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Re: Battery Advice Needed For Middle School Competition

Posted: Nov 11, 2017 2:46 pm
by DrkAngel
Sonas @ $150 per 100 cells = 4 x 24 cell battery builds

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 11, 2017 4:08 pm
by BlueBell
DrkAngel wrote:Sonas @ $150 per 100 cells = 4 x 24 cell battery builds
OMG, you should see what I get when Googling this!
Can't seem to find Sonas lipo's on-line...

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 12, 2017 4:49 pm
by DrkAngel
BlueBell wrote:
DrkAngel wrote:Sonas @ $150 per 100 cells = 4 x 24 cell battery builds
OMG, you should see what I get when Googling this!
Can't seem to find Sonas lipo's on-line...
Can't confirm Sona cells as 2000mAh ...
Not sure of replacement candidates.

Need:
180Wh ÷ 3.6V cells = 50Ah
12s2p (≤ 2080mAh cells) 43.2V 2000 or 2050mAh
13s2p (≤ 1923mAh cells) 46.8V
14s2p (≤ 1785mAh cells) 50.4V best ... if available
15s2p (≤ 1666mAh cells) 54V 1650mAh cells max recommended
16s2p (≤ 1562mAh cells)57.6V


180Wh ÷ 3.7V cells = 48.64Ah
12s2p (≤ 2026mAh cells) 44.4V
13s2p (≤ 1870mAh cells) 48.1V best ... if available
14s2p (≤ 1737mAh cells) 51.8V
15s2p (≤ 1621mAh cells) 55.5V 1600mAh cells max recommended
16s2p (≤ 1529mAh cells) 59.2V

Reputable possibilities:

Image

Lipo ...
.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 12, 2017 5:18 pm
by DrkAngel
Hobbyking!

11.1V 3200mAh Turnigy LiPo - $20

3s 11.1V x 3.2Ah =35.52Wh x 5 = 177.6Wh

15s LiPo 55.5V 3.2Ah = 177.6Wh


3s 11.1V 4000mAh LiPo

3s 11.1V x 4.0Ah = 44.4Wh x 4 = 177.6Wh

12s LiPo 44.4V 4.0Ah = 177.6Wh

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 12, 2017 9:52 pm
by BlueBell
DrkAngel,

I'm really starting to feel like an idiot here.
Not really sure what you're trying to beat me over the head with.
It looks like four different battery options...?
Is that right?
Is the C-number relevent here or are they all the same?
Knowing our requirements, is there one combination you would recommend over another?
If it's all the same then I would think the fewer number of pieces the fewer connections we'd have to make.
And what about charging?
The IMax B6?
Does that go between the panels and the battery?
What A/C charger were you thinking of or should we just use the panels leading up to the race?
I'm starting to get discouraged here, it seems like I'm missing something... something obvious.
<sigh>

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 12, 2017 11:54 pm
by DrkAngel
Sona 18650 cells may not qualify due to lack of documentation-verification of capacity.

2 different Lipo possibilities.
Higher C rate provides less sag but very high C rate tends to sacrifice reliability-durability.
Under your planned discharge C rate will be less than 3 C, so possibly 20-30C might be optimal.

iMax B6 is for testing, charging and balancing (equalizing) individual 3s LiPo, 4 individual charges for 3s LiPo packs.
Use panels to "top off" battery.
I recommend the 4 x 4000mAh as best choices. 5 x 3200mAh pushes charged voltage to 63V which is the probable controllers capacitor rating-limit. I don't recommend pushing to limit.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 13, 2017 12:21 am
by markz
High Ah trades off Discharge in 18650 format, so 3.5Ah is the highest these days, best guess is 10A discharge. But them 2.0-2.5Ah's can get 25A-30A discharge.

I have not looked at pouches or other formats.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 13, 2017 11:35 am
by 999zip999
I know it takes a lot of energy to get the prop started
So what is the amp draw of the controller and add a few ? So 12s 2p of Samsung 25r cells 25amp cell. Price is going down. Maybe 3.75- 4.00 usd each.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 14, 2017 2:24 pm
by BlueBell
"Sona 18650 cells may not qualify due to lack of documentation-verification of capacity."
Yes, you hit the nail on the head there.
They require documentation of battery specs.
Max 180 Watt-hours

Not sure which Turnigy 4000 you meant.
This one:
https://hobbyking.com/en_us/turnigy-bat ... xt-60.html

How will we ensure 25 minutes out of this set-up?
If we fall short by even 20 seconds we are disqualified!


"I know it takes a lot of energy to get the prop started"
Not really, especially considering the high torque of electric motors on start up.
It takes considerable more power at speed, ~8 - 10 knots ( ~4.5 m/s ).

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 14, 2017 3:43 pm
by DrkAngel
Not sure on the 4Ah RC LiPo.
1. Median C rate, (20-30C for better consistency-reliability)
2. good brand name. Ask others about "good brand name".

Watt meter has watt function.
... think I figured this for you already ...
DrkAngel wrote:2. Watt-watt Hour meters are fairly accurate and inexpensive. If a throttle is used, maximum safe battery output can be regulated fairly precisely!
180wh x 60/25 min = 432w
Should maintain 400w+ battery output for 25 minutes
Important to test drive before actual race.
Keep throttle positioned for determined watt usage (400W?) battery output.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 14, 2017 4:59 pm
by BlueBell
Ah, yes indeed, you did show me that, thank you and my apologies for overlooking it.
I've just read through the thread a few times and believe I'm getting a firm grasp on reality, finally.

So, 25C constant with 50C burst isn't okay?
You pick one. :)

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 14, 2017 5:04 pm
by BlueBell

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 14, 2017 6:08 pm
by DrkAngel
Either look good!
If budget allows, might recommend 2 sets of batteries or at least 1 spare, in case of accident or failure?
Graphene is newer tech with greater reputed lifespan.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 14, 2017 7:41 pm
by BlueBell
Yes, we are advised to have a second battery in case of poor weather and the solar-only heats will run on battery instead.

But I thought you didn't like the first one, the HobbyKing R/C one.
Graphene you say. Perhaps that has something to do with the differing three letter abbreviation associated with the different lipo listings.

Come on, stick your neck out and recommend one... please.
Or your two top picks, then you're not on the hook.
Is the heavier battery, of the same rating, the better way to go?

Thanks again.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 14, 2017 7:53 pm
by DrkAngel

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 14, 2017 8:00 pm
by BlueBell
Lol, ok, graphene it is... even though it's lighter.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 15, 2017 1:39 pm
by markz
With them RC lipo its just like lego, you plug whatever you want together, making sure to pay very very very very close attention to what you are doing. Buying or making a parallel adapter, I used a 5.5mm connector with 10awg that split into six 4mm 12 or 14awg wire, then I bought some 5.5mm bullets and some wire to solder the main wire. Its pretty simple to learn. Then you got to take care in charging and discharging. One day I will buy LiPo again.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 16, 2017 11:26 am
by BlueBell
999zip999 wrote:I know it takes a lot of energy to get the prop started
So what is the amp draw of the controller and add a few ? So 12s 2p of Samsung 25r cells 25amp cell. Price is going down. Maybe 3.75- 4.00 usd each.
Did you mean it takes a lot to get the motor going?
I've been told we may have a problem when running on panels only getting the motor turning due to it's high start-up draw. The panels may drop below the min voltage cut off in the controller.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 16, 2017 11:40 am
by BlueBell
DrkAngel,

I noticed the upper limit on the motor controller is 42.5 +/- 0.5 Volts.
Is this going to be a problem at 44.4V?
This is printed on the controller, the spec sheet differs, same for LVC.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 16, 2017 12:59 pm
by DrkAngel
.
...
Edited!

Better contact seller to confirm!
States 36-48V capable! ... ?
Very often 36V controllers have no HVC (High Voltage Cutoff) 42.5V might be hypothetical?

42.5V upper limit would be bad for 44.4V or from panels!
~31V LVC with 44.4V ≥ 50.4V charged capability required.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 17, 2017 11:20 pm
by 999zip999
42 volt is 10s fully charged.
Ok srill guessing 42v fully charged x 42,000mah equals 176 wh ?

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 18, 2017 9:03 am
by DrkAngel
Volts x Amps = Watts
Volts x Amp hours= Watt hours
V x Ah = Wh

"V" (Volts) is based on the average discharge voltage during a full discharge.
EG. 4.2V >> 3.2V MFG rated @ 3.7V
Wh is based on Ah x V averaged

Wh is rated at mfg rating of average voltage at modest discharge rate 11.1V (3x cell 3.7V) x mfg rated mAh (4000mAh) = 44.4Wh
(12s) 44.4V x 4Ah = 177.6Wh (180Wh limit)

edited previous post ... clarified expanded.

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 18, 2017 4:12 pm
by 999zip999
Aren't we stuck at 42.5 volts because the upper limit of his controller or 10s ?

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 22, 2017 1:24 pm
by BlueBell
Can we pick the direction of rotation on this motor or is it predetermined?
We are proposing to thread an aluminum tube onto the shaft threads of the motor.
If it turns counterclockwise, it will tend to unscrew our propeller shaft!

Re: Battery Advice Needed For Middle School Competition

Posted: Nov 22, 2017 3:18 pm
by DrkAngel
Youtube search shows motor turns clockwise, facing gear.

BM1418ZXF(BLDC)

Brushless motors, typically, are not reversible, without special controller.