Batteries Loosing Charge Fast

[stppinz]

Just spent 5 days and 4 nights in our new(old) MH. Everything was great except for the power. After 2 days and one night there wasn't even enough power to turn over the generater. I ended up jumping the coach battery with the truck battery (not sure if that is bad but we were in a pinch) and that would turn over the generater every time. The coach battery is brand new.

But after leaving the generater on for a hour or so we had power for the day/evening, but when we woke up it was dead again.

My two assumptions/observations were - 1. I just didn't run the generater enough to fully charge the batteries, and 2. I let the kids watch their DVD's (one small DVD player with 2 small screens) on a 12 Volt outlet that is labeled TV ONLY which suprised me when it drained the batteries.

So my questions are -

1. After having low/dead coach batteries how long with the generater does it take to recharge in general. I know this will differ depending on size and everything, but am I looking at running it all day??

2. Running on the coach battery, is it smart to only run the lights and other small RV stuff and not plug anything else in? I was just suprised how fast the coach battery drained. I was also suprised that running that small DVD player for one movie drained the whole system.

I am just trying to get a handle on all of this. Is any of this sound abnormal or do I just need to be more leaniate on using 12V power?

Thanks for the input.

 

[fredethomas]

How many batteries and what kind do you have.  Two days without charging is quite a long time for any system.  Better to run the genset for an hour or two morning and night.  The DC usage also depends on the type of RV and things like the heater, refrigeration etc.

 

[Carl L]

Old coach?  Possibly old batteries -- they are usually good only for about 5-6 years.  Even if new they may have been those cockamammy dual purpose marine units.  You want pure deep cycle units.

When you took those batteries to zero, you destroyed some 20-30% of their rated output that happens everytime you take them to full discharge.  And of course you may not have enough units for the load.  What is installed?

 

[John From Detroit]

WOW. I'd love to get 2 days out of one charge..

Recharge time: Maximum recommended charge rate is around 1/3 (actually 30%) of amp hour capacity so assuming you have the proper converter for that task, it takes at least 2 hours to get em to 90 percent from 1/2 down (Recommended limit) you were beyond that so figure 3 hours to reach 90 percent, another 4 to finish charging.

 

[rsalhus]

The coach battery is brand new.

Sounds like you only have one coach battery.  Let's say that it is a 105 AH lead acid battery.  If you discharge it to 0% SOC (which you should never do, as noted above by Carl L), you will need to replace roughly 84 AH of power to get the battery to 80% SOC.   

To estimate the recharge time required to do that, you have to divide 84 by the result of multiplying 0.7 times your maximum charge rate (this would be 21 if you have a 30 AMP charger, .7 * 30 = 21).  So you would need to charge the battery 4 hours (84 / 21 = 4) to get it back to 80% SOC.  Now this is just a rough estimate, but this method of computing your recharge time should give you an idea of what to expect.

 

[stppinz]

Thanks for all the good info guys. I hope I didn't hose the battery to bad. I am pretty sure that the battery is a deep cycle. I had Blane Jensen RV and Camperworld put it in when they worked on the generater.

I didn't think that I needed to charge that often because there isn't really anything running on the system. The fridge, water heater and everything else is propane, but I did just notice that for some reason the radio is wired with to the coach battery and is always on. but other than that nothing is running off that system. I guess the water pump is running off of the coach battery. Other than that it is just the lights. But I guess the system wasn't properly charged...I guess I will just have to run the generater more than expected.

 

[Carl L]

Thanks for all the good info guys. I hope I didn't hose the battery to bad. I am pretty sure that the battery is a deep cycle. I had Blane Jensen RV and Camperworld put it in when they worked on the generater.

I didn't think that I needed to charge that often because there isn't really anything running on the system. The fridge, water heater and everything else is propane, but I did just notice that for some reason the radio is wired with to the coach battery and is always on. but other than that nothing is running off that system. I guess the water pump is running off of the coach battery. Other than that it is just the lights. But I guess the system wasn't properly charged...I guess I will just have to run the generater more than expected.

One battery, eh.  Well the water pump, the fridge control board, your propane alarm, your lights, the stereo, vent fans, and the furnace fan all run off the battery.  As others have implied, you were doing good to get thru one night much less two.  My rig has two AGM deep cycles and solar.  Nevertheless, very careful use, including turning the furnance way down is needed to get us thru the night comfortably.

See if you can stuff another battery in there but do so when you replace the current one -- batteries have to go in matched pairs.

 

[stppinz]

Thanks! This all is helping a lot. I am going to get the battery tested to see how bad it really is and then look into adding another one. Not much room under the hood. Maybe a couple of gel batteries inside somewhere...

 

[John From Detroit]

I have often asked what kind of tests the places that test run...

Link to Harbor Freight

Is the tester  I trust

 

[NCsleeves]

See if you can stuff another battery in there but do so when you replace the current one -- batteries have to go in matched pairs.

Carl, I hadn't heard about having to replace coach batteries en masse.  Good to know...  we have four, two different vintages...  we were thinking we'd replace the two older ones.  Sounds like more research is in order.

 

[Ron]

I would never consider replacing just one battery in a bamk of batteries.  All should be replaced at the same time.

 

[Gary RV_Wizard]

A good tech can verify whether some of the batteries are good enough to work adequately with new ones, but peoplke with that knowledge and tools are hard to find and the cost of the test may be as much as a new battery anyway. It is safest to replace them all.

Having said that, I have on at least two occasions discarded a failed battery from a set and inserted one new one, with no problems.