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Old 26th January 2011, 12:14 AM   #1
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Default Battery project

Check out my batt box...

4 cell 38120S Headway LiFePO4 box... 13.3V nominal, 10Ah capacity.

Imageshack - gedc0147.jpg

http://img39.imageshack.us/img39/7234/gedc0149.jpg

http://img254.imageshack.us/img254/5876/gedc0154.jpg

2 outputs, 1 non-switched w/ JST-XH balance plug, 1 switched.

switch paralleled with temperature/voltage monitor.
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Old 26th January 2011, 05:49 AM   #2
Hitec is offline Hitec  Finland
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OK that's it; perfect cells for a boombox have been found . I did not know there are such nice cells. It is very nice to have a screw-attachment in the battery heads. No need for soldering. They seem to have over/undervoltage protection. Do they need anything else for charging than a current limiter (I guess yes)? Or are you planning to build/buy some kind of a BMS?
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Old 26th January 2011, 07:26 AM   #3
luka is offline luka  Slovenia
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wow? 10Ah? and 100A constant? beast... if you would take 2 or more likely 3 rows like that, you could start a car with it LOL
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Old 26th January 2011, 08:40 AM   #4
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Very nice. You've found some pretty cheap LFP cells there, I've order some from the same place immidiately as that's around 1/3rd of the price I have been previously quoted for the same type of product (I don't expect much difference between cells from different brands as they probably come from the same manufacturer but with different branding).
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Old 26th January 2011, 09:26 PM   #5
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Unfortunately, I'm running them unprotected which is why I put a voltage monitor on it. The monitor will sound an alarm if it falls below 10.5 Volts. I found it on Ebay for about $13. I couldn't find a BMS with the specs that I wanted for an affordable price.

I'm charging it using a Turnigy Accucell 6 which will balance the cells as it charges. (It works best to initially charge them in "storage" mode first, but thats another story)

I've had it for about 3 months and so far I've only charged it twice. However I don't think I really needed to, since it was only like 12.8 or 12.5 volts.

4 cells, spacers and the bus bars were $83.00, shipping was about $13. Hard to beat. All thanks to Manzanita Micro Power Systems.

More pics...

Front
http://img268.imageshack.us/img268/7...dc0162copy.jpg

Back
http://img692.imageshack.us/img692/4...dc0161copy.jpg

set up
http://img29.imageshack.us/img29/5739/gedc0157copy.jpg

oops, there's the power supply cord I don't use anymore. Also pictured is a Helder MKIII TA2020, and the MKI buffer.

There's a small, but very noticeable sound improvement, and a slight power increase.
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Old 26th January 2011, 10:01 PM   #6
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looks like I'll be adding a BMS

http://www.ebike-bmsbattery.com/inde...Fdid%3D6&did=6

cells
http://www.ebike-bmsbattery.com/inde...Fdid%3D1&did=1

Last edited by carlsbad64; 26th January 2011 at 10:04 PM.
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Old 26th January 2011, 10:12 PM   #7
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Pretty sure you can make a working LVD with a low current relay, a zener diode and a resistor.
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Old 27th January 2011, 06:13 AM   #8
Hitec is offline Hitec  Finland
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Quote:
Originally Posted by carlsbad64 View Post
This looks good but they give only a little information of what is inside the BMS. I think it resistively balances overcharged cells? Anyway it is very cheap if it contains all the functionality a BMS should have

But adding 8 of these cells and a BMS would add some watt-hours to the boombox and reduce a lot of weight compared to the lead-acid 18Ah system we have now . Then there is only the charging that would have to be solved.

I have actually been planning a charger with a LTC3780, a buck-boost controller with current limiting. This could take input voltages of 4-36V and output a constant voltage/current to the battery pack. However, I'm now busy with designing a preamplifier to it so this will maybe wait for a while.
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Old 30th January 2011, 09:54 PM   #9
col is offline col  Australia
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Quote:
Originally Posted by Saturnus View Post
Very nice. You've found some pretty cheap LFP cells there, I've order some from the same place immidiately as that's around 1/3rd of the price I have been previously quoted for the same type of product (I don't expect much difference between cells from different brands as they probably come from the same manufacturer but with different branding).
Hi Saturnus, do you have a URL for the retailer you used?

cheers,
col.
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