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Solar or AGM battery problem

Sven

Seglare
Something seems wrong with the solar charging 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
 

Ryan L

s/v Naoma
Idea

Sven- Having seen your boat, and giving full consideration to your desire for a timely departure, I think the best solution may be for you to swap boats with us. That way I'll have plenty of time to trouble shoot the problem from my slip here on Shelter Island while you and Nancy sail south trouble free on a boat with far fewer systems... :)

Senta II is truly a beautiful and well loved boat. Thanks again for the tour last week. Wishing you following seas, fair winds, and problem free battery charging!

Ryan
 

Sven

Seglare
Hi Ryan,

We'll definitely consider your suggestion as a good possible solution.

Thanks for the compliments, Senta is blushing :egrin:

It was very nice meeting you too. Amazing how small the world is !

Read your web pages ... very inspirational.

We're still stuck here, waiting for a forwarded copy of the vessel documentation before crossing the border. Not a bad place to be stuck :)



-Sven
 

Guy Stevens

Moderator
Moderator
You are not going to like this answer... Sorry

My best bet is that what you are seeing is the AGM batteries dieing. The behavior is indicative of a battery that has oxidization of the plate material and consequent loss of capacity. As one cruiser put it: "My AGM batteries have become badly functioning capacitors!".

I know that someone is going to come on here and start arguing with me about this, but before you do, look up the recommended charge cycle and discharge floor of AGM batteries. I know of two distinct laboratory studies that have taken place the one linked to below, (Battcon did not do the study, but they host the complete text on their site). In addition to the Rusch study, another study which was undertaken by the Australian Navy is also available on line. Both studies concern AGM and Gel batteries and various applications for each. The findings of both studies are practically identical. (I don't have the link to the Australian Navy study, which is an even better study for our application. You should be able to find it using the internet search engine of your choice.)

Here is a link to the Rusch study.

http://www.battcon.com/PapersFinal2006/RuschPaper2006.pdf

Your experience matches all of the data that I have personally collected from a number of cruising boats out there actually cruising.

The way that we charge, and discharge batteries on cruising boats is not at all the way that AGM batteries were designed to be used. Both Gel and Flooded batteries are a significantly better for our application on cruising boats than AGM batteries.

I would recommend flooded electrolyte batteries first, and if you must place your batteries in a place that is inaccessible or will not allow you to maintain them and check them AT LEAST once as week, then I would recommend Gel Cells manufactured by the East Penn Battery Company.* (This is not an advertisement for them, I have no financial stake in their company, or there products. However they simply are the best that we have seen and are consistent dependable, and quality which we have not seen in any other brands that we have tested.)

If you have 500 25% discharge cycles on AGM batteries you have exceeded their lifetime rated discharge cycles.

The Australian Navy study is backed by the Rusch paper which you can find a complete copy of at the above link, including the attached spider graph, and the data and methodology that was used to create it and the conclusion which states: "For solar applications, maintenance-free batteries with very high cycle life are required. Here, the VRLA tubular Gel is the best choice."


gel-agm-battery.jpg

Further out on the Graph is better in all categories.

AGM's are great for two applications. One, military attack helicopters which was the first place that I was introduced to them, circa 1989 or 1990. They are also good in other high impact high vibration applications, such as off road vehicles, remotely controlled vehicles etc. The other is in short cycle teleco backup supplies were the expected drain is less than 30 minutes, and the system is expected to be replaced every 5 years. (Note in this application the batteries are expected not to be used at all in that five years!).

In the real world my experience with multiple cruising boats suggests that the case is actually worse than that stated in the studies. Cruisers would be very lucky to achieve 3 years of service out of AGM batteries. In the actual cruising environment, most will get about 2 years, significantly less if there is a single (1) discharge incident that is equal to or exceeds 50% of the AGM battery capacity. Two or more discharge incidents of 50% of total capacity, and the batteries are likely to be non functional following the 2nd discharge. A routine 25% discharge rate will decrease their life in the real world to less than 3 years. For a cruising boat the discharge and cycle limitations are not sufficient for our usage.

* Lithium Iron batteries are proving to be the best I have used for cruising applications, however their extreme cost makes them prohibitive for most cruisers at this point. A good sized battery bank will cost over $5,000.00 if they are utilized. However they have a 80% discharge floor, and are rated at over 5,000 cycles at 80% discharge. They also have an amazing recharge curve, (frequently exceeding the ability of standard charging devices). They are also not damaged by long periods of deep discharge or rapid discharge cycles. Amazing technology now we just have to wait for the price to come down to where we can afford it.

Sorry to be the messenger of potentially bad news.

Guy
:)
 
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Sven

Seglare
Thanks for the very well thought out reply Guy.

Mainsail gave similar advice earlier, after I'd already replaced the original AGMs with identical replacements.

I suspect you are both right even if I certainly hope you are not.

The batteries I replaced were almost 11 years old when we replaced them which was why it seemed like they would be a good choice. I don't think we've ever gone below 85% SOC, usually more like 90% SOC before we installed the Frigoboat.

The batteries are indeed a real pain to get to so even weekly access would be a major impact.

Time to ponder ...

Thanks again.



-Sven
 

Mark F

Contributing Partner
Blogs Author
Hi Sven and Nancy,

I don't have any direct experience with solar charging but I do live with 8 AGM's for my EP system and 2 for the house. Do you know how your Blue Sky MPP charger determines when to change from bulk to float? Can you see the voltage of each battery individually? If you have a battery that is behaving differently than the others the controller/charger might see that as a reason to shut things down. I would start by checking each battery individually at rest and at peak charging (if you haven't already:). In the past I have had to charge one battery by itself to get it within range of the other batteries so my 48 volt series charger can fully charge an entire pack of 4 AGM's.

I agree with Guy about lithium batteries they are amazing, I hope to change to lithium in my boat when my AGM's die.
 

Sven

Seglare
Problem was a poor connection !

Sorry for the repost of what I also posted on the CF, but I did want to share the end result in both places.

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)
 

Mark F

Contributing Partner
Blogs Author
Hi Sven,

That's good news. It sure is nice when a big problem turns out to be an easy fix :).

If you do not have one, one of those cheap handheld infrared thermometers is handy for checking for bad connections. I had a lug connection fail and was getting strange readings for that battery on my battery monitor. I thought it was a failing battery but checking the temp at the lug connections showed that connection was quite a bit hotter than the rest of the connections. I now periodically check the temperature at the battery connections.
 

Sven

Seglare
Hi Mark,

If you do not have one, one of those cheap handheld infrared thermometers is handy for checking for bad connections. I had a lug connection fail and was getting strange readings for that battery on my battery monitor. I thought it was a failing battery but checking the temp at the lug connections showed that connection was quite a bit hotter than the rest of the connections. I now periodically check the temperature at the battery connections.

We do have one but I didn't use it :confused:

Tanks for the reminder !



-Sven
 

Maine Sail

Member III
I know that someone is going to come on here and start arguing with me about this, but before you do, look up the recommended charge cycle and discharge floor of AGM batteries.
Guy
:)

Guy,

AMEN !!!! You're preaching to the choir on this one. I was a very lone voice years ago calling AGM batteries out for horrible life cycle issues when used on crusing boats. Since that time some have actually ebgin to listen but usually only after it is too late..

GEL batteries far outlast AGM and can even outlast basic wets. Flooded batts are still, by far the best Ah/$ solution but if you need a VRLA battery go GEL not AGM..



Sven,

I would suggest FIRST checking every connection, fuse holder, crimp connector, terminal corrosion etc. between the batteries and controller. What he descibes does not sound like an acceptance issue but more a procesor or resistance issue or possibly a temp sensor issue.....

The BS controllers are pretty relaible but if not allowed sufficent cooling can do odd things. Remember the face plate on these controlers is the heat sink....

You already have AGM so the best you can do is to TRY your hardest to get them to 100% SOC once per week, if possible. "Full" is when these batteries are taking less than 0.5% of 20 hour capacity at 14.4V... You would check this by turning ALL ship loads off and runing the alt or battery charger at absorption voltage. If you hit 1%/"C" that is sufficient but the 1% needs to be at absorption voltage not float voltage. Properly charged AGM batteries can go a LOT longer than when not.
 

Maine Sail

Member III
Problem was a poor connection !

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




Damn, gotta learn to read the whole thread before replying.:rolleyes: That said a bad connections was my first suggestion....:) Glad you got it figured out.
 
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Grizz

Grizz
Incremental education...

It's threads like these, with various options described and the accompanying links to source material and research, that reinforce the value of this particular site. Please note that none of this happens without interaction between participants scattered across the world. Wonderful, just wonderful!
 

clp

Member III
Sven, I'm curious about the tiller pilot. Not being familiar with a 39, but I can only assume it's a wheel steerer? The reason I ask is, I've got an ST2000, with Edson steering on this 29', and have been trying to engineer the thing to work. Not that I'm too cheap to buy a proper X-5, it's just that, well, OK I'm cheap. And I already own a tiller pilot.
If I had to guess, I'd say the rudder post enters your boat differently than mine. So say?
 

Sven

Seglare
Sven, I'm curious about the tiller pilot. Not being familiar with a 39, but I can only assume it's a wheel steerer? The reason I ask is, I've got an ST2000, with Edson steering on this 29', and have been trying to engineer the thing to work. Not that I'm too cheap to buy a proper X-5, it's just that, well, OK I'm cheap. And I already own a tiller pilot.
If I had to guess, I'd say the rudder post enters your boat differently than mine. So say?

The tiller Pilot acts as a replacement for the wind-vane on the Cape Horn when you want to steer a compass course rather than a wind relative one. The Cape Horn still supplies the power needed to turn the quadrant. The combination of the two won't solve your "cheap" problem, unfortunately :esad:

Had an ST2000 on La Petite and loved it :egrin:



-Sven
 
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