Again on Batteries: Standard C Batteries vs Rechargable Batteries vs LiPos


#1

Hi, C batteries are not that common, so today I went buying 8 of them.

And I was shocked by their cost: without going to expensive long lasting batteries, the cost for a pair of C batteries was 4.5€, which means that 8 batteries cost 18€ (22USD). And that's enough for an hour of usage.

Use it 30 times, and the cost of batteries will be more than the cost of the ROV itself: not to mention the ecological impact of disposing that amount of batteries.

Probably an easy solution would be to use standard rechargeable Ni-Cd or Ni-Mh batteries, but since those are 1.2V, we'll end up with 9.6V. To get 12V we would need 10 of those, so we should make the battery tube longer. These cost around 10-12€ per pair: will be 120€ for a set, but this is the cost of less than 7 usages of normal batteries.

Or even cheaper, would be using LiPo: a pretty standard LiPo costs around 10€, a good battery around 20€ and super- quality one around 30-35€. They are 12V, so we would need one of them, or maybe to increase the duration, 2 of them wired up in parallel (also to keep the ROV balanced, with one per side of the ROV).

I don't know how long the ROV would run with LiPos, but even having 4 standard LiPos (2 as spare) would cost less than a full set of Ni-Mh (40-80€ depending on the quality of the LiPo vs 120€).

Running on LiPo have the additional problem of having to redesign the batteries' tube as normally LiPos come in the form of a parallelepiped.

Room for thoughts :)


#2

Yes, disposable isn't a good long-term solution. Jim started a good discussion about power management here: http://openrov.com/profiles/blogs/poe-and-rov-power-management?xg_source=activity

Some battery resources in the comments.

More importantly, we need to attack this in a more organized fashion, probably with a decision tree and a way for folks to report on different attempts/strategies. That would also give us the opportunity to wrangle all the different battery links that are scattered around the site.


#3

Definitely PoE is another option, same problem: you’d need a power source on the ground, which might not be available.
Imagine exploring a pond in the forest: it’s just you, your laptop and the ROV.
Simo


#4

Right. And when we've been traveling and out in the field, it's been great to be able to get the disposable when we need them.

Based on my conversations with Eric, I think we can run on less than 12V if we use the NiMh. What do you think?


#5

BeagleBone and Arduino run on 5V... The LEDs might need 12V, the motors will go even at 9.6V I guess (just slower RPM)


#6

I agree with you! Not a very good idea to run on C batteries, my own ROV will run on LiPo.

One big disadvantage with LiPo is that they are very sensitive to deep discharge so some kind of voltage measurement in the ROV would probably be required to not destroy the batteries.


#7

Yes, the cape will have such a voltage measurement. And running on standard ESCs I guess a cut-off threshold can be set


#8

Hey,

Another take on this: how about these LiFe batteries: http://www.batteryjunction.com/ultrafire-brc-18650.html

I have them (different brand but same type) for LED diving torches. They work fantastic and give a very good lifespan.

They run on 3.7V, so combining 3 would give us 11.1V and to increase capacity we could use 2 sets of 3 in parallel (this way we could distribute into two battery tubes again.

The one thing I don't know is, how much lifetime they can give us. I'm have to admit my electronics know how doesn't do right now to calculate that. Can anyone give a hand?

Cheers

Dominik


#9

Have a look at this:
http://openrov.com/forum/topics/battery-pack?page=1&commentId=6365107%3AComment%3A23635&x=1#6365107Comment23635


#10

the one time battery is not a good choice, and we recommend that you could find a good one in the lithium battery list as below for your application http://www.ufo-battery.com/category/small-capacity-battery


#11

Not that it matters all that much, but we’ve been having great success with Thundervalley 4350mAh 3S LiPO packs on our Eiodothea Mark II OpenROV hybrid. Have it in a mineral oil filled o-ringed project box and runs for hours. If we pegged the motors and draw 2amps consistently, we can get at worst 1.5 ish hours, and at best, drawing 0.3 to 0.4 amps, well 14 hours…ish


#12

Hi Jim,

I did a search on their website and couldn’t locate the battery you were talking about. Can you provide a link?

Thank you,

Ellie


#13

Most of the information on this thread is old. The official OpenROV recommended batteries can be found on our store.

http://store.openrov.com/collections/accessories