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

[Baltothewolf]

Keep it coming man, we are reading!!

[RedDevil]

Wednesday morning I left without checking the lamps, knowing the switch was on.
Fair weather, slow drafting and a mild tailwind made that I got very good fuel economy, but it did regenerate after acceleration and could not sustain EV mode for long.
And sure enough, the lamps were stone cold upon arriving at work.
The connection failed again.

Going home I rechecked and retightened the connectors and the lamps lit up again.
I had my volt meter in the car, it read 118.1 Volt for my pack confirming it had indeed used just about nothing.
On my drive home I got some more support than usual, but still not much. Suffering from a strong side wind the economy was reasonable at best.
At home, the lights were off and felt like the lukiest of lukewarm. The volt meter gave 117.9, switch on or off; so apparently the chain was broken again.

This morning I found that the only connector that wasn't very tight was on the thick red wire from my top battery.
Instead of just squeezing it flat like before I bent it more narrow.
It gripped the lamp connector very firmly indeed, almost cutting into the metal.
The lamps lit up yellowy.

Going against the wind and rain, I had a meagre start yet came up at almost the same economy as yesterday's morning commute - even though I missed out on the best drafting opportunities and ended up following relatively fast trucks.
At work the lamps burned a low orange.

Going home, the same. Very good economy for the weather: 3.5 l/100 km, edging 3.4!
I had a partial tail wind, but also a traffic jam and wet road. 3.5 l/100 km is dry summer territory!
At home the lamps were barely glowing.
I monitored the voltage while the key was in and the lamps glowing. It showed 114,1 Volt.
Flipped the switch, the buddy pack voltage jumped to 115.5 Volt and slowly built up to a resting voltage of 115.9.

So today saw a noticeable drop in the voltage, right around the SOC where the voltage remains at its stablest. It must have taken some current.
Indeed the fact that my pack jumped over 1 volt on releasing it from the IMA pack and lamps suggests that it drew more than 2 Ampere even as the lamps were glowing that low, assuming a buddy pack internal resistance of 0.5 Ohm.

I bet it has spent over half its charge now.
I can only tell by checking how much time it would need to be charged to full again.

Now that my buddy pack voltage has dropped below 117 Volt I think it is safe to hook it up with the IMA system without the lamps in series.
This should really do something as the lamps were in fact restricting the current a lot.
We'll see. Tomorrow.

In other news, one of my colleagues has bought a Prius of the third gen.
He was looking to replace his diesel estate at the end of his company lease contract so I let him have a spin in my Insight, and he liked it a lot.
He also had an electric Renault Zoe as a courtesy car when his diesel Laguna was in for service, and showed it off to us. That really made him want electric.

In the end he could not afford the Zoe and settled for either a Toyota Auris Hybrid or a Ford Focus, after test driving some Insights and not liking them half as much as mine.
But when push came to shove he did drive that Prius on a whim and was amazed about how good it was, so he bought it! It was delivered this afternoon.
So tomorrow I'm sure our traditional lunch break walk through the park will not take place

[RedDevil]

Hooking it up without the lamps got me great support in the first few miles this morning - I saw the battery rise to full and at a constant speed it maintained EV support - a constant rush of electricity keeping the gas use level low (not zero, but definitely low).
At a T junction it threw an IMA code so I switched the lamps back in series. Again, they did hardly glow at all.
At work the lamps were slightly warmer than ambient. I could not see them glow anymore. FE was quite good for a morning commute - especially this cold and foggy. But foggy means no wind - and that helps.

Going home I hooked the batteries up straight again, without the lamp shunt.
On the highway, no problem whatever, but neither did it yield good FE. Nearly home in the residential area it threw another IMA code. Ah well. Reset and do the last mile.
The battery tested at 115.5 Volt. Hm, seems it did not drop much.

I compared the 3 packs and one was 0.4 Volts lower than the others.
I opened the battery box and found one cell that dropped below 3 Volt while the rest was hovering around 3.15 Volt.
One bad cell then, or what?

Time to hook up the chargers.
The bad cell quickly came back in line with the other cells. The pack was soon indistinguishable from the other two, based on overall voltage. On all 3 pack it quickly built up to over 40 volts on charge (3 Ampere).
And it stayed there.
3½ hours into the 3 Ampere charge it's getting late and I quit the charging. Still at 41.0 Volt while the cutoff is 42.6 Volt!
It is clear that I pulled the pack to almost 0% SOC. As I must have put over 10 Ah into this 12 Ah pack and it still does not show signs of nearing a complete fill. I want to monitor that last phase, to see whether the BMS does balance the cells again or not.

While the batteries are charging I could upgrade the cases they are in.
Simple plastic page binder strips cut to length now serve as BMS wire organizers.
Black 3M duct tape, one edge folded over to form a non-stick lip, make sure even the last bits of exposed case metal are insulated - though anything bearing current was isolated on its own anyway.


While and after doing so I hook up the volt meter to the subpack I work on just to make sure all is well.

On the last subpack the voltage suddenly dropped from 40.6 Volt to 30 something.
Argh! Is it a short? And where? I should see smoke or find something getting really hot now... but everything seems just normal.
I unplug the charger and the voltage jumps back up to 39.8 Volt!
What the?
OK, the light on the charger had turned green, indicating the charge is done.
Except I'm pretty sure it wasn't yet. But what then causes this?

I examine the batteries up close and pull up the BMS circuit from the box.
The BMS wire connector is loose!
So the BMS shut off the pack, and the charger shut off itself because the voltage outside the BMS soared to its cutoff limit. Then the charger puts out a feed voltage of just 30 Volt while maintaining its green light indicating a full charge.
The BMS connector goes back in and all its well. Hooked up the charger and it goes again.
I need to finish the charge tomorrow. It is a full charge, that I know now.

The Prius was nice. Just a Comfort - but it has Climate control, HUD and a lot of other stuff. All in all quite a bargain.

[RedDevil]

Three commutes on the new charge all run with the lamp shunt, batteries still at 39.4 Volt each.

Using the lamps I get one check IMA error per day, or none. Usually when keyed off and on within seconds - typically at the lights, supposed to stay red for a long time, engine does not AutoStop, I key off and the lights go green at the same moment, jumping 3 lanes in their usual cycle .

Other than that, the lamps seem to solve the problem in a crude way. Crude as the support remains tiny with the limited current.
I do need to be able to switch them in and out, I want to order another relay together with a bunch of LCD displays and some shrink sleeve (can't have enough of that!)...

My economy remains about the same as before I started using the packs.
What is different is the weather. Temperatures plummeted from Indian summer like to near freezing all day. Still getting around 60 mpg on my commute is quite something, especially considering I lost my upper grill block in a gale a few weeks back.

Cold charging?
Right now I'm recharging the packs for the second time.
This time I took them in, as it is too cold to stay in the shed for long.

Hooked up with the charger, two packs jumped to 40.6 Volt - but one went as high as 41.1!
Oh beep, do I have a bad cell or what?

I unscrew the lid and test each cell for voltage. Hard as the iron box is almost too cold to handle.
Hm, the cells are pretty much even. And the whole bunch now shows 40.9, still charging.... and goes down to 40.8, still charging???

The other subpacks are at 40.7 Volt now.
Their iron boxes are cold too - but just a little less...
The coldest pack had been sitting in the car in the toolbox together with the other two, but closest to the upwind side of the car. So it was just a few degrees colder that the other two, and that was enough to increase its internal resistance substantially!

So, while the effect on my economy is not really impressive this far, I'm very glad with the pack being portable. As charging them around or below the freezing point is apparently a bad idea; being able to take them inside the house solves that.

Below 10°C / 50°F the internal resistance rises quickly on charging.
Do not charge LiFePO4 when cold - CONFIRMED!

[RedDevil]

I was a bit lazy on my build an report these days, as my 5 year old daughter caught the flu and we all are a bit strained now; not really ill but under pressure.
Work outside is difficult to boot; cold and rain, drizzle, rain.

When I charged the batteries to full after the first use I did not open the tops to check the cells, and it had been bugging me.
Especially because I had opened the one that dropped its charge below the other two on the bottom end.

I found one cell (cell 2 of the middle pack aka 'see no voltage') was just below 3 Volt while all the other cells still held 3.18 something. I had experienced intermittent support before that; lamps would glow on start, but be cold on arrival.
It jumped right up to 3.3 Volt on charge so I let it be. Closed the box and did not look back. Stopped charging when the voltage started rising above 42.1 Volt and left it at that. That was a week ago.

Last Wednesday I did the second recharge, see previous post.
This time I did not wait for the packs to go all the way down, so no bottoming out of cells.
I wrote that post while the packs were still charging.

Wednesday charge part two
After 3 hours one of the packs (the 3rd, aka 'speak no voltage') voltage rose slightly above the other two, so I kept monitoring that as it rose gradually up to 41.6 Volt on charge.
Then the light on pack 2's charger went green. The charger does that at 43.8 Volt and cuts off. So that pack is full...
Pack one (see no voltage) goes green too. Okay.
3 stays red, the voltage climbs steadily to 42.6 Volt, adding a tenth every 5 seconds right on to 43.7 Volt. The light remains red.
Hum hey, what to make of that?

I disconnect the charger on 3 and the voltage recedes slowly to 43.4 Volt.
It is genuinely full.
If it were unbalanced then the BMS would cut the charge and balance back the overloaded cells. The voltage would drop faster than this.

Time to check the other two packs. Pack 2 is just 40.6 Volt! See no voltage, indeed! Do I have a bad cell?
Pack 1 shows 41.8 Volt right in between the other two.

When I hook them up to the charger the voltage rises 0.5 Volt, stays there for a few seconds, then climbs and shoots to the roof making the charger cut off. Then they sink back to 40.8 and 42.0 Volt respectively, which recedes to 40.6 and 41.8 after a few minutes.
That must be the BMS sensing an overcharged cell, cutting the power and balancing it gently back. At 75 mA if the specs are right.
As long as the other cells aren't full this can take a while!

But analysis based on a guess won't cut it for me this time.
Off goes the lid and the cells get a voltage check.
Indeed, one cell (cell 2 of pack 2 again) shows 3.65 Volt while the others are around 3.35 Volt.
If I hook up the charger it jumps to 3.85 Volt in a few seconds, then the BMS cuts the charge and the voltage sags one hundredth every few seconds.
So, to balance the pack I need to hook the charger up for a few seconds every 5 minutes?

I ran out of time, literally; was already burning midnight oil.
I left it at that for a couple of days.

Friday: topping off the charge
I thought it may be a good idea to help that one overly charged cell down so the other cells could be charged too.
I have a TEC to use for an electric WAI (on which I'll start work when this PHEV pack is no longer drawing all the time I want to spend on ecomodding, and more). It would draw just enough to gently discharge that cell.
It does, at about 0.5 Ampere; I can increase the draw a bit by pressing the hot edge to the cold battery case and the cold side to my fingers

Even so, the charger at 3 Ampere quickly fills it back up to cutoff.
Measuring the overall voltage reveals that the other cells are picking up though. 41.1 Volt, next cycle 41.3 Volt, then 41.8 Volt, then... 43.7???
The light on the charger stays red!
Testing the other cells, all are above 3.5 Volt. Cell 2 now is the lowest at 'just' 3.43 Volt
A few cells even venture above 3.6 Volt, but the BMS slowly brings them back in line.

A gentle discharge on a few cells sees the other cells go to 3.8 Volt at the next cycle, but all are brought back in line.
Then I discharge those a bit to test the remaining cells and BMS leads, and indeed they all get balanced down too.
The BMS top balances perfectly on all cells!

Pack one must be close to perfect balance, at 41.8 Volt.
Indeed it takes just a few cycles before it reaches 43.high and the charger remains red.
All three packs now stay red on the charger. The charger fans spin up for 3 seconds and die again, seeing no current flow in.

Conclusion:
One of my cells, cell 2 on See no voltage, has almost certainly less capacity than the rest.
While the BMS was supposed to do top balancing only, I suspect my first run drawing it low showed that it did in fact do bottom balancing too, so it gave some support every time I reconnected the packs.
But that also caused it to be the first cell to top out on recharge.
I'll try to prevent bottoming out from now on, see if that prevents the top off unbalance.

Nonetheless, the combination of the BMS and charger characteristics seem ideal.
The BMS cuts off the charge if a cell reaches 3.85 Volt and releases it again when it drops to 3.65 Volt. It will keep balancing the cell down to 3.6 Volt.
The charger cuts off at 43.8 Volt, which is 12 times 3.65 Volt.

A perfectly balanced pack will be charged to 3.65 Volt per cell, at which the pack meets the chargers max voltage so it takes no more current which makes the charger cut off.
The BMS then forces the cells to sink back to 3.6 Volt, leaving the pack at 43.2 Volt.

A slightly unbalanced pack will see some cells go higher than 3.65 Volt while some other may not even reach 3.6 Volt. But as long as the balancing current flows the chargers will maintain 43.8 Volt. So while the high cells are fighting the (then) low current flowing in, the low cells will all eventually reach 3.6 Volt, or at least get very close to that, before the charger cuts off.

A strongly unbalanced pack will cut off due to overcharge, and will keep doing that until the other cells near full charge too.
I do have a trick for that; my chargers cut off, but I can link two packs together.
One (full and balanced) pack cannot overcharge the other pack as a whole but it can recharge the unbalanced pack every time the one overcharged cells reaches its release voltage. I just have to trust the BMS will do its job.

One big reassurance is the total lack of heat development on the BMS, batteries, cables and connectors. Everything stays at ambient - even the BMS while top balancing 8 cells down at once. But that has an array of cooling fins almost as big as the palm of your hand (not mine, I have huge hand palms - and tiny fingers! Mole hands) to dissipate about 2 Watt for that.

The only things that do produce (some) heat are the relays on the terminals and the lamps.

[RedDevil]

While I'm happy with the BMS and chargers an such, the delivery part of the system leaves much to be desired.

Last time out I could not make the lamps light up. I suspected a bad contact, but could not find it.

This evening I took the lamps apart. These are 6 20 Watt 12 Volt G4 lamps in reflectors, 3 parallel pairs of them, so 24 Volt would see 120 Watt and 5 Ampere.
But it would never be 24 Volt as my pack is only around 120 Volt and the IMA system would never go below 100 Volt.
So unlike my 12V lamp shunts this would not burn through.

You guessed it by now they DID burn through!

3 of the 6 lamps did burn out, and with just 2 spares this setup is grounded for now.

I could use something blunt like a mains heater as a shunt.
But I'd rather have a device that limits the current to a preset level.
I have been looking about but the world seems to avoid current limiting, or I'm lousy at googling it.
Any suggestions?

[RedDevil]

In fact all 6 burned out!

I blame the bad connection in the makeshift plug. The wires just wouldn't solder onto the tabs, they gripped it by shape - but not enough.
So it had not been making contact for a while. I depleted the battery in EV mode, drawing its voltage way below the buddy pack - enough to make it bridge the bad connection and suddenly deliver the full voltage differential to the lamps.

I redid the tabs with a 120 Watt heavy duty soldering iron (the same I needed for the 6 mm diameter wires in the pack - a 30 Watt iron is helpless with those) and now the tabs are soldered through.

Also I swapped the lights round so the reflectors face the full open side:


It is starting to look like something that belongs on the front grill
Yet I'd rather not have that high voltage cable run the length of my car for a vanity show

[RedDevil]

I got mail: 2 new panel meters, one double switch relay, two tiny relays for switching purposes and some 20 amp diodes.

I'll use the diodes to prevent back current, which I think limits net flow now.
The panel meters are to measure voltage and current flow.
The small relays for a push-and-hold style control which will drop off after key off, rather than the switch I keep forgetting now, which causes IMA errors.

The double switch relay will be the first to get used though.
My lamp shunt has a 2S3P setup so it can handle up to 24 Volt, but usually the voltage differential is below 12 Volt.
The current flowing to the IMA pack drops under 3 Ampere then.

I will power the coil in parallel with one 3P group of lamps, switching the other group in series when it is engaged, and parallel when not so it will be either 12V high current or 24 Volt low current.
That should allow for a lot more influx under normal conditions while protecting the system under high use.

It is still waiting because when the mailman left this happened:


on top of other issues and woes that kept us on our toes these last weeks.

Meanwhile, using the 2S3P lamp shunt I use about 1.2 kWh a week, for about 300 miles of driving. The effect of that cannot be more than a few %, and it completely drowns in disturbances like the storm I had to drive through - the same that killed our tree.

On a positive side, the imbalance occuring at the first charge is gone.
On the second charge one pack ended up fully balanced, taking the max 43.8 Volt from the charger without the BMS tripping; all cells below 3.8 Volt.
The other two had the BMS tripping, but were very nearly there. Just a few minutes of gentle balancing by the BMS got them in line.
On the third charge only one pack triggered the BMS.

Since then all packs end up balanced right after the charge.
Moreover, they do so in perfect harmony; all 3 chargers stop just a few tens of seconds apart after over 3 hours of charging!
Resting voltage after being detached for a night is 42.2 or thereabouts; all 3 within a tenth.
Last time I did not even bother to check the voltage. It just works fine.

About the post title:
All this tinkering with batteries and lamps and causing system errors gets on my nerve a bit.
Every strange sound, relay click or whatever sends an alarm signal up my spine. I keep telling myself that it is all normal, or the car behind is making that sound etc. to reassure myself.

When I smelled a burn yesterday right after using EV mode for a while I thought someone must be burning leaves somewhere, but just to be sure I switched off the lamps.
At work I got to the boot and found that a tiny leaf had landed in the boot, right on top of the glass of one of the lamps in my shunt.
It had a burn hole the size of a nail head...
I'll add some wire mesh to shield off the lamps

[ExDelayed]

Interesting thread so far. Need to keep track of it for later.

[RedDevil]

I tested the relay. I found it tripped at 7 volt or so, but I wanted it to trip close to 12 - the longer it allows all 6 lamps in my shunt to run in parallel, the better.
A 100 Ohm resistor in series with the (138 Ohm) coil did the trick.
It will also protect the coil when the voltage rises further than 12 Volt.
The alternative was to have the relay run parallel with one of the lamp sets, but I was afraid it would jump back and forth as the voltage over the lamps in series might be too low to keep it engaged.

If the relay is engaged it cuts 3 lamps from one feed and the other 3 from the other feed and connects them, so they run in series instead of parallel.


On the left is the power source; one wire goes to the (relay switched) plus terminal of the IMA system, the other to my buddy pack control unit.
On the right are the relay coil connectors, which are connected to the left connectors by a wire and a resistor.
Next to the right are the switched leads to each 3 lamp set.
If the relay is not engaged they are connected to the feed on the left.
If the relay is engaged they are bridged by the wire on the second left.

I made sure the contacts did not touch and locked the wires so nothing moves, yet I did push some isolation tape in between just to be sure.


The lamp unit rebuilt:


Then there was the tree that couldn't fly.
It tried and it went all wrong.
I could have told it not to try, but trees can't hear very well either.

Trees are green and hybrids are green, so the combination must be a tree hugger's dream come true.

But maybe not like this, like cut in boot size chunks.
(one was too long after all and filled the rear footwell)
On the plus, now tree huggers could hug this one tree simultaneously all over the world.
If you love fungi too hug the lowermost part of the trunk.

The workers at the municipal waste disposal started hugging the chunks with their grappler right when I dumped them in their big skip... the chance for a global community hug may already have been lost.
Anyway my hybrid is red not green.

Had to get that out while my back is still sore