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I know this has probably been thrashed out before, but I have just got some 18v motors and am wondering whether to buy Lipo or NiMh batteries to power them. What would I need to do to use Lipo? i.e. put them on metal and remove when not in use. What advantages do they have over NiMh? Or would it be best to go with what I know? Can people recommend particular makes of battery and possibly chargers? Sorry about all the questions.
LiPos traditionally require greater care than NiMH to be used safely. I say traditionally because they are in fact perfectly safe if respected. You would need a charger capable of balance charging LiPos and you need to put them in a fire retardant bag to charge safely (readily available, search LiPo charging or protection bag). I believe the current ruleset doesn't require you to have metal under the pack, it's a recommendation.
The advantages are in bang for buck. LiPos are miles ahead of NiMH in both power output and capacity per gram for the same sort of money.
That said if your robot doesn't require the huge power LiPos can put out then you may as well use NiMH for now. They will make a nice upgrade later on. Meanwhile you can read up about them and how to treat them; everything you need to know is online.
I wouldn't recommend really really cheap LiPo packs (Hobbyking's Nano-tech and Zippy ranges for example), whilst popular they often perform under their supposed rated output. I have used regular Turnigy packs (also Hobbyking) and have found them to perform well, would recommend. The best for roboteers are probably Optipower batteries. I think FRA members still get a 30% discount with Opti making them competitively priced despite being high end.
A good first charger would be something like the Imax B6. You'll need a suitable power supply for it. Cheapest place to get a B6 is you guessed it, Hobbyking!
lipo all the way... for the weight saving and power alone id never use anything else
Team RCC went LiPo early, and the less expensive ones too boot. (I myself prefer the HK Zippies.)
Even if they are "hobby amp rated", they do a good job in all our machines now.
Charger. Imax B6 is the basic charger. You can't go wrong with that one, as long you don't want to recharge large packs in 10 minutes.
I believe most affordable 50W rated chargers just use the same basic technology, maybe repackaged with a 4 in 1 box, or with an extra LED to tell somebody something.
Of course there is always the alternative LiFe packs that are lighter than NiMH and not so prone to fire.
Thank you for all the info. I currently have a Fusion Ethos LX41B Pro Charger that will charge LiPo batteries up to 4 cells. The B6 charger seems to be very cheap (how quickly will it charge a battery?). Are there others that will charge faster as I don't mind paying more for one?
As for batteries, I have seen this one http://www.hobbyking.co.uk/hobbyking...ipo_Pack.htmll . I assume that the fact it is 22.2v should not burn out the motors in a short fight. 3300mAh should last a few fights I think.
The speed of charging with an Imax depends on set value, amount of cells and total watthours needed.
50W is the max the charger dan push. It will take 30 minutes to recharge a 6S 1000mAh battery from empty to almost full.
(The complete balance cycle can take some time)
Have we ever had an actual Lipo fire with the current ruleset?Quote:
Originally Posted by kane
I believe the only way to have a LiPo fire with the current rules is with pure combat damage.
Anything else is wrong handling.
https://www.youtube.com/watch?v=KJ8xGJ9ZTCsQuote:
Originally Posted by psychostorm
Other than that though, I don't think so.
That was battle damage though, ram a piece of metal through a lipo pack and that will happen :p
But if you think of the number of robots running lipos now (across all weight classes), we've never had a fire just from misuse. A few folk have had packs/cells that have swollen up, but no fires that I can think of, contrary to the belief when everyone started using them that we would all be treated to regular pyrotechnics masterclasses.
Doesn't count. No base to hold the battery in at the time.
I believe the battery was held in, it was one of the front prongs being slammed into it by a hit from 720's drum that pierced the pack.