Suitable batteries for this motor/servo? (HB DC1)

[JCM6172]

Good day gentlemen,

Am completely new to the hobby so pardon my cluelessness.
After quite a bit of reading and research, I recently pulled the trigger on a Hobao DC1 RTR, except it doesn't come with a battery and charger. Relevant requirements and operating conditions:

- as large capacity as possible/feasible
- single pack (easier to maintain and charge rather than many smaller packs)
- suitable for 2-3 hour runs, mostly trail and a bit of crawling
- ambient temps 28-32c (82-90f)
- long runs about once a month
- shorter runs (~30m) a couple times a month
- might add a bunch of LEDs, roof bar and undercarriage light strips
- might add a powered winch
- no intention to upgrade motor and servo

The motor seems to be a Hobao 27T with a Deans plug.
Servo is a HB5518. Some pics: https://imgur.com/a/0jSpMOC

I've read up on LiPos everywhere but nobody seems to have covered:

1. How do I know what C-rating I should get for this setup?
2. Does the voltage (number of cells) affect how "powerful" the car is?

Appreciate any advice on the above, thank you!

Cheers,
Nick

 

[Inspector86]

First, Welcome to RCC!
For crawlers the C number is basically irrelevant as they don't draw enough amperage to make any difference unlike say a drone or plane that must run at or near full power in order to stay airborne. However, the higher C number batteries tend to be better quality and thus higher priced. Take a look at the documentation that came with your RTR and find what battery the manufacturer recommends. Most can use either 2S or 3S LiPo. 3S will give you more available power which translates to a bit more top speed. So a 3S battery in the 5000 Mah or up range will give you 2-3 hours. Think of the Mah as a fuel tank, the bigger the Mah the longer the runtime. Buy the highest Mah that you can find that will also physically fit in your battery tray.

Also, take a look at this thread which contains a number of links to specific battery information.

http://www.rccrawler.com/forum/elec...or-battery-threads-rccs-top-tech-threads.html

 

[JCM6172]

Alright, so I'm going through the user manuals, and in one of them it says:

WARNING
HB-5518MG servo accepts 4.8-6.0 volts.
Exceeding this limit will damage the servo.
5-cell receiver pack recommended for nitro vehicles.
Control system: Pulse width frequency control (1500 usec center position)
Working voltage: 4.8-6V
Torque: 15.3kg.cm (at 4.8V) / 18.6kg.cm (at 6V)
Speed: 0.14sec/60* (at 4.8V) / 0.12sec/60* (at 6V)
Motor: Core motor
Type: Digital

Which sounded fine. Until I started browsing the local marketplaces for batteries, and unless I'm mistaken it turns out 6V is an extremely low threshold?

The seller I'm looking at has these in particular:

• 2S1P 7.4V 5000mah 50C: 155mmx48mmx16mm ,260g
• 2S1P 7.4V 5200mah 50C: 138*46*24mm, 275g, with hard case
• 2S1P 7.4V 6000mah 50C:138mmx46mmx24mm,295g,With Hard Case
• 2S2P 7.4V 7000mah 55C:138*46*24mm, 312g, with hard case
• 3S1P 11.1V 1800mah 50C:105*35*20mm,142g
• 3S1P 11.1V 2200mah 30C: 105mmx34mmx24mm, 176g
• 3S1P 11.1V 2600mah 50C: 115mmx34mmx21mm, 201g
• 3S1P 11.1V 3000mah 60C:136*42*22mm,225g
• 3S1P 11.1V 5000mah 50C: 155mmx48mmx24mm, 376g
• 3S1P 11.1V 6000mah 50C: 155mmx48mmx27mm, 419g
• 3S1P 11.1V 6000mah 50C: 138mmx46mmx39mm, 425g,With Hard Case
• 4S1P 14.8V 2200mah 30C: 105mmx34mmx32mm, 220g
• 4S1P 14.8V 4000mah 30C: 135mmx42mmx31mm, 405g
• 4S1P 14.8V 4200mah 35C: 135mmx42mmx34mm, 410g
• 4S1P 14.8V 5000mah 50C: 155mmx48mmx32mm, 492g
• 4S1P 14.8V 6000mah 50C: 155mmx48mmx36mm, 549g
• 4S1P 14.8V 6000mah 50C: 138*46*50mm,580g, with hard case
• 4S1P 14.8V 7000mah 55C: 138*46*50mm,582g, with hard case
• 5S1P 18.5 5000mah 50C: 155mmx48mmx40mm, 608g
• 6S1P 22.2V 5000mah 50C: 155mmx48mmx48mm, 608g
• 6S1P 22.2V 6000mah 50C: 155*48*54mm,839g

Basically, I can only buy 1S batteries?

 

[JCM6172]

Not sure why my previous post is being held indefinitely but here's a more straightforward version:


The user manuals includes a page that states the following:
https://imgur.com/a/54h9CA4


The battery I'm looking to buy (HRB) is:
2S2P 7.4V 7000mah 55C:138*46*24mm, 312g


Am I understanding something wrong here? Max 6V basically means I cannot use anything more than 1S?

 

[ferp420]

the c rating = the amount of energy you can safely use at any given time for longer than a few seconds
with out damaging the battery
a 5000 mah battery with a c rating of 20 basicly gives you a discharge rate of about 100 amps
a 5000 mah battery with a c of 30 gives you a safe 150 amps
your crawler wont draw more than 35 amps normaly unless you bind it up and stall the motor like inspector sead it wont realy make a differance for you at this point
were it could come in to play is if your using small batterys some guys run 450 mah battery packs to meet that steady amp draw it would take a 100c battery pack to meet the amp draw needs of your motor

one other thing make sure that 7000 mah battery fits in your rig that could be a realy big battery

that page you linked was refering to the servo voltage not system voltage your esc has a voltage regulated output to run the reciver and servo usualy 5v to 6v
we normaly call the voltage regulator a bec or battery eliminating circite
the bec can be built in to the esc or external the built in units only run a few amps 3-5 most servos can run on that fine but the upgraded servos draw more amps so you would need a seperate bec or a external bec they usualy push more amps than the built in ones if that makes any sence

 

[soze]

I have a Hobao DC1, and you don't need anything special.

The stock RTR is a rebranded Hobbywing 1060 which is 2S and 3S capable.

Mine was a kit, so I put a Hobbywing 1080 in it.

If you want long run times, I suggest going with a 3S 5000mah Lipo. I run a 3S 3700mah shorty lipo and it lasts me 3 hours if I'm just crawling and trailing without being on the throttle all the time.

 

[JCM6172]

Thank you ferp and soze, I had kind of suspected that but thank you for confirming that the ESC regulates the output voltage.

Ended up pulling the trigger on a hardcase 5200mah 2s 30C Zee pack. The seller had bigger ones and the Hobao can definitely fit a humongous battery (or batteries) in the rear of the chassis/body as it's all wide open space but then weight and weight distribution concerns start to come in. :ror: