Possibly daft charging idea...

[MarkCX]

I’ve been thinking - which is not always a good thing.

The problem:

My boat lives in a muddy ditch, far from civilisation, with no mains available. I have a constant ⅔ amp load whether I’m there or not. In less than a week, my battery can be at a worryingly low SOC off-season.

What I do now:

1. I have solar (soon to be increased by 50%) which is fine for most of the year.
2. In the darker, wetter months, usually once a week, I lug a small, noisy generator down a muddy track. It then chugs away, charging the battery, while I do stuff - this takes a looong time and can only be done if it’s not raining.

I don’t live too far away, I like spending time there and I’ll probably be there a few times a week anyway. So here goes...

My proposed solution:

Get a reasonable sized, inexpensive battery with good handles, that I can comfortably carry and lift onto the boat, and buy a battery-to-battery charger.

Advantages:

1. Battery will not be as cumbersome to carry as the generator.
2. I can do this whatever the weather.
3. If pressed for time I can leave it to do its thing and pick it up later.
4. Charging battery at home is a negligible cost compared to petrol for the generator.
5. Quiet! The mooring’s on a nature reserve, so generator kind of spoils the atmosphere.
6. Not sure about this one, but can I use B2B charger for house battery when motoring?

Disadvantages:

1. I have to buy stuff - but partially offset by savings in petrol over the long term.
2. May have to take the battery slightly more often depending on capacity - but I’m usually there at least twice a week anyway.

Well that’s it. Possibly a daft idea, so totally ready for all comments, things I’ve missed and alternatives.

 

[peteK]

Get rid of the load my boats on a swinging mooring dont have any loads whilst unoccupied.

 

[Poey50]

[*]Not sure about this one, but can I use B2B charger for house battery when motoring?

Yes, and Sterling still have 60amp ones on clearance with a short warranty.

Battery to Battery Charger (used) 6 months warranty- several remaining

 

[MarkCX]

Don’t know much about this sort of thing, but would a 60amp one put too much strain on the alternator? Would it be more than I needed?

 

[Poey50]

Don’t know much about this sort of thing, but would a 60amp one put too much strain on the alternator? Would it be more than I needed?

You need about 30% higher rating in alternator than B2B. So 80amp alternator. Or you can run the B2B at half power in which case a 40amp alternator is enough or you can get a 30amp B2B.

More here.

Understanding the Sterling Power Pro Batt Ultra - Battery to Battery Charger - Marine How To

 

[pvb]

1. Not sure about this one, but can I use B2B charger for house battery when motoring?

You need to check the specifications of battery-to-battery chargers very carefully. You suggested getting a portable battery which you could bring from home, then use a battery-to-battery charger to recharge your boat battery. Most B-to-B chargers only work when the input voltage is more than about 13v, so it would work when motoring, but not when simply connected to a donor battery.

You won't overload your alternator - it will only supply as much current as it can. The B-to-B ratings are maximum currents they can handle, not a guaranteed output.

I'd agree with peteK that you ought to be able to get rid of, or at least reduce, the constant ⅔ amp load. What sort of equipment is drawing that much?

One thing you could do in winter is to have a dedicated standby battery which handles any loads while you're not there. Then bring an identical fully-charged one from home, swap the batteries, and take the depleted one home to charge. Simple battery terminal clamps would make it easy to swap over.

 

[Poey50]

But if you are thinking of charging your fixed battery with a mobile battery via a B2B that would be less efficient than using the mobile battery direct in some way.

Edit: Just seen pvb's response. Yes it would need to see 13.2v as default setting so that does rule out the use of a mobile battery as donor battery if that is what you had in mind.

 

[TernVI]

2/3A constant load? As in 666mA rather than 2 or 3 A?
I would seriously question why anyone needs this on a boat that's not going anywhere.

What's it doing? Alarms? remote monitoring?
I would suspect it can be done adequately with much less power.
A B2B charger is a poor solution anyway, because it won't fully charge the boat battery in the time you are there.

For a boat moored up over winter, we simply used to switch the two batteries over on the 1B2 switch and take one of them home to charge.
Then we got a small solar panel which was quite adequate to keep them float charged and power an SMS alarm.

 

[MarkCX]

Get rid of the load

Can’t ditch the load (0.6A). The boat’s on an isolated ‘river’ bank, with a history of scrotes nicking stuff. I have an auto dial alarm and CCTV with two-way voice.

 

[Poey50]

Can’t ditch the load (0.6A). The boat’s on an isolated ‘river’ bank, with a history of scrotes nicking stuff. I have an auto dial alarm and CCTV with two-way voice.

As others suggested swapping batteries seems the simplest and most efficient solution.

 

[pcatterall]

bang on more solar. You dont need to 'fit' it all, just use it as a non sailing temporary power source. If darkest winter is the problem then possibly a wind generator rather than solar?

 

[MarkCX]

switch the two batteries over on the 1B2 switch and take one of them home to charge.

Unfortunately the engine start battery is tiny and wouldn’t last much more than a day. The house battery is far too heavy, cumbersome and awkward to get out to take home.

 

[MarkCX]

bang on more solar. You dont need to 'fit' it all, just use it as a non sailing temporary power source. If darkest winter is the problem then possibly a wind generator rather than solar?

Any solar not ‘fitted’ would probably disappear unfortunately. Wind is a possible solution, but cost including regulator and all fittings, might be prohibitively expensive for me.

 

[pvb]

Unfortunately the engine start battery is tiny and wouldn’t last much more than a day. The house battery is far too heavy, cumbersome and awkward to get out to take home.

So have a dedicated alarm/CCTV battery and swap it every few days for a fully-charged one.

 

[TernVI]

There are plenty of SMS camera alarm systems drawing very much less current.

If you want to transfer 2/3A times half a week, that's 56Ah, in a reasonable time, you'll need to be putting it into a pretty big lead acid battery bank which will need to be significantly discharged to accept that kind of current. It's just compoounding bad choices.

 

[MarkCX]

There are plenty of SMS camera alarm systems drawing very much less current.

Do you have any suggestions? I appreciate that reducing current would be the best option, and maybe things have improved since then, but I couldn’t find anything better at the time.
Just realised I forgot to mention the MiFi hotspot I use with the camera.

 

[TernVI]

Do you have any suggestions? I appreciate that reducing current would be the best option, and maybe things have improved since then, but I couldn’t find anything better at the time.
Just realised I forgot to mention the MiFi hotspot I use with the camera.

You need to decide exactly what you require from the system.
Personally I would be looking for a useful battery life, SMS alert, pictures emailed to remote server.
Maybe it should respond to an SMS by uploading pictures.
What is the bottom line of what you need?

I know people who have a useful elvel of monitoring using 2G/3G phones on standby, these will easily run a week off a small battery if nothing happens. A week's standby if no solar power seems a reasonable requirement.
These systems are all hacked together by people I know, so not exactly off the shelf.
There are systems on ebay which have standby currents below 100mA at 5V for around a hundred quid.
I don't know what the state of the art is for an 'out of the box' system, because we can do the job using the technology of 10 years ago.
If you want to base your system on something basically unsuitable like MiFi, you will end up needing enough batteries to be worth breaking in for and nicking. Not to mention that it's broadcasting the presence of 'tech' to the scrotes.

 

[MarkCX]

Just seen pvb's response. Yes it would need to see 13.2v as default setting so that does rule out the use of a mobile battery as donor battery if that is what you had in mind.

Victron Orion-Tr Smart takes an input voltage as low as 8v. Obviously I wouldn’t go that low.
Definitely looking to be a daft idea though. Other than getting consumption down, plus my planned increased solar, I’m probably looking at keeping the status quo.

is a B2B charger a good idea when motoring anyway? Currently using a VSR to combine the two.

 

[pvb]

Do you have any suggestions? I appreciate that reducing current would be the best option, and maybe things have improved since then, but I couldn’t find anything better at the time.
Just realised I forgot to mention the MiFi hotspot I use with the camera.

OK, here's a suggestion. I'm guessing you have third party insurance cover. I don't know how far away your home is from your boat, but if you got an alert that someone was on board, how long would it take for you to get there? And even if you got there while they were still on board, would you actually want to physically confront people breaking in to your boat?

As for CCTV, well I have it at home and in my experience the police aren't interested, so I think it's of very limited value bearing in mind its cost.

You've already spent money on your system. And now you're looking at spending even more to cope with the power consumption of it.

So my radical suggestion is to sell it all on eBay and just accept the risk. This will resolve your power consumption problems and save you lots of money and aggravation in the future. If people want to steal your stuff, they will. Nothing you can do will stop that. If you try to make the boat impregnable, the damage will only be worse. Your previous posts say you've had some stuff stolen (anchor, fuel cans, etc) but if you remove expensive items if you can when you leave the boat, the potential downside is minimal.

 

[MarkCX]

What is the bottom line of what you need?

Current system for the alarm has motion detector and opening sensors on hatches. It sends a text and phones me when activated. Just a text wouldn’t wake me at night, the phone call does. The camera, which is separate, is motion sensitive, recording to an SD card and emails snapshots, and allows me to watch live. Wouldn’t really want less. MiFi doesn’t broadcast its presence, so you wouldn’t know it was there unless you were actively looking for it with more than your average phone.