Coach battery charging

[swetter]

Having a charging issue but I think I may have resolved. Everything I've read thus far has lead me to believe that while plugged into shore power my coach battery should charge. Well being new to Rving, I left the fridge in auto for a whole week with it not plugged into shore power. My LP fuel level is empty and my battery went down to 8.3 volts. (BTW I have a 97 Minnie Winnie 30 ft). So last night I installed some parts for my Onan genny that I ordered from Amazon. A fuel pump, fuel filter, and an air filter. While installing, I hooked up my house batt to a battery charger and got it back to 12 volts. I replaced the negative battery cable from the frame to the batter as it looked very corroded and old. I have left it plugged into shite power overnight and I am hoping that fixes the problem. The aux battery switch is in the off position. I will post later and hopefully the charger maintains the 12 volts. Any thoughts?

[Steve Ownby]

Originally Posted by swetter

Having a charging issue but I think I may have resolved. Everything I've read thus far has lead me to believe that while plugged into shore power my coach battery should charge. Well being new to Rving, I left the fridge in auto for a whole week with it not plugged into shore power. My LP fuel level is empty and my battery went down to 8.3 volts. (BTW I have a 97 Minnie Winnie 30 ft). So last night I installed some parts for my Onan genny that I ordered from Amazon. A fuel pump, fuel filter, and an air filter. While installing, I hooked up my house batt to a battery charger and got it back to 12 volts. I replaced the negative battery cable from the frame to the batter as it looked very corroded and old. I have left it plugged into shite power overnight and I am hoping that fixes the problem. The aux battery switch is in the off position. I will post later and hopefully the charger maintains the 12 volts. Any thoughts?

A fully charged battery will be at 12.8 VDC. The charger should start off charging at over 14 VDC and switch over time to about 13.2 or so for as long as you have it charging. A battery with no load and no charging input that measures 12 VDC is dead.


Steve Ownby
Full time since '07

[swetter]

How could it be dead? This is a deep cycle marine battery that I purchased less than 1 month ago. I've read they are meant to discharge and charge quite frequently. I suppose it's possible I got a bad battery.

[swetter]

Follow up question, with my volt meter, how do I test the charger built into the RV?

[Steve Ownby]

Originally Posted by swetter

How could it be dead? This is a deep cycle marine battery that I purchased less than 1 month ago. I've read they are meant to discharge and charge quite frequently. I suppose it's possible I got a bad battery.

Even deep cycle batteries should not be discharged to more than 50% state of charge. It's been a long time since I've looked at the charts but I believe that a battery with no load is at 50% state of charge at about 12.2 volts. It's possible that your charger is not getting the battery up to full charge.

The full discharge that your battery experienced may shorten it's total life somewhat but it should not be Ruined.


Steve Ownby
Full time since '07

[Steve Ownby]

Originally Posted by swetter

Follow up question, with my volt meter, how do I test the charger built into the RV?

It's somewhat dependent on your specific charging setup, but if your built in charger is working you should see an initial voltage of over 14. If a 3 stage charger, that will drop over time to float charge of about 13.2.

If you call Winnie tech support, they will be able to tell you how your coach is set up to charge and possible troubleshooting steps.


Steve Ownby
Full time since '07

[swetter]

Well I went and measured my battery this am and found that it is at 11.6! So in conclusion, my on board battery charger does not work! Great! Where do I go from here? Replace the battery? New charger?

[twinboat]

Before you condemn your onboard charger, make sure it is hooked to the battery. It may be hooked to the battery Aux switch and not work with it off.


Try leaving the Aux switch on and see if the volts come up.


That switch is for storing the RV, when no power is available.


Your new battery took a hit, but with a overnight charge, it should recover.

[HD4Mark]

Originally Posted by swetter

Well I went and measured my battery this am and found that it is at 11.6! So in conclusion, my on board battery charger does not work! Great! Where do I go from here? Replace the battery? New charger?

I'm not sure about your coach but our coach batteries do not charge from the inverter charger, only the house batteries do. The fridge would be wired to the house batteries though.

How ours works is there is a solenoid switch that will allow the engine to charge both the chassis and house batteries while running but the generator or shore power will only charge the house. If we are parked more than a few weeks I connect a charger to the chassis batteries for a day (or two for the two big batteries) due to some parasitic draws like the engine computer and some of the dashboard stuff.

If you are reading less than 12V on either set and plug in to shore power you will see 13+ volts from the charger if it is working and connected.

There are gadgets that will keep the chassis battery (batteries) charged like this Ultra TRIK-L-START Starting Battery Charger/Maintainer

[twinboat]

Coach and House batteries are synonymous. The chassis batteries, run the engine systems.

[grtharris]

swetter As per the drawings for your coach the chassis batteries will not charge with the battery disconnect engaged. I think that is what you are referring to as the Aux Battery switch. If the battery connections are corroded it will also affect the charging of the batteries. Without being connected to shore power connect your volt meter to the batteries check the reading then connect to shore power you should see a noticeable jump in the battery voltage up to around 13VDC.

[swetter]

Guys, all great suggestions. I have the aux switch on now. Hoping that was my problem. Thank you all.

[swetter]

Update, before leaving for work I peaked inside and heard a unfamiliar noise. It was the fan in the breaker box. Then I checked the coach batteries and they are at 12.1 and rising! Rookie mistake. I'm sure that,coupled with my bad cables are what discharged my battery so fast.

I will be on this thread a lot now. Thank you so much!

[swetter]

Also wanted to add that camp world wanted 1589.00 to troubleshoot my generator, another 15 for front brakes, and 2000.00. For a transmission seal replacement. With you guys and Amazon, I saved ait of money. Generator is working fine. I'll sub the brakes out to someone else. Transmission is not leaking at all. Bunch of crooks at camp world. Be ware!

[pokgunner]

It is beyond frustrating to me that, battery issues are by far the most common problem with RV’s yet the manufacturers do nothing to help. However many battery and charger manufactures do not help the situation. Most RVs are designed to last about 12 hours without shore power (or gen, engine) before you start hurting the life of the battery.

It is very likely that your OEM charger will not drop down to 13.2 volts, after it gets the battery fully charged. Usually then OEM charger is designed only to charge the batteries and will stay at 14 plus volts. If the battery is fully, charged this will “cook” the batteries, shortening their life and vaporizing the water. If you read the fine print in you manual it likely says something like: “If the unit is to be stored for extended (not well defined) periods, do no leave it plug to shore power. Instead run the engine at some interval.” What it will not tell you is that by running the engine, the alternator charges the battery.

If you have invested in new batteries it is probably a good thing if your charger is bad and you have to change it, because it likely should be changed even if there is nothing wrong with it. You should replace it with a “smart” charger, which will reduce the voltage as suggested by Steve Ownby. This lower voltage is known as a “float’ voltage and if the charger drops its output to the batteries float voltage, then you can leave the unit plugged into shore power and not risk “cooling” the batteries.

But not all “smart” charges are the same. You have to dig deep for some to find its specific output. They vary from, 12.9 to 13.8 for a float voltage. And not all batteries need the same float voltage, there are slight differences between batteries wet cell and AGM batteries, and among AGM batteries. (Even though they are called 12 volt batteries, they really are not. They should rarely be allowed to go below 12.5 volts, and if so charged back completely as soon as practicable.) A further complication is the fact that the float voltage for all batteries changes at different temperatures. The good chargers compensate for temperature, but again there is a variance of temperature compensation among manufactures.

But I will get out of the weeds and back to your issue. First every time you check the battery voltage, it should be at the battery. Depending on wire size there can be a noticeable difference between voltages measured at the battery versus somewhere else.

The fact that you battery drained to 8.3 volts is likely not only to the fact you left the fridge on. There is likely other load (by design or not) on the battery, even if you use the battery disconnect relay. In my case there was a partial short that was not enough to trip a breaker or blow a fuse, but increased the battery drain 25 times higher than designed. The only way to find the load is to use an amp meter (best location is between the battery negative terminal and the ground wire), and start removing fuses or tripping breakers until you see the amperage go down. Then you know that somewhere on that circuit is a load. If the total load is above 0.5 amps I would do something to reduce it (add relays in the circuit, or move the power source to the other side of the disconnect switch, fix a partial short, etc). Besides draining the battery a high load may fool a “smart” charger into thinking that the battery is charged less than it is.

You say that you charged it back up to 12 volts, which as I indicated is not fully charged. Note that a battery that is not fully charged will drain faster for any given load. The less it is charged the faster it will drain.

Finally most manufactures provide a charger that is way undersized, particularly if you are boon docking and relying on the generator to charge the batter. Take mine for example. If the OEM battery was down by 50% (and you should not let it get much lower, very often) the OEM charger would need over nine hours to fully charge the battery. If you are going to replace the charger and do much boon docking, you probably should increase the size of the charger. However there is a limit as to how fast a battery should be charged. An AGM can charge much faster than a wet cell.

[swetter]

Good info pokgunner. Can you name some smart charger manufacturers and models? I would be interested in installing one of those if it is a reletively easy swap.

[pasdad1]

The progressive dynamics models with the charge wizard are good.

[Tom N]

Your aux switch disconnects your coach battery(ies) from your converter/charger. Your batteries will NOT charge with the auxiliary switch OFF.

[pokgunner]

Swetter:

The “right” charger depends on a number of factors. Foremost is the battery manufacture’s recommendations and specifications, and in some cases that is not easy to obtain. What is the Amp Hour rating, the maximum charging rate, the absorption (bulk) voltage, the float voltage, and temperature comepensations. Another factor is; are you mostly plugged in or do you do a lot of dry camping.

As far as I know any multi stage charger will be “close” to optimal.

In my case I had replaced the OEM charger (it fried on my 2 weeks after the warranty) with and Intelipower charger. But because of the partial short I mentioned I drained the OEM batteries too often, and ruined the OEM batteries. I highly recommend that you check the load. On mine, after I fixed the short, I found nearly two amps of load wired between the batteries and disconnect switch. Now the only load there is the LP detector (0.3 amps).

So after I learned more about batteries and charging than I ever wanted to know, I replaced the OEM batteries with Lifeline’s batteries. Lifeline is very good about providing information about their batteries. But with the new batteries and the Intellipower charger it would take many (forgot how much, I think 12) hours to charge the batteries from a generator. Since I often dry camp for 2 weeks or more, and do not like to listen to the generator run, that was not acceptable. Lifeline batteries are better than most when it comes to fast charging.

So I decided to get more charging power and found that Xanrtrex’s True Charger 2, fit the Lifeline battery better than the Intelipower. Yet even then the Xantrex’s float voltage is 0.1 volt high.

This may be more technical than you want: I ended up buying two 60 amp Xantrex chargers and kept the Intellipower. I have one of the Xantrex chargers wired to the house batteries and the other to the chassis. I can then keep the RV in storage, plugged into shore power, without worrying about either battery. (It is very likely that your chassis battery is not charged by your charger, only by the engines alternator) I have added relays such that when I start the generator, both of the Xantrex chargers plus the intellipower charger, can charge the house batteries (180 amps total), IF I throw an enabling switch (I only use if batteries are discharged by 25% or more) and IF the air conditioner is not running (otherwise too much load for the generator).

PS one of the two Xantrex chargers I bought only appeared to be working correctly. Upon measuring it, the float voltage was nearly 0.5 volts higher than the specifications, After some run around with their support they sent me a new one. It works just fine. I do not know if this is a fluke with in Xantrex or chargers in general. But I suggest that if you buy one do not assume it is working as advertised just because the battery is charging and staying charged, Verify the voltage.

It seems to me that the manufactures of chargers, batteries, and RVs are too quick to use a “rule of thumb” for design considerations. The problem is that the use of several “rules of thumb” end up in an overal crappy design. Hence battery issues are no doubt the most common complaint or question about using an RV.

[nothermark]

FWIW for most people more than 12 hours of battery capacity is overkill and excess expense. It seems most people spend most of their time plugged in. The few that do not add a lot of stuff to boon dock like solar and more batteries. The rest do not need all that stuff.