The other I may run into, is the alternator on my 2GYM going to charge a lithium without blowing it up.

I've never had Relion, but I believe they are a quality manufacturer. I really don't know, however. As far as your alternator, you're going to want a way to adjust charge voltage. You are absolutely going to require a temperature regulator, or lithium will burn out an alternator. Many setups already have both and it's just a matter of programming correctly.

 

A DC to DC between the alternator and the lithium will protect your alternator. The DC to DC can be programmed to limit the charge current so the alternator is not stressed.

 

Relion is made by Navico group or a subsiderary. IE B&G, Simrad etal. That part tells me they should be ok. Unlike AGM or FLB types, I have not heard or seen anything about a given brand good or bad. Or the East Penn/Deka brands are probably the best of the basic brands, but if you spend more from Odysess, Mastervolt, Victron etc, you do get a longer lasting battery etc, but you spend 150% more as I did for the Northstart pre odysess version AGM I have. Yes it was worth the expenditure. I've gotten almost 6 years out of it vs 24-30 months with the lower cost items.
I'll have to look into the DC-DC or equal to see if I have one or not with in my boat. I'll swag but could be wrong, nothing has really changed in the 20 yrs I've owned my boat, she came pretty much stock etc when I got her. I did put a battery charger in it, when it had none. Recently put a newer one yet which can do FLB, AGM or Lithium vs the old one doing gel along with AGM, FLB. I'll need to figure out the alternator to battery part of the equation.

Marty

 

I have not heard or seen anything about a given brand good or bad.

There are many people out there testing lithium brands and models. The issue is staying current, because the offerings are changing so rapidly. The big reputable brands had the advantage of far superior Battery Management Systems (BMS), but some cheap offerings are closing in now. For those new to lithium, they must be managed by a computer circuit that keeps them from experiencing dangerous charge conditions. The lithium chemistry is hands down far more capable than lead acid, both in their total capacity per square inch of size and in the rate at which they can discharge and take recharge. However, early cheap models of lithium were using BMS that were limited far below the actual charge/discharge capacity of the cells.

Lots of DIY owners are willing to make mods to their electrical systems. I’ve always suspected that’s why DC electrical systems are the number one cause of fires on boats. It’s not particularly hard stuff to learn, but not knowing what one doesn’t know can lead to trouble. I encourage having a pro involved. Have them spec out changes to the systems or inspect it, if DIY. It’s super simple to create a circuit that allows the lights and radios to come on. It’s far more involved to insure safe wire sizes, fusing, charge and load capacities, temp and charge regulation, etc.

 

Now that I had a phun week of battling the BIG C. I can get outside of the home per say....
Went to the boat today, pulled out what I think is the DC to DC charger. Alternator positive goes to "A" and picture ending in 311 or middle post, then 1 goes to starting battery, 2 to the house battery. Only number or anything to say what it is in picture 312. The number is an 8503. Not seeing a brand label or spec etc.
Not sure how to test this thing, or equal to verify it is working. Nor can I see what the actual limits are per say in amps, volts or equal.

The only thing I see in the wiring I am not positive on, is both batteries have an individual wire from the alternator, and charger. Both batteries are hooked to the same pole on a basic Battery on-off switch like this one. SIERRA Battery Switch Off-On
My worry is that both batteries are being charge at the same time from the AC charger going in opposite directions. I may need to delete the starting battery. maybe that is what is not allowing the house battery to last as long as one should....

Marty

 

That looks more like a voltage regulator, or possibly an automatic charge switch, than a DC-DC charger.

 

That is a battery isolator, not a charger. Possibly an old Cole Hersee, as they were popular back then. It contains diodes that split the charge one-way each to separate outputs. When the alternator is not charging, it isolates the two outputs from each other.

Basically one-way valves for charging.

If your batteries are also connected direct to the alternator, then this isolator has been bypassed.

Mark