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Discussion Starter · #1 · (Edited)
Can the ageing ZF2 OEM Lithium pack capacity be increased/augmented with buddy/parallel packs?

I have acquired another OEM lithium pack to tinker with and have been thinking about how we can increase the capacity of the ageing Lithium cars.
We also have manual IMA control (IMAC&C) so if we can increase the battery capacity you could command much more assist etc to significantly improve mpg.

Basically use more electricity instead of petrol $$. (y)
Might be good if you have solar panels on the house to charge the pack for free.

The OEM Lithium battery is very small and as they age the useable capacity is going down relentlessly.
They can't be recovered or rejuvenated only replaced or perhaps (buddied) which is the idea of this thread.

During my earlier research I found that the Lithium battery capacity and SOC seemed to be directly related to the reported cell voltages and pack balance.
If we could buddy/parallel another pack with the OEM one then the voltages would obviously not change as much and endurance/capacity would be increased.

I def think the car would accept a buddy pack that restores the capacity to new OEM levels, say 75%.
So two weak packs say 37.5% would get you back to new 75% OEM level.

There are lots of potential gotchas and variations in this idea.

1) Does the car count current and cross check that with the pack voltages/duration etc?

2) Is the battery current sensor in the right place to allow charging when the car is on but regen is not being commanded?

3) Where do you safely put/mount a buddy pack? How do you monitor and control it?

4) Could you buddy a suitable voltage cheap used Nimh pack with the ageing OEM Lithium?
The advantage of this is that Nimh is cheap and plentiful in various pack/cell configurations from many cars.
It's also easy and safe to grid charge Nimh without much fancy monitoring.

Hmmm?????? Food for thought..
 

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Discussion Starter · #2 · (Edited)
Just looking at my pack on the bench and we do have access to the required battery connections without having to take it out of the car! (y)
It also bypasses the current sensor. So we could theoretically feed power into the OEM pack with the car on without the car detecting it via current sensing and throwing a fault.


I'll use one of my OBDIIC&C gadgets to monitor the OEM cell voltages and I can disconnect the buddy pack if things get out of balance.
I have loads of contactors and fuses kicking about!
 

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Discussion Starter · #3 ·
I have a 3kw Zivan NG3 charger kicking about hmm.

That will probably run with a 200-300V or so DC input and it has the right output voltage for the OEM Lithium pack.

I could bypass the NG3 input noise filtering and AC bridge rectifier to feed my buddy pack DC directly into the NG3 filter caps.
Might need a precharge resistor for the inrush current.

If I'm clever with a changeover setup I could use the same NG3 to charge the Buddy pack from the mains when back at base.
 

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Discussion Starter · #5 · (Edited)
Someone on YT asked about doing the buddy pack idea with an earlier ZF1 Nimh based CR-Z, so a couple of random thoughts on that..

1) You can't easily access the required Nimh battery negative terminal and avoid the current sensor without pulling the pack. (n)

2) The Nimh car does count current so that will be a hindrance with a big buddy pack that never runs out.
I have got round this before by using my OBDII device to autoreset the SOC to 75% forever until the buddy pack is exhausted.
That way you get very eager strong assist, no background regen, but still get regen on the overrun and when braking.

3) Nimh does not like being in a basic parallel configuration with other Nimh packs of the same voltage. You can't simply clag on another CR-Z Nimh pack.
You need monitoring and disconnects or one can discharge into the other uncontrollably causing a meltdown.

4) I don't have a ZF1 Nimh car so won't be physically testing/evaluating it.
However it's all been done before by me on other IMA Nimh Cars, G1 Insight, HCH1 Civic, HCH2 Civic etc
So it's all well understood and documented on various forums. Lithium Buddy into Nimh OEM being popular.
 

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Discussion Starter · #7 · (Edited)
Hmm. Seems to work so far. (y)

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Installed the Anderson connector and plugged in my NG3 mains charger and the pack charged quite happily from the mains.
Turning on the ignition did not throw any faults as the car does not see the current. :)
SOC ticked up nicely to full! 80% All promising for a buddy pack.

Note the feeble 42% useable capacity of my OEM pack!! (n)

What we might see hopefully with a buddy pack is the useable capacity % start to go back up...


I will try and throw an LTO Lithium or Nimh buddy pack into the boot/trunk this weekend for some quick and dirty testing.
For a direct connection I will have to match the pack voltages before connecting them.
Once connected they should stay in line with each other.

So this brings us onto where can we fit a buddy pack?

If you take out the big boot foam piece you have quite a bit of space above the OEM battery and under the deck.
That looks like the ideal place and you could fit quite a reasonable capacity bespoke pack into that area.
Need to do some tinkering/offering up/fabrication....
 

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Discussion Starter · #8 · (Edited)
So discharged the OEM Lithium pack on my drive around to 20% and the assist disable point. ~3.20V per cell
Plugged it in and charged back up at home using the mains no issues. (y)

20-80% SOC took a laughably short ten minutes :LOL: at 2kw grid draw and 12A charge rate.
Total electricity consumption was about 0.35kwh to charge from flat to full and charger cut off at ~4.00V per cell.

If we assume about 90% mains to battery charge efficiency then we get about 300wh into the pack between 20-80%.
A standard car would not be able to discharge to the levels I did with the manual control so the useable power would be quite a bit lower say 200wh.

The capacity of the OEM pack really is very feeble. It desperately needs a buddy!
That's this weekends project. ;)

3 x LTO 1.1kwh blocks to give ~3000wh or ten times my current capacity!!

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100mpg here we come.. :p

Edit. Also charged up the scrapyard OEM Lithium pack with the mains charger after checking cells with OBDIIC&C.
It has 52% useable capacity. All nicely balanced and back in cool storage now.

So if anyone in the UK/EU needs either a Nimh or Lithium OEM pack I have a good one of each available.
 

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So discharged the OEM pack on my drive to 20% and the assist disable point. ~3.20V per cell
Plugged it in and charged back up using the mains no issues. (y)

20-80% SOC took a laughably short ten minutes :LOL: at 2kw grid draw and 12A charge rate.
Total electricity consumption was about 0.35kwh to charge from flat to full and charger cut off at ~4.00V per cell.

If we assume about 90% mains to battery charge efficiency then we get about 300wh into the pack between 20-80%.
A standard car would not be able to discharge to the levels I did with the manual control so the useable power would be quite a bit lower say 200wh.

The capacity of the OEM pack really is very feeble. It desperately needs a buddy!
That's this weekends project. ;)

3 x LTO 1.1kwh blocks to give ~3000wh or ten times my current capacity!!

View attachment 68263

100mpg here we come.. :p

Edit. Also charged up the scrapyard pack with the mains charger after checking cells with OBDIIC&C.
It has 52% useable capacity. All nicely balanced and back in cool storage now.

So if anyone in the UK/EU needs either a Nimh or Lithium OEM pack I have a good one of each available.
I love this!, I was thinking about this on my drive home today.

I drive up and down the full length of I97 + a few miles here in MD as my work commute. That is about 20miles each way. People here in MD will run you off the road if you drive the speed limit, I typically was drive at 68 ~ 70 MPH, I sit at about 43 MPG for that drive.

If I could boost the that up to 50+ I would be a very happy camper. have a small ish pack I can take in and out of the car, charge up, would be a dream. Mounting it all in a Pelican / hard case. If I need the extra space just unplug it and leave it at home.

I love to see where this is going.
 

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Discussion Starter · #10 · (Edited)
I love to see where this is going.
Bear in mind batteries don't contain much energy/kg and with a power hungry CVT and higher road speed your results will be worse than my manual car.
Can you (borrow/abstract electricity) charge at work?

To get the most boost for your electron everything has to be perfect. Lower speed, less drag, engine in good state of tune, decent fuel.
Super A+ rated rolling resistance tyres might make as much mpg difference as a small buddy battery pack and be cheaper.

All that said eeking out the power in a small PHEV pack can be fun.

This is a ten year old video of my PHEV Insight which had a 20Ah pack.
Filmed on a shaky 1 pixel potato but you get the idea.

 

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Discussion Starter · #11 ·
I've built a very rough and ready buddy pack from some old LTO cells and faulty blocks I had kicking around.
I have it fully charged at about 166V which is 4.15V per cell for the Honda pack.
I bypassed 4 dead cells which was a bonus as that dropped the pack voltage down to where we need to be.

I need to get the Honda pack to within about a volt then I can simply connect them together and they will operate as one.
Then the testing can being properly.

Remember this is only proof of concept! The buddy pack I have thrown together is not what I would recommend.
It's heavy and old, at least twice as heavy/bulky as a pack of new cells of the same sort of capacity.

But LTO is rugged and tolerant, this is all about seeing what extra capacity or fudging the car will accept.
 

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Discussion Starter · #12 · (Edited)
Well that worked very well without drama!!

The approx ~3kwh buddy pack has a 125A fuse and breaker switch from a defunct Nimh CR-Z pack at the back left in the picture below.

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Controlling the IMA using my slider pot IMAC&C device I was able to use the 10 x extra capacity and trundle around the Hull outer suburbs for half an hour at well over 100mpg. (UK)

With the initial pack voltage I had the car SOC held at 80% (so no regen) for several minutes before it dropped enough to allow braking/overrun regen.
Normal assist of course was very lively but commanding it even more with the pot really helped these numbers.

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The car did not seem to get upset about the extra capacity and my 'useable capacity' has now gone from 42-57% on this one short test drive.
I suspect that might increase further after some more drives.

As the buddy pack voltage slowly decreased under load the car SOC % would tick down but then when the load was removed it would tick back up again!
Early days but looks very positive and you could have quite a big/light pack in the back and a grid charger pseudo PHEV capability.

You can't run on just electric but you can push mpg very high.
The trick is to use just enough fuel/throttle to get/keep the engine up to temperature and avoid the pumping loses if the engine isnt running.
On the open road at higher speeds the IMA power makes less difference but it would still be beneficial.

I don't know how much capacity I have used at the moment but I will charge up the pack in the morning when it is a bit cooler and note the Kwh consumed.

You do need an OBDIIC&C or equivalent to make sure things don't get out of hand with the OEM pack and you will need some means of monitoring your buddy pack.

Good points.

I didn't need/use any sort of fancy buck converter. :)
You can just add a parallel Lithium pack of the correct voltage range but with masses of capacity.
Simple to install. (y)
Addictive mpg.... :p

Bad Points.

Not sure yet.


Tomorrow.

Secure pack using the boot tie down points under the little flip up flaps.
Add charging port so the charger charges both packs simultaneously.
Investigate behind bumper to see if I can do a flip up number plate mains socket inlet.
 

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Discussion Starter · #14 · (Edited)
I added a splitter connector so I can charge both packs combined and it took approx ~1.9kwh to charge after yesterday's test.


Lash the packs down then off for longer test drives shortly.

Two tests today.

1) No use of IMA manual control. Just see how the car reacts/performs.

Recharge then....

2) Use IMA control to see the difference from above.
 

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Discussion Starter · #15 · (Edited)
Test 1 Report. (No IMA Manual Control)

Ambient temp 30C, Wind light. Traffic moderate.
Pack voltage 164V. 80% indicated SOC at start. (Both packs full)
55 miles no manual IMA control = 77.8mpg (UK)
1.7kwh consumed to recharge on return.

Note this was varied terrain, some town, some A road, some B road and some reasonable hills around the Yorkshire Wolds.
Sitting at a steady 50mph on a flat motorway would likely have given a significantly higher figure.

The car would not allow regen for the first 30 miles as the pack voltage was too high and the SOC was pegged at 80%.
This means I missed a couple of early opportunities descending hills to recover a little energy. (That maybe cost me 1-2mpg)
However it also means the car assisted at about 2kw with even the lightest throttle touch and it was a good way of eeking out the power available.

Eventually after about 30 miles the pack voltage fell and SOC began to drift down below 80% and regen became available.
It never fell below 65% so there was never any background charging going on which starts at about 60% SOC IIRC.
But I now had regen braking and on the overrun.

So a buddy pack can work quite happily without IMA manual control and you would get a reasonable mpg increase.
I would say +10mpg minimum in normal driving for an average driver.

But of course if you are a sympathetic economy driver and can command IMA at will you can make much better use of the power available. :eek:

The sweet spot is about 75% SOC which equates to about 3.8V per cell or a pack voltage of ~152V.
If you can hold the SOC/Voltage at that point you get eager assist and regen on demand.

So how do you hold the voltage/SOC at that point?

1) You have a big (Ah) capacity buddy pack that will naturally stay nearer the sweet spot for longer. (Mine is 20ah about 3kwh)
2) You fake the BMS board voltages on the IMA CAN bus and tell the car the pack is always at 152V.
3) You remove the OEM cells and install a massive capacity LiPo pack but use the OEM BMS boards to monitor it.

The fact my test pack voltage is a bit high is not a massive problem and it help us explore the outliers.
The chemistry of my LTO buddy cells is different to the LiPo OEM ones so we don't get a perfect match.
If you used 40 massive LiPo cells you would have a perfect buddy. (Of course you would have to monitor them unless you use the OEM BMS boards)

I might try a buddy Nimh pack to see how they fare.
I have hundreds of useable Nimh sticks and making something to fit in the trunk might be amusing.
 

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Discussion Starter · #16 · (Edited)
I do a regular urban commute to the gym about 6 miles away and managed over 100 mpg (UK) today return trip (12 miles) with use of IMA manual control and the buddy pack.
This was starting from cold. I will charge up again tonight when it's cooler to ascertain electricity usage. Probably a couple of Kwh.

Edit: It was 1.8kwh.
 

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Discussion Starter · #17 ·
The average UK price per kwh for electricity is about 30p, now so lets call that 50p (60c US) worth to boost my normal 60 mpg to 100 mpg over 12 miles.
I have the benefit of a 4kw solar array on the roof, so If I time it right and charge when the sun is out it doesn't cost me anything. (y)

I have managed to snag another Zivan NG3 mains charger so if anyone in the UK with a Lithium car is interested in having a go at this mod I might be able to assist.
 

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Today I did a little experiment, Took the Highway again to work, but I decided to actually do the speed limit (I know crazy idea). I had a lot of people flashing high-beams and passing me with some rather choice hand jesters. Gotta love Del-Mar-Va drivers.

But the on screen calculator read 47.8 MPG when I pulled into the parking lot. I was going to try taking the surface roads tomorrow. However I just took a new job, it will be a lot closer to home, with both a slower highway (55 MPH vs 65 MPH) and surface road option for the commute. So I'm not too pressed about trying to optimize that route any more.

New job will let me plug in stuff to charge in the office, so after I get settled there I would love to build up a pack to do some testing. It will be nice not driving sometimes 200+ miles a day in a branded van that make more noise then I can drown out with the radio.
 

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Discussion Starter · #19 · (Edited)
I did a tougher route today (Hull - Scarborough) and around 100 miles (50 each way) with a lot of up/down.
I managed 78 mpg overall, that's probably about 20mpg better than I would have done without the pack and manual IMA control.
The pack was low by the time I had finished the outward journey and I could not recharge at my destination.
So the journey back had less assist available but loads of room for regen.

One good thing about the directly connected 20ah buddy pack is....
Once regen is available it can absorb the energy from descending a long hill without maxing out the battery and having to resort to the brakes.

I need to add some more functionality to my IMAC&C now to enable/disable background charge etc at the touch of a button.
Need to smooth out the ramp up/down at the null point on the slider.
 

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I'm going to need one of these buddy packs if/when they become available. I'm lucky if I can get 300 miles out of a tank mostly highway driving. That equates to almost 30 MPG (US). Still not terrible but I'd like to get closer to the EPA numbers which is about 37 MPG highway. Most of my poor MPG is attributed to the SC and the current tune I'm running. My usual daily commutes I'm hitting 250 miles when the low fuel warning comes on.
 
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