Are my 2 yr Old Batteries Healthy?

[Dcsqatar]

I am concerned about my 2020 (26 mth old) R29S battery health and was looking for some insight. For the first two summer seasons I was able to count on the inverter to make a few 4 cup pots of coffee and power the microwave for say 2 mins a day, for at least 3 days on anchor with standard issue solar cells providing some makeup. This summer, I get low voltage errors on my inverter after just 1 pot of coffee, suggesting loss of house battery power, despite being only 2 years old. I realize I could pull the house batteries out and load test them, but I have read that a load test is not definitive and pulling the batteries out is not easy!

Instead, I did a practical sort of load test which involved opening the 110V breaker and running the microwave for 3 minutes while watching the battery voltage. Before opening the breaker, the inverter/charger showed "FUL" and voltage was 13.6 - 13.8v via the panel/needle gage on the 3 battery banks. With AC power off, inverter showed 13.3v but dropped to 12.9v within 10 minutes with no AC loads. Is that drop normal or suggest a problem? Voltage as shown on inverter dropped to 12.1v immediately when microwave was turned on, and settled in at 11.8v where it stayed until microwave finished (after 3 mins). Once microwave finished, inverter voltage recovered to 12.8v which was the same voltage shown for all 3 battery banks via the panel gauge. Within 30 mins of returning to shore power, the inverter showed "FUL CHg" and 13.8v.

Can anyone suggest how to interpret these results, and what I might/should do next to diagnose any battery problems. Would data available from a battery monitor (like Victron 712) be helpful? Thanks in advance for any help!

 

[CruisingElvinRay]

You will find a battery monitor very helpful. It’s like going from a paper map in your car (useful in getting to a destination) to a gps (not only gets you to the destination, but calculates the best route, tells you your speed, eta, total miles remaining, etc…).

How low have you been discharging your batteries? Repeatedly going below 50% SoC accelerates the capacity loss. I’m concerned that you’ve been discharging below that often enough to degrade them.


Sent from my iPad using Tapatalk

 

[Hydraulicjump]

I am assuming you have the factory batteries (UB121100). My experience with them may be helpful (or not). I found that after two seasons of very heavy use (accidentally discharging below 50% SOC multiple times), they lose capacity but (maddeningly) maintain charge. What I mean by this is that I would charge them fully, either at the dock or on a long run, and they would be clearly all topped up. They would hold the charge as long as I did not put a load on them. But when I loaded them, they quickly lost voltage and did not recover. By the time I swapped them out (year three) they were useless. And it was always an overnight on the hook kind of thing, where I would wake up in the morning and they would be shot.

I got one of those relatively inexpensive battery capacity testers (Alcel) and discovered that the batteries had only 40% of original capacity. So it sounds to me like your batteries are toast. I have swapped them out. It is a pain to do, and you really need to make sure there is access through the space beneath your outside fridge. If not, you can use a saw and cut a hole. It makes the swap much easier and will not affect the structural integrity of the hull.

Interestingly, although the boat is six years old, I still have the original thruster/windlass battery and although it has lost some capacity, it is still serviceable. And I replaced the starter battery two years ago with a high CCA Optima battery. It too is in great shape. And I took a new approach to the fragile batteries (replaced with same as the factory) and have been babying them. The boat is plugged in all the time when at the dock, even though I lose anodes faster. I installed a Balmar Smartgauge (super easy to install because it does not require a shunt) and religiously avoid discharging the batteries below 50% capacity (using the gauge). The result of being very careful is that the batteries are at about the same capacity that they were two years ago. So it pays to take care of your batteries, although it is a pain.

Finally, running a coffee maker and microwave (through the inverter, obviously) puts a big load on the batteries, potentially shortening their life. Again, this will show up with this brand as a loss of capacity rather than the ability to hold a charge. We have discovered, when on the hook, the joys of Melita filters and heating stuff on the stove. And only using the microwave when the engine is running or we are at the dock.

I know this sounds kind of obsessive, but obsessive and boat are often used in the same sentence.

From Princess Cove on Wallace Island, BC with 92% capacity remaining on my battery bank.

OCD Jeff

 

[knotflying]

I would first make sure the batteries are fully charged and rested. Then I would put on a load tester. I am not as familiar with the 29 as I am with the 27. I believe access to the batteries can be difficult and therefore access to do a load test will be difficult. With that said, I have always had my engine running when using the inverter for heavy loads. You are sucking a lot of amperage off those batteries and the solar panels will not replenish what you lose. The alternator does a much better job. Don't you have a generator? If so use that instead of the inverter. Also, for reference, a full charge on a 12V battery is 12.6V, Anything over that is what is called as a surface charge and will dissipate after a while.

 

[GaylesFaerie]

You may also find a specific gravity tester worth while. I use a HydroVolt hydrometer. Readings and battery state will roughly follow:

FLA BATTERY

%CHRG VOLT Specific Gravity
100 12.70 1.265
95 12.64 1.257
90 12.58 1.249
85 12.52 1.241
80 12.46 1.233
SHALLOW CYCLE DISCHARGE LIMIT
75 12.40 1.225
70 12.36 1.218
65 12.32 1.211
60 12.28 1.204
55 12.24 1.197
50 12.20 1.190
45 12.16 1.183
40 12.12 1.176
35 12.08 1.169
30 12.04 1.162
25 12.00 1.155
DEEP CYCLE DISCHARGE LIMIT
20 11.98 1.148
15 11.96 1.141
10 11.94 1.134
05 11.92 1.127

 

[Gypsy]

Having just replaced my four AGM batteries, I want to make sure I don't discharge them below 50%. How do I monitor this? Do I need to install a separate battery monitor or do the existing monitors/gauges provide this information? And, if I need a separate monitor, do I need one for each battery or can the monitor be switched between batteries. The monitors that I have been looking at range between $10 and $250.

 

[scross]

I’d recommend a Victron Energy SmartBatterySense monitor. One monitor for each bank of batteries. It’s a very small plastic box that glued to the side of one of the batteries in a bank with its leads connected to the terminals of that battery. It’s Bluetooth and, in my case, links to my iPhone. It doesn’t have alarms, just reports out voltage and battery temperature. If you wanted to monitor all three banks you would need three of the monitors. The iPhone app (VictronConnect) let’s you view any Victron Energy monitor you have installed.
If you want a more robust monitor with alarms and such take a look at the Victron Energy BMV 712 Smart Battery Monitor. It monitors only one bank. So you would need a separate monitor and shunt for each battery bank you want to monitor.
To be honest, I’ve not needed alarms. I check my battery status several times each day I’m on the boat. I try to be proactive about energy management and not be reactive to the batteries being over discharged.

 

[Red Raven]

Having just replaced my four AGM batteries, I want to make sure I don't discharge them below 50%. How do I monitor this? Do I need to install a separate battery monitor or do the existing monitors/gauges provide this information? And, if I need a separate monitor, do I need one for each battery or can the monitor be switched between batteries. The monitors that I have been looking at range between $10 and $250.

Gypsy,

Full disclosure. I have a battery monitor and use it. However, I find over time I rely less on the battery monitor %SOC than just using the battery voltage. Yes, the monitor is handy but not required if your boat has a solar panel remote meter or an analog meter for each battery.

Our R27 Classic has an analog meter on the DC panel. Basically a dial gauge and a switch to select between batteries that measures voltage only. All three battery banks can be measured for voltage.

In addition, and easier to read, we have a Morningstar Solar remote panel that came with the boat. It will read the battery voltages of the house and the engine banks in digital form. It does not read the thruster battery. If you have a factory solar panel I believe this meter should be installed on your boat.

If you have an accurate voltage reading of each battery, that is really all you need if you understand a few things. First, you need to know the relationship of voltage to SOC for Lead Acid (including AGM) batteries. The table posted above by Gaylesfarie includes all the data you need in the %charge and volt columns. 50%charge (50% State of Charge (SoC)) is around 12.2Volts when the battery is at rest. Just do not let the batteries go below 12.2V. That’s it!

The key to the above is the “at rest” statement. For the house, if your refrigerator or inverter or other power hungry items are currently actively running the number will be lower. Likewise if a charging system is actively runn8ng the voltage will be higher. For this reason I check the battery voltage in the morning before the sun comes up or at night after the sun goes down, the refrigerator is not running, the engine is not running, and when we are not connected to shore power. Anything above 12.2V is good! For the thruster and engine batteries it is the same, thruster or windlass not running, no alternator, solar, or shore power charging. Anything above 12.2V is good!

A battery monitor is handy because it gives you a quick measure of actual amps (A) being consumed at the moment and total amp hours (AH) consumed (relative to full charge) as well as a SoC (%) measurement in addition to the voltage (V) discussed above. The problem with relying solely on a Battery monitor is that they depend on a defined new battery capacity for your boat in the settings. AmpHrs and the SoC measured can mislead you if your battery is not new and not in good shape. For example, if your battery bank is 200AH capacity when new but is now degraded to 40% capacity it is really an 80AH battery bank! If your battery meter reads 40AH consumed and 80%SoC you might think it is all good, but if you check the battery voltage and it is 12.2V (at rest) or lower you actually need to get charging now!

In short, a battery monitor is really handy for measuring healthy batteries but isn’t a 100% necessary tool nor should be solely relied on as batteries age and get degraded. Checking the rest voltage is sufficient in general, and actually necessary as a backup check of a battery monitor.

If you do install a battery monitor (which I do recommend with the caveats above) I think one for the house bank is sufficient if you do not want to go to the trouble or cost for measuring the Engine Start and Thruster batts. The Engine Start and Thruster batteries do not go into deep discharge under typical use and can easily be checked by voltage as in your car or truck.

Curt

 

[Gypsy]

Al, Curt,
Thanks for taking the time to answer my concerns. The info you provided is appreciated.

 

[Dcsqatar]

Thanks to everyone for the insight. My batteries are 25 month old, and were "AGM upgrade" per my invoice for my 29S purchased new in July/2019. I have carefully monitored voltage on all 3 banks, and the house batteries consistently (and quickly) achieve full charge on both shore power and alternator. I do not believe I have ever drawn them down below 12v rested. In other words, they have been drawn below that under inverter load, but always recover to 12v+ once inverter off. My concern is year-on-year performance degradation, which suggests that the batteries have lost capacity even though they still obtain and maintain a charge. From reading all the advice, I think my next step is to find a load tester. I do have some more questions if anyone has more time to answer!

1. Any recommendation on load tester to buy? I see everything from $20 at Harbor Freight to $170 from Grainger.

2. The four house batteries are obviously wired together in parallel. To load test them do I presume correctly that I need to isolate each one and test it independently? That would presumably be much more difficult then just testing the complete bank.

3. How do I interpret the load tester results? Will it tell me % of maximum (original) load capacity now at full charge? If so, I would then decide if I can live with, say, 40% of lost capacity?

4. I saw one recommendation to test for specific gravity (thank youGayles Faerie). Will that tell me much more than a voltmeter will?