[cknuth]

Hi Folks,
By unwelcome coincidence, I seem to be having something similar this weekend.
Brief background: Last week, I spent a bit of time prepping the coach to travel. Attempted to revive the old golf cart coach batteries - despite watering, correcting some inverter settings and several cycles of equalization, the house bank still settles at down to just above 11V - planning an ambitious replacement program sometime soon. On shore power or while driving, the inverter is trying to charge the house batteries, so the fridge and other inverted loads continue to function - just not on the house batteries alone. I also removed and cleaned up the engine batteries (with disconnect switch off,) checked their water, reassembled, restored the switch.

At startup for travel, the Silverleaf and analog gauges agreed on about 13.7V. Great drive from Phoenix to Bryce Canyon. Ten miles from destination, the Silverleaf alarm called out low engine battery voltage. It dropped to 11.9-12.1V in cruise. Alarm threshold was set to 12.5V. All other parameters normal. At the same time, the house inverter was still powering the fridge with no problem. We continued to the RV park and went on 50A shore power. All house power systems normal.

So it seems that the engine alternator is working but that engine battery is not charging. I had not used the merge switch. The Heart Interface Echo is seeing (disconnected from shore power after an overnight) 12.6V engine and 11.8V house.

Now back on shore power with the merge switch on, I'm seeing 14.5v absorb charging to the house and 14V at the engine battery.

Any suggestions on where to start troubleshooting?

Thanks,
Chuck

[Richard]

I would confirm the engine alternator is working by 1. Turning the merge switch off, measure engine battery voltage, crank engine and set on high idle, measure engine battery voltage again. It should be higher with the engine running.

You cannot assume that because the inverter was running the fridge that the alternator is charging the batteries. The inverter will invert UNTIL it hits whatever value you have the low voltage cutoff set.

Be careful with the merge switch until you find the problem or you could kill all the batteries in the coach.

If you have a bad house battery and you were driving with the merge switch on then you were putting a terrible load on the alternator.

[encantotom]

hi chuck,

a few things to see if it helps.

and if i get this incorrect, other gurus please jump in.

this is the way i understand how all this charging stuff works.

1. if you are running the engine, the alternator charges both the house and starting batteries through the battery isolator that is in the rear engine bay hatch where the echocharger and merge switch is. there are 3 studs on the isolator. one goes to the starting batteries, one to the house batteries and one to the alternator charging wire. the isolator has diodes that route the charging current to each battery bank, but does not allow the current to flow the other way. what that means is when the engine is running, the alternator charges both battery banks and when the engine is not running, it does no charging but does not allow the two banks of batteries to be tied together so both can discharge together. that is why it is called an isolator. there would be no need for it if you didnt want to charge both banks at the same time with the engine running.

2. the way our rigs are wired is there is another cable that goes from the start and one from the house terminals of the isolator down to the merge switch. that merge switch is the one controlled on the dash to let you merge the batteries together if one bank is too low to either start the genny or the coach engine. merge switch is explained in other places on the forum, but it has 3 positions for a reason. it takes current to trigger the coil to merge the batteries. one way of the switch allows the start batteries to do the triggering and the other position (other than the middle off position) to use the house batteries to trigger the coil.

3. the echocharger or whatever similar trickle charging system is used is to just keep the start batteries charged by stealing a low charging current from the house batteries. that assumes you have shore power or genny running. it does not allow the house batteries to be charged from the engine batteries. it is a one way gig.

you said in your post that when driving the inverter was charging the house batteries that simply is not possible because the inverter gets its power from the house batteries. the genny would have to be running and in that case the inverter would switch itself to standby since the genny would be providing all the house power needed. on shore power the charger portion of the inverter charger would be charging the house batteries only unless you have the merge switch on.

if after sitting disconnected from shore power overnite your engine batteries are at 12.6volts i would say they are charged. the house at 11.8v would make sense if you were running something and there was some discharge happening...like if the inverter was on.

you said the house batteries after equalization settle down at 11volts, but later you said that after sitting disconnected all nite they were at 11.8v. not sure how to reconcile that.

so two suggestions.

first.....load test your house batteries individually. that will tell you easily if they are ok. i have a load tester in my shop i use. but any battery shop or autozone or autoparts place will have one you can use.

second, make sure all your battery connections (big cables) are corrosion free.

third....as for the start battery going low while you are driving. the silverleaf measures from the ddec and the ddec gets it info on voltage from the alternator directly. if that happens again, just run your genny and merge the batteries. i drove a multi thousand mile trip that way when what i thought was my alternator was bad doing exactly the same thing. voltage would swing up and down dramatically. i tested the alternator and it was fine, but i have an external voltage regulator i thought was bad so i ordered a pricey new one. when i went to install it, i discovered the alternator charging terminal on the regulator was totally loose. i replaced the regulator anyway since i had the new one and all was well. so check those connections on the alternator itself or the stand alone regulator if you have one.

your house power systems are normal on shore power because the house batteries are not even needed when on shore power. they can be totally dead and shore power will still work the coach.

your house inverter will not function below a set voltage that is set on your control panel.

hope some of this made sense

tom

[cknuth]

Tom,
I appreciate your thorough response and received your VM. This gives me enough to get home tomorrow, which is huge. I'll then do the real work and report.

Thanks!

Chuck

---

Richard,

Thanks for your Sunday reply. Will compare pre- / post-start voltages in the morning and report. I'm merging on shore power to assure a morning start but will turn it off on the drive.

Cheers,
Chuck

[cknuth]

Here's the morning report as we get underway:

Engine battery before start 12.4V; after 12.4V
House battery before 11.5V; after 14.6V absorb
Isolator 12.5/12.1/12.1 before
12.5/12.1/12.1 after

So we started the generator and merged the batteries. Now engine battery 14.1V and house 14.6V absorb.
So generator is not putting out, and I will start looking at connections at home.
Thanks again.

[Chester Stone]

Chuck, did you replace the house golf cart house batteries? The house Interstate golf cart batteries were purchased at Costco a long time ago and I recall learning that they are not strong enough for the application. The engine batteries were almost new when you purchased the coach. I would start by replacing the house batteries, and if you want to continue with the golf cart application, get stronger batteries than Interstate. Good luck and I hope you are enjoying the coach.

[Richard]

I think you meant the alternator is not putting out.

[cknuth]

Richard, right, alternator inop. Thanks.
Hey Chester!
As you suggest, I haven't replaced those old house batteries yet. Saving up money and knowledge for a Lithium upgrade.
Great to hear from you!
Chuck

[encantotom]

chuck,

make sure if you have a separate regulator that it is not the issue before you through a new alternator on it

tom

[encantotom]

i checked my house and start batteries today. the amp-l-start is on green for maintaining

house at 13.27v start at 13.25v

all is good again

tom