Balance at the cell low voltage limit

This is a little bit of topic but it needs some explanations and answers.
Many years ago, in my first Prius PHEV conversion I was using a Manzanita Micro PFC-40HM as my main DC-DC converter, powered by AGM PbA.
At hat time, it was pushing more than the rated 40Amps. With an accurately constant voltage and current settings, after proper tweaking, my 2004 Prius never "throw" error CAN codes.
I think that your source of information or lack of, is unbelievable wrong.
Also, I can't understand how a 3K and 5K DC-DC Enginer converter are also as good, witch one is the crappy one? , the derated 3K or the oversized 5K.

 

I really need to talk to Jack about trading my two converters for the new 5000 watt converter. I am having no issues at all with 23A going into the system for 40 mile drives.

 

There are NOT older PHEV conversion systems, only Pioneer ones


I used no spoofing at all in my conversion; that was part of the CalCars type of principle of operation and perfected by Andrew Ewart's electronics circuit in an open source project.
The CalCars conversions were based on mixing a DC power source made out of PbA at the beginning and changed by LiPoFe4 later; through their spoofing board.
My fully EV operation was set then at my DC-DC converter at 237.50 volts and backed by 47 Amps DC with out any sags.
You can buy today the same piece of equipment I use for a modicum price of $3,400.00 at various EV retailers; this is serious piece of equipment.

 

Guys, please do not blast me for putting this post on this thread. I purchased a 2 kw Enginer kit from Jack last year. After many fustrating moments trying to get it to work I finally did about two months ago. Two weeks ago one of the balancers started to beep. The batteries will not get a full charge. I am tired of this system. If anyone is interested in buying it from let me know. I live in Houston and it is currently installed in my car. I have removed the lithium batteries and will go with the kit. I am asking 600.00 if anyone is interested. My number is 832-860-9370. The converter is working and the charger works as well. It seams the batteries have failed. I talked to Jack and he asked me to get a reading on indivisual cells. I don't want to mess with this system anymore. I am tired! Everything that I got in the kit when I bought will go with it. I will not ship it. You must come to Houston to pick up. Sorry i will not hold it either.

 

Dan, Thank you. I have delt with them before. Do not let the name Houston Electric fool you. The owner is rude and has no Earthly idea how these systems work. He hires a guy who built a three wheeled electric motorcycle. to do his work. This company buys cheap electric cars from china and resells them at a profit. I am just tired of messing with this system. Jack has been helpful in the past. After four converters and almost a year, I am ready to hang it up. I am happy with my 45-50mpg.

 

Yeah, my 2010 can handle the 20+amps that the converters throw. I normally find Mr. Big's posts a bit rough, but to be honest he's accurate about how... variable these converters are. I like them, and they serve the purpose, but there is better out there... for a price. I'm happy with the 5k converter. I just had a 3k converter go bad on me, and I am going to return it. The two converters seemed to loose a bit too much energy in the conversion ... (heat?) I don't know. I think my current problem is most likely balancing the batteries. It all still works, but I want to get the MAXIMUM performance out of it.

Unfortunately I am too lazy to mess with the cell logs.. (for now.) I would really like to wait for some new balancers that are rumored to be around the corner. (wink) Those are supposedly going to send power from one cell to the other instead of just draining. In the meantime, I think I am going to try to get all the cells balanced on the low end, and then unplug the db8's and then charge/discharge. I will be sure to plug them in before I charge for a few hours and make sure it's WELL balanced.

I might do more, if I feel I need to after talking to Dan. After reading these 11 pages, I'm not so sure I want to put that much into it. Especially if the benefit is marginal!

I also want to say, according to the scangauge the 2010 already charges and discharges at a higher amperage than the gen2. SO, I have seen very high charge and discharge rates during driving. WITHOUT the packs running I have seen a maximum of 120amps during acceleration, and about the same regenerating, however it is much more rare. That said, during running the packs, and putting in an extra 20A, I have NEVER seen a code. I could have cranked up the 5,000w converter, and the 3,000w converter was already turned up to where it could be thermodynamically, but now the 3,000w converter is down. I don't plan on replacing it, so I will never know exactly how much can be thrown at it before throwing a code. I would be worried that at that point there might be danger of blowing a battery fuse.

I have read elsewhere that the gen2 had a 150amp dc fuse at the removable hybrid plug. I haven't inspected the plug on my 2010, but I assume it's similar. This may be something completely unrelated. I am not claiming to be an expert on any of this, just describing the numbers I have seen, and an idea about the limit on the 2010 being fuse related, and not hardware-component related. This car doesn't seem to code under any condition, but I would be wary of exceeding 150amps as that fuse is like 80-160$ depending on the dealer you talk to. (Most have never heard of the fuse.)

-brad_rules_man (Brad) *accidentally posted with wrong account, but I'm subbed to this thread on both accounts anyway*

 

I think I need to "tweak" up the output voltage of my converter a bit as I can never get into the green 7th bar on the stock pack while sitting still. It may be that each OEM pack is a little different thus requiring each converter to match. My open circuit converter voltage is presently at 245vdc.

It also seems that the Prius computer also utilizes more electrical energy when the stock pack is in the green zone, as it wants to bleep off the excess energy.

Pb

 

Mr. Big,

Do you know of a better cell balancer, or a cell log/alarm? I am only wondering because you seem to be involved in a greater EV club, and knew about the kick-a@@ converter! I know I have looked online, and been told or read that there really isn't at this time.

 

Hi Brad,

Really the next step up would be a full fledged BMS that can monitor all the cells at once and balance them accordingly (and allow for inter-balancing between all cells instead of 8 cells at a time). This may be overkill for Enginer style system however since such a BMS can easily cost upwards of $600 for 16 cells...

If you are willing to spend that much, there are some new BMS units coming to the market that would work well, but again they are more expensive than the DB8's you're currently using. Otherwise, my guess is that you're probably best off using the cell-log system detailed here.

Andrew

 

My choice of BMS at a professional level, and the only one I will do, is a product named Lithiumateâ„¢ - Distributed Li-Ion BMS by Elithion, top notch at an affordable price. Not an RC expensive toy market item.
This product is aimed to the EV'er for LiPOFe4 chemistry like the Enginer is actually using.

 

Ok, thanks for the replies, I really appreciate it. I am going to need time to mentally process this video, but I want you guys to watch it if you can. It's a full-on episode, it's kind of lengthy but if you can sit through it he gets into some very good points. (What I am referring to is balancing cells that are at different capacities.) It can apparently be very tricky as no two cells are alike. Here is the link: http://media.ev-tv.me/news111309-1280.mov (Hope that works.)

The part I am mostly describing is where he uses redwood stick to demonstrate. It is about 2/3's of the way through.

 

Of course... this is basically what you guys have been saying all a long. Balance at the bottom if anything at all! Balancing at the top can murder cells. This guy makes it easy for dummies like me. haha. I can't wait to learn more.

 

While I don't agree with the philosophy of always bottom balancing or that proper balancing damages cells (and I use the word proper), bottom balancing / no balancing may be preferable for the Enginer style system due to its unique setup. In an ideal world you would want the balancers to be able to communicate with each other and with the charger such that the charger can be throttled according to the remaining charge needed (the fancy pants BMS units can do this). That said, improper balancing /can/ as you put it--"murder" cells, yes. Improper balancing can result from a whole host of problems.

A close second would be getting the cells in relative balance (top or bottom--if bottom works better then by all means) and just letting them go. Eventually they will unbalance themselves due to any number of reasons, but you'll get quite a few cycles out of them before that happens.

Anyway, all that to say you may not actually need to balance your cells in the Enginer setup, but I wouldn't take that as an indicator that cell balancing is inherently bad or that it automatically damages your cells (I've had several lithium setups where balancing has worked quite nicely and made a significant difference). The idea is to maximize and uniformalize (is that a word?) depth of discharge so that all batteries see roughly equal wear and tear and you as the consumer get the most out of the pack.

Andrew

 

True. I'm actually .. almost giddy waiting for these new balancers. 16 cell, which would only need one.. supposedly can take from one cell and dump to any other instead of shunting it on to the next, OR discharging the higher cells by means of basically heat.

I also have something else disturbing going on, but I will know more when I open it up tomorrow. Tonight I washed my car, and afterwards I thought I would turn on the balancers to make sure the cells were ok. I had a problem with the converter that was in that pack, so I hadn't been using it. Well, the DB8 would only detect voltage from 3 cells. I even tried plugging the other DB8 in to make sure it wasn't the balancer. Now I'm going to be slightly worried until tomorrow when I pull the cells and start testing. /sigh

 

This can also happen if one of the cells (in tis case buddy cells) drops too low. The balancer will stop reading anything beyond that set.

 

I would second to check the wire harness. I had used the DB8 wiring for the CellLog and one set start to go flaky. It took me awhile to find it, as the CellLog voltages were starting to act weird, especially when it gets warm. I finally checked with a voltmeter and determined that the some wires in the harness were making intermittent open circuit. Since the wires are all shrink wrapped at the terminal, i couldn't see the bad connection visually. With a poor connection, it would trip the cellLog voltage reading to sounded the alerm. Needless to say, the siren scared the jibber out of me.