Night Scream

Hi everyone:

I have 2 planes running on battery backers.

But a few people in my flying field told me it was better to connect 2 batteries in sequence and it would save me the need for a battery backer.

How do you put 2 batteries in sequence? All I got told is that they literally put 2 batteries connect them to a Y harness and the follow connection into the main switch.

Doesn't that drain both batteries at the same time? Are there any benefits to this?

Or is there another way to connect 2 batteries in sequence??

ALWAYSPDG

My Feedback: (1)

It is best to use two batteries using two switches and NOT use a Y connector to connect the two batteries. Each battery is connected to one switch. Each REC lead coming from the switch goes to your receiver using two different slots.

Mike

Night Scream

So then the 2 batteries will be connected to 2 receiver channels then..

But will the receiver hold out with both batteries supplying power at the same time?
And both will be drained also at the same time right???

rcairflr

My Feedback: (44)

There will be no negative effect on the receiver and asuming both batteries are identical, they will drain equally.

TimBle

whats a battery backer?

By "connecting in sequence" I assume you mean connecting in parallel.

Connecting two batteries in parallel via a Y harness is not a problem at all. It provides battery redundancy.
Chances of a broken cell creating a problem are reduced but the damaged battery will drain faster.

I have not used a dual switch and each battery into a diffrent channel approach. I am not convinced its as good as it sounds.

Rodney

Two switches (with each battery plugged into a different slot in the receiver) is the most reliable method and also the more efficient, especially on servos that draw a high current. The lead impedance when using a Y connection can be quite high and cause major negative voltage drops at the receiver. Plus, a switch is more apt to fail than a battery cell so having two switches adds a bit of reliability. You must also charge any Nixx battery separately (can not safely charge them in parallel) so the two switches and charge jacks simplify maintenance.

TimBle

Ok I buy the dual switch redundancy but not the voltage drop down the leads. How is a Y harness any different to a servo lead extension? It's not.
The voltagedrop is miniscule over such a short transmission distance. Theres a bigger voltage drop through a switch and plug than along the wires. More switches = more resistance
Y harness will have 2 plug connections same as a 2 switch arrangement so the 2 switch system will have a higher voltage drop.

save for switch redundancy (and complexity and weight) I'm still not convinced of two switches being a better idea. I will admit to liking the ability to have two charge jacks though, that is sweet.

I use heavy duty switches anyways, whats the failure rate on those? at my club theres probably over a century of flyng experience and the number of switch failures can be counted on one hand. Thats tells me switches fail very rarely.

Some good advise I was given is too use silicone rtv between the fuse and switch when mounting to damp out any vibration.
That and to never charge your batteries in the airframe, no matter what type they are.

I have mailed Futaba and asked if they see an issue with the two switch arrangement. If not then I'll give it whirl.

rcairflr

My Feedback: (44)

It's very simple. With a Y harness you still have a single point failure and you have 2 batteries pulling the load thru a single 22 awg wire. Which may be OK on a small glow powered airplane, but definitely not OK on a giant scale gas airplane.

pilotpete2

The "Y" harness creates a single failure point for the two batteries and switches.
If an open servo port is not available, then "Y" one of the battery leads with a servo.
Pete

nicelife2010

Are u sure for that?

BarracudaHockey

My Feedback: (11)

Yes he's sure. He's also correct. Personally I would do it with the throttle servo.

Flyfast1

My Feedback: (1)

I fly large warbirds (20-40lbs) and on all my planes for receiver/servo power I use two batteries (same voltage and capacity, even though the same capacity is not required) through two separate switches into two ports on the receiver. Since I use all channels, I have to use a Y-harness for one of the battery lines. I usually "Y" one of the battery lines into either the throttle or air valve servo for the landing gear.

My understanding of at least some of the battery backer type circuits is that the circuit selects the battery having the highest voltage. Thus, the circuit is switching back and forth between the batteries. If true, this would appear to be inferior to using two batteries through two switches into two ports, because the servos and receiver could not draw from both batteries simultaneously. Having two battery packs electrically connected at the same time reduces the effective resistance of the packs.

I use heavy duty switches and in the years that I have been flying, actually had one fail. It was on my power line for the ignition on my P51. The engine died and I had to deadstick the plane. Afterward on the ground, I could jiggle the switch with my finger and cut the electrical contact. I use an optical ignition cutoff with an LED and could see the LED turn on and off when I jiggled the switch. Replaced the switch and everything was fine. In my experience, good quality heavy duty switches work well, but they can eventually fail, especially on a big gasser with lots of vibration. So, I'd rather have two switches than just one supplying power to the receiver.

-Ed B.

Charlie P.

I have one model rigged with a Smart-Fly battery combiner. I use two HD switches (between the batteries and the combiner) and that has two "out" leads, so I can use the B receiver input jack and I "Y" the other lead into a servo jack. The combiner draws from the pack with more remaining mAh, and will also cut a closed-circuit failed pack out of the circuit, preventing the possibility of a voltage draining short.

It also prevents a strong battery wasting itself by trying to charge/equalize a weak one. I don't believe this would normally be an issue with similar packs, but we are talking "what ifs" should one fail or partially fail.