Electronics question

[Zanix]

So my dad picked up another typhoon hovercraft off ebay, knowing that it was broken. (sigh) beside the point. He leaves it to me to make a working one out of the two we have. The first runs fine except for a torn rubber... bag/whateveryoucallitbottompart. So I swap baggies and it floats like a hovercraft should.

MY QUESTION: So I was wondering, if I wired it so I could attach both 9.6v batteries to the motors- would it be 9.6v + 9.6v = 19.2v = fried motors, or would it be 9.6v * 2 power = 14 minutes playtime instead of the usual ~7.

Thank you.

 

[Syringer]

What's a hovercraft?

 

[fyleow]

It depends if the circuit is wired in parallel or series.

 

[Krakerjak]

You can do this if you wire the batteries in parallel. Same voltage supply but longer Amp/Hours output from the 2 batteries.

 

[Zanix]

this is like the first one I got, cept mine is black

 

[Zanix]

any tips on how I might find out if this is parallel or series? I was thinking about just splicing into the wires just after the connection to the 1st battery...

 

[Zanix]

parallel or series... don't know what I'm talking about, well... obviously..

 

[Krakerjak]

That battery pack has only +/- wires coming so connect the same wires from the 2 packs together and you are in parallel. Is this driven on water or land, or both??

 

[DaveSimmons]

Originally posted by: Syringer
What's a hovercraft?

My hovercraft is full of eels.


look mom, I can google!

 

[Zanix]

Excellent... so my splicing idea should work.

Oh and it goes both. I just tested it with the new bag on the pool last night. It loves it. hardwood floors, cement, short carpet, some long carpet (full battery), water, and if I could get maybe 3 batteries together I could make it fly...

 

[Mark R]

You could connect the 2 battery packs in parallel, and it would certainly work. However, in general it's a bad idea as the batteries may have different voltages due to natural variation.

Potentially one could try to charge the other, and damage it in the process.

 

[Zanix]

huh... now could I attach a couple resistors or something of that sort to prevent the damage?

feels like I'm going to be playing roulette with this one. maybe I better leave well enough alone...

 

[NutBucket]

Simple solution: Swap out the electric lift motor for a gas one. This is a project I've been thinking about (already have the gas motor) but I don't want to cut up my Typhoon. One day I'll break down and get one of new ugly translucent ones and hack that up.

 

[AlienCraft]

Originally posted by: Zanix
huh... now could I attach a couple resistors or something of that sort to prevent the damage?

feels like I'm going to be playing roulette with this one. maybe I better leave well enough alone...

Actually, a simple diode will allow voltage out one way, but not back the other. Get one that is at the voltage you are dealing with. Leave the resistors out of it. There are some Dual Battery schematics around that will help you.
I'll try to dig one out of the libraray this afternoon.
Simply charge each batteries fully and connect in parallel for this type of high demand use.
Discharging fully and then conditioning the batteries will play a bigger role in battery life.
Condtioning involves cooling the battery after discharging and before recharging. You will then be able to discharge/ charge the battery more completely.
Do this once or twice with the battery before recharging. Then after charging chill the battery and then charge again.

I have some RYOBI 12vs that are over 10 years old that still charge great and run the porta driver/drill like nobody's business.

 

[dude8604]

Question: How loud are these RC hovercrafts?

 

[Zanix]

As for mine, about the same level of noise that comes from my case; light buzz of white noise... so comforting....

 

[NutBucket]

Originally posted by: dude8604
Question: How loud are these RC hovercrafts?

They're not too bad. My computer has been louder They are a lot of fun, however

 

[Zanix]

NutBucket: What gas engine are you thinking about using?

I'm googling about looking for things and comming up dry.

Edit: did come up with this though Looks like a 60's concept car

 

[Mark R]

Actually, the diodes are an excellent idea. They will solve the problem of one pack discharging into the other.

However, A motor capable of draining a battery pack in a few minutes will need a lot of current. Additionally, diodes will reduce the voltage available.

If you decide to go this approach, you will need high power diodes - specifically, you should get 'schottky' diodes with a current rating of at least 50A (preferably 100A). They will also get extremely hot, and will need heatsinks. You'd need something like a an ST STPS12045TV which is actually 2 diodes, and is specifically designed for connecting multiple power supplies together.

 

[Zanix]

Came up with this, Link

$14.70 sounds alot for a part, but then again... what do I know. This a good buy?

 

[Mark R]

Lol. That's more expensive than I expected. It's certainly not a good buy.

OK. A pair of these would be almost as good. Link

 

[Zanix]

alright, got two in the basket... wish nutbucket would tell me what gas engine he's using...


are these two puppies going to get real hot? I have alot of customizing to do...

 

[Mark R]

OK. You'd better remove them from the basket, because they're the wrong shape and utterly useless - a) You won't be able to solder to them, and b) you won't be able to attach a heatsink

These are the right shape and specification:
http://www.mouser.com/index.cfm?handler=search.listcategory&Ntt=+511-STPS4045CW&Dk=1&Supplier=Supplier&D=+511-STPS4045CW&N=0


Now, you need a heatsink (I'm fairly sure that this should fit).
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=227891&e_categoryid=80&e_pcodeid=5321

This one should fit.

Now, each of the diodes above is actually 2 diodes - and you could make the circuit with just 1 - but the diodes are only 20 A each and may potentially burn out. If you get 2 they will run cooler, and allow more power to reach the motor.

Don't forget heatsink grease, and some nuts and bolts to attach the heatsinks. (You're probably better off getting these bits when you have the stuff in hand, so you can be sure it will fit).

The only other thing to consider is how to stop the heatsink rattling around - remember that the heatsink will be electrically connected to the diode, so other wires and stuff mustn't touch it.

 

[Zanix]

Mr. Marc R, I took apart the main housing on the 2nd (broken) hovercraft and discovered some diodes that look identical to the ones you just mentioned. Markings: "C3420". Does this number mean anything to you? Amperage or anything? I could get started right now if I could use those pups. Also, do you think an old 486 cooler would do the trick? I've got some thermal paste that I could use to stick those diodes to it. That might look nice on the hood actually... if I could find my brother's digital cam I could click a few pics...

 

[LordMorpheus]

I have one of thems. It hardly has any lift as it is, the second battery would probably be too much for it to handle, weight wise.