willig10

The JR R921 DSM2 receiver that I just bought today has 2 ports for batteries. Can you run 2 batteries at the same time on this receiver? If so what is the max voltage and mah using nickel metal hydride batteries?

Thanks

BuschBarber

My Feedback: (2)

I have several JR 921 Rx's. They are the same as the Spektrum AR9000. They only have one port labeled Batt/Bind, but like most Rx, a second battery can be connected to any Servo port or the Data port. If you have no unused Servo Port, you can plug in a Y Harness and connect the second battery to one side and the servo to the other.

You can use 4.8v or 6v NiMh batteries, but they should both be the same voltage and capacity and each should be connected to a separate Y Harness and charged separately.

The JR Powersafe Rx's come with two battery connectors with blue bullet connectors on the ends.

pdm52956

My Feedback: (1)

I have a 921 in a 50cc Extra and have noticed that with one battery plugged into the batt/bind port, and a second battery plugged into the data port, it draws from the battery plugged into the batt/bind port while the battery plugged into the data port remains at it's charged voltage.

Does the 921 draw from one battery until it's voltage reaches some minimum value and then draws from the second battery? I expected it to use both batteries at some kind of similar rate but that isn't happening.

Paul

BuschBarber

My Feedback: (2)

As far as I know, both batteries should draw down equally. I have only used redundant batteries in one aircraft. One was plugged into the Batt/Bind port and one was plugged into a Servo port, however, I have read that you can use the Data port, as well. Both of my batteries were 6v NiMh and they drew down equally. The voltages for both batteries should be the same.

pdm52956

My Feedback: (1)

That's what I had expected to see but it isn't happening. Both batteries are on their own switch and I always test both before I fly so I know that both batteries are powering the rx, just they don't draw down the same.

I guess I'll plug one into an open servo port and see what happens.

Thanks.

BarracudaHockey

My Feedback: (11)

All the power pins, and all the ground pins are on a common bus, including the data port.

willig10

Ok back to my original question. My receiver says "Batt 1 bind" and "Batt 2 Data". If I want to use 2 batteries say 2 4 cell batteries at 6 volts each or 2 5 cell batteries at 7.5 volts each is this ok for this receiver?

This is my first 9 channel receiver and I just bought the JR 9503 radio. I would like to use redundant batteries in my giant scale cessna 150 I am building.

The manual that came with the receiver and the transmitter manual do not discuss dual batteries. I guess I am looking for someone that has done this before. Anyone have any pictures they can post on their dual battery setup with the R921 receiver?

Thanks
Glenn Williams

pdm52956

My Feedback: (1)

That's what I thought but if that's the case, it doesn't make sense that it wouldn't draw the same from both batteries. Guess I'll try plugging into another channel, like gear, and see what it does.

I can't figure out why, if both batteries are providing current to the rx, they both aren't coming back with reduced voltage.

I just don't want to have it drain one battery thinking that the other should power everything and find out that it didn't! [:@]

pdm52956

My Feedback: (1)

That's the reason I'm asking Glenn. I have the 921 and the 9503 as well and when I set the plane up, I decided to go with a dual battery set up. Each time I've flown the plane, the battery in batt 1 comes back with reduced voltage while the battery in batt 2 is still at a full charge........or very close to it. They don't seem to drain at the same rate.

If the rx doesn't draw the same between ports, and it doesn't "switch" between them, then what's to stop it from draining the first and then NOT draw from the second?

I'm using lipo and regulators but that shouldn't make any difference. Just can't figure it out.............

Sorry to highjack your thread!

Paul

willig10

What happens when you disconnect the battery that drains the most? Does the receiver still stay bound and does it pull from the 2nd battery? Also you do have 2 batteries connected to the receiver correct? I am assuming you have 1 battery in batt1 and the other in batt2?

I am concerned that if I connect 2 batteries either 4 cell or 5 cell directly to the batt1 and batt2 that it might destroy the receiver and then I would be out 169 dollars.

Thanks again

pdm52956

My Feedback: (1)

I have both batteries set up on their own switch so that when I get ready to fly, I turn battery 1 on and test to be sure it's providing power, turn the second one on and the first on off to be sure that the second one is powering up. So yes, both batteries are powering the receiver but for some reason I can't figure out, batt 1 comes back with lower voltage while batt 2 doesn't. It just doesn't make sense to me.

Yes, I have one battery in batt 1 and the second in batt 2.

As for using two batteries, you'll be fine. You can plug them into the rx at the same time and you won't do any damage. Your two batteries should be the same by the way.

Paul

DadsToysBG

My Feedback: (35)

I won't hurt the receiver. Remember two battery's at 6v is still 6v total. What you are doing to lessening your chance of a switch or battery failure> I have been using two battery's since day one one 922 and up. This setup is very common on all GS planes now. Dennis

willig10

Do you have pictures of your setup? I am building a Hostetler Cessna 150. I plan on using either LIPO or NiMh. I want to use dual batteries on the receiver and am looking for the best setup and the most robust dependable setup.

Thanks

Zeeb

My Feedback: (41)

Okay some confusion going on here....[X(]

First point; DO NOT USE 4 CELL BATTERIES or what's more commonly known as 4.8 volt, keep 'em at 5 cell or 6 volt unless you go to either two cell A123/LiFE's or (not my favorite) Li-Ion/Li-Po two cell packs. The R921 can tolerate the unregulated voltage from Li-Ion/Li-Po's but you are limited by what the servos and engine ignition can handle.

Depending on how you wire the thing, you can have dual switches with dual batteries and have outside access to both the Bind and Data functions of the R921 which is how I set mine up so no additional outside port is required to get to the Data port.

The R921 does not have any battery isolation capability like the R922 PowerSafe has so you really need to run matched batteries in good condition and you shouldn't run into an issue with unequal draw on the packs. The one gasser I have setup with an R921 and dual batteries uses dual switches and dual A123's, the power usage is very close between the packs when they get charged. There should be a close relationship between the two as there is a common buss between the two packs through the rx buss so even if a battery gets low, theorectically it should balance with the other pack. Do not use disimilar size batteries on this type of setup and pay attention to the continous output amperage capability of whatever battery chemistry you choose. Don't go cheap on on switches, wires or connectors or it'll bite you when you start playing with this stuff.

JMHO, YMMV.

pdm52956

My Feedback: (1)

This is probably the best picture I have. This was taken while I was installing the electronics so it's not complete.

willig10

Understood. What I plan on doing is using two 5 cell battery packs at 7.5 volts more than likely they will be Hydrimax. I am not well versed in the LIPO batteries. I will use MPI switches on each battery pack.

I was just concerned that using 2 batteries would damage the receiver.

That said is it possible to balance charge the nimh batteries like you can LIPO's? In other words if I am using two nickel metal hydrides on 2 seperate switches must both batteries be charged independant of each other or can you charge them together?

I have the Accucell elite and accucell + chargers.

I have never used a dual battery setup. Thanks again guys

pdm52956

My Feedback: (1)

And that is the reason I asked my question. I'm not confused about any of the setup, just why the rx isn't drawing the same from both battery ports.

Having said that, I'm not running a batt share system here so perhaps that might be why I'm seeing this?

Paul

Zeeb

My Feedback: (41)

Be VERY careful about which NiMH batteries you buy as I noted above, make sure they've got a decent continous amp output capability as there can be HUGE differences between them and price isn't necessarily the determining factor but it's usually a good indication.

No you cannot balance charge NiMH. You can do that with Li-Ion/Li-Po or A123/LiFE's and is in fact the recommended method for those chemistries.

You CANNOT charge dual rx batteries at the same time unless you have a charger which uses "high side sense" and they are pretty rare (yours does not have this feature) or you disconnect at least one battery from the rx during charging. Otherwise there is a common ground between the packs through the rx buss (even with the switches off) and it will confuse your charger leading to false peaking, inadequate charge state and I even know one guy who actually blew up a NiMH battery doing that exact thing. When I asked him why he was doing that his reply was "I've always done it that way...."

Spend some more time on the forums and you'll pick up lots of tidbits but here's an excellent FAQ on the care and feeding of NiCD/NiMH batteries. They have lots of other information on batteries as well and are an excellent vendor should you choose to use them:

http://www.hangtimes.com/rcbattery_faq.html

Zeeb

My Feedback: (41)

In your case, all you 'gotta have is one regulator which is set just a "titch" off what the other one is and it'll do what your talking about. Physically switch 'em from side to side and see if the issue follows the change.

I used to use the BatShare and it's a pretty neat idea, but they're really a current bottleneck for most GS stuff since they cannot carry enough current to support the servo demand. I wouldn't use just a straight BatShare.

pdm52956

My Feedback: (1)

OK, now that makes sense. I did switch battery 1 and battery 2 and after that, battery 2 came back with the decreased voltage instead of battery 1.

So let's assume that the regulator specific to batt 1 is allowing a "tick" higher voltage then the regulator on the batt 2 slot and that's the reason it's drawing from batt 1 and not so much from batt 2. If batt 1, the switch or some electronic component associated to batt 1 fails, it should still draw from batt 2 at that point correct?

Once again Glenn, sorry to highjack!

Paul

willig10

Thank you. The link is very informative. I appreciate all the help. I feel a lot more comfortable now.

Glenn

BuschBarber

My Feedback: (2)

I use LiPo or LiFe packs, with Regulators beyween the Switch Harness and the Rx.I had to connect a Y to the Batt/Bind port because you cannot Bind through the Regulator, but you can through the other side of the Y.

tomfiorentino

Willig10,

I just wanted to share with you that I had a similar 50cc set-up on an Extra 260 where I was using dual batteries into dual MPI switches that were modified for balance charging through the chargeport in the switch (just like you see on the hangtimes website).

Anyway, MPI makes a fine switch and a very nice housing. But it didn't work for my application as I was getting a significant voltage drop even on a fresh charge (A123 chemistry). Guys here on the forum helped me figure things out, but I was fine when I plugged the batteries directly into the receiver (no voltage drop). So, the combination of the MPIswitch and a small HD extension ended up being the problem area for me.

If you are contemplating a new receiver for this 50cc project, take a look at the Powersafe receiver and the softswitch. I changed over to that set-up and it is really, really solid. Ihated to spend the extra money, but as luck would have it, I needed another receiver for a smaller project anyway so I just swapped things around.

If you would like, please PM me. We can swap phone numbers and I would be happy to discuss over the phone the rest of my experience with this as you may find it helpful.

Happy flying!

Tom

harttvboy04

My Feedback: (32)

I fly mainly electrics -

Using the Castle Creations Pro BEC, I plug both available power leads into both battery ports on the RX...If you have one battery that is coming back charged and the other not, maybe it is a good thing that you are running two batteries
I'd cycle you batteries to make sure both are in good health. They should both draw equally. My $.02. Hope all is well!


Chris

willig10

Tom:
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