Battery soc

colderthan

Hey, great forum. I live in northern alaska and the sun is below the horizon until the middle of jan.(solar panels not doing much). I have found that by reducing usage and a little help from my air x I can go about two weeks with out charging with the diesel gen. and still stay above 70% soc. The battery bank spends alot of time at the 80% to 90% soc range this time of year. By march they will be back to getting a full charge almost every day.
My question is, is this damaging the L16s by leaving them at a reduced state of charge so much of the time?

Paul

System2

Re: Battery soc

Hi Paul, I have L-16's from East Penn, and when I asked for info on proper battery care, they sent me the following:

"Float 13.8 – 14.1
Absorb 14.4 – 14.7
Equalize 15.0 – 15.3

Cut-off parameters per charge and equalize intervals are application specific and will vary dependent upon site specific characteristics such as temperature, days of autonomy, array to load ratio, etc, for this reason it is best to monitor the specific gravity reading on a regular maintenance interval and with this data the equalize frequency will be determined it is recommend that at least once per month the system be returned to 100% state of charge.

Specific Gravity reading values
1.265 - 12.75 indicates full charge
1.225 = 75%
1.190 = 50% system should never go below this value.

Variation in specific gravity readings from one cell to another of .20 indicates equalizing should be performed."

Also keep in mind that the above voltages are for 77 deg F temps and as the trmp of the batteries goes down, you must add voltage. I'll paste here what our well informed friend Jim / crewzer sent me as a clarification:

"For a 12 V battery (six 2 V cells in series), a common TC expression is -0.03 V/degree C. For a single 6 V L-16, it would be -0.015 V/degree C.

The minus sign is important. It means that charge voltage is reduced as battery temperature is increased, and visa-versa (= inversely proportional)."

I myself wouldn't feel comfortable going 2 wks between full charges, but tat's me. Hopefully some others will chime in too.
All the best
Wayne

nigtomdaw

Re: Battery soc

It sounds that u r not far from equilibrium add another Air X or run the genset longer between visits for a full absorbtion charge then an equalize charge and pop goes your peanut !

Standby for flak......:D

nigtomdaw

Re: Battery soc

Hi guys Im not an American, but Im learnin fast, if I offend anyone kick me up the jacksee (butt)

Happy Holidays to all ........!

BB.

Re: Battery soc

Ran across one site today talking about batteries and their "magic" number to avoid sulfation problems was to remain above 1.220 specific gravity...

A big question for you would be what is the temperature your batteries are operating at and are you temperature compensating the voltage/SPG readings...

And, you have the double edge sword--keep your batteries above 77F--your capacity goes up--but your life goes down. Keep your batteries below 77F, and your cycle life goes up, but capacity goes down...

-Bill

System2

Re: Battery soc

nigtomdaw wrote: »

Hi guys Im not an American, but Im learnin fast, if I offend anyone kick me up the jacksee (butt)

Happy Holidays to all ........!

Hey, I'm not an American either, I'm Canadian, so some of my words are spelled differently, but that's about it. Haha
If you think you offended anyone on here, I don't know when it was. I haven't seen anything in your posts to cause offense.
Cheers
Wayne

BB.

Re: Battery soc

I forgot to add, the other commonly accepted number is to never go below 1.225 SPG (or 75% SOC) to prevent sulphate hardening... (and at least one brand of AGM battery claims to be relatively immune to sulfate hardening---because it is a "starved acid" AGM????).

-Bill

PS: Sulfate/sulphate spelled multiple ways as an homage to our international friends (yea... that's it)....

crewzer

Re: Battery soc

My question is, is this damaging the L16s by leaving them at a reduced state of charge so much of the time?

Paul,

I believe your operational mode is indeed damaging your batteries.

Regularly recharging a battery bank to less than 100% SOC is sometimes referred to as “deficit recharging”. Research at Sandia Labs indicated that such an operational mode leads to reduced battery capacity and life. I would suggest you find a way to completely recharge your battery bank on a regular basis, i.e., several times a week in the winter.

The right charge voltages for your L-16 battery bank is another consideration. For one thing, I’d suggest double checking Deka’s numbers for a temperature reference (20 C/68 F? 25 C/77 F?) and adjust accordingly for battery temperature. For comparison purposes, here’s a link to Trojan Battery’s instructions for maintaining their batteries, including their L-16’s. Note that their target voltages are based on a 27 C / 80 F reference temperature.

See: http://www.trojanbattery.com/Tech-Support/BatteryMaintenance.aspx
And: http://www.trojanbattery.com/ProductLiterature/pdf/DeepCycleMaintenance.pdf

A potential complication of tall batteries like the L-16 is that the electrolyte can stratify in the cells. The result is higher SG electrolyte at the bottom of the cell, and lower SG electrolyte at the top. This can result in accelerated corrosion at the bottom of the battery plates as well as in false low SG readings – and therefore false low SOC readings – from samples taken at the top of the cells.

Based on additional Sandia research, Morningstar has a separate L-16 setting for their TriStar PWM chargers. The reference absorption voltage is 15.0 V, and the EQ cycle is every 14 days. Part of the intent of this aggressive voltage and EQ pattern is to vigorously mix the electrolyte on a regular basis to reduce stratification.

See: http://www.morningstarcorp.com/products/TriStar/info/TS_Manual.pdf

And, as Wayne indicated, cold batteries (ref 25 C / 77 F) require higher charging voltages.

In sum, I’d recommend you consider a more aggressive and regular charging and maintenance routine for your batteries. Keeping them full and healthy will take some work, but it should pay off in both useable capacity and in battery life (discharge/recharge cycles). Don't forget to vent the batteries to the outside when they're in absorb- or EQ charge mode.

HTH,
Jim / crewzer

colderthan

Re: Battery soc

Thank you for the great information. My batteries are in a heated area and I use temp. comp when charging. The battery bank is 1290 AH charged with a trace 2412 and a iota 90 amp charger for bulk, finish charging with the trace only. I EQ charge about once a month. Sounds like I need to get more agressive with the charging. Man I hate to burn diesel!!!
Thanks again,
Paul

System2

Re: Battery soc

Group,
does "vent the bateries in absorb and EQ" mean open the caps on top of the batteries?
Is that because of gas bubbles?
how about during bulk charging?
anyone?

System2

Re: Battery soc

Hi Jim.

I have got my lecture already but it doesn't hurt hearing it twice!
But I am not too sure I understand what this means.......

Don't forget to vent the batteries to the outside when they're in absorb- or EQ charge mode.
HTH,
Jim / crewzer[/QUOTE]

Does it mean open the caps on the top of the batteries?
Why is that?
Is it because gas bubbles are forming? Should I bulk charge also with caps on or off?

BB.

Re: Battery soc

Generally, venting the batteries means letting the hydrogen gas out and bringing fresh air to prevent an explosion.

I think people used to say to loosen the caps to vent pressure from a flooded cell battery (if the caps are good, just leave them on)--but in any case, you don't want to remove the caps and leave them off--the bubbling acid will get on the top of the battery and make a mess (plus you will lose acid instead of water).

-Bill

System2

Re: Battery soc

That reminds me, I must remove and wash up the caps on my battery bank. I've noticed what looks like a bit if a dark gray buildup on the underside of the caps, and it might, just might, plug off a vent. The caps on mine have a rubber type sealing ring and the only time the caps are off is to check fluid level, or take SG readings.
Cheers
Wayne

crewzer

Re: Battery soc

But I am not too sure I understand what this means.......

Don't forget to vent the batteries to the outside when they're in absorb- or EQ charge mode...

Does it mean open the caps on the top of the batteries?
Why is that?
Is it because gas bubbles are forming? Should I bulk charge also with caps on or off?

As Bill described, venting the batteries means exhausting the hydrogen (and oxygen) gasses released from flooded-cell batteries while they’re in the absorb- or eq stages. Hydrogen gas is flammable/explosive in sufficient concentration.

Venting technique typically involves housing the batteries in an enclosure and using a fan to vent the enclosure to the outdoors. Check this link for related discussion and products: http://www.solarseller.com/battery_box_power_vent_by_zephyr_industries.htm

Battery cell caps typically include a breather hole that will allow them to vent while being charged. Accordingly, you don’t need to open the caps/manifold while charging the batteries. For example, Trojan says to make sure the caps on their batteries are tight when being charged.

See: http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/Charging.aspx
And: http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/Equalizing.aspx

HTH,
Jim / crewzer