Say I have 2 battery packs of 6 volts each. It is possible to have them wired in series for 12v and in parallel for 6v at the same time?
I know I’d need some sort of bridge to separate the segments so that they wouldn’t loop back on themselves (and I’d assume they’d all become 6v).
If you can figure out a way to connect two batteries so that they are both in series and in parallel at the same time, without drawing a dead short, then you’re better at physics than I am (or at least have put more thought into it than I have).
If you’re just looking at a way to supply both 6 and 12 volts to a robot at the same time from a common battery pack, that’s considerably easier using regulators, though your available power might be limited. If you need 12 volts for drive motors and 6 volts for electronics, then a 12-volt configured battery which is then regulated to supply the 6-volt electronics may well be your best bet. If you only need a little bit of current on the 12-volt side (to supply just one small module, for example), then 6-volt batteries and a boost regulator may work to provide the higher voltage that you need, though this approach doesn’t yield a whole lot of current at the higher voltage.
Without actually knowing why you want both 6 and 12 volts at the same time, and how much current you’ll need of each, it’s kind of difficult to come up with a meaningful answer to your question.
You can have a series/parallel battery configuration but it will not provide what you are looking for. Separate batteries or one lager battery with a regulator as Semus suggested might be the best option. More detail would yield a better solution though.
If you have 2 6 volt packs wired with a serial harness it is possible to tap into just one of the packs before the harness and have a 6 volt and 12 volt supply. However this is undesirable since you will be draining one pack faster than the other and the 2 packs will “try” to stay balanced while wired together.
I have done this with much larger setups. 6 X 12 Volt 10,000mAh lead-acid batteries wired 3 in series and 2 in parallel. This gives you a 36 Volt 20,000mAh pack. I’ve tapped into the + and - terminals on just one of the batteries and ran the 12V source to power something small like a camera or 1 or 2 servos. But they are drawing 250 to 400 mAh at the most which is really very little for a power setup like this. In my case, the batteries will keep themselves balanced and there is no problems.
If I were to power some motors off that one battery, say drawing 5 or 6 amps, then it would drain that one battery too quickly and the other cells would be fighting to balance the capacity in the cells. I would be basically creating a dead cell in my pack which would damage then entire pack or render it useless, eventually.
So if you are talking about using 2800mAh or 1800mAh sub-c cell battery packs, I would not recommend “sniping” power from one of the cells or packs in your setup. Running packs in series and parallel is the most efficient when all the cells are balanced exactly. The farther apart their capacities get, the better chance you have of ruining your packs.
Once you wear down that one cell or pack, it can no longer hold the charge that the rest of the packs are try to give it to keep balanced. If these were lipos, that cell would already be swollen or on fire.
I would use a voltage regulator if you are using smaller cells. It will be more efficient and your packs will last longer.
Something like this would work perfect:
lynxmotion.com/Product.aspx? … egoryID=48
I thought I would jump in here on this slightly older thread as I am trying to decide how I want to configure my new rover.
Suppose you had a 4wd rover, which has 4 motors requiring 12V and you built the rover with two 2800mah 6v battary packs wired in series to provide the 12V. Now suppose you add some servos for pan and tilt, maybe an arm and an Atom pro with some sensors, all of which want to run with 6Vs.
My first thought was to try to tap in between the two batteries for the six volts, but when I diagramed it out, it looked like I would probably need some form of diode to make sure the current will only go one direction? Is this correct? I did purchase the Adjustable HD Regulator MX-06 which I was planning to use as the web site said that it was good for 4.8 to 16vs, however when I received it (Mpi ACC234) the documentation shows voltage as 4.8-8V. Would you suggest using it anyway? Other suggestions?
Thanks
Kurt
How much current do you need?
If you are pulling well under 1 amp with the servos and atom, then you will be fine with no diode.
If you will be drawing more than 1 amp I wouldn’t recommend tapping into one of packs while they are wiring together. You will wreck both packs because they will constantly try to balance out. You can only snipe power from the middle of a pack if you are drawing a very small percentage of the packs capacity.
Over an amp would eventually wreck the pack it is attached to.
Probably not a whole lot, some of these numbers I am guessing, for example the HS-422 uses 150ma with no load, but what does it use with minimal load? Maybe 250mA
Pan/Tilt servos: 2 HS-422 with little load (1 very light camera):
~250ma * 2 = 500mA
Little Gripper: 2 HS-422? again 500mA but probably not much movement at same time as Pan/Tilt
Basic Atom Pro: did not find how much the BAP requires, but the mini ABB regulator supports up to 250mA? Assume 250mA, for electronics including sensors.
Hitec RC Receiver: ?
So rough guess is maybe 1 to 1.5 amps max and probably on average probably well less than .5Amps. Note some of this hardware is in a pending sale otherwise I could hook it all up on my digital multimeter and maybe get some more precise estimates.
What do you think?
That would be pushing it. It will work but there is a change that your battery will only take maybe 10 or 15 more charges before it has a dead cell or simply won’t hold a charge anymore.
Remember that when you are drawing capacity from one pack it is basically charging the whole time you are using it. It is the other pack charging it, trying to balance the voltage and capacity out so they are equal. So the more you draw, the more the pack charges while in use, Draining it’s life, and the more the other pack is trying to give capacity to the other, also hard on it.
You can try it but I would guess it will dramatically shorten the life of both packs.
You would be much better off buying a cheap voltage regulator. Or making one with 5V regulators.
Thanks, I will try out the Adjustable HD Regulator (MX-06) that is sitting next to me to see how well it works.
I will borrow the AP from my hex and try to set it up as I probably won’t receive the one I ordered yestarday for a week or so… Likewise I won’t have some of the servos until then, but I can at least hook up the RC receiver and the Pan/Tilt, which should at least give me some proof on concept.
Then off to programming. First stage, I would like to intercept and interpret the RC commands from the Laser 6 receiver and some of the time simpy forward them on to the motor controller or servos and other times not… But that is more for a different topic!
Thanks again
For fairly light servo use, like a pan/tilt cam, a 5v 1a regulator can be used (add a diode to the regulator reference ground for 5.7v output).
Try this I use it in my minisumo as a linear regulator for the electronic because they draw over 1A and I need low dropout. It is cheap, not much more than a 7805 at radioshack. I got mine from digikey, but I’m sure mouser of jameco would have it. 3A max so plenty of headroom.
Thanks, I might try the one that spacejunk recommended. But I am unsure of the diode hookup. Electronic design is not my strong point, so which pin of the diode do I hook up to the ground of the regulator? I saw some reference to this in a different thread:lynxmotion.net/phpbb/viewtopic.php?t=3066&postdays=0&postorder=asc&start=15, but after reading this thread I was not sure if this increased or decreased the output voltage.
Kurt
There is a simple schematic at the bottom of the below page showing the setup. Connect the banded end of the diode to the “-” line and the other end to the regulator reference leg. I usually try the radio shack parts first to see if they will work ok before ordering parts. The 1-2 week wait and $5-10 shipping for ordering a single part is a drag.
Thanks,
If the preconfigured module I mentioned earlier does not work out properly, I will give it a try.
I am also tempted to try out the voltage controller that spacejunk mentioned as it can handle 3amps. The 5 pin version of this allows you to set the voltage, by adjusting two resistors. If I calculated correctly, if I use R1=50k and R2=190k I would get 6v output. In this configuration I would need to also provide a capacitor to control the startup and shutdown speeds, maybe something like a 750pF and probably some other standard voltage supply capacitors like a couple of .1 and maybe a 22 to buffer it a little… This may be overkill, but it would be nice to go down to one set of batteries
Thanks again
I would just run it off 5v, because the 3A regulator is strange for stuff like that…
Also be carful that you don’t have much capacitence on the output, it will cause it to occilate because the reg. goes into short circuit mode.
