12v Battery Isolator Replacement

[HMT2]

I am putting some new batteries on my boat this week. My current system has worked well for years. We have had deep cycle flooded lead batteries last four years. So there is a part of me that is saying "if it ain't broke don't fix it". So let me explain. We are set up with two battery banks on two separate switches. One is a series 24 battery start battery, on its own switch (off/on). The second bank is house and two series 27 batteries in parallel. It is on a 1/2/both/off switch. (see picture called battery wiring) This works well I have no desire to change it. My dilemma is that for charging I have the standard Hitachi 35amp alternator, a 35 watt solar panel, and an ancient 30 amp three output "C-Charger" that I rarely use. I rarely use it because the solar panel generally keeps our batteries topped off. The Charger feeds into a West Marine 70 amp 3 bank battery isolator which feeds to the corresponding battery switches. Both the alternator and solar panel feed into the power source of the isolator. (see the diagram called charger diagram). There is also a photo of the charger and isolator.
So, here are my questions. 1) is there something that I can replace the old diode isolator with that will isolate the batteries and control the charge level of a new charger, the alternator, and solar panel. Would something like this work? http://www.sterling-power-usa.com/ProSplit-RZeroVoltDropMarineBatteryIsolator-12.aspx 2) if there is nothing that can do all three is there something that would control both the alternator and the solar panel? 3) can a charger sense voltage through an isolator?

 

[Head Sail]

If I understand correctly your isolator maybe old technology. Maybe put an ACR between the house and start banks. Your solar and alternator have regulators of their own.

 

[HMT2]

Yes the isolator is simply a diode isolator. Unless the alternator and solar panel are internally regulated there is no regulator on either of them.

 

[Head Sail]

Your alternator most likely has an internal regulator. A 35 watt solar panel may overcharge your batteries without a controller.

 

[Maine Sail]

1) is there something that I can replace the old diode isolator with that will isolate the batteries and control the charge level of a new charger, the alternator, and solar panel.

A Blue Sea ACR would be a great option with no 0.6V to 1V voltage drop like the isolator has. However, to work optimally, I would urge you to wire your house bank as one contiguously hard wire battery and then the ACR can sit between the two and charge start.

Your alternator, solar array and battery charger should all have their own voltage regulation. Your solar does not but it should. The old C-Charger is also not doing you any favors but if you don't use it but for only rarely then you can leave it. None of these devices are being done any favors by slapping a voltage dropping diode isolator into their path..

Would something like this work? http://www.sterling-power-usa.com/ProSplit-RZeroVoltDropMarineBatteryIsolator-12.aspx

I am a Sterling distributor but not a huge fan of that particular product, it serves no need, when a simple ACR/VSR/Combiner will suffice.

2) if there is nothing that can do all three is there something that would control both the alternator and the solar panel?

If the system was wired appropriately a single ACR would work, but you need to add a solar controller.

This is what you can do when you re-wire the switches. See 1/B/2/OFF Switches Thoughts & Musings

3) can a charger sense voltage through an isolator?

Yes, however it senses the voltage before any wiring voltage drop, on-top of the 0.6V to 1V drop associated with the diodes. This leads to chronic undercharging of the batteries and an inability to reconvert the lead sulfate associated with cycling. With a smart alternator regulator you can directly sense around the isolator but this gets expensive. Most chargers do not offer "remote sensing" (some very expensive inverter/chargers do) but isolators are/were not designed as a pass through for anything other than an alternator that boots when it spins regardless of battery voltage. The only reason your solar works is because it has no solar controller. Smart chargers, controllers and smart regulators are designed not to boot into an unsafe situation (think battery failure or open circuit) and diode isolators present 0V on the input stud, when no current is flowing, which triggers an "unsafe" mode to smart chargers, as it should.

Rx
Wire house as one hard wired parallel bank.
Feed all charge sources to house bank (including the alternator output)
Install an ACR/VSR/ Combiner or a DC to DC Battery to Battery charger between house and start banks.

What you will need:
Some wire
Terminals
Fuses
ACR
Solar controller

 

[Stu Jackson]

Maine Sail's response was very specific to your situation and answered all your issues.

If you want to do some more "basic" electrical boat system reading, including links to Maine Sail's excellent material, feel free to look around this topic:

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

There's a lot of material for background that explain the WHYs of his recommendations.

 

[HMT2]

Maine Sail,
Thank you for your very thorough and quick reply. Two follow up questions. 1) Which specific Sterling ACR would you recommend. 2) when I add the solar controller where do I add it? directly to the batteries (or house battery) or into the ACR?

Thank you again for all of your help with my specific concerns and for your help and wisdom on the forum!

 

[Maine Sail]

1) Which specific Sterling ACR would you recommend.

If you want a Sterling product the ProConnect VSR80 would suffice. In that class my personal preference however is the Blue Sea 7610SI ACR

2) when I add the solar controller where do I add it? directly to the batteries (or house battery) or into the ACR?

It sits between the PV array and the house battery. The ACR/VSR/Combiner would sit between the house & start banks.