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Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

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Old 03-05-2011, 02:41 PM   #1
DanWard
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Question Charging two 4S packs at one time?

I never know if I should continue to post in the beginner section or if like in this case it is OK to post in a section that is more specific to my question.

I have the cable that lets me change two 3S packs in series as if they were one 6S pack. It works well as long as packs are same mA and at approximatly the same state of dischange when I start charging them.

Recently a new plane has me now using 4S packs. I'd like to find a similar cable but search is not being my friend. Maybe no one makes one for sale?

If I can't buy one is it possible to buy two of the required 4S connectors and one 8S connector and make my onw? I know how my 3S to 6S is wired because when I received it I had problems right at first until I discovered it had been miswired by the manufacture. Once I swapped a couple of the wires around it has worked great.

Thanks,
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Old 03-05-2011, 04:36 PM   #2
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Default Charging two 4S packs at one time?

It would probably be easier to charge in parallel rather than series. I will post a pic of my set up for 3s packs. It could easily be made for 4s.

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Old 03-07-2011, 05:26 AM   #3
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Yup. Unless your charger can do 8S packs, you will have to do them in parallel.

Its fairly easy.

Make up a 'Y' lead for the main pack leads. Then connect the two packs to the Y and connect the other leg of the Y to the charger as if it was a single pack.

The next step is tedious but not hard - make up another 'Y' connector that Y's together all the balance tap leads in exactly the same way. Then connect just like the main leads.

Once you connect the two packs together, your charger "sees" a single 4S pack with twice the capacity. It will charge just like that.

You are doing what was common a few years ago (before large capacity cells became common) and making a 4S2P pack.

The two packs need to be at least vaguely close in voltage before you hook them up together but thats not as big a deal as many people think.

Even if they are a full volt different they will be fine to connect up together unless they are very old, low C cells.

The equalizing current that you will get between the packs wont be hi enough to worry about.

Just to refress my memory, I just did a test with two 4S 2200 mahr packs. One was almost fully charged at 16.4 volts. The other was at storage (about 50%) charge at 15.4 volts about a 1 volt difference.

The equalizing current starts out at about 6 amps or 3C charge/discharge rate. Safe enough for any modern cells. It quickly drops to about 2 amps or 1C as the packs equalize in voltage.

1 volt or so difference is my personal limit though more would probably be safe if your using good quality packs.

I think I need a signature.
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Old 03-07-2011, 07:13 AM   #4
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Originally Posted by DanWard View Post
I never know if I should continue to post in the beginner section or if like in this case it is OK to post in a section that is more specific to my question.

I have the cable that lets me change two 3S packs in series as if they were one 6S pack. It works well as long as packs are same mA and at approximatly the same state of dischange when I start charging them.

Recently a new plane has me now using 4S packs. I'd like to find a similar cable but search is not being my friend. Maybe no one makes one for sale?

If I can't buy one is it possible to buy two of the required 4S connectors and one 8S connector and make my onw? I know how my 3S to 6S is wired because when I received it I had problems right at first until I discovered it had been miswired by the manufacture. Once I swapped a couple of the wires around it has worked great.

Thanks,
My new Cellpro 8 charger will charge 8S batteries, but the price. Yikes. (IMHO, worth every penny though)
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Old 03-07-2011, 08:10 PM   #5
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I guess it would have helped if I had mentioned that my charger will charge 8 cell packs. It isn't a cellpro (can't afford the hobby at those prices) but it will charge 8 cell none the less.

I'd studied my cable that charges two 3 cell packs like one big 6 cell pack enough that I beleive I can make one for charging two 4 cell packs like one 8 cell pack.

My real problem is where to purchase the connectors. That is where search is letting me down.

I need one 8 cell connector like you would find on an 8 cell battery pack, you know the one that would plug into the charger.

Then I need two 4 connectors like the ones typically found in a battery charger that would accept a 4 cell battery pack connector.

Where does a guy buy this type of connector and what are they called?
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Old 03-07-2011, 10:01 PM   #6
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Originally Posted by DanWard View Post
I guess it would have helped if I had mentioned that my charger will charge 8 cell packs. It isn't a cellpro (can't afford the hobby at those prices) but it will charge 8 cell none the less.

I'd studied my cable that charges two 3 cell packs like one big 6 cell pack enough that I beleive I can make one for charging two 4 cell packs like one 8 cell pack.

My real problem is where to purchase the connectors. That is where search is letting me down.

I need one 8 cell connector like you would find on an 8 cell battery pack, you know the one that would plug into the charger.

Then I need two 4 connectors like the ones typically found in a battery charger that would accept a 4 cell battery pack connector.

Where does a guy buy this type of connector and what are they called?
First the good news. Places like www.digikey.com or www.mouser.com likely has them.

Bad news, they have thousands of DIFFERENT connectors, you've got to find the right one.

Hopefully one of the wattflyer readers can recommend a hobby type supplier that can provide what you need.
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Old 03-08-2011, 01:48 AM   #7
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What charger do you have?

Most all the ones I know of will be using two separate connectors for 8S packs.

I dont know if anyone is still making packs over 6S with a single connector. All the ones I can think of are useing split packs over 6S with dual connectors for the balance taps.

You need to start with the charger, find out what it is expecting for input and go from there.

I think I need a signature.
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Old 03-08-2011, 02:15 AM   #8
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Originally Posted by Larry3215 View Post
What charger do you have?

Most all the ones I know of will be using two separate connectors for 8S packs.

I dont know if anyone is still making packs over 6S with a single connector. All the ones I can think of are useing split packs over 6S with dual connectors for the balance taps.

You need to start with the charger, find out what it is expecting for input and go from there.
My Cellpro Prolab 8 can charge an 8S pack with balancing, per page 64 of the Cellpro manual.

The model for this setup uses a 12S2P A123 pack, configured as a pair of 6S2P packs for charging, and a 12S2P pack for flying.
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Old 03-08-2011, 02:32 AM   #9
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My two Power Lab 8s can balance charge up to 8S each as can my icharger 308B and my TP820CD can do two 8S at a time sperately and my iCharger 3010B can balance charge up to a 10S however as Larry stated most packs 6S and above are now split.

Thunder Powers over 5S have always used two balancing leads even before new shipping regulations forced the vendors into splitting packs to get around shipping regulations.

Hyperion charger use to be max. of 5S then max. of 6S then max. of 7S.

Charles
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