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Old 13-01-2020, 17:32   #31
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Re: Alternator voltage sense

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.
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Old 14-01-2020, 04:44   #32
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Re: Alternator voltage sense

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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.
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Old 14-01-2020, 05:12   #33
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Re: Alternator voltage sense

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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.
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Old 14-01-2020, 08:55   #34
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Re: Alternator voltage sense

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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.
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Old 14-01-2020, 09:05   #35
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Re: Alternator voltage sense

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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.
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Old 15-01-2020, 01:35   #36
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Re: Alternator voltage sense

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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.
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Old 15-01-2020, 04:01   #37
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Re: Alternator voltage sense

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?
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Old 15-01-2020, 04:33   #38
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Re: Alternator voltage sense

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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.
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Old 15-01-2020, 04:58   #39
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Re: Alternator voltage sense

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.
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Old 15-01-2020, 06:47   #40
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Re: Alternator voltage sense

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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.
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