I have shelved the AOS ship till I have a couple of my ongoing projects finished. With my Mutsu getting real close to being finished I have decided to go ahead and let my two boys start getting involved in the hobby. I have two Identical Espanas for them to cut their teeth with. I want to switch from the older SLA's to the newer LiFePo4s but I have no idea as to what a smaller vessel will need. I am assuming a couple of the round cells that are 3.2v - 10AH. They seam to be small enough yet have plenty of juice for two rookie captains to chase dad around the pond with. www.batteryspace.com/customizelifep...thpcb.aspx Is this a correct assumption?
My major issue with it is the 10amp limit on the PCB... then ... 100 BUCKS a pack that is $10 per AH!! In addition as this is a 28 second Class 4 DN you wont be running from anyone.. I certainly wouldn't run 10ah in the VDT if I was building it. I would want a minimum of a stinger pump and with dual drive motors I would need more than 10ah in a battle. Try to fit two of these in your ship if possible. http://www.batteryspace.com/LiFePO4-Prismatic-Module-3.2V-20-Ah-10C-Rate-64-wh.aspx
Yep thats what I run in my Mutsu... wont fit in the Espana I know they are expensive, but I am hoping they last long enough to outweigh the cost. To run my Mutsu I would need 4 SLA's for the day. Thats about 75 to 80 bucks if you add shipping. Not much difference in price if you add the overall life of the batteries... the SLA's dont last long and I am told the shelflife of the LiFePo4s will at least last as long as a couple of SLA sets... so the cost is more up front, but cheaper over time. Even if it is not, if I get better performance and run time out of the LIfePo4s it will be worth the cost to me. The only ones I can find that fit the Espana's so far has been the ones I linked... if you buy the cells and PCB to make them yourself it is just about the same cost.. My biggest worry is the threat of over discharging them. The set here I linked has a PCB installed, but the ones I am using for the Mutsu, the ones you linked, do not have a PCB so I am not sure what to buy for them if anything to help protect the batteries. I will continue to ask around to see what I need with them for protection.
It really depends on your setup and how much current you're pulling. (Difficult to judge before the ship is built but such is life.) My VDT ran great for years with 20AH @ 7.2V NiMh in it. During the ongoing refit I'm transitioning it over to 12AH @ 9.6 V LiFePO4's and brushless, that should be more than plenty judging from what my Bismarck draws. (about 5 AH per battle from a 12.8V LiFePO4 setup). However I dont think you can find the 12Ah LiFePO4's that I'm using anymore, atleast I can't. Most people have way to much battery power on hand anyway so over discharging becomes less of an issue. (remember LiFePO4 discharge curves are much flatter than SLA discharge curves) Plus you can get stand alone voltage monitors that buzz or whatever if the voltage drops too low, that is probably better for our uses than a limiter PCB if you're really worried about over discharge. Are you tied to a certain voltage? Alot of people seem resistant to use anything other than "6V" but there really isnt much reason to limit yourself to that. Are you going to do these boats brushed or brushless? That will change your power requirements as brushless are more efficient (cet. par.). It is probably worth building your own setup from something like: http://www.batteryspace.com/lifepo438120pmsizecell32v10ah100asurgerate32whwith6mscrewterminal-unapproved.aspx http://www.batteryspace.com/LiFePO4...-rate.aspx or http://www.batteryspace.com/LiFePO4-40152SE-Cell-3.2V-15-Ah-150ASurge-Rate-48Wh-with-6M-screw-Termin.aspx
Christ I am so out of my comfort zone when it comes to the batteries.... I am using two smaller 380's for the drive sytems and a 380 for the pump... the smaller motors.. There are three kips running the guns.. Any suggestions on brushless motors for smaller vessels that dont break the bank?
Hobby King has plenty of affordable motors and ESCs. If you're on 2S LiFePO4's I'd probably try something in the 1500Kv range to start with and then adjust from there, off course that's dependent on prop size and what gear ratio you use. (Direct drive counts as 1:1) Tugboat might have a good suggestion since he has outfitted more small ships with brushless than I have. Not knowing or have played with your setup before I'd start with this motor: http://www.hobbyking.com/hobbyking/store/__8503__Turnigy_2632_Brushless_Motor_1500kv.html and this ESC: http://www.hobbyking.com/hobbyking/...verse.html
Look at / read the product pages and ask about what you don't understand. Better to teach you how to fish....
I really love my 2S 8AH LiPOs One would do an España, easily. I did 5 hard sorties at Nats one year without changing the battery out. They're $35 each at Hoby King (not on sale at that price, sometimes it's lower). If they were going to explode, I'd expect that I'd have been missing a ship at some point in the 3 years that I've been running them.
In the product page it states " Input voltage: 2-3S Lithium batteries / 4~12 Ni-xx If it list the voltage at 4-12v, I would understand that... 2-3S is speaking french to me.. Sorry I dont know what that means.....
I so hate batteries because I have never understood the darn things and how voltage/wattage works... I just know it hurts when you pee on the fence @Tug So this set up would work for the Espana? Can these be chained in parallel for double the AH? hobbyking.com/hobbyking/store/__236...ouse_.html X3, Two for drive and one for the pump www.hobbyking.com/hobbyking/store/_...500kv.html x3, One for each Brushless motor.. www.hobbyking.com/hobbyking/store/_...verse.html
Some electrical theory as applied to our hobby: Power = Voltage x Current. Serial connections add voltage for same current Parallel connections add amphours for same voltage. So: take 2 3.2V 20ah batteries. In series: 6.4V and 20ah. Power = 128Watts (6.4*20) In parallel: 3.2V and 40ah. Power = 128 Watts (3.2 *40) So you get the same POWER output when putting batteries in. Advantages to going to higher voltage are that for same load (driving motors and pumps), current draw goes down, resulting in less heat generated (wasted energy) and less wear on motors (so long as they're designed for that voltage....DON'T run 12V motors at 6V unless you like frying them. So for most apps, a 12V system is more efficient overall. BUT.... receivers require 6V. So you need an extra circuit or battery. My personal opinion is that the extra complexity more than cancels out the greater efficiency of the 12V system. Which is why my boats will stick w/ the 6V.
Spudsy, any of those three would work, but more than two is beyond overkill (and I love me some overkill). Using two 2S batteries in parallel is nice because you can charge them separately on cheap chargers. The funny thing (to me, anyway) is that the LiPOs have a max charge rate of 5C... which with an 8AH battery means that you could charge them at a 40A rate (beyond any of my charger's abilities!)... so charging at 2A over lunch is 20 times below their safe limit and thus really conservative but gets you back on the water fast As Chase points out, I run a brushless ESC on my drive motors (one per), and the battery eliminator on the ESC takes care of receiver power. Never had problems with surges with this setup, either. With two drive ESCs, you do need to disconnect the red servo lead on one of them so that the two BECs don't fight (no programmed-in voltage droop for proper load sharing, designer was NOT a nuke electrician). I'd love to run the 12V (or higher, had looked at a 10S battery once), BUT... my drive motors have a kV rating, and running the voltage up means that my motor speed goes up, and really low kV motors tend to be spendy and big. Also, the ESCs that can handle the high voltage are also spendy. My brushless experience has been with 7.4V and 14.8v systems, and the cheap HobbyKing ESCs which are damn near bullet proof, as well as being cheap enough to have two spares in the toolbox that you probably won't need. My setttled-upon best practice for brushless systems is 2S batteries, whether LiPO or LiFE, as it does the job well and very cheaply relative to higher options. I definitely tend towards the LiPOs, even as the prices on LiFEs come down a little.
