Hi all. I read somewhere on here that the 12ah 6v SLA batteries (the ones that are usually 6x2x4) are heavier on the bottom than they are on the top. Thus, if you lay one down on its side in a boat, the balance of the ship gets all wonky. Is that true? I have a pair I was going to use in a cruiser, but if that's the case, I will need to figure something else out. Thanks for any info.
Well cripes. I guess those will work in my HMS New Zealand, but not a cruiser. Snipe, where else can you get batteries at, minimum, 8000mah for $15 each? I have some 8500mah SLAs lined up for $28/pair. Also, the extra weight will help reduce the extra ballast needed. Really, though, I am open to suggestions.
This is what I use: http://www.hobbyking.com/hobbyking/store/__16224__ZIPPY_Flightmax_8000mAh_2S1P_30C.html The upside is that the battery is flat and keeps weight down low in my armoured cruiser, which is where you want it. This means my ship doesn't roll much since the center of mass isn't up higher like it will be with an SLA. I don't tally know what you are building so it's hard to say if it will matter.
Thanks Chase. I am building a class 3 cruiser, either a County or a Suffren class. I am leaning toward the Suffren class at this point. Those suckers weigh a lot (something like 12.7 lbs.) so adding weight actually is an issue.
Back when I use SLAs in cruiser (08) I used the 6v 5amp hour. They are almost 2lbs my cruisers just made weight with this. In 09 I changed to nimh and got 10amp hours at the same weight.
yeah if possible I would buy up all the old large 8.4 or 9.6v Nimh packs everyone has sitting in dark corners collecting dust since they went lipo... combine a few together ( in different areas if you need to distribute weight) ... should be fairly cheap and if something happens to em not that big a deal. the constant full throttle foward and backward nature of battling is reallllly hard on SLA's unless your running like 15+AH sla's your gonna be spiking and hurting them the whole time. the 6v 4.5 ah sla in my 1/72 snowberry lasted like 4 or 5 trips to the lake before it started to degrade. and thats just a scale model puttering around the lake on a geared motor pulling a MAX of like 4 amps
For a cruiser 8000mah really isn't necessary unless you have a really hot pump (which you don't need, if you're taking a ton of damage in a cruiser that's a different conversation) or a very inefficient drive setup. How much current does your pump draw at full stream and how much does the drive train draw in the water at the correct speed? That would help determine the proper battery size for your ship. My suggestion would be to run something like this: http://www.hobbyking.com/hobbyking/...000mAh_2S1P_20_40C_LiFePo4_Receiver_Pack.html one for each sortie. 3000mah should be plenty for a typical cruiser sortie and since swapping batteries is allowed why not use a fresh one every sortie? Yes they are more than $15, however there are a lot of cases where spending just a little bit more money makes a much bigger difference in performance and this is one of them. (Solenoids are another, even if they cost more than just a little extra) If an extra $40 for a second set is that big a deal you really only need one set and then just charge them during the sortie they aren't being used/over lunch/etc it wont take that long, $40 is peanuts in this hobby compared to the cost of attending most events. (tank of gas or two, couple nights in a hotel, eating out, etc...) If you're spending time/money to go to an event I'd assume you want to have the most enjoyable time possible there, decent/quality equipment plays a big role in that. (not that all cheap stuff is bad, just some cheap things are worth the savings and some aren't, SLAs and Poppets fall into the later catagory.) Extra weight is better added as ballast (lead shot in epoxy) rather than overbuying the battery, since you get to put it where it will provide the most benefit and not just where the battery fits. Also why pay for extra battery that you arent going to use? Lead is fairly cheap and plentiful, also encapsulated in epoxy it isnt a health risk if you're concerned about that. Getting to arrange ballast where you want is very useful for trim or to correct any list from off center placement, reduce roll, etc.
I prefer extra battery capacity so i don't have to change my battery all day when I go to events. The other benefit of course is that it is cheaper to buy one battery vs several smaller ones. I prefer useful ballast to useless ballast.
Guess that depends how you look at it and what you value. Personally I prefer performance, swapping batteries is a small price to pay and a second set of batteries is just part of the cost of a boat, spread over running the same boat/batteries over 4+ years it isn't a big additional expense. Lead weights placed strategically in a hull isn't useless ballast, unless you think improved seakeeping and manuvering is useless, battery weight that you aren't using to capacity is.
meh, you can get lead lower in the hull than you can get a battery, check out McSpud's SD build, if that is all you're going for. However there is more to weight management than simply "low". It's a lot easier to (and you have a lot more ability to) trim a boat side to side / fore and aft (which can both significantly affect performance, ie stability, turning, acceleration, damage control, etc) if you don't have a lot of weight tied up in a battery. A lot of ships (mine included) carry way more power than they need anyway. To me it makes sense to give up some of that extra, and in the vast majority of cases unused, capacity in favor of some performance gains. You don't have to. I think that too often the conventional wisdom of "if you have extra weight fill it with battery" that gets tossed around really isn't the best solution.
If you're running an 8AH LiPO, you've got weight capacity to spare in any case. It doesn't have to be 'if you run the 8AH LiPO, you don't get to install lead weights'...
I for the most part if I need weight look to battery first... just cause its 'useful' weight. but if you have adequate battery already (or are set up to flip packs between battles, or as needed ) , the extra space to precisely place ballast .. or whatever is nice too. as mentioned above you can fine tune performance with it
What about something like this if you put it in an armored box? http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=58916
My LiPOs sit in the boat, no armored box, although they typically have a snug-fit bracket of blue camping foam to hold them in place.
