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Old 20-07-2019, 20:23   #1
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Dual battery isolator vs Voltage Sensitive Relay

I have one of these redarc 24v battery isolator devices on the primary engine and the small diode on it has melted so the house bank that runs everything gets no charge from the engine alternator and I end up having to start the genset during night passages to keep everything happy. (Solar during day)



https://www.ebay.com.au/itm/REDARC-S...edirect=mobile

I have seen these Victron intelligent battery combiners that seem to do the same thing for half the dollars.
Am I understanding it right and could I use that instead of getting the new redarc device?



https://www.ebay.com.au/itm/VICTRON-...edirect=mobile

Thanks in advance
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Old 20-07-2019, 20:32   #2
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Re: Dual battery isolator vs Voltage Sensitive Relay

There are many dozens of such devices that all do more or less the same job.

Victron does in general make great kit, but the Cyrix line is not nearly as good as Blue Sea's what they call ACRs.

This one is truly bulletproof, will outlast the boat

https://www.bluesea.com/products/762..._-_12V_DC_500A

Besides ampacity look at features like self-jumpstarting, starter isolation, remote override.

If you're open to a bit of redesign, consider putting all your charge sources direct to House.

In which case even a little Echo Charger or Yandina combiner will handle the little bit of current required to keep Starter topped up.
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Old 20-07-2019, 21:05   #3
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Re: Dual battery isolator vs Voltage Sensitive Relay

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Originally Posted by john61ct View Post
There are many dozens of such devices that all do more or less the same job.

Victron does in general make great kit, but the Cyrix line is not nearly as good as Blue Sea's what they call ACRs.

This one is truly bulletproof, will outlast the boat

https://www.bluesea.com/products/762..._-_12V_DC_500A

Besides ampacity look at features like self-jumpstarting, starter isolation, remote override.
Thanks for the reply but they are 6x the price of the victron here in Oz

https://www.springers.com.au/shop/pr...gory=48&page=3

And why do I need a 500 amp device when the alternator produces nothing like that?

Quote:
. If you're open to a bit of redesign, consider putting all your charge sources direct to House.

In which case even a little Echo Charger or Yandina combiner will handle the little bit of current required to keep Starter topped up.
A bit out of my league I would suggest and not wanting to add in the additional cost of electricians and marina berths into the equation if not needed.

If the Cyrix will do the job of what I had, and is pretty much undo wires and reconnect that'll do me.
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Old 20-07-2019, 21:20   #4
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Re: Dual battery isolator vs Voltage Sensitive Relay

Yes that is the Rolls Royce model.

Blue Sea has many other ACRs that are lower priced.

Of course in the end do what you like.
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Old 21-07-2019, 09:36   #5
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Re: Dual battery isolator vs Voltage Sensitive Relay

If you want a cyrix-ct 120A. I have one left. Due to a complete redesign. I reduced from 3 House banks to one.


But I am located in croatia and it'll took a long time to get it to australia.
Price? make me an offer.
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Old 21-07-2019, 09:48   #6
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Re: Dual battery isolator vs Voltage Sensitive Relay

In my application I found the auto-sensing of the BlueSea ACR to switch on and off when then engine was not running, due to the resting voltage of the engine battery bank. I changed to a plain BlueSea relay controlled by the engine's alternator charging signal.



That being said, I have both an BlueSea ML-ACR (7620) and a Victron Cyrix-ct (230A) up for sale. The Victron unit is unused. I am located in Canada.





Allan.
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Old 21-07-2019, 09:58   #7
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Re: Dual battery isolator vs Voltage Sensitive Relay

I have a small Blue Sea ACR to keep the reserve/start battery topped off without having to remember to flip any switches. Alternator and solar go to the house battery. Don't understand not having the alternator going to your house bank.
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Old 21-07-2019, 10:55   #8
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Re: Dual battery isolator vs Voltage Sensitive Relay

Intervolt EBI Pro has adjustable setpoints.

Horrible attitude but apparently a good product, and Australian
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Old 21-07-2019, 12:22   #9
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Re: Dual battery isolator vs Voltage Sensitive Relay

The inherent disadvantage of a diode based battery idolator is the fixed voltage drop of a diode which can be as high as .7 V so they can actually produce alot of heat due to the power loss. There is a power loss from the coil of a relay but it is nothing as compared to the diode loss. Highly conductive contacts of a mechanical power switch basically have no power loss.
There is no free lunch in physics.
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Old 21-07-2019, 12:30   #10
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Re: Dual battery isolator vs Voltage Sensitive Relay

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The inherent disadvantage of a diode based battery idolator is the fixed voltage drop of a diode which can be as high as .7 V so they can actually produce alot of heat due to the power loss. There is a power loss from the coil of a relay but it is nothing as compared to the diode loss. Highly conductive contacts of a mechanical power switch basically have no power loss.
There is no free lunch in physics.
True of the old ones- lots of losses.

The new ones like the Victron ArgoFETs are orders of magnitudes better.

They can also prevent any other potential large current flow issues between banks issues that could occur under certain conditions.
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Old 21-07-2019, 12:37   #11
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Re: Dual battery isolator vs Voltage Sensitive Relay

The alternative at much lower cost is to use a standard heavy duty automotive relay. Wire in an on/off switch to the coil to manually turn it on. And, if your alternator setup allows, also include a feed from the alternator that is only powered when the alternator is running to give automatic charging. I like the manual option as it allows charging to be turned off if not required but it does mean you need to remember to turn it on!!!
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Old 21-07-2019, 13:29   #12
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Re: Dual battery isolator vs Voltage Sensitive Relay

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Intervolt EBI Pro has adjustable setpoints.
Never head of these folks. Thx.

Photo of my current setup (yes, the wire against the terminal has been adjusted since this photo was taken). BlueSea remote battery switch, driven by the engine wire that turns off the alternator idiot light.


Allan.
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Old 21-07-2019, 14:11   #13
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Re: Dual battery isolator vs Voltage Sensitive Relay

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I have a small Blue Sea ACR to keep the reserve/start battery topped off without having to remember to flip any switches. Alternator and solar go to the house battery. Don't understand not having the alternator going to your house bank.
I never did the wiring
We bought the boat, all wiring done, all we did was replace dead inverter, dead house batteries and add solar.

The problem I see doing house first and then start is the anchor windlass runs off of the starts.(n150 x 2 @ 24v)
Also the starts would never get done as the house bank is continually being drained.so the device would never switch over to charge the starts.

We do have a 4amp trickle coming from the victron inverter charger to the starts but doubt if that'd be enough to keep up with start loads and anchor windlass usage.
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Old 21-07-2019, 14:20   #14
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Re: Dual battery isolator vs Voltage Sensitive Relay

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Originally Posted by Simi 60 View Post


1..I never did the wiring
We bought the boat, all wiring done, all we did was replace dead inverter, dead house batteries and add solar.

2..The problem I see doing house first and then start is the anchor windlass runs off of the starts.(n150 x2 @ 24v)


3..Also the starts would never get done as the house bank is continually being drained.so the device would never switch over to charge the starts.

4. We do have a 4amp trickle coming from the victron inverter charger to the starts but doubt if that'd be enough to keep up with start loads and anchor windlass usage.

1..Understood.
2..How difficult would it be to change the windlass to the house bank?
3..In most cases with equipment that automatically parallels banks WHEN CHARGING SOURCES ARE PRESENT the higher charging voltage closes the relays or passes through the diodes and provide charging to both. The charging voltage is always higher than the resting voltage of the bank(s). That's simply how they work.
4..Is that only when you're on shorepower? If so, then it should be different when you're providing charging via your alternator. You're not plugged in when you're recovering your anchor, are you?
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Old 21-07-2019, 14:31   #15
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Re: Dual battery isolator vs Voltage Sensitive Relay

I agree with Stu above. Start battery should be dedicated to starting only.

Windlass and everything else should be off of the house bank.

All charge sources should go to the house bank. This makes the most sense as the house is always most in need of charging. Also it prevents chattering as the ACR closes and opens repeatedly when charging goes to the start battery. Blue Seas agrees.

The ACR combines when the house bank reaches 13 volts, allowing the start battery to charge. The start battery will get charged.
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