Lithium on the Cheap

[avanti]

Originally Posted by booster

Trombetta part# 936-1215-011-21 from another forum

300 amps continuous rating-100% duty rating golf cart relay.

Not a separator or isolator

I thought such a relay WAS an "isolator". What else does that term imply? I didn't think it mattered that it was controlled by the alternator output.

[wincrasher]

I'm going to proceed with my little project.

The Smart Battery people are hand carrying a battery to my home on Monday. They have a distribution warehouse up the road in Fort Mill, SC.

The battery charger I ordered last week, so it will also be here on Monday too. I'm sticking with 45 amps as that is supported by the existing wiring. Yes, it's not quick charging. An hour engine run time or genset run time is quick enough.

So what I'm doing here is an extremely modest upgrade, with an extremely modest price tag - around $1500. My first concern was will it be safe. I'm pretty convinced that it is. Second is it reversible. That I have covered with it being plug and play using all the existing wiring.

For now, I'm not going to put in any thermal protection. I don't plan on using my van in freezing weather, and it's stored in a heated garage. If I do plan a trip in sub-freezing temps, it's not a big deal to install a heating pad. With the casing on this battery though, it may be enough to just heat it up by running a 12v appliance to heat up the battery. I think with it's position below the van, the cooling on it will be fine. I will install a sensor to see what temps I have inside the casing.

I'm only going with one, 100 ah battery. That is fully 2x the capacity of the stock battery and a bit more than the useable capacity of the 2 Group 31 batteries I have installed. I probably could squeeze in two, but I don't think I need that much capacity, and I don't want to push my luck with my existing wiring.

At this time, I'm not doing any inverter. I really don't need one. The water heater and the microwave are my only AC only appliances. So it's genset run time for those and the AC.

I also don't need any solar panels. I have the portable for those rare occasions I might want it. I just don't see sitting in one spot long enough to really get any benefit.

What I haven't figured out is how I'm going to determine the present capacity of the battery. They tell me it holds 12.8 volts all the way down to almost zero amps left. It may be useless information to know, as the total capacity is 4 or 5 days of my total daily useage in most cases. But I'd like to know the health of the battery in a year's time. I do have one of these that might do it: http://www.amazon.com/gp/product/B00...rch_detailpage

[booster]

Originally Posted by avanti

I thought such a relay WAS an "isolator". What else does that term imply? I didn't think it mattered that it was controlled by the alternator output.

In strickly engineering terms, it could, and probably would, be called an isolation relay. They need to be externally controlled.

In RVspeak, the term isolator is used to describe the diode type units that allow charge level voltage pass through from the engine to the coach, but not the other way around. They drop voltage about .7 volts.

Also in RVspeak, a separator would be like two way isolator that works with switching, rather than diodes, based on charge voltage on either side of it. They will charge all the batteries from charge voltage either on the engine or coach. They have no voltage drop.

[booster]

Originally Posted by wincrasher

What I haven't figured out is how I'm going to determine the present capacity of the battery. They tell me it holds 12.8 volts all the way down to almost zero amps left. It may be useless information to know, as the total capacity is 4 or 5 days of my total daily useage in most cases. But I'd like to know the health of the battery in a year's time. I do have one of these that might do it: http://www.amazon.com/gp/product/B00...rch_detailpage

I think all you would need to do would be to put in a Trimetric meter and you will now nearly exactly what your state of charge is.

[Boxster1971]

Originally Posted by booster

In strickly engineering terms, it could, and probably would, be called an isolation relay. They need to be externally controlled.

In RVspeak, the term isolator is used to describe the diode type units that allow charge level voltage pass through from the engine to the coach, but not the other way around. They drop voltage about .7 volts.

Also in RVspeak, a separator would be like two way isolator that works with switching, rather than diodes, based on charge voltage on either side of it. They will charge all the batteries from charge voltage either on the engine or coach. They have no voltage drop.

It depends on who is doing the speaking. My battery separator is called a Battery Isolation Manager (BIM) by the manufacturer, Precision Circuits Inc. It is a large relay controlled by an electronic module.

[avanti]

I agree with Boxster. Unlike some other RV-speak, I do not believe that it is at all uncommon to call a dumb relay a "battery isolator" or an "isolation relay" in an RV context. (not being argumentative--just trying to facilitate communication).

[booster]

I agree that they can and are called a lot of things, but in the RV discussions, it is almost always the way I initially described it, from what I have seen. I think the isolator thing was kind of universal, and it did what described, isolate the the starting battery to protect it from discharge. The two way units don't isolate anything, they just separate them from connection going both ways (I know Surepower calls a one way relay type a separator? I would call it a relay isolator because that is what it does).

The manufacturers call them whatever they want, but maybe Blue Sea has the best idea in calling them charge relays if they are remote controlled, automatic charge relays if the close do to charging voltage, charger relays with starter interrupt, etc. Pretty clear which is which.

It probably all gets down to that most manufacturers chose the Surepower, and they called it a separator, so the term stuck to differentiate it from the diode units. No good reason for it.

[markopolo]

What are the advantages & disadvantages of using the Trombetta part?

No voltage drop?
Uses current to keep the banks connected?

It looks as though Wincrasher could just leave that part in place.

[avanti]

My 2014 Great West Vans Legend came with a simple relay setup, controlled by the "engine running" signal from the Sprinter. I added a Trik-L-Start to support chassis battery maintenance and a "Boost" switch on the dash. IMO this very simple setup is pretty close to optimal.
(Not that anybody asked)

[wincrasher]

My van does have a "boost" switch, which I assumed controlled a combiner of some sort.