prv
Well-Known Member
Why “major surgery”? Surely it’s just one nut on the back of the alternator and one in the vicinity of the starter motor?
Pete
12v circuit refit - ideas/refinements?
- Thread starter GHA
- Start date
Why “major surgery”? Surely it’s just one nut on the back of the alternator and one in the vicinity of the starter motor?
Pete
GHA
Well-Known Member
Exactly, well almost anyway. I looked at the enclosed wiring loom on the engine and a millisecond later decided it would be big job, but you're right, would just mean running in another fat cable to the alternator.
Though not really sure there's realistically much to be gained in this application.
So onto fuses - these look interesting, any comments? Good / bad experiences?
For battery end thinking 150/200A should cover it (subject to some calcs)
Windlass already has a 100A breaker.
http://www.furneauxriddall.com/acat...f-Circuit-Breakers-VA_220_HIGHAMP.html#SID=33
Maybe something like this for the high power distro side?
http://www.furneauxriddall.com/acat...tuds---12-x-4mm-Screws-VA_189B_2.html#SID=983
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PaulRainbow
Well-Known Member
Unfortunately, you see little to be gained in any suggestions, you had already made your mind up before you posted. If you were a little more open indeed you would see that some of the suggestions made will be much simpler and more reliable, whilst still offering all of the functionality that you require, even the more "unusual" things.
There is no need to make any changes to the alternator wiring loom. You can simply connect the existing starter cable to the 1-2-both starter circuit switch that i proposed. This switch simply selects which battery you will use to start the engine.
The new, simple on/off switch, just turns the domestic bank on/off. The switch does cost a budget blowing £20 though.
I can't grasp why you think this is not a good idea. You will have dedicated domestic and engine banks, but still be able to start the engine from either or both banks, or run the domestic from either or both bank. When the engine is running it charges both banks, no matter that you don't use it often, it charges them all when you do use it and the battery isn't used for anything else.
You can then fit a breaker between the battery and the switch that's a little bigger than the windlass breaker and a correctly rated breaker for the positive busbar. No fear of the windlass tripping all of the electrics or messing the alternator up.
There is no need to make any changes to the alternator wiring loom. You can simply connect the existing starter cable to the 1-2-both starter circuit switch that i proposed. This switch simply selects which battery you will use to start the engine.
The new, simple on/off switch, just turns the domestic bank on/off. The switch does cost a budget blowing £20 though.
I can't grasp why you think this is not a good idea. You will have dedicated domestic and engine banks, but still be able to start the engine from either or both banks, or run the domestic from either or both bank. When the engine is running it charges both banks, no matter that you don't use it often, it charges them all when you do use it and the battery isn't used for anything else.
You can then fit a breaker between the battery and the switch that's a little bigger than the windlass breaker and a correctly rated breaker for the positive busbar. No fear of the windlass tripping all of the electrics or messing the alternator up.
Gunfleet
Well-Known Member
What would you have instead Paul? Genuine question. I'm interested in this as a bit of a rewire has to happen for me this winter tooI'd like to tell you to bin the 1-2-both switches, but i know you won't
.
PaulRainbow
Well-Known Member
Battery bank for the domestics with an on/off switch, same for the engine. Ideally a 3rd switch for emergency starting. A VSR or low loss splitter to allow the alternator to charge both batteries.
Gunfleet
Well-Known Member
Thanks
lpdsn
Well-Known Member
+1
If you (Gunfleet) can design your battery banks to suit their purposes that will also help (OK that may not be want you want to do at the moment). So a domestic bank as large as space (and wallet) will allow made up of batteries that can be relatively deeply cycled*. And an engine starter battery no larger than is necessary and with a high CCA.
As PaulRainbow says, an on/off switch for each. Real advantages in not charging through those switches. Third switch can either be a link switch or can switch the domestic bank into the engine/starter circuits. I have the latter, but can achieve true linking by turning both it and the engine battery on.
*Whole threads on deep cycle batteries and 'leisure' batteries, so I'll leave it there.
Gunfleet
Well-Known Member
Weirdly, for a 26ft boat I have tons of battery space available. Enough for two or more under the cockpit floor plus an engine start under the saloon floor. One of the advantages of a deep keel 4 ton yacht. Trim would be the issue from the ones under the cockpit rather. At the moment I have '1-2-off both' switch but it's in the wrong position and will have to be moved in the course of a long overdue electrical tidy up, hence my question. I think I am actually going to add another 110Ah battery to my 2x110 mounted in parallel, as the boat is on a mooring and I have acquired an Aerogen. I think with 3 domestic batts I can get away without a dump regulator.
lpdsn
Well-Known Member
Beware that if your old batteries are in significantly different condition from teh new one they'll drag it down. And of course plan the battery wiring to make sure there's equal paths to each rather than having the last one on the end of a chain. Even with thick cables, quite small differences in the resistance can have an effect on the charging of the most distant battery.
Sucks teeth re no regulator.
Sucks teeth re no regulator.
Gunfleet
Well-Known Member
Well I've tried to find the appropriate regulator but can't - the only LVM regs available are for the next generator up and cost over £200 + vat + delivery. There's a lot of stuff on ebay etc but it all seems designed for solar panels or windmills for off grid living.
prv
Well-Known Member
That's pretty much what I have, with two wrinkles:
1. I used a Blue Sea combined switch, which is electrically two separate switches for the engine and domestics, combined into one housing so that both switch together with one turn of the handle. There's a valid argument that this gives less flexibility should one side fail (eg, if the engine loom shorts out you can't run just the domestics until you've disconnected a terminal somewhere on the engine side), but I tend to prefer the neatness and convenience of a single "boat on/off" switch over the remote probability of a nearly-new high-quality electrical system mysteriously failing, and I can easily get at the batteries under a seat to make emergency disconnections if needed.
2. My VSR (SmartBank attached to a SmartGauge) performs the "emergency common" function, controlled via a button on its remote status panel, so I don't need a separate switch for that.
I'd happily endorse a row of three switches (individual on/off, emergency link the output sides of those) as suggested, though.
Pete
RupertW
Well-Known Member
All makes sense if you expect the boat to be in the hands of inexperienced people - otherwise 1-both-2-off switch is the simplest way to achieve maximum flexibility.
BabaYaga
Well-Known Member
I think it would be better designing this system with fusing considerations already from the start.
Given your choice, as I understand it, to have two batteries/banks that could alternate to act as one 'do-all' battery, to keep the two 1-B-2-off-switches and to not separate the engine starting/charging circuit, I would think along these lines:
Each battery positive post would have two connections: One thick cable, fused at 200A or so, and one thinner cable, fused at perhaps 40A (depending on charger output/domestic loads).
The two thicker cables would lead to one 1-B-2-off-switch with the engine and windlass on the COM-terminal (100A breaker on windlass cable).
The two thinner cables would connect to the other 1-B-2-off-switch, with domestic loads (including fridge), solar controller and 240V charger led to the COM-terminal, via a bus bar.
This does not solve your wish to be able to isolate one or the other battery for load testing from a chosen source, but I would suggest this to be done manually at the bus bar on these occasions (shouldn't be too difficult if preparations where made).
lpdsn
Well-Known Member
I've scanned around on the web a bit. The best I seem to be able to find for one where there's a description of how it handles overcharge is one for £145 on Amazon. It works by upping the voltage on the wind input to restrict the current rather than dumping the excess current into a shunt. I've no experience of using that type but other posters might.
dk
Well-Known Member
There are plenty around, but they can cost serious money. You'll need a charge controller that switches the charge to the large dump resistors. Alternatively, you could fit a 12V heating element to your hot water tank and dump it that way. You'll still need a VSR or similar to sense the overload and switch it over.
Gunfleet
Well-Known Member
Yes I know. Also most of those around are ac/dc regulators. The output from the aerogen is already DC. And then there’s the problem of keeping a load on the aerogen - they don’t all do that while the device needs it. By the way hot water tank=kettle. It’s a 1960s 26ft boat?. No real problem - I could get a dump resistor. Once you factor in all the parameters it makes me inclined to the three house battery solution, though it’s not my preference.
lw395
Well-Known Member
Series regulators like that are fitted to a lot of motorbikes.
The trouble is for float charging batteries you really want to be dropping the voltage to 13.5 or so once it's fully charged, unless there is some sort of daily load.
dk
Well-Known Member
You could get a car kettle and drink lots of tea when it gets windy!
Gunfleet
Well-Known Member
Thank you DK. On the other end of this (hot tea cold milk) I recently got rid of your old compressor cool box. It must be ten years since I bought it, so that’s pretty good going. Now I’m down to long life milk.
By the way the problem of needing to dump electricity isn't as bad as it's painted. According to Aerogen's manual, in a *constant* force 9 bft the generator would put out 15 amps. My measurements of the device (clamped to my shed at home with a little motorcycle battery as load) suggest closer to half that. At force 6 it's 5 amps max according to Aerogen. That's not going to overload 330 Ah x 12v. It's trickle charging.
By the way the problem of needing to dump electricity isn't as bad as it's painted. According to Aerogen's manual, in a *constant* force 9 bft the generator would put out 15 amps. My measurements of the device (clamped to my shed at home with a little motorcycle battery as load) suggest closer to half that. At force 6 it's 5 amps max according to Aerogen. That's not going to overload 330 Ah x 12v. It's trickle charging.
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prv
Well-Known Member
That assumes that "maximum flexibility" is the most important goal.
For a boat with a fixed configuration of equipment and always used in one particular mode (in my case, day-sailing with occasional night passages, rarely plugged into mains but also rarely sitting still for multiple days) there isn't that much need for great flexibility. I would rather prioritise ease of use.
I turn the boat on when I come on board, turn it off when I leave, and otherwise don't have to think about electricity at all.
GHA has a legitimate need for more options than me, but his situation is relatively rare.
Pete
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