Disappointed in new battery performance

[JimF]

Originally Posted by 360true

Jim.... We are full-time, and the residential big fridge allows us to stock up at Costco on meat, ice cream etc for a week or two at a time. Imagine having your smaller fridge at home. Mama might not be happy!

I don’t know what kind of refer you think we have but its darn near as large as our 26 cu ft fridge at home, its 4 door with ice maker and water dispenser in the door. We don’t use Costco we use the military commissary facilities and can stock up for a couple of weeks easy. If you haven’t seen it or know about it don’t knock it. We dropped out of full timing a couple of years back but the additional investment 8 years ago for a custom propane refer was worth it. Wouldn’t go back and trying to figure out how to put one in the house for those times of power outages which are frequent. The only down side is the price, about twice the cost of a residential refer.

[360true]

Jim... No need to get defensive or in a huff. Just explaining why we decided on a residential fridge. Different strokes.....

[B and B]

Originally Posted by 270S

Not sure if you are asking me or another poster - no quote this time - LOL.

BTW, I would adjust (change) some of those settings to the numbers I mentioned. Even though you "can", anything below apx 12.2Vdc recharge start point will shorten lifecycle of batteries. AGMs get 1000 cycles based on 50% discharge before recharge. If going down to the elevens , that number drops to 200-500 depending on how low, often, temperature, ...

I have had NO problem with my set up. Typically out hiking, ... til late afternoon if camping, return turn on AC & gen for an hour or so to cool down RV that has warmed up during the daytime, start cooking, showers, ... By quiet time (8pm) Gen is off, switch on inverter (batteries 100% topped off while Gen was on) and run Air Conditioning ALL NIGHT, watch TV , ... til decide to sleep for the evening, leave AC on. In the morning cook, .... Gen only if really needed otherwise I wait until the evening again to top off to 100%. If going to drive, the engine recharges all battery banks - my mod upgrade.

Aside from the convenience, .,... the MAIN Reason for the large battery bank and inverter is to NOT RUN an engine and go to sleep unless someone is awake monitoring it. Too many ways to get killed - everyone thins CO, but the real danger is FIRE! I've seen it too many times. It is a killer. There is usually no problem when you are plugged in, no engine is running.

How many batteries do you have to run AC all night?

[B and B]

Originally Posted by JimF

Wow, all this makes me very VERY GLAD we have the Propane/Electric refer. Set it on automatic and it cools on what ever is available and no problems. Think I’ll keep the residential refer in the house. IMHO.

I have the latest 18 cu ft Norcold. Never a problem as well. Something everyone should consider. Ours keeps the freezer cold as ice, ice cream is cold and the side of beef is frozen.

[babock]

Bottom line...you can't run a residential fridge on the batteries you have. Even if you had 200AH usable, you would be on the edge and you have less than that.

Either go with 6 batteries, or switch to 4 lithium and invest in solar.

[ScottBrownstein]

We need to go back to 360True's original question. I have a 335DS with the same reefer, I have measured the amperage over a long period of time under various temperature conditions. It averages 100 watts or about 8 amps...all the time. Unlike the OP, Forest River put 4 batteries in my coach and I can go nearly 24 hours without hurting the batteries. He can easily make it for 8 or 10 hours...he has two new batteries. If he is running the heat as well he might want to charge before bed...and charge right away in the morning and keep the thermostat kinda low. He can, however, do this without damaging his batteries.

[babock]

Originally Posted by ScottBrownstein

Modern residential refrigerators run ALL THE TIME! The power draw varies but they never draw zero since they have their own inverter powered compressors. My really big Frigidaire (French door with bottom freezer) will draw and average of 100 watts continuously through the inverter. So, 4 hours at 100 watts (about 8 amps) will pull 32 AH out of the bank. Your bank has a capacity of around 300 AH but only 150 to 50% discharge.

I think you are fine as others have said.

Voltage is a bad way to judge SOC.

If he is drawing 100W continuous, then that's 2400W in a 24 hour period. He has 150AH x 12V = 1800W!

[360true]

Thanks for the refocus. I too have 4 12 volt batteries. I am soon going to "test" by shutting off shore power and monitor until the output decreases to 12.0 volts. I will keep y'all posted! Thanks everyone.

[ScottBrownstein]

360True If you have a Xantrex like I do and can see the panel, it will display the wattage and battery voltage in real time on the panel.

[Flybob]

The kill-a-watt meter can measure the usage over time (KWHr)and if you have the correct model it will actually calculate the cost after entering the WHr cost for your service.

Originally Posted by ScottBrownstein

Maybe, but not for a modern reefer which has loads all over the map. Measure it in the low load state and you will be really happy...and then disappointed much later when you look at your SOC after more than a few hours.

Here is a long term measurement log for a big residential reefer:

[360true]

Scott: no I have a simple digital voltmeter wired in that shows current volts. The coach came with idiot lights only....

[ScottBrownstein]

Originally Posted by 360true

Scott: no I have a simple digital voltmeter wired in that shows current volts. The coach came with idiot lights only....

If your inverter is a Xantrex, there is a display on the inverter itself that alternates between wattage delivered and battery voltage sensed.

[360true]

Yes, I have a xantrex with display, but it is a pain to see.

[270S]

Originally Posted by B and B

How many batteries do you have to run AC all night?

Did you not start at page 1 of this thread? The whole thread was only 4 pages when you replied. It was there on the first page, post #5. With pictures too - woo! I only found this by accident, I unsubscribed.

[babock]

A 13k BTU AC will require around 120A. Assuming it's running 50% of the time over 8 hours, that would be close to 500AH. Pretty much not an option unless you have a bank of lithium batteries. Assuming the battery bank in post #5 are 200AH 6v batteries, that bank is a 400AH 12V bank so it would only last a short time.

[270S]

Originally Posted by babock

A 13k BTU AC will require around 120A. Assuming it's running 50% of the time over 8 hours, that would be close to 500AH. Pretty much not an option unless you have a bank of lithium batteries. Assuming the battery bank in post #5 are 200AH 6v batteries, that bank is a 400AH 12V bank so it would only last a short time.

You know what assume does, but not to me, I don't do that - just the facts and science. This happens to be my business and I actually know what I am doing.

In Florida heat, it will in fact consume apx 100-125Ah (many factors) during the initial cool down from an inside temp in the mid 90s, but after that it is not 50%, it is apx 12%. The compressor cycles on and off as needed apx 1/8 of the time originally needed for cool down. You may have missed the fact that the sun is no longer out adding to the heat factor warming the RV, just the internal heat generated and the residual OAT that is slowly lowering. Assuming one is starting this procedure at 8-10pm, it will consume in the following 8 hrs the same amount as it did during the initial cool down.

If one has an older RV with an older AC unit, it may consume more, but on the order of 20-30% higher. The marine units are even better and consume 50% less than that! Dometic manufactures both RV and marine, but the RV units are not even close to the quality I am used to dealing with in the marine world. I consume apx 200AH in my marine installations and 275-300 on the rv if the OAT is in the 80s or more. In the 70s, it obviously drops significantly to 135-185.

My 800 Ah battery bank using the parameters previously posted equates to 225Ah usable @ 35% [(800 * 80%) * 35%)]. If one were to routinely use 50% vs 35%, 320AH would be available, but I do not recommend such deep discharges on a regular basis.

That's the facts, no opinion here. No need to agree though, stay tied to a plug. Ignore that I have been doing this for over 20 years.

[270S]

Originally Posted by babock

A 13k BTU AC will require around 120A. Assuming it's running 50% of the time over 8 hours, that would be close to 500AH. Pretty much not an option unless you have a bank of lithium batteries. Assuming the battery bank in post #5 are 200AH 6v batteries, that bank is a 400AH 12V bank so it would only last a short time.

A 13k BTU AC will require 15-25 amps (not 120amps) at 120Vac to run depending on the OAT. On battery via inverter multiply that by 10-12 to get the DC amps required. After the cool down and constant high draw is over, the compressor will cycle and there is NO WAY to know how often during daytime (if it ever gets to "normal" indoor temps) heating, but after sunset, if it cools down outside, it drops to apx 15% run time. In our field tests, in the latter situation the total AH consumed over night will be apx 2-3 times the amount consumed in the first hour.

[babock]

Originally Posted by 270S

A 13k BTU AC will require 15-25 amps (not 120amps) at 120Vac to run depending on the OAT

120A at 12V is what I was saying. You really couldn't figure that out?

A 13K BTU AC draws 1250W.

So..you have 400AH 6V batteries?

I am a EE that worked on electric vehicles back when they started with lead acid batteries.

[270S]

Originally Posted by babock

120A at 12V is what I was saying. You really couldn't figure that out?

A 13K BTU AC draws 1250W.

So..you have 400AH 6V batteries?

I am a EE that worked on electric vehicles back when they started with lead acid batteries.

Yes, but I was trying to help those that may not have the education at their fingertips like some of us on this subject matter. The last thing we want to do is put out fake news, even if not intentional by accidental slip.

Yes, only because of the limited space available. 2groups of 6Vdc @ 400AH in series to make 12Vdc @ 400AH then paralleled together to make 12Vdc @ 800AH. In the marine environment, I use 6 2Vdc in series to make 900 or 1200 AH.

[360true]

270... And those of us who have skills other than electrical sure do appreciate the discussion and explanations that we have on this forum. Thanks to you all....