Lipo question

[secrtwpn1]

Two questions:

What does it mean whan a Lipo battery needs to be "balanced"?

Also, how many maH are needed to run a 1/96 sub???

Thanks
Farlan

[JWLaRue]

Farlan,

Balancing is the process of equalizing the voltage of the cells so they are all the same. This to ensure each cell discharges the same amount which maximizes the available capacity of the battery.

There is no simple answer to your question about how many mAh are needed to run a sub. There are too many variables. But to try to provide some sort of answer.....a 1/96 scale Skipjack can probably run for about 1.5-2 hours on a 7.2-volt 3000mAh pack.

Tell us what sub you have, the dive module being used and a better answer may be possible.

-Jeff

[secrtwpn1]

I have a 2.5" D&E cylinder.......

[salmon]

My Gato has a 1100 mAh 3S battery. It gets me at least 30 - 40 minutes of run time (I never have pushed it to the max drainage). Why that battery? I cut my tube to fit and rather than distribute the material removed from each end, I hacked it off one end (the battery end). So, I have a 90mm limit on battery size.
As far as how long, if you drive your sub like a rocket.....your battery will drain quickly. So, my advice, once you have your cylinder installed in your sub and you know the battery end will remain the same, buy the largest battery you can.

[secrtwpn1]

What is the "3s"?

[secrtwpn1]

Also, what voltage should I be looking at?????

[bwi]

I'm with Tom here

But make sure that prior to the purchase of the battery you have installed all the electronics inside and live test everything so you are sure you don't have to swap parts from the aft to the fwd compartment. Then buy the battery with the highest capacity you can squeeze in.

I also have a 2.5" SD
I have a 3600mAh 2s (7.4V) in the fwd compartment, and I have a lot of other stuff in there.







Grtz,
Bart

[salmon]

The voltage can be what you want between 7.4v or 11.1v LiPo. What will the difference be? The pumps will work faster with 11.1v (if going 7.4v you will want to remove the resistor on the pump that is preinstalled) and you have a bit more speed with 11.1v, (The motors and pump are rated for 11v DC) however....I have reduced my Gatos forward speed by close to 50% because there is too much power in the props and motor. So, 7.4v will be perfectly acceptable. Many ESCs (Electronic Speed Controllers) can accept either voltage. No matter what you use, the ESC will probably have a BEC (Battery Elimination Circuit) that will provide the same voltage (5v I believe) to the receiver. With 7.4v you might (MIGHT) be able to double up batteries and run in parallel.

It may be frustrating for some, but there is not one way to stuff your WTC and there is a lot of customization that you can do.

Bart is correct, pick a voltage and build your sub out. Then you will know how much space there is. When I started I bought a cheap 11.1v LiPo for bench testing (also a BEC on the bench) and it helped.

[greg w]

The 3s means 3 of the 3.7 volt lipo cells in series for 11.1
Volts total. A 2s battery is 7.4 volts

[secrtwpn1]

I need a battery shorter than 5 inches. So would I need to double up two short batteries?

[salmon]

You could, but I would find some cardboard and cut out the dimensions of your battery to see if they would fit. Make sure in your 5" or 127mm there is room for wires and connectors to get stuffed in there.

[bwi]

What you have to look at

Voltage related:
for our purpose you can have a a 7.4 or 11.1V battery pack.
On the NDD shop I see they recommend a 11.1V battery pack, so that sorted out.

Capacity related:
Lopo's also have various capacities most of the time this determines the dimensions and weight of the pack.
You probably will see batteries rate with a C coefficient 20C, 15C, that is the constant discharge current the battery can handle.
A 5000mA 40C battery will be able to give a 200A discharge current. This is not important for us, If you have an RC car it will be important but we boaters can neglect this.
I have a battery pack for a TX in my sub, so no worries here.

Dimensions related:
That is your main focus here.
You can have 2 Lithium-polymer batteries wired in parallel as recommended by NDD. They sell the required batteries.
The down side of this that you have to charge two batteries.
Another option requires some sleuthing, find a single battery that can replace the above.
This is the hard way, and some kind of a gamble regarding the exact dimentions.
you know the capacity of a single battery and it rough dimensions. Multiple both by two (except the length and the hight) and you know what to look for.

What I did, when I thought I had found a battery that would fit in the SD, I made a box in cardboard with the dimensions of the battery for test fitting.

Grtz,
Bart

Now I see the last suggestion was already made by Tom

[secrtwpn1]

So, its OK to use a transmitter battery?????? I saw one on Amazon.....

[JWLaRue]

A battery is a battery is a battery. There's nothing special about a "transmitter battery" other than perhaps physical size so as to fit into a transmitter.

As has been recommended, find the battery with the highest mAh rating at the voltage you need to run your sub at that fits into your available space.

-Jeff

[bwi]

This is what I use:

3600mAh 2S 12C Lipo Receiver Pack

I have exchanged the brushless motor for a small brushless outrunner 3800kv motor. Brushless motors are more economical. I reduced the speed of the motor down to 50% else the refs of the output shaft are to high and will burn / wear down the seal of the prop shaft.

It is connected to a dia. 43mm 7 blade prop through the original gearing.

It propulse a 1/144 Akula dimensions approx. dia 80 x 800 mm

All the above together it results in a run time of more the 2 hours. I’m fat up before the battery is drained. Yeah I like the built process more than the actually sailing.

This works for me, I do not run my sub as a semi torpedo, I’m captain slow.