Batteries giving a low hydrometer reading

Hairfarm · May 2015

Greetings,

Some info first:

Batteries: US 2200 (6-volt) @ 232ah. Wired for 3 series sets then paralleled for 696ah.
Specific gravity at full charge is 1.270 minimum.

Before taking readings I:
Waited until the batteries were fully charged and floating at 13.1.
Disconnected all loads.
Checked all water levels. Levels were fine.

The battery bank is brand new from golf-cart distributor.
I have never equalized the batteries yet since my system in only a month old.
The temp was about 83 degrees.

When I took a hydrometer reading every single battery cell measured only slightly over 1250. But as I listed above my manufacturer states that the minimum should be 1.270. Is my hydrometer off? If every battery is slightly over 1250 (exactly the same) that tells me that either all of the cells are low or that the hydrometer is off.
Should I equalize and re-read?

Here is the hydrometer I used. It got decent reviews on Amazon. Anyone recommend a better one?

http://www.amazon.com/E-Z-Red-SP101-...red+hydrometer

thanks,

Hairfarm,

CALLD · May 2015

1st) it's a good sign that all of them are giving an equal reading which means your wiring is doing its job well. If the voltages under load are all equal (within 0.02v per 6v battery) that's also a good sign. However if the hydrometer readings are low they are either not fully charged or more seriously - sulfated...
Try the manufactures specified equalization charge to see if you can get the specific gravity up to spec, if that doesn't work, perform a load test to see if the discharge curves match the manufactures performance claims - if they do then all should be fine and the hydrometer is probably out.

Sulfation and internal resistance are directly linked - the more sulfation present the higher the batteries internal resistance will be. So if you are getting lower than expected voltage curves under discharge followed by shorter than expected bulk charge times, suspect sulfation...

Blackcherry04 · May 2015

Put them on a Equalization charge ( 15.5v ) for a hour at a time and watch for a rise in the SG level on the hydrometer. Continue to do it. checking it each hour. Watch the temperature of the batteries and make sure they stay below 115 deg F. When they reach 1.265-1.270 they are done and equalized. Being new it'll probably take 2-3 hrs.

Vic · May 2015

Hi Hairfarm,

First, what is your Absorb voltage setting in your CC, and perhaps your inverter?
What is the Absorb time, and how is Absorb terminated (ie, are you using EA)?

You should try to fully charge your batteries, and then do an EQ, to the manufacturer's recommended specs for both Absorb and EQ.

Regarding the Hydrometer, the plastic one that you have, MAY, possibly be better than nothing, but perhaps not much better than that. The Hydro that you have may be telling the correct story, but, at the very least, those plastic Hydros seem to deteriorate fairly quickly.

Here is a very good Hydro, that is distributed by MidNite Solar:
http://www.solar-electric.com/batter...ydrometer.html

ALWAYS, rinse your Hydro at least three times after y our SG measuring session is done, with Distilled Water.

Here is some info from this Forum about Hydrometers, and a link and a search term to use:
http://forum.solar-electric.com/foru...-an-hydrometer

FWIW. ALso, if you could make a Signature, indicating what are the major components of your system, including PV, CC/s, inverter/s, and if you are off grid, etc, it would probably speed answers to questions, and make answers more appropriate to what your system is, and to what you are trying to accomplish.

Thanks! Vic

Vic · May 2015

AND, always use an Remote Temp Sensor for each charge source.

Hairfarm · May 2015

CALLD wrote: »

1st) if that doesn't work, perform a load test to see if the discharge curves match the manufactures performance claims - if they do then all should be fine and the hydrometer is probably out.

What's the best way to do a load-test?

Hairfarm · May 2015

Vic wrote: »

Hi Hairfarm,

First, what is your Absorb voltage setting in your CC, and perhaps your inverter?
What is the Absorb time, and how is Absorb terminated (ie, are you using EA)?

FWIW. ALso, if you could make a Signature, indicating what are the major components of your system, including PV, CC/s, inverter/s, and if you are off grid, etc, it would probably speed answers to questions, and make answers more appropriate to what your system is, and to what you are trying to accomplish.

Thanks! Vic

Thanks for the tips. I'll get more info when I have a sec and post back. btw, what is EA? I'll fix my signature too when I get a chance. I think I'll have to purchase that hydrometer too!

zoneblue · May 2015

End amps. For that youll need a setup with a battery shunt and a controller that supports EA.

New system owners are usually anxious to see correct charging, and thats a good thing. JUst remember it takes a bunch of cycles to complete forming the plates, ands its not uncommon to see low SG for a bit. Keep charging it correctly and it will come right.

Hairfarm · May 2015

zoneblue wrote: »

End amps. For that youll need a setup with a battery shunt and a controller that supports EA.

New system owners are usually anxious to see correct charging, and thats a good thing. JUst remember it takes a bunch of cycles to complete forming the plates, ands its not uncommon to see low SG for a bit. Keep charging it correctly and it will come right.

I'm using a CC Flexmax 80 (Outback). I did order a battery temp monitor for it today along with a new Hydrometer. No, I do not use a shunt to measure EA. Your comments are reassuring. I'll retest when I get the new Midnite hydrometer too just to compare with previous readings.

Hairfarm · May 2015

Vic wrote: »

Hi Hairfarm,

First, what is your Absorb voltage setting in your CC, and perhaps your inverter?
What is the Absorb time, and how is Absorb terminated (ie, are you using EA)?

Thanks! Vic

My Absorb cycle defaults at two hours. I have left the default intact. It is set for 14.1 volts. My inverter/charger is not setup to charge at this time. It will be later after everything tests ok.

My CC will BULK charge for as long as it takes until set points are reached. The ABSORB cycle will continue for the duration of the Bulk cycle or until the 2 hour (default) Absorb time limit is reached. For example, if a Bulk cycle takes 1 hour to reach the Absorb voltage set point, then the Absorb cycle will continue for 1 hour as well. However, if a Bulk cycle takes 3 hours to reach the Absorb voltage set point, then the Absorb cycle will continue for 2 hours only. A Bulk cycle will be re-initiated if the battery voltage is not sustained at the Absorb voltage set point.

I'm not using a shunt to measure EA. My CC is only using the info that I have programmed into it. Right now I'm doing manual calculations to compensate charging voltage for heat. I'm in the Mojave desert.

thanks,

BB. · May 2015

Remember that Equalization is technically used to "equalize" cell SG for a "fully" charged battery.

Your battery seems to not be fully charged and I would guess it is a combination of low Absorb set point and short absorb timer.

Your voltage set point should probably be around 14.5 to 14.8 volts and 2-6 hours for the absorb timer (shorter if you are not deep cycling the batteries, and closer to 4-6 hours if you are).

Remember, the Outback is probably using its own internal temp sensor and is adjusting the battery voltage based on the controller's air temperature (for better or for worse). Also, use a good volt meter to measure the battery bank charging voltage set point. The voltage displayed by the Outback may be temperature compensated (i.e., it shows 14.1 volts if the batteries are at ~70F, but really is at 13.X at the 95F of the temperature corrected set point--And some controllers may display true voltage on one screen and temp corrected on another).

And 13.1 volts sounds pretty low for float voltage, unless your battery bank is really at 95F or higher...

-Bill

Hairfarm · May 2015

BB. wrote: »

Remember that Equalization is technically used to "equalize" cell SG for a "fully" charged battery.

Your battery seems to not be fully charged and I would guess it is a combination of low Absorb set point and short absorb timer.

Your voltage set point should probably be around 14.5 to 14.8 volts and 2-6 hours for the absorb timer (shorter if you are not deep cycling the batteries, and closer to 4-6 hours if you are).

Remember, the Outback is probably using its own internal temp sensor and is adjusting the battery voltage based on the controller's air temperature (for better or for worse). Also, use a good volt meter to measure the battery bank charging voltage set point. The voltage displayed by the Outback may be temperature compensated (i.e., it shows 14.1 volts if the batteries are at ~70F, but really is at 13.X at the 95F of the temperature corrected set point--And some controllers may display true voltage on one screen and temp corrected on another).

And 13.1 volts sounds pretty low for float voltage, unless your battery bank is really at 95F or higher...

-Bill

Ok. That must be right. I lowered my set points overall by .5 volts based on very hot temperature...that has yet to arrive! I put the cart ahead of the horse, as they say. I set my CC set points to be ready for 115 degree desert heat even though its only 89 degrees out now. I need to increase the voltage and wait until it's actually hot enough to lower the voltage again, and not before. Hope that makes sense. I'll increase and take new hydrometer readings after recharging for a few days.

I ordered the temperature sensor for the Flexmax today. My invert/charger already has one.

Vic · May 2015

Hi Hf,

Well, if you have an Outback Inverter, the BTS/RTS should be identical. If you are mostly using the FM CC to charge the batteries, then you could move the RTS to the FM, until you get the new RTS ... hard to remember if you have ever mentioned what IS the inverter that you are presently using ...

AND, if you are using the Hydrovolt Hydrometer, they say that it is temperature-compensated. If your Hydro is not compensated, the factor is about 3 SG points per every 10 degrees F variation above/below about 77 degrees F, or are you on C? Anyway, for uncompensated Hydros, add three points per 10 degrees F for electrolyte temps above about 77 F, and subtract three for every 10 F degrees below 77 F.

FWIW, Good Luck, Vic

Hairfarm · May 2015

Anyway, for uncompensated Hydros, add three points per 10 degrees F for electrolyte temps above about 77 F...

That may make quite a bit of difference. My batteries are around 96 degrees F right now, (Mojave desert). So that's already six points I should add?

It's going to get a lot hotter out there too. In fact I'm going to insulate my battery compartment with hay bales this Saturday, which should help to insulate the batteries much better.

thanks Vic.

BB. · May 2015

I think I asked you before--Anyway you can make an Earth Berm/Earth contact battery shed?

Insulation is OK during the day, but you need to ventilate when the outside air temperature is lower than your battery bank to really remove heat from them.

-Bill

Hairfarm · May 2015

Bill,

I have my batteries in a locked, full-sized refrigerator. The batteries are sitting on cement blocks and 2x8's inside the fridge. The fridge has a low, screened vent on one side and a high, screened vent on the opposite side of it. The vent holes are about 4 inches diameter, round. Mounted inside the fridge on the high vent I have a 200mA DC fan installed. This fan pushes the air/gasses out of the fridge and runs off of a port on my charge controller. I can set the fan to run manually or automatically to expel gasses at pre-programmed set points from the absorption and equalization phases. At night I can manually run the fan to cool the batteries as well. I have a thermometer inside the fridge to show ambient temp and have ordered a battery temp monitor for the CC. I already have a temp monitor for the inverter, a Xantrex Prosine 2.0. The batteries were 96 degrees today. So this Saturday I'm going to insulate them.

The full-sized fridge is too tall to bury in dirt, obviously. So I'm going to stack straw bales up the sides and top of the fridge to help insulate it in the day. I'm going to cut spaces in the straw bales where they cover the vent holes so that the intake and exhaust are not obstructed. Earth Ship builders have used hay bales to great success to insulate their structures. It's like having an insulated wall that is 20 inches thick. Hopefully this will keep my batteries from overheating when its 115 degrees out there. Also I placed the fridge on the shady side of the house so it's not in direct sunlight.

Basically doing everything I can. I paid $700 for my batteries and don't want to ruin them by over heating. As a newbie, I'm sure I'll have plenty of other opportunities to ruin them in many other creative ways.

I plan to keep a temperature log.

thanks

BB. · May 2015

Batteries are a net producer of heat... Especially if you charge them a lot at the >80% SOC range (and especially >90%) and/or run them with heavy currents. Every 10C (18F) you increase battery temperature (over ~25C or ~77F), you cut their life by a factor of 1/2...

As long as you keep an eye on them--I worry that a "perfect" job of insulation will not allow the batteries to cool down.

-Bill

vtmaps · May 2015

Hairfarm wrote: »

In fact I'm going to insulate my battery compartment with hay bales this Saturday, which should help to insulate the batteries much better.

Bill is worried that insulation will not allow the batteries to cool down.... he is being too gentle... let me be more blunt: Do NOT insulate them. In your environment that can ONLY make them warmer.

The only reason to insulate batteries is to make them warmer than the surrounding environment.

--vtMaps

Hairfarm · May 2015

vtmaps wrote: »

Bill is worried that insulation will not allow the batteries to cool down.... he is being too gentle... let me be more blunt: Do NOT insulate them. In your environment that can ONLY make them warmer.

The only reason to insulate batteries is to make them warmer than the surrounding environment.

--vtMaps

I hear what you're saying, and all advice is appreciated. From what I understand insulation works both ways. Those that build earth-ships with straw and mud are keeping their dwellings cool in hot climates. However, I realize my batteries are generating their own heat from within too. And already they're hovering at 96 degrees. And it's not even June yet. I'm sure they'll get hotter. My data sheet for my battery type states that 120 degrees should be the max operating temp or thermal heat breakdown (?) occurs. My goal is to keep the sun from making the fridge hotter by using straw bales while venting/cooling with the internal 200mA fan. I bought a six-pack of these fans on eBay so I'm not worried when one burns up. At least there will be some air moving through the fridge.

In any case I have to at least try it out. If the batteries temperature is lowered by 10-15 degrees, then success! if not, it only cost me $40 in straw and I can unstack the straw from the fridge in five minutes. No harm done. I'll soon have two battery temp monitors in addition to the two thermometers I have inside the fridge. If my plan actually makes the batteries hotter, I'll post here asap and let you know. I should know in a couple days if this will work. The mojave desert will get to be as high as 115-118 in direct sun in August. It's like a perfect storm of misery. I have to at least try something. Burying underground would be best but it's not feasible.

respectfully,

Batteries giving a low hydrometer reading

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