My personal take on the starter battery, is that it needs No solar input. The goal of having a secondary battery system is so that the engine starting battery is never touched by house/ Aux draws/load, So one should not require sharing solar current with the starter battery.
The Surepower 1314a is a good single sense/uni directional smart solenoid meaning it will combine the batteries only after the engine battery is above 13.2v. Solar applied to just the house battery will not cause this solenoid to combine the batteries.
The surepower 1315 is a dual sense bi directional smart solenoid which will combine both batteries when either battery is up above 13.2v.
http://www.allbatterysalesandservice.com/browse.cfm/2,1140.html
The 200 amp versions are double the price of the 100 amp versions though.
Some might think the dual sense/ bi directional solenoid is a no brainer as it is the same price, but with Solar, you do not want to share the solar wattage between Starter and house, and you do not want a portion of the solar wattage to be used by the electromagnet just to do so. I say you do not want to share the current between both batteries, as most solar systems are underpowered to properly recharge just the one AUX battery. Even if the engine battery is fully charged and most current will be taken by the depleted house/Aux battery, a portion of the solar current is going to go into the engine battery just to hold it at 14.xx volts, and a portion is going to go to holding the solenoid contacts together. Current that would be better used to charge only the AUX/house battery which needs it the most.
You want all the solar wattage going into the house battery, and if you do want to share some solar wattage with the engine battery, many ways to do so exist. One could just put a temporary Jumper between the big terminals on the solenoid, or jumper cables between the batteries themselves. Having a dual sense solenoid just for the rare times when this scenario is needed/wanted, is unwise, in my opinion.
I am not familiar with the Yandina combiner/ separator function.
I personally do not like these smart solenoids, or ACR's. here is why.
First, the engine battery is in a properly wired/ designed dual battery system should not be discharged at all. Start the engine, and the alternator will nearly instantly have the engine battery over 13.2v or 13.8v and the batteries will be combined. If the house battery is super low it might drag the combined voltage down below the 12.8v threshold and the solenoid separates the batteries, and then, freed from the depleted house battery load the voltage quickly rises back up above 13.2, combining the batteries again. I think there is some sort of delay programmed into these smart solenoids to prevent this possible rapid cycling on and off, but perhaps not.
Many years ago the Surefire 1314 was responsible for a few vehicle fires and they had a recall and a large batch of serial numbers. Beware of used units being sold.
Now, the unidirectional/ single sense smart solenoid keeps the batteries paralleled until the engine battery falls below 12.8v or 13.2v . Due to surface charge, this might take hours before the voltage falls below the 12.8v threshold. This whole time the smart solenoid will have the batteries combined and using 0.6 to 1 amp to do so. If this 1 amp is for an hour, well that is likely more than my 12v compressor fridge uses in an hour.
If the engine is shut off during the day, while the solar is still going, then this unidirectional/ single sense solenoid will still keep both batteries combined until sometime near or even well after sun down. That solar current would have been better off only feeding the single house battery which was cycled and needs all the recharging current the solar can make.
Now if the engine is shut off, the solar keeps the voltage above 12.8v on both batteries, the smart solenoid keeps the batteries in parallel, and say the engine is started again, both batteries will be feeding the starter motor with 100+ amps each to do so. Any delicate electronics hooked to the house battery are not separated from possible surges/spikes that the starter motor can induce when the power is removed from it. Also the starter current flowing through the solenoid will wear the contacts faster. The only positive is that the Starter battery has two batteries feeding it and it turns much faster and starts the engine faster, but in reality holding the key to start for .5 seconds vs 1 second, means little.
I enjoy having the merest blip of the starter motor start the engine with my 930 CCA AGM, but the larger, higher capacity Flooded deep cycle battery @~ 620CCA also has no issues cranking the motor on its own, it just does so slower and I have to hold the key a bit longer. Big whoop. But I do enjoy the AGM's ability in this regard, even though it means nothing, or very little, in the end. It's a personal problem
In my opinion, a high quality Dumb CD solenoid, activated by the blower motor circuit( which is usually inactive during engine cranking/starting), is superior to a smart solenoid in application and function.
One can also wire in a simple lighted toggle switch on the blower motor solenoid activation circuit. Flip a switch to activate the solenoid after the engine is already running. Forget to unflip the switch, shut off the engine and the batteries still separate and the engine battery will still be fully charged, ready to go the next engine start.
Wiring the solenoid activation circuit appears to be a main reason why people choose instead these smart solenoids or Automatic charge relays over the dumb solenoid. Pulling 12v off the Blower motor circuit is not difficult at all. One can just shove the wire into the fuse for the blower motor, and putting a lighted toggle switch inline on this wire is a cakewalk too.
A depleted house battery can ask for huge amperages from the alternator, especially if the cabling between alternator/solenoid and house battery is thick and short, as it should be for maximizing efficacy. Each 25 charging amps takes one engine HP. I feel an overnight cold motor is better off warming up a bit without the alternator asking for 3 HP just to feed the battery. Some might say it is producing huge amounts to replenish the starting battery anyway. Perhaps if the vehicle takes lots of time to start this is true. On my '89 Van, which is fuel injected and starts easily and quickly the amps just to feed the fully charged starting battery starts at about 32amps and within 15 seconds is about 12 amps and will taper to the low single digits within a minute.
I usually allow at least 30 seconds to pass before turning my battery switch and allowing alternator amps into the depleted house battery but will go longer in colder conditions or if the house battery is really super depleted or if it is damp/ raining. If the house battery is not very depleted or there is to be a lot of sun, often I choose not to allow the alternator to feed it any current.
Having the toggle switch activating the blower motor circuit and thus the solenoid allows the driver the option to allow the engine to warm up a bit before it is asked to feed a hungry house battery with 25 to 75 amps, 1 to 3 HP.
When that toggle switch is thrown, when the house battery is depleted, you will hear the engine note change, perhaps not on a Diesel, but it is very noticeable on my 5.2 liter V8. When I turn my manual switch and the amps the alternator makes goes from about 18 to 70 amps, it is very noticeable in the tone of the engine. If it is wet out my alternator belt might start slipping and squealing at higher rpms(900 and above) as the battery is sucking up 75+ amps. The toggle switch would be nice. My manual switch however cannot be reached from the driver's seat. So If I accelerate and the alternator belt starts squealing, I basically have to get off the gas to stop the squealing. The dash mounted toggle would be nice. But I have no solenoid and am not moving my switches, so will just deal with it as is.
I like my 3 manual switches to control current flow from to and fro here and there, but In another Van, I would choose the Dumb CD solenoid on the blower motor circuit with lighted toggle switch over any other automatic isolator/ combiner system, even the respectable Blue seas ACR.
Lots of opinion in this post. There are many ways to do this battery isolation combination, and I'm not saying any one way is best for every/ All system(s) vehicles.
My goal is to inform to allow others to make the best choice for themselves.