Battery thermal runawy alarm

[sailormed]

In a post on 29/7 from Dockhead he posted: "Then on top of that we were rafted up just last night to a gorgeous Colin Archer pilot ketch which burned down (!) due to thermal runaway and fire in the bow thruster gel battery".


I have had 2 batteries with thermal runaway. I detected both in the morning just by walking barefoot on the floor. Feeling the unusual temperature of the floor I immediately checked the batteries, disconnected them and put them on the jetty. The measured temperature was around 55°C.


Since I have more then those 2 batteries on my boat I was looking for a cheap tamparature alarm system. I found the 12V Temperature control switch W1209 on ebay, in the acrylic housing for a little more then 3 dollars.
Combined with a 12V buzzer I installed this on all my batteries. I put the alarm threshold at 45°C. At present in the full heatwave here batteries were just below 30°C, so 45° is OK.

[model 10]

This sounds more like a shorted cell rather than thermal runaway. I thought only Ni-Cad batteries suffered thermal runaway?

[a64pilot]

ALL batteries, even lead acid can have a thermal runaway, it’s extremely uncommon though.
Lipo’s can do so catastrophically

Lifeline addresses the possibility in their manual I think.
Right at the beginning, page 3.
http://lifelinebatteries.com/wp-cont...cal-Manual.pdf

[john61ct]

Distinction without much practical difference, overtemp condition should be alarmed, too high shut down the pack.

[model 10]

[QUOTE=a64pilot;
Lifeline addresses the possibility in their manual



They don't explain a shorted cell. That is the main reason for a hot battery in a boat.
Until the 787 came along, only planes with a ni-cad battery needed a temp sensor.

[john61ct]

We should have them fitted anyway, for temp-compensating voltage adjustments by a smart charge source.

[newhaul]

Originally Posted by john61ct

We should have them fitted anyway, for temp-compensating voltage adjustments by a smart charge source.

temperature compensation for charging has naught to do with thermal run away.

Afaik you don't temp compensate when charging Lfp on solar.

[AndyEss]

Originally Posted by newhaul

temperature compensation for charging has naught to do with thermal run away.

Afaik you don't temp compensate when charging Lfp on solar.

True, but an inexpensive temp sensor, with relay and/or data outputs, could be used for alarms, hi temp shutoffs and temperature compensation, if ever implemented. A battery temperature record might in and of itself be useful to monitor battery health. Many boats have plenty of computing and data storage capacity to implement this.
Another line item to my wish/to-do list.

[Dockhead]

Originally Posted by newhaul

temperature compensation for charging has naught to do with thermal run away.

Afaik you don't temp compensate when charging Lfp on solar.

I think it does actually. The Lifeline manual linked above says that in AGM batts thermal runaway occurs from too high charging voltage or high ambient temperature, like if the batts don't have enough air circulation. You can stop it if the charger senses too hot batts and cuts the charging voltage.


My problem seems to be inadequate air circulation (like none) in the aft bank which is under my bunk. The forward bank has never done this; this is the second time with the aft bank.


Stupidly I installed the single temperature sensor for the Victron charger/inverter to the forward bank, just because it was easier to get to .



If I were to stick with lead, I would move the sensor and add an alarm as suggested by the OP (great idea, BTW).

[john61ct]

Yes, temp sensors are useful for many functions.

If talking LFP, ensuring you never charge in freezing temperatures is critical when far from the equator.

And at least being aware when ambients are getting very high would help keep them down for longevity.

[Kenomac]

Originally Posted by Dockhead

I think it does actually. The Lifeline manual linked above says that in AGM batts thermal runaway occurs from too high charging voltage or high ambient temperature, like if the batts don't have enough air circulation. You can stop it if the charger senses too hot batts and cuts the charging voltage.


My problem seems to be inadequate air circulation (like none) in the aft bank which is under my bunk. The forward bank has never done this; this is the second time with the aft bank.


Stupidly I installed the single temperature sensor for the Victron charger/inverter to the forward bank, just because it was easier to get to .



If I were to stick with lead, I would move the sensor and add an alarm as suggested by the OP (great idea, BTW).

We have a $5 computer type silent cooling fan continuously exhausting air from our house battery banks, hooked up to one of the batteries. Wouldn’t this simple, cheap solution solve your problem and save you over $10,000 on lithium batteries?

Flooded lead acid battery bank located in a non-ventilated cabinet under the stern bed.... wow, that sounds like a lousy design on several levels. Hydrogen gas build up for openers.

[Dockhead]

That's a great solution. If I had understood the problem () , then I I would have done just that, years ago.

But I would not save $10k by replacing the lead and doing that now. 300a/h of lithium cells (@24v) is only €3000, vs €2000 to replace my lead banks. Plus a grand for BMS and other gear, and net cost difference to me will be only €2k or so for a totally superior system. That's worth it to me just for the experience.

[newhaul]

Originally Posted by Dockhead

That's a great solution. If I had understood the problem () , then I I would have done just that, years ago.

But I would not save $10k by replacing the lead and doing that now. 300a/h of lithium cells (@24v) is only €3000, vs €2000 to replace my lead banks. Plus a grand for BMS and other gear, and net cost difference to me will be only €2k or so for a totally superior system. That's worth it to me just for the experience.

don't forget to post your build in the http://www.cruisersforum.com/forums/...219455-11.html

[a64pilot]

Lead acid batteries under a bed, in the bilge etc are exceedingly unlikely to overheat from a lack of air ventilation.
You have to realize that the majority of lead acid batteries live in engine compartments where there is often little cool airflow (city traffic), and they don’t overheat.

The key is proper voltage for the battery temp, as long as charge voltage is correct a battery isn’t going to overheat.

A battery is very poorly air cooled, between the small surface area and the fact that the plastic case is a decent insulator there is very little of any air cooling.

I’d suspect that the majority of overheated batteries are from a shorted cell and constant charging.

Many aircraft batteries are in passenger compartments or baggage compartments, if the odds of a thermal runaway were more than extremely remote, then the FAA would have issued an AD to have those batteries removed or temp warning devices or something, and there has been none.
Aircraft batteries are extremely similar to regular batteries, the difference is the acid is a little stronger and the cell caps have a valve in them to prevent acid spill if you go negative G’s

[model 10]

Yes but all aircraft battery boxes are well vented with an inlet and an outlet for air flow.