Battery charging/monitor

[legaltender]

Any one got any ideas on this one?

I have 3 x 180 amp Delphi maintenance free batteries being charged by solar panels. These are 400 watt with MPPT regulator. My battery monitor NASA BM1 compact shows these producing up to 17 amps in Turkey, and reads 104per cent charged by the end of the day.

However, after dark the charge rapidly falls, and by dawn, the monitor reads 65-70 per cent full.
If this is correct, it would mean I have used 30-35 per cent of domestic capacity, about 165 amps in that time. I am running 2 fridges and LED lights. The monitor shows that when both fridges are on they use 8 amps. Assuming they are coming on every 20 minutes, that is only 2 or 3 amps per hour. That equates to say 30-40 amps used by the fridges at night, plus maybe 10 amps for lights, pumps etc.

When the sun comes out, the lost charge is replaced within a matter of hours.

The batteries are in good condition and under a year old.

What is the explanation for charge falling and rising so quickly and by so much?

Thanks guys!

 

[Carmel2]

I don't know why you see the big drop, others will help I am sure, but to give you a comparison, we run a fridge and a separate freezer, we also are LED throughout and we go down by about 10% overnight. From advice on here I changed from a BEP to a Merlin Smartgauge which I believe is far more accurate.

Good luck.

 

[RAI]

Sounds like your BM1 needs calibrating. For one, 104% fully charged is impossible by definition. Your batteries are probably no longer holding the same capacity as they did when new, but with only a year behind them that should not be significant, unless they have faults or have been mistreated. Although, some battery manufacturers quote their capacity based on more optimistic discharge rates. If you look up Smartguage, you will find descriptions about the errors that creep into battery monitor calibration.

 

[Chris_Robb]

I would ignore the percentage charge on BM1, its plain misleading. I would just monitor the voltages, and if - before the sun comes up, volts are 12.6 or so, then everything is OK.

 

[bjl]

Try zeroing the 'Amp' readout when the sun stops charging your batteries and in the morning you can read exactly how many Amps have been consumed during the night.

 

[Richard10002]

Try zeroing the 'Amp' readout when the sun stops charging your batteries and in the morning you can read exactly how many Amps have been consumed during the night.

+1

Ignore %age capacity and check Ah used. Zero it at fully charged and you can see cumulative use overnight. Compare with voltage with nothing running and you will know where you are at..... or someone here will

 

[lpdsn]

Any one got any ideas on this one?

I have 3 x 180 amp Delphi maintenance free batteries being charged by solar panels. These are 400 watt with MPPT regulator. My battery monitor NASA BM1 compact shows these producing up to 17 amps in Turkey, and reads 104per cent charged by the end of the day.

However, after dark the charge rapidly falls, and by dawn, the monitor reads 65-70 per cent full.
If this is correct, it would mean I have used 30-35 per cent of domestic capacity, about 165 amps in that time. I am running 2 fridges and LED lights. The monitor shows that when both fridges are on they use 8 amps. Assuming they are coming on every 20 minutes, that is only 2 or 3 amps per hour. That equates to say 30-40 amps used by the fridges at night, plus maybe 10 amps for lights, pumps etc.

When the sun comes out, the lost charge is replaced within a matter of hours.

The batteries are in good condition and under a year old.

What is the explanation for charge falling and rising so quickly and by so much?

Thanks guys!

I don't know the BM1, but using 30% of your batteries in a single night seems a lot. I've 2 X 180Ah domestics, but the battery monitor is configured for only 180Ah - quite happy with that as it provides a secret margin that only I know about. Maybe yours is set up in a similar way. So the first question is whether you are actually using 30%-35% of 540Ah per night? 189Ah (35%) over twelve hours is an average of 15.75A - does that correspond with what you think you're really using?

The fact that you recharge the batteries in a few hours makes me suspect you're not really using 35% of 540Ah each night.

I'd at least use it to try to get a figure for the consumption for each light or other bit of kit by turning everything off and measuring everything on its own, so you can work out where you electricity is really going. You might find some surprises.

As others have said, check the voltages. Basic battery monitors are not very good at working out how much you put back in. i.e. taking 5A out for two hours then putting 5A back in for two hours doesn't get you back where you started, but many monitors work like that.

 

[legaltender]

Thanks one and all for helpful advice. The BMI doesn't have facility for zeroing amps, it simply gives read out of current rate of charge in amps, and present voltage as well as state of charge of batteries.
Last night I charged the batteries to a reading of 100 pee cent (ie 95 per cent allowing for a full charge reading of 105 per cent) running the engine after dark. By 4 am the soc had dropped to 65 per cent and voltage reading was 12.2 v. It's now 8.30 am, I have about 2 amps coming in from the sun from the side. Metre reads 70 per cent and 12.4 volts. I turned both fridges right down at 4 am.

I am coming round to the view that everyone seems to have, replace the monitor!

 

[RupertW]

I am coming round to the view that everyone seems to have, replace the monitor!

Although that may be a good idea, if your battery voltage is dropping to 12.2v overnight then the monitor is roughly correct that you are losing most of your charge. What I am not clear about is whether the battery was completely isolated and at a settled voltage when you measured 12.2v. If it was then most of your charge is gone, therefore something is taking a lot of Amp hours out overnight - potentially your fridges, but worth checking what happens to the voltage if you leave your fridges off for an hour overnight - does the voltage keep dropping during that time?

Obviously your batteries might (for some reason) be holding very little charge so just a few Amphours going out could bring them down. Apart from the monitor I would follow above advice to keep checking for hot spots, then switch everything off - check no voltage drops over time, and switch the panel on bit by bit and watch for any sudden drop of voltage if you can't rely on an ammeter. Could be as simple as a bad hot connection on a shower drain pump or cabin light.

 

[jordanbasset]

Thanks one and all for helpful advice. The BMI doesn't have facility for zeroing amps, it simply gives read out of current rate of charge in amps, and present voltage as well as state of charge of batteries.
Last night I charged the batteries to a reading of 100 pee cent (ie 95 per cent allowing for a full charge reading of 105 per cent) running the engine after dark. By 4 am the soc had dropped to 65 per cent and voltage reading was 12.2 v. It's now 8.30 am, I have about 2 amps coming in from the sun from the side. Metre reads 70 per cent and 12.4 volts. I turned both fridges right down at 4 am.

I am coming round to the view that everyone seems to have, replace the monitor!

I may be having a senior moment here but was sure you could zero the amp hours on my NASA BM1?
I also suspect it maybe the batteries not holding a charge, can you take an independent volt reading?

 

[GrahamM376]

I may be having a senior moment here but was sure you could zero the amp hours on my NASA BM1?

Sods law, I left the boat and my instruction manual yesterday. From memory, the BM1 ammeter can and should be zeroed during installation. 104% charge readout when fully charged but still at charging volts is quite normal. The monitor should be set up when the batteries are fully charged but at their "at rest" off load voltage with no current draw or charge, not immediately after charging when voltage is still abnormally high. The monitor will then show 100% at this battery state.

 

[jordanbasset]

Has got me intrigued so checked on the NASA site, as thought you can zero the amp hours used, see page 6 of attached about how to zero it
http://www.nasamarine.com/images/file/BM1+-BM2+.pdf
Hope it helps

 

[lpdsn]

Last night I charged the batteries to a reading of 100 pee cent (ie 95 per cent allowing for a full charge reading of 105 per cent) running the engine after dark. By 4 am the soc had dropped to 65 per cent and voltage reading was 12.2 v. It's now 8.30 am, I have about 2 amps coming in from the sun from the side. Metre reads 70 per cent and 12.4 volts. I turned both fridges right down at 4 am.

I am coming round to the view that everyone seems to have, replace the monitor!

Sounds like you've got a definite issue with the amount of current you are drawing. 540Ah worth of battery should not drop to 12.2V with the sort of current you think you are using unless they've been really trashed.

I'd start by checking how fully charged they really are to start with. I suspect you aren't properly charging them each day. It would be worth sacrificing a few litres of diesel to run the engine to make sure they're really charged (forget the monitor - 100% means nothing when you've been through a few cycles - measure with a voltmeter). When you've just stopped charging the batteries they should be at least 13.8V, more if they're in good condition. If they're not, charge some more. If you can't get them up to 13.8V the end is nigh.

Then, and only then when fully charged, you can use the monitor to measure how many Ah you take out overnight. Then you've got to track it down and manage what you're using. An average of 15A is a lot. Something is taking more than you think.

If you take higher currents out of batteries, the manufacturer will only stand over much lower capacities - you might be able to find the spec for your batteries on-line. My 180Ah batteries, have a second quoted figure of 130Ah at a higher current - can't remember the details accurately enough to quote them.

 

[Richard10002]

I may be having a senior moment here but was sure you could zero the amp hours on my NASA BM1?
I also suspect it maybe the batteries not holding a charge, can you take an independent volt reading?

+1 I can zero the Ah on my BM2. You hold one of the buttons until it zeros. I found it in the manual.

 

[Richard10002]

Sounds like you've got a definite issue with the amount of current you are drawing. 540Ah worth of battery should not drop to 12.2V with the sort of current you think you are using unless they've been really trashed.

I'd start by checking how fully charged they really are to start with. I suspect you aren't properly charging them each day. It would be worth sacrificing a few litres of diesel to run the engine to make sure they're really charged (forget the monitor - 100% means nothing when you've been through a few cycles - measure with a voltmeter). When you've just stopped charging the batteries they should be at least 13.8V, more if they're in good condition. If they're not, charge some more. If you can't get them up to 13.8V the end is nigh.

Then, and only then when fully charged, you can use the monitor to measure how many Ah you take out overnight. Then you've got to track it down and manage what you're using. An average of 15A is a lot. Something is taking more than you think.

If you take higher currents out of batteries, the manufacturer will only stand over much lower capacities - you might be able to find the spec for your batteries on-line. My 180Ah batteries, have a second quoted figure of 130Ah at a higher current - can't remember the details accurately enough to quote them.

I think you are missing the point. You are assuming no loss of capacity. If the batteries have lost a lot of capacity, say to 180Ah, if you use 30%, you have only used 60Ah. 12.2V is recognised as being 50%SOC, which would equate to a usage of 90Ah in my sulphated example.

 

[legaltender]

Although that may be a good idea, if your battery voltage is dropping to 12.2v overnight then the monitor is roughly correct that you are losing most of your charge. What I am not clear about is whether the battery was completely isolated and at a settled voltage when you measured 12.2v. If it was then most of your charge is gone, therefore something is taking a lot of Amp hours out overnight - potentially your fridges, but worth checking what happens to the voltage if you leave your fridges off for an hour overnight - does the voltage keep dropping during that time?

Obviously your batteries might (for some reason) be holding very little charge so just a few Amphours going out could bring them down. Apart from the monitor I would follow above advice to keep checking for hot spots, then switch everything off - check no voltage drops over time, and switch the panel on bit by bit and watch for any sudden drop of voltage if you can't rely on an ammeter. Could be as simple as a bad hot connection on a shower drain pump or cabin light.

No, I didn't isolate the battery. The reading was taken from the BMI with the fridges but nothing else on at the end of the night.I had all three batteries checked with a digital battery tester and was told they are only a little down from the manufacturers quoted capacity. It's only 9 am here, the sun is low and from the side. Only a few amps are coming in; both fridges are on, but the voltage has already risen from 12.3 to 12.7.
Another pointer to the monitor being suspect is that when it shows the soc as full, the solar regulator is still on bulk charge. I would have thought that if the batteries were full, the regulator would go over to float .
I will do as you advise, though a quick check at the time the batteries were tested gave a zero reading on the BMI when everything was switched off.

 

[legaltender]

Thanks one and all for v helpful suggestions. I am thinking of changing my user name to Battery Hen. In the meantime I intend to go into Marmaris where there is a good boat electrician and hope they can sort it out. Maybe that's cheating, but it's preferable to having my head bitten off by the wife for turning down the fridges or switching off a fan!

 

[Chris_Robb]

Have you checked the volts shown on the BM1 with another measure? Surely this this would prove conclusively if the BM1 was faulty.

You really should utterly ignore the % charge on the BM1 - its pretty good rubbish once your battery capacity is well down.

The simple test as to whether batteries are accepting charge is to monitor the volts and input amps as you charge.

At start with 12.2 ( which is pretty low to run them) with a 75 amp alternator you should expect to see 50 amps going in. As charging progresses and the voltage rises expect amps to go down and volts to rise. Eventually amps will be down to 8 or so and volts at that time will be 14.4V If you are only getting 14V during the charge process then you are not charging efficiently, and you need to sort that out as well.

To reset the amp counter press the A-hr button and then press and hold.

Good luck in sorting this.

 

[sailinglegend420]

Thanks one and all for v helpful suggestions. I am thinking of changing my user name to Battery Hen. In the meantime I intend to go into Marmaris where there is a good boat electrician and hope they can sort it out.....

It could be you need a refrigeration engineer to check they are working properly - as well as a Marine Electrician!!!

With both fridges using 8 amps you should assume in Turkey near Marmaris, around the corner from me where it is 30C, that the fridges are on at least 50% of the time - that's 12 hours X 8 amps = 96 amphours, not the 30-40 AMPS you estimated. If the fridges are on longer than that, or they have leaking seals or faulty temperature controls then the Fridge consumption could be much higher. Add lights pumps etc... and the computer, and that could give much more than the 10 amphours you suggest, so you could be getting towards the 165 amphours (not amps) that you think the BM is telling you.

It seems you haven't followed some advice like turning off the fridges overnight to see if there are any other parasitic loads, and have you zeroed the Ah counter to get a proper reading, not a % of what the BM thinks you have in your bank?

Battery Monitors don't normally "Go wrong", they either work or the don't, but 75% of the time they are installed incorrectly and 95% of the time they are programmed incorrectly, so have you checked the settings of the monitor - like the actual capacity of your bank is input correctly, with a 10% reduction per year of use. Have you set the amps to Zero when no current is going in or our - disconnect all loads! And if your Delphi batteries are Calcium/Calcium they need very high charging voltages 14.8 to 16 volts. Are these set up correctly?

Running your alternator will never fully charge the batteries unless you run for about 24 hours! So your batteries capacity could be way down if they have been abused for 12 months.

 

[lpdsn]

Sounds like you've got a definite issue with the amount of current you are drawing. 540Ah worth of battery should not drop to 12.2V with the sort of current you think you are using unless they've been really trashed.

I think you are missing the point. You are assuming no loss of capacity. If the batteries have lost a lot of capacity, say to 180Ah, if you use 30%, you have only used 60Ah. 12.2V is recognised as being 50%SOC, which would equate to a usage of 90Ah in my sulphated example.

I had a boss once who had difficulty reading past the first sentence before responding. After a few months of frustration with incredibly stupid decisions, I found that careful re-arranging of wording made a big improvement.

Of course it is mainly speculation, but I suspect the problem is current draw, combined with a cycle of insufficient charging during the day - only enough to show 100% or so on the monitor rather than full recharging each day - and the batteries are well on the way to being trashed. Hopefully not, but that's my suspicion.