Alternator voltage sense

[Bycrick]

The bigger wire suggestion, while fairly obvious, isn’t really as important as making sure that EVERY connection is "perfect" and that every component (switches, fuses, blocks, busbars, etc.) don’t add extra resistance.

2/0 wire has 0.779 ohms resistance per 1000’ (thousand feet). 4/0 wire is 0.049. So 50’ of wire in the alternator circuit (more than you ought to have), at 200 amps only has about 0.6v drop with 2/0 and about 0.3v drop with 4/0. With a 25’ total run, the wire likely isn’t your biggest voltage drop.

Look to the connections and components first.

[rom]

Originally Posted by Maine Sail

There are two types of 28SI internal regulators. One is considered "flat compensated" and no matter how hot the alts gets it should maintain 14.0V but as it gets cold temp can increase to as much as 14.3V (I forget the temp thresholds for where 14.3V occurs).

The other type is called "temperature compensated". The danger with this one is that the voltage adjusts both ways, up and down. In colder temps it can increase regulated voltage to as much as 14.7V and when hot can drop voltage to as low as 12.8V on some models.

Interesting information, thanks for sharing. So I guess I have the "flat" version, as I am always seeing the same max voltage (14.7V @alternator output) either cold or hot. That comes as another disappointment as I was expecting the VR to protect the alternator. But it opens new perspective as I can probably buy a new VR with different specs.

[john61ct]

Originally Posted by rom

I do not want the extra features and complexity (and cost) of external regs.

Yes really that or a DCDC device are really the only way to get good battery care out of an alt, in most cases.

GEL's lower voltage spec might be a good match, but with any sealed chemistry and long stints motoring, you still need to terminate charging, whether dropping to Float or taking the bank offline, once the bank is Full or longevity will suffer.

With FLA you just keep water topped up.

[Maine Sail]

Originally Posted by rom

Interesting information, thanks for sharing. So I guess I have the "flat" version, as I am always seeing the same max voltage (14.7V @alternator output) either cold or hot. That comes as another disappointment as I was expecting the VR to protect the alternator. But it opens new perspective as I can probably buy a new VR with different specs.

It does not sound like you have a genuine Delco 28SI?

While 14.7V may be okay for flooded deep-cycle batteries, or AGM's such as Full River, Odyssey or Northstar, but you won't have any float.

Without knowing what size and type bank you have, it is hard to advise.

[Maine Sail]

Originally Posted by rom

So, I will try to rephrase the question: is delco (half) stupid to provide a single wire for voltage sensing where they really should have provided a positive & negative pair for that purpose, like victron does. Or is it accepted as good enough because "drop should be minimal" as smac says.

No, they have built an alternator for a specific application type that never really "cycles" the batteries. The single positive v-sense suffices in this application. It's purpose is to aid in keeping battery voltage a bit higher for all the equipment that is running on-board a bus, EMS vehicle or heavy equipment.

The internal alternator regulator was not optimally designed for an application such as a boat, RV etc. but works ok for the design application the alternator was originally built for.

The Balmar MC-614 regulator uses Regulator B-/ (black wire in Ford plug) and terminal #9 for dedicated voltage sensing and this is your "two wire" v-sense.

[rom]

Originally Posted by Maine Sail

No, they have built an alternator for a specific application type that never really "cycles" the batteries. The single positive v-sense suffices in this application. It's purpose is to aid in keeping battery voltage a bit higher for all the equipment that is running on-board a bus, EMS vehicle or heavy equipment.

The internal alternator regulator was not optimally designed for an application such as a boat, RV etc. but works ok for the design application the alternator was originally built for.

The Balmar MC-614 regulator uses Regulator B-/ (black wire in Ford plug) and terminal #9 for dedicated voltage sensing and this is your "two wire" v-sense.

Well, that is somewhat the answer I was expecting. A bit disappointed as I was hopping the internal VR would reach 14.5V at battery posts and would have some kind of temp protection. Maybe the latter is not really needed with that type of beast though. I purchased the two of them from a website in belgium, came in a delco box, I bought them for genuine products but they may not be... (is there a way I can tell ?)



The rest is off topic but since I have my answer... I will keep the alternators like that, it is ok for me as I only need the extra power a few days a year. Remember I modified the VR to enable remote start/stop of the field. Other than that I have 1320W of solar & victron MPPTs taking good care of my 1000Ah vrla (allegedly Gel, Ultracell UCG). Longest PSOC in 4 years is 3 or 4 days. As for voltage drop, there is more than cable size at stake, maybe I 'll open up a new thread to share thoughts.

[Pascals Wager]

ROM as you have your answer i will jump in with a question,
I'm adding the MC614 to both my Valeo alternators on my cat. Both engine start batteries AGM, are charged thru an isolator. The house bank, LFP is on the other side of the isolator. Should the sense wires be connected to the house or start battery side of the isolator?

[rom]

Originally Posted by Pascals Wager

ROM as you have your answer i will jump in with a question,
I'm adding the MC614 to both my Valeo alternators on my cat. Both engine start batteries AGM, are charged thru an isolator. The house bank, LFP is on the other side of the isolator. Should the sense wires be connected to the house or start battery side of the isolator?

You probably know that AGM & LFP have different charging profiles. Of course you should favor the most expensive. Use a LFP profile on the balmar and connect it's v-sense to the LFP bank. Your AGM will likely be undercharged, but you can probably keep the original battery charger just for them, pluggued at the ouput of the inverter, and proceed with a proper charge every few days. Take that with a grain of salt, I have removed my start batteries, chargers, isolators etc... and I don't have LFP, yet.

[Pascals Wager]

ROM thanks for the quick reply. I'm still working on the final plan for the mixed battery types. At present they are charging together but all chargers are set to LFP profile. I think final plan will eliminate isolators and use B2B chargers from the house for them.

[john61ct]

Originally Posted by Pascals Wager

ROM as you have your answer i will jump in with a question,
I'm adding the MC614 to both my Valeo alternators on my cat. Both engine start batteries AGM, are charged thru an isolator. The house bank, LFP is on the other side of the isolator. Should the sense wires be connected to the house or start battery side of the isolator?

The power output from your MC-614 should go directly to House LFP and be optimized for their needs, so that's where V sense wires go, sensor for overtemp protection etc

also with secondary OVP OCP against overcharging (e.g. BMS, separate topic).

The charge rate should not be much over 0.4C, less if the cells are cold, a bit faster is OK when they're hot (which in general should otherwise be avoided if possible).

The Starter batts can then use whatever you think appropriate for getting topped up from House, lower current no problem.

[CarinaPDX]

You have a very good application for the Nordkyn voltage regulator - please look into it.

Your regulator is not going to be nice to most lead batteries - maintaining a high voltage and never dropping to a float voltage is a bad idea. But the internal regulator will, or at least should, be protecting the alternator from overheating and possibly other problems; external regulators need alternator temperature sense in order to protect the alternator, but are probably not as effective as the internal regulation for thermal management. So there is both a problem (fixed high voltage) and an advantage (alternator protection) with using an internal regulator. The reason to use an external regulator is to charge the batteries quickly using a 4-step regimen, while supporting a proper float voltage (4th step) for long battery life. Also, some external regulation can limit current (to protect the alternator) and delay charging during engine start.

The advantage to the Nordkyn regulator is that it allows the internal regulator to protect the alternator, and doesn't require any alternator modifications to install as long as there is an external voltage sense. It is able to cause the alternator to run through a proper 4-step charge, and offers other features as well. For me it solved the problem of having an N-type alternator - most US regulators are for P-type alternators only. Volvo-Penta engines come with a quality 115A Mitsubishi N-type with external voltage sense, so adding a Nordkyn regulator can be done very easily and not require modifications that would void the warranty.

Greg

[rgleason]

Attached is a Guest Universal Battery Switch pdf showing
Alternator Field Disconnect for External Regulators Wiring
to protect the Alternator.

I would be interested in responses (experience, thoughts and considerations) to the use of this field disconnect.
1. Will the contacts create much of a voltage drop?
2. I believe this wiring is different than what Balmar and Mainesail on marinehowto.com suggest.

[CarinaPDX]

If you have a selector switch in between the alternator and the batteries then I would absolutely use the field disconnect - a lot of alternators have been wrecked over the years by owners accidentally switching to "off". OTOH I would never use a selector switch for that purpose: a lot of batteries have not been charged because the owner forgot to switch to "both" while charging. A selector switch for consumption is a different matter.

There are so many good alternatives to selector switches now; it seems archaic to still be using them in the charging circuit. When I built Carina I installed isolation diodes instead, so the batteries were always isolated and always charged. There is some very small loss of power to heat with diodes, but with an external voltage sense it doesn't affect charging. This is a very robust solution. Another approach is to use a battery combiner, where one battery is permanently connected to the alternator and the other is connected through a relay when charging voltage is present. Not quite as robust but doesn't require external sense to charge properly. Both of these solutions apply the same charging voltages to both banks, whether appropriate or not. There are smart switches that can switch in one battery or the other, or both. Another alternative is to use a DC-DC battery charger instead of the combiner so that each battery receives appropriate charging voltages - probably the closest to ideal for charging different batteries (e.g. deep cycle house in one bank, starting battery in the other). None of these options should leave you with a fried alternator or a discharged battery, unlike the selector switch.

Greg

[smac999]

Originally Posted by Pascals Wager

ROM as you have your answer i will jump in with a question,
I'm adding the MC614 to both my Valeo alternators on my cat. Both engine start batteries AGM, are charged thru an isolator. The house bank, LFP is on the other side of the isolator. Should the sense wires be connected to the house or start battery side of the isolator?

I wound suggest getting rid of the isolator. Hooking straight to house. And going dc to dc to engine.

I had a huge issue with a brand new “low loss “victron Argofet last month. New 200a alt And ext reg feeding it. (Replaced the smaller int reg alt) I had I think a 0.3v drop in the 2/0 cable run to house bank. But the dam argo fet had an internal voltage drop of 0.4v to the house bank and 0v to the engine as it’s current based voltage drop. So sensing at the house bank. The engine bank was 0.7v higher and egine going over 15v. I ended up having to sense at the engine bank for saftey. And now the house is 0.7v too low (at bulk) and charging drops off too early. Dc System needs to be redesigned now.

[Stu Jackson]

Originally Posted by rgleason

Attached is a Guest Universal Battery Switch pdf showing
Alternator Field Disconnect for External Regulators Wiring
to protect the Alternator.

I would be interested in responses (experience, thoughts and considerations) to the use of this field disconnect.
1. Will the contacts create much of a voltage drop?
2. I believe this wiring is different than what Balmar and Mainesail on marinehowto.com suggest.

rg,


1. Most likely NOT because the field wire carries very little current. IIRC, Maine Sail says maybe a max of 7 A. Doesn't seem to be an issue, within reasonable lengths of wire, for #14AWG as recommended.


2. Couldn't one simply consider it is the different end of the same wire, i.e., connected at one end to the actual battery bank, while at the other end, instead of connected to the alternator is now simply connected to a switch that can turn off the field when the switch is turned to the OFF position? Of course, it's only for the model 2110A switch that has this feature.


Good questions, thanks.