shallow cycling, deep-cycle batteries

[Sunking]

I haven't seen a bulk charge occurring in two years, goes straight to absorb in the morning. Thanks to my cheap CC, it keeps trying to push a full absorb voltage (58V) into the batteries, even when they are fully charged, for the full two hours that has been set for absorb mode. That results in regular over voltage disconnects - in effect giving a "Bounce" charge, which I understand old CCs used to do.

Would that bounce charging be similar to equalising? I use AGM batteries so am not meant to perform regular equalisation charges.

When the CC goes into Float, everything works fine, no bounce and no disconnects.

If you are using AGM,Stratification issue goes away taking care of that problem. Sounds like you have a far bit of battery caoacity, and are not using much. One thing you can do is just the turn panels off for a day or two so as ti discharge down to 50% to make sure it is working right.

Sounds to me like you are not discharging deeply enough to see an Bulk charge.

[carilchasens]

Thanks.We installed our Rolls S-550s this summer, so I assume they are still formatting. Until recently, they were going through bulk-absorb-float every day, although our use was quite light for the size of the bank. Does the full bulk-float-absorb (Midnite Classic) mean that there is no worry? This week, fall rain weather has made a respectable call on the batteries and northern winter is coming - we do need the capacity.

[smily03]

Cool, makes sense. Thanks!

[inetdog]

Can stratification be an issue for starting batteries? (letting my curiosity run a bit today :P)

Depends on how they are used. Starting batteries (ab)used for PV can stratify.
In normal vehicle use they get sporadic fast charging and some gassing during normal use, as well as vibration.

[Sub]

Chronic shallow cycling results in stratification of electrolyte, insufficient charge time to dissolve sulfate crystals, and overall capacity loss Not necessarily a big problem as all that can be maintained to acceptable limits with more frequent Equalization Charge.

If you are only discharging 10% over night, your charger will not go into Current Limit aka BULK MODE. Instead going right into a Constant Voltage mode Absorb, then Float. The battery never receives full charge current, it just basically gets slowly Trickled charged which is fine, but does not stir up electrolyte much or have enough time to dissolve sulfate crystals.

Essentially you are just Float Charging the batteries which is the best method for charging batteries and extending Shelf Life. However the operating nature of Solar does not lend itself to Float Charging. So assuming you have the battery properly Formatted and the plates Formed, you can shallow cycle, but will have to EQ more frequently. It also indicates you have a very RARE DISEASE. called Batteryoutwazoo or your battery is too large.

Hi Sunking, I'm thinking I must have oversized my battery bank a couple of years back. What lead me astray was that we only use things like the vacuum cleaner, washing machine, toaster, etc, when the sun is shining.

I have a 580ah battery bank which I calculated was about right to allow for 3 days autonomy using 80ahs a day, but that calculation did not take into account our frugal use of high wattage appliances.

In summer we seldom discharge to more than 20 - 30%, and in Winter we occasionally go down to nearly 50%, at which point I charge up with the genny.
I haven't seen a bulk charge occurring in two years, goes straight to absorb in the morning. Thanks to my cheap CC, it keeps trying to push a full absorb voltage (58V) into the batteries, even when they are fully charged, for the full two hours that has been set for absorb mode. That results in regular over voltage disconnects - in effect giving a "Bounce" charge, which I understand old CCs used to do.

Would that bounce charging be similar to equalising? I use AGM batteries so am not meant to perform regular equalisation charges.

When the CC goes into Float, everything works fine, no bounce and no disconnects.

[smily03]

Can stratification be an issue for starting batteries? (letting my curiosity run a bit today :P)

[Sub]

Totally ignorant question here... To prevent stratification, could you just stick your batteries in the back of the truck and drive around occasionally? I know it wouldn't be practical, I'm just curious about feasibility

Hmm, I don't know, but not very practical since my batteries weigh 70kgs each!

[inetdog]

Totally ignorant question here... To prevent stratification, could you just stick your batteries in the back of the truck and drive around occasionally? I know it wouldn't be practical, I'm just curious about feasibility

Depends on your roads. The stratification based on electrolyte density is really resistant to mixing just by sloshing around. Gas bubbles, on the other hand, mix things very well.
Instead of driving them around in your truck you could outfit them with dip tubes and nitrogen bubblers. Not too practical though unless designed into the batteries at manufacture.

[smily03]

Totally ignorant question here... To prevent stratification, could you just stick your batteries in the back of the truck and drive around occasionally? I know it wouldn't be practical, I'm just curious about feasibility

[Sunking]

Chronic shallow cycling results in stratification of electrolyte, insufficient charge time to dissolve sulfate crystals, and overall capacity loss Not necessarily a big problem as all that can be maintained to acceptable limits with more frequent Equalization Charge.

If you are only discharging 10% over night, your charger will not go into Current Limit aka BULK MODE. Instead going right into a Constant Voltage mode Absorb, then Float. The battery never receives full charge current, it just basically gets slowly Trickled charged which is fine, but does not stir up electrolyte much or have enough time to dissolve sulfate crystals.

Essentially you are just Float Charging the batteries which is the best method for charging batteries and extending Shelf Life. However the operating nature of Solar does not lend itself to Float Charging. So assuming you have the battery properly Formatted and the plates Formed, you can shallow cycle, but will have to EQ more frequently. It also indicates you have a very RARE DISEASE. called Batteryoutwazoo or your battery is too large.

[carilchasens]

Using these keywords, I am only finding references to the initial phase of deepcycle battery use. I particularly want info on the process that can harm batteries in cycles of less than 10% discharge.

[carilchasens]

I would like to get the best life possible from my battery bank, but also our needs through out the year are extremely variable, so at times we shallow cycle.

[carilchasens]

Those are the kind of questions I like. Someone who is willing to do their own work and look things up.

The words you are looking for is FORMAT and PRIME. Start your search here.

The references I get with this are to the initial wearing-in phase of a deepcycle's life. So far I haven't found anything about the deterioration that specifically occurs in shallow cycles, and the process of reversing that harm by occasionally cycling deeper. Is there a word for the sulfation or whatever it is in shallow cycles?

[inetdog]

You should probably include a few more keywords, like BATTERY for example.

[ButchDeal]

format a prime number?

(actually the main hits are hard format a Galaxy grand Prime)