Rx battery

[Mulisha]

Just wondering what size, type and brand batts are you running for your rx. My castle bec just gave up today in the middle on the lake

[NativePaul]

BEC or UBEC all the way for me, I haven't used an RX pack for something like 20 years.

When I did I used 5x industrial Sanyo 700mAh AA cells with short buttons and welded tags for big stuff or 5 of the oval button cells from a rechargeable Sanyo 9v PP3 battery, I am not 100% but I think these were 120mAh.

[Mulisha]

Do you use the castle bec? Was thinking of trying the castle pro

[Scott T]

Pack of 5 x 1600 2/3A Intellect cells. Very reliable.

[NativePaul]

I have used a Castle BEC in the past and consider it to be a good unit, although the maximum input voltage is lower than most, I used one for years with my Hydra 240s on 4s (I see linear BECs as 3s Max). Thanks to the progression of technology, all my ESCs that are in use at the moment have switching BECs built in to them (a mix of Castle and HiModel), so I have no use for an External BEC, and they sit collecting dust in my spares box in case I have to break out an old fashioned ESC.

[jetnfast]

I really don't understand the point of an external BEC in a boat other than to take an extremely minimal load off the ESC. In an airplane it makes more sense since you isolate the components in case of ESC failure. If you have ESC failure (and internal BEC failure) on the water in an FE boat, it will just stop where it is with no control. Of course you need to go get it by recovery boat, kayak or whatever, but its not like an airplane that burns up an ESC then crashes due to loss of control. I guess the one instance would be if it burned up in a boat on a WOT run and you had no steering for the decelerating portion, but that would be it. Otherwise the external BEC in a boat just adds complexity and weight.

[Fluid]

In boats external ESCs are normally used in place of a receiver pack, with an ECS that does not have a built in BEC. They weigh less and never need to be recharged. Perhaps now you understand....



.

[NativePaul]

Linear BECs are just a FET that burns off extra voltage as heat in order to drop the output down to 5/6v, the more voltage you have above the the output voltage the hotter it gets and as such they limit the number of cells you can run, they are often quoted as being for 12 cells/4s max but 10 cells/3s is a more realistic limit, and even with 3s the heat it generates is not insignificant. Take for example a 3s boat with a standard size digital servo on the rudder that consumes 5A at 5V during a turn, near the start of the run you have 12V from the battery so the linear BEC has to drop 12V-5V=7V x 5A=35W, or the equivalent of turning on a medium sized soldering iron attached to your ESC every time you make a turn, and it is impossible for high cell counts, for example 6s would be 24V-5V=19V x 5A=95W, 15W more than the soldering iron I use to swap wires on ESCs so even without any heat from the ESC itself the BEC would get hot enough to de-solder every component on the ESC within seconds.

At one point if you wanted over 10cells/3s you needed a separate RX pack and had to put up with the extra weight and charging. Then standalone switching UBECs (that switch the full voltage on and off at such a speed that it mimics a lower voltage without having to burn off excess voltage in exactly the same way our ESCs do) came out reducing the excess weight and eliminating the charging, and a few years ago ESC makers started building switching BECs into their ESCs which has a negligible weight penalty over a linear BEC and generates only a small amount of extra heat in the ESC. At this point in time I would guess that the majority of ESCs have switching BECs so external UBECs are becoming less needed and the market is shrinking, but there are still ESCs on the market with linear BECs and folks still have older linear BEC ESCs in their models, so for the foreseeable future the will still be a market for external switching BECs.

[Chilli]

I use Hyperion LiFe packs for my receiver batteries. I run a 850mah on my 4S boats during a race weekend with no problems (4 or 5 heats). I use 1450's in my gas boats except for the one with a quarter scale rudder servo. I use a 2100 in that one. I'll use the 1450 occasionally on the 4S boats also. The extra weight not that bad (still less than 5 sub C NiMh's). Go 1450 if you want extra piece of mind.

[martin]

I also use 2s LiFe rx 1000mah packs, anything that reduces load on the esc in SAW type set ups. Rx pack only weighs 48grams.

[Chilli]

I'm with you. If it reduces load on the ESC (no matter how little) I'll do it.

[bigwaveohs]

I agree...the 2S LiFe's work great. I had a problem with radio voltage drop-outs. I think it was caused by a dip in the primary battery voltage under load.External pack solved the problem...just insert a short servo extension, cut the power wire (or pull that pin out of the socket) and power the radio directly with the external pack...add a switch and you can save the battery between heats.

[Mulisha]

Some esc don't have a bec also. Plus SF recommend using external bec over 4s. Might just try the castle pro bec

[viper1]

Many people using ESC's with modern switching BEC's build in, still use an external switching BEC with same specs, because... what was it again.... because the internal BEC can fail !
Go figure.