Battery draining question
I'm pretty new to RVing. We have been inveterate tent campers, but last fall purchased a used '07 (or '05 - somewhere around there) hybrid travel trailer (Jayco JayFeather 19-H) so I'm pretty new to many issues. Also, we typically look for more out-of-the way campgrounds and sites within campgrounds, so we are not likely to have an electrical hookup available.
We took the camper on a several day shakedown trip last fall and the only issue we had was that the battery drained down unexpectedly rapidly - resulting in a middle-of-the-night screeching alarm when the voltage to the lp detector got too low. This was unexpected because we had been very frugal with our energy usage to begin with. I recharged the battery by plugging back in to the towing hookup and letting our vehicle run for about an hour - probably got it up over 12 volts, but again it didn't even last a day. I can't remember if we had the fridge on, but we literally used nothing else after that except the occasional pump.
It could have been something unexpectedly drawing current, or just a bad battery (no idea how old the battery was - though it looked fairly new), so I figured I would just work out the details this summer.
This year I got a new battery (NAPA Premium Marine/RV Deep Cycle) with RC rating of 130. On our big camping trip this summer, everything seemed to be working fine. I had the fridge on and again we used minimal water pumping and even more minimal lighting (we have lots of LED lanterns). I didn't measure the voltage every day, but the idiot lights (good/fair/poor) indicated that the the battery was doing fine. One morning after about 6 days, we noticed that our fridge had turned off during the night. Propane was fine, but it was clear that the battery was too low (pump, and lights weren't working, but thankfully the LP alarm hadn't gone off). Battery idiot light now indicated poor. Checked voltage on the battery and it was at 8V.
I'm not sure how much juice the fridge draws just to be running on propane, but I figured that a week was probably a fair amount of time for a good battery to power minimal loads without needing to be recharged. So, I plugged in ran our vehicle again for an hour or two and charged the battery up to over 12V, which I figured should easily last us for the remaining 3 or 4 days we were planning to be there. After less than 24 hours though, the battery had dropped back to about 8V. There is one switch that is an override for all the cabin lights, and I noticed that it had been left on - so even though we were not using any lights, I thought there might be a phantom load that might be drawing juice. After that, I made sure that switch was off and I also pulled all the fuses except for the ones governing the fridge and the water pump (those two fuses also covers a few other auxiliary things). I charged the battery up to about 12V again, but by the next day it was again down to about 9V.
I'm no expert on batteries, but my limited understanding is that charging is non-linear; The first 80% or so is easy to charge and as the battery gets close to full, it gets harder and harder. Thus, when charging an electric car for example, you can get up to 80% relatively quickly, but getting all the way to 100% takes a lot longer. However, I thought that (assuming the battery is OK) the loss in voltage during use should be roughly linear under a constant load.
Unfortunately, I don't currently have a DC ammeter (though I think I will get one) to measure the current draw and isolate the problem (if there is one).
Does this sound normal? Am I mistaken about how the battery is supposed to work? Do I always need to charge it back to full when recharging? I'm not worried about shortening battery life by not always recharging to 100%, but I thought it should still work fine if not fully charged (especially on the very first recharge).
Once I get my DC ammeter, I can probably find out if there is an unexpected draw, and exactly how much the fridge draws. However, maybe a battery expert out there can tell me if this is actually the expected behavior and if so, why.
Thanks.
-J
We took the camper on a several day shakedown trip last fall and the only issue we had was that the battery drained down unexpectedly rapidly - resulting in a middle-of-the-night screeching alarm when the voltage to the lp detector got too low. This was unexpected because we had been very frugal with our energy usage to begin with. I recharged the battery by plugging back in to the towing hookup and letting our vehicle run for about an hour - probably got it up over 12 volts, but again it didn't even last a day. I can't remember if we had the fridge on, but we literally used nothing else after that except the occasional pump.
It could have been something unexpectedly drawing current, or just a bad battery (no idea how old the battery was - though it looked fairly new), so I figured I would just work out the details this summer.
This year I got a new battery (NAPA Premium Marine/RV Deep Cycle) with RC rating of 130. On our big camping trip this summer, everything seemed to be working fine. I had the fridge on and again we used minimal water pumping and even more minimal lighting (we have lots of LED lanterns). I didn't measure the voltage every day, but the idiot lights (good/fair/poor) indicated that the the battery was doing fine. One morning after about 6 days, we noticed that our fridge had turned off during the night. Propane was fine, but it was clear that the battery was too low (pump, and lights weren't working, but thankfully the LP alarm hadn't gone off). Battery idiot light now indicated poor. Checked voltage on the battery and it was at 8V.
I'm not sure how much juice the fridge draws just to be running on propane, but I figured that a week was probably a fair amount of time for a good battery to power minimal loads without needing to be recharged. So, I plugged in ran our vehicle again for an hour or two and charged the battery up to over 12V, which I figured should easily last us for the remaining 3 or 4 days we were planning to be there. After less than 24 hours though, the battery had dropped back to about 8V. There is one switch that is an override for all the cabin lights, and I noticed that it had been left on - so even though we were not using any lights, I thought there might be a phantom load that might be drawing juice. After that, I made sure that switch was off and I also pulled all the fuses except for the ones governing the fridge and the water pump (those two fuses also covers a few other auxiliary things). I charged the battery up to about 12V again, but by the next day it was again down to about 9V.
I'm no expert on batteries, but my limited understanding is that charging is non-linear; The first 80% or so is easy to charge and as the battery gets close to full, it gets harder and harder. Thus, when charging an electric car for example, you can get up to 80% relatively quickly, but getting all the way to 100% takes a lot longer. However, I thought that (assuming the battery is OK) the loss in voltage during use should be roughly linear under a constant load.
Unfortunately, I don't currently have a DC ammeter (though I think I will get one) to measure the current draw and isolate the problem (if there is one).
Does this sound normal? Am I mistaken about how the battery is supposed to work? Do I always need to charge it back to full when recharging? I'm not worried about shortening battery life by not always recharging to 100%, but I thought it should still work fine if not fully charged (especially on the very first recharge).
Once I get my DC ammeter, I can probably find out if there is an unexpected draw, and exactly how much the fridge draws. However, maybe a battery expert out there can tell me if this is actually the expected behavior and if so, why.
Thanks.
-J
