Solar or AGM battery problem

[SvenG]

Something seems wrong with the up-til-now-perfect solar charging system or the batteries, but I don't know what.

(Note, these are AGM batteries.)

We've been all solar for 6 months now, not counting the times when we have motored. We've had an abundance of power and have been absolutely amazed at how well the system has worked. In the last week or so something has changed, or I've just noticed it.

The Blue Sky display kicks in as it should with sun rise, 12.x to 14.3 volts and 0.1 Amps to start with, then climbing to 4 Amps or so as the sun gets higher. It shows that it is bulk charging. This is an MPP charger.

In the past, the Amps would continue to climb until about noon, peaking at 22 if the water maker was running, otherwise sitting at about 8 or so until the Victron would show that the batteries were getting close to 100%. Now it stops climbing and instead drops down to 1 Amp or so and goes into "acceptance" mode after just an hour or so. An hour or two later it falls to .3 Amps and goes into float mode.

According to the Victron we're only at 85% charge and the voltage at night (not open circuit, but no real load) drops from 12.7 to as low as 12.4 which I see as vindication of the Victron reading.

IOW the charger is acting as if the batteries are charged when they are far from full.

I considered the possibility that it could be an issue with lower winter sun angles but I don't think that's the case as the charger shouldn't go into acceptance mode and then float while the batteries are less that 90% full ?

Wish this had happened earlier since we are crossing the border to Mexico in the next day or two.


Suggestions appreciated.

Thanks,


-Sven



Details:
2x135 Watt Kyocera panels
Blue Sky MPP charger
4x100 Ah Lifeline AGM in house bank (18 months old)
1x100 Ah Lifeline AGM in spare bank (18 months old)
Spare bank charged via an Echocharger

[sailinglegend]

Originally Posted by SvenG

....In the past, the Amps would continue to climb until about noon, peaking at 22 if the water maker was running, otherwise sitting at about 8 or so until the Victron would show that the batteries were getting close to 100%......

Why peaking when the watermaker is running????

We need some + or - signs to indicated charging or discharging.

Have you tried it on your spare bank - or is that just the starter?

[noelex 77]

The first thing I would do is independently measure the charge voltage using a multimeter on the batteries.

To charge the AGM batteries the solar controller should let the battery voltage build to the absorption voltage, (usually about 14.5v for AGM) and keep it there for the absorption time (usually between 1-2hours). Then it should drop to float voltage (usually about 13.5 forAGM) and hold it there.

If there is enough sun and not much load this is the charging profile you are looking for.

If this is what your controller is doing the controller is working correctly.

I think the most likely explanation is the controller is defective.


BTW the 22A is exceptionally good if this is the output of your 270w. So good, I think the reading is probably optimistic.

[SvenG]

Originally Posted by sailinglegend

Why peaking when the watermaker is running????

We need some + or - signs to indicated charging or discharging.

Have you tried it on your spare bank - or is that just the starter?

The output of the panels goes up as the load increases, up to the point where it matches the maximum the panels can put out. That's an empirical observation, not sure how it is implemented.



-Sven

[SvenG]

Originally Posted by noelex 77

The first thing I would do is independently measure the charge voltage using a multimeter on the batteries.

To charge the AGM batteries the solar controler should let the battery voltage build to the absorption voltage, (usually about 14.5v for AGM) and keep it there for the absorption time (usually between 1-2hours). Then it should drop to float voltage (usually about 13.5 forAGM) and hold it there.

If there is enough sun and not much load this is charging profile you are looking for.

If this is what your controller is doing the controler is working correctly.

I think the most likely explanation is the controler is defective.


BTW the 22A is exceptionally good if this is the output of your 270w. So good, I think the reading is probably optimistic.

It might indeed be optimistic as the 22 Amps were at 14.4 volts = 316 watts. I only saw that once, for a few minutes, but I sure wasn't complaining

Until now the system has been amazing, supplying virtually all our needs, including water maker, frigoboat refrigeration, computer use, lighting, power tools via inverter, and so on. We don't even have a shore power cord and had never been below 85% SOC (per the Victron).

Thanks,



-Sven

[sailinglegend]

Originally Posted by SvenG

It might indeed be optimistic as the 22 Amps were at 14.4 volts = 316 watts. I only saw that once, for a few minutes, but I sure wasn't complaining.....Until now the system has been amazing, supplying virtually all our needs....We don't even have a shore power cord and had never been below 85% SOC (per the Victron)

Like Noelex 77 I felt 22 amps charging was a bit much and thought there was some confusion with discharging!

You offer some more information which maybe gives a clue to your problem.
"We don't even have a shore power cord"
This means you may not have been charging your batteries up to 100% often enough. Lifeline AGMs must be charged to 100% at least every three weeks. Shorepower is the best way.

You maybe believing your Victron Battery monitor too much. Any battery monitor is not accurate unless you get the batteries back to 100% regularly.

I would also suggest that now that we are late in the season, depending on where you are, the solar is consistently NOT getting your batteries any where near 100%.

You only have 400 Ah which is the absolute minimum for the kind of cruising you are doing. Have you measured your Ah usage over 24 hours by turning off your solar and measuring the AH used. Have you extra equipment on board that is using extra power - like a second computer, or kids with you using the computer all day?

150 Ah/day would in theory need a bank of 300 Ah, but if you only ever charge to 80%, easy by engine or solar, then the capacity you need is 40% more - that's 420Ah.

A simple immediate solution is to add the spare battery to your bank and get a small AGM Red Flash or Odyssey for the starter bank.

[Vasco]

AGMs aren't good for cruising unless you have some way to regularly charge them to 100%. Most cruisers use between 50% and 85% and seldom get them up to 100%. I had AGMs for two seasons then they were useless. Back to flooded. Expensive lesson.

[MarkJ]

One of your connections is stuffed.


Go find the shonky connection.

After that, pull the MPPPPPT controller off the line. You don't need one for 400 amp hour battery bank so it won't hurt. Then see how they charge.

But don't do that till your have done the source of you problem.... A faulty connection.

All my problems have always been connections. Some last a decade, some a month. It's nothing to do with a $300 pair of crimpers, it's that one of the connections decided to suicide.


Mark. <----- I am an electrical genius because I know it's always the connections!

[SvenG]

Originally Posted by MarkJ

Mark. <----- I am an electrical genius because I know it's always the connections!

I am really hoping Mark is right and suspect he is (even if that's wishful thinking). I incidentally got a private e-mail with the following suggestion

I would carefully check the connections between the charger and the battery. A three-stage charger goes into float mode when it senses that the charging current has dropped to a low level, i.e. a charged battery won't accept much current at the regulated charge voltage (~14.4 V). If there's a loose connection somewhere then the added resistance will drop additional voltage, and the battery will only see the charge voltage minus that drop. For example, if you have even 0.5 ohms of additional resistance due to a bad connection, then the 4 A of charge current will cause a 2 V drop at the bad connection. Now your battery sees only 12.4 V of charging voltage instead of 14.4 V. The battery will draw less current at this artificially low voltage, thus fooling the charger into thinking that the battery is charged before it really is.

Right before I came up to get my e-mail I had looked at the Blue Sky display and compared it to the Victron. The Blue Sky was seeing 13.4 volts but the Victron only saw 12.9 volts ... a smoking gun which certainly points to a loose connection ... I HOPE !

Just a BTW: I don't think we have ever run the bank below 85% SOC before the current problem.

Thanks for all the suggestions, time to access the wiring !



-Sven

[noelex 77]

Originally Posted by sailinglegend

150 Ah/day would in theory need a bank of 300 Ah, but if you only ever charge to 80%, easy by engine or solar, then the capacity you need is 40% more - that's 420Ah.

A simple immediate solution is to add the spare battery to your bank and get a small AGM Red Flash or Odyssey for the starter bank.

400AHrs is a reasonable sized battery supply for this sort of set up.
It's unlikely the OP is using 150AHrs a day as 270w of solar will not generate this much power on average.
Solar boats tax their battery capacity less than a boat relying on the main engine or generator.
If the OP is using 80AHrs a day say 40AHRs of this will be used during daylight hours when the solar panels will replace the power. The battery therefore will only be drained 40 AHrs overnight. These sort of numbers fit in with OPs description of how the system is performing.

The battery capacity needs enough reserve to cope with, and even, out poor days. This does vary from location to location. Summer in the Med for example gives one cloudless day after another. Solar provides a very consistent output and battery capacity can be small. Tropical areas can see much more variation.
A large solar array relative to power used also reduces the need for battery capacity.

In the days before solar and wind yachts needed a very large battery capacity. Many boats persist with notion that these very large battery banks are needed when a simple analysis will show they are increasing their battery costs and adding weight for very little practical gain.

[sailinglegend]

Originally Posted by noelex 77

400AHrs is a reasonable sized battery supply for this sort of set up.
It's unlikely the OP is using 150AHrs a day as 270w of solar will not generate this much power on average......

Have you ever actually measured the Ah discharge over 24 hours using a Battery Monitor with all charging disconnected. Only last week we did some tests and we use 65 Ah from 2000hrs to 0800 hrs sitting in a marina in Turkey. Another colleague here did it for 24 hours and was using 150 Ahrs.

To size a battery bank you need to consider the worst case scenario - night cruising for 24 hours with bad weather and no solar charging. We use 10 amps or more continually for boat system/autopilot/fridge etc.. That's 240 Ah, so a bank of at least 500 Ah is needed. Any charge source can easily get from 50-80% charged easily and fairly quickly, but getting to 100% takes very much longer - so you often only replenish your bank by 30% not 50%, so you need a bank 40% larger. That's a 700 AH battery bank - and you are still having to charge the bank every day.

Solar is the way to go, but the OPs 270 watt is as you say probably not enough to replace his Ah usage AND fully charge his batteries.

[noelex 77]

Originally Posted by sailinglegend

Have you ever actually measured the Ah discharge over 24 hours using a Battery Monitor with all charging disconnected. .

Yes my system actually measures the AHrs used independently from the AHrs produced so I can see the usage and production every day, without disconnecting the charging.

Solar produces over 95% of the power I use so I do need to keep careful track of things.
In summer I use about 120AHrs a day. There is no need to conserve because I produce more than this so computers etc are often left on when they are not being used.
In the depths of winter I have to be more careful. By installing the most energy efficient products I can still live comfortably on about 55AHrs a day at anchor and 70 AHrs sailing.

Everyone's requirements will be different. It's not unusual for boats to use double this. On the other hand I cruised for some years on a boat with only about 17AHrs a day available.

[SvenG]

We're very happy.

We dug down to the batteries and redid the connections, tightening some and re-doing a couple of crimps.

Of course, this morning was socked in ... but drumroll ... the panels are charging just fine again. When the sun almost popped out the Amps jumped back to 8.5 and the charger/controller no longer thinks the batteries are charged but is still staying in bulk mode 7 hours later.

Since we'd need a 1000 mile long shore power cord we'll probably forgo that solution

From sundown to sunup we typically use 15-30 Ah for fridge, un-rationed lighting and computer re-charging. That's at a mooring or anchor or slip. Since we are all LED the lighting draws almost nothing. The fridge is a small keel-cooled frigoboat that draws 3-4 Amps at full blast but has a 25-33% duty cycle in Southern California (cold water).

Under way the Broadband radar draws less than an Amp (if I recall correctly). The Cape Horn (CH) does the steering and even if we need to steer a compass course we just hook up the ST2000 tiller pilot to the CH and that is another draw of less than an Amp. The AIS, depth sounder and chart plotter probably draw more like 2 Amps.

When new, the water maker used 22 Amps but once it got broken in it seems to have dropped to 18 or so. At 6 GPH we could live with 1 hour per day but run it more like 2 hours per day while out in non-oily waters. At other times we run it for 4 hours to make up for lack of running where there are natural oil seepage issues. On a sunny day around noon those 4 hours are almost covered by the panels in real time. If we have to motor and don't have a full water tank we'll turn on the water maker too.

If the weather gets too bad or the days too short we have the option of firing up the 110 Amp Balmer attached to the old Perkins but so far we have never had to do that and before this issue cropped up we'd never been below 85% SOC.

Conservation through equipment choices has been our strategy and so far it has worked beautifully.

This glitch was unnerving as we're about to cross the border but thanks to WiFi we got lots of helpful inputs here and elsewhere, including the answer !

Thanks for all the suggestions.



-Sven (fingers crossed that the solution is permanent)

[Kettlewell]

Read about AGM Battery maintenance here.

[T1 Terry]

If you get a chance to buy a tube of Alminox some where, clean every terminal connector and paint this stuff between them and reconnect them. Lead acid batteries are shockers for creating a bad connection through oxide build up and the symptoms you posted show all the signs of this being the problem.

T1 Terry