After reading some reviews of the Seawind Readyset version, it appears that the sail winch is very power hungry. It has been suggested to use at least 2500mah NiMH batteries, but would a 2S 7.4V lipo with say a CC BEC or voltage regulator be better? I was thinking perhaps a 2S 1350mah 20C lipo or something similar. Thoughts?
Hi,
it depends on the electronic components. If your receiver, servo and winch are specified for 2s LiPos, it is ok. If not you have to take the risk. Many servos and winches are specified up to 6V which is 4Nixx cells only! Remind the voltage peak at the beginning. A fully charged 4 cells Nixx battery might have up to about 7V during the first minutes (which is clearly out of specs). But the voltage drops quick enough under load to avoid damage.
Sometimes the components are explicitly specified for 5 cells - then you can replace the 5 Nixx cells also by a 2s LiFePO (which is my favourite choice).
The voltage of a freshly charged LiPo is more than 8V for a relatively long period of time which is usually too much unless otherwise specified.
So, if you are not sure, use a voltage regulator. But it should be capable of the current used by your winch. But such a set up reduces only the voltage drop under load. It does not reduce the power consumption of the winch. In contrary - if the voltage is kept constant be the BEC or voltage regulator, the winch will be more powerfull and the power consumption might be higher at the end. Btw, energy content of the LiPo battery mentioned is less than that of the NiMH: 4.8V * 2500mAh=12Wh is more than 7.4V*1350 mAh=9.99 Wh. In reality it is even worse, because you cannot fully discharge a LiPo without damage.
I guess it depends on what you mean by ‘power hungry’. I don’t know what winch servo comes standard on the ReadySet version, but I fitted a Hitech HS-765HB Sail Control to my kit version and running a 6V NiMH battery pack I can sail for three hours continuous in light winds with no problem. I have not yet sailed it to the point of depletion of the battery, but when that happens the system shuts off the 765 and supplies power only to the rudder servo, allowing you to limp home on rudder only with the sails set wherever they are. I am sure that with two battery packs and one pit stop I could probably sail for eight hours.
I do this, lipo and a BEC, and it works fine. The only downside is that you really need to be experienced with lipos because they can be unsafe if treated improperly. Also, for the record, the energy density is much higher with lipos than NiMHs, it is the capacity in this example that is lower. The advantages of lipos are higher energy density and very fast energy dump capability. The former allows greater capacity/lighter packs. The latter allows higher draw equipment, which is relevent when driving large electric motors, but not sailboat winches.
I use 100% lipos but i also run 100% HV digital servos…
Keep in mind also that with a lipo you will be saving weight not sure how close to minimum weight the seawind ready set is.
rather than dropping to a battery with lesser MAH for lesser weight… why not put in a higher MAH lipo which will have the same weight as the nimh…
Yes under extreme circumstances lipos can be dangerous. but you’d need to beat on them pretty hard, short circuit them, cut the pack open and immerse in salt water to get a substantial reaction…or try to charge them improperly…
you will need a special charger. I have taken lipo’s down to zero (accidentally) and I have been able to revive them took quite some time to slowly add juice back into them until the lipo charger woudl take over. Not reccomended…
I’ve got more than a few lipos that are 4-5 years old…
LIPO batteries are permitted by Class Rules but I fail to understand the attraction and added complication of using a LiPO plus voltage regulator when a 5-AA cell NiMH fits in the battery box perfectly and is as reliable as all get out but I guess some folk have to have the latest fad item. Don’t forget Rule 11.4 regarding required location for the battery!
Mike
Mike,
half a dozen or so years ago I’d agree with you on the LIPO being a fad. right up there with 2.4ghz radios which I told myself I’d never buy…
I don’t think lipo’s are a fad any more. and the more they are used their track record builds. Their prices have come down and are comparable to nimh pack, and the performance ,I feel, is much better. no memory effect. higher voltage with less drop-off, longer life (ie more charge cycles) coupled with the lower weight
You should look into LiFe batteries (aka A123)… A 2s 6.6v LiFe battery pack can run 6 volt servos with no regulator… Lighter than NiMh, all the advantages of a LiPo but not the instabilities and having to be careful about over discharging, storage problems, etc. They make great receiver packs… I run 2000Mah ones in my boats and never have issues…
Cheers
Eric
Eric, What do you use for a charger for LiFe batteries? I am just using NiMh now.
I have a Bantam BC6DX II charger that does most chemistries including LiPo, Nicad, NiMh, etc. Most LiPo capable hobby chargers (even the cheaper ones) will do LiFe as well…
Cheers;
Eric
The best chargers out right now are the ichargers. Not cheap, but incredible value. I have a 308 that I use for my RC cars, I charge at 20 amps. Packs are done in 8 to 9 min. It also shows the IR as the packs charge, allows discharge, will charge up to 8 cells, charges 2 packs at once, has adjustable cut off voltage and is user calibrated for voltage. You can even update it with a USB cable.
There are lots of cheaper chargers out there that will do multiple chemistrys. I also use a Thunderpower 610C, but they are no longer produced. Its a great little charger, but is limited to 10 amps.
this is what I use have had it a couple years…have never charged over 1 amp. works flawlessly
http://www.hobbyking.com/hobbyking/store/_28245__HobbyKing_ECO6_50W_5A_Balancer_Charger_w_accessories_US_Warehouse.html