Lipo Pack conection question for my old school chopper.

[Kaño]

Hi,

Since I don’t want to burn before reaching Hell, I need to as you gurus a question.

I have a lipo pack of two 22.2V 4ah lipos wired in parallel to power my Cyclone 500w motor, voltage is low and the motor has less speed and torque than with my SLA pack.

So this is the deal, I want to parallel two lipos 7.4V 4AH in a pack and the wire this pack in series to my other pack of 22.2v witch is also a parallel pack.

Is this safe? And most important, would it work? It would give me 29.6V witch is enough for my motor to regain some muscle.

 

[AussieJester]

I would think your getting some pretty bad voltage sag pal, best grabbing a couple more 22v packs

KiM

 

[Kaño]

Yes, Indeed, sag is killing me! I thought Lipos wont sag that much.

But, if I do this pack configuratiòn, would it be all right? I know very little of electricity, so if the answer is obvious, dont get mad at me.

All I have learned so far, was from here. Hey, I used to ride gas engine bikes before I bump with this forum! It is like a parasite taking control of me a bit more each day. :wink:

 

[monster]

sound like you need to invest more on batteries

 

[AussieJester]

Yes, Indeed, sag is killing me! I thought Lipos wont sag that much.

But, if I do this pack configuratiòn, would it be all right? I know very little of electricity, so if the answer is obvious, dont get mad at me.

All I have learned so far, was from here. Hey, I used to ride gas engine bikes before I bump with this forum! It is like a parasite taking control of me a bit more each day. :wink:

I would suggest checking the battery thread and reading up on the chemistry a little before you do ANYTHING more

 

[Kaño]

Ok, will do. Thank you

 

[vanilla ice]

You can do it and it should work fine. There is a small risk of damaging the lipo packs when you connect them in PARALLEL if the voltage is not the same between the pair, so make sure they are equally charged. As far as your connecting the pair of 22.2v packs in SERIES to the pair of 7.4 there is no risk of anything bad happening. Assuming you connect it up right.

Your 22.2v packs are basically just three 7.4v packs connected in series. So you're adding one more, no biggie.

Just curious, what brand 4000mah packs are you using? What kind of Vsag are you seeing? I will be doing the same 2p 4000mah pack thing soon so I'd like compare results.

 

[vanilla ice]

Word. Double post..

 

[Kaño]

Vanilla Ice,

Thank for the info! :wink:

This is a link to the pack I’m using.

http://cgi.ebay.com/2x-11-1v-4000mAh-15C-3S-Li-Po-LiPo-RC-Battery-11-1-WF_W0QQitemZ270449010120QQcategoryZ34056QQcmdZViewItemQQ_trksidZp3907.m263QQ_trkparmsZalgo%3DSIC%26itu%3DMRU-220%252BUCI%252BIA%252BUA%252BFICS%252BUFI%252BDDSIC%26otn%3D12%26po%3DLVI%26ps%3D54

My sag under load is about 2 to 3v after an amp is consumed; the voltage of the pack stabilizes at 22.2v at rest sagging to 20 or 19.7v when load is applied. Min voltage registered by the CA 18.4V.

 

[Drunkskunk]

Yes, you can add the 7.4V packs the way you dezscribes with no problems.

As far as the batteries are concerned, you will have taken a 6s2p battery pack and turned it into an 8s2p.

However, your voltage is pretty low. You might consider a setup that gives you at least 10 cells in series.

 

[vanilla ice]

How many amps are you pulling from those? Those look similar to my ECP's, same shipped price too.

 

[Kaño]

Normal riding about 15 to 20 amps on average, with peak of 49 amps when WOT to try to see my top speed. The Cyclone 500w motor is very hungry!

I suspect that the batteries are not 10C continuous because I’m pulling around 5.5C on peaks and 2.5C on average and they are sagging pretty much around 2 to 3v.

 

[vanilla ice]

I'm seeing the same type of sag with mine. I'm going to try to limit them to 4c max continuous. Even if they are a real 4c cont. 8c burst, I still think the price is not so bad. How much does a 4c 12v 12ah sla cost shipped? I think price comes out the same as these per usable Wh, and sla is so much bulkier and heavier.. safer tho.

 

[Kaño]

Ok so I`m not crazy! There is something wrong with this batteries, the specs were not right.

Perfect, I dont know how to limit de C, so when you finish your test please let me know how it was.

As for the price, hell yes, it is far better than my SLA and my Nimh packs! I guess I only need more lipo bricks.