Three Bank Charger with Parallel Batteries

Willhound

This is more of a discussion for interest and curiosity rather than do it like this, or that.
I have a ProMariner ProSport 20 Plus three bank charger that I hooked up 3 years ago. I have a single starter battery on bank 1, and two house batteries on banks 2 and 3 with the house batteries wired parallel. I can clearly remember the instructions stating, and backed up by other sources, that the ProSport requires all three sets of leads to be hooked up for the charger to work properly even with a parallel connection. Apparently the circuitry in the charger prevents a short condition.
I've never questioned it, but it makes me wonder, does anybody know what magic happens in the charger to sense the parallel connection and how does that affect how the charger operates? Does it alternate between charging circuit 2 and 3? Does it allow current flow to both at a reduced rate? If one battery is weaker than the other does the charger prevent parasitic flow from one battery to  another when charging?
Curious minds want to know!

LaRea

So you have bank 2 wired to the first house battery, bank 3 to the second, and then a set of parallel cables from the first battery to the second?

JoeStang

I've got the exact same setup, and always wondered the same thing. All I know is that it works!

Willhound

LaRea said:

So you have bank 2 wired to the first house battery, bank 3 to the second, and then a set of parallel cables from the first battery to the second?

Yes. Sounds weird I know. First time I plugged it in I waited for the fireworks but it's been fine for 3 years and as I said the documentation and further search shows that's how they expect it to be hooked up. Since I'm going tomorrow to put the batteries in it piqued my curiosity since its in my thoughts.

BrianN15

I am looking to replace the original battery charger and isolator on my 2003 rinker fiesta vee 342.  I am going with the pronautic 1240p battery charger and the Promariner 02-70-03 battery isolator (2 in / 3 out 70 amp battery isolator to replace the original guest 2403) I also want to re-evaluate the boats wiring while making the changes.  After doing a decent amount of research this is what I have planned out in my head.  I was hoping somebody with a little more knowledge and experience could review and make any necessary comments or suggestions.  I currently have 1 starting marine battery and 4 deep cycle interstate srm 29 batteries.  Should I go to the 2 starters and 3 house (in parallel) as I have shown in the proposed wiring diagram? Any help would be much appreciated.

DanD2

IMO, You should definitely have 2 starting batteries just as you've drawn. Remember, one of those batteries also starts your generator. Kind of surprised you only have 1. As far as house, you would be much better off with 3 group 31 batteries instead of group 29's. I have 4 31's in mine and that provides lots of capacity when on the hook.

BrianN15

Thank you Dan! Sorry for the multiple posts I am still new to the forum and getting familiar with it all.  I appreciate the advice on battery quantities and types.  Does the wiring as shown look to be correct as well?

reneechris14

The drawing is correct definitely check or change all connections and the back off the battery switches. Two start batteries are good as far as the deep cell there are many choices. I have 2 group 31's flooded lead and it works for me I run genny 2 hours in the morning and 2 hours at night. Have stayed on the hook for a week with no trouble. If you go with different batterys I think they will all have to be the same type.

Stodge

The last time I replaced a battery charger (previous boat) the installation instructions said to go direct from charger to battery(bank) and I did without issue.  It called for #6 wire.  The only issue I can see with going to the isolator is if the gauge of the wire it runs to the battery is smaller than what you need for the amperage you want.  

skennelly

Replaced my charger and per the install directions went direct to the batteries.  I see no reason to go through the isolator.

Willhound

Same here. Alternator to isolator but charger direct to batteries. With the new smart chargers I think they need the direct connection to read the battery state correctly.

BrianN15

So your saying.....still keep the isolator using only the alternator posts and then leaving the other 3 output posts empty at this point?  If so then you would need to pair up new wires on those posts to take back to the starter batteries  wouldn't you?

Willhound

No. Run your two alternator feeds to the isolator and then from isolator to appropriate batteries. But run the leads from the charger direct to the batteries. You need one bank per battery so if 3 batteries a 3 bank charger, 4 batteries a 4 bank charger etc. The newer "smart" chargers read each individual battery for condition and charge rate and running through the isolator can mess up their readings.

BrianN15

Ok I think I have it. So in my situation (with the new 2 in 3 out isolator) I will run from engine alternator to the 2 alternator post on the isolator. Take 2 of the 3 out post and run those to the associated starting batteries.  This will leave the 3 post empty.  Then from the charger run 3 separate wires - 1 to each of the starter batteries & the 3rd would go to the 3 deep cycle house batteries that are connected in parallel .

BrianN15

Also what is the 70A not with the symbol on the rinker wiring diagrams referring to?  Is that a 70amp fuse? Do I need to add in line fuse to new wires run to batteries and such?

BrianN15

Type
and what is this helm power note?

Willhound

BrianN15 said:

Ok I think I have it. So in my situation (with the new 2 in 3 out isolator) I will run from engine alternator to the 2 alternator post on the isolator. Take 2 of the 3 out post and run those to the associated starting batteries.  This will leave the 3 post empty.  Then from the charger run 3 separate wires - 1 to each of the starter batteries & the 3rd would go to the 3 deep cycle house batteries that are connected in parallel .

Getting closer. Those house batteries in parallel would also have a feed from the isolator so that they charge while engine is running. Just run the charger hookuos direct to batteries, not through isolator.