help finding an appropriate 3s lipo

[ambientvoid]

i bought two high capacity Turnigy Multistar 4s 10000mah batteries to link in series for 8s but i made a mistake on the voltage i needed and i actually need 7s so i want to purchase a 3s battery to go with one of my 4s batteries, im having a hard time finding an appropriate battery though so can someone help thanks?

 

[pwd]

Just curious, why do you need 7s?

I see that hobbyking doesn't have what you are looking for... might have to try another site. A quick google search came up with this:
http://www.overlander.co.uk/10000mah-3s-11-1v-20c-lipo-battery-overlander-supersportxl.html

Here is the search:
http://lmgtfy.com/?q=3S+10000mah

 

[wesnewell]

Unless you have a need for a 4s pack, just remove a cell from one of them and make it a 3s pack.

 

[ambientvoid]

ok well i did do that google search before posting here after failing to find anything on hobbyking, however i wasn't sure if mixing different brands of batteries would be okay and im a bit hazy on whether its ok to have 2 batteries with different C ratings connected together (the overlander battery is 20C and my battery is 10C).
i need 7s because im powering a 30V amplifier module for a trailer mounted speaker and im worried that going 3 or 4 volts over with an 8s pack might end up damaging it.

and taking apart batteries im told might explode if pierced is well beyond my skillset and confidence...

 

[motomech]

They don't explode. If a pouch is punctured, the reaction w/ air will cause it to glow a deep red inside w/perhaps a little smoke. Kind of like looking into a mini Mordor.
You wouldn't remove any cells, but move the Pos. main lead inside to the next cell and clip the red balance wire. It has to be the Pos. wire since electricity "flows" Neg. to Pos.

 

[dogman dan]

Right now, it's Chinese New year. DO NOT ORDER SHIT FROM CHINA TODAY. Wait a week or even two.

Soon,, Hobby king and others will sober up, and the spring stock will be in the warehouse. Then you can find some 3s.

for your application,, it should not matter if you mix brands or c rates. just get capacity the same. Just be sure your lowest c rate packs can handle the load.

 

[ambientvoid]

i had another look at the sure tk2050 user manual link on parts express (weirdly i didn't get a paper copy with my amp) to double check the max voltage and it seems to list two maximum voltages, in the Electrical Characteristics section it says the max input voltage is 30V but in the Overview section it says it can be powered by "any DC power supply ranging from +10 to 36V, which can be used to drive any 4ohm or 8ohm passive speakers". so that's confusing...
also in the introduction Notes section it says it recommends DC36V to power it for 1 hour, so it's possible that the 30V max is for continuous usage in which case is it possible that 32 to 33V would be ok for a few hours at a time?

 

[Ianhill]

What you will find is as you up the voltage it will draw more current, if the high end volume sounds undistorted then your good to go, soon as you apply the battery voltage will drop away to 28.8v when around 80% flat so keep it 8s it fits the voltage range best 7s will drop to 25ish volt when flat with less output.
When I used to run my 9v amps at 14.4v they worked much louder but would draw more current so make sure it has good heat dissipation on board.
Sounds a nice little project I like my subwoofers myself cracked my door frame with a pioneer splx sub running 2000w in my room.

 

[ambientvoid]

the amplifier has a small but chunky heatsink with a small computer style fan on top which should do a good job of keeping it cool and as i intend to use it outside it should keep extra cool, now being in the UK the default weather is rain regardless of the time of year so as much as i intend to use it only on sunny days there's a fair chance of being caught out in the wet so i was wondering could i mount the amp board upside down in a tupperware box vented on the bottom and raised up to leave an air gap underneath? that way i think it should further reduce the chance of water ingress if i am caught out in rain...

 

[dogman dan]

Sounds like 8s is the way to go then. As you run it, it will drop down in voltage after all. In a very short time it will be down to 4v per cell, much closer to the range it "likes".

A slight undercharge, and you would start at 4.1v per cell.

 

[ambientvoid]

A slight undercharge, and you would start at 4.1v per cell.

I have a Turnigy Reaktor balance charger, so far I've just used the standard balance charge for everything but do you know if it's possible to set a limit for the balance charge to 4.1v?

 

[Ianhill]

A slight undercharge, and you would start at 4.1v per cell.

I have a Turnigy Reaktor balance charger, so far I've just used the standard balance charge for everything but do you know if it's possible to set a limit for the balance charge to 4.1v?

Should be in settings and end voltage.
I can set my lipo to 4.2v and lilo to 3.9v so when I charge the lipo in lilo mode it balance's the cells to 3.9v then It discharge them to 3.7v for storage so it completes a maintence cycle I do that around once a month to all my batts to check the figures and gauge their health.

 

[kingjamez]

A slight undercharge, and you would start at 4.1v per cell.

I have a Turnigy Reaktor balance charger, so far I've just used the standard balance charge for everything but do you know if it's possible to set a limit for the balance charge to 4.1v?

Set your Reaktor to Li-Ion instead of LiPoly and it will top out at 4.1 volts instead of 4.2 volts. I do this on my multistars for the added longevity it gives to the packs.

-Jim