Battery tester for AGM house batteries

[Irish Rover]

Can anyone recommend a relatively simple to operate battery tester for testing my 210Ah house batteries. I saw another thread recommending a Topdon unit for cranking batteries. Would this unit do the job or is there something better.

 

[chris-s]

https://amzn.eu/d/66JwjzN

I’ve been using one of these for a while and although I can’t say how accurate it really is it seems to be good enough.
I test each of my house batteries separately.

 

[VicS]

Can anyone recommend a relatively simple to operate battery tester for testing my 210Ah house batteries. I saw another thread recommending a Topdon unit for cranking batteries. Would this unit do the job or is there something better.

There are some videos you can watch.

The Topdon BT100 appears to aimed at testing a cranking battery. Ie one which is required to supply a high current for a short time but you require your house battery to be able to supply a much smaller current for a prolonged time
It also does a charging test which tells you a little more than a multimeter will.

It does not address how well the battery retains its charge

Useful for a garage workshop perhaps but as far as the boat owner is concerned its value is somewhat limited.

 

[alahol2]

Best way I've found is to do a capacity test with a couple of 25W car headlight bulbs and a couple of multimeters, one for volts, one for amps. Only problem is that it takes a long time and you need to take readings every hour. There are constant current capacity testers on the market but they run at £50+.

 

[cpedw]

A long time ago, I devised this battery load tester. I think all the components are still available but the Malin references are for nostalgia only!

 

[William_H]

OP wants to know how good his batteries are. ie will they do the job he wants them to do. He has 210AH house batteries. Possibly 2 in parallel. So he needs to isolate the batteries. Now these are designed to give a lowish current for long period of time. And in fact that is what they are used for in service. ie 5 to 10 amps for many hours. There is now way a tester can test instantaneously the capabilities for long time. The tester can only check volt drop at high current. (this is very useful in testing an engine start battery.)
So the only way to test the usefulness of a deep cycle battery needed for house services is a check with a known current drain over a period of time. This can be done as suggested with a head lamp bulb and much patience. However the battery can be assessed in service by checking voltage after using your services aggressively. Lights fridge pumps etc. You will get an idea of just how good your batteries are by what they will do for you. Keep a log so that over a period of time (years) you will see a demise in performance. Eventually you will opt for new batteries. If he does isolate and test the 2 batteries individually he can get a comparison which can be really useful. ol'will

 

[Irish Rover]

I'm not very technically gifted, and to compound matters, I'm a lazy, impatient type always looking for fast results with minimal input. So is there an easier way to test the batteries. The Topdon tester I mentioned in my OP apparently measures the internal resistance of the battery. Will this tell me if my batteries are healthy or otherwise. I have 3 x 210ah AGM batteries connected in parallel.

 

[Daydream believer]

I had 2 AGM batteries which were a couple of months out of warranty. I was not happy that they were giving the required performance & wondered if such a meter would give me the info I needed. Not knowing whether to spend £20 or £80 on ameter-ie what sort to purchase-I rang the supplier for advice.
I was told NOT to waste my money, as these meters did not really tell one if a battery was any good or not. The only way was a proper test. They would arrange for collection & testing, even though they were out of warranty.
I sent them back & after 2 days they said that they were OK, but the chap said that he intended to have them tested further. This seemed odd to me. However, Inspite of being out of warranty, 10-14 days later 2 new batteries arrived FOC.

 

[Tranona]

I'm not very technically gifted, and to compound matters, I'm a lazy, impatient type always looking for fast results with minimal input. So is there an easier way to test the batteries. The Topdon tester I mentioned in my OP apparently measures the internal resistance of the battery. Will this tell me if my batteries are healthy or otherwise. I have 3 x 210ah AGM batteries connected in parallel.

Load testing is not appropriate for your service batteries, it is capacity you need to know and post#4 is a simple but slow way of testing that. Do the engines have their own start batteries? Do you have a battery monitor that shows charge and discharge plus state of charge? This will help understand how the bank is being cycled and whether it is coping with the demands you are placing on it.

 

[vyv_cox]

Load testing is not appropriate for your service batteries, it is capacity you need to know and post#4 is a simple but slow way of testing that. Do the engines have their own start batteries? Do you have a battery monitor that shows charge and discharge plus state of charge? This will help understand how the bank is being cycled and whether it is coping with the demands you are placing on it.

Furthermore I understand that drop testing (really a dead short across the terminals) is terminal () for leisure type batteries as it can distort the narrow, delicate plates and short them.

 

[Irish Rover]

Load testing is not appropriate for your service batteries, it is capacity you need to know and post#4 is a simple but slow way of testing that. Do the engines have their own start batteries? Do you have a battery monitor that shows charge and discharge plus state of charge? This will help understand how the bank is being cycled and whether it is coping with the demands you are placing on it.

I think you don't believe how much a dunce I am when it comes to electrics. So to answer your questions, as best I can. I have 3 x 210Ah house batteries in parallel. I have separate start batteries for each of the engines and the generator. I have a Blue Sea Multimeter which shows Voltage and amps and is selectable to show the house and each start battery separately. I'm at anchor right now and each of the three settings is showing voltage above 13v - house and stb =13.50 and port 13.05 - but there are 2 x 70w solar panels feeding and it's a reasonably sunny day with minimal cloud. When I select the amp reading all 3 are showing 3.3 but truthfully I have no idea what that means.

 

[VicS]

I think you don't believe how much a dunce I am when it comes to electrics. So to answer your questions, as best I can. I have 3 x 210Ah house batteries in parallel. I have separate start batteries for each of the engines and the generator. I have a Blue Sea Multimeter which shows Voltage and amps and is selectable to show the house and each start battery separately. I'm at anchor right now and each of the three settings is showing voltage above 13v - house and stb =13.50 and port 13.05 - but there are 2 x 70w solar panels feeding and it's a reasonably sunny day with minimal cloud. When I select the amp reading all 3 are showing 3.3 but truthfully I have no idea what that means.

What exactly do you have?
One of these?

 

[Irish Rover]

What exactly do you have?
One of these?

View attachment 178195

 

[PaulRainbow]

I think you don't believe how much a dunce I am when it comes to electrics. So to answer your questions, as best I can. I have 3 x 210Ah house batteries in parallel. I have separate start batteries for each of the engines and the generator. I have a Blue Sea Multimeter which shows Voltage and amps and is selectable to show the house and each start battery separately. I'm at anchor right now and each of the three settings is showing voltage above 13v - house and stb =13.50 and port 13.05 - but there are 2 x 70w solar panels feeding and it's a reasonably sunny day with minimal cloud. When I select the amp reading all 3 are showing 3.3 but truthfully I have no idea what that means.

It's easy.

Turn off and disconnect the batteries, or you can do one at a time. Make sure they are fully charged and leave to rest for 15-20 mins..

Measure the voltage with a multimeter, note it and the time.
Connect a known load to each battery and leave for one hour. Leave to rest for 15-20 minutes and record the voltage again.
Repeat until the rested voltage is 12.1 volts.

Multiply the number of hours that the load was connected by the amps of the load. That's the amount of amp hours you can get out of the battery by taking it down to 50%

 

[Irish Rover]

It's easy.

Turn off and disconnect the batteries, or you can do one at a time. Make sure they are fully charged and leave to rest for 15-20 mins..

Measure the voltage with a multimeter, note it and the time.
Connect a known load to each battery and leave for one hour. Leave to rest for 15-20 minutes and record the voltage again.
Repeat until the rested voltage is 12.1 volts.

Multiply the number of hours that the load was connected by the amps of the load. That's the amount of amp hours you can get out of the battery by taking it down to 50%

Thanks. I really don't think I have the patience for that and, unless we get a storm which keeps me in port, I'm not sure I'd want to give up the boating time to do it.
As always, I'm looking for a quick fix and that may well be to just replace the batteries - as far as I'm aware they're in the boat since new and saw 6 years of charter, so probably not a lot of life left in them anyway.

 

[Tranona]

Thanks. I really don't think I have the patience for that and, unless we get a storm which keeps me in port, I'm not sure I'd want to give up the boating time to do it.
As always, I'm looking for a quick fix and that may well be to just replace the batteries - as far as I'm aware they're in the boat since new and saw 6 years of charter, so probably not a lot of life left in them anyway.

600Ah is a big bank. That gives you 300Ah potential to 50% discharge. Decent AGMs have a cycle rate of 800+ - that is you can discharge down to 50% 800 times. In practice I think you will rarely get down that far when cruising because of the hours the engines are running plus any solar will be replacing part of your consumption. A more detailed battery monitor than just your voltmeter will give you a more accurate picture of your daily net consumption. Not expensive and easy to fit but really worth having Your voltmeter in your pic is showing a float charge into house bank presumably from some solar which indicates that your batteries are pretty much fully charged and any consumption is being more than met by a charge.

Moving on to estimating life in years and whether your batteries are nearing the end.. Assume the boat was in use on charter 20 weeks a year that is 140 cycles. With a potential of 800 cycles that gives a life of around 6 years. However, for reasons given above I doubt they have been routinely taken down to 50% SOC (state of charge) and if there is solar will have been kept fully charged when not in use so may well have lots of life left in them. Paul's suggested test will give you good information, but appreciate the lack of patience to do it - there is no short cut. However I would suggest fitting a monitor and getting a handle on your own pattern of consumption as a start. Doubt the batteries will crash and because you have dedicated start batteries you will never be marooned nor be without some form of charging.

The killer of batteries is stopping at anchor for a few nights and using electricity that you can only replace by solar during the day or running the engines. Once you have determined your level of consumption you can think about whether you can live within what you have or need to cut consumption or increase power generation. The fact that the boat has done 6 year's chartering where the same issues arise and is still on the same batteries suggests the setup is not too far out,

 

[William_H]

It does seem the OP is worrying in anticipation of house battery failure. He will know it when the batteries fail by not giving enough power when at anchor using power and not replacing. It will not be terrible when they fail all he need do is start the engine(s) and recharge. This needed recharge becoming more frequent.
However OP should be aware and prepared to isolate the house batteries one from another to then enable comparison of apparent performance. One will usually die ina dramatic before the others. (pulling the others down). Certainly don't go rushing to replace batteries that may be ok at least for some time yet. o'will

 

[VicS]

I think you don't believe how much a dunce I am when it comes to electrics. So to answer your questions, as best I can. I have 3 x 210Ah house batteries in parallel. I have separate start batteries for each of the engines and the generator. I have a Blue Sea Multimeter which shows Voltage and amps and is selectable to show the house and each start battery separately. I'm at anchor right now and each of the three settings is showing voltage above 13v - house and stb =13.50 and port 13.05 - but there are 2 x 70w solar panels feeding and it's a reasonably sunny day with minimal cloud. When I select the amp reading all 3 are showing 3.3 but truthfully I have no idea what that means.

You meter shows the voltage readings for one of the three batteries according to which is selected by the switch below the display, as you already realise. Possibly the most useful readings will be when the batteries have rested with no charge or load for a number of hours ( ideally 24 hours.) There is a little table in the instructions to relate that reading to % state of charge but read the whole of the section for a full explanation. When the batteries are being charged by an engine alternator or by your solar panels you will see the charging voltage. When there is a load on the battery you will see the terminal volts which will be less than the resting voltage and will depend on the magnitude of the load.

There is only one current reading, it is not selected for the batteries individually like the voltage reading. Exactly what it is depends upon how the shunt is wired into the system. It might be the total nett charge/discharge for all the batteries combined , which it will be if it has been wired as shown in the instructions, or , if it has been wired in the negative connection to just the house battery bank , it will be the charge or discharge for the house battery bank. hopefully this is what it will be as this will be the more useful of the two alternatives.
When the batteries are charging the reading will be positive but when there is a nett load the reading will be negative.

 

[Irish Rover]

Thank you all. Despite myself, I'm actually learning a little.