4S li-po too close to regulator drop out?

[marcopolo]

I'm thinking about battery options for my 4up XR-E cutter BFLEX kit.

Would a 4S LI-PO cut it at full power? If some of the new R2 Vf is around 3.5v: 3.5*4 + 1.1v (regulator)= 15.1v when running at 1A. 4S lipo is around this voltage for 80% of the discharge cycle. Also if I get some good R2's, Vf @ 1A may even be slightly lower than 3.5v.

It would be OK for 500mA, 250mA, 125mA modes etc.as Vf is lower...but what i'm thinking is that if the regulator drops out and it goes to direct drive in full power mode - this would actually be very efficient as there are no regulator efficiencies to factor in now.

Is my thinking correct? Of course if I use a 5S LI-PO problem solved but it would be good in terms of efficiency and weight to use the 4S.

(I've lashed up some NiMH until i've ordered some LI-PO's)

Marco.

 

[snaps]

I'm using 2 Cutter quad R2s with bflex & 4 Li ion batteries & it works fine @ 750mA for over 2.5 hours with 2.2Ah (the light increase at 1A isn't that much more concidering the reduced run time & extra heat)
Vf of all 4 R2s at 750mA is 12.67.
When the bflex drops out of regulation you just get a gradual dimming.

 

[marcopolo]

Nice Lights! Is that 1 medium 14 deg, 1 narrow 4 deg?

 

[snaps]

Yes Cutter medium & narrow optics, I also use a narrow triple run at 1A on my helmet! I don't need anything brighter

 

[marcopolo]

That is a serious amount of light you have up there!!. My set up will be very similar as I have also 2 of 4up kits. But I have a sinlg MC-E to play around with for my helmet.Do you find that your bar mount narrow becomes redundant when you have your helmet light switched on?

 

[Tidra]

Yes Cutter medium & narrow optics, I also use a narrow triple run at 1A on my helmet! I don't need anything brighter

You must be kidding,... hahahahahaha


For now I am using 3x SSC P4 @ 1.2A mini triple Khatod fi35mm on helmet and I could ride anywhere,...

 

[snaps]

That is a serious amount of light you have up there!!. My set up will be very similar as I have also 2 of 4up kits. But I have a sinlg MC-E to play around with for my helmet.Do you find that your bar mount narrow becomes redundant when you have your helmet light switched on?

Yes it doesn't do a lot at below 15mph but above that it provides useful light from about 8m to 15m (the medium quad lights up the front wheel to 8m)

You must be kidding,... hahahahahaha

No - last year my lights were limiting my speed, this winter I'm almost doing daylight speeds downhill at night - 40.4mph so far!

 

[marcopolo]

- 40.4mph so far!

LOL; the fillings in my teeth come out at that speedp>