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retepsnikrep Senior Member Joined: 31/12/2007 Location: United KingdomPosts: 131
Posted: 05:05pm 23 Sep 2008
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Sorry I haven't been active on the forum since I built my Savonius some months ago. Suffice to say I've been busy with a big Pic project for the management of Lithium Ion cells in my Hybrid Vehicle.
Lot's of rambling by me but in the last few pages we are getting there. Anyway no reason why the system could not be adapted for a home battery bank for our homegrown power. Just for your info and interest. Edited by retepsnikrep 2008-09-25Gen1 Honda Insights.
grub Senior Member Joined: 27/11/2007 Location: AustraliaPosts: 169
Posted: 09:30pm 23 Sep 2008
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A slight glitch in your address, there is no space between the 1 & 2 (1 245=1245)
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 10:13pm 23 Sep 2008
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Hi Peter,
This type of cell balancing[voltage limiting] only performs a limited job, if every cell in the pack has the opportunity to be fully charged. A better system I developed for NiCd packs and Pb-acid and that is being trialed on LiPo cells performs cell voltage balancing on cells no matter what the pack voltage and works during charging and discharging, and while the pack is idle. The current consumption is only several mA from a pack and only if cells are unbalanced. The voltage and current limited charging is still controlled by a single charger only. My system will work in conjunction with existing BMS.
Gordon.
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retepsnikrep Senior Member Joined: 31/12/2007 Location: United KingdomPosts: 131
Posted: 05:20am 24 Sep 2008
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Gordon
Please let us have the full details and specs.
Thanks
Peter Gen1 Honda Insights.
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 11:13am 24 Sep 2008
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Hi peter,
I am sorry I cannot hear you.
Gordon.
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retepsnikrep Senior Member Joined: 31/12/2007 Location: United KingdomPosts: 131
Posted: 04:21am 25 Sep 2008
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? I'm confused. Gen1 Honda Insights.
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 08:58am 05 Oct 2008
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Hi Peter,
As I said above, the units are currently being trialed prior to commercial negotiations. If all goes well. you may eventually be able to buy one, and before anyone criticises my comment, this cct has been in development a long time before LiPo batteries and more than 10 years before I knew of 'thebackshed'. Any disclosure on a public forum would jeopardise exclusivity to a commercial outcome, so I cannot release any details. There are other alternatives that claim to cell balance. Most others are basically equivalent to a series of voltage limiting zeners across the cells with some control and indicator logic.
I suggest you continue with your own design.
Gordon.
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 08:29am 09 Oct 2008
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Hi peter,
If you have read the report from trev, in his diary, then you have some idea of what my equalising cct does. I had told trev, that he could expect the equalising process to take up to 10 cycles for a 90Ah battery. It seems this was a bit of an over estimate.
It was good to see the progress with charging and discharging time, results. I expect the imbalance will continue to decrease with more charging cycles.
I am looking at a possible short production run with a new pcb layout, as a demonstration model. You are on the other side of the world, so it may be some time yet before commercial units are available there. The final commercial version may end up as an IC, in a std leaded package. Costings will ultimately determine the final outcome. I have not been able to replicate my design with normal leaded components. I have had to use the tiny SMD package components only. The cct looks a bit like one from a micro HDD. The specks are pretty hard to solder. A leaded pckege may be a way out.
Gordon.
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mrbigh Newbie Joined: 12/10/2008 Location: United StatesPosts: 1
Posted: 02:21am 12 Oct 2008
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I would like to be part of your future equalizer product test/purchase list. My application will be for NiMH 7.2 VDC Panasonic prismatic modules, 202 VDC strings.
Horacio
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 06:59am 12 Oct 2008
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Hi mrbigh,
I have to say that 1.2V cells are possible, but a pretty expensive option. My testing is to cater for critics.
You would require probably 70 or more modules. This would be many thousands of $. There is no point in equalizing blocks of batteries unless the individual cells are equalized to.
Gordon.
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 04:54am 23 Oct 2008
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I believe there is a chip made by Intersil, [ISL9208], that performs a function I have described above with cell voltage limiting. This chip requires up to 1W power resistors that are placed across each cell. They use a complicated microcontroller algorithm. My cct design is nothing like this device.
The initial testing of my cct design is a complete success. The next test will be a connection to a battery that is starting to lose capacity with a normal BMS. It is expected that the capacity will be recovered. I am still awaiting components from the UK, to complete the new test units. I am negotiating a commercial arrangement. A limited production run will be the next step. A typical EV will require multiple cct's. The most economic arrangement seems to be blocks of 4 cells. These units can be combined to any number of cells.
Ideally the design should be integrated into a chip package. A 4cell unit could end up a 10pin device, that includes an LED indicator output. Will have to wait for talks with a manufacturer.
Will be a bit more time before final EV pack testing is complete.
Gordon.become more energy aware
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 12:22pm 29 Oct 2008
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This is the latest version of the cell equalizer PCB. All loaded, tested and calibrated. Had to cram a lot of components onto the available space and eventually used every I/O on the picaxe micro. Multi layer board and DS:SMD allowed the PCB to shrink somewhat. It helps when the cct has low consumption. This board is to equalize 4 cells as well. Firmware has used most of the EEPROM as well. This size is probably the limit for hand soldering. Will have to look if a chip format is feasable.
Here is a picture.
Trev will need 15 units for his EV main battery pack and I am hoping for a successful outcome with it.
Gordon.
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retepsnikrep Senior Member Joined: 31/12/2007 Location: United KingdomPosts: 131
Posted: 09:44am 01 Nov 2008
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That looks good.
The issue with BMS systems for self conversion enthusiasts like myself though is that most are pretty savy, and don't want a magic black box/circuit where no one knows what's going on inside it. How long will it be supported/available before the inventor turns up his toes or loses interest?
Detailed specs and how it works, possibly even source code etc would be expected in current EV community IMO.
You might find a market for it in more commerical conversion setups as part of a complete system for the more normal man on the street, not the sort of people who frequent this type of message board.
Good luck anyway. I'm keen to see your results. Gen1 Honda Insights.
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 01:10pm 01 Nov 2008
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Hi peter,
I see the battery equalizer as similar to the battery. You did not make the battery cells in your EV. You just bought them. I see the battery cell equalizer fits in the same category. The same goes for the speed controller. Your Honda insight has a factory unit. You did not make a new one. An enthusiast could add these units to their own battery, as this would require just wiring, following a precise procedure. I would think units should be installed by a trained person, as incorrect wiring will destroy a module. Warranty would be difficult to honour with a self installed unit. I know how easily this type of cct is damaged. Damage will occur if a mistake is made during wiring up, rendering a module useless, but once connected to the battery, then it is very reliable unless environmentally compromised. I expect units will become available once a packaging regime is sorted.
I doubt a savy EV enthusiast would be comfortable soldering the 600 or more black spec components needed in a typical EV setup.
The specification might only be the consumption at various battery SOC levels, and maximum/minimum cell voltage limits. How the cct works is not really about source code or how fast a micro can do the maths. You may wish to know exactly how my cct works, but people I know with EV's are more interested in getting more km's per battery recharge. They don't want to monitor all the cells and have to worry if the cells are not balanced. The how does it work is a temporary interest. Once the proof that it does work
is established and the benefit of having it becomes evident, confidence rises and this component of the EV becomes a minor aspect.
I will not be directly testing on an EV. This is done independently, in an objective way. I expect results will be presented when available.
Gordon.
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 10:27pm 18 Nov 2008
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Hi Peter,
If you weren't aware, some performance data is available on Trevs' diary, EV5 thread. I expect there will be more data to be presented for the main pack.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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