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Topic: Engine Start Battery Options (Read 3651 times) previous topic - next topic

Re: Engine Start Battery Options

Reply #43 –
Pierce's EBay Victron ArgoFET isolator comes from Bay Marine Supply, same price as the link I provided that actually goes to Bay Marine.  Alan's prices on Victron equipment are most often very competitive.  if you find it for less ask and he may discount a bit.  and if you have questions he is there for support.  These days that is worth more than saving a couple of bucks.
Victron Argofet Battery Isolator

Re: Engine Start Battery Options

Reply #44 –
My method of just one battery bank with 1400 watts of solar seems to be as "KISS" as is possible.
It does require being aware of the charge state of the batteries, especially when an engine start is required before the sun is shining.
I have used this system for 10 years but did have to boost with my car battery on two occasions.
No isolator required.
I also moved all the wires from behind the rear driver side wheels to under the bed and connected the alternator sense wire to a common "+" post rather than the OEM A/C relay. 

Re: Engine Start Battery Options

Reply #45 –
Wyatt,

I have no problem with your "one battery" solution.  BUT (read that a BIG BUT) I suspect less than 5% of RV'ers are "electron savvy" enough to do it correctly (proper discharge/recharge cycle).

Having spend many, many months on a sailboat (ya, no shore power) there ARE those of us who know how to manage 12 VDC.  However, I would not recommend that for very many folks.

OH, and Purket would be proud of you. 

Re: Engine Start Battery Options

Reply #46 –
Quote from: P. Wyatt Sabourin –
I also...connected the alternator sense wire to a common "+" post rather than the OEM A/C relay.
I find Wyatt's comment about the sense wire very pertinent to this whole thread.  With his setup of a single (big) battery bank, and no isolator, one might think that the alternator sense wire is no longer required.  I took this idea one step further, wondering if a "ONE WIRE" alternator could be used to replace the DUVAC unit.  At least that's what I was thinking...but I was wrong.

In a perfect world, where 100% of the output from the alternator flows unimpeded to the end of every circuit on the coach, you might do OK without a sense wire.  However, it is not a perfect world, and there is always something trying to "resist" the flow of electricity.  Might be dirty terminals, or corroded connectors, or under sized cables, or poorly designed overly long wiring runs.  No matter what the reason, it is very likely that what your alternator puts out is NOT what your batteries (all of them) will see.  Hence the need for a sense wire.

I always thought that the closer you can connect the sense wire to the actual battery post, the better.  You DO want to induce the alternator to do whatever is necessary, so that the full optimum charging voltage is delivered to where it is required: at the POS battery post.  However, the article below makes a case for connecting the sense wire at some central wiring junction, rather than directly to the batteries.  Sounds more like what Wyatt did.  I'm not smart enough to know if the article's logic is applicable to our coaches, but it seems to make "sense" (Ha, Ha) to me.

Interesting article (written by Hot Rodders) that got my mind right on this subject:

Catalog

Re: Engine Start Battery Options

Reply #47 –
I did the same on the sailboat.  Wired the sense wire (external smart regulator) to the battery itself. That way the small loss in connections and wire are "made up for" and the batteries see the full voltage they are capable of absorbing without harm.  A good thing, since the 4 cylinder diesel auxiliary is run twice a day while at anchor just to recharge the batteries.

Re: Engine Start Battery Options

Reply #48 –
My Delco 40si brushless alternator needs no excite wire.  The 40SI uses a Remote Sense wire that reads the actual voltage at the start battery. This signals the alternator to boost its output to compensate for the voltage drop and the actual voltage of the start battery to reduce charge time.

http://www.delcoremy.com/getmedia/f651dcc3-60db-4186-80eb-154b8111fdf0/Delco-40SI-Single-Page-Brochure-3-16.pdf.aspx

If you have multiple battery sets the amps that can be pushed into each set depends on the the overall resistance of the batteries and connections and the voltage of the batteries in each set.  The higher the charge level in the batteries the harder it gets to add more charge.  It is like filling a water tank from the bottom.  It is easier when it is 1/2 full and harder to push water in as it gets fuller. It takes more pressure (voltage) to push water (amps) into the tank when it gets close to full.

So if your house batteries are pretty well charged and you start the coach you just pulled a bunch out of the start batteries.  You will push more amps into the start batteries than the house batteries for a while until the two sets are closer to being equally charged.

Maybe a simplified way of looking at it but it works for me.



Re: Engine Start Battery Options

Reply #49 –
My understanding is that most smart alternators output 14.15 volts? 

Re: Engine Start Battery Options

Reply #50 –
"Most"  is a big corral to be generalizing.  Not so on the Delco.

Re: Engine Start Battery Options

Reply #51 –
Seems this thread has run its course, so I will wrap it up with my conclusions (for what they are worth).  I have considered the info presented here (thanks to all) and believe the following plan will work for our crew, the way we use our coach, and based on our level of technical expertise.

1.  I will replace our two old Red Top start batteries with a new O'Reilly AGM8D.  It will (hopefully) fit in the existing battery rack, and will work just fine with the existing cables.  I will use fresh "military" style battery connectors to hook up the cables.

2.  I will replace our still functional 25-year old Hehr Powerline diode isolator with a new Victron ArgoFet 200 amp 2-bank isolator.  By doing so, I retain the original factory alternator-to-battery charging layout, while enjoying the benefits of more modern technology.  The new isolator should be a bolt-in swap, and will be connected to the existing battery cables, which are in good shape.

3.  I will retain the Trik-L-Start "thief" battery maintainer that has served us so well for 4 years.  It does a fine job of keeping our start batteries topped off when our coach is parked (plugged in to 50 amp) in our driveway and when camping at full hookup parks.

4.  I will replace the existing boost solenoid with a Blue Sea Systems 7701 ML solenoid, which has a 500 amp continuous rating, 1450 amp 30-second cranking rating, and zero power draw in "ON" and "OFF" position.  Doing so will retain the OEM boost circuit design and function, while providing me with additional battery charging options when in dry camping mode.  If I wish to utilize our augmented battery storage capacity, I can simply activate the 7701.  Combining the battery banks will increase my available amp hrs by 50%, and will allow rapid recharging of both banks using our solar panels and/or generator + inverter/charger.


I believe the above plan will add extra capability and options to our battery system, while retaining the elegance and KISS-ness of the original FOT factory design.  I hope this will meet with the approval of the electrical gurus on this Forum.

Re: Engine Start Battery Options

Reply #52 –
Sounds like a good plan Chuck. We have certainly well chewed this subject. Please keep us informed of your progress and results. 😎

Re: Engine Start Battery Options

Reply #53 –
Chuck, you might want to replace the 4 ga cables from the two battery posts on the isolator to the two sides if the boost solenoid with bigger cables.  The 4 ga cables are probably the minimum size for the amps for that length of wire but bigger would not be a bad thing.  Your alternator to the isolator is perhaps a 2 ga cable, this would be a good size to go from the isolator to the solenoid.

If you have an easy source for cables great but you can order any size and length cables from Bay Marine Supply with the lugs you need on both ends.

Re: Engine Start Battery Options

Reply #54 –
Thanks, Roger, for the tip.  My OEM wiring schematic shows the wires to be "2RD" from alternator to isolator, and also "2RD" wires from both of the isolator battery posts to the boost solenoid.  I assume "2RD" means a red 2 gauge wire?  If so, I should be good?

I will verify the actual wire sizes next time I'm under the coach, just to be sure.

My OEM cables from the boost solenoid to the batteries, and all my battery cables, are shown to be "000" which I think is called "triple-aught"?  When AM Solar installed my solar system and Magnum inverter, they used "000" and "0000" cables for the high amperage circuits.

Re: Engine Start Battery Options

Reply #55 –
I think your isolator may have originally been over by the wheel well?  If so then the longer cables from the isolator to the boost relay would make a 2 ga cable make sense.  At the head of the bed box the cables were maybe 16" long so 2 ga was probably sufficient.  Yes 4RD means 4 ga Red.  With a bigger alternator I just didn't want those smaller wired to be choke points.

Re: Engine Start Battery Options

Reply #56 –
Here's my isolator panel as it is now, in factory stock configuration (plus the add-on Trik-L-Start).  The big fat muffler is long gone...
 

Re: Engine Start Battery Options

Reply #57 –
Chuck,my panel looked exactly like yours,redid the whole thing,all new components and put back in the same spot,after sanding and painting all rusted frame parts.We went with the smaller 28si alternator,keeps the 13.8 even at low idle.