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40w coolbox and Evinrude 15hp outboard.

Guest SetFair

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Hi Jim,

Halfrauds 42lt model, kicking out 40 watts. Main reason for getting this box was the price (£60, in store promotion) and the lowish (or so I thought) consumption.

I looked at Waeco ones but for a large box, they were £100's. I had a CF45 once and returned it twice to Waeco as it wouldn't cool.

The Halfrauds one does what it says on the box - "cools to 16 deg below ambient". Before the battery went flat, it was maintaining a nice 4-6 degrees.

So yes, any alternatives would be appreciated.

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Hi Paul

We bought a Waeco CF35 a short while back which is superb and is great on our batteries. The old and cheap coolbox was awful and at 12 volts will pull tons of current (5 to 6 Amps)

When you had the Waceo unit, did you set the battery sensor? The new one we have is brilliant and chills great cheerscheersbar

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Hi Set Fair,

From what you have written on your post on the YBW Forum, i assume that you only have one battery.

Therfore you appear to be using a leisure battery to crank over an engine, albeit a small engine.

Leisure batteries are not designed to have a very large amount of current drawn from them in one go, hence they do not have a CCA (cold crank amp) rating. They only have amp hour (AH) of which yours is 85.

So your o/b engine, may end up shortening the life of your leisure battery. (this will depend on how much current your engine needs when cranking)

Regading the 40w cool box which would be drawing just over 3 amps @ 12vdc on an 85 AH (assuming it still has a 85AH capacity after being used to crank an engine over)

This, in (theory) would use up the battery's capacity in 25.7 hours.

Then when the engine charged and run the cool box, the current that would be drawn through the diode / regulator on the alternator would high, as it would have the cool box pulling 3.3 amps and the battery would be drawing a high amount of current due to it being flat. The battery current draw will be a variable here, as it will depend on what state it is in.

Regarding the regulator & diodes being rated at 20 amps (which was upgraded by yourself), then i don't see a problem with that part not handling the current, but don't forget that the original was only rate at 6 amps, so it does make me wonder how much current you could actually draw without burning out the windings.

You could modify the coolbox and fit a thermostat like i have. But you will need to connect just the Peltier to the thermostat and leave the fan permantly running.

Oh, and i would recommend using two batteries (one being a leisure battery for aux only and the other being a car batery that suits the CCA of your engine)

You will then need to split the charge as well.

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Thanks to Jim and Grant for your time. More than can be said for YBW.com which seems to be aimed at the Rag & Stick brigade :wave . But let's not dewll.......

Jim - thanks for the alternative Waeco option but the cost is a major issue for me at the moment. Having just spent £100 on a seconhand Ruddersafe and a few more £'s on a rev counter plus countless other bits as you do when a new boat arrives, I'll have to save up but maybe Santa might bring something :dance .

Grant - wow, all I wanted to know about charging systems, many thanks ;) . Having always had domestic and starter batteries on my larger boats, having only one battery is something of a steep learing curve. We're going to stick with the 40w coolbox (Halfords jobbie) which did what we expected of it but we're only going to connect it when the OB's running. From what you've said, we're also going to disconnect it before staring the OB - how much of a pain is this when locks on the Thames come up every 30 minutes and you have to turn your engine off when locking.

I've toyed with the idea of two batteries ever since we bought the boat. I like the idea of a separate domestic and starter battery but wouldn't have a clue where to start with spilt charging systems. Perhaps you could guide me through this in layman's terms? It just so happens I have a spare 70ah car battery in the garage and we intend, on our next forray out over this weekend, to carry the car battery as a back up should everything go Pete Tong.

Once again, many thanks for all the advice ;)

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Hi paul,

Hope the above was ok for you.

Regarding splitting the charge to two batteries, you just need two diodes to do this.

ASAP Supplies amongst other companies sell these in a nice fancy heatsink package.

The diodes will drop 0.6v across each of them, so if your alternator is dishing out 14v, then 13.4v will arrive at your batteries.

You will need a Diode Split Charge unit that has 3 connections (1 x Alternator i/p and 2 x O/P for the batteries)

Have a look at the link to ASAP to get an idea of what you are looking for.

They have a 120 amp unit on this page to charge 2 batteries (Way OTT on the current that you will ever need, but will give you an idea)

http://www.asap-supplies.com/marine/dio ... -splitters

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Hi Paul,

Thats exactly what you need & with only a 0.2v volt drop, excellent.

To wire it in, you need to take the Alternator charging wire to the input post on the splitter, then take a lead from each output post of the splitter to your batteries.

(There will be instructions on a sheet that come with it, so this should help with the install.)

(Just remember to use cable that can handle the current when you install it)

From what you said about the original diode on the alternator only handling 6 amps, - this split charge unit will be able to handle much more current than your alternator can. so i wouldn't worry about fitting cables that can handle more than 50 amps. I would suggest around 20 -25 amp cable would be more than enough for what you want for this install.

I don't wish to complicate things for you here, but some installs will need a relay fitted (as did mine) The relay temporarily kicks in to supply 12v for the igmition circuit /exciter supply to the alternator. Once the engine is running, the relay drops out and the alternator starts charging.

The relay is controlled by your ignition switch - (The point on the switch where you turn the ignition key to turn over the starter motor and let it spring back once the engine has started)

Therefore, You turn the ignition key to pos 1 (ignition on) Then turn to pos 2 (turning engine over & relay is also turned on) Then let the switch return to pos 1 (ignition on, but now relay has switched off)

You may not need this relay, but i thought i had better mention it just in case you do.

Hope this Helps


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Thanks Grant for the advice cheersbar

Will certainly look at this at the end of the season (August? lol) and be more prepared for next year.

Once again, thanks for all your help.


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  • 6 months later...

Just a quick update with regards to the split charging system.........

Now have separate starter and domestic batteries (not new though :cry ) charged via ASAP Supplies split diode. Hardest part was working out where the alternator charge wire was in the outboard and extending it to the splitter input but had a lot of helpful advice on the YBW.com forums. No relay was required to excite the OB on startup - phew :party: .

All looks to be working as it should but will find out for cetain in the next week or so when we launch for the first time this year.

Many thanks to GrantS for his help in previous posts and for giving me some good ideas.

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