more Qs... Batteries & Run Times

[jmh2002]

Further to my general post here: https://forums.offshoreelectrics.com/...8022#post58022 I have to say Im now in quite a conundrum regarding batteries.

Firstly, Id like to confirm that with 4-5000mah battery packs (whether NiMh or LiPo) Run Time is approximately 6-10 minutes - is this correct?

If so this seems crazy from a recreational (non racing) point of view - over $500 invested for 6 mins use... - but perhaps someone can put me straight there?

So assuming the above is correct, I think I need some guidance. I think I need at least double the above Run Time, at least 20 minutes, to make this worthwhile for recreation.

This would seem to mean that I need to put at least 4 x 4500mah NiMh batteries in at once to give 14.4V and 9000mah overall. This is cost effective (eg: 4 x these: http://www.offshoreelectrics.com/pro...d=ep4500-6cell), but is this going to far from a weight perspective?

To save weight (& only need 2 batteries) it seems Id either need NiMh that are either much higher capacity (say 8-10,000mah each), or that are 14.2V per battery (at say 4500mah each). However, I havent really seen these around?

I can of course solve this by going to LiPos, however to get the required Run Time / mah the cost appears to be 1 to 1.5 times the cost of the boat itself, plus an expensive charger?

I look forward to your comments and hopefully I can be pointed in the right direction - or is everybody running around with $1000 worth of batteries?

THANKS!

[jmh2002]

EDIT: Im more than happy to be corrected, and I know everyone says how great the LiPos are, however on reflection, maybe I have answered this for myself.

The 4 x 4500mah NiMh option (these: http://www.offshoreelectrics.com/pro...d=ep4500-6cell) wired in series and parallel to give 14.4V and 9000mah may be the best overall choice (for my use):

- very reasonable cost
- no need for special charger
- extra weight will help with handling & trim, especially when its bumpy
- the lower COG may assist with self righting?
- everything can be purchased from OSE

So, two more questions (ok, maybe 3):

- does anyone see any problems with this?
- do 4 batteries actually fit?
- will I have any type of heat problem, with either Motor, ESC, or the Batteries themselves, with a run time of, hopefully, 15 minutes plus?

THANKS!

[Eodman]

Hey JMH not to disappoint you but you will never see 20 minute run times with this hobby right now! Reasonable thinkin 5 to 7 minutes once you have it dialed in and thats wide open throttle!

Gas or Nitro running you will but not with Fast Electrics!

Be advised that brushless motors and esc's do not like partial throttle running ... too much heat buildup! And heat is your enemy!!!!

[Eodman]

Also the slower you go the less efficent the cooling system works --- lesss water ruuning thru it! Again ... more heat build up!


But all these things aside - once you get one on the water time is not a factor!

My only suggestion is when you buy your charger step up and buy one that will also charge Lipos ... trust us you will grow into Lipo's

[jmh2002]

So, you are saying that with 4500mah Ill get 5-7 minutes run time (ok, thats within the range commonly quoted on this forum), but with 9000mah I wont do any better?

That doesnt seem to make any sense to me, and tends to contradict many other posts - more capacity should equal more run time - no ?(regardless of NiCd, NiMh, LiPo, or whatever) ?

I dont think I mentioned that I wanted to run partial throttle, in fact probably the opposite - if Im carrying more weight Ill probably being using more throttle.

I do have some thoughts regarding cooling which are mentioned in my other thread.

THANKS! for your input. I look forward to some more replies.

[Eodman]

I'm not sure but lets wait for other more knowledgeable guys to weigh in ... but I don't think the stock ESC will handle that battery set up for that long!

[Doby]

I have run 2X 4S LiPos at 4500 MaH capacity each (9000 Mah total capacity and got about 12 minutes of run time in my SV. Your biggest problem will be fitting 4 packs of NiMh inside your SV.

In one of your abve posts you mention that it should help with self righting. The SV hull is very stable upside down and will not self right.

If you still want to stick with MiMh, run 2 packs, come in,,,replace with 2 new packs and carry on.

[jmh2002]

Im interested to hear your thoughts regarding the ESC, and why it wont handle this battery setup? Can you be more specific?

Obviously heat is a concern of mine, however effectively only because of the increased run time, unless Im missing something?

As far as I understand the ESC would view this battery pack the same as normal, it would simply detect 14.4V at full charge. I dont think the ESC detects capacity does it?

As I said, I am factoring heat as a possible issue, however I am also conscious of the fact that this will otherwise be a stock boat as far as drive train is concerned, and far less aggressive than some boats which are running bigger motors, different props, etc.

Per my other thread I will have the option of running either an increased cooling water flow rate (via a trim tab pickup) or a separate cooling circuit, both of which would result in a lot more flow and therefore cooling ability.

As an aside, I see quite a few comments around the forum in relation to battery heat - has anyone considered cooling the batteries themselves (in much the same way as the ESC is cooled)?

THANKS!

[jmh2002]

THANKS! @Doby

[Doby]

The standard SV controller DOES NOT HAVE A LIPO CUTOFF. Keep that in mind. I run mine with LiPos with no problem but always bring the boat in after about 4 minutes to be on the safe side. I run 3700- 5000 MaH capacity packs. I run the SV controller in a couple of different boats for upwards of 3 years now with no problems. If you are going to run the stock prop and want no heat issues, get an aluminum water jacket. So much better than the silicon one.

The standard controller will handle the 4 packs you are suggesting, but its a matter of cramming and securing 2 packs on each side that will be an issue. Its a tight fit and may not be possible,

I'm running a 9XL in my SV, a "hotter" motor than the stock motor and the controller does not even break a sweat. I would suggest that you do not use the rudder pick up and install a transom mounted one instead, you will get more water flowing that way and keep things cooler.

I have run pack after pack through this setup every weekend, sometimes only stopping long enough to change the packs and never have heat issues.

If you are running in rough water , you will end up upside down, it doesn't matter if its the SV or the BlackJack (I have both ). They are not really rough water boats. TAPE THE HATCH, not just for waterproofing, but to help keep it in place as the cowl lock can pop open if there is enough force put on it.

[ChaKane]

What you may consider is to change the wiring harness over to parallel from series and use a higher voltage battery. Changing the harness over to parallel will effectively add the two mAH together.

eg

2 x 7.4volt 4000mAH in series effectively gives you 14.8 volts 4000mAH
2 x 7.4volt 4000mAH in parallel effectively gives you 7.4volts 8000mAH.

I run my SV in parallel with either 14.8 volt or 22 volt batteries.

[jmh2002]

@Doby: THANKS! for the specifics.

@Chakane: Yes, that is what I was suggesting except using 4 NiMh packs instead of 2 since I havent seen any that are 14.4V per pack?

If these are available, perhaps you can point me in the right direction?

I know everyone will just say 'use LiPos' however, the price is just silly to get any decent mah. With high mah LiPos I think Id be better of buying the Nitro version of the SuperVee.

To be honest, the thought had crossed my mind, but I from what I have read with the Nitro boats you can end up doing more maintenance and tinkering than actually driving the thing...

[Doby]

The Nitro guys are always messing around with the engines and then there is the noise factor,,,,but there is also the smell of nitro,,,,Mmmmmm Nitro ! I do like that !

[eboat]

I have the Super Vee also and if it is run time you are after you will have to use lipos

4 packs of NiMh will not fit in this boat very well to keep the COG (balance point)
It will also add too much extra weight and make it work harder plowing through the water

As Doby said get your 4 packs and just come in and switch 2 at a time

[domwilson]

I'm running a 9XL in my SV, a "hotter" motor than the stock motor and the controller does not even break a sweat. I would suggest that you do not use the rudder pick up and install a transom mounted one instead, you will get more water flowing that way and keep things cooler.

Doby, are you running the stock ESC with this motor?

[Doby]

Wilson; You are alive,,,,excellent.

Yup, I run the same set up in my Blackjack, Llumar and SV, all on 4S. All using the stock SV prop. Its a great combo!

[motoxbob11]

Hey JMH not to disappoint you but you will never see 20 minute run times with this hobby right now! Reasonable thinkin 5 to 7 minutes once you have it dialed in and thats wide open throttle!

Gas or Nitro running you will but not with Fast Electrics!

Be advised that brushless motors and esc's do not like partial throttle running ... too much heat buildup! And heat is your enemy!!!!

I agree completely. We expect too much performance to get long run times from a small electric motor. If you want to drive around for 45 minutes you can get a weedeater motor gas boat. They are great boats.
As far as an SV I run for 5 minutes with a stock setup and a cf 45 prop and 4800 lipos. I takes about 2500 mah to recharge them so I'm not even close to discharged but I like it that way. The fact is we spend a lot more time fiddling with these boats than actually driving them but oh boy is it fun when we do!

[domwilson]

Yes Doby, I'm still alive. It's a good thing too...

Ya think it might work with an x642?

[Doby]

Don't know,,,,,,,try it and let us know.

[domwilson]

But I'm scared.

[domwilson]

How about a x640? an x637?

[jmh2002]

I run for 5 minutes with a stock setup and a cf 45 prop and 4800 lipos. I takes about 2500 mah to recharge them so I'm not even close to discharged but I like it that way.

THANKS! for the info. However this is kind of what I am getting at. If you take the boat out for a even 30 minutes you must have multiple sets of of batteries, no?

So, is everyone running around with $1000 worth of batteries, or? Surely you dont go home again after only 5 minutes use?

[Rex R]

not quite that much in batteries...tho I do (usually) bring about 4-5 chargers :-) (and 2 power supplies), I am fortunate to have 120v availible on site for charging.

[jmh2002]

As far as an SV I run for 5 minutes with a stock setup and a cf 45 prop and 4800 lipos. I takes about 2500 mah to recharge them so I'm not even close to discharged but I like it that way.

Based on the above scenario, which would seem like quite a common set up, am I correct in thinking that to put that 2500mah that was used up in 5mins back into the battery, it would take, charging at 1C / 0.48amps (please correct me on this?) about 5 hours?

Or do I have my maths mixed up?

Is it a good idea to charge them in parallel to double the capacity (even though in the boat they are in series, to diuble the voltage) in order that a higher charging curremt can be used, and therefor a faster charging time (ie: about half the time)?

THANKS!

[Rex R]

at 1c (4.8 amps, darn those slippery decimals) it should take no more than an hour...given usual charging rates(observed) figure about 40-45 minutes to put 2500mah back into the packs.

[jmh2002]

Ok, thanks.

I thought I had my maths wrong.

Either way, it would seem that at least 2 sets of batteries are required, and if they are Lipos, its starting to get a bit on the pricey side $ spent vs fun hours returned, which is a bit of a shame.

Ill mull it over some more I guess.

[motoxbob11]

Yea it is a shame but we are just making sure you know what the deal is. You need a couple sets of packs and hopefully a couple chargers (or a duo) to do it for any length of time

[Doby]

http://s167.photobucket.com/albums/u...lerLake029.flv

Heres a link of mine in some rough water, its fun but you do have to be careful.

[motoxbob11]

Not only careful about flipping the SV but those darn fish keep biting my leg also!
A couple of nice saves there Doby and it really shows how tough it is going into the waves as opposed to running with them.

[Doby]

Running with the waves is a blast, It turns into a submarine a few times.
The saves were from devine intervention, not driver skill.

The fish turned out to be minnows about 3 inches long!