Battery Bafflement

gksmith · 03-12-2020, 07:33 PM

My coach alternator has quit charging the coach batteries first thing in the morning after stopping overnight. I admittedly have previously abused my coach batteries due to ignorance, but I have gotten by with them until now. They will take a charge from shore power or the genset, but not from the alternator. However after running the genset for only 15 minutes and turning it off, voltage does go to the batteries from the alternator. The lead acid batteries do go to a very high discharge level overnight (which I know is not good practice) but they usually are still able to power the 12 volt accessories in the morning. Previously voltage would immediately go to the coach batteries upon starting the coach engine. Now it seems that the coach batteries need to be "primed" via 110v to take a charge from the alternator. I have a Progressive Dynamics PD4645 power converter if that makes a difference. Is it possible the power converter does not let 12v pass through to a highly discharged battery, but does pass through 12 volts that are converted from 110 v?

A side note which may or may not be relevant is that the genset will not start off the coach batteries in the morning (as expected due to the low voltage) until i connect the two battery systems together maually through my Blue Sea ML-ACR. They do not connect together automatically as they should and formerly did when starting the coach first thing in the morning. But upon manually latching the batteries together the engine battery voltage is getting to the coach 12v system to give enough power to start the genset. So it seems that engine voltage is going into the 12v system to start the genset but the engine voltage will not get passed on to the coach batteries until, again, "primed", all through the same cable from the alternator to the power center. And the low coach battery voltage keeps the ACR from operating properly. Why?

Comments/suggestions will be appreciated!

Rockwood27 · 03-12-2020, 08:10 PM

What year, make, model of RV do you have? The info will help us give you a better response.

gksmith · 03-13-2020, 05:11 AM

I have a Leisure Travel Freedom 4M on a 2002 Dodge RamVan 3500 chasis.

GallenH · 03-13-2020, 06:36 AM

Others will know more about this than I do but have you measured the voltage of your house battery in the morning without load? You mention that there is power to run your 12v accessories in the morning but not enough to start the genset. Sounds like your house battery does not have enough power. My alternator goes directly to the house battery and not through the convertor. Shouldn't you be able to measure alternator output also?

Don't know much about the logic of the Blue Sea but I thought that the manual latch on these was to provide power from the house battery to serve as an emergency chassis engine start. Not the other way around.

Again others will know much more than me. But I'd start measuring. Good luck.

booster · 03-13-2020, 10:15 AM

If I am reading this all correctly, I think everything is working as would be expected, but the batteries do not have enough capacity or are shot.

The Blue Sea ACR is probably one of the models with a low voltage lockout which is probably about 9-10 volts so no charging until it sees that much on the battery side. The PD charger is the only think saving you at this point as most of them are power supply style and are able to control voltage without a battery reference. Many/most smart chargers will not initiate on a dead battery so you would not have any charging source at all unless you jumpered the ACR with a wire or had one with manual over ride.

Going forward, you likely need new batteries and if you are abusing them as badly as it appears with extremely deep discharges all the time an increase in capacity would also be needed. Once you start getting below 20% state of charge on a regular basis the life of batteries can get much shorter, although there is a large variation between brands and types of how much worse and how fast.

gksmith · 03-13-2020, 06:53 PM

Thanks for the suggestions. Yes, I do measure the voltages, using a digital multimeter when testing and plug in digital voltage readouts when observing. I an sure I need new batteries, but I am on the road and was hoping to wait until I got back home to thoroughly test the batteries, taking them out, properly charging them, and testing each cell with a hydrometer. The baffling charging problem only started the last couple of days after being on the road for two months, almost always boondocking. Last night we did check into a RV site and plugged in for overnight for the first time almost four weeks although we did not use the unit while staying at my daughter for a couple of weeks. Usually we drive quite a while between stops, but last week the travel time between stops was considerably less, but we tried idling the engine to make up some of the difference. We will probably try to limp home for two weeks and see what happens. Plus I will observe what takes place after last night's full charge and our future boondocking. Thanks, again.

engnrsrule · 03-19-2020, 05:38 PM

I had similar issues with my Roadtrek (Sprinter). I upgraded from one 12v 90Ah battery to two 6v 235Ah (golf cart) batteries and they perform far better. They also fit exactly in the existing battery space. Also added victron battery monitor to get better visibility to coach battery performance. A battery swap out should not be too hard on the road, and would give you chance to evaluate the ancillary system performance during the rest of your trip.

ChicagoTom · 03-19-2020, 10:14 PM

Battery separator

Sehc · 03-20-2020, 02:09 PM

Time for a new battery bank. Your battery is shot.

gksmith · 03-24-2020, 05:10 PM

I gave up and replaced my coach batteries on the road. But my bafflement continues. In the morning, I cannot start my genset without manually switching my batteries together using the external switch on my Blueray ACR. Before, with the old batteries, if I tried to start with the battery system set on the automatic switching position, a rasping noise would take place (not unusual for discharged batteries), but the genset would start upon manually switching the batteries together. Now with the new batteries, nothing happens (not a sound) when trying to start the genset on the coach batteries, but will easily start when tying the batteries together. What is even more puzzling is that if I return to the automatic switching mode on the ACR while running the genset, after a few seconds, the genset dies. In the meantime, though, it does charge the coach batteries. What could cause this? This situation did not formerly exist. The new batteries do maintain their charge overnight and have good voltage in the morning.

Comments will be appreciated!

GallenH · 03-24-2020, 11:51 PM

So I'm still wondering what your voltage measurements show. Your first post appeared to say that your coach battery level went down a lot at night but still was enough to power lights, etc. In fact, I believe that you said it discharged to a level where it wouldn't accept a charge off the alternator. That's a pretty steep discharge. Other comments pointed to the potential lockout on the blue sea as the possible cause to the inability to accept alternator charging.

I'm curious as to the battery level prior going to bed and in the morning now that you have new batteries.

I don't have a genset so here's a question for others: Is it possible that a degenerating start motor or something else in the genset could be causing an unusual draw? Something that progressively has gotten worse.

gksmith · 03-26-2020, 04:48 AM

To determine my voltages, I use a 12 volt plug-in USB adapter that also displays voltage. I have found these readings correspond with the ones that I get at the batteries with a multimeter. The voltages I am going to report are now by memory, as I have been back about a week. With the old batteries, my voltage would usually be about 12.1 in the evening but would often be about 10.8 in the morning. The only draw would be the refrigerator (on LP) and two cell phones, plus occasional LED lights. The voltage once went as low as 8.8 after a few days of no driving, with the refrigerator not even working. Now, with the new batteries, the normal charged state after driving is 12.4 and the next morning would be 12.1. When running the genset, the voltage is about 13.4.

I am most baffled by the operation of the BlueRay ACR, as it is not acting like it used to. If I set it on automatic and run the genset, after about one minute, it will switch to the battery systems being separated and the genset dies. But, if I set manually to tying the systems together, it runs fine.

The genset starts just fine when using the engine battery, but absolutely nothing on the coach batteries. A weak starter might be a possibility. I do need to have the genset serviced (fuel pump needs replacing) so I will have the technician check it out.

hbn7hj · 03-26-2020, 05:06 AM

My guess is your new batteries are not getting a full charge. It could take as much as two weeks at 13.7 volts to charge them. Charge them with a battery charger that can provide 14.4 volts for a couple of days then see where you are.

What you really need is a shunt based battery monitor.

You could use a smart 3 stage converter upgrade. You need to be able to see 14.4 volts with the generator running and batteries charged.

gksmith · 03-27-2020, 02:43 AM

Quote:

Originally Posted by hbn7hj

My guess is your new batteries are not getting a full charge. It could take as much as two weeks at 13.7 volts to charge them. Charge them with a battery charger that can provide 14.4 volts for a couple of days then see where you are.

What you really need is a shunt based battery monitor.

You could use a smart 3 stage converter upgrade. You need to be able to see 14.4 volts with the generator running and batteries charged.

I checked voltage tonight after being on shore power for a couple of days and it is 12.8 volts, but still no go trying to start the genset off of coach batteries. I had previously upgraded to a Progressive Dynamics PD4645 power converter. Is that not what you have in mind? I am quite sure it is 3 stage.

I will also try charging with an external charger -- I do not know what voltage it provides, but will find out. I will see what the ending voltage will be.

What do you recommend for a shunt based battery monitor?

Thanks!

hbn7hj · 03-27-2020, 05:58 AM

Don’t know why the generator won’t start with 12.8 resting voltage on the batteries. It should, so something else is wrong and it is probably simple. Put an ohmmeter across the starter solenoid. The power is in the battery but it isn’t getting to the starter? That doesn’t explain why it works with combining batteries.

Putting a voltmeter on the output of the starter solenoid during a start attempt with and without combined batteries should tell you something.

I use the Bogart battery monitor. It has a case that mounts on the wall.

There is a Victron battery monitor. It mounts in an instrument hole but I think they have a case for it.

The battery monitor answers a lot of questions and will be useful even after you get the generator problems solved.

GallenH · 03-27-2020, 06:02 AM

I also have a Progressive Dynamics and I believe that you are correct in assuming that it is a 3-stage. It's not the best. But a workable solution. I'm charging a LifeLine AGM battery and I believe that the resting voltage on it is in the vicinity of the 12.8 that you are describing. I think that hbn7hj is monitoring with a Trimetric shunt based. I'm using a Victron. I'd listen to hbn7hj for advice. He's worked a lot with battery systems.

But my feel is that you should have enough to kick over your genset. I'm still suspicous of its condition.

hbn7hj · 03-27-2020, 06:12 AM

Maybe we should be looking at the generator ground? It is grounded through the mounting brackets to the frame. Also through the AC ground line, I think.

My battery ground to chassis was extremely corroded and needed to be repaired. (2003)

This doesn’t address the combined battery start unless it then can use the chassis battery ground. Check the coach battery ground connection or jump it with a known good ground-battery negative to chassis with a battery jumper cable.

Looking at the positive side hasn’t gotten us anywhere. Look at the ground side.

The more I think about it you have a bad connection between the coach battery and ground. It is the only thing that covers all the symptoms.