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...

[DrewE]

bobndot wrote:
I was thinking about long term storage in the future without shore power, I was going to try a Trik L Start but thought it might eventually run down both house AND chassis batteries while parked, not plugged in to shore power, while parked long term. It seems to me that the chassis battery will eventually deplete the house bank unless you also have solar in place.

The Trik-L-Start won't do that, at least not to any appreciable extent, because it only charges the chassis battery when the house battery voltage is above a certain threshold (I think high enough that the house battery is actually being charged). Otherwise, it's basically an open circuit. I guess the LED indicator would consume a few milliamps.

Without some source of energy, your batteries will run themselves down eventually (self-discharge) even with nothing attached--relatively quickly in warm temperatures, more slowly in cold temperatures. For long term storage, there's basically no way around needing solar or something to keep them charged.

[bobndot]

I was thinking about long term storage in the future without shore power, I was going to try a Trik L Start but thought it might eventually run down both house AND chassis batteries while parked, not plugged in to shore power, while parked long term. It seems to me that the chassis battery will eventually deplete the house bank unless you also have solar in place.


My chassis battery does run down over a week or so.
As an experiment, I already have an automatic Battery Tender Solar panel in a 10 watt size to use as a maintainer, so I tried that to maintain the chassis battery. I leave it on my dash. Seems to be working so far. I just tried this solar maintainer as an experiment to see if it would work, if I ever do store this rv. I normally just leave my rv plugged into shore power and not worry about batteries period.

[LOG]

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?

[pianotuna]

LOG wrote:
Sorry. I did not ask the question adequately.
In a motorhome after 2018, with a smart charging system, the alternator will never fully charge the house bank unless it has a DC to DC battery charger.
If that is correct, please explain why. Thanks.

It is correct.

IF you had 168 hours, with no loads, and constant charging at 12.8 volts--then the house bank would become fully charged.

At 13.8 volts the ECM "sees" the starter battery as full. Mine drops down to 13.2. But we don't drive constantly for a week at a time.

Trojan suggests 14.8 volts be used. That only happens in the vehicle if the starter battery is quite discharged, and not for very long at all.

Then you have voltage drop to contend with.

When my RV is in storage the solar charging system does get the job done--but it takes a week or so to get to 0.0 amps of charging. My bank is 566 amp-hours so at 25 C (77 f) fully charged is about 2.9 amps going into the bank.

I do use a trik-l-start to maintain the starter battery. My first batteries lasted from 2009 until 2017, and the starter battery a similar length of time. I moved to AGM telcom jars because laying down in the snow to check battery electrolyte levels is not much fun at -35 C.

[pianotuna]

Time2roll,

My point was that pulse charging is not going to change the basic chemistry that happens when charging. Some one is telling porkies.

[time2roll]

pianotuna wrote:
One glaring issue is "less need for temperature compensation". Sorry that is basic chemistry and no "witchery" will get around that need. Charging at -40 requires higher voltage and charging at 115 f requires charging be discontinued.

Yes OK and most RVing is closer in the 40 to 110 range and any typical multistage converter will do just fine.
And yes camping in -40 will need a lot more preparation than just a temperature compensated charger.

[LOG]

pianotuna wrote:

LOG wrote:
Am I understanding this correctly? The alternator can fully charge the chassis battery but will never fully charge the house bank.
Unless there is a DC to DC battery charger.
In other words, less than 13.8 volts can fully charge the chassis battery but cannot fully charge the house bank.

Yes, because there is voltage drop in the cables to the house bank, so it never sees 13.8. BTW 14.7 may be a more effective charging voltage.

My OEM from engine to house batteries was #8. I doubled the path with a second #8.

Sorry. I did not ask the question adequately.
In a motorhome after 2018, with a smart charging system, the alternator will never fully charge the house bank unless it has a DC to DC battery charger.
If that is correct, please explain why. Thanks.

[bobndot]

pianotuna wrote:
Charging at -40 requires higher voltage and charging at 115 f requires charging be discontinued.

Yes, that makes sense.

pianotuna wrote:
My OEM from engine to house batteries was #8. I doubled the path with a second #8.

I noticed a difference when I increased my #12 charge line to a #8. If I remember correctly, it took less time to charge up the house.
I never even thought of running two 8's. :C

[pianotuna]

LOG wrote:
Am I understanding this correctly? The alternator can fully charge the chassis battery but will never fully charge the house bank.
Unless there is a DC to DC battery charger.
In other words, less than 13.8 volts can fully charge the chassis battery but cannot fully charge the house bank.

Yes, because there is voltage drop in the cables to the house bank, so it never sees 13.8. BTW 14.7 may be a more effective charging voltage.

My OEM from engine to house batteries was #8. I doubled the path with a second #8.

[pianotuna]

bobndot wrote:
The algorithm term was new to me. I found a Flexcharge link specific to it. IMO, it appears to do a good job explaining what exactly it means. If its incorrect, please advise. Thank you.

explanation of algorithms

One glaring issue is "less need for temperature compensation". Sorry that is basic chemistry and no "witchery" will get around that need. Charging at -40 requires higher voltage and charging at 115 f requires charging be discontinued.

[bobndot]

The algorithm term was new to me. I found a Flexcharge link specific to it. IMO, it appears to do a good job explaining what exactly it means. If its incorrect, please advise. Thank you.

explanation of algorithms

[LOG]

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

Am I understanding this correctly? The alternator can fully charge the chassis battery but will never fully charge the house bank.
Unless there is a DC to DC battery charger.
In other words, less than 13.8 volts can fully charge the chassis battery but cannot fully charge the house bank.

[pianotuna]

theoldwizard1 wrote:

pianotuna wrote:
That is why a DC to DC voltage boosting device works better. You will still need a solenoid so that the starter battery is isolated from the house batteries when the engine is not running.

I have NEVER seen a DC-DC charger that will allow the house battery bank to send power back to the chassis battery without some kind of "bypass" being applied.

(FYI - A DC-DC charger actually first converts the incoming DC voltage to AC, runs it into a transformer (or some kind of inductor). The resultant AC is then converted back into DC. Current can not flow "backward" because DC current can not flow through a transformer/inductor.)

dc to DC is one way. But we don't want it to draw on the starter battery when the vehicle is not running. Therefore an isolation device needs to be used.

[bobndot]

oldwizard1,pianotuna, thank you for your helpful explanation. :C

[whizbang]

oldwizard.

I am going to pull the NEW house batteries out so I can inspect the solenoid behind them.

I will conduct the test you recommend.