Dual deep cycle batteries not lasting through the night - is something wrong

[jmaher31]

Hi all,

Hoping to get some guidance here. I have a Rockwell Forest River pop-up trailer. I purchased two JITA deep cycle batteries hoping to be able to get enough power to last three nights, but, despite fully charging the batteries, they are dead after a single nights usage. I am only using lights and the small fridge. Is this normal? If not, any ideas how I can go about troubleshooting.

 

[Buly]

It is very simple math, but you must provide Amper hour battery capacity, and the fridge ampere hr draw. Plus extra for the lights. Than if you have some other appliances that you did not think of? We can not guess all the numbers.

 

[Richpatty]

Adding a BMK (battery monitoring kit) helps immensely when trying to watch battery capacity and usage.

 

[B52Bombardier1]

What you listed is quite a lot of amperage draw for almost any reasonably sized set of batteries. Especially if your lighting is all still using incandescent lamps - a change to LED would help but not solve your problem.

Rick

 

[jmaher31]

It is very simple math, but you must provide Amper hour battery capacity, and the fridge ampere hr draw. Plus extra for the lights. Than if you have some other appliances that you did not think of? We can not guess all the numbers.

Two 100amp hour batteries. I don't know what the fridge draws because I don't have access to it currently and can't find that information online. The manual just say 3 way fridge. We are only running lights and teh fridge on battery

 

[Bob K4TAX]

I changed to LED lights. For the relationship between incandescent bulbs and LED units, I measured the current of ONE incandescent bulb and the current of ONE LED unit. The difference is that ONE incandescent bulb draws 10 times the current of ONE LED unit. The equivalent light output was equal on both bulbs. The current draw of the incandescent bulb was about 1.2 amps. The current draw of one LED unit was 0.125 amps.

If you have a 3 way refrigerator, it should be running on LP and NOT DC. If on DC that unit will require between 8 and 12 amps per hour. A 100 aH deep cycle battery can be safely discharged to 50%. Thus two batteries will provide 100 aH of effective capacity. The refrigerator on this souce will deplete the capacity of thebatteries in about 10 to 12 hrs.

Solution: Change all lamps to LED and run the refrigerator on LP. That way you should have adequate battery capacity.

Bob

 

[jmaher31]

Thanks Bob. Will do.

 

[AbdRahim]

My class C had exactly the same setup. One night at a truck stop only using the vent fan and a few lights - fridge on propane, and batteries were down to 50% in the morning ( around 14 hours. Two batteries don't go very far.

 

[Bob K4TAX]

Estimate vent fan at 4 amps for 14 hrs = 56 amp/hours of available battery.
Estimate 5 lights a 1 amp each for 6 hrs = 30 amp/hrs of remaining battery capacity.
Estimate refrigerator control panel and LP valve at 25%/3 ah x 14 hrs = 10.5 aH of remaining battery capacity.

I can envision 2 x 100 aH batteries with a 50% discharge in the above estimates to be to the discharge limits at 96.5aH consumed of 100 aH available. The vent fan, just like the furnace, is a battery killer.

Bob

 

[WinMin4]

Not sure your battery size, I have 2 deep cycle batteries, group 27, that will last overnight easily on my Class C, then I run the generator daily for a short time to recharge them and phone. I replace the batteries every 2 years regardless and by good ones - don't go cheap especially if you like boondocking. $400 every 2 years not too bad. By the way never used LED, still using bulbs with my original 20 year unit.

 

[Bob K4TAX]

By changing from incandescent bulbs to LED bulbs, you will have the same amount of light, the same color of light, and reduce your current consumption for lighting from your batteries by 90%.

Bob

 

[gibsito]

Agree 100% with most of what was already said here. LEDs and leaving the fridge on propane is the way to go. If you really want to take the mystery out of what your electrical system is doing, wire in a good monitor that will tell you voltage, watt input and usage, etc. It eliminates all the guesswork.

Another consideration, for when your batteries get worn out is to switch from lead acid to LifePo4. A 100ah LifePo4 battery can be discharged 90% without excessive damage, as opposed to 50% for lead acid. That gives you effectively 80% more usage out of a single charge. Yes, LifePo4 is expensive - but they're touted to last 10 years and they weigh much less than lead acid so are easier to handle.

The most time I've ever gotten out of lead acid is 8 years, but more often less than that. I would never replace them on a two-year schedule though. You can tell when they're getting ready to be retired by how low the voltage is drawn down, even with relatively light loads. I'm at almost 8 years on my two lead acid batteries now and, although they are getting weaker, they still work and don't leave me without power. They've been well maintained, getting fully recharged daily (on solar) and water level checked regularly.

But I'll be going with LifePo4 next time.