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Tinker

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Joined: 07/11/2007
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Posted: 01:52pm 10 Feb 2012

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Trev, just out of curiosity with regard to the middle cell(s) getting hot.
If one wanted a 4 cell (12V nominal) battery set up how practical is it to stack the cells end to end (narrow sides touching)? This would expose a much larger surface area for cooling.
I guess the strapping could be replaced by tapped rods which likely are more rigid over the extra length.

Klaus

grub
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Joined: 27/11/2007
Location: Australia
Posts: 169

Posted: 09:41pm 10 Feb 2012

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Trev, would it help you if you sandwiched the middle cells that get hotter with a thin aluminum heat disperser? Something with lots of fins to aid heat dispensation like square tubing cut to length and set next to each over to form a block on each cell side/end?

Trev

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Joined: 15/07/2006
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Posts: 640

Posted: 10:08am 11 Feb 2012

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Tinker, not practical end to end. Besides, they are already, as well.

Grub, that would increase the heat dissipation. My biggest problem in the main pack is they are inside a sealed insulated fibreglass box. The heat can't get out. My next set of batteries I intend to make alloy checker plate boxes, with air gaps, still sealed, but heat can dissipate throught the alloy.

Generally they don't need anything between them. You can see the ribs in the side of the cells, the ribs keep the cells apart a little and so heat rises up the holes.

Trev @ drivebynature.com

Trev

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Joined: 15/07/2006
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Posted: 11:30am 15 Feb 2012

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Gordon sent me an update on Relativities Active Balancing testing.

Quite some time ago I sent 8 cells x 90ah to Gordon to connect up to his 24v wind & solar system for the purpose of testing the Relativities. In a recent post I said, must be near 3 years now. Gordon assures me it is just over 2yrs, like 2 yrs and 3 months.

Gordon says
Here are some pics, of the drawdown curves, and the recharging curves. We used over 2kWh from the battery. Check out the kWh discharge, 2.13kWh, and the kWh used to recharge, 2.10kWh. These are circled in red. Pretty close to the same energy. A tribute to the performance of the Lithium chemistry. The dark red trace is battery current. Charging above centre, and discharging below, with a +/- 20A scaling. The green circles show the normal absorption time, as well as in the second pic, the battery was equalized. This is a fully automated system, with no user intervention.
The cells do separate slightly in voltage at the extreme voltages, but the equalizers can be seen to be bringing the differences down. This is the blue trace. It had been about a month since the last equalization had occurred. The multi coloured traces are the superimposed individual cell voltages. The recordings are at 10sec intervals. The normal scaling is 3-4V, that is 3v at the bottom and 4v at the top of the black window. This is a narrow range, so the working voltage range of the battery is from about 3.45 to 3.2 cell Volts, and the battery is considered charged at a cell volts of 3.65. The centre of the screen is 3.5V, or equivalent to 28V on the battery. As you know, this 8cell Lithium pack is in parallel with my 24Vnom lead acid battery.

Trev @ drivebynature.com

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 03:00pm 15 Feb 2012

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Hi Trev

By the look of the results the equalization is working well and maybe the
batteries are more suited to this style of use, as I have a number of people tell me that the string of cells to get high voltage for care use kills the odd cell,

All the best

Bob

Foolin Around

Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 4406

Posted: 01:16am 20 Feb 2012

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I have been giving some thought to the battery cooling problem.
Air cooling is just not going to work because of the the required very close packing between cells.

But suppose you could sandwich a serpentine metal pipe between two aluminium plates, and circulate cooling water?
Pack those between cells, or alternate cells.

Even a simple single "U" shape pipe may be sufficient, because the aluminium will conduct very well over it's whole surface area back into the battery.

Perhaps some quarter inch copper pipe epoxied between two flat aluminium plates.
Coat the pipe with epoxy, and squash down on the whole thing in a hydraulic press until the epoxy cures.

There is not a lot of heat to remove, just something to stop the temperature from very slowly building up over time.

Cheers, �Tony.

Trev

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Joined: 15/07/2006
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Posted: 08:27am 26 Feb 2012

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Bob, the high voltage string has nothing to do with killing a cell.
Tony, in some aplications water heating/cooling has been done. However, for normal driving there is not much heat to remove. I don't believe it is necessary.

About a month ago I fitted a Soliton 1 speed controller to the EV Hilux. Fiday, tidied up the wiring.

Very easy to program with a standard ethernet cable to computer conneted to the web interface. I have it set at 600A max, standard factory acelleration and motor max votage at 150v.

This controller is very nice. Smooth and very controlled. Hilux acceleration is a bit quicker. The Soliton controller is better efficiency too. Generally I use around 14.5kwh to do my normal 75km round trip each day. With the Curtis I used around 17kwh. Controller heat is no longer an issue. It delivers power much better than the Curtis.

The engine bay looks even more empty now.

Edited by Trev 2012-02-27

Trev @ drivebynature.com

Trev

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Joined: 15/07/2006
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Posts: 640

Posted: 09:27am 26 Feb 2012

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The 3.7v chargers have been taken out, a while ago.

The 14.8v chargers have been fitted, waiting for the Relativities Active Balancing circuits. Yes, we are going to test again in the EV Hilux! It has been a long time! Am I excited? Should be here soon. I did not bother trying to mount the 14.8v chargers, they are just in the battery box.

The idea is that the 14.8v chargers can assist in providing a better spread of power without the huge number of chargers used in single cell charging. It is at the end of charge that the biggest difference in cell voltage occurs, and that's where these 14.8v chargers will work. Only needed in the long series string of an EV. Not needed in a solar/wind RE system using a smaller number of cells in a series string.

Last weekend I had to manual balance the main pack again. I used several 3.7v chargers and a 12v auto light. Much quicker manual balancing than I have done in previous times. Though much longer time than when I had a 3.7v charger on every cell and every morning they were switched on.

The 12v block voltages were getting further apart. Peak difference this morning was 3.80v to 3.33v. I connected 4 of the 3.7v chargers to balance them. As said before, these cells (12v block cells) have not been balanced since I had the very first Relativities prototype on them. After a few hours the peak difference was 3.71v to 3.73v. Very Good. They will be right for a long time again.

Edited by Trev 2012-02-27

Trev @ drivebynature.com

Trev

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Joined: 15/07/2006
Location: Australia
Posts: 640

Posted: 11:13am 27 Mar 2012

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The new version of Relativities arrived. I made new moulds to pot them for protection. With plugs, all the wiring can be done without risk of damaging the Relativities. A wiring test circuit was also provided, so all wiring can be tested to make sure it is connected correctly before connecting Relativivites. A brilliant setup. They are also now made in 8 cell units (balancing 8 cells), as well as the 4 cell units (balancing 4 cells).

I have 5 x 8 cell Relativities and 1 x 4 cell Relativities. They are connected across 44 cells, not overlapped. I am using the 14.8v chargers to break up and distribute the charge across the pack and then Relativities active balance all the time in a smaller area.

It is great to see a cell difference of only 0.08v each morning. Relativities and the 14.8v chargers are working well.

Except I have a couple of cells that have a higher self discharge than the rest of the pack and so I have the single cell (3.7v chargers) setup in that area of the pack. One of those 2 cells, only started about a week ago, became obvious when lower than the rest. I have 3 x 3.7v chargers connected to it and so it gets 12A help every morning.

With a new pack, or a pack well looked after, Relativities may work by themselves without the small chargers, but not this pack I have now.

Relativities has been connected for a few weeks now. All working good. They are over the back of the battery pack. There was not quite enough room above the batteries. The plug adds a little more height to the units. An example picture of the monitor screen shows just 0.08v difference between the highest and lowest cell. This is how it is every morning.

Trev @ drivebynature.com

Tinker

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Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 01:34pm 27 Mar 2012

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Thanks for that post Trev.

Ever since you mentioned these 'relativities' gadgets I was wondering how many wires are required to run them. It appears its just a pair of wires to each cell and two wires to the bank voltage terminals (4 or 8 cell units), is that correct?

The gadget appears to be just sitting atop a cell so one can assume it does not get hot nor needs heat sinking?

Is the testing period still in progress or are these gadgets already available with the purchase of a LIPO battery bank?

Very neat packaging BTW, I like the look of it. Now, if I only could get my tongue around the word 'relativities'

- not easy for someone to whom English is a second language.

Klaus

Trev

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Joined: 15/07/2006
Location: Australia
Posts: 640

Posted: 07:25am 28 Mar 2012

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Klaus,
9 wires to balance 8 cells and 5 wires to balance 4 cells. Each Relativities has one negative wire for the whole block and one positive wire for each cell in the block.

No heat (no burnoff). It transfers power from a high volt cell to a low volt cell.

Still in testing, although we are considering a small production run.

Trev @ drivebynature.com

Tinker

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Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 01:47pm 28 Mar 2012

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Thanks Trev, these units are what I will choose for that planned LIPO battery bank - hopefully they are available then.

More questions if I may ask

, Is there a power drain from the Relativities (standby power) if all LIPO cells are balanced?
Also what is the 3 pin connector for?

Klaus

Trev

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Joined: 15/07/2006
Location: Australia
Posts: 640

Posted: 11:39pm 21 Jul 2012

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Yes Klaus, there is a small power draw, even when balanced. I forget now what Gordon told me. It is extremely small though, nothing to worry about. They are pluggable so if you were going to leave the batteries for a long time without chanrge then it is possible to just unplug them. The 3 pin connector is for Gordon to program them.

Trev @ drivebynature.com

Trev

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Joined: 15/07/2006
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Posts: 640

Posted: 12:03am 22 Jul 2012

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I have drained the 12v block too low, too many times, and one cell developed a higher self discharge than the others. I removed the C-Tek charger and fitted 4 single cell chargers. But the 4 single cell chargers (4A) were not able to replace the normal daily power usage when switched on over night (off peak). But I thought it was ok, and just play catch up on the weekends. Obviously not.

One morning not so long ago, I found that the single cell charger did not switch on, possibly because the cell voltage was too low. Well that doesn't help a cell that is already too low. It still had to supply power to the main monitoring screen, while the main pack was being charged at the same time (off peak overnight).

I found it had been reversed. Dead. I tried to charge it but it would not take a charge.

So I replaced it with a LYP. The original 4 are LFP. I will leave it with single cell charging, so the 2 chemistries don't muck me up if I were to charge with the C-Tek.

Dad cut the dead one open. Nothing run out, but it was moist with something inside. A clear like fluid. The plates were just copper and aluminium foil alternating with some kind of insulation between them.

Trev @ drivebynature.com

Tinker

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Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 03:08am 22 Jul 2012

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Thanks for that info Trev, interesting what you found inside a lithium battery. I hope that stuff is not poisonous.
Regarding Gordon's Relativities gadget, I was brainstorming this thing and think I have come up with my own version of individual cell charge equalization without wasting excess charge as heat.
All theory so far but as soon as my new batteries arrive I will build a prototype to test it, let you know of the outcome.
It won't be as neat & clever a Gordon's but sometimes the basic approach works just as well

Klaus

Trev

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Joined: 15/07/2006
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Posts: 640

Posted: 01:09am 25 Jul 2012

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I have wanted to add more cells to my main pack for a while. In fact my camper set was originally bought to be in the main pack, plus one more, making it to 50 cells.

With the pack getting to the point were range was borderline reaching 80km, I have now made the effort to add the extra cells.

With current situation and thinking decided to use these 5 plus 3 more, making it up to 52 cells now in the pack. These 8 new ones are LYP and the old ones are LFP chemistry. The Zivan chargers have the output voltage adjusted to suit the new pack voltage. For balancing, I did not have any more Relativities, so single cell (3.7v) chargers are used. All small chargers are switched on by the end of the Zivan charge. These 8 new cells are also monitored on the same monitoring screen as the others. Performance and range has been increased.

Relativities testing has proved reliable. They are still working.

So far have driven on these batteries, 419582 - fitted with speedo reading 350153 = 69429km.
That makes it $16200 / 69429 = $0.23 cents per km.
There is still more power in them yet.

Trev @ drivebynature.com

Trev

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Joined: 15/07/2006
Location: Australia
Posts: 640

Posted: 11:57am 28 Jul 2012

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Sideline note (not EV).

Tested an old version of Relativities on a 12v 90ah lithium block used as a standard vehicle starter battery. This battery block was the one I used in the mower as a starter. It has been over charged, I discovered the mower does not have regulation. If I remember right the pack was charge to 18v?? It swelled a bit but still works well.

Measured the instant jump of current on start up to be 250A.
Both, lithium battery and Relativities are working well.

Our Ford Laser is our long range vehicle.

I can't remember exactly when fitted to the Laser, must 3 to 4 months ago.

Trev @ drivebynature.com

Trev

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Joined: 15/07/2006
Location: Australia
Posts: 640

Posted: 01:06am 06 Aug 2012

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Last week went camping with a bunch of year eight students. Too much fun and very little sleep.

Home on Friday, went to bed early, very tired and forgot to plug in. Next morning discovered the 12v battery had drained its last and one cell with voltage reversed. They don't like being drained empty! I tried to charge it. To start with seemed to take a charge but would not go passed 1.15v. Removed chargers and immediately dropped back to below zero.

So removed it. It was hard to get out with the ends still fixed in the mounting frame. Very much swelled, even the top and edges.

I decided to put in a cell that was damaged in transport (split). It apparently had leaked out a bit of fluid? Dad used a soldering iron to melt over the crack. Charged it several weeks ago and was still holding charge. Fitted, charged and tested capacity on discharge. I figure it has about 50ah. Originally a 90ah cell. Should do me for a while. I don't normally use that much. It will be interesting to see if it can last.

Trev @ drivebynature.com

Wombat

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Joined: 27/05/2011
Location: Australia
Posts: 72

Posted: 12:55am 08 Aug 2012

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Hi Trev.

I've been following your post with great interest.

I have a heap of 12v battery's that are in need of
controlled equalization.

Will/would you be building a 12V version of your "Relativities"?,
as I think they would be quite popular. With me anyway!

Keep up the great work!

Russ.

perth
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Joined: 25/11/2012
Location: Australia
Posts: 12

Posted: 12:18am 28 Nov 2012

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out of curiosity, what if youd have your ev hilux and never equalized the cells.
would it halve your battery life or reduce or range? what would be the consequences?

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