Is This My Boat ? I'm A Frayed Knot !

[Brundall1037]

I've always wondered why these units are needed. If connected to shore and the battery charger is on is that not doing the same job?

 

[grendel]

1 hour ago, Smoggy said:

I would use ant foul instead

useful at the ant infested mooring on the river side of wroxham broad

[dom]

37 minutes ago, Brundall1037 said:

I've always wondered why these units are needed. If connected to shore and the battery charger is on is that not doing the same job?

A traditional battery charger is basically just a PSU and would work in the way you describe.

Modern multi-stage smart chargers work completely differently though and it's undesirable for them to "see" a fluctuating load. If they do, they'll keep running through a bulk charge cycle, which can damage the battery in the medium to long term. Isolating the fridge and running it directly from its own transformer avoids the issue.

[Smoggy]

9 minutes ago, grendel said:

useful at the ant infested mooring on the river side of wroxham broad

Oops! I got it wrong as well.....

[Brundall1037]

8 minutes ago, dom said:

A traditional battery charger is basically just a PSU and would work in the way you describe.

Modern multi-stage smart chargers work completely differently though and it's undesirable for them to "see" a fluctuating load. If they do, they'll keep running through a bulk charge cycle, which can damage the battery in the medium to long term. Isolating the fridge and running it directly from its own transformer avoids the issue.

Cracking answer. Thanks!

[Bikertov]

1 hour ago, Brundall1037 said:

I've always wondered why these units are needed. If connected to shore and the battery charger is on is that not doing the same job?

When you are connected to shore power, the unit is giving out 24V to the fridge so apparently the compressor runs better, and only drops it to 12V when the mains is disconnected

[Smoggy]

A danfoss compressor will run the same on 12 or 24v, I'm pretty sure the controller feeds it 12v whichever input volts used.

[Bikertov]

13 minutes ago, Smoggy said:

A danfoss compressor will run the same on 12 or 24v, I'm pretty sure the controller feeds it 12v whichever input volts used.

The EPS100 unit I have gives a 24V output to the fridge derived from the 240V mains, or whatever the boat battery output is when the mains is off

[Bikertov]

2 hours ago, dom said:

Could be as simple as a reverse polarity AC supply having been connnected. It's not unheard of for mains supply posts to be wired up reversed, which often goes unnoticed, but can cause an issue with some electronic devices. Equally, it's on a boat, so also possible it was just moisture in the wrong place.

Thanks for that - I will check the mains wiring before I reconnect it. By swapping from a hardwired connection to a plug and socket, it will then mean I can put a mains tester on to check the L/N polarity before proceeding.

I do know that the marina feed and my shore power are the correct polarity

[dom]

9 minutes ago, Bikertov said:

The EPS100 unit I have gives a 24V output to the fridge derived from the 240V mains, or whatever the boat battery output is when the mains is off

Do you know if the fridge has a Secop BD35F compressor? If so, I think it has two input voltage bands within which it operates. It cuts off if voltage exceeds the overvoltage threshold, or if the battery hits the low voltage cutoff. Within the bands, the output voltage to the compressor should remain pretty constant. I think you can adjust the various voltages with a hard-wired resistor, but I last dealt with Waeco getting on for 10 years ago and mostly in caravans, so may have that wrong.

I think the EPS100 was probably made the way it is so it can serve both fixed 24v and dual 12/24v units. We used to sell a very similar unit with a cigar socket for running coolboxes.

 

[Bikertov]

30 minutes ago, dom said:

Do you know if the fridge has a Secop BD35F compressor?

...

I think the EPS100 was probably made the way it is so it can serve both fixed 24v and dual 12/24v units. We used to sell a very similar unit with a cigar socket for running coolboxes.

 

Yes, the EPS100 has a 12V cigar lighter output too

https://www.jacksonsleisure.com/caravan-motorhome/dometic-waeco-eps-100-12-24v-mains-adaptor/

I will check the fridge and compressor model at the weekend

[dom]

I suspect the info about running better on 24v probably comes from more basic chilled coolboxes. You can probably tell - if the compressor's running harder on 24v, I should think you could probably hear a pitch change when you connect 240v.

The BD35F compressor speed can be changed, but it's controlled by a fixed or variable resistor between the thermostat and control unit.

[Bikertov]

So, this is how my day went at the boat today:

I got to Jones at around 10:00, and as it was still quite cold and damp while I waited for it to warm up a bit (before doing the anti fouling) I took the opportunity fit a new bow thruster anode.

It is a specific fit for my Side Power (Sleipner) unit. The anode was ordered earlier in the week from Forum sponsor JPC Direct. It is a tiny conical thing, 25mm diameter at the base, and the postage was going to cost more that the anode itself. But a quick polite call to JPC and they did a deal on the postage, reducing it by half.

I tried screwing the fitment screw in to the end of the thruster (4mm hex head), but not wanting to overtighten and strip the thread, the anode was not held firm and was spinning around. 

Looking into the screw hole, there seemed to be deposits in there stopping the screw from going fully in. I scraped out as best I could with a small flat blade screwdriver, and then a mini wire brush attachment for my cordless Dremel. The bottom of the hold was now visible, and at the same time I also cleaned the mating surface where the anode meets the thruster. This done, the screw just went in that little bit more, and could secure the anode.

The fitting information on the Sleipner website said to use thread-lock to keep the screw in place. So I asked in the chandlery shop if they had any, and they tried to find a tube in the workshop I could use, as it only needed a few drops. They couldn't find any, so they very kindly gave me a tube from the shop, and said to bring it back when I was finished and they would put it in the workshop for them to use. 

In all, it took an hour just to put a little anode in place, with one screw. Not a good start ...

I spent the rest of the day doing the anti fouling (more details to follow on the anti fouling thread) and finished up just after 5pm.

A long and physical day, that I am sure to feel by tomorrow morning.

 

[Bikertov]

Following on from an earlier post, this is the back of my fridge, showing the Danfoss BD35F compressor, being a 12/24V unit.

 

 

I refitted the Waeco fridge rectifier - the picture is looking up from the bottom of the under-sink base unit.

The mains junction box was moved, and a piece of flex added to allow a new single socket to be fitted, along with a plug on the end of the unit mains flex. I had to fit the socket upside down, as the flex from the unit had previously been cut too short. With the socket in place instead of the previous hardwired connection, it means I can easily isolate or disconnect the unit in the future.

It all seems to work now, so I can power the fridge from 240V shore power (or the inverter), or just the 12V house battery. When on mains, the output ramps up to 24V, and drops back to 12V battery voltage when the mains is disconnected.

In an ideal world, I would move the plug and socket (and maybe the unit as well) to a more accessible place in an adjacent cupboard, as currently I have to pull out the fridge to get to it all. But for now it will have to be OK