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 ProISO (ProMariner) or ProSplit (Sterling Power) combines batteries based on
voltage in a
priority order or in
steps. It waits until each battery has come to 13.3V before bringing another bank on-line. That's it, so fancy I know.
With a near fully charged start battery achieving 13.3V 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."
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 how a start battery, at the point in its Coulombic curve where it's the most
inefficient, eg: 97-99.5% SoC, can become "
completely charged" in
"a few seconds" (quoting the Sterling manual) 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.. I guess we just supposed to assume Ohm's law & Coulombic efficiency do not apply to these products? "Completely charged" in just "a few seconds" at 13.3V......?
"
Wow, I must have that." says the often misinformed boating public. This type of marketing hype is how you can get mugged by the marketing department...
With these devices the start battery is always connected to the alternator meaning charging
begins with the start battery, all "few seconds" of it.. Please understand that 13.3V does not
charge a battery. It also means all charging amperage for the deeply discharged house bank must pass through the device where with a standard ACR you can feed all charge sources directly to the house bank and optimize charge performance.
It really means a
less than direct path to the bank that actually
needs charging the most. Because these devices sit smack dab in the alternator path, the closest we can sense voltage is at the unit itself. It can not account for any voltage drop between the unit and battery bank. This obviously = Non optimal for charging performance.
These devices also requires an "
ignition feed" to turn on. So, if you're planning on using it for
all your charge sources, such as wind, solar, hydro, shore charger etc., like owners do with Blue Sea Systems ACR's, other VSR/combiners, Echo Chargers, Digital Duo Chargers etc. you'll probably want to know the
quiescent draw of the unit when it is powered up 24/7, not just when "ignition activated".
Unfortunately neither Sterling nor 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:
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.
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 or what ever bank is on terminal #2. This would be no different than you removing 1.5Ah's from your start battery, 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.
The way it can completely recharge your start battery is no different than a Blue Sea Systems ACR or Yandina Combiner and it does this
in parallel with the other banks.
"Completely charged" 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". The Blue Sea Systems 7610-SI ACR combines at 13.0V and this happens much faster than 13.3V. That same Lifeline battery hits 13.0V in about 2 minutes.
Two 7610-SI ACR's would cost about the same as one ProISO, and they will work with all charging sources, not just the engines alternator.
This article goes into a lot of detail on how ACR's work:
Making Sense of Automatic Charging Relays
Two 7610-SI ACR's to charge the other banks is very simple and they are extremely reliable...
