Multiple charge input to battery isolator

[ancor]

Hi all, I currently have one house and one starter battery with alternator charge plus mains charger when in port.
I'm looking to upgrade the system with a three battery isolator as I ultimately want to install another house (or dedicated autopilot/windlass) battery.
In addition, I would like to supplement the charge system with wind/solar down the track and was wondering how this would be wired? Can one put all the separate charging inputs into the "input" of these units, or do I require an additional device to keep the solar, wind and alternator charges separate?
Any info very much appreciated.

[David M]

Put the two or three or whatever the number of house batteries in parallel, with on-off switches on each in case one of them goes bad. Try and keep things simple for when the Sh8t hits the fan and you have to remember how it all works under stress. Your 12 volt charging devices can all be connected to the isolater input. I have done it for many years on a research vessel with no problems. They all have their different charging curves but that was never an issue. I have two alternators and one generator that charge all of the 12 volt batteries...house and starter.

[billknny]

Originally Posted by David M

Put the two or three or whatever the number of house batteries in parallel, with on-off switches on each in case one of them goes bad. Try and keep things simple for when the Sh8t hits the fan and you have to remember how it all works under stress. Your 12 volt charging devices can all be connected to the isolater input. I have done it for many years on a research vessel with no problems. They all have their different charging curves but that was never an issue. I have two alternators and one generator that charge all of the 12 volt batteries...house and starter.

I'll agree with everything DavidM says.

One exception. There is no good reason to have switches to isolate each battery "in case one of them goes bad." In the rare case a battery "goes bad" you just disconnect the cable from the terminal. No need for expensive switches. As DavidM says, "Keep it simple."

And for me, there is no remembering how it is all connected, no matter how simple. A proper schematic drawing that is accurate and fully representative of the current "as built" arrangement is critical.

[Stu Jackson]

Why an isolator?

[ancor]

Thanks for the feedback, the reason why I was looking to separate two house batteries was to have one with non-essentials, but high demand systems like windlass and autopilot and one for lesser demands, but essentials like nav lights and radio, which is currently all on one battery. At the moment there is only a battery switch with 1, 2, both and off, would prefer to have the charging automated, without having to remember to switch over etc.

[john61ct]

The big House bank is where all significant charge sources should be directly connected, ideally separate voltage sense, temperature sense wires, regulation optimized for that chemistry etc.

Then run appropriate combiners or VSR/ACRs to feed Starter(s) and other secondary/specialist/reserve banks.

The current level they pass through can usually be pretty small, say an Echo Charger only allows 15A.

But you can go all the way up to Blue Sea ML at 500A, enough to allow jumpstarting off House if needed.

An "isolator" traditionally implies an old-school diode based device, too much voltage drop, avoid those.

Keeping all your banks to chemistries that share a charge profile voltage range, means you do not need to spend the extra money on a DCDC charger.

Any large bank IMO should have an isolation switch, in an emergency or when doing wiring / maintenance, you don't want to have to fiddle around with tools.

[john61ct]

Having just one big House bank, as opposed to separate dedicated specialist ones, will give higher overall capacity from Peukert's Law.

Longer life from reducing average DoD, and

higher amps discharge rates with less voltage sag.

A second bank for redundancy is not a bad idea, but then treat it as a Reserve, not in normal daily use, just tested regularly.

[john61ct]

from Stu Jackson:

These oft-repeated threads about battery switching usually have one thing in common: the OP rarely understands how switching in electrical systems works and how many OEM boats came from the factory, and many still do.


Here's how and why, as well as just about every switching method used that actually works:



OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4....html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowner...d.php?t=137615

This is a newer primer for boat system wiring design with a thorough digram: Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/ind.../#post-1332240


STANDARD DISCLAIMER: combining a good bank and a dead one is just plain dumb, as is the BS DCP switch for sailboats.


AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
https://forums.sailboatowners.com/in...teries.133773/


********************

These links come from:

Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

[ancor]

Thanks John for the info. Will go through your links in due time. I'm not looking to up-speck to the latest, the boat is from the 80's. It is a simple setup that I'm looking to update with basic technologies and funds. No Lithium and staying with Gel as the starter battery is also basic, so similar charging profiles. As you mentioned, combining good and bad banks doesn't make sense, hence I was thinking of separating them vie an isolator as redundancy only. On my simple charger, the 'normal' setting allows for gel as well, but AGM etc. is another setting, so looking to keep it within the same category, if that makes sense!?

[CatNewBee]

Originally Posted by ancor

Thanks John for the info. Will go through your links in due time. I'm not looking to up-speck to the latest, the boat is from the 80's. It is a simple setup that I'm looking to update with basic technologies and funds. No Lithium and staying with Gel as the starter battery is also basic, so similar charging profiles. As you mentioned, combining good and bad banks doesn't make sense, hence I was thinking of separating them vie an isolator as redundancy only. On my simple charger, the 'normal' setting allows for gel as well, but AGM etc. is another setting, so looking to keep it within the same category, if that makes sense!?

What is your goal should be the first question.

What is your consumption?
What is your current set up?
Do you want more capacity?
Do you want more resilience by independent systems?
Do you want most longevity off your batteries?
Do you want an automatic system or manual control?

The simple part everybody shoud understand first is charge sources are same as loads, they can be connected in parallel to a battery, they have internal logic to regulate voltage and resulting current to stop charging when the battery is full, they are protected by dessign from over current and overheating. They have to be configured each to the battery chemistry they should charge.

Now to the isolators, how they work, why we need them and where are they necessary.

For resilience reasons one would like to have not all eggs in the same basket. If you have only one battery bank and one battery is damaged causing a cell short, or you leave a light on for a long time, all energy may be drained and the battery deep discharged. There is no way then to start the engine to recharge or navigate. Therefore it would be a good idea to have a separate independent battery only for the engine.

You could run a house and an engine circuit independent side by side, using the alternator alone for the start battery and the shore charger, wind generator and / or solar for the house. But you may want to also charge the house by the alternator and the start battery by the solar or shore power.

Now things get complicated. There are charger for shore power and solar, that have 2 or more independent outputs that allow charging of 2 or more independent batteries there are solutions with diodes to distribute charge currents and even voltage sensitive relays that connect batteries if there is an active charge source. You also could combine the batteries by a switch for charging and disconnect them when finished or simply use a switch to direct a charger temporary to a specific battery. You can even go further and use a b2b charger to discriminate or force a battery to be charged first, overcome battery demands on different chemistries and even create setups with different system voltages.

Usually boats and RVs have from the manufacturer separate circuits for the engine start battery and the house battery, so you can use what you have. An ACR (automatic charge relay, or voltage regulated relay or even a simple big NO relay connected to the D+ signal of the alternator or a diode /FET charge distributor) can be sufficient to separate the start battery from the board battery and use the alternator to charge both simultanously and automatically when the engine is running.

[Gtstricky]

I learned a lot from these videos. Maybe they will help.
https://www.youtube.com/playlist?lis...pSbzS42ggLptN4

[john61ct]

Originally Posted by ancor

staying with Gel as the starter battery is also basic, so similar charging profiles.
…
charger, the 'normal' setting allows for gel as well, but AGM etc. is another setting

GEL really needs precise regulation, both capping voltage much lower than AGM, but more critically strict on stopping charge on earlier endAmps, say 0.015C rather than 0.005C

Plus AGM really wants as high an amps rate in Bulk stage as possible, while GEL needs to be charged much more slowly.

So, if you really want to mix, I'd recommend your using a DCDC charger on the GEL bank, put the direct connection from high amp charge sources to the AGM.

Or, to get away with just a VSR/ACR stick to one or the other, and AGM is better for high C-rates.

But FLA remains the best value for money.

[john61ct]

Did you mean you're using GEL as Starter? If so, why?