12v circuit refit - ideas/refinements?

Not a lot of load, my boat was only 25ft with small yanmar with 30amp alternator, no windless or fridge. My friends boat had larger engine, 80amp alternator. His was failing on batt 2 position.

Not sure about the failure rate of these but know of a few more locally that are playing up but still operational.

There must be ongoing failures as they are stocked by chandlers and most new boat for a few years have not had them fitted from what Ive seen so cannot be going there.
 
Last edited:
GHA said:
Does that ever happen? Never heard of one burning out but would be nice to know if it's a common problem - any details of any incidents anyone?
Click to expand...


I'm not being defensive and i'm perfectly chilled, thanks.

Yes, they do fail and yes, on/off switches fail too. The point is, if you 1-2-both fails at a critical moment, you could be in trouble, i just turn a switch and carry on.

You keep talking about keeping batteries charged and cruising boats, my comments have nothing to do with either, as such. You might have missed it, but i omitted the charging circuits in my diagram, my focus has been reliable battery systems, with maximum redundancy.

FWIW, my own boat is a cruising boat. I spend most of the time onboard and i have a good understanding of the systems needed to run a cruiser. My boat systems are very power conscious and i have long range fuel and water capabilities. I bought the boat last year and have been modernising things, in Feb this year i replaced the batteries, uprated the solar panels, fitted a new controller and all charging wiring. I have a 30a battery charger, quality battery monitoring and automated mains charger capability, which could just as easily be simple low voltage alarms. From Feb to Sept i was 100% self sufficient in terms of power. From Sept i have had to supplement the solar yield with some shore power charging (if i was at anchor my alarms would alert me to the low voltage and i'd run the genny in the evening for an hour).

So, you are correct that no single solution will suit all boats, i've never said it would. Where you are incorrect is to claim that i, and everyone else except Roger, has no understanding of cruising boats.
 
GHA said:
Not at all, nothing was rejected out of hand, just that none of the comments come from a cruising boat perspective,
Click to expand...

Having reread this thread a couple of times, I think that you perhaps would have received better comments if you had been even clearer about how different your setup is from most cruising boats and how special your priorities are.
I think most posters to this thread have a 'cruising boat perspective', but that is a very broad category of boats.
For instance, mating 300W of solar to a 225Ah battery bank may appear a bit odd to most people on here, as well as the ambition to cycle the bank between 100 and 80 percent and having battery life time as no 1 priority.
Not claiming this is wrong in your situation, which I know nothing about, but surely different from how most of us use our boats.
 
Last edited:
GHA said:
Not at all, nothing was rejected out of hand, just that none of the comments come from a cruising boat perspective, Roger's the only one who knows what he's talking about.
Prime example is everyone getting into a big row about their favourite switch and no one person interested in how to keep lead acid in best condition.

Oh well so it goes :)
Click to expand...

You gotta laugh.
 
PaulRainbow said:
View attachment 67615


Hopefully this makes it clearer. I left the solar wiring out for clarity. Wasn't sure if you had a shunt, but i included one anyway, if you don't have it just use a straight cable. All of those negatives are connected to a post, a stainless bolt is fine. Also left the mains charger off, but that's simple.

In normal use the domestic switch is on or off. The engine switch is on (1) when you want to use the engine. Both circuits are isolated, both banks charged by the alternator via the VSR. Starting the engine will not cause voltage drops on the domestic circuit. There are no changes to the current starter/alternator cable, charging goes to the load terminal of the engine switch, if you have to run the engine from the domestic bank the alternator will still charge.

The 1-2-both switch allows you to select (1) for normal use, (2) if the start battery is dead flat or knackered, or (both) if it's just a wee bit flat.

If the domestic bank suffered a catastrophe, isolate it and select (both) on the engine switch.

Domestic bank to isolator breaker circa 240a (may need to upgrade the cable to the switch). Windlass breaker, whatever it needs, but less amps than the one from the battery. Switch to domestic busbar whatever you need. This arrangement overcomes the previous fusing concerns, such as the windlass tripping all of the domestic circuits.

Oh, your VHF won't go off when you start the engine :encouragement:
Click to expand...


Ok. Then let us say the VSR is sensitive to the hotel battery. A charge current is introduced to the hotel battery the threshold voltage of the VSR is now reached. Due to the extra load the voltage is depleted and the VSR disconnects (chatter). Must be a simple fix?
 
35 years with about 9.5years per set of batts and.... No solar regulator! Omg they gonna die.... ;) worth listening to everyone, including those that actually do it long term off grid. Though no solar reg maybe not such a good idea these days , just as easy nowadays to achieve same "mini equalising " just with a parallel switch around the regulator to take it out of the circuit or use your regulator wifi app to up absorption to 15.5v.



 
third engines said:
Ok. Then let us say the VSR is sensitive to the hotel battery. A charge current is introduced to the hotel battery the threshold voltage of the VSR is now reached. Due to the extra load the voltage is depleted and the VSR disconnects (chatter). Must be a simple fix?
Click to expand...

A decent quality VSR won't chatter, they are more than just a simple relay.
 
GHA said:
35 years with about 9.5years per set of batts and.... No solar regulator! Omg they gonna die.... ;) worth listening to everyone, including those that actually do it long term off grid. Though no solar reg maybe not such a good idea these days , just as easy nowadays to achieve same "mini equalising " just with a parallel switch around the regulator to take it out of the circuit or use your regulator wifi app to up absorption to 15.5v.

Nothing in your original description has much (if any) bearing on how you will be able to fully charge your batteries or maintain them between 80% and 100% SOC. If you have 300w of solar power and only 225ah of battery capacity, then you clearly have an issue and that issue is not addressed in any way by anything discussed in this thread. This thread only deals with your battery wiring and fusing, along with system reliability and redundancy, which you fail to grasp.

If you want to deal with battery life, SOC and charging regimes, that's a whole different matter. The first thing you need to do is increase the capacity of your domestic bank. It's too small for a permanent live aboard cruiser. If you don't want to go below 80% SOC that means when the solar stops charging your batteries need to be fully charged, with 300w and 225ah yours should be fully charged well before the Sun goes down. You then have about 40ah (assuming your batteries are absolutely perfect, which they won't be for long) to see you through until the solar panels start charging again. Your panels are capable of charging a much bigger bank than you have, you could double it. If you did double the ah you halve the amount you discharge the batteries during the night.
Click to expand...
 
If you want to deal with battery life, SOC and charging regimes, that's a whole different matter. The first thing you need to do is increase the capacity of your domestic bank. It's too small for a permanent live aboard cruiser. If you don't want to go below 80% SOC that means when the solar stops charging your batteries need to be fully charged, with 300w and 225ah yours should be fully charged well before the Sun goes down. You then have about 40ah (assuming your batteries are absolutely perfect, which they won't be for long) to see you through until the solar panels start charging again. Your panels are capable of charging a much bigger bank than you have, you could double it. If you did double the ah you halve the amount you discharge the batteries during the night.
Click to expand...

Bit of guesswork there, Paul...;)

I was all set to buy a 2nd pair of trojans but after adding solar to 300W, surprisingly it turned out there was little point. More days than not up to full charge again based on less than 1% capacity in aH being enough to push the voltage up to 14.8v double checked with SG readings on all cells.

Overnight consumption rarely takes the 2 x t105's below 80%, below is a typical accurate voltage at the battery terminals for a hot August even with the fridge being greedy. Voltage under load rarely gets below 12.5v in the mornings. That's running fridge, Raspberry Pi all the time,music, bright LED anchor light and laptop for a good few hours most evenings.

You can see where the laptop was turned off and the voltage increased a little with less load on the first night at left of the plot. Fridge cycling is easy to see.
With only discharging to 80% on one bank, doubling battery capacity would lead to little increase in power going in, only dropping to 90% might mean a little bit more maybe before the acceptance rate drops below current available but not a great deal.

Little to be gained in the real world.

Graph was before upgrading to MPTT regulator, things are even better now with absorption set higher.
Winter means running a genny every couple days to catch up with lower sun or sun being behind the hills if up a river.

t8Ra3jD.png
 
Last edited:
You must log in or register to reply here.

Other threads that may be of interest

Y
The Seafarer 700 and NASA clipper sounders saga
Replies
10
Views
430
Dellquay13
Dellquay13

Share this page

Top