Specific Gravity...

jtdiesel65

Re: Specific Gravity...

Hopefully it will go back up. I would venture that if you did a couple full 3 hr absorb followed by 3 hr eq cycles and SG didn't move, then SG probably won't.

My old surrettes were chronically undercharged when I got them. It was a shaded 600w array on a 1000ah battery. The electrolyte was white cloudy in some cells and dark cloudy in others. For about a month, I equalized every chance I got and I saw about a 25% improvement. But they were old and I had nothing to lose by being so aggressive on the EQ. Sounds like you have new batteries, so in my opinion after 2 or 3 cycles you should probably start considering your SG to be a new set point.

My new battery instructions say eq once a week, but it's a 1900lb forklift battery and cells are 30" tall. The stamp on the battery says sg at full = 1.285. The documentation that came with battery says 1.285 to 1.290, and documentation from 3rd party says 1.275 to 1.3. Go figure.

What would I do in your case with new surrettes? I'd do a couple full 3 hr absorb followed by 3 hr eq cycles in week one and then eq every week for 4 weeks. But that's just me and I'm certainly no expert here.

Btw I recycled my old surrettes at 15 cents /pound and they were 142lbs each. It was a hard life for them. 1999 vintage and basically made it to 2012.

plongson

Re: Specific Gravity...

Well, I ran the generator EQ yesterday afternoon using the Magnum 4 hour canned program. I'm not sure where it left me though, here's why.

I started off with an overall SG of about 1.235-1.240 when it was floating on the Magnum. The SG slowly started to rise and I monitored water and gravity every 1/2 to 1 hour. Somewhere around hour 3 it seemed like they pretty much peaked and stopped rising. A few cells were actually 1.260 but mostly 1.250 was across the board, and two never got above 1.245. Then around hour 3.5 they actually started to DROP OFF! Some actually appeared worse than when I started but overall, they were back to the original readings. They boiled vigorously the entire time but never lost an appreciable amount of water. They did make a frigg'n mess on the battery tops from popping bubbles though.

I ran the genset this morning again before sun up for bulking and laundry/dish washing chores, and it is in float now but I have not checked the SG this morning.

WTF is up with this crazy set of batteries?? I'm about ready to stop "Wet Henning" over them and just treat them like hired help instead of a little princess...if you know what I mean...LOL

Any ideas or suggestions??

Paul

Volvo Farmer

Re: Specific Gravity...

Did the batteries get very warm? I believe specific gravity becomes lower as temperature rises.

plongson

Re: Specific Gravity...

No, only about 55°f

Vic

Re: Specific Gravity...

Hi Paul,

VF is correct. During EQ, temps rise. This rise causes the battery current to rise, as battery terminal voltage decreases. AND, the SG does fall with temp rise, but that effect is farily small for any reasonable temp.

When you said that the Magnum did its canned EQ, are you able to set EQ voltage? Disd you?

And, forget, but think that the Magnum has the required BTS? Good Luck, Vic

plongson

Re: Specific Gravity...

Well Hallelujah, Wonders never cease. I am just finishing up another EQ this afternoon and what should happen...I'm seeing 1.260-1.265 pretty much across the board. I might actually be getting these things up. I think I scared them with my earlier comments about making them work for a living.

Anyway, things are looking better. I don't take anything for granted and I still need to keep them up (and it's frigg'n snowing like hell right now). I think I'll taper off on this project and go make a celebratory toddy...

Paul

NorthGuy

Re: Specific Gravity...

plongson,

I'm just wondering what's the end of the story. Did you managed to finally get SG up. Does it stay there? I'm having a similar problem, but mine is way worse ...

Blackcherry04

Re: Specific Gravity...

NorthGuy wrote: »

plongson,

I'm just wondering what's the end of the story. Did you managed to finally get SG up. Does it stay there? I'm having a similar problem, but mine is way worse ...

That thread is almost a year old and he may not be coming back very often ( July was his last post ). What kind of batteries do you have and how many ?? The procedure is about the same for most flooded batteries. You have to keep the temperature under control.

vtmaps

Re: Specific Gravity...

NorthGuy wrote: »

I'm just wondering what's the end of the story. Did you managed to finally get SG up. Does it stay there? I'm having a similar problem, but mine is way worse ...

Welcome to the forum NorthGuy,
How about starting a new thread to ask about your problem...
--vtMaps

NorthGuy

Re: Specific Gravity...

I hope he made it work.

I've got Trojan Industrial line IND13-6V batteries, and I can't get SG high enough, and even when I manage to move it relatively close to specs, it drops back down very next day.

I'll do as vtmaps said and post it in a separate thread. I'm still doing some charge/discharge tests in hope to fix it. I'll post as soon as I get enough data.

Blackcherry04

Re: Specific Gravity...

NorthGuy wrote: »

I hope he made it work.

I've got Trojan Industrial line IND13-6V batteries, and I can't get SG high enough, and even when I manage to move it relatively close to specs, it drops back down very next day.

I'll do as vtmaps said and post it in a separate thread. I'm still doing some charge/discharge tests in hope to fix it. I'll post as soon as I get enough data.

If you are able to get to the correct SG, then you have to look at the things you can change in your daily charging. Voltage, Time and Ending Amps, If your getting enough Current in Amps to satisfy the capacity of your bank. If you can't do it with Solar alone, they you will have to supplement it with your generator.

plongson

Re: Specific Gravity...

Hey North Guy, I'm still here and check in periodically.

My SG on my Surette batteries is always an ongoing battle. With 16 batteries in two strings, I always have the same 3 that struggle to get to 1.255 when the rest are 1.265 to 1.270 pretty easy. I've made changes in small increments, but FOR ME I seem to the best results with a long and moderately hot absorb. Surette recommends a formula for absorb that is longer than most of us have sunshine.

Overall though, the system really works great and I'm done agonizing over getting those bad players to come up. You can only do so much and gott'a work with what you have.

Now after much research and babysitting these batteries for over a year this is what I think

1.) Surette batteries are tough to get 100% equal and up to the desired SG.

I didn't commission them correctly. If I had it to do over

2.) I would have specified all the batteries be at full charge and 1.270 on delivery.
3.) I ordered the batteries too soon. Unfortunatly the batteries came in at the same time as all the panels, invertes and coltroller.
4.) I would not have let them sit for 4 weeks uncharged before the install
5.) I would have immediately done an EQ and recorded the SG for future reference.

Presently I'm absorbing (using a Midnite Classic 250) at 59.2v , using varimax, for a min of 3.5 hours and a max of 6 hours. I service every 2 months and use about 2 gallons (1 gal/mo).

Wintertime is tough though with short days and higher use.

Hope this helps!

Paul

NorthGuy

Re: Specific Gravity...

Thank you Paul,

I start thinking that my problem is quite typical. Regular charging routine with absorption going for 1-2 hours simply doesn't produce enough bubbling to fight stratification.

plongson wrote: »

My SG on my Surette batteries is always an ongoing battle. With 16 batteries in two strings, I always have the same 3 that struggle to get to 1.255 when the rest are 1.265 to 1.270 pretty easy. I've made changes in small increments, but FOR ME I seem to the best results with a long and moderately hot absorb.

I don't know yet how long do I need, but it's definitely way longer than I would want. If I go several days with standard Xantrex charging routine, SG goes way down, and then I need to equalize, and it takes 15 to 20 hours of equalization to get to a relatively normal SG. I guess an asorption voltage applied for equally long period of time would work as well. Fortunately, I'm still connected to the grid, so it's easy to experiment, but I need to somehow eliminate the need for long operations before I disconnect. In Winter, sun here only shines for five hours.

plongson wrote: »

Surette recommends a formula for absorb that is longer than most of us have sunshine.

That is interesting. Do you still have that formula. Where can I find it?

NorthGuy

Re: Specific Gravity...

Blackcherry04 wrote: »

If you are able to get to the correct SG, then you have to look at the things you can change in your daily charging. Voltage, Time and Ending Amps, If your getting enough Current in Amps to satisfy the capacity of your bank. If you can't do it with Solar alone, they you will have to supplement it with your generator.

I cannot quite get the specified SG of 1.260. It only goes to 1.245. I guess I'll have to live with that.

I'm experimenting with absorption. I maxed the voltage at 58.8, which is the top of the suggested range. This increased heat - every charge the temperature goes up 2C, but didn't help much with SG. Looks like there's no substitute for long absorption time. OP came to the same conclusion. So will have to work on this.

plongson

Re: Specific Gravity...

This is from the Surette website. Just a quick cut and paste

Attachment not found.

NorthGuy

Re: Specific Gravity...

plongson wrote: »

This is from the Surette website. Just a quick cut and paste

Attachment not found.

That is an interesting formula. It gives 3 hours for me. That is, BTW, less than 4 to 5 hours that Trojan tech support recommended. However, when I do absorption, the current tapers down to around 5A relatively quickly, may be in an hour, hour and a half. Then it stays about the same, still slowly tapering down. Perhaps, for first hour and a half, the formula will work and I'll get 0.42*100A*1.5 -5% = 60AH. But, if I double the time to 3 hours, this will not double the charge, as the formula suggest. During this time, I'll only get 5A*1.5hr = 7AH. This way, to get full 120AH, I'd need to absorb for 13.5 hours.

How long is the absorption time that you ended up using?

Blackcherry04

Re: Specific Gravity...

NorthGuy wrote: »

That is an interesting formula. It gives 3 hours for me. That is, BTW, less than 4 to 5 hours that Trojan tech support recommended. However, when I do absorption, the current tapers down to around 5A relatively quickly, may be in an hour, hour and a half. Then it stays about the same, still slowly tapering down. Perhaps, for first hour and a half, the formula will work and I'll get 0.42*100A*1.5 -5% = 60AH. But, if I double the time to 3 hours, this will not double the charge, as the formula suggest. During this time, I'll only get 5A*1.5hr = 7AH. This way, to get full 120AH, I'd need to absorb for 13.5 hours.

How long is the absorption time that you ended up using?

Since you never stated the Voltage you are using for Absorb, from all you said, Raise the Charge Voltage. I'd also check the voltage at the battery post and make sure the readings you are using are true and accurate.

stephendv

Re: Specific Gravity...

I see similar behaviour with my forklift batts, they start the day at 85% charged and enter absorb by about 11am. But no matter how long I leave them absorbing at 2.4V (57.6), even 5 hours in summer, they never quite reach the fully charged SG of 1.29. They stick around at 1.28 max.

But, doing just a short EQ charge, say 10 minutes after a normal absorb brings them up to 1.29. A lot of forklift chargers support this type of charging by default: bulk, absorb, then current limited but voltage unlimited charge. Charging stops either when a predefined voltage is reached, e.g. 2.65V or when voltage stops rising, or when current decreases below a certain value. Might be worth trying to do a short EQ after absorb if you can and see if it has an effect.

You can find more info on this type of charge by searching for "IUI charge battery".

plongson

Re: Specific Gravity...

NorthGuy wrote: »

How long is the absorption time that you ended up using?

Right now in winter, I'm using 59.2 volts and 3.5 hours minimum, 6 hours maximum. my Classic 250 charge controller allows for changes in shading/cloud cover etc that can compromise the absorb charge. It's called VARIMAX and looks for a change from both the preset volts and amps parameters, to maximize the available absorb time.

Blackcherry04

Re: Specific Gravity...

stephendv wrote: »

I see similar behaviour with my forklift batts, they start the day at 85% charged and enter absorb by about 11am. But no matter how long I leave them absorbing at 2.4V (57.6), even 5 hours in summer, they never quite reach the fully charged SG of 1.29. They stick around at 1.28 max.

But, doing just a short EQ charge, say 10 minutes after a normal absorb brings them up to 1.29. A lot of forklift chargers support this type of charging by default: bulk, absorb, then current limited but voltage unlimited charge. Charging stops either when a predefined voltage is reached, e.g. 2.65V or when voltage stops rising, or when current decreases below a certain value. Might be worth trying to do a short EQ after absorb if you can and see if it has an effect.

You can find more info on this type of charge by searching for "IUI charge battery".

Sounds like good advise, with deficit charging it must be having a real effect and with the OP's statement of "15-20 hours of EQ' ing " to get the SG's up. Thats a long time, something just doesn't seem right.

NorthGuy

Re: Specific Gravity...

Not to highjack the Paul's thread any further, I have created a new thread were I posted all the data and numbers. Any thoughts are appreciated.