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

[RedDevil]

EDIT: This is now a build thread! I bought 36 12Ah LiFePO4 cells, boxes, bridges, nuts, wires, connectors and BMS and am now done with tying these together.
Next phase: car harness...
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I want to design and build a portable battery pack and run it parallel to my Insight's hybrid battery.

The goal is to pull up the state of charge of the main hybrid battery so the IMA system will use the EV mode and boost more and to do away with forced recharge while running on gas.
It is not supposed to act as a full EV - both the Insights motor and the intended battery pack are not powerful enough for that.

The battery pack needs to be portable to charge it at home and at work at the mains with no fuss.
That should solve charging issues in cold or hot weather too.

It needs to have a (more or less) stable voltage corresponding to a high state of charge.

I don't want DC-DC converters in the parallel pack as I don't want the extra heat they provide, nor any overcharge issues.
A straight pack cannot overcharge the main hybrid battery when its fully charged voltage is below the max for the main battery.

Portable means I aim at no more than about 15 kilo / 30 pounds.
Charging voltage is 230 AC as customary in Europe.
Capacity needs to be at least 1 kWh; that should save me about half a liter of fuel per charge.

Total cost should not exceed 1000 € ($1100) by much, but I might stretch that for more capacity if worthwhile. Yet the aim is to have a ROI within the lifetime of the car for this mod.

I will break down the design over several posts and link them from here as a starting point.
Please do feel free to comment - I sure can use some help on this.

While we're at it a *** WARNING: Hybrid batteries contain high voltage components and can kill ! ALWAYS take the necessary safety precausions. *** so you know I know and I know you know, etc.

(I go bonkers for subtlety )

Some basics: power usage (2nd post)
The IMA hybrid system (3rd post)
Battery types

(thread under construction)

[RedDevil]

A hybrid can run on electricity, but like most the Insight does not come with a plug - it has to make its own.
It will do that by using the 10 kW pancake motor/generator bolted to the crankshaft where the flywheel would be.

When decelerating the CVT gearbox will rev the engine with DFCO and valves shut for minimal friction so the generator can charge the pack.
Likewise, under light load the generator will sap some of the engine power to keep the battery charged.

When accelerating the motor will pull in unison with the engine, and under very light load the motor will turn over the engine in DFCO etc; as it does not use gas then that's pure EV mode despite the moving pistons.

The Insight does have a 12V starter motor but no alternator; instead the 12 Volt system gets fed by a DC-DC converter powered by the IMA system.

The hybrid principle dictates that electric usage and regeneration are in balance - in the long run you cannot pull out more than you put in.
Which is a pity, as there are way more opportunities to use that power to good benefit than there are to gain it back for free.

Hence my plan to boost it.

[RedDevil]

The Insight hybrid system (IMA) has a 84 cell NiMH battery pack which can run between about 99 Volt and 120 Volt, but typically sits around 107 Volt (which was exactly what I've measured from my own pack on 2 occasions) when it is about 50% charged.
Some excellent data on it can be found here; AVTA: 2010 Honda Insight HEV Testing Results | Department of Energy. (thx Cobb )

(I will add some stuff here later)

[sheepdog 44]

What capacity do you want the booster pack to be? If you want it to be portable, like you take it out and charge it inside, it can't be very big or heavy. The stock pack i guess is at least 50-60 pounds. If you want to double the capacity you'd need lithium if you want to take it out regularly.

If not a regular 120 volt extension cord might be best plugged into a regular wall outlet both at home and at work.

[RedDevil]

The US Dep. of Energy tests suggest that the voltage of a half charged IMA battery sits around 105 Volt, a bit dependent on the mileage on the battery.
My relatively lightly used battery rests around 107 Volt.

110 Volt and upwards corresponds to at least 90% SOC; at that level the Insight should use all means to reduce it by using electricity.
The max level in the test is 117 Volt.
In order to have good boost the parallel pack needs a lower limit of about 110 Volt and an upper limit no higher than 117 Volt.
That is just 6% between fully charged and empty.

IMHO only LiFePO4 batteries can operate in such a tight range.

I could string 36 of these together to get 117 Volt worth, but I'd need a BMS and the like.


Alternatively, nine of EV-Power | LiFePO4 Battery Pack (12V/12Ah PCM) would make me need just 9 simple 12V charges and the standard stuff, but are a bit pricey.


Then 3 of these bicycle batteries EV-Power | Battery for EV bikes - EVBike 36V/10Ah (black case) come with chargers and all.

(I would not use the antlers just the battery)
Having 3 separate units makes installing and charging relatively easy, sadly the charging time is not that great, nor is the max power output (I guess).

The last pack came with a graph that shows what voltage and voltage drop to expect from the battery.

The 12 cell pack sets off at about 39 volt, so 36 cells (in whichever configuration) will yield about 117 Volt - about the max I'd subject the OEM pack to.

[RedDevil]

Originally Posted by sheepdog 44

What capacity do you want the booster pack to be? If you want it to be portable, like you take it out and charge it inside, it can't be very big or heavy. The stock pack i guess is at least 50-60 pounds. If you want to double the capacity you'd need lithium if you want to take it out regularly.

If not a regular 120 volt extension cord might be best plugged into a regular wall outlet both at home and at work.

Thanks, I keep forgetting to put down the essentials.
Your input is more than welcome

I'd want at least 1 kWh, which is doable with 10 Ah LiFePO4 cells which are typically just about 300 grams each, so a 36 cell pack could be as light as 11 kilograms.

In my 22 mile commute I can use about 1 kWh when it discharges at 2C (twice its hourly capacity), 2 kW. That should drop my fuel consumption by about 25%. If all works out as planned.
A larger battery could yield more, but I'm not sure the system would tackle that very well.
Cobb had a 2kW Enginer kit that worked well in his Insight, but problems arose after doubling its power, which is not proven to be the cause but can't rule it out.

We do have 230 Volt here, and 16 Amp fuses. Then, I would not even be bothered by an 8 hour charge time, so no issues there. I'd rather charge slow and safe than fast and reduce battery life.

The bottom line for this project is relative efficiency; improving my economy somewhat on the cheap without compromising boot space much, rather than maxing out no matter what the cost.
I can scale up later.

[MetroMPG]

Subscribing.

[planetaire]

Hi, Reddevil

Nice project.

I suppose in this post that you will grid charge only the lithium.
When this is done you will connect the lithium pack on the nimh.
Of course you will use a contactor, if not the connectors will be quickly destroyed.
When parralleling the 2 packs, you may have an important current.
It depend upon the voltage of the 2 packs and the sum of the 2 internal resistance.
It is a good idea to use summer internal resistances. They are the smallest possible then the amperage will be the maximum. Also using the smalest voltage for the nimh and the maximum for the lithium.

Then an other good idea is to check that the cells will accept this amperage. Nimh cells and lithium cells. In this situation lithium will be discharged and nimh charged. This just before driving.

Ninh sitting in the car will be cold in winter.
But lithium could be grid charged at room temperature or in the car, so being cold.

An other solution could be to grid charge the 2 packs. But end charge is not detected the same way.

[RedDevil]

Hi Planetaire, thanks!
Your awesome conversion is one of the main reasons I dare try this project.
Knowing it will come nowhere near yours in effectiveness and sophistication...

I was thinking about using this contactor: EV-Power | DC Power Contactor 100A, Coil 12V.

I may use a couple of them, to set up one circuit with a resistor to reduce the current when the voltage between both packs differs too much or the temp is low.
I could use one contactor to short the resistor when all is well, then the other to cut off all when the LiFePO4 pack hot or low on voltage.

Another point is, should I allow recharging the parallel battery on braking?
When the Insight recharges the main pack voltage can peak above 120 Volt.
When it has been pulled to an artificially high SOC by the parallel pack, it may not have enough capacity left to store the regenerated power.
Bleeding it off to the parallel pack may be a necessity; and that should be able to handle it, as this can only occur after it spent some of its energy already
(unless I'd put it in fully charged at the top of a mountain - but I would never do that).

Nevertheless, there again I'd need to take the max current the pack can take into account, maybe switch to the resistor circuit on high current either way?

I still need to find out what cables, collision breakers and current sensors to use. Safety is a must and a professional look to the project a bonus.
I don't want my dealership to refuse working on my car.

Tips on where to buy my batteries etc. are welcome!
I'd prefer EU based due to tax, transport and customs restrictions btw.

[planetaire]

Good questions.

Contactor. Theorically it don't have to handle HV. It is between two packs and for example may have only 48v. But I use a tyco ev100.
To choose one contactor there are 3 parameters: amperage, voltage and number of time it can handle this amperage. The more amp. the less number of on/off cycles.

Resistor
When connecting an electronic device with capacitors a resistor is a good design. Capacitor would give huge amp. This process take a few seconds because the capacitor don't store a lot of energy.

But it is not the same problem when paralleling cells.
If connected via a contactor named # 1 with a resistor, amperage will be reduced. This resistor will handle power during a long time until the Delta V become small enough. Then contactor #2 is powered.
The resistor could be hot.
In my Prius there is only one contactor. Max amperage is not too high. Both packs (Nimh and lifepo4) can handle this max amp. Amp being high, time during energy transfer is reduced.

Regen
When braking, before using lithium cells in my Prius voltage could be high, say 270v. After adding lithium cells it is not the same. Because both pack are //, internal resistances are also //. Very little delta V in summer, more in winter of course.

Cells
You have to know the max amp your actual nimh pack have to handle in charging/decharging mode. The max and min voltage.

If your lithium cells don't accep the max regen, using a dc-dc converter is a good way. Efficiency can be high.

Current sensor Hall sensor are interresting. For example allegro one...