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-   -   Charge Multiple batteries.. (https://www.rctech.net/forum/radio-electronics/729511-charge-multiple-batteries.html)

Racerz27 05-12-2013 08:39 PM


Originally Posted by Dave H (Post 12145368)
That's why it's important for the batteries to be at a similar voltage, a similar charge state, before connecting. Good practice to check each before charging every time.

There is a new type of paraboard, that appears to be one but I'm not sure, that has polyfuses to help in the case of a brain dump. But still best to not get in bad habits.

My paraboard is 3 fuses on the top each that say "40" on top. and another fuse on the side where the red and black wire comes out that says "50" on it. Is this what you are referring to?

Racerz27 05-12-2013 08:48 PM


Originally Posted by Dave H (Post 12145540)
Bingo!

(Well except for the charger limit detail, isn't it a 20 amp max charger? But you have the battery thinking part right)


It would be a 20,000mAh battery, yes.


No, you would be able to. It's not a 6 cell total limit, it's only a 6 cell in series limit. All four of the 3S in parallel are still just a 3S to the charger.


ohhhh ok got it. And yes, I forgot my charger is limited to 20amps. Sooooo 350*80%) divided by 12.6 = 22.2max amps. BUT, my charger will only do 20 since that is the chargers limit. So basically just set my charger at 20amps, 10,000mah when im charging my two 3S 5000mah batteries. So it would be charging 10amps per battery. (double what I was getting before on my cheap charger only doing 1 battery at a time :lol:) ha

Edit. Ignore the mad face at the top of this post. Not sure how that got there, nor do I know how to get it off now. haha. Time for me to go to bed, all this is making my head hurt. Finally got it all figured out tho. Thanks Dave!

Dave H 05-12-2013 08:49 PM


Originally Posted by Racerz27 (Post 12145546)
My paraboard is 3 fuses on the top each that say "40" on top. and another fuse on the side where the red and black wire comes out that says "50" on it. Is this what you are referring to?

Yes, I believe the whitish ones down on the board in the rows of 3 are polyfuses to protect the balance connections. Those will reset on their own once they cool I think it is.

The red ones sticking up are for the main large wires, those I believe are automotive type fuses that you would need to replace. Suggest picking up a small container of them to have on hand. (if you have them you won't need them, Murphy's Law! lol)

Dave H 05-12-2013 08:51 PM


Originally Posted by Racerz27 (Post 12145570)
ohhhh ok got it. And yes, I forgot my charger is limited to 20amps. Sooooo 350*80%) divided by 12.6 = 22.2max amps. BUT, my charger will only do 20 since that is the chargers limit. So basically just set my charger at 20amps, 10,000mah when im charging my two 3S 5000mah batteries. So it would be charging 10amps per battery. (double what I was getting before on my cheap charger only doing 1 battery at a time :lol:) ha

Edit. Ignore the mad face at the top of this post. Not sure how that got there, nor do I know how to get it off now. haha. Time for me to go to bed, all this is making my head hurt. Finally got it all figured out tho. Thanks Dave!

:nod: As long as your lipos are rated for 2C, which most are these days.

meno1103 05-12-2013 08:51 PM


Originally Posted by Racerz27 (Post 12145439)
ok, I see what your saying now. I think im getting the "in parallel" and "in series" confused.

For some reason I just assumed since Having two 3S batteries plugged into the paraboard that the charger would think 6S total and charge to 25.2v instead of 12.6

So in theory, (minus the whole, being limited to 6 cells charging becasue of the way i have it set up) I could be charging Four 3s 5000mah batteries at once and it would still technically be (350watt*80%) divided by 12.6 =22.2amps total. But then I would have to divide that by the 4 batteries being changed and that would only be 5.55amps for each battery charging right? I think im starting to get this.. ha

Edit. for my example above, If I were to be doing that, I would have to set my charger to 20000mah right? Again, I know I wouldnt be able to do that since im limited to charging 6 cells at once, its just an example.

The way I see it (and someone please correct me if I'm wrong)
:
You are only limited on the number of packs you can charge at once by the board you use, which I see connectors for four packs.
You should be able to charge up to four of any cell count from 2s to 6s simultaneously.
The math comes in to play when you try to figure what max charge rate you can set for a given number of packs, and cell count, the limiting factors being the max wattage from the power supply, max charger charge rate, and lipo battery c rating.

Racerz27 05-12-2013 08:54 PM


Originally Posted by Dave H (Post 12145583)
:nod: As long as your lipos are rated for 2C, which most are these days.

Yup, My Gens ace can be charged at 5c max I believe. But I wouldnt ever go that high anyway. I Ordered some SMC batteries as well, I think they can do 3c? not 100% sure. 2c for sure tho. Thanks again!

Dave H 05-12-2013 09:29 PM


Originally Posted by neospud (Post 12145234)
Your charger factors in as we'll.. It needs a certain voltage to reach its rated charge.

Two 3s in parallel is still 3 cells voltage, just has an increased capacity so it will take longer to charge unless you charge faster. I use 4.2v in my calculations so the result I get will work all the way up to full charge.

So my two 3s 1400mah packs would be one 3s 12.6v 2800mah pack if wired in parallel. 1c would be 2.8 amps. 2.8 * 12.6 tells me I need 35.28 watts. Factor in an extra 10 to 20% for power supply efficiency.

Yes, some of the high power chargers require a certain minimum supply voltage to achieve maximum wattage, due to input current handling limits.

Don't know if that applies to this charger. Best I can tell it's spec'd for 11-15V input, it might need something close to 15V, don't know. Generally it's an issue for chargers over 500W and with ~24V input capability, but again just speculation, not familiar with this puppy.

Worst case for the OPs situation, since the 3S tops out at 252W compared to the 300W rating, I'd expect it to be fine in this case with at least a 12.6 volt supply. (252/300 * 15V = 12.6V)

Dave H 05-12-2013 09:31 PM


Originally Posted by meno1103 (Post 12145584)
The way I see it (and someone please correct me if I'm wrong)
:
You are only limited on the number of packs you can charge at once by the board you use, which I see connectors for four packs.
You should be able to charge up to four of any cell count from 2s to 6s simultaneously.
The math comes in to play when you try to figure what max charge rate you can set for a given number of packs, and cell count, the limiting factors being the max wattage from the power supply, max charger charge rate, and lipo battery c rating.

Seems reasonable.

Racerz27 05-13-2013 04:41 AM

Earlier post mentioned the balance board not being able to handle 20amps. How true is this? The wires coming from the paraboard a just slightly bigger than the ones going from the balance board to the charger. There are fuses on the paraboard, but nothing to protect the balance board. Should I be worried about the wires on the balance board? Most of the high amps goes through the red and black wires into the battery correct? How much power actually gets sent through the balance wires?

neospud 05-13-2013 09:39 AM


Originally Posted by Racerz27 (Post 12145592)
Yup, My Gens ace can be charged at 5c max I believe. But I wouldnt ever go that high anyway. I Ordered some SMC batteries as well, I think they can do 3c? not 100% sure. 2c for sure tho. Thanks again!

If you charge one battery at 20 amps, finishing quicker, you can avoid the whole parallel charge fiasco! Some simple logic to consider: If you parallel charge 2 batteries and don't have 2 more batteries to charge while you're running the first 2, your charger would be sitting there doing nothing. You will run the 2 batteries down, then charge them simultaneously and wait for them to finish.

This is the same as having a single battery and waiting between charges only with longer intervals... I like to charge one fast, and run it while charging a second pack. Gens Ace easily handle 5c charges.

This may not be your scenario. I know you have two 3s and two 2s so you can keep your charger busy no problem. Still charging a single battery means you would need to own fewer batteries as long as you could charge them as fast as you drain them.

If your charger is maxed out, you're not charging your batteries as fast as they will allow which to me reduces my time out running my cars. I have one battery that has a 2c max charge rate and it really throws me off...

Just my 2c...

neospud 05-13-2013 09:42 AM


Originally Posted by Racerz27 (Post 12146265)
Earlier post mentioned the balance board not being able to handle 20amps. How true is this? The wires coming from the paraboard a just slightly bigger than the ones going from the balance board to the charger. There are fuses on the paraboard, but nothing to protect the balance board. Should I be worried about the wires on the balance board? Most of the high amps goes through the red and black wires into the battery correct? How much power actually gets sent through the balance wires?

The balance board shouldn't need to handle more than 20 amps or even 5 amps for that matter. The majority of the current flows through the thick +/- leads. A smaller current flows through the balance port. That's determined by the charger's rated balance current.

Racerz27 05-13-2013 09:48 AM


Originally Posted by neospud (Post 12147055)
If you charge one battery at 20 amps, finishing quicker, you can avoid the whole parallel charge fiasco! Some simple logic to consider: If you parallel charge 2 batteries and don't have 2 more batteries to charge while you're running the first 2, your charger would be sitting there doing nothing. You will run the 2 batteries down, then charge them simultaneously and wait for them to finish.

This is the same as having a single battery and waiting between charges only with longer intervals... I like to charge one fast, and run it while charging a second pack. Gens Ace easily handle 5c charges.

This may not be your scenario. I know you have two 3s and two 2s so you can keep your charger busy no problem. Still charging a single battery means you would need to own fewer batteries as long as you could charge them as fast as you drain them.

If your charger is maxed out, you're not charging your batteries as fast as they will allow which to me reduces my time out running my cars. I have one battery that has a 2c max charge rate and it really throws me off...

Just my 2c...

This would work when using my stc truck. But this is primarly for my hpi vorza, which uses 2 batteries in series.

neospud 05-13-2013 09:55 AM


Originally Posted by Racerz27 (Post 12147086)
This would work when using my stc truck. But this is primarly for my hpi vorza, which uses 2 batteries in series.

Ah yeah.. makes sense. thats when para charging comes in handy =P

Racerz27 05-13-2013 10:08 AM

So when im charging 2 batteries that are 5000mah and I set my charger for 10000mah. Does the charger know to keep 5000 per battery or will it just charge until it reaches 10000 total? What if it over charges a battery once its at 5000 and the other isnt there yet?

neospud 05-13-2013 11:30 AM


Originally Posted by Racerz27 (Post 12147136)
So when im charging 2 batteries that are 5000mah and I set my charger for 10000mah. Does the charger know to keep 5000 per battery or will it just charge until it reaches 10000 total? What if it over charges a battery once its at 5000 and the other isnt there yet?

The batteries voltage will equalize when hooked up in parallel. That's why it's important to have fairly close starting voltages. Current will flow from one to the other to equalize. If you parallel charge a 5000mah pack and a 10000mah pack, the voltages will still equalize.

It will charge until the voltage hits whatever your charger is set to stop at regardless of how many mah has been put in.

I'm trying to think of the analogy but can't recall at the moment.

edit: think of it like filling one small glass and one large glass from 50% to 51%. it will take more liquid to fill 1% of the larger glass. the batteries will charge from 4.1v to 4.2v but the larger capacity battery took a larger share of the current to fill that .1v


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