Overheating Battery Issues

[westwinds]

Originally Posted by FlyingCloud1937

Don't forget a temp censor for the alternator, especially for charging AGM's and Lith, it will save the alternator from burning up. FLA's also need a alternator temp sensor, when you have a large bank in ratio to the size of the alt.

lloyd

Another option is to get a a heavy duty alternator that can put out a constant high amperage without burning up. For my last alternator replacement I got a heavy duty Bosch that does the job. It cost about 50% more than an ordinary alternator.

[Amnesia II]

Originally Posted by witzgall

+1 on the wiring issue. Do you have the positive and negative leads going to the same battery? If so, then there is your likely problem, or at least there is one problem. The positive cable need to be on one end of the string, and the negative at the furtest _ terminal at the other end of the string.

Chris

Thanks for pointing the cable connections out Chris, infact the batteries are connected correctly as you advised.
Thanks everyone for your helpful replies.

Let me clarify a few things: The temp sensor is from the Prosine 2000 inverter and just sticks on the battery casing...no electrical connection at all.
I have the sensor on the battery closest to the engineroom to cover the hottest location of the batt bank.
I have boosted the regulator/alternater voltage but not exessesively...14.5v but the last recent overheating was while on shore power which is a totally different charging system.

Each overheating only the offending battery gets VERY hot...60 degrees C, and on testing with the multimeter 10.8v indicates a dropped cell with all the other batts reading 12.7v

[sailorchic34]

I would adjust the max charge voltage down to 14.2. AGM's was real touchy with over voltage.. Everything I've read indicates 14.1 to 14.4V max.. Really depends on the AGM battery manufacturer.

If you have three fried batteries then voltage set point might be to high.

So when does the temperature sensor show high temp, is it when you have a high AC load on the inverter and charger is trying to keep up???? Or no inverter load and just charging.

Also have you measured the charging voltage at each battery with a Volt meter.

Was the batteries that over heated first on the Positive side or negative side of the bank. I'm going to guess that its on the negative side.

[Boulter]

Hi:

Any chance there could be high resistance in a cable connected to the battery, putting extra heat into a cell near by? I don't profess to understand batteries well enough to take this idea any further.

Boulter

[Nicholson58]

Originally Posted by Ike

AGM batteries are temperature and charging voltage sensitive. I would suspect overcharging. Check the voltage output of the alternator. If it is more than 14.5 volts your are cooking the battery. Most AGMs require a charging voltage between 14.1 and 14.4 volts. Unfortunately many alternators put out more than that and need to voltage regulated for AGMs and Gel cells.

Make sure you follow the vendor's chart regarding the proper voltage. No guesses allowed.

Did you try moving the temperature sensor to other bateries?
If it was just your engine chargine alternator I would suspect you may not have a proper charge controller as a replacement for the usual voltage regulator. (Balmar or other?)

[westwinds]

60 degree Celsius = 140 degree Fahrenheit. That's a hot battery, and 10.8 volts is too low since the battery is being charged. So, what's the voltage on these batteries with shore power? However, you are also destroying batteries with the engine alternator? What was the voltage on the engine alternator before you set it at 14.5 volts? I suppose it could be that you have been using voltages too high for AGM over the past several years and it is finally destroying the batteries.

[Captain Bill]

Lifeline is currently recommending charging at 14.4-14.6 on their AGMs. The battery showing 10.8 has a dead cell (probably shorted)and the other batteries are feeding through the short as is the charger. I recently had one of my lifelines short out and both batteries heated to 174f until I removed the charge and then they increased to 188f before I disconnected them from each other. When I talked to Concorde they said that this is what commonly occurs when on of the batteries in a bank develops a short. The short in my battery develoed after running into some steep wind opposing current waves in the Gulf Stream. It was a moonless night and you couldn't see the wave trains coming. In any case we fell off the back sides of a couple of these waves and slammed very hard. It was shortly after this that we found the the batteries overheating. While AGMs are more shock(physical as opposed to electrical) resistant than some other batteries they can still be shorted if subjected to violent shocks. Is there any chance you had a similar slamming incident before your batteries started giving you trouble?

[Amnesia II]

Thanks Capt Bill & everyone for input...lots to consider there.
The boat was used far differently by the previous owner in California..shore power and a weekend away every 2 weeks or so.
I fitted a 200 amp alt instead of the 80amp original, everyday use of the boat on my Pacific crossing completely contrasted it's past use.

I did extensive research before increasing the voltage on the reg to 14.5 for the AGM's.....within safe limits.
However, age, high daily usage( charge/discharge), maybe a poor connection somewhere is having a nasty effect which I have to sort out.

[sailinglegend]

Originally Posted by Captain Bill

Lifeline is currently recommending charging at 14.4-14.6 on their AGMs...........

Where did you get this information?

Lifeline currently say on their website 14.2-14.4 volts.

[Captain Bill]

Originally Posted by sailinglegend

Where did you get this information?

Lifeline currently say on their website 14.2-14.4 volts.

You are correct, that is what the web site recommends and that is what the paperwork says that comes with the batteries. It also says to only use a constant voltage charger whic would seem to eliminatge a three stage charger. If you talk to their technical support they will tell you to read the technical manual, not the owners manual. The technical manual is much more....well technical. In any case the absorption voltage is dependent on temperature and since I was in Maine this summer my battery temps were hovering around 60f which according to the technical manual should require a 14.56 volt absorption voltage, at 70f it requires 14.41v. Assuming that since we are taliking about boats that the batteries are likely that the temps will not get much below freezing or above 90, at least while the boat is in the water. I'm also assuming that the batteries are not in the engine compartment which may not be true in many cases. The technical manual states that an absorption voltage of 15.1V is required at 30f and down to 14.15v at 90f. It seems that the simple statement made on the web site and in the owners manual doesn't quite cover the range of requirements that boaters have to deal with in real life.

Here is the link to the technical manual.
http://www.lifelinebatteries.com/manual.pdf

[sailinglegend]

Originally Posted by Captain Bill

You are correct, that is what the web site recommends and that is what the paperwork says that comes with the batteries. It also says to only use a constant voltage charger whic would seem to eliminatge a three stage charger.............

A constant voltage charger is only used for maintaining batteries in long term storage.

All deep cycle batteries should use multi-stage constant current charging. This means alrenators MUST have an external multi-stage regulator.

[noelex 77]

Originally Posted by sailinglegend

A constant voltage charger is only used for maintaining batteries in long term storage.

All deep cycle batteries should use multi-stage constant current charging. This means alrenators MUST have an external multi-stage regulator.

Battery chargers, solar,wind controlers and alternator regulators on boat systems use constant voltage for the regulated phases (absorption and float)

[sailinglegend]

Originally Posted by noelex 77

Battery chargers, solar,wind controlers and alternator regulators on boat systems use constant voltage for the regulated phases (absorption and float)

But they also use constant current for the Bulk stage....

That's what defines a proper multi-stage regulator as opposed to an alternator that ONLY has one constant voltage mode.

[noelex 77]

Originally Posted by sailinglegend

But they use constant current for the Bulk stage....

During the bulk phase the current is simply the maximum current that can be delivered by the device. There is no controlled limitation. A 30A battery charger will supply 30A during the bulk phase because this is the maximum it can produce.
Swap it for a 40A charger and charge current will go up to 40A in the bulk phase.

In practice the load goes up and down, as does the output for divces like the alternator and solar power so during the bulk phase the battery current varies considerably.

There is no control placed on the charging until the absorption phase and this is controlled by voltage.

Most boat charging sources don't even measure battery current, so they have no mechanism to charge with constant current.

[Maine Sail]

Originally Posted by sailinglegend

But they also use constant current for the Bulk stage....

That's what defines a proper multi-stage regulator as opposed to an alternator that ONLY has one constant voltage mode.

Even a "dumb" regulator has both bulk/constant current and absorption voltage.

Bulk = Anything before the batteries rise to the absorption voltage limit. This current can be limited by either the batteries or the limit of the charge source. If the bank will take 70A and you have a 50A alt it will pump out what it can until the voltage comes up to the absorption setting. If the batteries will only take 80A and you have a 120A alternator the alt will pump out 80A until the terminal voltage rises to the "limiting" set point then enter "absorption" or voltage limiting mode..

Absorption = The voltage limit of the regulator. Current is applied to the battery via pulsing the field so as not to "over shoot" the voltage limit.


Voltage regulators are nothing more than voltage limiters..... They limit voltage in absorption and then limit at a further reduced voltage when in float. Any time before they are limiting voltage at the set point the alt is in constant current mode. The regulator will turn the power on and off, very quickly, to match what the battery bank needs, in current, to maintain, but not over shoot, that voltage limit..

Any charge source that regulates to voltage, once the voltage set point is attained, is a constant voltage charge source. Just because bulk is technically a constant current (full field) does not mean the device is not a constant voltage charger, alt, regulator, solar controller etc..