Charging a 3rd battery from the alternator

Instead of the solenoid, use a battery isolator. That way, you can leave it connected all the time and whatever tools you might run off of the aux battery will not drain the main battery.

NAPA part number ST-85

Umm, that's what the solenoid does without the voltage drop.

Hmmm... Was *I* surprised earlier this week when the local NAPA store wanted more than $50 for the ST85 solenoid and then couldn't tell me whether it was a starting type or continuous duty type! So I went to the NAPA website, struggled through their multiple search choices, and found the ST85 for which they wanted $48.99 plus shipping! I also discovered that it was listed only as a starting type solenoid. There is another starting type solenoid (ST95) listed for about $28. No specs are provided for either; the apparent physical difference is that the ST95 has 3 connectors and the ST85 has 4 connectors.

So I did a search of the Camping World website and found one battery isolator listed and no solenoids. My local RV dealer gave me a sort of blank stare when I asked him about solenoids and offered to sell me a battery isolator.

So, the plot thickens... Can anybody tell me if a NAPA ST85 solenoid is rated for continuous service? I hate to spend $50 for something that's going to burn up.

Is there another similar or hopefully less expensive solenoid available that will do the job of isolating a vehicle starting battery from a deep cycle battery in a 12V system?

Otherwise, what am I missing?

TIA and best regards, John Kinney

Is this what you're looking for?

Thanks, that's just what I was looking for, too.

Here ya go

Still too much, though. I paid $14 (not sure if that was with or without tax, just looking in my log) for the last one I bought. I got it from Shipps RV sales in Chattanooga, TN. Shipps is also a $CW$ store. I recall the first one being $11 so maybe the $14 is with tax.

I despise Shipps for they way they shafted my mom on some repair work but I do know that they have these on the shelf.

Oh, "4 wire" vs "3 wire". Four wire brings both coil leads out of the case as in the one pictured above. Three wire has one side internally grounded to the case. I prefer the 4 wire type, as the steel case of the solenoid tends to develop corrosion against its mounting and that can make the circuit intermittant. With the 4 wire, you simply run the other wire to a good ground.

John

I found this solenoid at the bottom of the page that the other solenoid was listed. I like it better cause its cheaper by about $0.50, has a rating of

On Sat, 20 Jan 2007 21:44:10 -0500, JerryD(upstateNY) rearranged some electrons to form:

Actually if you dont have a business, then Graingers wont sell to you. You have to register your business with them and then they will sell you all you want. I used to get away with buying from Graingers at a local branch, cause I was in the Navy, but I would have to pay cash for everything or they would charge it to the ship... LOL Either that or I would have it charged to the Horse farm I worked for as a equipment maintenance guy. But I digress, you have to have a business or work for a business that is registered with them to buy direct from them.

Ford Tech

Ya that is a crappy change they made like a year ago... You can still buy up to $100 worth from Granger without an account.

And if you know anyone who does have an account, Granger will sell over $100 sales to you under that persons account... :-)

On Sun, 21 Jan 2007 07:56:00 +0000, My Name Is Nobody rearranged some electrons to form:

Well, I usually show my company ID when I buy stuff from them... (most of the time it's less than $100). I then get a discount off the catalog price. :-)

No, granger has changed that, they will sell to anyone, account or no, if the purchase is under $100.

Maybe your Graingers will sell to anyone but the one here won't. I called and the first thing she asked was the telephone number of the company I was calling for/from. When I said I was just a home owner, she said they were wholesale only.

Just make up a company name and use your cell number. They don't check and they don't telephone spam you so that's safe. The cell number won't be in any commercial business directory, in case they ever do check.

I've used a long-defunct company name for decades with them. I pay with a credit card or cash and everything's fine.

A company name and checking account is a handy thing to have around for a number of reasons. Very often it'll get you wholesale pricing at places like HVAC and appliance parts wholesalers. As long as it's not a corp or LLC and no income flows through, there's no paperwork. When you set up the bank account you use your SSN as the "business's" EIN. Only possible expense is whatever fees the bank might charge, usually zero if you keep a few dollars in the account.

Having some business cards printed up with the company name is handy too. Couple hundred for under $10 at most quick print places.

John

A company name and checking account is a handy thing to have around for a number of reasons. Having some business cards printed up with the company name is handy too.