Planing CanView and BMS+ conversion with lithium

It is normally done with up to extra 3 OEM Prius NiMH HV packs in parallel from other Prius's from the wrecker's yard. As far as I am aware nobody has tried using lithium battery packs in parallel. You would have to ask norm. The problem with using lithium is that the cells need to have a very high charging limit 15C as up to 120 amps can be pushed into the lithium battery pack during regenerative braking. NiMH can take the high charging current. The Prius battery ECU may have a problem with Lithium and throw DTCs. You could ask pEEF for advice as he has done something similar without using BMSplus.

 

Hello, Mr-plugin.

I have been using for one-two month bms+ and lithium cells in // with stock nimh and have a 2007 prius.

It works very fine now. Never got some dtc.

More informations here

Short description:

70 cells A123 20Ah each, serialy connected.
This pack is subdivided in 5, each 14 cells easily removable. => 4,55kWh
Total weight only 41kg (90 lbs).

Some pictures before connecting bms+



Only the lithium cells are grid charged. Just limiting end charge voltage near 3v5.
These cells are connected in // with the nimh only when driving, even when they are "depleted". So there are contactors (and fuse of course) between lithium and nimh.

Add of course a high voltage bms, bms+ and driving pleasure.

It is then possible to drive in 100% EV for more than 40km (25 miles) with an average speed of 42 km/h (26 mph). Energy usable is more than 4kWh.
Maximum speed in 100% Ev is 90 km/h ( 56mph).

Maximum electrical power:
-under 45 km/h (28 mph) 20-28kW.
-over 14 kW.

Engine can be used when you want. Just press accelerator pedal more.

This additional equipment can be totally removed.

I enjoy it

I agree with lopezjm2001. Only use lithium cell that can accept at least 100A regen for a few seconds.

 

That's great! Couple of questions:

1. What is the charge rating for your prismatic pouch a123 cells. They appear to be made in Korea. I see they have a discharge rating of 3C. Selling on EBay.

2. What are you using for a BMS to balance your cells.

Thanks.

 

Hello, lopezjm2001

1) You have A123 20AH datasheet here

So during 10sec 1kW per cell. Total 70kW, more then necessary.
This would be more then a hard braking. I never see more then 25kW.
I don't really use more then 60-70A when braking.

2) I use a modified version of peter perkins bms with 0,3A balancing amperage.

 

The A123 pouch cell data sheet is very vague. It is possible that the A123 cell is capable of a charge rate of 4C for a few seconds during regen braking although it will probably decrease the cycle life of the cell. Maximum battery life is achieved with a charge rate of 1C.

I noticed that your 5 x A123 cell boxes are made of PVC. I would have chosen metal boxes to help eliminate the chance of ignitability and flame propagation. Although PVC boxes are lighter and the clear lid is great to be able to see the BMS board without opening the box and the box is a lot lighter and is easier to remove. The other advantage of a metal box is that in the unlikely chance the cells are overcharged the metal box goes a long way to stop the pouch cells from expanding like a balloon and bursting the bag of the cell and leaking battery fluid into the box. Do not get me wrong I still think you did a great job. I guess you must have added up the advantages and disadvantage between using metal or PVC.

Just wanted to know what you are using For a 230Vdc charger?

Did you build your own Peter Perkins BMS board or did you buy it?

Thanks,

John

 

Hi Plugin,

You can use two contactors to engage the battery. The first contactor will put in a high power 10 ohm resistor in series with the battery to limit inrush current and arcing. Then the second contactor will bridge out the resistor. Use the 230 volt contact output to energize the 240Vdc Coil of the second contactor. I use this system to reduce inrush current and arcing in a high frequency generator 120MHz to seal plastic. It is simple and effective. It dramatically increases the number of cycles the contactor can energize before a contact is blown or welded together and thus increases the contactor's operating life.

 

Ok. Before you enagage the contectors what are the possible battery voltages of your NiMH and lithium pack. The NIMH could be as high as 240v at 80% SoC and the lithium could be as high as 70 x 3.35 = 234.5 volts. So inrush current could flow in either direction as current always flows from a higher voltage to a lower voltage. During EV mode the NiMH battery could be as low as 180 Vdc. Do the calculations. The worst case scenario is that if the resistor is underrated it will burn out and develop a open circuit.

 

Actually, the regen capacity is shown on power graph, for 10 seconds at 85% charge, the battery can handle 900 watts, or about 250 amps. The key thing is to monitor battery temperature, and if it gets too high stop the regen charging.

 

It should be stated and be clear to anyone attempting this project that

240Vdc can kill you

 

Minor detail, how ever a VERY important one!
Eating toast is better than being TOAST...

 

You can use a Canview relay to do this. My Canview V4 has five relays which I can use. One controls a HV battery fan mod to keep the NiMH cooled as possible. I could also use a Canview relay to engage a lithium battery pack.

If you ever make the mistake of doing regen braking down a long mountainous pass you run the risk of overcharging your Lithium pack if you not have any safeties installed to disengage the lithium battery pack. I remember reading about somebody who had a second NiHM battery pack without cooling and the regen braking seriously damaged the NiMH battery pack as he was going down a very long mountain pass. He could have been doing regen braking of 90 amps for as long as 20 minutes continuously. This is well above the lithium pack specs charging limit. This much overcharging could possibly lead to the lithium pack cells bursting open and leaking battery fluid.

 

I first want insulation (high voltage inside ) and to be able to have a look inside without opening boxes.
But metal box would be fine also because emf.



Temperature (ordinary not during a fire ...) was one of the unknown points.
But after several hours driving, nimh stays colder than without lithium and I never saw lithium over 30°C.

I made it, I bought pcb.

BUT please note that it is the most difficult part of this project.
This is because this bms is connected to lithum and then to the nimh battery, HV voltage is floating relatively to the car body. And secondly the boost converter generates high "spikes" that the bms has to handle.

Note that data transmission needs a very efficient insulation. Optocouplers is not enough at all.
I use bluetooth in order to send the 70 voltage values to my PC during driving.

This was one of the main questions before doing this plug-in.
Will I have to connect first a resistor before main contactor, like toyota does with nimh ?

In practice , it is not necessary. For exemple last time nimh voltage was 218v, lithium 240v and max amperage was 35A. Nimh was cold (11°C) and lithium near 19°C.
Theorically it can be 60-70A. It fallsl very quickly.

Note that nimh voltage doesn't go under about 215v. I set Bms+ to end-voltage = 210v. With this voltage lithium is "depleted" then no need going under.
This voltage goes up after driving between 218 and 225v.

Lithium end voltage after charging is 245v and falls near 240v.

Then no need for me to add a second contactor with a resistor.

Now I use a low voltage charging after disconnecting 5 packs.
But I will use a HV charger later.

Hope this could help

 

Please contact Norman about this question.
What I saw is that bms+ reduce ccl when voltage goes over, i think, 240-245v
So When lithium is fully charged, if cells stay well balanced, regen will be canceled.

 

Hi Plugin,

You probably have already thought of reconfiguring your Enginer battery pack. The RFE F20 pouch cells have a max discharge of 40 amps see data sheet at

http://www.enginer.us/f/index.php?action=dlattach;topic=1273.0;attach=12701

You would still need to buy 6 extra pouch cells from RFE to make up 230 volts. The 4kwh kit uses 4 x 16 = 64 cells.

You can electrically split up the Enginer pack into five banks using Anderson plugs. Connect all banks in parallel for charging and you can still use your Enginer charger. After charging you just reconnect all 4 banks anderson plugs in series to give 230 volts. Each bank would draw 15 amps / 5 = 3 amps. This is well below the recom. charge rating for the F20 cell of 0.5C = 10 amps.

Norm has already written a special BMSplus code for 2 enginer kits which can be downloaded from his website. The code limits the electric motor current draw to 40 amps maximum. You would need to purchase a device from Digikey to download the code into the BMSplus. I have already downloaded the special code into my BMSplus and it works.

Anyhow you could consider this as an option.

 

I do not think that the RFE F20 cells are not dependable. It is the way that they have been put together and the BMS16D that has made the F20 cells look bad in my opinion. Their power to weight and volume ratio makes them a good contender.

Hills are a problem. I try to sustain stealth mode going up hill for as long as possible using my BMSplus which sometimes I can make it to the top of the hill if I decelerate slowly rather than causing the ICE to start. The Canview has a bar graph on the LHS of screen which gives me an indication of how close I am to causing the ICE to start.

Since I started using BMSplus I have concluded I am better off not using EV mode. The high current draw just depletes too much too quickly. So the NiMH battery pack would probably not like high current draws and would probably shorten the NIMH battery life. I have EV mode setup so that it only comes on automatically at start up using a canview relay. I did this by setting the ICE temp condition to 120 deg. Celcius. The ICE normally never reaches 120 deg. Celcius so EV never operates automatically during my trip except at start up.

 

Has anybody found a supplier of A123 prismatic pouch cells AMP20M1HD-A?

The ones on Ebay appear to be a clone. Doing a Google search showed that the sales distribution of these cells are very limited to car makers.

The A123 website displays the following:

Please be aware that A123 is focused on high volume commercial applications and does not supply battery cells or systems for hobbyists and custom vehicle conversions