Now that I have your attention, I would like to make sure I don't go boom. I have this battery, I thought that one pack would get a QE through a sortie but now being told by more experienced battlers I need two per sortie. Battery: http://www.hobbyking.com/hobbyking/store/__14069__ZIPPY_Flightmax_4200mAh_3S1P_30C_LiFePo4_Pack.html Charger: With the upcoming Lancing battle I don't have time to switch the wiring to have one pack for pump and another for the rest of the boat. Can I hook them up in parallel or is this a no-no with LifePO4?
I run 4 of these now in the Baden, in parallel.... for two pumps and two motors. If you have 1 motor and 1 pump you MIGHT be able to get by with 8ah but it depends on the motors. To answer your question you CAN run the packs in parallel.. make sure they are both fully charged.. and keep an eye on your usage. The computer charger can tell you how much current you put back in.. to give you an idea of how many AH you are using. if you are wrong.. you burn two packs... I burned 4 at the Brouhaha trying to stretch them to a third sortie.. the sortie when I took the most damage. Overall I would suggest at least 3 per sortie...I don't think those cells will carry you for two sorties.
I use two in parallel in the South Carolina and change every sortie. Mine are 4100 and 4200 mamp packs. I might could stretch to two sorties but prefer to be safe.
Yes you can!!! When I was at Carl's with only 8 packs I had to take the RTV and drive uphill to charge batteries and then drive back down. I think one time that one pack had not fully recharged but it was close enough.
Also keep in mind that the danger of over-discharging is real. At the Brouhaha that is exactly what happened to me... I ran the packs too long (3 sorties instead of 1) and when I was heavily damaged and had two pumps running full stream.. the pumps started to pump less and less until they could go no more. When I took out the batteries they were puffed, hot, fat, and measured 0.0 volts.. never to return.
I think 2 per sortie should be fine if you are running stock 550 motors. I run 2 per sortie in the Rivadavia (Baden with 1 rudder) with generic 550 motors (1 drive, 1 pump), and I typically take 800-1000 mAh out of each pack, with a max of around 1400mAh. I use 4s packs, so at 3s the mAh per sortie per pack would be closer to 1500-2000. If you are running a Titan or Stinger on the pump you would probably still be fine, but will probably be discharging the packs closer to 3000mAh per sortie.
this is exactly why I set a low voltage cutoff on my ESC's. I am particularly fond of the esc's that have the soft cutoff that power limits rather than a hard stop. I have one of those on my pump, power limit works great. drive motors are shut down type but they are not the biggest current draw in the system and tend to not be the first to shut down.
The problem is there are so few ESC that are LIFE aware and are only set for Lipo.. and/or the BEC is not large enough on the ESC to use and so.. you don't get the benefit of the voltage cut-off. You could spend an extra 20 bucks on a Castle BEC but that is just another item to fail. I use a receiver battery to cut down on issues related to powering the radio off the main batteries. Also the cut-off wouldn't help me as the Titan pumps draw the most power, not the drive motors.
I would go with 2 per sorite. I've been running mine like that for a while and it works perfectly fine.
