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Gel Cell Failure

PostPosted: Tue Jun 09, 2009 1:09 pm
by LAdamo
As a fan of AmplePower products on a previous sailboat of mine and future purchaser of Ample Power products for my current sailboat, I thought I'd ask your opinion regarding a battery failure I recently experienced. In the attached photos, you'll see a house bank of four and start bank of one group 31 gel cells in the battery compartment under the foot of the quarter berth in my sailboat. Of the five batteries, the only one not to lose its positive terminal was the far rear house battery which is located close to the bulkhead between the interior and an exterior cockpit locker.

I've formed my own opinion as to why this happened but I am hoping you might share your ideas as well. I will share more details as the topic unfolds...

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Re: Gel Cell Failure

PostPosted: Tue Jun 09, 2009 8:16 pm
by Coulomb
:o Wow! I've never seen anything like this before. It's hard to imagine that long term overcharging could have done this, although it will dry out the gel electrolyte and eventually corrode the positive plates.

Overcharge is generally easy enough to detect, either with meters or alarms. We'll be glad to learn more details.

Re: Gel Cell Failure

PostPosted: Tue Jun 09, 2009 9:14 pm
by LAdamo
I thought about overcharging, but we have a Xantrex smart charger which I think should be be OK.

In the nearly 5 years we've lived on the boat, the usage has been fairly consistent - almost no outings, nearly 100% living aboard at the dock. The big change during that time is that two years ago, I installed a hydronic heat system including running the hoses through that compartment since I was running them all around underneath the bunks. I didn't realize how warm the hoses would really get - the fluid is 150-180 deg F and the outside of the hose is almost too warm to touch when the system has reached a fully stabilized state. When I installed it, the batteries were in fine shape. I believe that the batteries were overheated and leaked at the positive terminals until they fell off. I have removed the hoses from this particular compartment and installed a thermometer. Now, over a 2 week period of typical usage, the max temp recorded has been about 80 deg F, which I believe would be fine. I have moved the thermometer to the neighboring compartment where there are still heater hoses present. In 2 days, I have seen over 90 deg F max. This is in San Francisco summer, where the heat runs for only a short time in the morning and evening. I think the real test of how hot it got in there will be a cold rainy weekend watching football with the heat on all day.

What I don't know is what the manufacturer recommended max temp range is for extended periods and what they say the failure mode would be.

The other possible issue that I have considered is that I installed DC refrigeration about a year ago. When both compressors are running, the system draw is about 10 amps on the batteries. I believe this would kick the charger out of float mode so it is possible that they have been subject to extended higher than float voltage conditions.

The bummer is that because the the batteries are under the foot of the bed, it is very easy to not check on them regularly. I intend to change this, but I want to correct the condition before I spend a thousand dollars replacing the damaged ones. I am considering insulating the divider between the battery and neighboring compartment.

Re: Gel Cell Failure

PostPosted: Tue Jun 09, 2009 10:02 pm
by Coulomb
The old saying that batteries like the same temperature as humans is true - 70 and 80s. At 120F no charging should be done. Our regulators used to cutoff at that temperature, but the reality is that a lot of power boats have batteries in the engine room and they get that hot. We raised to cutoff to stop the complaints.

I wonder what range of temperature compensation the Xantrex has. Does it have a battery over temperature alarm?

Re: Gel Cell Failure

PostPosted: Wed Jun 10, 2009 9:51 am
by LAdamo
I will look into the details of the Xantrex charger. It does have a temperature probe on one of the neg battery posts.

It might not be obvious in the pictures, but the appearance/amount of corrosion on the 4 batts that failed is amazingly consistent - almost like on the count of 3, they all went poof in unison. The only other sign of failure is a slight puffing of the top of the case around the positive terminal. Are you suggesting that the heat alone is unlikely as a culprit, but rather charging at too high a rate relative to the temperature is more likely? Why did the one house batt survive?

BTW - We discovered this on one of our rare outings which was, in fact, the first since the refrigeration went in. Ran the generator before going to bed. Five hours later, I woke up and found the battery voltage of the house bank below 12. Decided to start the generator - house bank couldn't do it. Tried start bank and there was zip. Confused, thinking a cable came off, I looked in the battery compartment and found what you see in the photos. Amazing how those electrons just don't want to cross the air gap. Had to call a friend to pick up a POS battery and deliver it to us via dinghy to get engine started.

As soon as I feel like I've protected against re-occurrence, I'll get to designing and installing a proper AmplePower system.

Re: Gel Cell Failure

PostPosted: Wed Jun 10, 2009 2:35 pm
by Coulomb
Heat alone is not the culprit. It took electric current. Overcharge
corrodes the positive plates. Somewhere in all our documents we explain
what happened to you - corrosion silently takes it toll on the positive
plate grid, weakening it. Then a high current demand suddenly ruptures
the fragile connection. You did that by trying to start the engine
using the house bank.

I wouldn't overlook the possibility of electrlysis playing a part,
perhaps as a side effect of the new heater system.

You should read the first two paragraphs about corrosion here.
http://www.amplepower.com/primer/etc/index.html

Putting batteries under a bunk is fine, but don't forget that you still
need ventilation because even sealed batteries can out gas hydrogen and
oxygen when over charged. Read the following URL:
http://www.amplepower.com/primer/explode/index.html

I'm guessing that because one battery survived, you don't have the
parallel wiring done with the positive off one end and the negative off
the other. This subject is discussed in our book, Wiring 12 Volts for
Ample Power.

You don't mention the brand of batteries, but recently we've heard
from people using Ritar gel batteries from China. Their charge
acceptance rate is quite low for gel batteries, and I'd guess they also
have a high Peukert's exponent that limits hight rate discharges.

Finally, your temperature probe is connected in the wrong location. Heat
buildup during charging occurs first and greatest in the positive plate,
and with parallel batteries the hottest post is the one that has the
wire going to the positive distribution. That's where you want to sense
temperature.

Re: Gel Cell Failure

PostPosted: Thu Jun 11, 2009 9:41 am
by LAdamo
Thanks for the type of information I was really looking for.

- I will have to work on a plan for venting. Apparently, the yacht manufacturer's reg's don't require them to put vents in for Gels.

- The electrolysis aspect could be a bear. This is a fully bonded Valiant. The heat system doesn't touch the sea. The refrigeration system uses "keel coolers" which I did tie into the bonding system.

- The parallel wiring is done per your recommendation so we'll have to look for another survival reason, but the temp sensor is definitely not on the first batt positive terminal. That's an easy fix.

- The charger is Xantrex Truecharge 40+. Manual @ http://www.xantrex.com/web/id/462/docserve.aspx (Page A5 says high temp shutdown is at 60 deg C for batt sensor - this seems high doesn't it?). It is set to 3-stage / gel / has optional temp sensor.

- The batteries are Interstate Batteries SQ-29, 550 CCA, 180 Ah. Interestingly, I can't find any 12v gel cells on their websites. Maybe they have discontinued carrying them for some reason. Maybe they are impostors.

- Something we haven't mentioned is the fact that the "high output" alternators on both engine and generator do not have any kind of smart regulation. I suppose this could have contributed to overcharging corrosion though we don't have many hours of charging them via engines.

If I let the heat system run all day during the weekend so that the cabinets/furniture reach a real equilibrium temperature and I still see a max temperature in that compartment of approx 80 deg F, do you see any reason to try to insulate it further? What temperature would cause you to make further changes?

Re: Gel Cell Failure

PostPosted: Thu Jun 11, 2009 5:22 pm
by Coulomb
Yes, 60C is higher than ideal to cut off charging, but pragmatic because
many power boats operate batteries in the engine room where that
temperature is the norm.

Many years ago at the Annapolis Sailboat Show a Valiant
owner informed me that he didn't need any of our gear because Valiant
boats were built to the highest standards. I agreed that the boats were
well built, but the electrical system was less than a high standard.

About 30 minutes later the owner of Valiant Yachts was in my face
literally screaming and cussing, telling me that I was ignorant about
electrical systems, on and on.

So here you are:

No smart regulators on the main engine or generator alternators;
Batteries mounted under the bunk without proper ventilation; and
Interstate gel cel batteries.

Do you have high and low voltage alarms?

Interstate tried to build their own gel batteries. They were a flop.
They ended up buying the parent company of Sonnenschein and ended up
with the Prevailer label. I haven't used any of their gel batteries.

You may have a really old set of Interstate gel batteries. In that
case, we can probably stop looking for other causes of failure.

If ABYC does not require ventilation of battery compartments when used
with gel batteries they are totally remiss. I think the the Coast Guard
made such recommendations after the boat exploded in the Carribean.

Valiant is a great boat, but the electrical system could use a little
work.

Re: Gel Cell Failure

PostPosted: Thu Jun 11, 2009 5:48 pm
by LAdamo
When our boat was being built in 2004, I asked them to install your products. I was politely told that you and Rich didn't see eye to eye - probably a reference to that same incident. Well, I tried and here we are. I agree completely that Valiant is a fantastic boat, but old fashioned on the electrical system and I knew even before we took delivery that I would be modifying it.

How does this sound as a plan?

- stop worrying about the compartment temperature now that the heater hose is out of it and my thermometer is showing a max of 80-82.

- get new set of batteries of respectable lineage and install the temperature probe in the proper place. Also put my thermometer probe at the same point so I can see what the temperature is.

- monitor carefully the voltage vs the temperature for a little bit to make sure the Xantrex is not way out of line leading to a tragically short battery life.

- redesign charging and monitoring system using your products and deal with issues like no venting.

Re: Gel Cell Failure

PostPosted: Fri Jun 12, 2009 10:43 am
by Coulomb
I understand passion for excellence, but when ego gets in the way of listening to constructive criticism then no amount of passion for excellence can replace that chance to improve.

As a first step add circulation to the battery compartment - for the sake of safety.

A temperature up to the mid-80s isn't bad. Air circulation may reduce that somewhat.

By all means monitor the temperature and battery voltage. You should determine what the temperature rise is after a long charge. It will peak 30-60 minutes after charging stops.