Charging batteries in series with 20 amps

[Tony Stewart]

• Heat kills batteries such they have short life in Arizona, Nevada etc.
• Excess duration when low SoC also kills battery life.
• Weakest cell kills the unit unless you are using a trickle charger, as fast charge rates will evaporate electrolyte and if not replenished accelerates the weak link.
• deionized water and distilled water are not always the same, but if low in ionic contaminants, will not degrade cell as fast as tap water.
• Unless cell design is weak and plates warp or corrode, sulphation is #1 cause of battery death with low S.G. and higher ESR and lower Ah capacity. Then ? ns >10A pulse circuit will resonate and breakdown lead sulphate cyrstals from harmonics of impulses, while only drawing a couple watts average. anything >20kHz. with low RdsOn and pulse steering diodes.. However if you put on your car or truck, it will interfere with AM rception on weak signals.

 

[tcmtech]

TCM don't get me wrong. You are very knowledgeable person with a load of practical experience and some great ideas and I often learn a lot from your posts. But you do seem to get a bee in your bonnet and I can't see why.

spec

You must be reading far more into what I post than what I am implying.

About the only time I get wound up is when I see someone obsessing over a trivial issue when there are far greater more concerning issues in the overall system that will cause the problems they are so worried about than what they are focusing on.

Sort of in the lines of the saying,

"You're concerned about finding the best way of stopping the draft through a keyhole when it's 20- outside when your house is missing all its windows. "

or as I have come to see things in electrical terms

" You're concerned about how much power a USB charger uses in standby mode while you have your central air running to combat the broken electric heater that won't shut off. "

As in look at the bigger picture of the overall workings and faults of the system before worrying about the tiny deatials.

That's what bugs me.

 

[Tony Stewart]

• They are the same, except that one is made by distillation and the other by deionization and might have slightly more dissolved ions than distilled. Same water obtained through reverse osmosis would probably be called deionized as well since there is no distillation in the process.

• D distilled water can still have ionic contamination evaporated and condensed but generally ok but more expensive.
• RO reverse osmosis removes heavy metals but not all sub-micron minerals.
• DI removes sub micron ionic contamination which tend to be insulators which otherwise add to electrode resistance.
• RO+DI or D + DI is best for batteries, but not for humans as minerals are essential to life.
• Some distilled water indicate low Sodium, which is also ok.

 

[SimonTHK]

My so far conclusion to this:
Yes it would be nice with a charger that is able to charge 36v batteries with microprocessor controlled voltage outputs for normal charge, float, bulk and equalize. This is not at all all chargers that can do this, especially not old ones.
The 6 chargers I have used works great and "buff up" those "bad" cells. Today I measured exactly 6,88v on ALL 6 batteries...exactly. I do like that. With 60 amp load, the performance was FAR better than with the old 36v charger, though still abit different in voltage (most at 6v and two at 5,8v with load). These are great great numbers compared to before.

Also I tested charging with the old charger after I have used load, after I had charged with the 6 chargers... (no bulk, no equalize, just cut off at 41,5v). The charger now charged the batteries more equally than before. Before I could measure over 7v on some batteries, 5,4v on others. This was by far better now. So the 6 charger´s made the old single charger, perform better again.

So: 1 charger that charges a series setup, is great if it can do bulk (which means slightly overcharge to reach better potential for both good cell´s and cell´s that is behind other cell´s). Equalize only means, that flooded cell´s like to get shaken in the bottom of the battery liquid. The bobbles help with this. Equalize has to be timed around 4 hours. Equalize can help batteries maintenance, keep better performance, and longer lifetime, but it aint mandatory, but advised.

More charger´s is great for keeping them all up. 6 pieces of 6v 20 amp charger´s, one for each battery with bulk, equalize and float would be best of all. This ofcourse aint gonna happen in normal procedures, when you can just use one single. Also the quistion ofcourse is, "how often will you see cell´s acting differently when you have one single charger, with all the good stuff going on, microprocessor charge, bulk, equalize, float?).

Also I did figure out, that you can use a normal laboratorie power supply to do equalization, if you are just gonna do it few times a year. Remember to use timer.

 

[Tony Stewart]

(no bulk, no equalize, just cut off at 41,5v). I think this is the accelerant of the problem.

While rapid charging is not very efficient, it doesn't allow time for the undercharged batteries to reach full charge if one cell is overcharged. If instead, stage 2 tickle charge or Slightly lower CV with declining current to near zero would allow the lower voltage charging cells to reach a higher potential. The weaker cells reach overvoltage sooner due to higher ESR, while the lower ESR cells which are better are at a lower voltage. Then when high load occurs, the overvoltage cells, with high ESR drop to a lower cell voltage probably due to 1 of four 1.5V cells.

I call it the weakest link reaction, where capacity and ESR are inversely related with aging and state of charge. Equalizing is faster with independant Voltage chargers, but still possible with 3 stage rapid charging with current sharing, where stage 2 prevents the weaker overvoltage cells from being aged faster with more current and the others to catch up to full charge with a slower rate of charge.

Unlike capacitors which would simply all integrate current into voltage and the weakest or lowest C value cap would charge up the fastest, batteries have non-linear properties below 10% and above 90% SoC. Below 10% ESR rises rapidly, and when over charged and overheats, ESR drops and overcharging accelerates.

This is a hand waving experience, I don't have data readily avail to back up, but is consistent with my experience. Hot batteries have more power but age much more rapidly. dead batteries have like worn caps low capacitance and high ESR.

You might have around 100k Farads in each battery, but the S.G. and ESR is what dictates aging. Smart chargers have temp. compensated 3 stage controls.

 

[Tony Stewart]

Just found this patent image which supports my experience on nonlinear battery curve.

 

[SimonTHK]

(no bulk, no equalize, just cut off at 41,5v). I think this is the accelerant of the problem.

While rapid charging is not very efficient, it doesn't allow time for the undercharged batteries to reach full charge if one cell is overcharged. If instead, stage 2 tickle charge or Slightly lower CV with declining current to near zero would allow the lower voltage charging cells to reach a higher potential. The weaker cells reach overvoltage sooner due to higher ESR, while the lower ESR cells which are better are at a lower voltage. Then when high load occurs, the overvoltage cells, with high ESR drop to a lower cell voltage probably due to 1 of four 1.5V cells.

I call it the weakest link reaction, where capacity and ESR are inversely related with aging and state of charge. Equalizing is faster with independant Voltage chargers, but still possible with 3 stage rapid charging with current sharing, where stage 2 prevents the weaker overvoltage cells from being aged faster with more current and the others to catch up to full charge with a slower rate of charge.

Unlike capacitors which would simply all integrate current into voltage and the weakest or lowest C value cap would charge up the fastest, batteries have non-linear properties below 10% and above 90% SoC. Below 10% ESR rises rapidly, and when over charged and overheats, ESR drops and overcharging accelerates.

This is a hand waving experience, I don't have data readily avail to back up, but is consistent with my experience. Hot batteries have more power but age much more rapidly. dead batteries have like worn caps low capacitance and high ESR.

You might have around 100k Farads in each battery, but the S.G. and ESR is what dictates aging. Smart chargers have temp. compensated 3 stage controls.

Well ty
I did read this 3 times now. I dont know the terms ESR or CV. I do understand what you write, and these are also my observations, that cell´s can be weaker, and the weakness can apply greater easier with bad charger.
I guess you agree, that single charger´s are quite great? The typical CTEK intelligent charger, doesnt provide equalize, but I guess it delivers all the other stages. The 6 I use right now... I need to read up on them, I dont know how many stages they have, or if they are simpler because they were crazy cheap...

In the future, I am gonna use 1 single bad ass charger with 5 stages: Initialization, Bulk, Absorption, Equalization, & Float
If money is no prob, I am gonna use them on each battery!!!
Also I could do it half way, use 3x12v charger´s on 6x6v batteries.

On AGM from like 20-100 AH, I cant see why I should use anything else than intelligent cheap chargers on each battery, not equalizing, not having the need to benefit from the serial high ampere charging.

 

[schmitt trigger]

You can also mix a teaspoon of it with your distilled water and drink it if you ever get into a pedantic debate over how to charge your batteries, whilst totally ignoring the discharge and general working cycles (IE, primary battery damaging actions) and their effects on said batteries, that end up giving you heartburn.

Is it pedantic to a provide a safety tip? Really?

I thank my lucky stars that I was carrying some bicarbonate with me, when some idiot did not clean an acid spill on a battery surface. My shirtsleeve cuff soaked the acid, which immediately started to burn my wrist.

It was a cold day, so I had a coat, sweater and fully buttoned shirt. I poured the bicarbonate on me, which neutralized the acid enough to allow me to remove all my garments. The acid-soaked cuff also brushed my face when I was hurriedly removing my shirt.

Even with the bicarbonate, I developed a two inch blister. It could have been far worse.

 

[tcmtech]

Okay, Fine. Don't use baking soda and water for heartburn next time.

If you can take what I say out of context then I can do it too!