Deep cycle 6v charging help
Rich_A
Registered Users Posts: 5 ✭✭
Just found this forum. Been looking for a good source for "alternate energy" discussions and info. This site looks to be one of the best I've seen. I will be spending a lot of time here getting educated .. (I hope) <grin>
I'm trying to set up something a little different here than your normal off-grid alternate energy solution. Recently inherited this property and home that is pretty much off the beaten path. We are on a small mountain top on a several mile unimproved dirt road in North Central Connecticut. For the past two years I've been renovating this 70's era home which had been unoccupied for several years and needed a lot of work.
The most pressing problem here at the moment is short term power outages. We are in a heavily forested area of old growth trees and our electric service is often interrupted for (mostly) short 1 to 6 hour periods. So far this past 12 months we've had maybe 10 outages. These are usually caused by tree limbs contacting the top electric lines on the poles. Normally the lines are not damaged, but the contact causes the line to be shorted and we loose power until the electric company can find the problem area, remove the tree limbs and re-set the local breakers on top of the poles. The electric company is quick to respond and because the problem is often very local and in a limited area it is fixed quickly .. 1 to 2 hours at most. Sometimes we do have (twice now) major storm related outages that last several hours. In that case because our several mile long road in the mountains only has like 6 people living on it .. we are of course the very last to have our power restored. I have a whole house external connection wired for a generator. (still haven't gotten the genny yet)
In the mean time, I thought of building some kind of small battery / inverter system to use sorta like a big UPS just for these short term outages. I only need to keep the Fridge, some electronics, lights and the furnace running. Rather that running out to the garage to fuel up a generator, hook it up and run a cord to the house hookup (usually in the dead of Winter in a snow storm of course) I thought to just have this battery / inverter backup system in the basement ready to just "plug in" and be okay for several hours.
So I've purchased two new 6v 215 AH golf cart batteries and have a 3K pure sine wave inverter (12 volt) set up. When I got the batteries home I checked them and found although they are the same models etc. they were manufactured in Sept and Nov of this year. I was hoping to get as close to a "matched" pair as possible. I found the Specific Gravity in each cell (new out of the box and supposedly fully charged) to be good and close to being equal in one battery. But the 2nd battery had one cell that was quite a bit lower than the other two. (I didn't write it down but it was something like two were at 1.250 and one was 1.200 .. So I put on a "cheap" 4 AMP smart charger that was a high freq. 3 stage charger and maintainer. I've used this charger before on some small SLA deep discharge and regular car 12 volt batteries and it worked great. But it doesn't seem to be working correctly with this new "suspect" 6v golf cart battery I have. It has quickly gone into (i think) it's equalizing mode .. and the voltage has been cycling between 7.1 and 7.2 volts for 2 days. ( Normally when re-charging a 12v battery it goes into it's "equalizing mode if needed" and cycles between around 15v for a couple hours and then drops down to it's maint. mode of 13.8 or so volts.
However, during the 6v battery charge, the charger screen stays red and flashes those "top off or equalizing voltages". It's "supposed" to finish at some point and then turn green and go into it's maintenance (float?) charge (green screen) at 6. something volts. But I'm now starting into day three and it hasn't finished yet.
Can anyone tell me what kind of time frame I'm looking at to finish charge a 215 AH deep cycle golf cart battery using a smart charger running at a max of only 4 amps ?? Sorry for the long post .. just trying to give as much info as I can. I intended to first fully charge each battery individually and hopefully equalize them before installing them in series for the system. Working on a limited budget but hope to increase capacity in near future to a series / parallel setup and add solar power to recharge the batteries later. I'm also now worried about the "gassing" situation while doing full recharging. At the 7.2 volt full at 4 amps? there IS a little bit of bubbling going on ... (very very little) But I'm concerned. I figured during normal use, after the power is restored I could have more than weeks or months before needing it again and could "slow charge" the batteries back up to full.
Comments
For example "The recommended charge current is 10%-20% of the AH capacity of the battery bank, based on the 20 Hr AH rate (C20)."
https://rollsbattery.com/public/docs/user_manual/Rolls_Battery_Manual.pdf
I am available for custom hardware/firmware development
Sorry to hear about the problems with that one FLA battery. Have you tried a load test on it (or taken it to the battery retailer and have them check it)?
It does sort of sound like that battery is sulfated... Quickly recharging to "full", but perhaps not really full. Do you have the SG readings for the cells after "charging"?
If the cells remain low (or at least one of the cells is "low"--Say 0.015 to 0.030 below a "nominal" 1.265 SG fill), and equalizing does not restore... I would try to get that battery replaced (would be "an easier return" if it "failed" a load test).
Generally, a 6 volt golf cart battery is around 200 AH... If it sat for ~1 month at room temperature not connected to a charger, it can drop to about 75% state of charge through self discharge (the colder the battery is stored, the slower the self discharge).
- 200 AH * 0.75 state of charge = 150 AH of stored current
- 200 AH - 150 AH = 50 AH to recharge
- 50 AH / 4 amp charger = 12.5 hours of charging "ideally"
As batteries recharge, they slow the charging current (charger runs to ~7.35 volts) and the absorb should be held at that voltage for ~2-6 hours (the deeper the discharge, the longer the time "absorb" stage).So, as a wild guess--The charger should take about 16 hours (+/- a couple of hours) to fully recharge the battery the first time.
To equalize an FLA battery, you need 2.5 to 5% rate of charge...:
- 200 AH * 0.05 rate of charge = 10 amps
- 200 AH * 0.025 rate of charge = 5 amps
- EQ should be around 7.5 to 8.0 volts (you really want to get your ~5 to 10 amps of current flowing into the battery and a pretty good "fiz" going--Not a rolling boil. And if the battery is left on EQ for "hours", it will get hot--And with enough current/time, hot enough you need to stop charging to prevent overheating)
- EQ starts when the battery is near 100% SoC... EQ is basically controlled over charging of the "full" cells, to bring up the under charged cell(s) to full too.
- "Full charge" is when a cell SG stops rising (check cell SG every 30-60 minutes). Some battery Mfg. recommend EQ ~once per month... Others recommend EQ when the difference between the high and low cell SG is over ~0.015 to 0.030 SG units (be careful when measuring SG... gas bubbles can collect on the float and give you a miss reading--And rinse the hydrometer after you are done with a few squirts of distilled water--Old electrolyte can get sticky and cause the float to stick to the wall of the hydrometer).
So, that charger is a bit small to really give a "good equalize" to your battery. But if you need "corrective" EQ on a "new" battery--There is probably something wrong with the battery.-Bill
For example, a 1 hour outage where you only need to provide heat (because the fridge and freezer will stay cold enough for example) is very different than a 12 hour outage. Discharged to ~50% you battery will likely deliver ~ 1.3kwh of power, and that is from a comparatively small load. Try to run a fridge compressor for very long, and, as I said, the battery will drop below low voltage disconnect.
Consider, at a minimum, 4 GC batteries, a 1 kw inverter, ideally an inverter/charger like a Magnum.
As for you current set up, at the very least, get a good four stage charger if you want your batteries to last.
All things considered, for the price of the inverter and the batteries, a Honda Eu2000i generator (or a cheaper clone) would cover most of the essential loads for a long time on very little fuel at less cost and more reliability.
Good luck and keep in touch,
Tony
Just to clarify (maybe I missed it), but is the 4a charger set for, and/or capable of 6v battery charging? If it's a 12v charger, it may see the 6v as under a low battery cutoff and be faulting? If so, you'd need to charge it along with the other battery.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Also, I was not correct about my inverter .. it's actually a 1,500 watt unit with a 3,000 watt surge capability.
Yes I know I could just pick up a cheap knock off Honda inverter generator clone for 6 to 7 hundred bucks. But money IS an issue at this time. And the "gasoline generator" doesn't solve the actual problem here. At 74 years old with some pretty bad recent heart problems I'm hoping to eliminate my having to trudge out to the detached garage where the generator will be stored (some distance from the house) and dig out the generator, gas it up, hook it up and run a cord to the house and get everything running only to have the power come back in 1, 2 or 3 hours.
My thought was that a small battery backup system would enable me to keep the furnace, fridge and TV and some electronics going for just a few hours and I wouldn't have to fool around with the generator at all. In the Winter what with my current medical problems I really don't want to be trudging around in the snow in sub zero weather messing with gas and such when I'm only looking to keep a couple items and some lights running in what most likely only be a few hours at the most.
It's been a couple years since I first moved up here and during the renovation I did check various wattage's etc. for everything. All the appliances were bought new at that time and all are tops in energy efficiency. Since then I lost my notes but from memory I believe the furnace (measured with a clamp on amp meter at the electrical box) saw a bit over 6 amps spike at start up and a regular running load of a little less than 3.5 amps total (@120 volts) that was for the oil burner and the circulatory pumps for the hot water baseboard heating system combined or about 400 watts. Last Winter our coldest month averaged 28 degrees per day, and all that time the furnace only turned on for 5 minutes about every hour or actually 25 times in a 24 hour period. So for that total 24 hour period of 28 degree weather, the furnace ran for a little over 2 total hours. Not sure about my calculations here, maybe 800 total watt-hours? I've lost a few brain cells over the years. <grin>
For the fridge, just because I didn't have any notes from 2 years ago I did a short test earlier today, and recorded the use over a 5 hour period. During normal run time the fridge was drawing 108 watts and less than 1 amp. I knew it was a pretty good energy efficient unit and was frankly surprised at how little power it was using. So I left it plugged into the "kilowatt" meter for 5 1/2 hours and checked and it only drew 0.31 kWh for the entire 5.5 hours. Of course that was today and it's Winter and the house is usually at a pretty low ambient temperature. But still I'm wondering if I'm reading the meter correctly or if I'm screwing up my calculations by comparing AC street wattage at 120 volts and DC wattage provided by the battery's 12 volts? This was second nature to me 20, 40, and 60 years ago. Now, not so much.
So I originally thought I'd be good to run a few lights and maybe a small LED TV for a few hours along with the intermittent use of the furnace and fridge and would be okay. At least for a few hours ? Shouldn't I be able to run those things for a few hours only using 50 percent of the 215 AH battery capacity? Maybe I should also consider inverter efficiency, and a host of other things that could affect this.
Remember, I'm not looking to go "off grid" with a whole house configuration for days at a time. I'm only looking to find a quick and easy way to "get by" for those several times a year when I loose power for 1 o 3 hours at most. I hope I haven't underestimated my energy requirements here. If so perhaps 4 more batteries with all six in a series / parallel arrangement should give me about 645 AH of which I could probably drain to 1/2 capacity and still have 300 AH reserve left if really needed? And I still wouldn't have spent as much money as a decent inverter type 2 KW Honda generator.
Yea--Double spacing has been a problem for a few years, but mostly restricted to a few posts/systems (like my android phone with firefox).
I will reopen the trouble ticket and see what happens.
-Bill
As Estragon also points out, about 1 kw would be the right size for your battery bank. Once again, define your mission critical loads, and design the battery/inverter/charge regimen around those loads. Adding solar is of course an option, once again defined by the loads.
Tony
PS. Your 215 ah (12 vdc) battery bank would like to see ~21-25 amps of charge current to keep it happy. Too low of a charge current is a way to slowly kill a battery.
T
Lead Acid Batteries actually need to be cycled... One full, it can take dozens of cycling (down into the 75% tio 50% state of charge range) to help "form" the plates and reach the battery's maximum AH rating.
At this point, you can stop the charging. It is probably not doing anything "good" for the battery at this point.
Your SG readings seem to be OK...
Regarding how much current your refrigerator uses... I am trying to be clear here, and if you already know this, sorry to be redundant.
Your refrigerator using 1 amp at 120 VAC... But the battery bank is at ~12 VDC. Remembering our power equations:
- Power = Voltage * Current
- P= V*I = 1 Amp * 120 VAC = 120 Watts
- I=P/V= 120 Watts / 12 VDC = 10 Amps
So, your 1 amp @ 120 VAC motor is actually drawing around 10 Amps @ 12 VDC...And AC Induction Motors draw (very roughly) 5x current during starting:
- 1 amp * 120 Volts * 5 starting/locked rotor amps = ~600 Watts starting
- 600 Watts starting * 1/12 VDC battery = 50 Amps starting current
Deep cycle batteries can supply (relatively) high surge current... But with all of the stuff that goes on in a solar power system, the recommended maximum size AC inverter is ~250 Watts per 100 AH of 12 volt battery capacity:- 200 AH battery bank * 250 Watts per 100 AH = ~1,000 Watt recommended max inverter rating (typically 500-1,000 Watt inverter suggested)
And to run a modern full size AC refrigerator is suggested around a 1,200 to 1,500 Watt minimum AC inverter... So, technically, suggesting at least 2x parallel strings of golf cart batteries (12 volts @ 400 AH or 4x GC batteries total).-Bill
Telling the doctor, (the IT guys) the symptoms will make the diagnosis easier. Hope this helps.
Edit: Once a comment is made the bold title dissappears and upon reopening goes to the latest post.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Assuming you can babysit the loads in an outage, you might be able to get down to say a 35%SOC and (maybe) still be able to start/run the loads (one at a time). That gives you (maybe) 1600WH usable.
Running loads of (eg) 50wh/hr fridge + 50wh/h furnace + 50wh/hr lights = 150w ÷ 75% inverter efficiency =200w. In theory, if the load numbers are about right, that might get you through many of your outages. 1600/200=8hrs, but the starting load may pull bank down too low before then. The inverter will likely fault if voltage sags to ~10.5-11v starting a load.
For the genny, you may want to consider a propane (or converted from gasoline) unit to reduce fuel storage issues. I think there are some small gennies that can be fitted with remote start.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
2. I need to address the problem of re-charging the battery(s) in high current mode and deal with gassing problems.
the entire box is vented with a Zepher fan, directly to the outside, with the fan voltage controlled so that it comes on when the battereis are charging at or above gassing voltage, and is off all the rest of the time.
https://www.solar-electric.com/zephyr-battery-box-ventilator-24-volts-dc.html?gclid=Cj0KCQiAt_PuBRDcARIsAMNlBdoLH6HgpU6d7wWjdlIzFyzmea2nEGBEqzf6CdVbabsUlR4LUKddUhQaArypEALw_wcB
This one is 24 vdc, but they make (and our host sells) a 12 vdc version. Draws ~1/2 amp iirc, and plum is into 2 or 3” abs or PVC DWV pipe. Very easy to install.
All that said, 2 (or even) 4 GC batteries are unlikely in a large space to produce enough gas to be a real risk imho.
Good luck, and keep in touch,
Tony
Tony
Before my solar setup, I used a similar roll-around charger with a pair of GC batteries for a few years and it worked fine.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter