Fwd/Reverse Motor Control using DPDT's?

mneary said:

I should chime in here that a deep-cycle marine battery may be overkill. 12V 7Ah sealed lead acid batteries aren't very expensive and might fit inside your ROV. Of course you'd have to shed a lot of ballast. I don't know how big your ROV is, but in the end a small SLA should weigh (and cost about $22) a lot less than 100 ft of 14AWG stranded wire.

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I have looked into the SLA's but I guess I'm under the impression that I wouldn't be looking at very much runtime. There's an SLA I was looking at online that is rated at 18Ah for $53. Now does that mean that it will provide 18 amps of current for 1 hour of continous operation?

If I ran all three of my motors and both lights continously I will be looking right at 18A. In reality though, I would just be running the motors in bursts and most likely only two at a time. However, the 50w halogen lamps I'll be using will draw 3 amps each continuously as long as they are switched on.

If I can come up with a way to build a pressure vessel for the battery then I will probably end up going this route. Even better, if I had $120 for a marine gel-cel battery I wouldn't have to worry so much about waterproofing except for the terminals.

Thanks for the feedback!

Pcolaboy

Specs vary, but 18Ah usually means C/10 for 10 hours (1.8A for 10 hours). (but 2x50W/12V is 8.4A)

Slightly poorer under heavier load. An 8.4A load might be a little under 2 hours, depending.....

But yikes! 8.4A through 100 ft of 14AWG loses 4.2V getting to the ROV. How do your lights look on 7.8V? AWG 12 still loses about 2.9V.

These batteries are designed not to let the acid out, so I don't see any reason to expect them to let water in. Terminals are always going to be a challenge.

mneary said:

.....
But yikes! 8.4A through 100 ft of 14AWG loses 4.2V getting to the ROV. How do your lights look on 7.8V? AWG 12 still loses about 2.9V.

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Thanks for the great information and suggestions!!!

The weight and expense of an adequate SLA is still going to be too prohibitive for this project. I already have CAT-5 and 12AWG wire.

What about running two standard 12V car batteries in series to produce 24V and then some sort of voltage regulation circuit on the ROV relay board? I already have these batteries and there's more than enough room on my boat to accomodate this setup.

If I went this route, I would have two cat5's (one for control power, one for video) and one power cable bundled together for the tether in heat shrink tubing.

Thanks again,

Pcolaboy

Keep us posted on your progress. A few pictures now and then would be interesting.

3v0 said:

Keep us posted on your progress. A few pictures now and then would be interesting.

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Will do! Caution though...it may be similar to watching an iminent train wreck!