exploded battery

Only at considerable expense Angelique. With a bank existing of just a few large batteries and current requirements of many 100's of amps you need quite an array of semiconductors to switch these loads.
Tesla divides their 6000 cell lithium bomb in small, manageable clusters, each with their own control circuits. Some people still think it isn't safe.

 

Sure, it is also the first time for me.
Every battery sold nowadays has a label that says "absolutely maintenance free" and most have no means to check the electrolyte level.

This week I brought another one to its grave. Italian made, 90 Ah, maintenance free, used in my RV for less than 4 years. On my last trip it couldn't supply the TV (30 watts) for more than 2 hours. I suspect the charging circuit that is part of the vehicle (also Italian) to destroy batteries when left unattended.

 

Maybe the car is parasitically draining the battery?

Right now my car battery I can tell is losing capacity, I think sulphation. It is getting harder to start the car. The battery was made in 2011. Car is a Buick Roadmaster Wagon 1994. I know the charging system is ok.
Most of my boat batteries seem to fail with a shorted cell and they have water covering the plates when they short. The car batteries seem to loose capacity, sulphate without shorting a cell.

I also suspect battery makers wish to sell more batteries and as cheap as possible. So they make the plates light and thin and expect them to wear out sooner so as to sell more batteries quicker.

Back to that exploding battery, I think if you have a single failing battery it will be manifest to the user that it needs to be replaced. But a large paralleled bank is not going to be so noticeable. So maybe dont use sealed batteries in large battery banks.

 

Good idea: any elegant solution I can think of (So Far) has to handle the difficulty posed by conventional fuses. Fuses need to blow if a battery gets a shorted cell, but NOT blow when a short high-current requirement like engine starting or big bow thruster comes along.

So there are three components:
1. electronic current sensing on each battery
2. some hard-contact or other very-low-resistance disconnect for each battery
3. a microcomputer-based control system that decides what to do

2. is the hard one. Big latching relay? Some monster low Rds ON power FETs?

COULD be done. Hmmm....

 

CDK
On the Battery University website there was a section that dealt with solar charging of 12volt batteries. One comment was that if you have a 12 volt solar panel, that in high heat and sunlight conditions, solar panels are capable of producing up to 40 volts.
The solar panel should have the circuitry between the panel and the battery to limit the voltage to reduce the chance, not eliminate, of your type of overcharge/explosion

A solution to protecting the shorted cell battery in a parallel battery bank might be to put a solenoid between the positive post that is actuated by a heat sensor that is attached to each battery. This solenoid would be normally closed without a current draw.When the temperature reaches a certain value, the solenoid would open and prevent current from moving in from the other batteries or out to the load.
An alarm or instrument light could be ran to the helm to show a problem

In our case, the invertor/charger manufacturer had one heat sensor that was attached to one battery but it was hooked to the 5th battery furthest from the battery that malfunctioned and did not help.

Also, this single heat sensor with our type of charger would only shut down the charger but would not shut down the other batteries current input trying to feed the lower voltage, dead shorted cell battery. A condition which one of the contributors mentioned.

 

Hi CDK,

I had same kind of problem with my RV batteries. I found the original charger did a poor job of managing the batteries. Also it was very slow to recharge and so it took a long time if I was off the grid using a generator.

I bought one of these:
http://www.amazon.com/gp/product/B000GANZZ6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

..and it works great. Recharges from generator about 3 or 4 times faster, and it manages the batteries much better in the opposite situation where the RV is unused for a while. Once in a while it automatically runs a 14.4V equalizer charge. So I bought another one of the 12V backup batteries in our home. Works great. (I do not get a commission)...

 

Thank you Terry, I would need a 230V AC device of course, but I've seen they have that too, albeit not in 45 A. but 60 A.
The unit the RV came with also charges the starter battery and uses the alternator output for the fridge and house battery charging as well. I assume these functions are not incorporated in the PD9245CV...

 

My Li-Ion cordless tool batteries monitor each cell for charging, this protects from fires and avoids most "memory" issues.
Memory is caused by one cell reaching full charge before the rest, the charger senses the correct amp signature and cuts off, meanwhile the rest of the cells are not fully charged, over time this will get worse.

 

A internally shorted battery may heat up enough to ignite the hydrogen gas without burning the fuse. The cells would try to equalize the voltage and will increase current on both the positive and negative cables, unless the short is on one of the end cells. If the short was on the negative end cell, a fuse on the positive cable would not help.

 

Why would a short in an end cell not increase current in both cables? Unless the battery acts like a capacitor or has a short from the interior of the battery to the exterior of the battery the current (not voltage) must be equal at both terminals.

 

Back to school Gonzo!

 

Couldn't this be done by a solenoid switch like there is on a starter motor, they can switch 100's of amps and draw only a little current to do so. Maybe this application requires a special designed solenoid switch. . ? ?

 

There must be such a relay for every member of a battery bank, so that's not a practical solution. Solid state switching is to be preferred.

 

There ARE Normally-closed solenoid type relay. But the system would have to have power from the "other" batteries to disconnect a battery. And keep it disconnected until manual intervention.

There must be a relay with actuation like the usual momentary car door lock mechanism... Hmmm...

 

It is pretty practical as we are trying to switch up to 300 amps. What would a solid state switch cost.
A normally closed solenoid would cost about 20 bucks per solenoid, this is pretty cheap
If you can send some reference to a solid state switching system that can deal with 300- 350 amps, I would be most interested.
When all 5 of our 1100 ah, AGM batteries died, they had to be replaced at a cost of about 4,000. If a solid state solenoid/switch is available and cost effective, this would be the way to do.

The next challenge is to find a temperature sensor to attach to the battery to trigger the switch

From Terry King
There ARE Normally-closed solenoid type relay. But the system would have to have power from the "other" batteries to disconnect a battery. And keep it disconnected until manual intervention.

The draw on such a solenoid is in the milliamp range and could stay on for an extended period of time