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  #1  
Old 12-27-2010, 07:09 PM
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Default Review of Headway Battery for the Big 13 Tractor

Hi all,

Hope you will all help out here. Our batteries and other stuff will be arriving on the 4th of January.

I'm going to describe the proposed battery pack/monitering system/charging system layout for the tractor and ask you for opinions.

Don't be afraid to lay it on me if you think somethin is a bad in the set up. I know in advance there are potential holes and problems. Some are irrellivant becaust this is a competition machine and will only run for 15 to 20 seconds at a time. Some I will live with because of cost andweight considerations.

I need to find any problems that I have missed in planning. LAY IT ON ME

Initially we will be using 150 38120P Batteries in a 50S/3P layout. Eventually we will be adding another layer if we find we need it and when we can afford it.

Each set of 3 batteries (four later) will be buddy paralleled (similar to what JACKBAUER is doing).

Each buddy pack of three will be monitored by a Cell Log 8M. Eight buddy packs of three batteries to each Cell Log. This should keep us pretty aware of condition of each buddy pack. If we see a odd or out of spec pack we can look for a dud battery. The cell log will also give us warning if we exceed a low voltage we will decide on when we are pulling.

Each buddy pack of three batteries will be charged by a DC/DC converter, 5 volt in and each converter adjusted to 3.65 volts out. The DC to DC Converters will be powered by a regulated 5 volt 350 +- 50 amp power supply. (I have found a number of these on ebay).

This way, no battery can be charged above 3.65 volts and if a buddy pack will not come up to spec. we can check the individual cells.

We never expect to do more then two consecutive runs within 15 to 20 minutes. The charger should restore the pack well enough between hooks.

20 inches wide x 6 inches thick x 50 inches long, about 100 pounds, a killer battery. 172 volts (3.45 voltsper cell) and 24ah nominal and up to 600 amps at I hope 2.6 to 3 volts per cell times 50 cells under load. Up to 90 kW. Oh Boy.

Y'all be well and have a great New Year.
Jim
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Last edited by Jimdear2; 12-27-2010 at 07:13 PM.
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  #2  
Old 12-27-2010, 09:33 PM
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Default Re: Review of Headway Battery for the Big 13 Tractor

Which dc/dc converters are you going to use? I'm with you on that setup though! I would do some testing as to the current draw etc when you start to charge from various SOC levels. Otherwise your setup sounds good, I'm sure others will find the holes
Good luck!
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  #3  
Old 12-27-2010, 09:42 PM
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Default Re: Review of Headway Battery for the Big 13 Tractor

My partner whom is the electronics wiz has them. All I know right now is they are 5 volts in and adjustible 3 to 4 volts out and I think he said 9 amps. I'll get names and numbers from him tomorrow if I can.

He has been using a jury rig with them to charge our test batteries. Seem to work quite well
Jim
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Old 12-27-2010, 11:00 PM
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Default Re: Review of Headway Battery for the Big 13 Tractor

here are some 20A vicor's. They need a 48V front end.

http://cgi.ebay.com/VICOR-DC-DC-CONV...item45f51942f9

$10 each ain't bad. Seller might sell for less in higher quantities.
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Old 12-27-2010, 11:22 PM
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Default Re: Review of Headway Battery for the Big 13 Tractor

Quote:
Originally Posted by frodus View Post
here are some 20A vicor's. They need a 48V front end.

http://cgi.ebay.com/VICOR-DC-DC-CONV...item45f51942f9

$10 each ain't bad. Seller might sell for less in higher quantities.
Frodus,

Thanks for the tip.

Darin has located something that run $3.50 in quantity. Just a board so we will need to box them, probably with the panel that will hold the Cell Logs. They are 5 volt input and adjustable output.

I plan on using something like this to power the DC to DC Converters.

http://cgi.ebay.com/ACDC-Power-Suppl...item563c2ed106.

I've found a bunch of these ranging from $80.00 to $300.00 with outputs up to 450 amps and inputs from 100 to 240 volts, 50 and 60 hz.

Thanks and Happy New Year,
Jim
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Old 12-27-2010, 11:27 PM
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Default Re: Review of Headway Battery for the Big 13 Tractor

Quote:
Originally Posted by frodus View Post
here are some 20A vicor's. They need a 48V front end.

http://cgi.ebay.com/VICOR-DC-DC-CONV...item45f51942f9

$10 each ain't bad. Seller might sell for less in higher quantities.

Here's the ones I'm using ($4.95 or less...), and they seem to perform pretty well:
http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT

I have a temporary setup that works really well, I assembled the pack quite unbalanced to see how it would bring it in line, which it did very nicely.

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Old 12-27-2010, 11:45 PM
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Default Re: Review of Headway Battery for the Big 13 Tractor

RW,

Your set up works well? Great that is encouraging.

I have a question for you. It looks like you are using aluminium for your connecting buss. Are you having any heating problems.

I was going to order the copper to make up my buss connectors tomorrow, but just the raw material was over $200.00. Aluminium should be quite a bit cheaper. I know aluminium will carry a lot of current and you need to size up at least 50% or more. Do you know of any rule on sizing?

Are you noticing any problems? It looks like you are powering audio AMPs and I know they will pull a LOT of current.

Thanks,
Jim
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Old 12-28-2010, 12:16 AM
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Default Re: Review of Headway Battery for the Big 13 Tractor

Quote:
Originally Posted by Jimdear2 View Post
RW,

Your set up works well? Great that is encouraging.

I have a question for you. It looks like you are using aluminium for your connecting buss. Are you having any heating problems.

I was going to order the copper to make up my buss connectors tomorrow, but just the raw material was over $200.00. Aluminium should be quite a bit cheaper. I know aluminium will carry a lot of current and you need to size up at least 50% or more. Do you know of any rule on sizing?

Are you noticing any problems? It looks like you are powering audio AMPs and I know they will pull a LOT of current.

Thanks,
Jim
So far I have 1/2 a dozen cycles at different SOC and the dc/dc converters charge things nicely, I'm charging to 3.5V now. I started out at 3.65V but at over about 50% discharge it was drawing huge currents from the dc/dc converters (mine will put out 27-28A at slight overload) however dialing the voltage back a bit put me in a nicer current output even when the cells are quite discharged.

As for the aluminum, I'm using 1/8" and there is zero heat but I can only draw about 100A right now, I did use it to shart my Porsche as well but that was a very short burst. Like you said a 50% oversize isn't bad, the technical equivalent is more like +33ish% but 50% makes the numbers easy and actually increases the current capacity slightly over copper. The weight/size/cost makes it a decent alternative, just be aware of the properties of aluminum oxide. However if you start to compare what some little 90C lipo's are using (10 or 12awg copper) to carry their big currents, 1/8" aluminum starts to look huge!
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Old 12-28-2010, 06:45 PM
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Default Re: Review of Headway Battery for the Big 13 Tractor

Quote:
Originally Posted by Jimdear2 View Post
I have a question for you. It looks like you are using aluminium for your connecting buss. Are you having any heating problems.
For my motorcycle I used 11 Ga (0.091") aluminium bar to pass around 600A peak to the battery without problems. I use NO-OX-ID compound at terminal (contact area).
But my buss bar was large! 0.091" x 2" give a great area.

My understanding is: AWG 00 (2-0) copper wire have a 0.105" square of conductor area.
So 0.125 aluminium bar need to be 1-1/4" tall for have same resistance. (0.105" / 0.125" / 0.66 = 1.27")
And in your case, because you use 3P configuration, 1/8 x 1/2 bar will be electrically good but 1/8 x 3/4 will be structurally better!



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Old 12-29-2010, 04:35 PM
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Default Re: Review of Headway Battery for the Big 13 Tractor

Yabert,

You may find this information supprising, I sure did.

I do admit that my original method of selection of the copper was a bit of research and a bit of gut. Probably I could get by with a bit smaller stock but Since most of the work this battery will do is full on have no mercy 20 to 25C, I wanted to err on the side of caution.

I went to my metal supplier's catalog and looked up aluminium plate and bars with approx 50% increase in size. I was shocked to see the price of the aluminium was quite a bit higher then the smaller copper stock. To go with 50% bigger aluminium would have cost about 15% more.

Live and learn.

I still say the stuff you build is first quality.

Have a gooooooooooooood New Year,
Jim
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Last edited by Jimdear2; 12-29-2010 at 04:37 PM.
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