Battery Charging Problem ***UPDATE***

[whizbang]

While dry camping in freezing weather, the charging system died for the dual type 24 house batteries (2002 Winnebago Mini).

It appears to be a solenoid system. It failed two years ago and the RV shop ran a new replacement wire "to tell it to charge".

I am going to fix it myself this time. (I am a ham radio operator and licensed general contractor, Tinkering are us). However, I have zero expertise in automotive charging systems.

My inclination too, is to remove the solenoid system and run a battery isolator instead. I had an isolator in my F350 twenty years ago and it worked great.

Comments or suggestions? I have no clue where to start, other than doing lots of homework...

[pianotuna]

Log,

Voltage may be the least accurate method to check state of charge. I suggest verifying the charge level a few times using a temperature compensated hydrometer. You may be surprised at of "real" state of charge where the battery charger goes into float mode.

[LOG]

pianotuna wrote:
Log,

How do you measure fully charged on your battery bank?

Fully charged on my batteries is when my battery charger goes to float mode.
Float mode on my battery charger depends on temperature of the batteries because it is temperature compensated. That would be somewhere close to 13.2 volts.
If measured at rest, without any source of charging, the batteries would measure around 12.7 volts.
When I pull into a campground after a day of driving (around six hours), and hook up to shore power, my battery charger goes almost immediately to float. If they were not fully charged at that time, the battery charger would go into Bulk mode.
I would like to add that my battery tester is a professional level OTC micro-load electronic battery tester that sells for more than $500.
It is not a simple multi-meter tester.

[pianotuna]

Log,

How do you measure fully charged on your battery bank?

[LOG]

pianotuna wrote:

LOG wrote:
It appears that your motorhome has the voltage drop problem that DrewE was explaining. And has nothing to do with a "smart" charging system.
Maybe you need a better battery isolation manager or combiner.

LOG,

I have dual charging paths with #8 wire (rating 50 amps) with dual solenoids, each rated at 200 amps continuous. I have manual control of the solenoids and charging from the alternator. Each charging path is protected by a 50 amp automatic circuit breaker.

If the house batteries are "hungry", then I see more than 75 amps of charging. (my meter only reads to 75 amps). On occasion I've observed at least one of the circuit breakers flipping off and then on.

On normal use, because my starting battery is given a maintenance charge when ever the sun is shining, I see little charging after the starter battery is full from the ecm's point of view.

I can "force" charging of the house bank by using the inverter and running the 1400 watt water heater. However this does, after about 20 minutes, cause the starter battery to go down to 12.3 volts. At that point, I use my manual control to stop the charging, and I disconnect the water heater. The reason for doing so, is the 1/3:2/3 duty cycle on the alternator which I do not wish to burn out.

After 40 minutes of highway driving, I can repeat the above process. The last hour of driving I use to return some charge to the house bank.

I can "see" one of the breakers flipping in and out if I run the engine and use the microwave (170 amps draw) and the induction cooker (70 to 130 amps) at the same time.

These observations are from 2013 when I had 8 identical marine jars, one of which was used as a starter battery, and the house banks were configured as 3 and 4. Both banks were wired in a balanced manner. The "house" bank was 875 amp-hours @ 12 volts.

It appears that your motorhome is not the typical motorhome that one would expect to see in a later model motorhome with a "smart" charging system as was explained in one of the first post in this thread by Theoldwizard1.
Would you provide an example of a newer motorhome that would not fully charge the house bank with the engine alternator.
My older 2005 motorhome does not have that problem.
I simply start the engine, drive to my destination, and when I arrive my engine battery and house bank are both fully charged, without my having done anything other than driving and listening to then radio.

[pianotuna]

LOG wrote:
It appears that your motorhome has the voltage drop problem that DrewE was explaining. And has nothing to do with a "smart" charging system.
Maybe you need a better battery isolation manager or combiner.

LOG,

I have dual charging paths with #8 wire (rating 50 amps) with dual solenoids, each rated at 200 amps continuous. I have manual control of the solenoids and charging from the alternator. Each charging path is protected by a 50 amp automatic circuit breaker.

If the house batteries are "hungry", then I see more than 75 amps of charging. (my meter only reads to 75 amps). On occasion I've observed at least one of the circuit breakers flipping off and then on.

On normal use, because my starting battery is given a maintenance charge when ever the sun is shining, I see little charging after the starter battery is full from the ecm's point of view.

I can "force" charging of the house bank by using the inverter and running the 1400 watt water heater. However this does, after about 20 minutes, cause the starter battery to go down to 12.3 volts. At that point, I use my manual control to stop the charging, and I disconnect the water heater. The reason for doing so, is the 1/3:2/3 duty cycle on the alternator which I do not wish to burn out.

After 40 minutes of highway driving, I can repeat the above process. The last hour of driving I use to return some charge to the house bank.

I can "see" one of the breakers flipping in and out if I run the engine and use the microwave (170 amps draw) and the induction cooker (70 to 130 amps) at the same time.

These observations are from 2013 when I had 8 identical marine jars, one of which was used as a starter battery, and the house banks were configured as 3 and 4. Both banks were wired in a balanced manner. The "house" bank was 875 amp-hours @ 12 volts.

[LOG]

theoldwizard1 wrote:
A smart charging system WILL NEVER FULLY CHARGE A "HOUSE BATTERY BANK" !

It appears that this is just an opinion.
I mistakenly understood it to be a fact.

[LOG]

pianotuna wrote:

LOG wrote:

Would you please provide the year, make and model of a motorhome that has a "smart" charging system that would do that.
Thanks.

My own RV exhibits this behavior. 2005 Kustom Koach.

It appears that your motorhome has the voltage drop problem that DrewE was explaining. And has nothing to do with a "smart" charging system.
Maybe you need a better battery isolation manager or combiner.

[pianotuna]

DrewE wrote:


Yes and no. The ECM sees the voltage at the chassis battery. Provided the two batteries are connected with a low enough resistance connection, the voltage will be practically the same at both batteries, and the ECM will see that same voltage and not deem the battery to be charged and drop the voltage until both are at whatever it thinks is fully charged.

Hi DrewE,

No. Even batteries that are side by side must be wired in a balanced manner. That would be the only way the ECM could "see" the house batteries. See the smart gauge site for an explanation if you do not understand balanced wiring. In an ideal world all the batteries would need to be identical.

[pianotuna]

LOG wrote:

Would you please provide the year, make and model of a motorhome that has a "smart" charging system that would do that.
Thanks.

My own RV exhibits this behavior. 2005 Kustom Koach.

[LOG]

DrewE wrote:

pianotuna wrote:

LOG wrote:
Lets say a new motorhome with a smart charging system also included a battery combiner that connected the chassis battery and the house bank when the engine is running.
Would the ECM still see the chassis battery as fully charged and drop the alternator voltage before both are fully charged?

Yes the ECM "sees" the chassis battery and drops the alternator voltage.

Yes and no. The ECM sees the voltage at the chassis battery. Provided the two batteries are connected with a low enough resistance connection, the voltage will be practically the same at both batteries, and the ECM will see that same voltage and not deem the battery to be charged and drop the voltage until both are at whatever it thinks is fully charged.

Not all motorhomes have a connection between them with a low enough resistance for this to work too well. That could be because the wire is insufficiently heavy, or there's a poor connection somewhere, or in some cases because an auto-resetting circuit breaker is clicking on and off (and, of course, has a very high resistance in the off state). The greater the resistance is in the connection, the greater the voltage drop will be to the house batteries, and the more prematurely the charge voltage will drop.

Thanks for that explanation. That makes sense to me.
However, my understanding is that we are talking here about a "smart" charging system on newer motorhomes that come from the factory with a system deigned to do that.

[DrewE]

pianotuna wrote:

LOG wrote:
Lets say a new motorhome with a smart charging system also included a battery combiner that connected the chassis battery and the house bank when the engine is running.
Would the ECM still see the chassis battery as fully charged and drop the alternator voltage before both are fully charged?

Yes the ECM "sees" the chassis battery and drops the alternator voltage.

Yes and no. The ECM sees the voltage at the chassis battery. Provided the two batteries are connected with a low enough resistance connection, the voltage will be practically the same at both batteries, and the ECM will see that same voltage and not deem the battery to be charged and drop the voltage until both are at whatever it thinks is fully charged.

Not all motorhomes have a connection between them with a low enough resistance for this to work too well. That could be because the wire is insufficiently heavy, or there's a poor connection somewhere, or in some cases because an auto-resetting circuit breaker is clicking on and off (and, of course, has a very high resistance in the off state). The greater the resistance is in the connection, the greater the voltage drop will be to the house batteries, and the more prematurely the charge voltage will drop.

[LOG]

pianotuna wrote:

LOG wrote:
Lets say a new motorhome with a smart charging system also included a battery combiner that connected the chassis battery and the house bank when the engine is running.
Would the ECM still see the chassis battery as fully charged and drop the alternator voltage before both are fully charged?

Yes the ECM "sees" the chassis battery and drops the alternator voltage.

Would you please provide the year, make and model of a motorhome that has a "smart" charging system that would do that.
Thanks.

[pianotuna]

LOG wrote:
Lets say a new motorhome with a smart charging system also included a battery combiner that connected the chassis battery and the house bank when the engine is running.
Would the ECM still see the chassis battery as fully charged and drop the alternator voltage before both are fully charged?

Yes the ECM "sees" the chassis battery and drops the alternator voltage.

[LOG]

theoldwizard1 wrote:

Check the voltage at the battery. It should be 14.0V-14.5V. Drive for at least 10 minutes. With the engine still idling, check the voltage at the battery. If the voltage is below 13.8V at the engine starting battery, you have a smart charging system.

A smart charging system WILL NEVER FULLY CHARGE A "HOUSE BATTERY BANK" !

Would someone with a newer motorhome with a "smart" charging system please address this.
My 2005 motorhome with a Ford E450 chassis will fully charge the engine battery and the house bank when using the engine alternator, generator, shore power, and solar panel.
If newer motorhomes will not do this, and require an after market part to correct the charging system, then the industry is going backwards. And hard for me to believe.

[bobndot]

Tnx for confirming that DrewE.