winter battery performance

BB. · December 2011

Re: winter battery performance

vtmaps wrote: »

...they advertise their "alpha plus paste electrolyte"...

Just out of curiosity, where did you see that phrase--At this point, I can only find that exact wording in your post on the WWW...

-Bill

icarus · December 2011

Re: winter battery performance

I have never seen the viscosity of electrolyte change with temp, even as cold as-30. Me thinks something else is going on here.

Tony

westbranch · December 2011

Re: winter battery performance

Bill, it's here
http://www.trojanbattery.com/pdf/TRJN0158_T2CorpColl4PLR_001.pdf

page 3

BB. · December 2011

Re: winter battery performance

I guess I must be going blind... I don't see the word "electrolyte" anywhere on that page... Searching for electrolyte does not return anything on page three--But it is possible the phrase is in a graphic that cannot be text searched.

-Bill

Vic · December 2011

Re: winter battery performance

Of course, the viscosity of the electrolye does change with temp changes, but the change is fairly small. More ovbious stuff, this is why there is that temp comp for temp delta from 77-80 degrees F.

Would sure surprise me that one could observe the difference in the behavior of the electrolyte twix 80 F and, say, 35 F on a fully-charged battery, or nearly so.

We are in a fairly hospitible climate. It is 61 F, now. The overnight low was 38 F, and the batts are in Float, and read 14 C about 57 F (my mental calc). SSsoooo, I have little experience with off-grid FLA that are COLD. Doing batt maint today.

Best wishes for Christmas and the Holidays. Vic

Vic · December 2011

Re: winter battery performance

BB, Have not read any of those pages, but bet that the Mfg is stating a "unique" process for manufacturing the plate and paste that is used to fill the grid,

Every manufacturer has a "new and BETTER" Technology. That's what one does when products like FLAs all use the same basic technology as was used in the 1850s. Whatta I now ? Just guessing. HH, Vic

BB. · December 2011

Re: winter battery performance

I agree, there are changes to the paste, and to the separators (more ribs, something that prevents antinomy from migrading between positive grid and negative plate). Nothing mentions any changes to the electrolyte (that I could find).

-Bill

vtmaps · December 2011

Re: winter battery performance

vtMaps wrote:

they advertise their "alpha plus paste electrolyte"

BB. wrote: »

I don't see the word "electrolyte" anywhere

OK, neither do I. I assumed that because on their illustrations of the battery construction on page three of:
http://www.trojanbattery.com/pdf/TRJN0158_T2CorpColl4PLR_001.pdf
They have their "separator with thick back web" applied directly to the plates and the paste is where the electrolyte should be. They say that the separator keeps the acid channels open. As I mentioned: "I have often wondered about these trojan batteries", but I'm not to sure that my interpretation of their illustrations is correct. I sent a query to their tech support. I don't expect to hear back until after the holidays, but I will update you when I do hear from them.
--vtMaps

Derik · December 2011

Re: winter battery performance

I didn't mean to give the impression that they are gel like and slushy which is not the case. It looks just slightly thicker than water but when the electrolyte is warm it seems thinner than water. It takes more pressure with the bulb to get the electrolyte up into the hydrometer. The hydrometer is also stored in the battery box so it is cold as well.

My batteries were not fully charged when I last checked the SG, it was 1.225-1.230
I am not there at my cabin now but I suspect after a week of sun they have come up close to 1.250 or so.

In the spring summer and fall I add water to my batteries due to the gassing and mixing of the electrolyte. I do not have to add water in the winter even with the absorb set to 5 hours.

vtmaps · December 2011

Re: winter battery performance

Derik wrote: »

In the spring summer and fall I add water to my batteries due to the gassing and mixing of the electrolyte. I do not have to add water in the winter even with the absorb set to 5 hours.

that is a sure sign that your batteries are undercharged. Do you know about temperature compensation? You need higher charging voltages in cooler temperatures. Our host has a good battery FAQ that explains it. If your charger does not have a battery temp sensor, you should manually raise your voltage. Don't forget to lower it again in summer. If you your charger can't be adjusted, you are causing permanent damage to your batteries.
--vtMaps

icarus · December 2011

Re: winter battery performance

Here are the battery links mentioned:

http://www.batteryfaq.org/

http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

Merry Christmas to all,,

Tony

Derik · December 2011

Re: winter battery performance

My outback system compensates for temperature. My panels put out over 2000 watts and I see up to 80 amps going into my batteries when needed the norm is about 60 due to the fact that I produce way more energy than I will ever use. Once my system reaches absorb when the sun is high that 60 amps or much less is all that is needed to keep my batteries at 29.6 volts for 5 hours.

I am sure my batteries will not live as long as ones that are backed up or charged with a generator to keep them at 100% 12 months a year but I can keep mine at 90% 3 months a year and near 100% the rest of the year then I am happy.

BB. · December 2011

Re: winter battery performance

Derik wrote: »

My outback system compensates for temperature. My panels put out over 2000 watts and I see up to 80 amps going into my batteries when needed the norm is about 60 due to the fact that I produce way more energy than I will ever use.

I am not sure, but you may be conflating Maximum Power Point Tracking and the fact that Vmp rises as panels get cooler (Pmax=Imp*Vmp; Vmp rises as panels get cold and Imp falls a tiny bit when panels get cold, so overall Pmax increases with cold panels)...

With the use of a internal sensor or external remote battery temperature sensor measure the temperature of the battery and compensate the charging voltages based on battery temperature (hot batteries need lower charging voltages, cold batteries need higher charging voltages).

-Bill

Derik · December 2011

Re: winter battery performance

I was refereing to the battery temperature sensor that adjusts the charge voltage on my Outback System. I only included my panel output and amps produced to illistrait that my batteries are getting sufficiently charged.

I wasn't trying to complicate this post I only wanted to let the original poster know that my experience from winter to summer is that yes the cold does affect the batteries capacity, they don't charge up as high, gas as much and the electrolyte actually gets thicker!!!

Derik · December 2011

Re: winter battery performance

waynefromnscanada wrote: »

In the same way that cold water is thicker than warm water. Measurable with special instruments, but unnoticeable in everyday usage.

We aren't all lucky enough to live in Nova Scotia and here in the Southern Republic of California at 3,400 feet we can have temperature swings of 70-80 degrees from winter to summer. Our socialized medicine (Obama Care) hasn't kicked in yet but as of 2010 ( my last eye exam) I had 20-20 vision which allows me to see the slowness of the electrolyte and thicker properties as I draw it up the hydrometer to check for SG or SOC. No special instruments required!

Merry Christmas

waynefromnscanada · December 2011

Re: winter battery performance

All the best my friend. I wish you the best of luck with your batteries.
Peace be with you.

NWCabin · December 2011

Re: winter battery performance

Samuel,

You've got a great blog. I'm just starting out myself, but maybe these are ideas that the old pro's will endorse.

I've read parts of this thread over a few days, so sorry if I'm repeating something already ruled out.

From reading the blog it sounds like batteries were added over time, and now there are some over a few years old that also went through the deep discharge to 33% SOC that you mentioned. With them in parallel to a bus bar, it would be straight forward to disconnect some of the sets and see if they hold a charge or not. I'd check the oldest ones one pair at a time by disconnecting them and letting them sit overnight and see if they drop voltage. Like I mentioned, I'm new to this, so this is internet advice and needs to be qualified, but it seems to me that it be one way of going through the batteries, since that seems to be what everyone is identifying as the most likely suspect.

In my area, you can take batteries into get them tested for free. Again, since you wouldn't disable your system by taking out a pair or two at a time, maybe this is another option.

As far as other suspects, I know for me, I didn't consider the inverter draw on my system. I'm using a Suresine 300, which uses 450ma when it's on, but this adds up to 10.8AH a day since I have it set up to be on all the time. This time of year, if you're only getting a few amp hours out of your panels, maybe you could turn the inverter off when you're not there, if you're not already doing that.

silvertop · December 2011

Re: winter battery performance

I keep my batteries indoors in a vented box and room temp. does help. I have a 2 Inch vent but have not yet installed my power vent so I am backdrafting some cold. The power vent will close off the cold untill I get to Absorb Voltage. This way the batteries wont derate. Something like this might help...........

samuel · December 2011

Re: winter battery performance

Merry Christmas! I have an update of sorts. My presence at the cabin, where the off-grid system is located, is both limited and intermittent. My Dad has reported, via text message (cell phone reception is another issue we have) that the current state today was:

Dec 27, 9:17 am, CE 85, 20 amp load, 11.92 volt, 37 degrees
Dec 27, 10:50 am, Absorb 70 amp, vic 14.92 volt, xantrex 14.9, Soc 100

(Exactly as he texted)

CE represents amps consumed, and is supposed to be 'amps consumed from 100% SOC'. After looking at the reports from the ol' man and the data I've collected from specific gravity I think two things are at play and I'm willing to say "stand back! I'm going to try science" and advance my conjecture to a hypothesis and test it at some point. What I suspect is happening:

The batteries are holding less Ah in winter due to the cold
The battery monitor is not accurately reporting the SOC of the batteries (I'll explain)

I suspect, though I can't measure this unless I spend several consecutive days at the cabin, that the poor PV conditions are partially to blame. In Summer I can charge at 2.5 - 3% of the battery bank Ah from the PV array. Under this condition I've observed adequate bubbling and accurate battery monitor readings (double checked with spec. gravity readings). In summer the battery bank reaches 100% each and every week. In winter the charge current is down to <1% of the battery bank Ah from the PV array about 80-90% of the time. Also, we have about 1 amp continuous draw from some LED security lights that are always on. The cause for the battery monitor error is probably due to the unfavorable PV conditions and our LED electric load. I'm willing to bet that the low charge current in winter is barely doing anything to charge the batteries and is simply getting wasted due to the internal resistance of the batteries - sort of like trying to push a stalled car, you need so much force just to get the car moving and additional force to keep the car moving. The battery monitor only measures the force (so to speak) and if the PV panels aren't overcoming the resistance then the ledger is getting unbalanced. To illustrate this with some made up numbers:

45 amps charge current = 3% battery bank Ah charge rate and maybe 90-95% efficiency
8 amps charge current = 0.5% battery bank Ah charge rate and maybe a meager 30-60% efficiency

Since the battery monitor cannot account for efficiency changes it is easy to 'lose' Ah when 100Ah travels to the batteries but only 50Ah or so gets capture by the batteries - this has not been proved or directly measured, but it would account for my problems measuring the SOC of the battery bank.

How to test my hypothesis (list item #1 & #2):

Full equalize charge (confirm via spec. gravity +/- temp. correction if needed) followed by a 20Ah current to draw off 100Ah. Then compare/recrod everything - Volts, current, spec. gravity and whatever else the system monitors will tell me. Then apply some simple math: Use spec. gravity to calculate a SOC; then take (%SOC/100%) x 100Ah = battery bank Ah. Repeat in warm and cold weather.

Outcomes:

adjust Ah of battery bank to match "real world results" and observe the effects of temperature on battery capacity
if after adjusting battery bank Ah, SOC is accurately reported by the battery monitor this says that undercharging in winter has skewed the accuracy of the battery monitor
for winter we will recharge once the battery monitor reports <11.9V under a 20-25A DC load when between 30-40°F, this is about 55% for our system and a common load at night in the cabin. Voltage appears to be the most accurate indicator for winter. In summer the battery monitor appears to be accurate

I'll share what I find out when I get a chance to get back to the cabin.

vtmaps · December 2011

Re: winter battery performance

Derik wrote: »

the cold does affect the batteries capacity, they don't charge up as high, gas as much and the electrolyte actually gets thicker!!!

icarus wrote:

I have never seen the viscosity of electrolyte change with temp, even as cold as-30. Me thinks something else is going on here.

vtMaps wrote:

I sent a query to their tech support. I don't expect to hear back until after the holidays, but I will update you when I do hear from them.

Well I heard back. This is from the (Trojan) horse's mouth:

The electrolyte does not get thick. The electrolyte can only increase or decrease its density, which is the "specific gravity".

They also confirmed that the "alpha paste" is NOT the electrolyte (despite the somewhat confusing illustration in their literature.
--vtMaps

niel · December 2011

Re: winter battery performance

with charge rates of 1% and 3% these are basically at or just above float charge rates and is not going to do much for your trojans that actually need around a 10% rate. the primary charge source better be the generator with sufficient power to charge them up through a good properly sized 3 stage charger.

waynefromnscanada · December 2011

Re: winter battery performance

vtmaps wrote: »

Well I heard back. This is from the (Trojan) horse's mouth:
The electrolyte does not get thick. The electrolyte can only increase or decrease its density, which is the "specific gravity".
They also confirmed that the "alpha paste" is NOT the electrolyte (despite the somewhat confusing illustration in their literature.
--vtMaps

Exactly what I expected. Thanks for clearing that up. Thanks for sharing.

Derik · December 2011

Re: winter battery performance

Christmas weekend I had the opportunity to spend some time at my off grid house. I checked my batteries SOC with the hydrometer they were 1.250 and that was with only 2 days out of 10 getting to my 5 hour absorb setting.

Now a week later (& lots of sun) they are up to what they normally are with full sun in the summer 1.255 (this is what they read when new two years ago) Now I could do an EQ which I have only done with my bank maybe 4-5 times since they almost never fall into the range where Trojan recommends Equalizing. This might bump them up a bit but they seem to have a lower SOC than my Trojan 105/s

I'll try to take some photos of a small vile of water and a vile of electrolyte since nobody here seems to believe that the electrolyte is thicker when cool, but I'll have to wait until it cools off again since we are expecting 75 degree weather today.

If I had a generator would I use it if my batteries were fully charged?

Anyway back to my point my batteries behave much differntly when cold in other ways besides the lower capacity.

Now they think it's Spring!

Cariboocoot · December 2011

Re: winter battery performance

Oh dear oh dear oh dear!

Semantics and terminology again!

Yes, electrolyte gets "thicker" when it is cold. The words "thick" and "dense" can be used interchangeably in this instance. All liquids thicken (become more dense) with a drop in temperature (except pure water, which actually expands above and below its maximum density temperature of approximately 61.5F at sea level).

This is why there are temperature corrected hydrometers.

Will it turn to sludge? No. Battery electrolyte does not freeze if it is charged. Remember it is a sulphuric acid solution, not pure acid. Some batteries have more acid, some less, giving them "hotter" or "cooler" performance (yes, both in terms of how they function for producing electricity and how they behave in different climates).

All electronic behave differently with temperature changes, not just batteries. But there's an inverse relationship as most components will perform better when cool than hot. Batteries don't like being either too cool or too hot.

Equalization, by Trojan's recommendations, should only be done if there is a significant difference in SG readings between cells. If all are low then what is needed is more charging (possibly at a higher Voltage, as the charge set points should be temperature compensated via RTS attached to the charge controller). Remember that ambient temperature is not battery temperature unless they are left out in the cold, uninsulated, with no current flow long enough for the batteries to cool down to ambient.

I can't think why you'd use the generator or any charge source on batteries that are fully charged. But cold SG of 1.255 is not necessarily fully charged. Hydrometers aren't all 100% accurate. If you measured this as the fully charged SG when you first got them (at the same temp) that's another story.

You've probably noticed that battery chemistry is complex and confusing, and that even people who know what they're talking about disagree. Sometimes with themselves.

waynefromnscanada · December 2011

Re: winter battery performance

Cariboocoot wrote: »

Oh dear oh dear oh dear!

Semantics and terminology again!

Yes, electrolyte gets "thicker" when it is cold. The words "thick" and "dense" can be used interchangeably in this instance. All liquids thicken (become more dense) with a drop in temperature (except pure water, which actually expands above and below its maximum density temperature of approximately 61.5F at sea level).

This is why there are temperature corrected hydrometers.

Agree, except that the OP was referring to thickening (as in soup) to the point of it being difficult to draw up into the hydrometer, and at temps well above the freezing point of fresh water.

Derik · December 2011

Re: winter battery performance

waynefromnscanada wrote: »

Agree, except that the OP was referring to thickening (as in soup) to the point of it being difficult to draw up into the hydrometer, and at temps well above the freezing point of fresh water.

I simply made the point that the electrolyte in my trojan L-16 RE batteries was thicker in the winter, didn't seem to bubble & didn't seem to gas as much. I didn't use the analogy of soup just said it was noticibley thicker.

My batteries are in an insulated battery box but do see temperatures of 100 in the summer and a little less than 40 in the winter, yes those numbers are about the same as the electrolyte.

If it were soup (electrolyte) it would be egg drop soup and not chowder or cream of chicken!

Happy New Year from the high desert 75 degrees out today! So today it's Chicken Noodle!

icarus · December 2011

Re: winter battery performance

When I return home after bing a way for a couple of weeks, my batteries can be as cold as -20C,, or 0C. I have never seen any noticeable difference in the viscosity of the electrolyte.

Tony

Derik · December 2011

Re: winter battery performance

Never really noticed with my Trojan T-105 either but they are on the sunny side of a small shed so they never get as cold as the L-16 on my house.

I would be curious to see if anyone here in the states where it gets really hot and cold as well notices the same differences I noted in their Trojan L-16 RE batteries.

samuel · January 2012

Re: winter battery performance

Hi guys, I'm back from the cabin and have some new data to mull over.

I recently had the opportunity to equalize the battery bank, measure spec. gravity, draw off 300Ah and measure spec. gravity. I also partially charged from that point and remeasured the specific gravity at two intervals.

I noticed that while charging it took the MS3000 a while to get going. Despite temperature compensation it began to charge around 13.7-13.9V in Bulk. Once it reached 14.2-14.4V it appeared to be charging the batteries at a faster rate. I wonder if the Charger/Inverter is spinning it's wheels until the voltage picks up. I'm assuming that the specific gravity is instant and that if I charge and test versus charge, wait two hours, and test, then there will be no difference between each measurement.

The battery temps ranged from 30-45°F during my stay.

I created this temperature/specific gravity chart:

Attachment not found.

After looking up two battery manufacturers I made a chart and a more detailed table based on the Trojan T-105 user data (which my batteries most closely resemble). The table is extrapolated from the T-105 data. I can upload the spreadsheet if anyone wants to see how I extrapolated. This brings me to a question I can't seem to find an answer to. Based on my measurements it appears that the rule of thumb to SUBTRACT 0.004 for every 10°F below REFERENCE (77/80°F usually) for specific gravity measurements is to estimate the battery capacity for the cold such that when below the reference temperature it is IMPOSSIBLE to correct the reading to 100% SOC. Can this be correct?

Last winter (42-45°F) I equalized to 1.263 and again this winter it was almost the same. In summer (80-82°F) I can achieve the 1.277 literature value.

My records for this year:

Attachment not found.

I would really like to know why specific gravity is corrected for temperature. I couldn't find the reasoning anywhere - just that it needs to be done and that battery capacity increases in heat (and shortens life) and decreases in the cold (and increases life).

Some interesting observations:
0.1V drop under a 2-3A load (compared to open circuit)
0.3V drop under 20A load
1540Ah (usable) summer
1044Ah winter
derate 20-25% for winter

niel · January 2012

Re: winter battery performance

"..........it is IMPOSSIBLE to correct the reading to 100% SOC. Can this be correct?"

without reading everything or looking at your charts and such i ask you to think about this for a second. it means that cold batteries will not meet their ah rating of 100% soc based on the 77 degree temp standard. they are derated in the colder temps. they will not have the same capacity as when they were warm.

winter battery performance

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