Outboard output - Charging

Explore Cowal · 01 September 2016, 22:01

I've got a 20hp Honda BF with a 12v power output at 6A. It's fitted to my SIB and I'd like to be able to top up air whilst on the water, charge phone etc.

I got this cable with the outboard. Is it as simple as just connect to outboard and battery terminals? Or is there a requirement for some kind of regulator.

I've been looking at batteries, however weight comes into the equation so don't want to go leisure at 18kg for 60Ah. I've found a few batteries at 40Ah which weigh in at 10-11kg, which would be acceptable. But would it work in the way I intend? If the 40Ah would suffice day trips I could charge the battery at home

Any advice welcome. Thanks.

Poly · 01 September 2016, 22:17

You'll need to consult a manual (or stick a meter on it - preferable with a load like a big bulb on the terminals).

There are two possibilities 1. It's a charging circuit - most likely if it has electric start too. This will be regulated and you can stick the battery on it. It will be D.c. And with a load on there shouldn't go much above about 14.5volts; 2. It's actually just a "lighting coil" which means it will be unregulated (higher volts at higher revs) and probably also unrectified (so will give odd readings on a DC multimeter).

Oh, and the 40ah will be more than adequate.

Explore Cowal · 01 September 2016, 22:49

Quote:

Originally Posted by Poly

You'll need to consult a manual (or stick a meter on it - preferable with a load like a big bulb on the terminals).

There are two possibilities 1. It's a charging circuit - most likely if it has electric start too. This will be regulated and you can stick the battery on it. It will be D.c. And with a load on there shouldn't go much above about 14.5volts; 2. It's actually just a "lighting coil" which means it will be unregulated (higher volts at higher revs) and probably also unrectified (so will give odd readings on a DC multimeter).

Oh, and the 40ah will be more than adequate.

Thanks Poly. I don't believe it has an electric start so I'll assume it'd be the latter of the two options you've highlighted. Will it still serve as a charger as is or is it to volatile, or perhaps only charge once above a certain RPM? Ta.

Nos4r2 · 01 September 2016, 23:00

Don't assume anything til you've looked at a manual.

I don't think that's an AC lead you have there though, Honda used to use red for +ve and green for -ve on motorcycle electrics so it's as likely to be proper rectifed DC. Hence, you REALLY need to look at a manual.

Explore Cowal · 01 September 2016, 23:54

Well after turning the house upside down, much to the wife's delight I found the manual.

It's a charge system

with 20amp fuse.

Thanks.

Last Tango · 02 September 2016, 09:19

That's pretty straight forward but if you don't have electric start I wouldn't go as big as 40AH if weight is an issue.
Something about half that size would do. (about 20AH) eg lawnmower battery?

Lawnmower Battery Powerline 12V 20Ah - (Replaces F19-12B ) | eBay

Fenlander · 02 September 2016, 09:43

Agree re downsizing the battery. For just topping a phone or running a fishfinder/GPS etc even as low as a 12ah would probably be fine.

With no charging on my OB I use a 7ah for the plotter and even left on all day that never runs low, I have a 12ah for the Bravo pump and that will do more than a whole air floor SIB inflate before that needs charging.

Last Tango · 02 September 2016, 12:51

Another idea for you....and the cover actual looks waterproof on this one.

Waterproof Dual USB Charger Adapter Socket 12-24V Outlet Power Supply Boat BI347 | eBay

Explore Cowal · 02 September 2016, 13:38

Thanks for all the input. Referring to the manual it details 35Ah upwards, wonder why that is? think I'll fit a car stereo, amp and some speakers as well,ha.

I'm intending on housing the battery and associated electrical doodahs in a large tool box. I will also be able to store my pump and other marine item in it.
My mate gave me this, it's got a 12v socket, volt meter and USB sockets. There's a lip on tool box so I'll install it just below to help prevent water ingress, although it's meant to be waterproof. I'd have a switch with fuse between battery and the trio.

If I pull the handle up on the toolbox it'd be like an A frame on my wee SIB

Sure I've got a 4 gang cig lighter adaptor somewhere, I could fit that internally if the weather didn't suit external charging.

Last Tango · 02 September 2016, 16:21

Quote:

Originally Posted by Explore Cowal

Thanks for all the input. Referring to the manual it details 35Ah upwards, wonder why that is? think I'll fit a car stereo, amp and some speakers as well,ha.

.

It might be that the output is rectified but not regulated.(That used to be the way 30-40 years ago). but I would doubt it. East way to check is meter the output...no battery connected...and see what the voltage goes up to when the engine's revd.
If it self-limits at around 14.5V then it's regulated if it goes significantly above that it's not, and it's using the battery to regulate the voltage. A bit naughty because there's implications for a sealed gel battery of any size if that's the case.
Obviously I'd not advise you to do anything that contravened the instruction manual but if it was me and the supply is regulated, I'd down size the fuse (10amps) and put what ever battery I wanted on it.