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Lipo Pack for 48V Brushless motor

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viperr View Drop Down
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  Quote viperr Quote  Post ReplyReply Direct Link To This Post Topic: Lipo Pack for 48V Brushless motor
    Posted: 19/Mar/2009 at 4:56pm
Hi,

I would like to make up a Lipo pack to power my Large Brushless motor.

The motor is 48V and rated at 150Amps Max.

I would like to make a Lipo battery pack to drive it and also have a good capacity to achieve for 0.5h to 1h duration or more. ie maybe 30Ah to 70Ah.

Can you help me please with a cost effective option / options ?

Thanks
Rob.
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W3FJW Ron View Drop Down
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  Quote W3FJW Ron Quote  Post ReplyReply Direct Link To This Post Posted: 19/Mar/2009 at 5:22pm
It appears you would need a 12S pack with a 30 to 70 ah rating. The largest Lipo packs sold here are 6S 5ah packs so you would need (for 30ah)  12 packs in a 12S6P configuration which would cost between $85 to $120 for each pack depending upon the brand. If your average motor current is 30 amps, that would give you a 1 hour duration.

It would help more if you would tell us the use you're putting it to and the actual operating parameters of the motor.

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  Quote u4eake Quote  Post ReplyReply Direct Link To This Post Posted: 19/Mar/2009 at 5:27pm
I've been looking at that also for an electric bike.
Best buy I have found is 20 of these 6S packs arranged in a 2S10P configuration to get 12S 50Ah. That will give you about 2400W during an hour.

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7639

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  Quote viperr Quote  Post ReplyReply Direct Link To This Post Posted: 20/Mar/2009 at 7:20pm
HXT 80-100-B 130Kv Brushless Outrunner (eq: 70-55)
This is the motor I want to run - the parameters are listed on the website.
im in australia and with the exchange rate sadly dropping i need a cost effective option.
Thanks for your replys they are much appreciated.
Any additional options would be great.
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  Quote Not Yet Quote  Post ReplyReply Direct Link To This Post Posted: 24/Mar/2009 at 4:32am

Hi, a newbie here.

I too am thinking of using the HXT 80-100-B 130Kv Brushless Outrunner (eq: 70-55).

However I only need 2 minutes of endurance provided I can recharge the pack as a hole from a 12 Volt system.

The application is to power the prerotator of a gyroplane. After takeoff I would like to recharge from the onboard 12 Volt system.

Is this practical or possible?

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  Quote W3FJW Ron Quote  Post ReplyReply Direct Link To This Post Posted: 24/Mar/2009 at 7:18am
You can use a charger for a lipo pack connected to your 12V system. However, I can't think of anyway of doing it automatically like in an auto or airplane as is done with a pb battery with alternator & regulator.
I don't think it would be healthy for the charger and battery to be connected permanently into the system while prerotation (HXT running) is taking place but I don't know as I've never heard of anyone doing this.
It would be possible to switch the charger/battery for charging to the 12V system manually though.
I don't know if there's a 12S charger in HK inventory though.
The 12S battery may need to be charged as two 6S either separately or in parallel.


Edited by W3FJW Ron - 24/Mar/2009 at 7:24am
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  Quote Not Yet Quote  Post ReplyReply Direct Link To This Post Posted: 25/Mar/2009 at 1:04am

Thank you Ron

 

I don’t understand any of the nomenclature of these batteries.

If I understand you correctly, I would need two 6S batteries wired in sires, to run the motor, and wired in parallel for charging. If I have a switch between the batteries and the ESC, and a switch between the batteries and the charger set so only one at a time can be closed, would this work?

Could you please help me understand what the battery nomenclature is or means.

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  Quote W3FJW Ron Quote  Post ReplyReply Direct Link To This Post Posted: 25/Mar/2009 at 5:55am
Ok, lets see.
pb is a lead acid battery, Lipo is a Lipoly battery,  S or more commonly 1S is a single cell Lipo, P is the number of cells/batteries in parallel, 1C is the capacity of the battery in amps or more commonly mah (miliampere hours).
Lipoly batteries should be charged at the 1C rate or less. Any more can/will shorten the life of the cells. They should also be balance charged which means all the cells are monitored to keep all the cells at the same state of charge so one or more cells in the pack do not overcharge which can ruin the battery pack if the cell voltage exceeds ~4.2 volts which can also lead to the cell catching on fire or exploding (rapid rate of burning rather than an explosion as we define an explosion).

So a 6S battery pack = ~24 volts. There is no charger that I'm aware of that will charge a 12S battery, hence the need to charge the 6S pack in parallel or the two 6S packs separately.
A better battery for your purposes would be the LifePo4 cells which can have up to 60C discharge rates and can be charged at up to a 10C rate. http://www.hobbycity.com/hobbycity/store/uh_listCategoriesAndProducts.asp?catname=LiFePo4&idCategory=218&ParentCat=85
Your idea of switching of switching between battery packs would work if balancing the batteries is not taken into account which is probably ok if the batteries are balance charged every 3 or 4 times they are discharged.
To be honest, I am not that familiar with LifePo4 batteries so some reading up on them would be necessary by you (and me for my information) to make sure they would be useful for your application.
Personally, I'd hesitate about using Lipoly batteries in your application.
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I can only remember half of what I say....
I used to walk on water 'til I found out it was more fun sitting in the boat drinking beer

Ron
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  Quote Smeagle Quote  Post ReplyReply Direct Link To This Post Posted: 25/Mar/2009 at 5:17pm
Hi NotYet,

No offense meant, but you seem to have not much experience with electric flight. I would suggest, to first use the equipment as it is intended to be used. And if you got some experience and everything works, only then you should start to build fancy "charge while flying" systems... You will need a lot of electronics skills to build a system like that!

- Oliver
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  Quote W3FJW Ron Quote  Post ReplyReply Direct Link To This Post Posted: 25/Mar/2009 at 5:45pm
You should read the posts more carefully Oliver. He's using this equipment to get his blades started on a full size gyroplane. Not a model.

Edited by W3FJW Ron - 25/Mar/2009 at 5:47pm
Best Regards
I can only remember half of what I say....
I used to walk on water 'til I found out it was more fun sitting in the boat drinking beer

Ron
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