For the average boat owner the marketing spins and wives tales usually force one to use some common sense & critical thinking...
All of the devices below are in what I call "Charge Management Devices" or CMD's. I lump them into four categories.
Diode or FET Isolating CMD's: These devices split charging and isolate banks for back drain via FET's or Diodes. They induce voltage drop and can not be used with most smart chargers or solar controllers etc. that require a 12V signal to boot up. In today's day and age they are akin to dinosaur saddles or buggy whips and have few justifiable uses on boats. They are usually easily identifiable with their input & output studs & aluminum heat-sinking fins. These cooling fins are there for a reason. The reason is that voltage drop creates waste heat and that waste heat needs to be dissipated.
Paralleling CMD's: ACR's, Combiners, VSR's, ProSplit R's, CVSR's etc. etc.
These devices simply parallel banks when charging voltage is present and isolate/unparallel them when not. They combine/close on voltage rise and isolate/open on voltage fall. This is essentially a fully automatic BOTH switch.
Voltage Following Buck Type CMD's: Echo Charger & Duo Charger
These devices follow the voltage of the house bank and can only impose voltage and current limits on the output side. They do not independently float or feed a different charge profile to a start battery as many incorrectly assume they do.
Independent DC to DC Buck/Boost CMD's: Sterling Power DC to DC Battery to Battery Chargers or B2B's
These devices are essentially a full featured, fully independent 12V DC to 12V DC battery charger that is powered by 12V DC on the input side as opposed to 120V. The newest Sterling B2B chargers are capable of 30A - 60A and are fully programmable including absorption time parameters. They are equivalent to the smartest battery chargers only they are powered by a battery bank not 120V..
What about the ProIso?
IMHO the ProIso is chock full of marketing gimmickery and is really the work of Sterling. PM wound up with it through a joint venture with Sterling. I would suggest avoiding it unless you like parting with your money too easily. There is no need for any of the marketing driven features in that unit other than to add complexity that is not really necessary, and to scare and mislead the general boating public about what it is they think they may need.
Don't get me wrong C. Sterling can and does build some great stuff but the ProSplit-R/ProIso are not, IMHO, one of them. As a dealer I am not a huge fan of this product because I don't see any need for it nor for the complexity of it. There are numerous features that make it "less than ideal" compared to other products.
This is especially true when comparing it to a much simpler product, with a virtually impeccable reliability rating, such as a Blue Sea ACR or ML-ACR. Charlie is well known for praying on the fears of consumers & then developing a product that sells to those fears. Some of his products are great, such as his DC-DC battery to battery chargers, and some are not so "wow" like the ProSplit etc..
One thing Charlie mentions in his manuals, that PM often fails to counsel their customers on, is that any un-used output needs be tied to another used output. If this is not done the unit won't work.
"Please note in the event of any outputs on the ProSplit not being used then they must be linked to one which is, i.e. all outputs must be used, one must not be left unconnected."
What is the ProIso or ProSplit?
This product is nothing more than a stepped voltage sensitive combining relay. For added complexity and additional failure points the units often have multiple relays in one box and it's installed in-between the alternator and the bank not between batteries like other charge management devices... The PI or PS combines batteries based on voltage in a priority order or steps. It waits until each battery has come to 13.3V before bringing another bank on-line. That's it, not so "complex" once you break it down and no smoke no mirrors other than in the confusing marketing lingo.
With a near fully charged start battery this can literally be just "a few seconds". In other words your 99% SOC start battery exceeds 13.3V in a matter of seconds once the charge source fires up, because of its SOC. Once start is at 13.3V the device brings the house bank on-line. When the house bank hits 13.3V it then brings a third battery on-line, if you have a three bank model.
All sorts of wild marketing claims are made such as; "Priority setting for the START battery to ensure a completely charged start battery[/b]."
I can see the product development meeting now;
"Let's pray on the fears of boaters who worry they may not be able to start their boats engine.". "Yeah, yeah boss we'll call it "priority start" and throw so much confusing lingo at them they'll think they are getting something they're not."
If someone can explain to me how a start battery, at the point in its Coulombic curve where it is the most inefficient, eg: 97-99.5% SOC, can become "completely charged" in "a few seconds" (quoting Sterling manual same product as the ProIso) at just 13.3V you've discovered best battery storage medium in existence....
That last 2% of the SOC curve is the absolute longest & excruciatingly slow part of the charging curve that exists.. Are we just to assume Ohm's law & Coulombic efficiency do not apply to these products? "Completely charged" in just "a few seconds" at 13.3V. This is why I said "critical thinking" is key when looking at these products..
"Wow, I must have that." says the general boating public. This is how you are being mugged by marketing...
With these devices the start battery is always connected to the alt meaning charging begins with the start battery, all "few seconds" of it.. Oh and please remember that 13.3V does NOT charge a battery. This also means a less than direct path to the bank that actually needs charging, the house bank. Because this device sits smack dab in the alternator path, the closest we can sense voltage is at the unit itself. There for it can not account for any voltage drop between the unit and battery bank. This = Non optimal.
The unit also requires an "ignition feed" to turn it on. So, if you're planning on using it for all your charge sources, such as wind, solar, hydro, shore charger etc., like many do with ACR's, combiners, Echo's, Duo's etc. you'll probably want to know what the quiescent draw of the unit is when powered up 24/7, not just when "ignition activated"... Oh wait, neither Sterling or ProMariner tell you this critical specification in the manual.....??? All that marketing and they just happened to leave that piece of critical information out....??
How it "completely charges" your start battery (wink):
When the start bank hits 13.3V it then combines/parallels with bank #2. When the system voltage (combined voltage of bank 1 & 2) is again at 13.3V it then parallels in bank #3 and so on. That's it!!
It does not prioritize and "completely charge" a start battery first, as they like to suggest through marketing, it simply brings it to 13.3V before paralleling it with the house bank. This would be no different than you removing 1.5Ah's from your start battery, at home, then turning on the charger until the battery voltage hit 13.3V then turning it off. You can't replace those 1.5Ah in a "few seconds" so suggesting the units "completely charges" your start battery based on "priority" is misleading at best.
They way it can completely recharge your start battery is no different than an ACR or Yandina Combiner, and that is in parallel with other banks while charging.... However PM and Sterling lead you to believe this "priority step" is completely charging your start battery first and this is not at all true. With most start batteries this voltage rise happens in "a few seconds" and even with the minimal consumption from starting, the battery Ah capacity has not really been replaced before it has been placed in parallel with the house bank. Misleading? Absolutely.. The device simply begins with the start battery then brings the others in parallel as voltage attains the 13.3V level.
Even for a 50% discharged house bank attaining 13.3V does not take a long time with a properly sized charging system. For example even a high acceptance rate Lifeline AGM discharged to 50% SOC (in lab conditions for accurate measurements) then recharged at .2C, this is 20% of Ah capacity or 20A on a 100Ah battery, will attain 13.3V in about 20 minutes. This is why, for a start battery North of 98% SOC, this voltage rise takes "a few seconds".
Options:
House to Bow Charging (assuming all charge sources lead to house):
If you already have large wire to the bow bank, such as 1/0 or larger, then an ML-ACR, with the Contura switch, is an ideal choice between bow and house. The ML-ACR allows you to "lock it closed" when using the windlass or thruster thus utilizing alternator power and your massive house bank to keep the voltage at the thruster end as high as possible. The higehr the voltage at the thruster end the better it performs. When you are done with the thruster simply set it back to ACR mode. With high draw thrusters and windlasses you really can't beat a parallel connection to the house bank. Because the ML-ACR can be "latched", and is capable of handling thruster currents @ up to 500A continuous, it is really the only voltage sensing relay/combiner that is well served for this type of installation, if you have the positive and negative wire to support it..
If you do not have big wire between house & bow the best option will be something like a Sterling 12V to 12V battery to battery charger such as the Sterling Power BB1230 or BB1260 one is 12V X 30A and the other is 12V X 60A. They are in high demand right now and stock is slim in the US but they are great B2B chargers.
The Sterling battery to battery chargers are excellent and are the only true "independent" buck or boost 12V to 12V chargers out there. For example a B2B can take a GEL voltage of 14.1V and boost it to a TPPL AGM voltage in the bow of 14.7V and give a fully independent charge profile to the TPPL AGM bank..
House to Start Charging:
Here a standard 7610 SI ACR would be fine as would an Echo Charger or Duo charger.. Both the Echo & Duo are "buck" (drop voltage) voltage following CMD's and they can not float or boost voltage to another bank if it's a different chemistry requiring that.
Due to amperage of the thruster a one size solution is not in the cards. The most amperage you can share between the house bank and bow bank will yield the best performance and this is an ML-ACR..
