Add me to the ODD battery voltage issue

Topic: Add me to the ODD battery voltage issue (Read 1299 times) previous topic - next topic

Add me to the ODD battery voltage issue

July 16, 2019, 07:20:03 pm

Just spent a couple of weeks at the Wa. Coast and Mount Adams. While at Mt. Adams. We were hooked up to 50 amp, I of course had the inverters charger going as well as a 3 amp trickle charger to the chassis batteries. I did a maint clean of the start batteries posts and clamps. Upon starting the coach for the drive home. The engine spun over nice and quickly.

Two hours down the road we stop for lunch and shut the engine off. Upon a restart 30-45 minutes latter. The start battery voltage at the VMSPC shows 12V a little bit down the road it shows 11.8 YIKES! WTH!

So I start the genset and have the wife make sure the inverter was off and then press the charge button and I activated the boost switch. The voltage came up to 12.4V but then dropped back to 11.8-12 the remainder of the trip (about 100 miles)

After getting home. I go to the electrical panel and see that the charger is in float mode even though the start battery reads 11.5V. So I turned the charger off then back on. It went from charge to accept in a few seconds. I walk up front and the start batteries are reading 12.8V on the VMSPC. No low voltage fault on the VMSPC either.

Any clues?
Tonight I'm getting out the old dumb charger and charge each start battery that way and then check each batteries voltage.

Re: Add me to the ODD battery voltage issue

Reply #1 – July 16, 2019, 07:46:01 pm

Don't rely on the VMSPC as the last word for voltage. Go to the batteries and check with a digital meter with the engine stopped and then running. A battery just taken off the charger won't show a stable voltage for six hours. If low, follow Brett's earlier about the isolator. Naturally, check to make sure the batteries terminals are clean and have a good connection.

Pierce

Re: Add me to the ODD battery voltage issue

Reply #2 – July 16, 2019, 08:48:06 pm

VMSpc does not measure voltage or anything else. It simply reports the data reported on the data bus from the engine and transmission computers. I agree with Pierce, check voltage at the batteries or the isolator or the alternator.

Use the VMSpc Diagnostics Menu to see reported events. Be sure to look at History.

These kind of voltage changes point to an issue that you need to chase down. Alternator, isolator, connections,

Re: Add me to the ODD battery voltage issue

Reply #3 – July 16, 2019, 09:03:07 pm

Quote from: Roger & Susan in Home2 – July 16, 2019, 08:48:06 pm

VMSpc does not measure voltage or anything else. It simply reports the data reported on the data bus from the engine and transmission computers. I agree with Pierce, check voltage at the batteries or the isolator or the alternator.

Use the VMSpc Diagnostics Menu to see reported events. Be sure to look at History.

These kind of voltage changes point to an issue that you need to chase down. Alternator, isolator, connections,

Yes on the VMSPC just being the messenger. Just cleaned those battery connections a couple of days ago.
As soon as it cools off a bit. I'm going to do some measurements at the isolator and check both banks and then again with the coach running at high idle. I take it to measure the alternator output at the isolator, You use the center terminal and ground. Never have dealt with an isolator and two battery banks.

Re: Add me to the ODD battery voltage issue

Reply #4 – July 16, 2019, 09:31:32 pm

Took some measurements at the isolator. There are three terminal lugs. Both outside lugs measure 12.67 volts.

With engine running at high idle of 1150 RPM. The center lug measures a bit over 10 volts. But was bouncing around a lot between 7-10 Volts.

Maybe I have an alternator issue?

There were two faults logged.
1, 251-80 Power supply = Low voltage
2, 251-52 Power supply = Low voltage
The 251 SID code shows as real time clock power interrupted.

Both of these were on July 12th When I started the coach at the coast. It had sat all week and only the coach batteries got charged while running the genset. It turned a bit slow and I released the key before it started and that's when that code showed up. The code did not reoccur on today's trip.

Re: Add me to the ODD battery voltage issue

Reply #5 – July 16, 2019, 09:43:37 pm

Alternator post should be about 0.8v more than the house and start battery posts. Make sure your excite wire is in good shape. It should read what the start battery does. The excite wire is hot when ignition is on. Same with the sense wire, it is connected to start battery so same voltage.

Measure voltage (carefully) at the alternator to rule out a bad cable.

Re: Add me to the ODD battery voltage issue

Reply #6 – July 16, 2019, 09:57:32 pm

Before condemning the alternator, make sure the sense wire and if present, the ign wire are OK.

Re: Add me to the ODD battery voltage issue

Reply #7 – July 16, 2019, 11:32:46 pm

The ignition wire at the alternator has battery voltage when the key is on. When I started the engine and put it on high idle (1100 RPM) I checked the alternator output. 4.6Volts. Oh Oh.

I couldn't figure out how and where the other wire went. On the alternator it says "from #1 post of the duvac" HMMM!

Re: Add me to the ODD battery voltage issue

Reply #8 – July 16, 2019, 11:35:56 pm

Quote from: bigdog – July 16, 2019, 11:32:46 pm

The ignition wire at the alternator has battery voltage when the key is on. When I started the engine and put it on high idle (1100 RPM) I checked the alternator output. 4.6Volts. Oh Oh.

I couldn't figure out how and where the other wire went. On the alternator it says "from #1 post of the duvac" HMMM!

Is your volt meter on the right scale? Maybe 14.6

Re: Add me to the ODD battery voltage issue

Reply #9 – July 17, 2019, 12:05:22 am

Quote from: craneman – July 16, 2019, 11:35:56 pm

Is your volt meter on the right scale? Maybe 14.6

Yep. Minimum setting on my meter is 0-20 VDC

Re: Add me to the ODD battery voltage issue

Reply #10 – July 17, 2019, 12:06:52 am

Besides possible bad alternator you could have a boost solenoide that may be coming and going. With boost switch on all batteries should read the same voltage.

Re: Add me to the ODD battery voltage issue

Reply #11 – July 17, 2019, 05:56:06 am

BigD,

Your sense wire goes to a breaker on the same panel as the isolator is mounted on. It then goes to the same terminal as the A.C compressor gets it power. (unless someone has relocated it).
With your alternator putting out some power it is most likely that either a brush is stuck in the holder, the voltage regulator is failing or possibly you have a diode inside the alternator gone bad. Any of the 3 are not an expensive fix. If you have a bad stator or rotor (both a high $ repair) you wouldn't be producing any power.

Mike

Re: Add me to the ODD battery voltage issue

Reply #12 – July 17, 2019, 10:59:35 am

Here is the exact alternator for our coach. New, no core for $254 delivered. Sure cheap if you have one fail and the coach has to be towed or someone has to work on it. LEECE NEVILLE 160 AMP DUVAC ALTERNATOR MOTORHOMES RV'S 2824LC 2825LC EL-039...

How about just installing it where the AC compressor is/was? We don't use ours so the space goes to waste. One alternator could go to the engine batteries, one to the house. Get rid of the isolator then.

Pierce

Re: Add me to the ODD battery voltage issue

Reply #13 – July 17, 2019, 11:52:11 am

Good one. Bought a spare. Mine was recently rebuilt and works fine. Cheaper than my rebuild by $50. May swap the new for the rebuilt and store the rebuilt one. One diode was bad on mine which means the other 5 are 22 years old....,

Re: Add me to the ODD battery voltage issue

Reply #14 – July 17, 2019, 12:41:55 pm

I have two. The second is a one wire Delco wired to house bats. Did nothing to my isolator. Not sure if it bothers it or not .

Re: Add me to the ODD battery voltage issue

Reply #15 – July 17, 2019, 09:29:35 pm

BigDog,

I have had good luck getting my alternator rebuilt at Texas Alternator Starter Service in Austin. Came back looking like new with new bearings, internal wiring, and regulator for about $60 in 2011. More now of course. I know you are on the west coast, but if you can find a good shop to rebuild yours, might save you some $$, assuming you have an alternator problem which is what it sounds like. If you are up to removing and replacing the alternator, more $$ saved. Disconnect the start batteries first and label all the wires on the alternator. Good luck.

Re: Add me to the ODD battery voltage issue

Reply #16 – July 17, 2019, 10:18:48 pm

Quote from: Jerry Whiteaker – July 17, 2019, 09:29:35 pm

BigDog,

I have had good luck getting my alternator rebuilt at Texas Alternator Starter Service in Austin. Came back looking like new with new bearings, internal wiring, and regulator for about $60 in 2011. More now of course. I know you are on the west coast, but if you can find a good shop to rebuild yours, might save you some $$, assuming you have an alternator problem which is what it sounds like. If you are up to removing and replacing the alternator, more $$ saved. Disconnect the start batteries first and label all the wires on the alternator. Good luck.

Going to the NAPA store in the AM to run an alternator test to verify if the diodes have gone south. Seems that is likely the case as the alt still energizes but only manages 6.4 V @ 1100RPM.

The engine bay in the unicoaches are quite roomy and the alt looks easy to r&r. So I'll go the DIY route. NAPA has the Wilson exact replacement for the LN. Although thinking about the Delco SI28 and the zero loss isolator.

I'll shot this question out there. With the Wilson being a direct LN replacement. What does that mean for a change to a zero loss isolator?

Re: Add me to the ODD battery voltage issue

Reply #17 – July 17, 2019, 11:10:25 pm

Quote from: bigdog – July 17, 2019, 10:18:48 pm

With the Wilson being a direct LN replacement. What does that mean for a change to a zero loss isolator?

By "zero loss isolator" do you mean something like the Victron Energy Argo FET isolator, or a similar device? If so, it will not require any change in the alternator wiring, as long as the alternator sense wire is reading start battery voltage.

With the common diode based isolator, in order to fully charge the start battery, the alternator must increase its output voltage to make up for the voltage lost across the diode between the alternator post and the start battery post.

If the new isolator has zero voltage loss (or close to it) between the alternator post and the start battery post, then the alternator will simply supply the voltage required to fully charge the start battery. To the alternator, it will seem exactly like being connected directly to the start battery.

I am running the Victron Argo FET isolator, and it works just fine with my remote sense alternator.

'93 U280 Isolator Panel Upgrade

Re: Add me to the ODD battery voltage issue

Reply #18 – July 17, 2019, 11:22:14 pm

Jerry, consider a Delco Remy 40si series alternator. Brushless, more efficient, no excite wire needed, just a sense wire.

Victron makes a nice series of zero voltage drop isolators, ArgoFET as Chuck mentioned. Sterling makes a smart zero voltage drop isolator, the ProSplitR. They also make an Alternator to Battery charger, smart, faster recharge. Lots of options out there.

Re: Add me to the ODD battery voltage issue

Reply #19 – July 17, 2019, 11:36:00 pm

You will pardon me for mentioning again that the entire rv biz has changed to a auto combiner. No one uses a isolater. Too much power loss. That's why they have fins on it! Dead engine batteries. Customers unhappy.

Straight install where the isolator was. The boost switch is replaced by a off/auto/combine switch. No new wiring.

Run a wire to the starter relay and the house batteries are locked out during the starter relay being used unless you manually combine them or choose not to add the starter relay sense wire.

I give up. You can all replace your 20 year old tech with the same parts and kill batteries regularly.

Not right if you might REALLY need the coach to work.

Re: Add me to the ODD battery voltage issue

Reply #20 – July 17, 2019, 11:41:44 pm

Quote from: Chuck & Jeannie – July 17, 2019, 11:10:25 pm

By "zero loss isolator" do you mean something like the Victron Energy Argo FET isolator, or a similar device? If so, it will not require any change in the alternator wiring, as long as the alternator sense wire is reading start battery voltage.

With the common diode based isolator, in order to fully charge the start battery, the alternator must increase its output voltage to make up for the voltage lost across the diode between the alternator post and the start battery post.

If the new isolator has zero voltage loss (or close to it) between the alternator post and the start battery post, then the alternator will simply supply the voltage required to fully charge the start battery. To the alternator, it will seem exactly like being connected directly to the start battery.

I am running the Victron Argo FET isolator, and it works just fine with my remote sense alternator.

'93 U280 Isolator Panel Upgrade

So the sense wire tells the alt to increase voltage automatically to compensate for a diode loss and the opposite for a no loss isolator. I think I got that. Seeing all the posts about amps & voltage requirements had me scratching my melon.

Re: Add me to the ODD battery voltage issue

Reply #21 – July 17, 2019, 11:43:19 pm

Quote from: Caflashbob – July 17, 2019, 11:36:00 pm

You will pardon me for mentioning again that the entire rv biz has changed to a auto combiner. No one uses a isolater. Too much power loss. That's why they have fins on it! Dead engine batteries. Customers unhappy.

Straight install where the isolator was. The boost switch is replaced by a off/auto/combine switch. No new wiring.

Run a wire to the starter relay and the house batteries are locked out during the starter relay being used unless you manually combine them or choose not to add the starter relay sense wire.

I give up. You can all replace your 20 year old tech with the same parts and kill batteries regularly.

Not right if you might REALLY need the coach to work.

That sounds good. I'm open to anything.

Re: Add me to the ODD battery voltage issue

Reply #22 – July 17, 2019, 11:57:58 pm

Quote from: Roger & Susan in Home2 – July 17, 2019, 11:22:14 pm

Jerry, consider a Delco Remy 40si series alternator. Brushless, more efficient, no excite wire needed, just a sense wire.

Victron makes a nice series of zero voltage drop isolators, ArgoFET as Chuck mentioned. Sterling makes a smart zero voltage drop isolator, the ProSplitR. They also make an Alternator to Battery charger, smart, faster recharge. Lots of options out there.

The 40SI would be nice. But she who must not be disobeyed and comptroller of the Big Dog family budget nixed that as to expensive given the cost of that alt and the new run of very big cables from stem to stern needed to go from 160 to 240 amps.

Re: Add me to the ODD battery voltage issue

Reply #23 – July 18, 2019, 12:32:04 am

The batteries will only take so much input. Regardless of the alternator size. The LN has an adjustable voltage regulator on the unit.

See the eBay link on the deal on new ones. Look at the users. Gillig. Transit busses.

Std Delco puts our 14.15 volts to the battery as far a I have read, if the batteries are physically hot you are massively overcharging them. More than a volt. Ballooned cases.

As Brett has posted many times here you need 13,6 at the batteries to lessen the overcharge.

Unless you have 5 house 8d's to be able to charge at 1/5th C no use for the extra amps.

Especially at too high of a voltage.

Does the delco have adjustable voltage?

It's not a car. Long drives.

Like I said look at the eBay link for the LN where it mentions the adjustable voltage.

If we had lost power in flooded cells long ago we(I) used to turn up the built in voltage regulator to equalize batteries to restore capacity.

We did not have chargers that could do that. That's why the LN has adjustable voltage to tailor it to the use.

My 160 alt and 125 charger normally max out at 110-115 amps into three 8g8d mk gels.

Ah if you have Lifelines they may be able to take more amps? 20% faster charging than any other AGM as far as I have seen.

I bought another LN on purpose. 20 years life. 10-12 year house and engine batteries life reported here many times.

And you want to change it?

Cabling is fine. The batteries cannot take that many amps period

Re: Add me to the ODD battery voltage issue

Reply #24 – July 18, 2019, 08:12:57 am

For a 160 amp alternator look at a Delco Remy 28si.

Affiliate Notice