Running 2 11300MAH 3s LiPo batteries in a stock Traxxas Spartan, Bad Idea?

[Bird_dog92]

So I am new to R/C and shortly after purchasing my Spartan I wanted a 2nd set of batteries so i could swap them out while the other set is charging. I bought the boat and 2 7600MAH SMC 3s LiPo's and was very happy with the performance and run time. I went to the same hobby shop and they were out of the 7600 so I bought 2 11300 thinking it wouldn't make a difference. I didn't do any prior research and the guy at the shop basically told me it would just give me more run time. I only had a chance to run it one time last year on the 11300 and I was very pleased with the stability and handling with the added weight but I think it overheated and went into thermal shutdown. After it cooled down I ran it with the 7600 which was fine until it went airborne and flipped and submerged the ECS for about 45 minutes until i could retrieve it. And I believe the ECS is done (box wasn't sealed with silicone where the wires enter the box) I haven't tested it since then to see if it's functional because i don't want to charge up the batteries and not use them if the ECS is fried. But Anyway my main question is whether or not it's safe to run the 11300MAH once I get the ECS issue figured out?

[fweasel]

Those batteries are a good bit heavier so run them as far back in the hull as possible to affect the center of gravity as little as possible. You were likely running with more of the hull in the water because of the extra weight, which puts more load on the motor and ESC, which means heat. We call that running wet. You might still have a center of gravity too far forward, even with those packs pushed all the way back. Ideally, a V-bottom hull will "air out" and run with just the last few inches of the hull in the water. It's much faster that way, less drag, and easier on the electronics. It's also easier to flip. You may have been running the two smaller batteries to far back, and didn't have enough weight forward.

The other problem with large packs like those, is the increased run times can build up more heat than the cooling system can dissipate. If I remember correctly, the stock Spartan came with a restrictive silicone cooling jacket on the motor, which isn't ideal either. As for testing the ESC, the battereis don't have to be fully charged to test the ESC out on the workbench. Batteries at storage voltage will spin the motor just fine assuming the ESC is in working condition.

[Bird_dog92]

I run the 7600mah as far forward as possible but it still does back flips even in every calm water. would adjustable trim tabs help alleviate that? I also have a aluminum cooling jacket and dual water pickup rudder i will be installing soon so I hope that allows me to run the 11300 batteries, otherwise they're just a $300 flammable paper weight. Do you think with the big batteries further back and some trim adjustment id be able to plane enough to keep the motor and ECS from overheating? Or is there a way to remove a few cells from the batteries and make them lighter?

[Bird_dog92]

Also correction I don't think it's the ESC that's bad its the receiver, After being submerged I opened it up to dry it out and there was corrosion on the circuit board and it was blinking red and the ECS wouldn't go through it's normal start up procedure.

[Bird_dog92]

Ensure that the ECS is properly sealed and protected from water ingress. Once the ECS is functional again, you can try using the 11300mAh batteries, but keep a close eye on temperature levels and monitor the performance during operation.

slope

It was the receiver that got wet, I fixed that. But as far as performance goes I loved how the boat handled with the extra weight from the big batteries, and it didn't slow it down to any more than i was able to notice watching it. But it did have a thermal shutdown. not sure if that was the extra weight? But like I said it handled perfectly and I was able to go fast without it chine walking and trying to flip backwards. And now the 11300mah are my only batteries left, I checked out my other set of batteries (7600mah) and one is swelled up so they are done. and I really want to put the 11300 to use because I paid $300 for them and only ran them one time for until the boat overheated. I was still running the stock cooling jacket and have upgraded to an aluminum with fins that covers more of the motor, But I don't think that is going to help mitigate the heat. I just don't know anything about the theory involved with electric boats, when it comes to props, trim, stinger angles, motor KV, ECS ratings and thermal management. Also it's hard to check temps because I have to tape the hatch cover on because It flys off when the boat gets squirrel and spins out or backflips, is there some kind of onboard temperature reading device i can install?

[Xrayted]

Don't waste any time replying to "richie". That is a fake spammer account using AI Chatbot to make replies. Its also posting hidden gaming URLs within the replies, which is what all of these spammer accounts do, and there is one to the far right of his reply that can only be seen well when using dark mode

[Bird_dog92]

Damn that sucks I was excited someone actually replied to my thread. R/C boating sucks I have $500 worth of useless batteries and a boat that thinks it's an airplane. And just bought a brand new gas boat that i paid $1500 for and got a defective engine that doesn't run.

[Xrayted]

Yeah, most hobbies can easily turn into a black hole of spending, and RC fast electric boats are up with the worst as we are pusing things to the ragged edge at all times. A gas boat that can easily cruise around for 20 minutes a time without overheating sounds like it may be a better option for you, so hopefully you can sort out the engine issue. Hopefully you can get it replaced if its a new purchase from a reputable source?

[Bird_dog92]

Yeah they are having me mail the engine back and see what's wrong with it. But I still like my spartan I just don't understand why there's no solution to allow me to run the 11300 MAh batteries, the boat planes just as good as the smaller set, People run electric motors in way bigger, heavier boats, with larger props and don't have issues, why is a few ounces of batteries impossible to mitigate thermal overload on a boat this size. If I need to put a different motor, ECS, and prop on it I have no issues doing that, but i just don't know what it needs.

[Xrayted]

Basic physics unfortunately. More weight = more current to move it, and unlike a gas model, the model doesnt get lighter as the batteries drain. The bigger, heavier boats you are comparing to are using much larger diameter motors than you are as well, so its not a black and white simple comparison like you are making it to be.

Larger motors make more power, but can also handle a lot more current without overheating as easily as a smaller motor will simply due to the larger mass. You will need to find the prop combo that will allow your boat to run for a longer amount of time with the bigger battery/heavier setup on your smaller, stock motors without overheating, and this takes time and a lot of experimentation. Its the same for everyone in this hobby.

It took a few months and about 6 different props before I finally found one that was the perfect heat racing prop for the mono in my avatar image. It can run 55-60 MPH for an entire pack without overheating, whereas the other props I tried, even slightly different could end up with desoldered connectors within 2 minutes of running.

Its a very fine line of balancing what your electronics can handle. I also run the largest water outlets I can get vs the tiny little restrictive outlets that come on most RTR boats. Also, both the ESC and motor have their own water pickups, so no sharing of water exiting one part into another, and also running the largest diameter water line I can

Its also counter intuitive, but running your boat slowly will heat the electronics up faster than wide open will. All brushless motors/ESCs are most efficient at 100% duty cycle. Running at 50% throttle for example is the absolute worst place to be, because ripple voltage is the highest at 50% PWM, and ripple is an electronics killer. Things get very hot and can burn because the ESC caps can no longer handle the ripple.

Many have no understanding of this concept, so they overheat or burn their boats down running around at partial throttle all the time. If the boat is too fast at 100% throttle, then it needs a lower KV motor so it can be run at a higher throttle out value

[Bird_dog92]

For my set up would you recommend as a starting point, should i try a smaller diameter prop with less pitch?

[Xrayted]

Im not personally familiar with your specific boat, but hopefully someone with a Spartan can chime in, but yes, you will likely need a prop with less diameter, pitch or a combo of both if things are getting too hot from running too long. There are a lot of vids of many of the different RTR RC boats all over You Tube, so I imagine some of them are non stock props on them for a starting point.

Just be careful, as many of the vids are all about straight line speed values (SAW runs) and that would be the opposite of where you need to be going with the props