House Battery Bank Test Method?

[Shano]

I am wondering if I can test our house battery bank without removing the batteries and load testing the individual batteries. So...on our CW30 we have 4 UB121100 house batteries. With our batteries fully charged I flipped the main ac breaker off, I then turned the microwave on for 30 seconds using the inverter. The voltage dropped from 13.2 to as low as 12.1. I waited a few minutes then tried it again and the second time the voltage as measured by the inverter dropped from 12.7 to 11.6. I had the main fridge on during both trials. I wonder if someone with the same battery setup on a new boat tried this what their voltage drop would be and if this is a useful battery bank test? This is our 4th season with these batteries.

 

[Kimberly Dawn]

Can't speak to your testing process, but I can tell you I just received an email today from Fisheries Supply (Seattle) for Lifeline AGM batteries... as a RT/Cut owner you do get a discount.

Bob
The Doghouse 2

 

[Katmat]

Not sure why you couldn't use a 12 volt battery load tester.
https://harborfreight.com/automotive/di ... 61747.html

 

[Shano]

Not sure why you couldn't use a 12 volt battery load tester.
https://harborfreight.com/automotive/di ... 61747.html

I have a load tester similar to the one you mentioned but I think that they are for testing only one battery at a time. I guess I could disconnect all of the house batteries and try to test them in place one at a time but the space is pretty tight and it may not be safe to do it that way. I am trying to get a sense of how my 3.5 year old house bank compares to a new house bank the lazy way.

 

[BB marine]

It's best to test individually. If you are not having an issue with the battery bank it's probably ok.It's not a bad idea to remove all the cables to clean connections and then tighten connections as a preventative maintenance. This is a good time to load test and evaluate the batteries condition.

 

[ohioan55]

The recommended way is to test each battery individually. One battery could be weak and testing them all together will hide this fact. One weak battery will also affect the ability of the entire bank to carry a load. Weak link in the chain thing.

 

[Shano]

It's best to test individually. If you are not having an issue with the battery bank it's probably ok.It's not a bad idea to remove all the cables to clean connections and then tighten connections as a preventative maintenance. This is a good time to load test and evaluate the batteries condition.

Thanks Brian and ohioan55 , I will test them individually. The only issue I have had is that with the parallel switch turned on I had a low voltage warning come thru the Garmin system when starting the D6, this has only happened once and I know that the electronics are sensitive. It is surprising that with 5 batteries connected together it dropped the voltage enough to cause the Garmin electronics to warn of low voltage. Other that that we have anchored out several times recently and while we were only running the main fridge, Wabasto furnace, and the anchor light the house bank batteries did the job well and were showing 12.5 volts in the morning before any solar charge. I am planning on changing the engine battery for a Northstar group 31 or group 27 and pondering whether to change out the house batteries also. But if they are ok for another year then.....

 

[asm777]

Thanks Brian and ohioan55 , I will test them individually. The only issue I have had is that with the parallel switch turned on I had a low voltage warning come thru the Garmin system when starting the D6, this has only happened once and I know that the electronics are sensitive. It is surprising that with 5 batteries connected together it dropped the voltage enough to cause the Garmin electronics to warn of low voltage. Other that that we have anchored out several times recently and while we were only running the main fridge, Wabasto furnace, and the anchor light the house bank batteries did the job well and were showing 12.5 volts in the morning before any solar charge. I am planning on changing the engine battery for a Northstar group 31 or group 27 and pondering whether to change out the house batteries also. But if they are ok for another year then.....

Are you checking the voltage with the engine running on the Garmin system? I finally figured out that our alternator had gone bad and the Garmin Low voltage warning I was getting was because the voltage wasn't in the 13-14v range (stayed around 12.5-12.7v and dropping) with the engine running...

 

[iggy]

It's best to test individually. If you are not having an issue with the battery bank it's probably ok.It's not a bad idea to remove all the cables to clean connections and then tighten connections as a preventative maintenance. This is a good time to load test and evaluate the batteries condition.

Yep to the above. But it would also depend when the last time it was done.

Not to go against any one, but I would not use that tester from harbor fright. That unit is more like a toaster, it will heat up by putting a full load on the battery. Also you not set it to the type of battery you have.

I use something like these https://www.amazon.com/ANCEL-Battery-10 ... 546&sr=8-4


https://www.amazon.com/TOPDON-BT100-Aut ... 603&sr=8-5

You can set it to flooded, AGM or gel and to the CCA of your battery. It puts a small load on the battery and does the math and the test is done in seconds. So you can go from battery to battery and not wait for it to cool down.

In theory, you do not have to remove any cables when testing the batteries in the bank. Just go to one battery and place the leads on that battery's Pos and Neg post and do the test. Just have that banks battery switch set to off. Or remove all the cables and do the test. Ether way will work, but as BB mentioned, its not a bad idea to clean the terminals and use dielectric grease.

 

[barling]

Do both of these testers work equally as well for AGM's?

 

[iggy]

Do both of these testers work equally as well for AGM's?

The one I own they don't make any more and I don't want to endorse one. There are many others to pick from that are highly rated. Back to the question, in the descriptions on both, I would say yes. Worst case, send it back for a full refund.

 

[Hydraulicjump]

I too use the AncelBST200 tester and really like it. The problem is that if you are testing your house batteries they are wired in parallel, so it will think you have a single big battery. Best to disconnect the batteries to test them. You do need to enter the CCA and battery type for this tester. You may have to go online to find the CCA for your battery if it is not printed on it.

I have retired my old load tester/battery toaster. This new technology is a whole lot better. Or so I am told by people who are smarter than me.

 

[NorthernFocus]

... we have anchored out several times recently and while we were only running the main fridge, Wabasto furnace, and the anchor light the house bank batteries did the job well and were showing 12.5 volts in the morning before any solar charge. I am planning on changing the engine battery for a Northstar group 31 or group 27 and pondering whether to change out the house batteries also....

Conventional load testers don't provide accurate information on battery capacity. They assume a linear relationship between reserve capacity and CCA. That assumption is not accurate as demonstrated by the following actual test data

Unfortunately there is no easy/instant test to determine the condition/capacity of the house batteries. The most practical way is to simply record voltage data in a log book every morning after spending a night on the hook. Of course there will be a lot of scatter in the data depending on differing house loads but over time the data should show a downtrend.

Lead acid batteries begin to suffer long term damage when they drop below 12.3V. So when you rise and shine in the AM if voltage is 12.3 or higher life is good. If it's consistently below that you will experience a downtrend in performance. The lower the voltage the faster the downtrend.

We don't have a generator on our boat and rely completely on the house batteries for power. We're not heavy users with typical night time load being the fridge, LED anchor light, and chargers on phones/tablet/laptop. We run the engine for 10-15 minutes at 8-9pm every night to boost the batteries and to keep the engine from getting real cold by morning. We average about 40 nights per season at anchor. We're on our fifth season on a bank of two group 31 deep cycle batteries and still no issues with them. I will replace them when voltage is consistently below 12.3V when we wake up mornings.

 

[Shano]

Thanks everybody for their informative posts. When I test the batteries I will post the info.

 

[iggy]

I too use the AncelBST200 tester and really like it. The problem is that if you are testing your house batteries they are wired in parallel, so it will think you have a single big battery. Best to disconnect the batteries to test them. You do need to enter the CCA and battery type for this tester. You may have to go online to find the CCA for your battery if it is not printed on it.

I have retired my old load tester/battery toaster. This new technology is a whole lot better. Or so I am told by people who are smarter than me.

I AM BAD!! Yes, it would see it as one big bank. One cable from each battery must be removed. Sorry, I got bad news on my dog and trying to keep myself occupied. :roll:

But to go back to Dan's point. I must say that the load tester has worked for me reliably.

 

[Katmat]

Not sure why you would need to disconnect the batteries, just put the tester on each battery (unless you can't get to the batteries on your tug).

 

[iggy]

Not sure why you would need to disconnect the batteries, just put the tester on each battery (unless you can't get to the batteries on your tug).

Because there connected in parallel, not in series. So all of the Pos terminals are connected to each other. The same with the Neg ones. Just as the boat sees one big battery the tester will too. So one cable needs to be disconnected from the test battery.

 

[katmat1]

Not sure why you would need to disconnect the batteries, just put the tester on each battery (unless you can't get to the batteries on your tug).

Because there connected in parallel, not in series. So all of the Pos terminals are connected to each other. The same with the Neg ones. Just as the boat sees one big battery the tester will too. So one cable needs to be disconnected from the test battery.

If you connect one lead to say battery A's positive and the other lead to A's negative it will just read that battery same as if you put a VOM style meter across the terminals to check battery voltage.

 

[NorthernFocus]

...But to go back to Dan's point. I must say that the load tester has worked for me reliably.

How do you define "reliably"? What you're really saying is that it has worked to your satisfaction. Just trying to point out that for house bank battery purposes a conventional tester is giving you irrelevant data. When you use a tester the results are indicating an assumed position on the red line on the graph. Above 60 percent or so there are just as many data points on either side of the line. So in house battery service there is an even chance that your battery is in either better or worse condition than indicated by the test. In other words you can make just as good a decision by flipping a coin as you can based on a conventional load test. You may have replaced batteries that were good for another season or two. Or three....

Using a conventional tester to evaluate the condition of the house batteries is like timing a person running a 5k race and using that information to assume how fast they can run 100 yards or a marathon.

For house bank service all it takes is paying a little bit of attention to evaluate the condition of your batteries. For wet cell batteries there is a roughly linear relationship between capacity and voltage. Full charge is 12.7V and effectively dead is just under 12 volts. So for anyone's typical load requirements you can simply monitor voltage over time and calculate the percent of capacity that you use per hour. As the batteries age the percent per hour will increase for the same load. When you can no longer live with the rate of decline for your personal house load requirements it's time for new batteries.

One good thing about house load service is that you won't just wake up one day and the battery no longer functions as can happen with a starting battery. If one pays attention there will be a gradual decline in performance. As pointed out earlier if the battery is always maintained above 50 percent(12.35V nominally) the rate of decline is greatly reduced. At the other extreme if you let the battery run all the way below 12V and stay in that condition for extended periods of time then all bets are off. The battery can become useless very quickly.

 

[NorthernFocus]

...If you connect one lead to say battery A's positive and the other lead to A's negative it will just read that battery same as if you put a VOM style meter across the terminals to check battery voltage.

That is not correct. The VOM is reading the bank voltage not the individual battery voltage. Unless you have a switch in the circuit or lift a cable to disconnect the batteries in a parallel bank you can not get a valid test on an individual battery.