Guys,

Im using 2 2s Lipo batts to power my rx. 2s 1000MAh connected to powerbox digi switch and the other one is 2s 800mah connected to formeco regulator. Both regulator has 6.0 voltage output. Is this a safe setup? After flying 2 flights I noticed that my 2S 1000mah batt is 70% capacity on BR3000 and 2s 800mah is 95%. Just wondering why my 2s 1000mah lipo drains faster than normal. Need your help guys. Thanks in advance.

<p class="MsoNormal" style="margin: 0in 0in 0pt"><font size="3" face="Times New Roman">First off, 6 volts is perfectly fine for newer version servos.</font>
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Something is not right for sure. My guess is even though both controllers are set at 6 volts, the Fromeco voltage is lower than the Digiswtch so the 800ma pack is not being drawn from (or very little). There is nothing wrong with this. What will happen is you will draw from the 1000 ma pack and only when the voltage drops to the Fromeco voltage; you won&rsquo;t see any draw on the 800 pack. <span style="mso-spacerun: yes"></span></font></font></p><p class="MsoNormal" style="margin: 0in 0in 0pt"><font size="3" face="Times New Roman">
My question is why such a large draw on the 100 ma pack? I&rsquo;m assuming you are running this in a 2 meter plane with normal size servos. I draw about 40 to 50 ma for a 7 minute flight. You might try setting the Fromeco a hair higher voltage from the Digiswitch to have the receiver draw from the 800 pack to see how much it draws.
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One more thing, the size of your packs are way over kill. You are just adding extra weight. I run two 350 TP packs with two Tech Aero controllers and can get an easy eight flights.</font></p>

The larger capacity pack will "feel" a higher load than the smaller pack. Ohm's Law makes it so. Rather than looking at the capacity reading look at what you put back into each pack. Each delivers capacity in proportion to its size so they will reach full discharge at the same point.

I think capacity is not exactly the word you meant to use.
It's more likely a function of internal resistance. The pack with the lower resistance would drain fastest.

The point is that if you use two packs with different capacities they will reach full discharge at essentially the same point. The larger capacity pack will discharge faster, even if they do not have the same IR (which is not related to capacity as far as I know). If you connect a 1,000 mAh pack and a 500 mAh pack to the same load they will reach discharge at the same time. Say it is a 1 amp load, it will take 1.5 hours to discharge the packs. This assumes parallel connection to the same load.

Silent-
Go back and look at what yepe said.
What you are saying should happen to otherwise equal but different capacity packs, but it did not.
IR is a factor independent of capacity (just like you said) that would account for different drains on paralleled packs.

Reading yepe again, the fact is he's not paralleling two packs as we assumed, but using two different regulators with their outputs paralleled.
Probably Portland really has it right.

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Well let&rsquo;s look at it mathematically. Lets say you draw 50 ma per flight and we have equal draw from both controllers (25 each). Keep in mind we are not drawing direct from the packs, but via the controller outputs. If each controller is indeed set at 6 volts, one half of the 50 ma need is pulled from each controller.</p>

So after one flight we have drawn 25 ma from each pack (theoretically). The 1,000 ma pack would (theoretically) now be showing 97.5% capacity remaining (975 / 1000). The 800 ma pack will be at 96.9% remaining (775 / 800). So in &ldquo;Yepe&rdquo;s case the numbers don&rsquo;t add up if both controllers are set to a 6 volt output.</p>

The reality is this all just theory, I use dual Tech Aero controllers with dual TP 350 ma&rsquo;s. Both controllers are set to 6 volts output. After several flights, I always put more back into one pack versus the other. We are dealing with $40 controllers, not $4,000.</p>

Silent-AV8T said it best. You should never, ever go by the percentage left on a volt meter. It just isn&rsquo;t accurate enough. You should fly several flights and see how much you put back into each pack.</p>

The important issue here is we are not pulling direct from the packs. In this type of redundant set up (voltage the same), each pack will see equal current draw. The packs are not paralleled, rather the controllers.</p></span>

Good info from Tech Aero

http://d7kx18lgvr3p4.cloudfront.net/Tech-Tip%200601.pdf

The Tech-Aero shows two identical packs. In that case the load is evenly split as they show. And that is a parallel arrangement. Regulator or not has nothing to do with the connection type. If two packs are connected to a single load then they are connected in parallel. So plugging into two separate ports on the RX or even using two packs plugged into a "Y". All are parallel connection arrangements.

If the capacities are not the same then the load will be different on each pack. Ohm's Law requires this since they are at the same voltage on the RX bus. This is why I asked the OP what he actually put back into the packs. That is the only way to know what he used from each. The resting post flight percentages read off a meter or the charger are not as accurate as knowing the actual capacity replaced.

In theory two "identical" packs on two "identical" regulators should drain evenly. I have a couple of models set up this way with dual Tech-Aero regs and FP 350's and it has never happened, although they are pretty darned close.

Using a matched set of batts/regs removes some of the intangibles, at least in my unsophisticated little electronics mind. If the draw-down is within a couple tenths of a volt after 5 flights, close enough.

What is much more important is to use a battery checker that can check loaded voltage, i.e. voltage with a .5-amp or 1-amp load to ensure that the cells are good, and to check the IR's of the cells when recharging. These checks are the only real indicators of cell health. Unloaded voltage can be very misleading.

Yepe,

Using two different regulators even at 6Volts will not consume exactly the same on two identical batteries, using different regulators and different batteries will make it even more noticeable. Seems normal to me, and have never done that, either identical systems or just one system.

Best regards

guys,
use 2 identical batts 2S 800Mah different regulator. The one connected to power box drains faster 4 6 mins flight battery reading is 51%. The other one connected to formeco is 90% batt capacity and noticed that is formeco regulator is cold, usually this formeco reg is hot after 6 mins flight.

Well, that is different from your first post. In that case I think you are seeing the effects of how the two different regulators are allowing the load to be distributed between the two equal packs. Typically I would use the same equipment for both packs to eliminate this type of situation.

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I disagree. I think he has something more serious than misbalanced controllers going on. If you indeed are using almost 50% of an 800 pack for just four flights, that&rsquo;s 100 ma per flight. Way too much draw. Not only that, the Fromeco controller shouldn&rsquo;t be getting hot after just one flight. It sounds like you have a servo drawing way too much current or you have binding in the linkage.</p></span>

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So I posed this question to Ed at Tech Aero:</p>

I am currently running dual Tech Aero controllers (one switch) and 350 ma packs. I have the voltage set to 6 volts on both. Each pack is drawn down pretty much the same.</p>

My question is, if I leave one 350 on one controller, but use a much larger pack (1,000 ma) on the second controller will the draw be the same on both packs (50% from each pack) or will the draw be greater from one of the packs? In other words, do the controllers draw equal amount?</p>

This is his response:</p>

Changing the capacity of the pack isn&rsquo;t going to change the amount drawn from each, so the smaller capacity pack is going to need to be recharged sooner than the higher capacity pack.</p>

So, at least for Tech Aero units, they indeed do isolate the batteries from the receiver and will draw the same amount from each battery.</p></span>

That makes sense since the regulator is providing the same output voltage. The will be split evenly then and the smaller pack will deplete faster. If there are no regulators involved the two packs will need to be at the same voltage (Ohm's Law) and they will reach discharge at the same point.

In the OP's case I doubt he has a servo messed up or anything. I still think that the Fromeco regulator is not acting right since it is not apparently passing the load to its battery as it should. The other pack/regulator is doing all the work. The load should be split evenly, but for some reason the Fromeco regulator is not doing its job.

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My reasons for thinking he may have a servo or linkage issue is the heavy load on the one pack and the heating on the Fromeco unit. The big draw on the one pack seems just too high. In normal use, the Fromeco controller should never be hot, in fact it shouldn&rsquo;t even be hardly warm.</p>

My guess is the voltage output on the Fromeco is below the Digiswitch and is not being drawn from little if any.</p>

The OP really needs to give us ma put back in not percentage.</p></span>

For all we know, the regs may be going into a Y harness and then to the receiver. I've actually seen this, and the guy doing it believed he had a redundant power supply to the RX.

I suspected a misunderstanding when I read the header "redundant Rx" setup problem.

Until you actually SEE a set-up, sometimes it's hard to tell what is really going on.

Yepe, given the problem you have described and the overheating Fromeco, it would be much safer just to use the one Powerbox digiswitch and a single 800-mAh battery, which is a common set-up with many experienced Pattern fliers. Move the control surfaces around (while on the ground!) to check for binding and to see if the Digiswitch reg heats up.

I wish one of us could be there to inspect the whole set-up in person, but since that isn't possible try to find somebody locally who is experienced with good Pattern set-ups. In any event, I wouldn't risk flying a nice model until I got the issue resolved.

Is he running a YS?

Jim O

Jim, I assume that since this is the electric pattern forum the discussion is in regards to a model with electric propulsion.

Yepe also inquired in other threads about Pletty and Himax and (if I recall correctly) other motors, which also leads me to believe this. However, Yepe could be working with another totally different model and you could be correct.

In any event, as I know you are keenly aware, whether glow or electric an overheating reg in a Pattern ship is a sign of something very wrong.[]

If we assume his data is correct and I'm sure it isn't, he has an average current drain of about one amp. 30% of 1000 and 5% of 800 is 340 in about 1/3 hour is about 1000 per hour. I could see this with tight digital servos and a lot of vibration.

If you read his second post, the Fromeco regulator is now cool whereas it had been running hot. I'm assuming it was running hot when it was by itself handling the full one amp. Their early regulators were only good for 1.5 amps. I don't know if they ever fixed that.

As someone said, it is difficult to troubleshoot without having good data. By the way, the original problem, uneven discharge, is no doubt due to the digi-switch regulator voltage being slightly higher than the Fromeco.

Jim O

LOL, take two Jaccio's and call me in the morning!

Time to start fresh with two good, matched regs and two good, matched batteries...

No, I like the idea of using one pack and having the other as a backup so I set one reg to 6.3 and the other to 6.0. That way you only have one pack to charge. Of course now I run the 6.3 reg off of the balance connector of my motor pack so there is no recharging required for the receiver pack.

Jim O

I'm not opposed to that, however I wonder if the repeated plugging and unplugging of the reg that goes to the battery balance tap might lead to fatigue in the connector.

On the model I'm working on now (almost finished) I am using a high voltatage input BEC (up to 12S) set to 6V with a back-up battery with reg set to 5.75V, with the same idea in mind... stolen from elsewhere actually. My first time with this set-up but it seems sound.

Tell me now if it ain't!!

Sounds good to me. In the old days switching regulators created a lot of RF noise that affected receiver range but I'm sure you checked that out before you flew it.

Jim O