ok now batteries

hello all i was looking at sla batteries and i was wondering do some allow more amps to be pulled per hour than others i dont see a rating for it on them just volts and ah rating .
also anyone have a suggestion on how many ah i need( to run the motors only), for a cleveland class with 2 -380 motors 1.25 props for about 1 hour at full power.

thanks all as a side note i now have my cleveland and independence plans and the first ship will be a carrier so i can hone some skills that i havent used in a while .

 

Are you talking about a C rating? That refers to the discharge rating relative to the amp-hour rating. For example, a 4.5Ah 12v battery rated at 2C discharge is rated to discharge at 9 amps, lasting a total of 1/2 hour. If the battery were rated for 7Ah at 2C, it would discharge at 14 amps, lasting 1/2 hour. If the 4.5 Ah battery were rated at 20 C it would discharge at 90 amps, lasting 3 minutes. The same applies in charging. You could charge the 4.5Ah battery at 9 amps and it would be charged in 1/2 hour, or you could charge at 2.25 amps and it would charge in 2 hours.
I don't recall seeing the C rating for SLA, but the concept still applies. The C rating is commonly given for Lithium batteries. The LiPOs I run in my planes are 2200mAh 20C 3s (11.1v) packs.

 

Cruisers can change batteries, don't think in terms of 1 hour. For your first ship, just get a car race pack and use that.

 

yes the c rating idea is what i was asking about i understand the amp draw and recharge rate are realtive to the amount of amps over a given time at a given voltage what i dont know is how high i can go on amp draw before damaging the battery also i wasnt sure how much power i needed to get thru a fight hopefully still being buoyant at the end lol do you know what amount of amp hours i need to run the 2 380 s
thru a battle to be able to change the battery pack?

 

If you want to go SLA, find one that fits your ship and use that. I's go with NiMH though. They are more power dense. For a cruiser running 380 motors, normal RC packs are just fine. I used to run my Mogami on 10Ah packs I built, but that was for campaign so I could just reload BB's and not worry about battery.

 

I would do 2 of the 3.2 V 10Ah LiFePO4 cylindrical cells in a cruiser 38120P, they handle 100A surge, hold about 10.4 Ah at a 1 amp discharge rate, and get you started with the type of battery you are most likely to want to use in your later and larger ships. They have a flatter discharge curve than SLA so your ship won't noticeably slow down during a battle like it does with SLA, and they don't go dead over the winter while in storage (If you keep the cells electrically separated from each other), and they last many years longer than SLA. They are less than half the weight of comparable capacity SLA batteries, a real advantage (2 Cells weigh 1.5 lbs and give 10Ah @ 6.4v. They run about $17 each but are easy to charge in an hour between battles if there is power near the lakeside. I think a fuse in the circuit is advisable since these cells can be used to tack weld sheet metal.

I wouldn't fool with NiMH the LiFePO4 tech is more robust in my experience.

That is the same type of cells I plan to use in an Agano (6.5 lb light cruiser) and the same cells I use in my HMS Invincible battlecruiser.

 

yes indeed those look pretty nice i dont understand the weight listed but ill figure it out it says 82.0 wh/kg whats wh mean weight?
at any rate they do have very cool specs and i like having 2 to make it easier to fit in the boat
would you use these for the receiver and servos as well

 

wh/kg would be watt-hours per kilogram, a measure of energy density. Higher energy density means you get more out of the same weight, or conversely, you need less weight to get the same endurance. LiFe cells have a higher energy density than SLA because of the different chemistry. As Ron said, those LiFe cells are less than half the weight of comparable SLA batteries, a real advantage. A quick search shows that a powersonic 10ah 6v cell weighs 4.4lbs, while two LiFe cells from Strike wired in series for 10ah at 6.4v weighs 1.9lbs.