Two 3.3V Blue Cells(they are 1/10V higher than the yellow ones) (6.6V Total) But when fully charged are actually around 7.2-7.3V
The excess charge that brings fully charged cells to a point above their rated voltage burns off very quickly. It is called surface charge, and on LiFePo4 cells burns off within 5% or the the first half amp hour or so of use. After it burns off they run at about 3.2 volts per cell (or slightly less depending on the amp draw) until they reach the last 10-15% of their charge, then they drop off very quickly. Most LiFe battery specs assume either a 2 or 2.5 volt minimum voltage for capacity determination. If you notice a LiFe powered ship slowing down due to low voltage, you should probably declare it sunk and pull it to avoid damaging the cells. They really don't like going below 2 volts. Make sure you design in excess capacity. I run a 40% reserve on a 3 sortie battle, and still have more available useful power than a similar weight in gel cells. Ron Hunt
Correct, the Blue Cells though are 3.3V, so after partial use they are usually running in the 6.6 to 6.8V range. All three packs I have are sitting at 6.6 or 6.7v right now. I have never let these packs drop below 6V unless conducting a Discharge/charge cycle on the bench.
I suppose when I upgrade (usually 4 years behind the curve) I will run the ships with 20 amphs but we'll see what developes. Right now I have a crap load of good batteries that fit every ship and no reason to dump cash (busy year coming up, employment never definite in NY) plus the other ongoing project... I recommend if you are starting out, run the sla's. They're cheaper and easier. When you get some time battling, you can worry about batteries. I would build simplier the first time and add to it later.
the Lithium Iron Phosphate (LiFePO4) batteries are no doubt the wave of the future and give twice as many amp hours (and twice the cost) as two SLA battery’s in paralell, and the LiFeP04 weight about 40% less than the SLA batteries. My son and I just got started in this hobby about one year ago and his boat, plus the cargo ship run on SLA. So I think going to go with 4 6V SLA 12amp hour batteries. I know the 970 motor needs two SLA in paralell, think maybe three in parelell for 36 amps and one SLA for the pump. This weight should not be an issue, rather a need, since I floated it to get the water line with 4 10lb weights. Hovey, one of our members in the club, I think is going to LiFeP04 in his new barren. He has been doing this for over a decade I think off and on . Iceman, nice GTO. I use to have a 1968 firbird convertible, 350 4 speed. my high school budy bought it from me. I needed the money and he worked for the family buissness.
All my new construction will use LiFePO4, but the Bayern wont be finished under the current rules. I might finish her up just to sail around but wont arm her. I think that SLA are cheaper up front but more costly in the long run as SLA don't seem to last as many charge cycles. However in a ship as large as yours weight isn't an issue so a large bank of SLA works just as well as anything else really. Personally, I don't like duel battery systems for pump and drive, but it can work. My thought being that if the pump or drive battery goes you are dead meat, why have two things to that could fail? If they both fail at once (as in a single battery bank) then you are still just as dead. But if you are slowing down then you know you are running low on juice and need to work toward shore before the pump slows too much. One thing I would recommend is to try to keep your ships consistant (as practical) wih the same size and type of battery. It makes it much easier pond side having all of your batteries the same.
As far as battery life my batteries have seen an enormous amount of charging cylces. I been using nothing but SLAs over the last 20 years and for the money and ballast they work great. I used the same pack in Yamato for 7 years and I only needed to swap one Sla which I ruined my myself by shorting it out. My Bismarck used a pair of SLA's for 8 years. Both models were very active battling and cruisng. Overcharging SLAs will shorten thier life but correct charging and proper storage and care they will last a long time. As far as performance they work very well in hot or very cold weather. I used both models both ways. I agree the new batteries are superior but cost way to much for budget minded people. The SLAs are great for their ballast weight as well. For the cost 1 LIfepo I can get 2 new SLA's least here in this neck of the woods. The life batteries price will come down eventually and when they do then I can start swapping out batteries. I agree with Iceman get the Slas for now they are cheap and you will need the ballast and they work well with the 970.
going with SLA, four and trying to keep them all the same. here a few pick on instlling the two other drive shafts which will have a drag prop on them. waiting for some parts to arrive now, drive shaft support and gears for the rudders and servo.
Looking good there. Are you just going to be using those plywood discs as dragdiscs, or will you be using low angle props? Also, people allways seem to use the scale(ish) props, and not regular rc boat props. Is this due to build rules, or is there a genuine advantage to using them?
the disk are just to help with locating and lining up the shafts. the disk are 1.5 dia, so will probaly go with a 1.25 drag prop. figuring out as I go. mite have to play with different dia drag props in the water to see what works best, if time allows
Looks good. I will measure my drag discs for you to give you an idea what I have installed. I hope to test it before the lake freezes up here.
Normal drag disk size is identical to the prop size. That is the maximum allowed by the mwc ruleset. I can't remember if the ircwcc rule proposal to limit the drag disk size passed or not. The guys around here use 2.25" and 1.75" 5 blade props. We think 1.75" prop turns the ship a little tighter and accelerates less but have not completely tested that out yet with our current drivetrain setup. Ron Hunt
all I could find in the rule set is "Each ship shall be equipped with the proper scale number of shafts, propellers or drag props, and rudders, all in relatively scale locations". so looks like one can use 1.75 or 2.25 diameter props. kit came with 2.25 prop. think I will trie to postion the drag props for a 1.75 dia prop and as long as it dones not drop the shaft to far down. can move it aft some also.
The drag disk size rule proposal did pass in this year's IRCWCC balloting. So basically, the drag disks may not be larger than the drive props.
The Ircwcc ruleset has not been updated online yet. Drag disks can be as small as you like, no limit. You could use scale props instead of the flat discs, I have in the past. Nothing says you Have to use drag disks. But flat drag discs are used by almost everyone because they increase the ships turning ability by increasing the thrust necessary to make speed. For increasing turning ability, the larger the drag prop the better. Ron Hunt
Like we would make a stink if he didnt put something on those shafts? Only if it turned out to be 22 seconds. Bigger drag props is definitely the way to go though. EDIT: We would care a lot if your drag disks were bigger than your prop size as that would be considered cheating.
