SLI battery maintenance

[RDMueller]

Most of the battery discussion that takes place here obviously tends to focus on deep cycle, AGM, 6v, etc. I've learned a ton over the years and feel fairly knowledgeable when it comes to my house batteries. But I haven't given as much thought to my SLI batteries other than checking electrolyte level periodically.

The 2 SLI batteries in my truck are a bit over 6 years old. Based on that alone, they are likely nearing the end of their lives. When checking the electrolyte today I decided to also check the SG. All cells of both batteries were low. Average was 1.245. Lowest cells were 1.230.

Based on my deep cycle knowledge, I thought that desulfating them might buy them some extra time. By the way, they were starting the truck just fine before doing anything. I applied 16.2V at max 2A (roughly 3% of C for these batteries) for about an hour to each battery separately.

Afterwards, checked the SG again and it was nearly identical. Maybe a slight improvement in a few cells, never more that a .010 improvement though. What was different though is that the electrolyte was no longer clear. It had a brown tint, probably from millions of tiny rust particles suspended in the electrolyte. I've never seen this in my deep cycle batteries.

Anyway, I put them back in the truck and it starts just fine. Not sure though if what I did was a good idea. Probably not a big deal either way since they are likely due to be replaced soon anyway. Just wondering if anyone does ever desulfate their SLI batteries.

Obviously most car owners don't even know what desulfate means. They just drive until one day the car won't start and then they buy a new battery. But, in the interest of maximizing the life of an SLI, is it a good idea to desulfate or at least equalize them periodically? I'd love to hear what the battery experts think. As usual, thanks in advance!

[brulaz]

Don't need a Trik-L-Start as the trailer's 24V battery bank -> 13.2V converter is one-way already.

But if some idiot pulls the 7 way, or my trailer's batteries get stolen (like last year), my truck's two batteries are guaranteed to die in 5 weeks or so (like last year).

Think I'll just disconnect the truck's batteries. A pain, but safer.

[time2roll]

Yes a Trik-L-Start installed across the isolation relay.
Works like a charm. Power only moves one way when the truck is off.

[pianotuna]

Hi,

I have a trik-l-start from the house bank to the starter battery. It works well. The starter battery was fine--but I wanted to go to AGM so I replaced it after 8 years.

brulaz wrote:
Oh, you use the trailer's solar to maintain your truck batteries in storage? I've heard pros and cons on that. Can't decide ...

[brulaz]

time2roll wrote:

brulaz wrote:
But deep discharge does kill them. Happened in storage once, they were dead as a doornail. Didn't even try to repair/equalize, they were replaced.

Yes I killed my 7 yo start battery earlier this year by letting it discharge.
Forgot to put the 7 pin back in after using the truck.
dead dead dead and no point to attempt revival.

Oh, you use the trailer's solar to maintain your truck batteries in storage? I've heard pros and cons on that. Can't decide ...

[time2roll]

brulaz wrote:
But deep discharge does kill them. Happened in storage once, they were dead as a doornail. Didn't even try to repair/equalize, they were replaced.

Yes I killed my 7 yo start battery earlier this year by letting it discharge.
Forgot to put the 7 pin back in after using the truck.
dead dead dead and no point to attempt revival.

[MEXICOWANDERER]

My Grumpy Opinion

US Battery pays their engineers a fraction of what Trojan and Rolls & Surrette pays their engineers.

IHMO US Battery engineers are overpaid

PTUI

[red31]

Rolls suggests 5 A per 100 AH of battery capacity
The Mex trick of adding a 12v light inline, like a 60w, I thought was to maintain the current while eq, I thought it was along the concept of the current is the same in the circuit and the bulb would force 3-4 amps in the circuit. Bologna?

Also the reasoning for min 100w solar or 5A per 100ah cap. ?

Goofy reg volt controll in chevy Colorado, I use manual charger that reaches 15.3 overnight on occasion, sealed. Other times I use a 60w PV and controller to hit with 14.6v on a sunny day.

[brulaz]

RDMueller wrote:
The thing I'm still wondering is if equalizing is even something you should do to a starting battery. Especially if it was never deep cycled, i.e. nobody ever left the dome light on overnight, never even sat in the vehicle for an hour listening to the radio with the engine off. Only used for starting duty it's entire life. Would there be any reason to equalize, or would it do more harm then good, especially considering the paper thin plates an SLI has?

Under these conditions, I'm guessing it is not sulfation that eventually kills the battery. More than anything, it's probably heat. That's a pretty punishing environment, under the hood. Maybe why we are starting to see some cars with the battery in the trunk.

I've certainly never done it.
My truck's alternator charges at 14.1V, hopefully that's enough.

But deep discharge does kill them. Happened in storage once, they were dead as a doornail. Didn't even try to repair/equalize, they were replaced.

[RDMueller]

The thing I'm still wondering is if equalizing is even something you should do to a starting battery. Especially if it was never deep cycled, i.e. nobody ever left the dome light on overnight, never even sat in the vehicle for an hour listening to the radio with the engine off. Only used for starting duty it's entire life. Would there be any reason to equalize, or would it do more harm then good, especially considering the paper thin plates an SLI has?

Under these conditions, I'm guessing it is not sulfation that eventually kills the battery. More than anything, it's probably heat. That's a pretty punishing environment, under the hood. Maybe why we are starting to see some cars with the battery in the trunk.

[brulaz]

pianotuna wrote:
Brulaz,

I no longer know where I got the information originally. But I was reassured when Mex came along and said 5 amps per 100 amp-hours of storage for equalization/desulfation. It may have been from my Blue Sky solar charge controller manual.

One does need to monitor the temperature of the battery and keep it under control.

For my 215 Ah bank, 5% would be 10.75A.

I just equalized yesterday, it started at about 10A and went down to about 5A after an hour or so, and stayed there until I pulled the plug.

Just looked at the US Battery charging docs again. They don't mention Amps but do have a graph showing current declining during equalization down to 3% of C/20 (6.5A for my bank).

[RDMueller]

MEXICOWANDERER wrote:
What you are seeing is shedded suspended negative plate material lightly coated with antimony. Normal but it's like seeing an old man clutch his heart and then smiling "Oh good, it has passed".

Get your plans together. If you have tow service great. If you don't, muse how difficult or easy a no-start in some parking lot would be. This would be a perfect scenario for a (powerful for a diesel) emergency jump start battery. At least carry TWO GAUGE jumper cables if your vehicle is a diesel. Your vehicle is waiting for you to park in a remote parking lot at night in a rainstorm before the batteries go belly. Typewriter paper, thin starting battery plates just about show their ribs when brand new. A forced diet of plate shedding means the end is near.

I'm with you Mex. They are clearly nearing the end of their lives. Even if I gained an extra couple of months, at what cost? Almost certainly left stranded some morning in January when the temps are in the single digits. 6 years was not bad at all.

[RDMueller]

landyacht318 wrote:
2 amps was able to get the battery to 16.2v?

My flooded marine batteries required about 5 amps per 100Ah after hours at 14.4-.7, to get upto 16v.

I've also EQ's a not very old flooded group 27 starting battery that was deepcycled often and rarely charged anywhere near full, and it required 4 amps to get to 16.2v and eventually settled to 2.5 amps before amps required to maintain 16.2v began rising again.

Was never able to restore Sg on that battery and it is apparently still continuing to be deep cycled over a few week timespan by someone who repeats a battery's age over and over as to whether it is still good or not..

The EZ red and similar plastic hydrometers say they are temp compensated, but I do not believe it. During EQ charging the electrolyte gets warmer. My float readings with a turkey baster glass style hydrometer would often stay the same, but when factoring in the temp compensation, the EQ was still increasing SG and i would keep going until it did not or amps required to hold 16v would start rising instead of tapering.

Yes, I set the charger to 16.2 limited to 2A. Voltage steadily rose over a period of 15 min or so before it reached 16.2, then amps started to taper as expected. After an hour it settled at about 1.3A which is when I disconnected.

[pianotuna]

Brulaz,

I no longer know where I got the information originally. But I was reassured when Mex came along and said 5 amps per 100 amp-hours of storage for equalization/desulfation. It may have been from my Blue Sky solar charge controller manual.

One does need to monitor the temperature of the battery and keep it under control.

[brulaz]

pianotuna wrote:
5% would be a better number than 3%.

Don, where do these Amperage % numbers come from?

All I've seen is Equalize for 1-2 hrs (USBattery), or until Sp.Gr. stops rising (Trojan), or Sp.Gr. is constant for 45-60min (Rolls)