Expected house battery life

C

Cmjansen

Member
Joined
Jan 23, 2017
Messages
20
Fluid Motion Model
C-242 C
Non-Fluid Motion Model
Ranger R23
Vessel Name
Coddiwomple
I can only get 1 day off my house batteries on my R23 before my low battery alarm goes off. The only load connected is the fridge. Is this normal? The 36' bayliner next to me on the dock this weekend has two house batteries of the same AH and he usually gets 3 days before he has to charge.
 
What cooling level is the Refrig set at ? If it's 3 or less it certainly should not drain the house battery at all within a day.

Are you on shore power, and if so presumably there's no issue as your batteries should be on a charge.

Make sure every else besides the Refig is turned off.

Do you have solar panel setup correctly.

Are you on the hook or moored at a Marina with or without shore power connected ?
 
The refrigerator is at 2. We are at Conover cove so no shore power. I ran my main engine for 25min this morning to recharge my batteries. By 2pm my low battery alarm went off - 10.4v. I ran my engine for another 45 min. House batteries were at 12.8v. After a couple hours battery at 11.2v. A manual would be nice. Do the batteries charge with the engine on or do you have to switch the inverter on which allows you to turn on the "battery charger" circuit
 
How many total amp hours do you have for the house in the R23? If your fridge is the only thing running it should only draw around 2 - 2.5 amps on average. With everything else taking about 0.5 amps you should draw only around 2.5 amps total or about 25 amp hours over ten hours. Even at a 5 amp draw you would only use 50 amp hours in 10 hours.

Your inverter should be off. The engine will charge without the inverter/battery charger on. If your inverter is on that would explain the use of amp hours.

Do you have a solar panel?

Curt
 
A 25 minute charge is likely only putting a surface charge on the batteries. the fridge can draw 4amps. averages around 3amps.

also remember the voltage shown on the battery is also whilst its under load (from that fridge) for a true state of charge you need to have no load on the batteries.

there is a chance they are toast but I suspect they are either not fully charged to start off with or you have more draw than you think

what age are the batteries?
 
This is a new R23 (Feb 2017). The 2 house batteries are 890AH each (1780total). No solar panel.

I was woken up again last night at 1am by the low voltage alarm again. This is after running my engine a second time for 45min (6:30pm). The Garmin indicated a charge of 12.7 volts when the engine was shut off. The only load was the fridge which was set at 2.

This became the topic of discussion on the dock this morning.
 
measuring voltage is a pretty crude measurement of SOC.
only real way to determine the state of the batteries is to pull them off the boat and perform a proper load test.

to get a better sense of whats happening you could try one of these http://www.balmar.net/products/smartgauge-battery-monitor/ which gets excellent reviews and doesnt need shunts installed. its very clever technology and easy to install.

as you mention you are on a non powered mooring with no solar, there is a remote chance that in the past you could have damaged the batteries by accidentally discharging them too far. if that happens their capacity and life is severely impacted. again the best way to determine this is a load test. it would produce the symptoms you describe.

you may also have a parasitic load on the batteries you are not aware of as well due to a miswire, product failure, or something accidentally being left on. Might be worth exploring what other systems could be causing an issue. for instance the propane solenoid I recently read on tugnuts can draw 1 amp when on which surprised me!
 
cmjansen,

You mention that your 2 house batteries are rated at 890 Amp-Hours each. I am not familiar with the batteries installed in the R23, but this extremely high rating sounds quite a bit unlikely.

I've used deep-cycle batteries in 2 different Ranger Tugs and 2 different diesel pusher motorhomes over the past 17 years. I've never run across any group 31 deep-cycle 12V battery with this large of a rating. For 12V Group 31 deep-cycle batteries, the ratings are typically in the range of 95-125 Amp-Hours. Group 31 batteries are the size that I have seen in the R27 and R31, although I'm not sure what is in the R23.

It is worth checking the actual Amp-Hour rating of your batteries. I suspect it is more than likely that you have 110 Amp-Hour Group 31 deep-cycle batteries x2. Then, the capacity is 220 Amp-Hours. You should never discharge them below about 50%, so the usable Amp-Hours is about 110 Amp-Hours. If you have an average load of, let's say 5 Amps, then in 20 hours you are discharged by 100 Amp-Hours (5Amps x 20 hours) and almost at the 50% limit.

If you discharge the batteries very many times much below that limit, then the batteries will wear out very quickly. Also, if you do not fully charge the batteries after a deep discharge, that also will wear out the batteries very quickly. I would guess that running your engine for 45 minutes after a deep discharge will not fully charge them, even though you might get a surface charge of 12.7 volts. Repeated lack of a full charge (that is, just a surface charge) will eventually cause severe sulfation of the batteries and failure.
 
I question the usefulness of those smart monitors like the balmar for the following reasons.

While the unit properly measures the SOC it will not necessarily reflect the capacity which is more important to me. Lets take an analog to this. Take a 1 Gallon water bottle, i can fill it with one gallon and measure the state of charge at 100 percent. If I squish the water bottle, I can fill it also to 100% but there is not 1 Gallon of water in it. That is what SOC tells you, assuming a healthy "unsquished" battery.

I have had batteries in my car that analyzed by several tools claimed to be 100% full but just did not have capacity when putting a real load on.

Even the Coulomb counters may not give you accurate info. They count the amp hours going into the battery, but they do not tell you if the energy gets stored or perhaps wasted as heat or used to split water into H and O.

Bottom line, you need to perform several tests to assure the battery has the capacity as assumed, and then SOC will be relevant.

In a boat or RV, I still would want to know what the current consumption is to find any loads that should not be on, in addition to the SOC. Whether I count the consumption or charge is another matter. But AH consumed or added, along WITH SOC should give you a pretty good picture of how well your battery is doing.
 
the tech in the Balmar doesnt operate the same way as counting passing amps and doesnt assume a knowledge of current battery state and health. it figures that out in the shape of the discharge curve thats matched to known curves for battery types. its very clever.

its really worth reading the article linked below on how the Balmar works. this is not the same as the Victron style systems.

to the original poster; I think Dale is on the money with the diagnosis.
 
We always use more amp hours than we think. In a 24 hour period the refrigerator could use 60 amp hours alone. Add plugged in devices like cell phones and ipads and then a few lights, the fusion radio and then the background items that are on all the time and it adds up. Running your engine for 45 minutes, as Dale said, is only giving you a surface charge. It may look good initially, but give it a one hour rest and take a look at your voltage to get your actual. I do not have sophisticated equipment, but use this as my guide. If you have no solar panel it won't take long to reduce your SOC significantly.

Voltage State of Charge
12.6+ 100%
12.5  90%
12.42 80%
12.32 70%
12.20 60%
12.06 50%
11.9  40%
11.75 30%
11.58 20%
11.31 10%
10.5  0%
 
I am not disputing the accuracy of the balmar, just saying that as a user of electricity I am interested in the remaining Ah not SoC which is in percent. If it shows me 70% soc. I don't know how many Ah I got left because I don't know what 100% is

Capacity of a batteries change based on model, age and damage to it from wrong operation. I had once a car battery that was identified as 100% SoC but it would not start the engine. Testing it with a discharged showed it had 7Ah of capacity but it was at 100% SoC. Soc is like a dipstick into a container, it unless you know the container size it won't tell how much liquid is left in it
 
stwendl":ll6ubfu4 said:
I am not disputing the accuracy of the balmar, just saying that as a user of electricity I am interested in the remaining Ah not SoC which is in percent. If it shows me 70% soc. I don't know how many Ah I got left because I don't know what 100% is

Capacity of a batteries change based on model, age and damage to it from wrong operation. I had once a car battery that was identified as 100% SoC but it would not start the engine. Testing it with a discharged showed it had 7Ah of capacity but it was at 100% SoC. Soc is like a dipstick into a container, it unless you know the container size it won't tell how much liquid is left in it
Click to expand...

Maybe the instrument indicating SOC was not functioning properly. That is why I like the imperfect voltage method and with flooded batteries checking the specific gravity is a good indicator as well. It is always important to turn all you loads off and wait about an hour to get your true voltage.

The reality is anything you read on a meter only indicates where you are at that moment. Knowing your initial amp hour capacity and what you will consume at a specific interval should let you know where your state of charge should be when you check it. When you compare the two and if you are off significantly it is time to figure out if you have a bad battery or a parasitic draw. A bad battery can be figured out with a load test. If that checks out okay the n you are in for the long haul trying to figure out what the culprit is.

As an example, I know that after a night on the hook my voltage should read about 12.42, 80% SOC. If I see a discrepancy from the norm regularly I start to get concerned if I can't quantify why. On a couple of instances the good old fashioned hydrometer indicated a couple of week cells. Off to Walmart for my $90.00 flooded batteries.
 
It sounds like you may be confusing the specs on your battery. The 890 is likely the CCA(cold cranking amps). Amp Hour capacity is more likely around 100. I quickly looked up group 31 specs on a lead acid and optima type battery and the amp hour capacities were 105 AH and 75 AH respectively.

For sake of argument lets say your fridge is pulling 3 amps and running 50 percent of the time. In a 24 hour period that's 3x12=36 amp hours used. Don't know which brand of outboard you have on your boat but the max sized alternator on most is 60amp. Theoretically a 60 amp alternator has to run at full capacity for 36 minutes to replace the power used per above. However, life isn't perfect. For one thing, the alternator isn't putting out full capacity at idle speed. Secondly, as the battery charges it absorbs charge slower and slower. Third, you're likely using more power in addition to the fridge than you realize. So if you're idling the outboard for 45 minutes per day it is highly unlikely that you are adequately recharging the batteries. When on the hook we typically have the fridge, Webasto heater, and a laptop running. We run the engine(more or less) for 20 minutes every six hours. I use the same simple guidelines described by knotflying. With no/minimal load if the batteries drop to 12.3V I crank the engine and run it for a bit.

Another thing to be aware of is that every time a lead acid battery is pulled below 12.3 volts it is being damaged(i.e.capacity is being permanently reduced). And the longer it remains in a low state of charge, the more permanent damage it sustains. Doing a bit of internet research on 12V batteries might be useful for future reference.
 
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