Simple Battery Isolator Diagram ?

[Cheechako]

using a simple battery isolator... 2 batteries, one alternator. want to isolate one battery so it wont discharge in reserve for starting. I would like the option to be able to combine batteries in case of emergency so would like to use my existing battery selector (#1/both/#2) switch for that. I find diagrams on line but without the combining option.
Yeah, I can figure it out, but I imagine someone has this done.
and yes I know the pitfall is the alternator only senses one battery for charging.

[Beersmith]

read through this, excellent explanation by the magnificent Maine Sail:

1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com

[Cheechako]

Yeah, it is great...
I like the:
"We use our switch as a "USE SWITCH" in a SIMPLE ON/OFF scenario. That's it, ON & OFF, or more accurately #1 & OFF. We do not use it as a charge directing switch, or a start on BOTH or #2 then remember to move to #1 switch. It is basically an ON/OFF switch the way we use it. Simple, effective and you likely already have one.."
I also like the: " 2 banks , neither necessarily a start battery, only ever switch to one bank, other always reserve" which is how most my big boats were used, however it require I remember to switch to charge each battery bank.
However, it doesnt solve my problem of charging both banks. My battery switch is in the engine room and not that convenient to use if I'm trying to manually charge/discharge using the switch. It's a simple "day use" boat, but I dont want to get stuck with a dead starting battery... so would like to start off one battery and house off the other... both getting a charge. I'll figure it out.... just need the switch to transfer the "house" batt to "start" in an emergency...

[btrayfors]

Here you go. The ON-OFF battery switch shown on the engine circuit is a simple Blue Sea Systems #6006....robust, small, and inexpensive.

This gives you the option of combining if you want/need to, and simple automatic charging of both batteries. No need to switch anything.

Bill

[hellosailor]

Well, the cheap simple way is to install two separate simple "on/off" switches for the batteries. Turn on one or both, your choice. Turn #2 off, and it is isolated and reserved. That's cheap and simple.

Of you can use a West/Yandina battery combiner, little box you hook up, which only connects #2 when it sees full charging voltage on #1. Turn off the engine/charger, and #2 gets isolated. (There's a manual option to bypass the box and join the batteries, etc.)

That will cost more but ensures #2 is getting charged when there's power. There are similar "combiners", some solid state, etc., out there as well, and the EchoCharger doing the same thing.

But two simple switches, on/off battery switches, might be all you need.

[S/V Illusion]

Originally Posted by Cheechako

using a simple battery isolator... 2 batteries, one alternator. want to isolate one battery so it wont discharge in reserve for starting. I would like the option to be able to combine batteries in case of emergency so would like to use my existing battery selector (#1/both/#2) switch for that. I find diagrams on line but without the combining option.
Yeah, I can figure it out, but I imagine someone has this done.
and yes I know the pitfall is the alternator only senses one battery for charging.

Copying schematics already widely available by a simple Internet search is all you need.

[Maine Sail]

Originally Posted by Cheechako

using a simple battery isolator... 2 batteries, one alternator. want to isolate one battery so it wont discharge in reserve for starting. I would like the option to be able to combine batteries in case of emergency so would like to use my existing battery selector (#1/both/#2) switch for that. I find diagrams on line but without the combining option.
Yeah, I can figure it out, but I imagine someone has this done.
and yes I know the pitfall is the alternator only senses one battery for charging.

I would not suggest using a diode isolator. A voltage sensitive relay/automatic combining relay/Yandina Combiner) (VSR or ACR) or a battery to battery charger (B2B) such as an Echo Charger or Duo Charger would be fine for the second aux battery bank. The Echo Charger is the most simple to install

These are very easy to wire in... With an Echo Charger one wire goes to the house positive (the red one) one wire goes to Start/Reserve positive (the red with white stripe) and one wire to the house neg post or the loads side of a shunt. When installing an ACR/VSR or Echo charger you simply run the alt output to the house bank as well as the voltage sensing for the regulator. The VSR or Echo/B2B charger do the rest.... Now your 1/2/BOTH is a simple on/off use switch and charging both banks is done seamlessly and behind the scenes..

[DotDun]

I've had good luck with Victron's Cyrix, fairly cheap and easy. It has a 'emergency' mode.

Cyrix-i 120A/ 225A /425A - Victron Energy

[model 10]

Or you can operate the regular switch correctly. and not add anymore "stuff". I find the idea that there is always going to be human error in something this simple, unfounded. You develope procedures and stick to them.
And then have a back up plan

[hellosailor]

"I find the idea that there is always going to be human error in something this simple, unfounded."

Then perhaps you are not intimiately familiar with words like "Guest" or "Fatigued".

I know someplace where a truck backed into a loading dock, a simple task, and knocked out a water main. The plant manager was out, no one else remembered to tell him "there's pipes on that side, back into this side" and that's all it took, he knocked them out without ever seeing them.

When the pipes were being replaced, I asked the plant manager wasn't he going to at least put up a guard in front of them? He said no, they'd just make sure no one backed up on that side again.

If a simple mistake CAN be made, by accident, error, omission, fatigue, confusion, etc. and you can foresee that but take no steps to make it less likely...that's just plain foolishness.

In no one else will ever be on the boat, great. But at least a guard, a warning label plate...most of us would figure some type of precautions were in order, even if "idiot proofing" seemed uncalled for.

"Did I just do that?" has happened to most of us at least once in this life. Or in a recently passed one.

[goboatingnow]

Maine sail , why the dislike of using diode splitters to route charge current to the two batteries.


Dave

[Cheechako]

Originally Posted by hellosailor

Well, the cheap simple way is to install two separate simple "on/off" switches for the batteries. Turn on one or both, your choice. Turn #2 off, and it is isolated and reserved. That's cheap and simple.

Of you can use a West/Yandina battery combiner, little box you hook up, which only connects #2 when it sees full charging voltage on #1. Turn off the engine/charger, and #2 gets isolated. (There's a manual option to bypass the box and join the batteries, etc.)

That will cost more but ensures #2 is getting charged when there's power. There are similar "combiners", some solid state, etc., out there as well, and the EchoCharger doing the same thing.

But two simple switches, on/off battery switches, might be all you need.

Really no different than my battery selector switch. But as I said it's in the engine compartment, so if I want to charge while running I need to get in there and select "Both", then if I stop or anchor etc, I need to get in there and select one bank, then when I get back to the marina I need to get in there and possibly change again. It's a PITA. The reason I'm asking is because last time I used the boat a week ago I left the Batt selector on "both" and I left the VHF radio on. A week later both batteries were at 3 volts!
Glad that didnt happen at anchor. trying to make one battery not be drawn by anything but the starter and be charged whenever the other is.

[transmitterdan]

Originally Posted by goboatingnow

Maine sail , why the dislike of using diode splitters to route charge current to the two batteries.


Dave

I'm not Maine Sail and don't play him on TV but the short answer is that the diode lowers the charging voltage to the battery thus causing undercharging which reduces the life expectancy of most batteries. It is also wasteful of energy and creates a needless point of failure. I'm sure Maine will have even more reasons.

[goboatingnow]

Originally Posted by transmitterdan

I'm not Maine Sail and don't play him on TV but the short answer is that the diode lowers the charging voltage to the battery thus causing undercharging which reduces the life expectancy of most batteries. It is also wasteful of energy and creates a needless point of failure. I'm sure Maine will have even more reasons.

But of your battery sensing that's over cones the voltage drop , or use Schottky or even ideal MOSFET diode isolators , which essentially removes the voltage drop.

Very little energy is wasted in the voltage drop anyway.

I certainly prefer mosfet ideal diodes over mechanical relays.

Dave

[Cheechako]

Originally Posted by Guy

Or you can operate the regular switch correctly. and not add anymore "stuff". I find the idea that there is always going to be human error in something this simple, unfounded. You develope procedures and stick to them.
And then have a back up plan

The Japanese call "fool proofing" ..."Poka Yoke". It's one of many reasons they passed the USA in manufacturing for a couple decades.. until we copied them ....for a change! The second battery is the backup plan... but currently needs Poka Yoke! By the way... my tier two backup plan was one of those portable quick start things..... guess what?... when you hook one up to a battery at 3 volts the battery soaks it all up and you still cant start your engine!

"....When the pipes were being replaced, I asked the plant manager wasn't he going to at least put up a guard in front of them? He said no, they'd just make sure no one backed up on that side again..."
This guy worked for a company that refused to come into the new century..... just like GM, FORD and Chrysler until they "saw the light".