Reengineer the electrical system

[Bob666]

Hi!

Got a 70s boat. Norlin 37, recently bought.

4 x Gel batteries from 2013. 300 Ah. Stern section. This is the major battery bank.
1 spare battery in bow section. Gets charge when land power attached only, via battery charger. Not charged by solar panels or engine alternator. idea of previous owner: Used if major battery bank of gel batteries fails, to crank start engine.

Will add plenty of solar panels and bow anchor windlass.

Emailed previous owner. He suggest adding yet another bow section battery for the windlass.

Dubious. His setup is one major battery bank only, it also cranks the starting engine. Less complicated than two battery banks. I agree.

I have some questions:
1. Not sure why the solar panels shouldn't charge that stern battery.
2. Why have that extra battery, really, not used for anything, except emergency start.
3. Ok it's a precaution, keep it, but why not use it for the windlass. Adding a 6th battery doesn't make sense to me. If use it for windlass, I should probably make sure it's getting charge also from solar panels and alternator?
4. Or should I could keep the reserve battery as it is, and use really thick cabling from stern battery bank to windlass? I will start the engine when using the windlass anyway.

I don't have time for major refits/total electrical system overhaul, will add-on in ad-hoc fashion rather. But it things are crazy they need to be re-engineered.

I will replace the current 50 A alternator with a 100 A alternator and replace some cabling with thicker cabling.

Cheers

[skipmac]

The does sound like a very odd setup.

My opinion, the simplest setup but adding reliable engine starting.

- One house bank with suitable capacity for your power needs

- Separate, isolated starting battery.

All charging sources wired directly to the house batteries with an automatic combiner that connects the start battery only when there is charging voltage present.

A lot of people add a separate battery forward for the windlass but I think this adds more wiring, more complications and really only makes sense with a very large boat where the cables from the house bank would be very long.

[Steve Bean]

If the "bow section" battery is used for engine starting, it should have some robust cables to handle starting amperage.

[Bob666]

Hi!

I want to take the lazy approach. Not reengineer the whole electrical system. Last boat I did that and documented everything 1-1 <-> 2-1 etc in MS Visio. Took ages! And I believe simpler to actually write what to what in normal words, not numbers and having to look in another document what "1-2" means.

What if I stick to one battery bank. The extra bow battery could also be charged via the solar panels and alternator by putting a diode on the plus side towards it, and it can be used by the windlass AND be a reserve starting battery? Bad-ass plus and minus cables to it. Total: 5 batteries.

I will replace the parallell coupling cables of the 4 Gel batteries with fatter ones. I had 70 mm2 on previous boat. Perhaps overkill, what about 50 mm? Short cables, longest is 0,5 m as the fourth battery is a bit on the side from the other three. As I will replace the alternator from 50 A to 100 A I could check out the cable thickness there as well.

One thing I noticed is that the voltage drop from the electrical panel to the cockpit is substantial. Much lower in the plotter than at the batteries.

How do you go about designing the targa arch in the stern, the one I can put solar panels on top of? I have no experience of construction and strenght optimizations. Need to get in contact with somebody knowledgeable, how much can the solar panels protrude aft of the arch and how proper must they then be held up by welded arms attached somewhere on the aft side of the arch.

I have found at least two good welders of marine aluminium (need to keep weight down so rather than stainless steel). But they are not designers of the ultimate solar panel arch, I should find some kind of engineer for this job. Perhaps there exists designs already? If I knew the recommended angles, thicknesses and ratios (max and min lengths etc) I could modify to my needs.

Cheers

[Bob666]

Originally Posted by Steve Bean

If the "bow section" battery is used for engine starting, it should have some robust cables to handle starting amperage.

There's starting cables in the boat. One has to lift the battery and put it near the engine. Currently.

[skipmac]

If you plan to take the lazy approach make sure your towing insurance is up to date. One of the forum members, GordMay has this as his signature line.

"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

It isn't really that much time and work to do a little rewiring. Buy the parts and you could do it in a day. To get a workable system you don't really need a complete "reengineering" of the system. Moving a few wires around, maybe adding a couple of new wires and a couple of parts will get you in much better shape.

[Bob666]

Ok you two guys perceive one house bank for all purposes as an incorrect solution.

I do not necessarily do that (it's not black and white) and hence humbly ask an opinion from somebody who would consider such a scenario valid.

Seriously, KISS is my motto, and I will sail away without radar for example. Electronics are notoriusly untrustworthy, they're all made in China = ****.

The less electronics the better!!! Two house banks = more complex.

Cheerz

[skipmac]

Originally Posted by Bob666

Ok you two guys perceive one house bank for all purposes as an incorrect solution.

I do not necessarily do that (it's not black and white) and hence humbly ask an opinion from somebody who would consider such a scenario valid.

Seriously, KISS is my motto, and I will sail away without radar for example. Electronics are notoriusly untrustworthy, they're all made in China = ****.

The less electronics the better!!! Two house banks = more complex.

Cheerz

My setup and recomendation is one house bank, one starting battery.

One house bank is the KISS version and healthier for your batteries.

Isolated starting bank so you can always get the engine cranked.

All charging goes to the house bank because:
- unless you have a problem the engine starting battery uses very, very little charge to crank the engine.
- the house bank on the other hand usually expends lots of charge running fridge, lights, radio, electronics, etc.

The foolproof and very simple setup to keep the start battery charged, connect an automatic battery combiner between the house banks and the starting battery. When the house batteries are being charged, the starting battery also gets charge. When the house batteries are no longer being charged the start battery is automatically disconnected so is isolated and will not be run down because someone forgot to change a switch. Some people are perfect and never forget and can use a switch but I'm not one of them.

[Stumble]

One massive battery bank is far better than two small banks. The smaller the draw on batteries (as a % of capacity) the slower the banks are drawn down, and the larger the effective capacity. That being said a stand alone battery (not bank) just to start the engine is good insurance against doing something stupid.

The other option is to use a lithium battery portable jumper system that charges off the inverter. It won't discharge to the system, and stays fully charged, hopefully forever. Just make sure (test it) that it can start the engine.

[Bob666]

Skipmac, Stumble. Thanks for your input. I didn't mean two house banks, I meant one house bank + one starting battery. Sorry.

Ok so maybe better with that setup. Just curious what the previous owner thought when he designed this system? He was an electrician (high voltage, they don't always do things right with 12 V systems I've noticed). I cannot ask him unfortunately.

Total overhaul out of the question. I will keep the original power panel with glass fuses and switches. It does the job for non-critical applications such as LED interior lightning and stuff.

I found a windlass I am considering to mount in on the bow:
Bada ankarspel 1200W till båtar på 40-65 fot | MarineOnline.se

1200 W = 100 Amps. Tough one. If I use cabling from the house bank in the stern it has to be 95 mm2 at least. I could use the fifth bow battery for this and have shorter less thick cables. When running the windlass, I will start the engine. I wonder how many amps will be flowing from the Engine alternator (will replace current alternator of 50 A with a 100 A), i.e. how thick must the cables from the alternator to the fifth bow battery be, please? Not sure about its capacity but for the sake of argument let us assume it is at 75 Ah, would be quite typical.

Would you know how much current you can charge with maximum then? Is it 10% of the battery capacity? The charger in the boat delivers up to 30 Amps I believe, saw it delivering 10 A to the house bank when I connected shore power. 30 A would make sense as the house bank has 300 Ah. That would mean the bow battery would get to much current? Or has the previous owner limited the current someway (possible?) to just that battery?

And keep current setup = use the house bank to start engine. (Ok I will consider adding a sixth battery near the engine. Maybe.).

If I take the route of one house bank + a starting battery. It's a djungle how to do it. There's the relay/switch approach (I need to read up) = old-fashioned. Perhaps more robust. And there's all these new "CTEK dual Smartpass" gadgets etc:
Battery chargers | CTEK
But what if that fancy CTEK breaks in the middle of the Atlantic? Better to have a few cheap relays and replace a broken one? Do it the "70s way"? (Just have to learn it).

Would you know why the Volvo Penta 2003 manual says to not use more than one battery at 70 Ah for the starting engine? Isn't it the index finger that kills most starting engines?

Solar panels. There's two regulators for two small solar panels on the boat. Not enough amps rating for the 300 W I want to add on a stern arch. I will add a MPPT and connect the 3 x 100 W in serial to reduce cabling cost. I believe the sun will shine on all three back there on the arch, most of the time. Thermal fuse.

The house bank is not very well ventilated and will probably get quite hot in the tropics. And there's no temperature sensor involved. Do you need that when charging from solar panels and alternator or only when shore power + battery charger?

[skipmac]

Hi Bob,

For simplicity comments below.

Originally Posted by Bob666

Skipmac, Stumble. Thanks for your input. I didn't mean two house banks, I meant one house bank + one starting battery. Sorry.

One house, one starting can be considered two banks, just dedicated for different uses.

Ok so maybe better with that setup.

After being left without enough juice to crank the engine a couple of times,once 100 miles from nowhere with no possibility of assistance and no alternate ways to charge the batteries, I'm really big on having a dedicated starting battery. Also an automatically isolated from the system starting battery. A common setup it to have two battery banks and a 1-2-Both-Off switch. 1 for house, 2 for start, Both when charging. The problem is, you have to remember to switch from Both to 1 when you anchor for the night and turn on the stereo. Forget and the next day you might not have starting. You might guess how I know this.

Just curious what the previous owner thought when he designed this system? He was an electrician (high voltage, they don't always do things right with 12 V systems I've noticed). I cannot ask him unfortunately.

I've seen all kinds of strange wiring setups including the one on my boat when I bought it. Many of the worst were done by "experts". At this point nothing in boat wiring surprises me.

Total overhaul out of the question. I will keep the original power panel with glass fuses and switches. It does the job for non-critical applications such as LED interior lightning and stuff.

Glass fuses and switches are just fine. They do the job quite well. Just keep plenty of spare fuses of all values. I've gone through 10-15 fuses before trying to solve a problem circuit so you can sometimes burn through the fuses much faster than you think.


I found a windlass I am considering to mount in on the bow:
Bada ankarspel 1200W till båtar på 40-65 fot | MarineOnline.se

1200 W = 100 Amps. Tough one. If I use cabling from the house bank in the stern it has to be 95 mm2 at least.

95mm2 is a really large cable. How far do you have to run the cable from the main battery bank to the windlass and how much voltage drop are you allowing?

I could use the fifth bow battery for this and have shorter less thick cables.

For large boats and/or large windlass loads it starts to make sense to have a separate battery for windlass loads. Since you already have one battery forward it might make sense to use that one for the windlass.

When running the windlass, I will start the engine. I wonder how many amps will be flowing from the Engine alternator (will replace current alternator of 50 A with a 100 A), i.e. how thick must the cables from the alternator to the fifth bow battery be, please?

How many amps running to the battery will depend in part on how discharged the battery is. However, if the battery is charged will the power to the windlass come from the battery, the alternator, both? Both I'm sure but not sure what ratio of the power would come from each source. Worst case scenario, 100 amps might be flowing through the cable from the alternator so I would size the cable accordingly.

Not sure about its capacity but for the sake of argument let us assume it is at 75 Ah, would be quite typical.

Would you know how much current you can charge with maximum then? Is it 10% of the battery capacity? The charger in the boat delivers up to 30 Amps I believe, saw it delivering 10 A to the house bank when I connected shore power. 30 A would make sense as the house bank has 300 Ah. That would mean the bow battery would get to much current? Or has the previous owner limited the current someway (possible?) to just that battery?

This will depend on what kind of battery. An AGM type can safely accept a higher rate of charge than a regular liquid acid (called a FLA flooded lead acid). 10% of the battery capacity is a reasonable limit for FLA batteries. As it reaches full charge a battery will self limit how much charge it takes. Batteries have an internal resistance that increases as the battery is more fully charged. So a discharged battery can take a lot of charge but once it gets to 80% the resistance increases and the charge it will accept decreases.


And keep current setup = use the house bank to start engine. (Ok I will consider adding a sixth battery near the engine. Maybe.).

If you have the spare battery in the bow and a backup way to charge the house batteries you could just use them for house and starting. You just run the risk of not having enough power to start them immediately.

If I take the route of one house bank + a starting battery. It's a djungle how to do it. There's the relay/switch approach (I need to read up) = old-fashioned. Perhaps more robust. And there's all these new "CTEK dual Smartpass" gadgets etc:
Battery chargers | CTEK
But what if that fancy CTEK breaks in the middle of the Atlantic? Better to have a few cheap relays and replace a broken one? Do it the "70s way"? (Just have to learn it).

Here's what I use. Combiner 100 Sheet There are similar products from other manufacturers like Blue Sea Systems. These devices have a very good reputation and are generally very reliable. If one fails a jumper cable or manual switch can serve until you can do a repair.

Would you know why the Volvo Penta 2003 manual says to not use more than one battery at 70 Ah for the starting engine? Isn't it the index finger that kills most starting engines?

The manual says specifically 70 Ah? Ah (amp hour) is a measure of how much power you use. 70 amps for one hour or 140 amps for 1/2 hour totals 70 Ah. Maybe the manual means don't use more than 70 Ah of power trying to start the engine as more will overhear the starter? So yes, it is the index finger that kills the starter. The starter doesn't care if you have a really large battery connected, it will only use what it uses. Just like a bulb in a flashlight. It will work the same with AA, AAA, C or D size batteries as long they are the correct voltage.

Solar panels. There's two regulators for two small solar panels on the boat. Not enough amps rating for the 300 W I want to add on a stern arch. I will add a MPPT and connect the 3 x 100 W in serial to reduce cabling cost. I believe the sun will shine on all three back there on the arch, most of the time. Thermal fuse.

The house bank is not very well ventilated and will probably get quite hot in the tropics. And there's no temperature sensor involved. Do you need that when charging from solar panels and alternator or only when shore power + battery charger?

A large charging source whether a shore powered charger, solar panels or alternator, can overheat the batteries. It isn't the source it is more the amount of charge. A temp sensor is a good thing to have.

[Bob666]

Steve Bean, Skipmac.

If I cannot know whether the windlass takes its current from the bow battery and/or the alternator, I should put fat cables from the alternator to the bow battery.

By doing so, why not creating a true dual bank system:
1 x bow battery. Function as starting battery and windlass battery.
1 x house bank (4 x gel batteries).

Either way, I have to have fat cables to the windlass, so might as well take that approach, right?

If I go down to, say, 50 mm2 cables. There will be a voltage drop. I heard you can mount electronics that measure that drop at the bow battery and charge accordingly. I will not run the windlass very long so if the 50 mm2 cable gets slightly warm, maybe not a big deal? I will put fuses where required of course.

I will also mount NASA and it can monitor dual banks, so I will know what's going on...

This one:
Combiner 100 Sheet

It says to connect to 2 house banks consisting of max 1 battery per bank. Shouldn't it suffice for me anyway? I don't have anything that draws more than 100 Amps including the cranking engine.

I will take the route of building a dual bank system with traditional equipment (the link + temperature sensor + voltage adjustment thing etc).

[Bob666]

Hi everybody. Did the math. I will need 250 Ah a day, but will get less than 200 Ah if not running the engine. So I looked into shaft and towing generators, and wind generators as well.

Wind generators, they could shadow the panels on my aft arch, so pretty much ruled out.

Shaft generators:
Watts and Sea seems the way to go, unless it interfers with my Windpliot Pacific. BUT, it is prohibitely expensive!

Towing generators:
Very sceptical, people seem to have major problems with them:

https://www.youtube.com/watch?v=2AmcKJWfRr4

The rope is revolving. Asking for trouble? The Aquagen no good?
The Ampair. Any good? I could use it as a wind generator once arrived in the Carribbean:
http://www.cruisersforum.com/forums/...ors-26143.html

Cheers

[leftbrainstuff]

Originally Posted by Bob666

Hi!

I want to take the lazy approach. Not reengineer the whole electrical system. Last boat I did that and documented everything 1-1 <-> 2-1 etc in MS Visio. Took ages! And I believe simpler to actually write what to what in normal words, not numbers and having to look in another document what "1-2" means.

What if I stick to one battery bank. The extra bow battery could also be charged via the solar panels and alternator by putting a diode on the plus side towards it, and it can be used by the windlass AND be a reserve starting battery? Bad-ass plus and minus cables to it. Total: 5 batteries.

I will replace the parallell coupling cables of the 4 Gel batteries with fatter ones. I had 70 mm2 on previous boat. Perhaps overkill, what about 50 mm? Short cables, longest is 0,5 m as the fourth battery is a bit on the side from the other three. As I will replace the alternator from 50 A to 100 A I could check out the cable thickness there as well.

One thing I noticed is that the voltage drop from the electrical panel to the cockpit is substantial. Much lower in the plotter than at the batteries.

How do you go about designing the targa arch in the stern, the one I can put solar panels on top of? I have no experience of construction and strenght optimizations. Need to get in contact with somebody knowledgeable, how much can the solar panels protrude aft of the arch and how proper must they then be held up by welded arms attached somewhere on the aft side of the arch.

I have found at least two good welders of marine aluminium (need to keep weight down so rather than stainless steel). But they are not designers of the ultimate solar panel arch, I should find some kind of engineer for this job. Perhaps there exists designs already? If I knew the recommended angles, thicknesses and ratios (max and min lengths etc) I could modify to my needs.

Cheers

The increased wall thickness and larger diameter tubes needed to build a structural arch in Aluminum will likely be heavier than a stainless arch. This is the reason most boat arches, aircraft or race cars are not built from non ferrous materials like aluminum.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[skipmac]

HI Bob,

250 Ah/day. That's a lot of juice. Not that it is any of my business but very curious what you're using that draws that much. I haven't checked draw of the AP on my current boat but guess it has to be under 100 Ah/day. My fairly large fridge uses about 50 in hot weather, half that if it's cool. Cabin and running lights estimate 20-30 Ah max. Unless I run my old, high draw radar 24/7 I'm estimating 150-160 Ah/day.

As you're noticing, getting the extra power can be a problem. Hard to pack too many solar panels on a monohull. I have also heard a lot of problems with towed generators. Looked at the new water gens that raise lower and yes the cost was huge. I do have a wind gen still in the box and also wonder if it will shade the panels.

I do have a Honde EU2000 that I might run early in the morning to get a little bulk charge in before the solar panels kick in. Also considering a few small panels that I can move around to brackets on the side decks when weather is good and sun is right.

Another option is to run the engine but I hate that just for charging.

The last idea is one of the new fuel cell generators but they're also very expensive.

Let me know if you have any other ideas.