House Batteries Dead?

[BillT]

Hi Everyone!

I'm not even sure if I have a problem.

My new Challenger 37 TB seems to kill the charge on the house batteries (4 6volt) when I park it for more than a couple of days. I'm wondering if it's my fault. When I store it I:

1. Turn off inverter
2. Turn off house batteries

Is there something else I should be doing or possibly screwing up?

How long should the house batteries last for in the state I leave it?

Thanks all,

Bill

[EA37TS]

Bill,

With no load they should last more than a couple of days.

Last week I turned off my breaker and disconnected shore power from the coach so I could cut the grass between the coach and the house. When finished I plugged back in and went about my business. Four days later I went out to the coach and even though the AC was sent at 75 the thermostats were reading 79. I started fiddling around and turned on the inverter and my batteries were reading 11.2 volts. I fired up the generator and started doing some additional checking and low and behold, I forgot to turn the breaker on after I plugged the coach back into its shore power receptacle.

I only have 2 6 volt batteries and only dropped to 11.2 Volts in 4 days. With 4 batteries you should be lasting longer than a couple of days especially with the house batteries in store mode.

[KNMIB]

My house battery use to last for a month with all turned off, this year they would only hold for a day or two so I had to replace the junk Harris batteries with Interstate. With that said the Harris batteries where 3 years old but where never used much until we bought the unit.

[Yosemitebob]

Charge your batteries up again, then turn everything off, then.....use a meter and check your load on the batteries, something is amiss here. You do know your Use/Store button doesn't really turn everything off right? Check with a meter.

[Lloyd]

Originally Posted by dstankov

Bill,

With no load they should last more than a couple of days.

Last week I turned off my breaker and disconnected shore power from the coach so I could cut the grass between the coach and the house. When finished I plugged back in and went about my business. Four days later I went out to the coach and even though the AC was sent at 75 the thermostats were reading 79. I started fiddling around and turned on the inverter and my batteries were reading 11.2 volts. I fired up the generator and started doing some additional checking and low and behold, I forgot to turn the breaker on after I plugged the coach back into its shore power receptacle.

I only have 2 6 volt batteries and only dropped to 11.2 Volts in 4 days. With 4 batteries you should be lasting longer than a couple of days especially with the house batteries in store mode.

11.2 volts is considered dead batteries. 11.8 volts is 50% discharge, which is considered dead batteries.

[BillT]

Originally Posted by Yosemitebob

Charge your batteries up again, then turn everything off, then.....use a meter and check your load on the batteries, something is amiss here. You do know your Use/Store button doesn't really turn everything off right? Check with a meter.

Ok, so I'm learning some stuff here. So 11.8 is 50%, which means that if 11.2 is dead then about 12.4% is full charge. Correct? Will the display on my inverter tell me this? I think I remember my inverter display reading higher than 12.4% though. What gives?

Also, how do I check and with with what kind of meter?

Bill

[EA37TS]

Determining the state of charge on a battery is a little more complicated than just a measurement of voltage.

Here is a good article which explains the concept and how to test the state of charge with the particular power loads in your coach.

Understanding Battery Voltages and State of Charge - Roadtreking : The RV Lifestyle Blog

[tenbear]

Here is another good reference, The 12 volt side of life.

Can't get the link to work so just Google "12 volt side of life".


To find out if your battery still has a load on it a Clamp-on Ammeter is a usefull tool, but make sure you get one that measures both AC and DC current. Here is a link to a meter that Sears sells.
Sears.com

Of course, you could just disconnect the battery, negative lead, and see if the battery still dies.

[Yosemitebob]

Battery standing (0 amps for 6 hours or more)
90% full (a standard charging system will not charge 100%) 12.7v
80% 12.5
60% 12.2
40% 11.9
20% 11.6
0% (empty) 11.4
empty is also irrealvent as empty while discharging (depends on amps and temp) can be 10.5 - 11.5


Some other helpful figures:
Battery full with light loads (depends on amps drawing) 12.4-12.7
Battery full with heavy loads (depending on amps drawing) 11.5-12.5


Have you checked the converter/charger to make sure it is charging properly, water level in battery?


It seems you have a drain somewhere, a rather large one, so should be easy to find at least. You need a meter, they come pretty cheap now-a-days and should be part of your toos set anyway. After charging your battery full as you can, with the system off (store) then you start testing the battery and circuits and one place to start is your 12v fuses at your panel. But first take a measure at the battery write it down. One or two hours later take another measurement write it down, if it is losing voltage, test the cells, I saw it mentioned in one of the above clips. If the cells are testing good, then go to the panel and start there.


Don't forget to check all your connections, they can sometimes delvelop excessive resistance (if loose) and this causes loss of capacity as well.

[KNMIB]

Which meter do you use I have had bad meters (probably to cheap)LOL

[Yosemitebob]

I use a $15.00 meter I got from Home Depot, test it on a known when you get it is all. This is what I have, it works fine.


Compare
Digital Multimeter
<img src="http://www.homedepot.com/catalog/productImages/145/7c/7ca247e9-4210-4f3e-be1e-9d4263f8f4f4_145.jpg" alt="Digital Multimeter" height="145" width="145"/>


Model # MT-1210

$15.45 / piece