R/C Naval Combat

How do you know how many batteries to buy? I'm thinking of going with NIMH's, to save on weight and because of their better power curve. If I bought a few 5 amp-hour packs, and hooked them together in parallel, how many would a ship like mine need?

I'd imagine that depends on how efficient your ship is electrically. I think most ships that size are usually powered by SLA type batteries, which are also far cheaper then the NiHMs.

In a class 5 ship like The Duke you should have at least 20 amp hours. If you're using NIMH then 25-30 amp hours is easy to do.

25-30 amp hours of NiHM is going to be EXPENSIVE though.

So, when I link the packs in parallel I just add up the combined amp hours?

My ID is using 4, 5 amphour packs in parallel, to give 20 amps for the drive system, receiver, and firing system. I then have 2 packs in parallel for the pump. I like to isolate the pump from the rest of the system, since my pump is a tad bit crazy on the amount of amps it draws.

I found that after 2 sorties at Nats, I never used over 9 amps on the 4 packs, so I will be trying just 2 packs at the next Savannah battle to save the 1.4 pounds. Of course that will give it a little more freeboard for them to shoot at.

The 5 amp packs run around $30 a pack, and Mike is right it can be expensive. If you are just starting out, go with some SLA, untill you can afford the additional cost. I need 12 packs to run my ID for the day, and those cost quite a bit, even making them up myself.

What about voltage? The drive motors say they run on 6-12 volts. Does it matter what the batteries deliver, or does the ESC just do that for you?

ESCs dont change the voltage delivered by the batteries, only the duty cycle. So for motors that are rated 6-12 V use some battery combination that is 6-12V, the higher you go youll get more power but are more likely to burn out the motor as well. 6V systems are currently standard but there are some good arguments to move to higher voltages and with some of the new battery technologies I would expect to see more people running ships at more than 6V in the future.

It seems like a lot of packs run at 7.2 or 8.4 volts. Would that work for me?

When building your first ship it's best to use what others have tried and had success with first. Not only are there good systems for you to copy but when something of your breaks at a battle someone will have a spare on hand or be able to help you fix it. If you're then only one with system X help and parts are going to be hard to find.
There are a few guys in the club running at 7.2 or 9.4 volts. But not many. Start with the 6 volt packs. You can always rework them to a higher voltage latter. If you go with NIHM I like the 10 amp hour packs better then the 5 amp hour packs. They can be used in a cruiser (1 pack), small BB/BC (2 packs) or big BB/BC (3-4 packs). I think the overall cost is less, as you're buying less cells, but you'd have to look around to prove that. You also have less packs to charge, less chargers to buy too.

Good point, I guess that would be better. Where do you get a 10 amp hour pack?

I think we got ours from batteryspace.com. I think they had an e-bay sale.
If you look around on the web for 10 amp hour NIMH cells you should find a good deal somplace. Get the batteries in premade packs or at least with tabs to make your own. Without tabs soldering them together is a lot of work.

I got my 10 Ah, D size cells from eBay for a half decent price (around $35 per batteyr pack). I use 6 cell packs instead of 5 cell packs for the extra voltage to run the solenoids I have in my two cruisers. The packs are used in a Lutzow (13lbs total weight) and a Gloire (9.5 lbs total weight). A pack will easily last 4 sorties in my Gloire.

Bob, you are an animal. Non-stop boats on the brain.

I like SLAs. 2 12 amps are good for ballast and last even for long battles. And they are cheap which is important when you have a big fleet.

PS: Jake is talking NATs next year if it works out. One more allie!!!!!

John B.

I was looking at that, but I'm concerned about weight- David said his Iron Duke barely had enough freeboard with nimh batteries.

I also heard that the SLAs have a worse power curve.

Does anybody know if SLAs degrade over time, like NiCads do?

Yeah, all batteries degrade over time, its just a matter of how much and how fast. SLAs don't degrade as fast as other types from what I understand.

So, what all is involved in making your own pack? do you just soldier the cells together in series until you get up to 6v? Then combine the mAh?