Batteries

The Wanderer2 · 05-26-2019, 02:32 AM

How long can I run the refrigerator in storage before the batteries need charging?

formerFR · 05-26-2019, 06:06 AM

there's no way to know for sure, even if someone has you same exact coach, batteries, and fridge - there are too many variables, though for a new coach, you might expect 24hrs IF the setting is on low, the fridge is already cold when you begin the 'time frame' you refer to, the outside weather is not hot, and there are not many items in the fridge.

Your battery levels and their condition will be a great determination. Your inverter will also be using some power even while it 'waits' for the fridge's compressor to run, and several items in your coach will continue to 'use' power from the batteries, even though you may not realize it, especially since you won't have the 'Use/Store' switch in the store mode.

If you have a Magnum Inverter, and ME-RC remote panel to control it, you can use it's 'SEARCH WATTS' setting, to minimize the Inverter's power usage when the fridge is not actually 'running', giving you a little more time as well.
The SEARCH WATTS function tells the inverter to 'sleep' while it waits for 120v items that require power. When the fridge's compressor needs to come on, it 'wakes up' the Inverter.
My Search Watts setting is set to 50 watts, the maximum.

tomkatb · 05-26-2019, 06:41 AM

Too many variables.

P=IV.

Find the wattage of the refrigerator. Divide by 12.5. Take that number and add 15%. That is the amps used per hour.

Then find the amp rating of the battery bank. Divide that by the number above.

That is the minimum number of hours the fridge will run. Depends a lot on the temperature in the coach. Efficiency of the unit. Worst case.

Will be hours not days. Residential fridges not do well on batteries.

Battery powered cars have the same problem today as they had at the turn of the century, 1900. Storage capacity.

dan-nickie · 05-26-2019, 06:45 AM

On my Berkshire, With nothing else much running besides the refrigerator about 8 hours based on my tests.
That pulled the battery down to about 12.0 or 12.1 volts which is time to recharge.

formerFR · 05-26-2019, 06:59 AM

while TOMKATB hits on many of the 'technical' aspects, and you can certainly go thru those calculations, if you wish, the reality is that you really won't know, until you 'know', by trying it. Worst case scenario is that your inverter cuts off due to low battery power, and your fridge does not kick on, usually near the point when you return the next day anyway. A fridge is a big COOLER, so a few hours without 'power' is not necessarily going to cause sudden 'loss' of all of your fridge items.

Some with older battery banks, and higher outside temps, may only get 4-6hrs before the fridge is without power. Others with new battery banks, and lower temps, might get 24.
Who knows.

Mine is running on the inverter right now, while parked uptown, after arriving at 9:45 last night - we left it parked, with the inverter on, and when I return this morning, around 9am, I expect that the fridge will still be cool, the inverter may have shut off, or not, but I am not in the least worried about it, and I have ice cream in the freezer. : )

When I left it last night, I simply turned off most everything except the fridge, left the Inverter's LBCO(low battery cut off) setting at 11.5 volts, turned the fridge's setting from 5(High) to about 2(lower), and walked away.

Now, if I were not coming back to the coach as early in the day, or had left the coach in 'storage' for several days, but wanting to keep the fridge on cool, I would have put the Inverter in 'SEARCH WATTS' mode, which basically tells the Inverter to 'sleep' until the fridge's compressor needs to kick on, then waking the Inverter up to power it for 10 minutes or so, then back to sleep. This saves a little battery power while the Inverter isn't required to be 'awake' all the time when the fridge doesn't need to be running.

FUN!!!! (or, if you are really concerned, you can ENABLE your AGS to start your generator and recharge your battery bank when it needs it!)

The Wanderer2 · 05-26-2019, 07:27 AM

Thanks for the information. Just as I thought the batteries wouldn't last more than a day without charging. I'm new to some of the Berkshires electronics. The reason I ask, I'm trying to learn the ins and outs of the system before we go west to Seattle in August. We're going on an Alaska cruise for a week and the motorhome will be in storage during that time. I found a place that has storage with only extension cord plug in for power. I only want to maintain the batteries and the frig. while gone. I'll try to limit what's left in the frig. during this period.

dan-nickie · 05-26-2019, 07:28 AM

Since your question was about the coach in 'storage', I assume you're talking about leaving it un attended for more than one day. Can't be done.

dan-nickie · 05-26-2019, 07:31 AM

Quote:

Originally Posted by The Wanderer2

Thanks for the information. Just as I thought the batteries wouldn't last more than a day without charging. I'm new to some of the Berkshires electronics. The reason I ask, I'm trying to learn the ins and outs of the system before we go west to Seattle in August. We're going on an Alaska cruise for a week and the motorhome will be in storage during that time. I found a place that has storage with only extension cord plug in for power. I only want to maintain the batteries and the frig. while gone. I'll try to limit what's left in the frig. during this period.

From experience, I can tell you that plugging in to A120 volt at storage is a gamble if other motor homes are connected to the same breaker panel.
The motor home next to mine tried to run their air conditioner and blew the breaker which caused mine to lose power. After about a week The stuff in our fridge was pretty rank smelling.

The Wanderer2 · 05-26-2019, 07:48 AM

I guess I really need to limit what's in the refrigerator. I've did some research and this place is recommended by other RVers who have taken the Alasken cruise out of Seattle. I will need to shut the coach batteries off and the inverter to off and hope the 120AC works.

dan-nickie · 05-26-2019, 08:43 AM

Good luck. And have a fun trip.

L2RV · 05-27-2019, 01:49 AM

If you are staying at Lake Pleasant RV Resort in Bothell WA and storing your Motorhome in their Cruise RV Storage Area while you are on the cruise your coach will be hooked up to electricity so you will not need to worry about your batteries. All spaces in their RV Storage Area for people going on Cruises have electricity so your refrigerator will be good.
We will be going on an Alaskan cruise in August also and have booked reservations at this resort in their RV Cruise Storage area. They told us we will need to bring a 75' 110v extension cord to use while in storage area.

L2RV · 05-27-2019, 01:52 AM

If you are staying at Lake Pleasant RV Resort in Bothell WA and storing your Motorhome in their Cruise RV Storage Area while you are on the cruise your coach will be hooked up to electricity so you will not need to worry about your batteries. All spaces in their RV Storage Area for people going on Cruises have electricity so your refrigerator will be good.
We will be going on an Alaskan cruise in August also and have booked reservations at this resort in their RV Cruise Storage area. They told us we will need to bring a 75' 110v extension cord to use while in storage area.

The Wanderer2 · 05-27-2019, 05:44 AM

Wow, small world, that's the same place we are storing the RV at. Even though I come from a long boating background with similar systems the Berkshires electrical system is more complex. So I might be asking some stupid questions in my attempt to learn about my Berkshire.

FFred · 05-27-2019, 06:05 AM

"That pulled the battery down to about 12.0 or 12.1 volts which is time to recharge."

Voltage is a really inaccurate measure of battery capacity.

A temperature scaled hydrometer will give accurate results for SOC.

jeff64 · 05-27-2019, 06:31 AM

Quote:

Originally Posted by FFred

"That pulled the battery down to about 12.0 or 12.1 volts which is time to recharge."

Voltage is a really inaccurate measure of battery capacity.

A temperature scaled hydrometer will give accurate results for SOC.

You can get an optical hydrometer from amazon for around $25. I got mine back in the 70's in school. When using charge battery well before test. Specific gravity of each cell should be within .1 of each other if all is good. 1.250 full charge . If you are within .3 or better the battery is on it's last legs.

Oscarvan · 05-27-2019, 09:31 AM

Quote:

Originally Posted by FFred

"That pulled the battery down to about 12.0 or 12.1 volts which is time to recharge."

Voltage is a really inaccurate measure of battery capacity.

A temperature scaled hydrometer will give accurate results for SOC.

A battery condition monitor is even better, and a lot less messy.

DogFather · 05-27-2019, 11:51 AM

Thanks for the tip about the SEARCH WATTS function - good to know.

But it raises a question in my mind: If there's no 120V present at the fridge during the sleep mode (assume the fridge is functioning as an unpowered insulated box), how does the fridge signal the inverter that it needs power to run the compressor?

*Just found the answer - The inverter isn't always off. It comes on with periodic pulses and checks for a qualifying load. If found, it stays on until the load goes away.

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