Cause of death?

cparke

I have four 6V Lifeline deep-cycle sealed lead acid batteries which are now 9 years old and have failed. Not surprising, but it is the way they failed very suddenly that leaves me curious as to how this happened and if I did anything wrong with them over the years. Maybe some here with more experience has some possible explanation.

Basically, these batteries were bought new together, connected in series to provide 24VDC, were only used a handful of times per year, rarely allowed to fall below 50% discharge, stored in a fixed stationary location (not in a vehicle or boat), and kept on float charge with a temperature sensor the rest of the time. My understanding of battery aging and failure is that as batteries age, they lose capacity from charge cycles and sulfation. But based on what happened to me, there must be more to it than just that!

Recently, I called this 9 year old battery bank into service. About 10-15 minutes later, the battery at the positive (+) end of the series suddenly failed. At rest, that battery still reads 6.42V like when it was new. But now with just a small load, the voltage drops to 2V or so and almost no amps come out. Remove the load, and relatively quickly the battery voltage rises back up to 6.42V.

The other batteries in the bank seemed fine, so I decided to switch to a 12V battery bank configuration to use the remaining three batteries for however long they last. However, similar results occurred with the next 2 batteries: again after 10-15 minutes of service, each battery at the positive (+) end of the series failed in similar way! I’m left now with just one working 6V battery at the negative (-) end of the series, the same one that has been there all three times, but I have no facility to charge it or utilize just 6V. I’m also doubtful the battery would function under load any longer than the others, even if I had an application to for it.

So, I’m confused here about what might cause this kind of battery failure. It’s almost like a fuse blew inside the battery, or lead plates cracked, or cells shorted, upon applying the load. Does age alone eventually cause this? Strange too that it was always the battery at the positive end of the string, coincidence? What process must be going on inside the battery to cause this, and is there anything that I could have done differently over the battery life (like not keep them on float charge for years) to change the form of death?

Not planning to perform an autopsy, but would like to get an understanding of what could eventually go wrong in a lead acid battery to cause this type of age failure. Thanks for your thoughts.

crcook84

I recently ran into a problem with my own battery. It’s not the same situation. But, maybe you can glean some information from it.

I have a lead acid battery that has a manufacturing date of 2016. Recently, the voltage dropped on it. The individual cells were always topped off with appropriate fluids. I was fortunate enough to get my hands on a desulfator. So I decided to spend 4 weeks desulfating it. Now, we live in Texas. This means temperatures over 90F at least 1/3rd of the year. After desulfating it outside the first three weeks, I take it inside to let it disulfate the last week in an environmentally controlled room. After the last sulfation, it initially shows 8v. I wait a few hours and the voltage goes up to 12.8v. Not only that, I install it in my car and I’m able to turn over the car twice. I hooked it up to a trickle charger to see if, overnight, I could get a little bit more voltage out of it and it climbed to 13.1v and the car was still able to turn over. I let the battery sit for a few days because I didn’t need it right away and I’d rather use it for something unimportant if it fails. When I get ready to use it, I find that the voltage had dropped to 8v.

Now, the temperature outside the night I tried out the battery going into the next day when it reached 13.1v was around 80F. Over the next few days I had held off using the battery, the temperature reached over 90F. At this point, I don’t know what is going wrong with the battery internally. Whether the chemical composition of the acid/water mixture had changed or the cells inside of the battery had changed their properties due to 6 years in 90F heat or something else entirely. I just know that the battery was holding a decent enough charge to turn over our car engine for 12 hours before the voltage dropped again.

Obviously, this is not exactly the same situation as what you are going through. However, in my opinion, a combination of temperature and age can change the chemical composition of the acid/water mixture as well as the properties of the internal cells. They may seem to work perfectly fine under ideal conditions at first. However, the moment you bring them into a real-world situation, they just fail.

Foxxie

9 years is probably the best you’ll get out of those batteries. Once their capacity drops off like that. its pretty much toast. you won’t be able to get much more out of them. Likely disintegrated inside and worn down to just nubs connected to the tips of each electrode to the battery terminals.
Could try topping up the water if they are low. be careful and dont overfill. Charge them up first before adding any water. Make sure to not overfill it. only add enough to just cover the tops of the battery plates. and not any higher.
If a full saturated absorption charge for minimum of a few hours 2-3 hours at 14.4 to 14.6v doesn’t get the battery capacity up. then its likely shot. and you won’t be able to get anything more out of them.

ive got a 6v 5AH spring terminal type AGM sealed lead acid battery and its from 2016 and somehow still works although not the same capacity as when it was new. it charges up and discharges with a useful capacity range. Even though it has mostly spent its life sitting unused and not being maintained. only occasionally topped up but mostly just sitting. Not sure how much more its got left in it. it has never been deep cycled below 50%. and it doesn’t have many total cycles on it either.