Prewarm batteries is a MUST

[gil sonsino]

Did a simple test with a tired 3S pack that showed IR (internal resistance) of 14moh( 5-5-4) at ambient temperature,the balancing was ok. Icharger 208B is a great tool for Fe models as it has this IR function.Put it in my warmer batt bag at 45C for about ten minutes and checked again the IR...WOW number dropped to 4moh(3-1-0).so for you that want best effiency for your FE set up's Pre warm batteries is a MUST specially for me that only run saw! Gill.

 

[Chilli]

Tell us about your warmer bag.

 

[gil sonsino]

Chilli got it at HK...simple and inexpensive device that many 3D heli pilots use before Racing .and from my experience is working good with my saw riggers.I need to test it more but with the decrease of the IR I guess we can get na increase of speed too.Gill http://www.hobbyking.com/hobbyking/store/__33990__Turnigy_Programmable_Lipo_Battery_Warmer_Bag_12v_DC_.html

 

[Chilli]

That is very cool Gil. I was looking for a way to preheat lipos as late fall and early spring isn't the best time for FE SAW's. Will give these a shot. Thanks for sharing.

 

[Doug Smock]

If you have power available heating pads work great for this. I recently picked up a unit similar to this that the local medical center was going to throw out. http://www.enthermic...230/pid/10.aspx It's not for everyone but will meet my needs perfectly. I'll lease you some space in Nov. Mike. :lol:

 

[Chilli]

Man, you hit the lotto with that unit. Cant imagine what that sucker costs new. I was looking into heating blankets, plate warmers and there is a place on ebay in Canada that sells thermostats. Was going to throw that stuff in a cooler. I've got options now. LOL That reminds me, I've got some days off I need to request......

 

[gil sonsino]

Doug's suggestion would be nice to earn some bucks at the lake lol. Actually I got two Hk bags as there is space for just one 6/7S pack.Gill

 

[Patrick M]

OMG!!!...... you guys are stepping into a forbidden area here! When attempts were made to introduce Lipos into FE racing, one of the major nono's was preheating packs. Bringing packs up to operating temperatures was considered extremely dangerous and one of the major causes of Lithium fires, e.g.: burning houses, garages and vehicles.... LOL! Can't seem to find any organizational rules banning the practice now. Walgreens digital heating pads work well.........

 

[Chilli]

I haven't heard that. Anyone know if ROAR bans the practice? I know they have about six pages of Lipo rules in their book. All necessary safety precautions will be taken at the Elizabeth City SAW's. Packs will be warmed in Doug Smock's trailer...... I'll be parked at the other end of the lot ..... :lol:

 

[Samuel Hagan JR]

I haven't heard that. Anyone know if ROAR bans the practice? I know they have about six pages of Lipo rules in their book. All necessary safety precautions will be taken at the Elizabeth City SAW's. Packs will be warmed in Doug Smock's trailer...... I'll be parked at the other end of the lot ..... :lol:

Probably a dumb question but what is ROAR and what are the rules. I've seen safety videos about LiPo's.

 

[Chilli]

ROAR is the sanctioning body for RC Cars and Trucks.

 

[gil sonsino]

Patrick when I say prewarm a Lipo batt I mean raise its temp to the same temp it will reach after a good run so I see no worries here to deal with this practice observing the safety limits.Gill

 

[properchopper]

Great find Gil. I'm ordering one today. I've been using a car chiller/warmer for quite some time - problem is it pulls 4A and it puts a strain on my old deep cycle lakeside battery when coupled with multiple chargers- the HK unit pulls 2A max .

 

[Patrick M]

Patrick when I say prewarm a Lipo batt I mean raise its temp to the same temp it will reach after a good run so I see no worries here to deal with this practice observing the safety limits.Gill

Never believed the BS myself, but during the great Lipo debates the anti-Lipo crowd used pre-warming as a portion of their paranoia package. Some groups had to promise not to use artificial means of heating, at least until the paranoia passed, and most realized that the hype was unwarranted. In the mean time we had found that simply leaving a pack in the sun on the dashboard would warm it to 120*+ (135* here in AZ).... I've been a long time user of heating pads and have set at least one SAW record using a pre-warmed pack.....

 

[gil sonsino]

Even with the temp set at 45C after twenty minutes my big packs are just 32C so very reasonable and safety too.Yes the consume of 2A is very low compared to other devices and I think the price is great.Where we practice we have power so I use to charge my packs in the bag and the final IR is unbelivebly low.Gill

 

[Jim Caldwell]

I have been doing this for years, using car warmer/ chiller draws 4.5 amps. I run it at the lake off of 1/2 (12V) of my power supply. 100F into the boat before oval race SAW racers use 120F. From 72F to 100F IR goes from 3.0 to 2.0 that 1/3 more power for the first 1 or 2 laps of a 6 lap race until the batteries warm up and they come out the same temp. or slightly less as not warming them up!

 

[gil sonsino]

So we can conclude that there is an agreement among most of us and the paranoia went to the bottom of the lake! Gill

 

[Patrick M]

So we can conclude that there is an agreement among most of us and the paranoia went to the bottom of the lake! Gill

Precisely! As long as normal operating temperatures are not exceeded, pre-warming of Lipo's is an acceptable and normal competition practice... B)

 

[jayt]

My club used to run warmers for our 20C and 25C LiPos in the winter (summer ambient is 38C) and we saw performance improvements. That was several years ago and it was obvious when running that the boat ran noticeably faster later in the run as the cells heated up. But when datalogging with today's 45C+ cells we see no advantage to warming, the cells do not increase voltage with temperature like the old high-resistance low-C packs did. The mill lap warms the LiPos up plenty if the ambient is above 25C. I do not trust IR readings from a charger, but I do trust lap times and trap speeds.

 

[gil sonsino]

Jay I only run SAW so for me warm batteries has increased the performance of my riggers.IR is a good indicator of health's batteries and I use a very accurated meter to compare with my charger and they are quite the same....maybe for heat Racing this is a minor fator with the new batteries. Gill