5s or 10s A123 setup for boat?
 

I'm thinking of building another brushless boat and considering 2 different setups.
I have the A123's ,actually Linc is building me 4 5s packs right now

Should I run 5s2p(4600Mah) with a 1700kv motor or 10s1p(2300Mah) with a 850Kv motor.
Battery setups will weigh the same either way and take up the same space.

Equipment wise the cost is not much different if looking at comparable components for each setup. Motors are the same price either way looking at 70mm Medusa's, and as for the Ecs's
the Turnigy 80Amp Hv is $75 plus &25 for a ubec Vs. the $70 for a Turnigy 120A.
The 80HV is good for 12s Lipo /45v and my 10s A123's are only 33v so theres a bit of head room there.

Any input on which will be more efficient and yield the longest run times, All the guys over at Offshoreelectrics.com seem a little spooked at the idea of High Volt setups so I wanted the opinions of those more versed in big power setups.

Both setups come out at about 42Mph with a 42x1.6 prop 2 blade.

I'd go HV. Efficiency is much higher, therefore temps will be much lower and runtime will increase.

I wouldn't say efficiency is 'much' higher, it is higher yes, but as an example, say if the 5s2p system was 89% efficiency, then the 10s system would be around 90.5 - 91% max efficiency. And you are right, every point higher the % efficiency is, turns up as a noticeable difference as far as heat in the wires a bit, and motors would run a touch cooler, and the runtime will increase, but not noticeably.

But ya, go for the HV setup of course. What are you using to charge 10s A123? Are you going to have them as 2 separate packs charging separately, then connect them in series for running?

I would be charging with an iCharger 1010b (300watt)@10s.
The Batteries will assembled as 5s packs then use a serial adapter to both charge and run the boat.

Right, one pack per each side of the boat?

I'm actually running 5s1p packs in my Villain EX with great results, I have to watch it though!.... when the packs dump, they dump FAST! I get into trouble at times!

Yup 1 pack per side. The boat is an Aeromarine Titan 29
http://www.offshoreelectrics.com/pro...?prod=Aero-T29
I know what ya mean about fast "dumpage" a low charge pack dips quick in the water.
I have a Villain that I still run on 12 or 14s NiMh with upgraded props,its a fun boat that wife or friends can try out.

I mentioned Medusa 70mm as motor choice but how would a Kb 45 compare,anygood for this setup?
A big difference in price.

Yeah from experience, when A123's are done, they're DONE. And they wont give you much warning either.

I have no experience with the 70 mm medusa, but it should perform close to a 1515... Now I do have experience with the kb45 motors, and considering you will be water cooling the motor I would go with the kb45xl, maybe the 10xl-11xl on 10s a123? Big motor, with big power! I ran a 1/8 on road car geared for 50mph with a L can kb45 and it performed very well, at least as good as a 1515, so the xl should perform as well as a 1521. They are 2 pole motors, and they will not run as efficiently as a neu, but water cooling will keep the heat down, and you cannot beat the price, get 2 for the price of that 70mm medusa, and it will put out more power. Hope those a123 cells can handle it... Maybe go 2p (use all 20 cells).

I know, I have been running them for 3 years now, and I can barely read their warning signs, which are almost non existent.

Did he get 2 dewalt packs, or one of the '20x A123' eBay items?

If your referring to me I got them as A123 Systems 2s2p packs, buy 4 get 1 free. If i recall they were $48.00/pack brand new.

And they are sitting in a box waiting for me to get them built into 5s packs... I should have some time this weekend, and I can sit in the a/c in my office and build these. Damn a/c in my hobby room is acting weird, need to take the heavy beast off the wall (huge 70's 2 ton window unit!) and have a look at the internals. Maybe it has seen its day? I have a couple of the split systems waiting for me to install them, but maybe I can con my buddy into doing it for me, he does a/c for a living.

be careful with those cheaper escs boats can be real amp hogs, if this your first boat i dont

Honestly, I highly doubt this is the case. Most guys there run boats that are setup to spec. N, P, Q classes, etc... They are listed as to which battery setups are used.

Have a look at this chart:
http://www.castlecreations.com/suppo..._boat_apps.pdf

This is a helpful tool for boating.

Honestly, I don't think A123's are worth there salt in boats... Most setups require high quality Lipo cells as boats can pull SIGNIFICANTLY more amps than the car world. For instance, most people that run 1515/1Y use a Hydra 240 because the amps spike up pretty high continuously. Its also very easy to use the wrong prop and burn up something in a heart beat.
Also, most FE boating setups only get 3-7 minutes of runtime. I would want to most mAh available.

Now on to your setup...

Aeromarine Titan 29, a beautiful mono with the ability to take a decent chop. In order to make boats work properly, you want to spin 28-33k rpm's. SO if you're insisting on pushing a 850kv motor, 10s will be necessary.
Honestly speaking tho I would opt for the 5s2p setup for not only more available amperage, but more than likely, more runtime.

Motor choice: The KB45 1700kv would be a great choice, KB's seem to be a hard to beat motor in boats when properly used. However, a Feigao 11XL would work just as well in this hull. This 29" hull doesn't really require more than a feigao 9XL for power. A 10XL would be optimal.

I don't know your asperations for the boat but for anything over 30mph I would run a Feigao 11XL on 5s2p, with a X445 prop. Should be a reliable setup with those A123's being the weakpoint...

Enjoy.

If this helps, here is an Eagletree of my Villain EX on a hard run. After the pack has dumped, there being no airflow through the hull, the pack temps usually around 115F. That being around a 10 min runtime, or 6C average discharge, which is quite a bit. They are still preforming like day one though, discharging over 2250mah. I would say it clips along the water at up to 22mph? Give or take 2mph.

IMO, boats are a good use for A123's... as there is not much "peaking" in currents, more of a constant current relatively, so you can design a setup around your discharge currents and calculate your voltage drop, and adjust your setup accordingly.

EDIT: OOPS, almost forgot the eagletree graph.

Ok, let me rephrase my words.

A123's are ok in a boat. However, Quality high capacity lipo's are a must in Fast Electric Boating.

A Titan 29 would be a waste at speeds of 22mph... Buy Villian or Kyosho for that.
The Titan is a very capable boat and loves to run 40-45mph in light chop. I would run a 4s2p Lipo setup with a Feigao 10XL and a X445 prop and see low to mid 40's all day. Or maybe a 1515/1Y on 4s2p Lipos with a X442 of X640 and see 50's all day.

Actually, I am pretty sure it is 25mph, it is quite fast!

I agree, for fast boating, lipo is probably needed... but then again, NiMH used to be used to extremely fast boats! IIRC, speeds of around 70mph...! A123's are only more powerful than NiMH.

I am not pushing the 5s pack to the limits, and he plans to use twice as many cells, it should be a 1000watt+ setup if done right.

1000 watts should get him close to 50mph if he sets the boat up correctly. I have a bone stock supervee running a modded x642 prop that I got close to 40 with 12nimh cells, and beat 44mph with a pair of 3600 12c 2s packs. I have not had a change to get out again with a new set of 3600 12c 4s packs, wired in parallel for 7200mah. I have a feeling that battery combo will do 50 in the sv, but I doubt the hull will like it much. Not that the hull is in the water at all at those speeds, just the trim tabs and half of the prop.

Yeah, keep in mind, I am pushing the Titans past their efficiency range.... brushless would be a big leap in performance/or runtime.

Well, posting this same question on HV setups another OSE member looking to do a 10sLiPo setup got every response telling him HV is "not needed" or "I don't know" so I basically took this as not many FE guys are running or have experience with High Volt setups.

Since the whole build is around my A123's (because of charge time) I am trying to pick components to work with these cells in a 10s1p configuration.

This is a play boat as I don't have any clubs close by so high 30's-low 40's is my goal.
Plugging in my proposed setup here
http://www.offshoreelectrics.com/conversion.htm on the
Speed Estimate by Use of Voltage & Constant "Kv" table nets me 38mph
with
Medusa 36x70 880kv
10s A123 (33v)
and a X442 prop
should get 3+ min run times with under 15min charge times plus I have 2 sets of 5s Lipo to run as 10s as well.

Yes the 5s2p setup will have more available amperage but it will also consume 2x the Amps for the same Wattage. So how can it get more runtime having less efficiency?

The 5s2p setup you suggest comes out at 37mph which is bang on what I'm looking for just want to know why you feel 5s2p over 10s1p w/lower kv motor?

I think if the A123's in 10s can handle 2000+ watt loads in todays 3D helis
they can hold there own in my reasonable setup.

Is that 2000watts sustained? or bursts?

2000watts is quite doable with 10 cells sure, but I am just wondering about air flow... Example, I ran a 8s1p A123 pack in my lawn mower at 800 watts sustained, and even higher bursts (~1000watts), that lasted roughly 4 minutes, and discharged 2200mah (of 2300mah 'rated'). NOTE: A123 cells sure do put out their rated capacity, no matter the load on them.

Did you take a look at my eagletree graph I posted?

2000watts, I would design the setup then for 2.4v - 2.5v/cell @ ~90 amps. For a 10s pack. Just a quick calc.

Looking at same kv which will pull less amps a 36mm Xl size or a Kb 45Xl?
Looking at things like weight, space and hardware compatibility I'm leaning towards a 36mm can over the 45mm unless the 45 is a better choice in terms of efficiency.

I don't intend on running 2000+watts, just an example of their capability.

I did check out the ET graph,was that on the mower?

For your setup and desired speed the 36mm can xl would be a better choice.

Just piced up a 32" mono and a mean machine cat... Less than 200 bucks for both shipped, and both have hardware... Not sure what I plan to run in the cat, but the mono will get a 14xl on 8s lipo. Most likely going to snag a turnigy hv esc, and I need another 60 amp esc for 3s usage in my mini mogli boat... Plus the big gas boat needs some work on the hardware, dual rudder conversion and fooling with the surface drive... I have work to do. Tomorrow will be a batt building day for gimpy, I have had his stuff for too long....

I knew you thought about me even when I'm not around...:wink:

HAHA, while you are gimpy, I was referring to the OP, sure you know that anyways. I will build your packs as well Harold, but I seem to be out of 3s align taps, will hyperion do? Or do you want to send me some jst xh taps?

hyperion will do.......

just such a perfect opportunity:lol:

Sounds like a really good deal. What is the mono,just curious?
I just picked up a mini. Its a Velocity mono from minicatracing.com cool little boat, supposed to run mid 30's on 3s we'll see I guess.

Linc did you get anywhere with the ThunderPower packs,still good?

I can do that!

Not sure what the mono is. It has some damage, but that is an easy fix. I am going to custom paint the armada...

The minicat boats are good, I know you will enjoy it. I have a 13" mirco from mhz and it runs great with a 4700 28 size motor and 2s lipo. I run a mamba 25, so I even have reverse!

I hope to run her this weekend, need to find a better pond the one I run now is all full of weeds.

Great chart as a guideline for lower voltage setup's but not much help as I'm looking at going HV.

I guess all I really want to know is, is there any draw backs to going HV.
I realize lower volt setups are tried and true and probably even a few buck$ less, but in an effort to put less stress on these cells wouldn't a High Voltage setup be the way to go?

For lowering cell stress, yes, HV will reduce it a small amount, not much.

The system as a whole will be more reliable however (usually), because of less resistive heat losses; wires, esc, motor...

So since I've got one of these kicking around
http://www3.towerhobbies.com/cgi-bin...&I=LXHYK6&P=ML
do you think it will cut it for the 10s setup if I add watercooling or just not enough?

Hmm, that would be pushing the limits of that ESC pretty hard. I don't really know how Kontronik rates their controllers vs. realworld, but I would say a ~80amp continuous controller is what you need. But you never know, you could just try this one out for a while, go easy on it, check the temps and keep pushing it until you are satisfied. Water cooling system just might do it though.

I have one sitting in an e-Raptor converted heli that I'm not using.
I think I'll try it out on a small prop & watch the temps.

yah, do that, cuz with water cooling, you tend to need a less rated current capacity compared to surface vehicles. Try it, and report back with temps, and the go from there.