RE: [Chrysler300] Group 27 Batteries

John,

I stand by my original post, and can back it up from printed material provided by battery manufacturers and engineers. Also, battery state of charge (specific gravity) most definitely can be determined by reading the battery voltage across the posts with no load and when not connected to a charger.. Notice I wrote "state of charge" I did not write "battery capacity", they are two different things. A battery's cell open circuit voltage = specific gravity + 0.845. So a 6 cell , 12 volt battery that is fully charged equals 1.260 specific gravity + 0.845 x 6= 12.63 volts across the posts. This is nominal because temperature affects the value as does S.G. variances cell to cell.

Self discharge is a fact for all lead acid batteries (actually all batteries to some extent). This is why battery retailers must periodically provide freshening charges to the product in stock. Pure lead plates will have the lowest self discharge, but even they will self discharge given enough time. Storage temperature plays a large role here too.

I'm not suggesting all battery maintainers are created equal or that they can be used across all types. What I am stating is that if properly used, they will extend the life of a battery during long periods of non-use. Once a battery discharges, water replaces the acid and sulfation begins to form, and if left long enough it will preclude the battery from accepting a charge. I had this happen to good quality, two year old flooded group 27 in my 300G. I let the car sit for almost 10 months during a house remodel and the battery would not take a charge. Rather than just buy a new one, I decided to spike the electrolyte with hot acid (1.265 S.G.) by removing an equal amount of low gravity acid and replacing it with the hot stuff. The battery now began to slowly take a charge, As the specific gravity continued to rise, I pulled off some acid and replaced it with distilled water until the battery was fully charged and all the cells read about 1.250. Got another 3 years out of it, can't do that with an AGM battery.

I now use inexpensive maintainers on unused batteries in my truck, 300 and lawn tractor and check them periodically. They work for me, and I do not see any appreciable water consumption as a result. An alternative would be to just give the battery a periodic freshening charge, that works too, but I get busy and forget. By the way, I do get my maintainers from Harbor freight, and I had my doubts too.

Bob J

Danville CA

From: John Grady [mailto:jkg@xxxxxxxxxxxxxxxxx]
Sent: Wednesday, May 27, 2015 11:06 AM
To: 'Bob Jasinski'; Chrysler300@xxxxxxxxxxxxxxx
Subject: RE: [Chrysler300] Group 27 Batteries

Bob, I agree with all except first paragraph. An external monitoring design using a battery voltage, or fixed trickle voltage , to decide anything about charging (as it must) in passive storage has absolutely no way to know state of charge from that voltage. It does not change from half to full charge . see graph of your own batteries, voltage vs charge state. “the light goes on, but they dim when I try , and it will not start” –right? The light was nice and bright… . The only way and not easy, is to charge it heavily or discharge it ,look up volts under certain draw etc. vs charge, or use hydrometer, or track AH in and out, as solar people do (I have had stand alone solar for 30 years ) . Left on say 13.8 trickle overcharges it.=water use. The problem is about the 1 volt no man’s land from sitting idle volts, 12.6 , and beginning to charge ? 13.2? That is variable temp dependent and somewhat unpredictable.

I developed a habit of watching headlights during crank, how much they dim tells you LOTS about battery. As it ages internal resistance goes up, volts drop more. If you see it dim way down, even if it starts ok, time for a new battery. But volts resting will still be perfect , charging system perfect.

Quite aside from opinions about it, the batteries DO go dry on maintainer trickle charger auto charger-- whatever. Reality check. I believed all the BS for years ,too. . And they do just fine left alone. Even 1% a day is 0.8 AH , in 100 days 80 AH would be dead. Does not happen .180 days later it starts right up, as Don relates, even 8 years old. Admittedly some charge has passed away, (normal , as you say) but not enough to prevent a ready, positive cranking speed. ; I too have seen ten years with no devices and two years with fancy devices. Why I started looking into all this, it gets to be big $ buying 8 or 10 batteries every spring, after a winter on maintainers in long past years. . Especially big MB one for 300CD diesel I had for 25 years with a built in maintainer, wired permanently to block heater. Never got more than three years. . And SL600 with the trunk floor ruined by acid overflow.

Industrial installs are monitored carefully ,and cycled on load. The opposite example industrial thing is standby lighting. I own several large industrial buildings --all the gel cells ,100’s of them in emergency lamps die regularly, due to sitting at 14 + volts ; fire alarms too. I would note cynically that battery companies like to sell batteries, must love battery tenders, and float chargers. . ; SAE battery guy tries to explain how to make them last in cars. And they do. That book is “Batteries for Automotive Use” by Reasbeck and Smith. Reasbeck , a PhD, is Chief Scientist and Director of R&D for Lucas. (yes , the prince of darkness! And warm beer ,due to Lucas refrigerators) . Book is quite good.

APC (American Power Conversion) the huge UPS company in RI, even goes so far as to make their big 4500 watt units so that only their physical size battery fits in it, about 8 ~ 27 size batteries for 48V .The thing has never worked here, 3-4 x, on power out, red light says bad batteries, only a few years old. . I traced this to absurd 58 V float(14.5 v each ) ; I fixed that myself (no adjustment as designed ) and threw out their cases so I could use wet cell batteries .APC lives on selling you batteries at 2x list, of same AH wet cell, every two years.

Smile; can only lead to the water….!! Good discussion, in any event.

John Grady, current PE

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of 'Bob Jasinski' rpjasin@xxxxxxxxxxx [Chrysler300]
Sent: Wednesday, May 27, 2015 11:56 AM
To: Chrysler300@xxxxxxxxxxxxxxx
Subject: RE: [Chrysler300] Group 27 Batteries

There is a big difference between a battery charger and a battery maintainer. All lead acid batteries lose some of their charge over time. The rate is about 1/4 to 1% per day depending on what makes up the plate alloy, and the temperature in which it is stored. Old style lead /antimony alloys are around 1%. New calcium and other proprietary alloy mixes are less. If a battery enters winter storage fully charged, and the car is stored in cold temperatures the rate is slowed by the cold temps. Stored at a high temp will increase local action within the cells and will self discharge faster. A good battery maintainer, with circuitry designed for the type of battery design; sealed AGM/ gel vs. flooded, will only MAINTAIN the state of charge to full. It only puts in what is needed to offset the internal loss.

The trick with VRLA (valve regulated lead acid) sealed batteries is to limit the charge voltage to just enough to charge the plate but not cause too much pressure buildup within the cell. When that happens the valve releases and the battery gasses, losing water in the process, drying the battery out and killing it. This is why flooded cell batteries are more durable, if they get overcharged and boil off water, it can be easily replaced. VRLA batteries are also called recombinant cells. That is, the hydrogen and oxygen recombine within the cell to form water again, that is why they don't need additional water as long as the recombinant design requirements are met. Proper float voltage is an important part of that process.

I have personally inspected dozens of stationary battery installations of lead acid storage batteries that are kept on charge 24/7 for 20 to 30 years. These are the same battery banks that back up large computer and telephone infrastructures to provide backup power should the AC fail. Proper float voltage is critical to keep each cell at full charge while minimizing water consumption. The float voltage (maintenance voltage) is critical in these installations, and determined by the alloy type and content of the plate, as well as the specific gravity of the acid put in the cell when manufactured.

Bob J

Past San Francisco Exide District Manager