Electrical Questions

MotoMac · 12-07-2019, 09:12 PM

I have a 1999 Itasca SunFlyer M-33B Ford

I winterized the MH and put it into storage in late October. Took it to a uncovered storage facility, checked that everything worked, and put a cover on it. Since then we've had a few nights that dropped to single digits and then back to normal with highs in the 40s & 50s, with lows in the 30s.

I bought it from the original owner and it was in excellent condition with right at 50K on the odometer. The only exception is the light cracking in the decals, which appears to be fairly normal for one of that age. The MH has the original 10W solar panel and then the original owner added two 100W solar panels. All last summer and autumn they kept the batteries fully charged and maybe a little more. I did check the batteries in June and the acid was down about 1/4" from the bottom of the fill port liners. I topped them off then and it stayed fine until now.

I went over today to check on everything and found the house batteries down to nearly 9V and the fluid level was again down like before. Both batteries are 6V deep cycle units, are less than a year old, and hooked in series. No lights would come on and the generator would not even turn over from any of the two remote or the one local position....not even a click. The Itasca owner's manual was at home so I couldn't check for any info about charging it, plus my phone was also at home so I couldn't go online.

The chassis battery is fine and the MH fired up immediately.

So, after I got home and browsed around online and on this forum, I see that I probably either left the battery disconnect 'on', or left one or both of the inverters 'on'. This is my first MH and I wasn't aware these things had to be off.

So, it appears I need to charge the two house batteries. I did find several websites that said it is okay to charge the two 6V using a 12V charger. However, that still leaves a few questions.

1. Do I need to disconnect the batteries from the whole electrical system before I begin charging them?

2. Can I just use the battery disconnect switch to isolate them from the rest of the system or do I need to remove all the various wires hooked to the POS and NEG terminals?

3. There is no shore power at the storage facility, so I need a source of power to charge them. I have a gas-powered 2500W generator I can bring over and use it as a power source. The generator has a 12V outlet just for charging a battery, so should I use that or bring my regular battery charger and plug it into the 120V output of the generator and then connect it to the batteries? Which one would be best for a successful charge.

4. If the engine of the MH is running, does the alternator charge the house batteries? Should the battery disconnect be 'on' when I'm charging from the MH alternator? Would this be quicker than using my generator or battery charger? Will one method give a better or more complete charge than the others?

Sorry for the length of my post, but I'm just not familiar with the electrical system on this MH. My only previous experience is with towed toy haulers that were nowhere as complex as this MH.

powercat_ras · 12-07-2019, 09:41 PM

1. No.

You don't need to disconnect the batteries to charge them. The 6 volt batteries are in series with each other to operate the 12 volt systems in your coach.

2. No. Don't remove any wires. You use the battery disconnect to minimize battery drain during storage.

3. Use your generator's 120 Volt AC output to plug in the shore cable on the RV. The RV has a on-board 12 Volt Converter/Charger that will charge your coach batteries at a much faster rate (30 amps or more) than 12 volt outlet on the portable generator will. You need to have the battery disconnect in the NOT DISCONNECTED setting for the converter/charger to charge your coach batteries. You'll need to be on the generator charging for at least 2 hours to go from almost dead to somewhere between 50-80 % charged.

4. When the engine is running and the coach is disconnected from 120 volt power, the alternator "should" charge the coach batteries. You can confirm by pressing the switch on the monitor panel and see if all the 12 volt lights show on, this indicates charging. The battery disconnect should be in the NOT DISCONNECTED setting. Assuming your RV has a high output alternator, you should get a equal or slightly faster charge rate at engine idle speed than the on-board 120 volt charger. You could get a higher charge current of 50-60 amps at higher engine RPM such as if you were driving the coach.

Both methods will take over 3 hours to get a near complete charge, from their current "almost dead" state. I suggest charging at least 2 hours to get batteries to at least above 50% state of charge. Battery electrolyte freezing temperature goes down as state of charge goes. At 10% state of charge they can freeze and be damaged even at temps in the 20s.

rgvtexan · 12-08-2019, 08:28 AM

Randy

Nice answer.

MotoMac · 12-08-2019, 11:35 AM

Wow....great reply and fast too!!! Thanks so much for the very detailed information. As soon as it stops raining I'll head over there and get started!

Would it be okay to do 2 hours one day and then another hour or so the next?

Morich · 12-08-2019, 01:01 PM

This is another time when personal choice can make a big difference in what is "right".
For my use, I would rather take this situation differently and take the batteries out, take them home and then do a slow gradual charge, where I can check them once in a while and not try to force a slow trip into a couple hours.
Batteries tend to boil off water when they are charged quickly. When/if they run down, it damages them, so I favor having them handy at home and watching , rather than having idle time at the storage while I get antsy waiting and oding nearly nothing.
But that involves some mechanical work and it can get into the "personal choice" area.
I like slow and steady over a couple days over quick charging and possibly only getting a surface charge. Since they are home and safe, I can do an occasional check on them over the rest of the winter---while I figure out some of those little quirks of having an RV!
Different strokes for different folks!

MotoMac · 12-09-2019, 04:05 PM

Before I started into the charging yesterday, I took a voltage reading and it was around 8 pt something Volts. I could only spend about 90 minutes charging, but when I disconnected the generator, they were up to 12.6 Volts. I will go over again tomorrow and see how they are doing.

The original owner installed two 100 Watt solar panels along with the 10 Watt OEM unit. Unfortunately I have a cover on the MH, so they are of no use at all. Maybe I should cut a hole in the cover to let the sunshine through and not worry about it any more. To be honest though, I'd rather not slice up a $400 cover.

If it looks like they are not holding this charge, then I'll try again. If it still doesn't hold the charge, I'll take them home and add to seven other batteries I am cycling through the battery tender. The warranty ran out about 2 months ago but maybe I can get some help from the Interstate dealer.

powercat_ras · 12-09-2019, 05:57 PM

When charging lead acid batteries, their voltage can't be used to monitor state of charge until you let the batteries "rest" to dissapate something called "surface charge". So, even though you read 12.6 right after disconnecting the generator, this does not mean you got 100% charged.

You can put a small load on the batteries like one of your interior coach lights to dissipate surface charge in a few minutes, 10 or 15. Then voltage can be used to roughly estimate stored charge in lead-acid chemestry batteries.

12.6 , 100 %
12.4 , 80 %
12.2 , 60 %
11.9 , 40 %
11.6 , 20 %
11.3 , 10 %

Note that if your volt meter is even 0.1 volt off your voltage reading will mis-represent stored charge. A way to check the accuracy of your volt meter is to read a brand new 9 volt alkaline chemistry battery, your voltage should read 9.7 volts.

In 90 minutes, you likely only got to 50% at best. When you return to the RV I predict you will see a voltage reading below 12 volts.

Good luck.

Morich · 12-09-2019, 07:45 PM

Quote:

Originally Posted by powercat_ras

When charging lead acid batteries, their voltage can't be used to monitor state of charge until you let the batteries "rest" to dissapate something called "surface charge". So, even though you read 12.6 right after disconnecting the generator, this does not mean you got 100% charged.

You can put a small load on the batteries like one of your interior coach lights to dissipate surface charge in a few minutes, 10 or 15. Then voltage can be used to roughly estimate stored charge in lead-acid chemestry batteries.

12.6 , 100 %
12.4 , 80 %
12.2 , 60 %
11.9 , 40 %
11.6 , 20 %
11.3 , 10 %

Note that if your volt meter is even 0.1 volt off your voltage reading will mis-represent stored charge. A way to check the accuracy of your volt meter is to read a brand new 9 volt alkaline chemistry battery, your voltage should read 9.7 volts.

In 90 minutes, you likely only got to 50% at best. When you return to the RV I predict you will see a voltage reading below 12 volts.

Good luck.

This is a really big point that is often missed. Surface charge is very easy to misread. It was explained to me as being somewhat like adding black ink to a barrel of water. You will see lots of change in the color but, given time and letting the ink spread, you will find the "total" color change is far less. Part of my reason for wanting to have the batteries at home so that i can take it slow and easy on them, making sure that I don't charge them too fast or too far. so that I damage them for the long term.
I just changed out a car battery that was trying to lie to me. It got draggy when doing errands but checking the alternator, showed 14+ and when I stopped at home, the voltage was 12.2. after shutting it all down. But after 5 hours and no drain, the voltage was 9.6! Kind of expected as it is a three year battery that is five years old, so somewhat expected time to replace.

bobmac · 12-15-2019, 04:20 PM

MotoMac - I do not use a cover on my coach here in Ontario and after 10 winters, the coach still looks new. I have 400 watts of solar and I replaced my AGM batteries after 7 years. When using wet cells without solar, battery life was 2 to 3 years at best. My recommendation to you is to pull off the cover and sell it - your batteries will be better off. You need to keep the solar on the batteries all the time not just a couple of hours now and then unless you want to replace them frequently.I have a neighbor at the storage lot whose coach was scratched significantly with heavy winds when the cover got loose. I am not a fan of covering but many are. Good luck,

7997redtail · 12-15-2019, 05:44 PM

I like the great info in the first response and the idea about removing them and charging at home (that’s what I would do). But there is a third option.

While rving in Mexico for 6 months our golf cart batteries died. It was my fault I had mislabeled the switch that chose them. Anyways, because it takes so long to replace 1200, 1400or 1600 ah using a home/rv charger I removed them and took them to a battery shop and had them recharged.

Just a thought. Faster and no need to run the rv or a generator for hours.

BTW, I think they were going to do it for free but I gave them some money anyways. They were great.