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Topic: 24SI Alternator check (Read 9634 times) previous topic - next topic

Re: 24SI Alternator check

Reply #20 –
Quote from: dlkj07 –
The thing is, I often get voltage in the low 12's intermittently when I'm driving at highway speed so not sure that's it...

Does this only happen when the headlights are on?  If so, do you also show lower oil pressure?  Do you also show higher coolant temperatures?  Do you have the electroluminescent dash?

There are a couple of issues.  First, especially with coaches with an EL dash that have a headlight conversion, is high coolant/low oil readings when the headlights are on.  It's been mentioned sporadically over the last 12-15 years.  James Stallings at Xtreme is working on a fix (wiring harness.)

Second is what Foretravel sometimes used for connections on the chassis battery wiring (low voltage readings).  See this post

Chassis Battery Compartment Refresh

Either issue could cause intermittent voltage fluctuations.

Re: 24SI Alternator check

Reply #21 –
Quote from: dlkj07 –
Ok, here it is...

Lights off after draw down, Engine off
Alt  12.5
Isolator chassis lug  12.5
Batteries  12.5

Engine on 1100 rpm, lights off
Alt 13.8
Iso chas lug13.8
Batt 13.7
We have not ascertained what type chassis battery you have.  I am going to assume that it is AGM.

So, looking at your test results, first thing we can say is you don't seem to have any cable or connection problems, because volt readings at all three points remain consistent in all 3 tests.

Next, with your chassis battery bank pulled down to 12.5 volts, you started your engine.  With engine running at 1100 rpm, and no big loads on the battery, you read 13.8 at the alternator and 13.7 at the battery.

In my opinion, your alternator is not producing sufficient voltage.  Yes, it does seem to be "functioning", but it is NOT acting in the manner required to fully charge AGM batteries.  The internal voltage regulator may have been damaged by running the alternator for several years with those two small mystery wires improperly connected to the "I" and "R" terminals.  You can search online for "AGM Battery Charging Voltage Chart" and find this info for yourself.  The excerpt below is from Google AI search:

Charging Stages:
AGM batteries go through three charging stages: bulk, absorption, and float.
Bulk Stage: The charger provides maximum current to bring the battery to about 80% capacity, with the voltage rising to around 14.7V.
Absorption Stage: The charger maintains a constant voltage (around 14.4V to 14.7V) to reach full charge, reducing the current.
Float Stage: Once fully charged, the charger drops the voltage to a lower level (13.6-13.8V) to prevent overcharging and maintain the battery's charge.

I went back and found the Forum thread where you first had this alternator installed.  That is when your battery charging troubles started:

Alternator output

8600310 24SI New Alternator | Product Details | Delco Remy

You received the information at that time suggesting that you had a problem.  But, as you say, because you also have solar panels and a generator to help keep your chassis batteries charged, it never became a BIG problem.

Again, IN MY OPINION, your best move would be to replace your 24Si with a proper DUVAC alternator.  This will allow you to retain your battery isolator (which appears fairly new) and it should solve your charging problems.  You can search online for J180 Hinge mount DUVAC alternators.  Try searching for genuine Leece Neville 2824LC (beware of cheap clones).  If you go this route, there is plenty of installation info available on this Forum.

If you want to stick with a Delco alternator, I would recommend your upgrade to a 200A 28Si (model 8600307).  This will also require replacing your battery isolator.  See the isolator links in my Reply #1 in this thread.

https://www.delcoremy.com/getmedia/90520e29-6966-4656-a04e-9053e59b5929/28SI-Single-Page-Brochure-4-16.pdf.aspx?ext=.pdf

Re: 24SI Alternator check

Reply #22 –
My dash voltage gauge would read low sometimes too. I checked out alt, wiring, etc. The problem was the ignition relay at the dash.

Re: 24SI Alternator check

Reply #23 –
Quote from: Michelle –
Does this only happen when the headlights are on?  If so, do you also show lower oil pressure?  Do you also show higher coolant temperatures?  Do you have the electroluminescent dash?

There are a couple of issues.  First, especially with coaches with an EL dash that have a headlight conversion, is high coolant/low oil readings when the headlights are on.  It's been mentioned sporadically over the last 12-15 years.  James Stallings at Xtreme is working on a fix (wiring harness.)

Second is what Foretravel sometimes used for connections on the chassis battery wiring (low voltage readings).  See this post

Chassis Battery Compartment Refresh

Either issue could cause intermittent voltage fluctuations.
I'm using a reading from my Bluefire app, which I believe comes from the ECM correct? All those other readings are working properly on my dash.

I'll check into the connection post, thanks

Re: 24SI Alternator check

Reply #24 –
Quote from: Chuck & Jeannie –
We have not ascertained what type chassis battery you have.  I am going to assume that it is AGM.

So, looking at your test results, first thing we can say is you don't seem to have any cable or connection problems, because volt readings at all three points remain consistent in all 3 tests.

Next, with your chassis battery bank pulled down to 12.5 volts, you started your engine.  With engine running at 1100 rpm, and no big loads on the battery, you read 13.8 at the alternator and 13.7 at the battery.

In my opinion, your alternator is not producing sufficient voltage.  Yes, it does seem to be "functioning", but it is NOT acting in the manner required to fully charge AGM batteries.  The internal voltage regulator may have been damaged by running the alternator for several years with those two small mystery wires improperly connected to the "I" and "R" terminals.  You can search online for "AGM Battery Charging Voltage Chart" and find this info for yourself.  The excerpt below is from Google AI search:

Charging Stages:
AGM batteries go through three charging stages: bulk, absorption, and float.
Bulk Stage: The charger provides maximum current to bring the battery to about 80% capacity, with the voltage rising to around 14.7V.
Absorption Stage: The charger maintains a constant voltage (around 14.4V to 14.7V) to reach full charge, reducing the current.
Float Stage: Once fully charged, the charger drops the voltage to a lower level (13.6-13.8V) to prevent overcharging and maintain the battery's charge.

I went back and found the Forum thread where you first had this alternator installed.  That is when your battery charging troubles started:

Alternator output

8600310 24SI New Alternator | Product Details | Delco Remy

You received the information at that time suggesting that you had a problem.  But, as you say, because you also have solar panels and a generator to help keep your chassis batteries charged, it never became a BIG problem.

Again, IN MY OPINION, your best move would be to replace your 24Si with a proper DUVAC alternator.  This will allow you to retain your battery isolator (which appears fairly new) and it should solve your charging problems.  You can search online for J180 Hinge mount DUVAC alternators.  Try searching for genuine Leece Neville 2824LC (beware of cheap clones).  If you go this route, there is plenty of installation info available on this Forum.

If you want to stick with a Delco alternator, i would recommend your upgrade to a 200A 28Si (with "S" terminal).  This will also require replacing your battery isolator.  See the isolator links in my Reply #1 in this thread.
Chuck,
My chassis and house batteries are AGM, though I'm going to throw a wrench into all this when I upgrade to house lithium's in the future.
I'll look into a DUVAC alternator since it sounds like my alternator is not working at optimum output...maybe because it was wired incorrectly in the first place. 🤷‍♂️

Re: 24SI Alternator check

Reply #25 –
Quote from: dlkj07 –
Chuck,
My chassis and house batteries are AGM, though I'm going to throw a wrench into all this when I upgrade to house lithium's in the future.
In that case, then I would change my recommendation and suggest you seriously consider upgrading to the 200A Delco 28Si (model 8600307)

At the same time, you could totally remove your diode based isolator and install some type of "smart" DC-to-DC charging device.

But before you buy anything, you will want to read through the Forum posts by members who have switched to lithium house batteries to get their thoughts on how to charge the lithium bank while protecting your alternator.  Charging mixed battery types can get tricky, but others here have made this move, so no need to reinvent the wheel.

See sample DC-to-DC charging info post below from a popular ForeForum Influencer:

Update Isolator/Auxiliary Start Panel

Re: 24SI Alternator check

Reply #26 –
Quote from: dlkj07 –
I'm using a reading from my Bluefire app, which I believe comes from the ECM correct? All those other readings are working properly on my dash.

Correct, so real numbers.

It's only the dash gauges that read incorrectly/wonky with the EL/headlight issue, and the usual workaround has been to use VMSpc, ScanGauge-D, or Bluefire.  We use Bluefire. 

Re: 24SI Alternator check

Reply #27 –
Quote from: Chuck & Jeannie –
In that case, then I would change my recommendation and suggest you seriously consider upgrading to the 200A Delco 28Si (model 8600307)

At the same time, you could totally remove your diode based isolator and install some type of "smart" DC-to-DC charging device.

But before you buy anything, you will want to read through the Forum posts by members who have switched to lithium house batteries to get their thoughts on how to charge the lithium bank while protecting your alternator.  Charging mixed battery types can get tricky, but others here have made this move, so no need to reinvent the wheel.

See sample DC-to-DC charging info post below from a popular ForeForum Influencer:

Update Isolator/Auxiliary Start Panel
I was leaning that way too because I've already done quite a bit of reading on the DC DC charger and I believe in my current situation I could add it with my AGM's and then it would already be there when I add lithiums. But I'll do a little more digging just to make sure... at this point I'll go with your recommendation and get the 28SI.

Re: 24SI Alternator check

Reply #28 –
Quote from: dlkj07 –
...at this point I'll go with your recommendation and get the 28SI.
So remember, the 28Si must see voltage on the B+ terminal to start charging.  The easiest way to accomplish this is to move the alternator charging cable from the center post on your isolator over to the chassis battery post.  This will eliminate the need for a SENSE wire, because the alternator will directly sense the voltage on the chassis battery through the charging cable.

EDIT: Ignore my statement (above) about the SENSE wire.  Even if alternator is connected directly to chassis battery, you should also run a SENSE wire from the chassis battery POS(+) post to the alternator "S" terminal.

With the chassis battery being directly charged by the alternator, you can still use the BOOST switch to combine the coach batteries with the chassis battery.  OR, just keep your coach batteries charged using your solar panels when dry camping, or the inverter/charger when plugged in or running generator.

Re: 24SI Alternator check

Reply #29 –
Quote from: Chuck & Jeannie –
This will eliminate the need for a SENSE wire, because the alternator will directly sense the voltage on the chassis battery through the charging cable.
Yes, the Delco 28SI will function without a SENSE wire, but as recommended by the Delco brochure, a SENSE wire connected to the chassis battery terminal will allow the alternator to compensate for any voltage drop in the cabling for optimum performance.

The selected media item is not currently available.

Re: 24SI Alternator check

Reply #30 –
Peter,

I understand the purpose of the sense wire with the 28Si.  In fact, as you may remember, when I installed a new 28Si on our coach, connected directly to our start battery, I DID elect to run a sense wire.  So I'm not disagreeing with your comment in any way.

Delco Remy 28SI Alternator Installation

However, looking at the Delco factory brochure that you posted (above), it does raise a question in my mind.  In the drawing labeled "With Remote Sense" the red sense wire appears to be longer than the B+ charging cable.  Assume (for arguments sake) that this was the case in "real life".  That is, the sense wire is actually longer than the B+ charging cable.  The purpose of the sense wire is to compensate for voltage drop in the charging cable.  Why would we not see the same, or greater, voltage drop in the sense wire?

Going back to my coach as an example, when I installed the 28Si I decided to upgrade the charging cable and the sense wire.  The OEM charging cable was 2 AWG and the sense wire was 18 AWG.  I elected to upgrade to 2/0 welding cable for the charge cable, and to 10 AWG for the sense wire.  My new charging cable (unlike the diagram in your post) runs in one unbroken section from the alternator straight to my AGM8D starting battery.  My new sense wire follows the exact same (unbroken) path.  In fact, they are tied together along the whole length with zip ties.

So, on my coach at least, the charging cable and the sense wire are exactly the same length.  In addition, the charging cable is much larger diameter than the sense wire.  Thick wire has less electrical resistance than thin wire.  Why is the battery voltage seen by the "S" terminal on my 28Si "better" (more accurate) than the voltage seen on the B+ terminal?

Like I said, I'm not disagreeing with your comment...just curious about the reasoning behind the whole "sense wire" concept.

Re: 24SI Alternator check

Reply #31 –
Chuck,

Good question. The reason why the SENSE wire can be much smaller (and possibly even longer) and work fine is that it is sensing voltage with very little current (probably just a few micro-amps). So there is virtually no voltage drop on the sense wire.

The main alternator cable is carrying a very large current - possibly up to 200 amps - so the cable needs to be sized to handle this current. Your use of 2/0 cable was a good choice. The 10 gauge SENSE wire is fine, but it could have been 18 gauge with no issue.

Edit:
The reason the alternator B+ voltage is not accurate as the SENSE voltage is the alternator will be maintaining the voltage only at that point - to say 14 volts. But let's say the current demand is 200 amps with a resulting voltage drop of say .5 volts at the battery, now the battery is only getting 13.5 volts. A sense wire to the battery will tell the alternator now to maintain THAT point at 14 volts, raising the B+ voltage to 14.5 volts to cover the cable voltage drop under high load. Once the current goes back down the alternator will adjust to keep the battery at 14 volts at all times.

Re: 24SI Alternator check

Reply #32 –
Peter,

I figured you would supply a logical technical answer to my question.  That is why I value your comments so highly.  ^.^d

Cheers!

Re: 24SI Alternator check

Reply #33 –
Quote from: prfleming –
Yes, the Delco 28SI will function without a SENSE wire, but as recommended by the Delco brochure, a SENSE wire connected to the chassis battery terminal will allow the alternator to compensate for any voltage drop in the cabling for optimum performance.

The selected media item is not currently available.
So the wire that was hot with the key on and connected to the "I" lug on my current configuration wouldn't work as the SENSE wire once I install the 28SI correct? Or does it matter that it's only hot when key is on. As previously mentioned I do not know where those 2 small wires that were connected go once they leave the alternator, just that one is hot with key on ("I" lug) and the other (connected to the "R" lug) read 6 volts when the engine is running. I realize that these wires were probably connected incorrectly and maybe not needed at all with the 24SI without a SENSE lug.

Re: 24SI Alternator check

Reply #34 –
Also, I drove the coach today and dropped it off to get some work done and the voltage on my Bluefire was reading 13.4 consistently. That is with the B+ from the alternator connected directly to the chassis battery lug on the isolator. Normally it would fluctuate to a lower voltage then back up as I drove so something is better.

Re: 24SI Alternator check

Reply #35 –
Quote from: dlkj07 –
So the wire that was hot with the key on and connected to the "I" lug on my current configuration wouldn't work as the SENSE wire once I install the 28SI correct?
Yes - that is correct.  "Hot with key on" won't work as sense wire.

Re: 24SI Alternator check

Reply #36 –
To add to Chuck's comment,

No, the "hot" with ignition won't work as the SENSE wire. The SENSE wire needs to be directly connected to the chassis battery. I would recommend to run a new SENSE wire if you upgrade to an alternator with SENSE capability.

The "hot" with ignition could still be useful if you decide to put in a 28SI and also change your isolator to one with an excite terminal. If you remove the isolator and connect the 28SI alternator directly to the chassis battery you won't need the excite wire. As mentioned previously, connecting an excite wire to a Delco alternator can cause permanent damage. The "I" terminal is for an Indicator lamp connection.

It's hard to know where the other wire is connected with a reading of only 6V, I would leave that one disconnected and just tape it.

Re: 24SI Alternator check

Reply #37 –
Alternator brands is a vigorously debated topic on this forum, I wanted to throw a suggestion into the mix.

Here is a source (DelStar - made in Canada) that would be worth considering for anyone looking at upgrading. (I have no financial connection with this company).

DelStar offers alternators very similar to Delco models including the 28SI, here is a 200 amp model that is brushless which will provide improved performance and reliability over a brush design.

https://www.delstar-hd.com/pdf/160/D100-16100.pdf
 

Re: 24SI Alternator check

Reply #38 –
Quote from: prfleming –
No, the "hot" with ignition won't work as the SENSE wire. The SENSE wire needs to be directly connected to the chassis battery. I would recommend to run a new SENSE wire if you upgrade to an alternator with SENSE capability.

Agreed.  And a little more "reason why": 
You want correct voltage to the chassis battery. A sense wire connected to the chassis battery or the chassis battery side of the diode-based battery isolator gives the alternator accurate data.

But, an ignition-hot wire is does not accurately represent chassis battery voltage.  Depending on where it is connected to an ignition- hot source has gone through fuses, relays, connections and lengths of wire.

And, depending on where the ignition-hot source comes from, changing in loads on that circuit (head lights, dash HVAC fan, etc) will send falsely low voltage signals to the alternator which would lead to over-charging voltage to the chassis battery.