Using battery sense on your alternator?

[Kettlewell]

I've read various alternator posts of yours with great interest, particularly your ongoing experiment using a "dumb" regulator and WalMart batteries. I'm curious if you have found an 8MR Leece-Neville alternator (Prestolite) that puts out 90 amps and has a battery remote sense connection on the attached regulator. I can't find one in their catalog that does this and puts out 90 amps. Some of the lower-rated 8MR models do--for example a 65-amp unit.

And, of course the secondary question, which might actually be more important, is do you think that having a remote sense is important when using built-in or attached regulators. All of the remote, supposedly "smart", regulators do this, along with battery temperature, etc. If you don't do this it would seem that you are probably getting less than 14.4 volts at your batteries, unless you have them very close to the alternator and/or have humongous cables.

 

[Maine Sail]

I've read various alternator posts of yours with great interest, particularly your ongoing experiment using a "dumb" regulator and WalMart batteries. I'm curious if you have found an 8MR Leece-Neville alternator (Prestolite) that puts out 90 amps and has a battery remote sense connection on the attached regulator. I can't find one in their catalog that does this and puts out 90 amps. Some of the lower-rated 8MR models do--for example a 65-amp unit.

And, of course the secondary question, which might actually be more important, is do you think that having a remote sense is important when using built-in or attached regulators. All of the remote, supposedly "smart", regulators do this, along with battery temperature, etc. If you don't do this it would seem that you are probably getting less than 14.4 volts at your batteries, unless you have them very close to the alternator and/or have humongous cables.

First let me say welcome aboard!

Sensing the battery would certainly be necessary if you use a diode based splitter but is not necessary if your battery to alternator cable is sized appropriately for minimal to no VD. Almost no one uses diode based splitters any more due to the roughly .7+/- volt drop. Most stock wiring harnesses run the alt though about 10-12" of #12 or #10 wire then to the battery switch then to the bank. With this type of path you can often see a VD in the wire..

Size the alt cable to the max alt output and you'll have minimal to no VD. The stock Mitsubishi alt on our current engine puts out 14.4 volts and that is what I am seeing at the battery post but it has been re-run direct to the house bank via 4GA wire..

Also the 8MR 90A versions have an adjustable stock VR so if you have a voltage drop in your cable you can compensate it out. Simply run the motor with the batteries at 100% state of charge and NO LOADS on the bank. Measure the output at the B+ terminal of the alt and the battery post of the house bank. If you have a VD differential simply adjust the screw until the battery post voltage matches what you want to set your absorption voltage at. You'll have minimal amps flowing at full charge but that is where you want to set the absorption so you don't over voltage your batts. 14.4 is a good general voltage for wets that won't be a gassing voltage very often in the North East unless your batts are in a hot space. If they are in a hot space I would not suggest a dumb regulator as 14.4V can be come way to high when the temps climb. With the cold waters here in Maine I've yet to see my battery compartment much above 80F but if you live in a warm area or have batts in the engine space, which is not good, then an external reg with temp sensing is pretty much a "should do".

The funny thing with external regulators is that I see only about 10-15% of them installed that are actually using the temp sensing, which is perhaps the most important feature.

There is NOTHING wrong with external regulators and they have MANY benefits, the #1 issue for me being temp compensation, but many coastal cruisers/weekend warriors are not in dire need of the $1500.00 charging system they have been led to believe they "must have"...

If I had a dollar for every time I heard "I spent $1200.00 on a 125 amp alternator and regulator and I've never seen it put out more than 40 amps, what's wrong?" I'd be retired by now... This is the typical dock stored, shore charged boat with two group 24 wets who spends one weekend night on the boat about five weekend per year. No real "need".....

 

[Kettlewell]

That makes sense, but unfortunately most "dumb" regulators are so dumb they don't let you adjust the voltage, so you're beasically stuck with what you get. For example, I've been using various remanufactured Delco 10 SI and 12SI variants for quite a few years, and I've only recently discovered that the internal regulators on these are typically set at 14.8 volts due to GM's desire to properly charge the lead-calcium Freedom batteries that were around when these alternators were designed. I have had reasonable success with this "dumb" set up and standard 12-volt wet cells, though I am not happy with how often something fails in the alternator. The flip side is that they are cheap and easy to get repaired or to fix yourself, and parts are available everywhere (including Colombia and Honduras, in my experience). Cheap clones are readily available at any auto parts store. I will have to investigate more carefully to figure out what is happening on my boat because I don't recall reading 14.8 volts at my main voltage meter, which is connected direct to the batteries--if my memory is correct I've been seeing about 14.4 volts there, which is about right.

Another question. Have you found any good "smart" regulators other than the usual marine Balmar, Xantrex, and Ample Power? They all seem to be quite expensive for what they are, and I have heard of a lot of failures, particularly with the Balmars. It would seem that there should be some industrial or commercial trucking version of these things that are reliable and cheaper.

 

[Bill Roosa]

You can trick your internal regulator to produce more voltage by adding a resistor into the battery sense circuit. Course that is going to requrie some research and taking appart the alternator but that sounds like no big deal to a sailor of your caliber.

Welcome aboard

 

[Kettlewell]

that sounds like no big deal to a sailor of your caliber.

I'm just a neophyte when it comes to alternators, and I enjoy continuing to learn. The problem isn't so much increasing output as finding a durable, relatively inexpensive alternator, that is easy to adjust the voltage up or down. I personally would feel a bit ripped off to spend a fortune for a name-brand marine alternator and regulator if I could purchase an industrial, car, or truck unit for maybe 20% of the cost that did the same thing. Even many of the so-called "smart" marine regulators appear to be rather limited in their voltage adjustments. For example, I have been reading today that apparently Trojan and some other companies say that you should be charging at 14.8 volts after all, in order to achieve maximum capacity. I noted also that Sterling's alternator regulators and their alternator to battery charger (doesn't require changing anything on a standard alternator) use a 14.8 volt set point. So maybe my really dumb Delco 12 SI alternator with built in regulator set at 14.8 volts isn't so bad after all.

Anybody have any experience with the Sterling products? Made in the UK, but sold through a distributor in Maine. The guy who runs the company in the UK has a bit of a reputation for being abrasive, and he has some different ideas on battery charging, but I read a lot of kudos on the UK Web sites. Plus, the Sterling stuff is much cheaper than many of the other well-known marine brands.

 

[Maine Sail]

I'm just a neophyte when it comes to alternators, and I enjoy continuing to learn. The problem isn't so much increasing output as finding a durable, relatively inexpensive alternator, that is easy to adjust the voltage up or down. I personally would feel a bit ripped off to spend a fortune for a name-brand marine alternator and regulator if I could purchase an industrial, car, or truck unit for maybe 20% of the cost that did the same thing. Even many of the so-called "smart" marine regulators appear to be rather limited in their voltage adjustments. For example, I have been reading today that apparently Trojan and some other companies say that you should be charging at 14.8 volts after all, in order to achieve maximum capacity. I noted also that Sterling's alternator regulators and their alternator to battery charger (doesn't require changing anything on a standard alternator) use a 14.8 volt set point. So maybe my really dumb Delco 12 SI alternator with built in regulator set at 14.8 volts isn't so bad after all.

Anybody have any experience with the Sterling products? Made in the UK, but sold through a distributor in Maine. The guy who runs the company in the UK has a bit of a reputation for being abrasive, and he has some different ideas on battery charging, but I read a lot of kudos on the UK Web sites. Plus, the Sterling stuff is much cheaper than many of the other well-known marine brands.

Mark Grasser (sp) is the guy who runs the US branch of Sterling here in Maine. Nice guy. I have one of their regulators and while not fancy or as adjustable as a Balmar they do okay. The instructions are a weak point with them though but Mark is a good guy who can help. Any alternator can be converted to external regulation. 14.8 can work well so long as it is temp compensated. You will burn off more water but will charge faster. 14.8 with hot batteries is not so good...

 

[Kettlewell]

It seems like a lot of us are using too low a charge voltage based on some things I've been reading lately, like this (see page 9), this, and this.

 

[Roger Long]

and this.

I could certainly believe "this". Back when I was flying small planes, pilots were learning that engine manufacturers were advising to adjust the mixture (in aircraft you fiddle with the mixture constantly because of changes in air density with altitude) at the setting that subjected the engines to the greatest mechanical stress, wasted fuel, and created the most cylinder deposits. Why would they do that?

At that setting, the engine is most tolerant of small problems that ought to be fixed such as leaks in the induction air hosing. An engine that was fully up to spec could be run much leaner than the recommendations at the price of a hint of roughness. However, it took some understanding. One benefit of "Lean of Peak" operation in my mind was that you would become aware of any small problem and could get it attended to. Engine manufacturers didn't want to deal with a large number of complaints from pilots who didn't understand what was going on under the cowl so they simply recommended (which meant you had to operate your engine "wrong" whenever an FAA examiner was in the plane with you) the setting that created the least customer service. Selling new engines sooner was a bonus although I'm sure a few pilots never got to buy their second one.

 

[Maine Sail]

There is much wrong with our buddy Bob's posts so I would not no where to begin. His general point of charging at higher voltages is acceptable though provided you are also charging at the recommended charge current for the battery. Trojan recommends 10-13% of Ah capacity. I don't know too many sailors willing to submit to an alt at 10% of bank size..? Many boaters are running alts capable of hitting the max acceptance which is why most charge at between 14.4 and 14.6. Interestingly enough Trojan recommends the MAX size for "fast charging" current at 20% of Ah capacity. For a 225 Ah bank this is just 45 amps. 14.4 V is the gassing voltage and anything above will require much more frequent watering events.

If you are talking a small solar grid not capable of much more than 5% of Ah capacity then there is not much harm done in charging at slightly above gassing but charging at high rates of current and high voltages is generally not done because folks have dealt with the results.

Deep cycle wet cells will "self limit" the current but will often heat up if the voltage and current is pushed hard. If the battery heats up you really need to decrease the charging voltage or attenuate it. All one has to do is watch an external regulator with battery temp compensation and if pushing up against acceptance the voltage will dial back automatically when the battery gets hot..

With the Balmar 612/614 you can program two separate "absorption" voltages and set them for time limits.

I do find his post regarding certain small solar regulators to be spot on as it applies to many marine installations. Our bank eventually got charged back to 100%, even with a fairly dumb on/off Flex Charge PV7 regulator, but it took a LONG, LONG time to do so. With the MPPT controller we dropped our time to "full" by over 4 days becuase it does not shut ON & OFF like a cheap shunting controller will.

You really need to take advice given by a guy who is claiming a fully charged Trojan is 12.85 volts when Trojan says their batteries are full at 12.72 V. I have never seen a rested Trojan wet cell put out more than 12.73V resting voltage even when brand new a barely broken it. He clearly still has a surface charge or has not let them sit long enough for a true OCV or hydrometer test.

Again nothing wrong with charging higher, if the batts can take it, just be careful and use temp compensation.

 

[Bill Roosa]

But MS, if you don't recommend a 500 amp alternator (when all you need is a 45 amp one) and an external regulator, and solenoid isolators and shinny paint, ..... how are the manufactures of such items going to put their kids through college?
We owe it to them to buy their stuff even if we don't need it. It will make us feel better too.