals are surrounded by plastic edges.
I hoped there would be enough clearance to slide them in under that plastic from the left towards the right (stepped up) terminals, but there isn't.
Ah well, the bent connector does fit.

The voltage was a bit of a surprise, as I have not seen it above 108 Volt before. But I feel reassured about using a 117 Volt buddy pack, if 111 Volt is within the normal operating range then the remaining 6 Volt difference won't kill it.
The total internal resistance of all cells and BMSes is about 0.8 Ohm; hooking the pack up will not see a crazy surge.
I'm glad I went for 12Ah cells instead of 10Ah, but now I wonder if I should have used even bigger cells for lower internal resistance.
Time will tell, I guess.

I still do need 2 x 1 meter of additional cable to my switch and fuse etc. box (car-side buddy pack terminal), and that switch.

[Daox]

Looking very good.

Sorry if I missed it, but how do you plan on connecting/disconnecting the two packs?

[RedDevil]

Originally Posted by Daox

Looking very good.

Sorry if I missed it, but how do you plan on connecting/disconnecting the two packs?

Thanks!
It is still in the works, but I want a double relay/contactor inside the 'safe area' (the IMA pack and electronics are in a big black bucketlike box, shielded by a big aluminum piece.
There is ample space in that for some extras like my relay/contactor.
I will wire a 12V switch from outside the box (obviously) to operate the contactor.

The physical connection is by 3 pairs of Anderson connectors.
I need to fix mount the car side Anderson connectors to prevent that anyone could ever interconnect them, which would have the remaining connector bear the full voltage. All other interconnections would be safe, if my analysis 2 posts back is correct.

Had another mail from the supplier one hour back.
Working hard to get everything I need so I can start the build coming weekend.

[RedDevil]

Filling in the last bits. Two relays (one for each terminal) and some wire and stuff from the supplier that sold me the cells.
Fuses, fuse boxes, pin connectors, a 12V switch to operate the relays, a 200.0V digital voltmeter, orange isolation tape, high voltage warning stickers, etc. from another.

I was looking for orange cable and cable tubing as those are required for high voltage cabling in cars, but it was hard to get and shipping cost was unnecessarily high.
Then I saw the orange tubing in my Insight was taped. So I got the insulation tape instead.

The high voltage stickers only come in batches of 10. Guess I have some spare ones to play with. The company urinal may get used less frequently in the coming weeks