Abusing an SLI battery so you don't have to!

[Rainwulf]

Heh, I've already done that experiment by accident with a really expensive Enersys / Odyssey at 4v ocv. Didn't think I should use an LVD and woke up one morning freaking out.

The Optimate 6 brought it back nicely. Not too much harm since I got to it asap but I'm sure I cooked off a few cycles.

So, yeah, I could just burn it up but I've been there. Still trying to think of something I can learn something interesting from - lifepo4 has been done to my satisfaction - conventional / pure-lead agm's are fun. Maybe an FLA is in my future if I can think beyond just rote proper maintenance.. hmmm

A decent FLA will have your testing go into the year territory.

[Willy T]

Look on the bright side, you could be off grid and waking up 600 amp hrs in the hole after 4 days of clouds and 10 more days in the forecast. Oh yeah, it's all scaleable. This is where the 50-80% soc charge scheme @ C/6 kicks in and you have to live with 30% of your bank capacity.

[Rainwulf]

Look on the bright side, you could be off grid and waking up 600 amp hrs in the hole after 4 days of clouds and 10 more days in the forecast. Oh yeah, it's all scaleable.

600ah in the hole.. holy crap. I still have grid power at my place, as my own off-grid project is just to run a server and a few bits and pieces... if i end up with a cloudy day i just turn the inverter off, and the automatic switchover relay drops it back to mains. I can still get 20-30 amps of charge on an overcast day, so my batts dont sit there stewing in their own flat acid.

[Willy T]

With the east coast about to get a good hammering from a storm it's always interesting to see how many solar users find out how their systems react. Some will get a real surprise when they wake up to a grid tied system and no power. Even the ones with battery backup and no ability to recharge get a wake up call.

[Rainwulf]

With the east coast about to get a good hammering from a storm it's always interesting to see how many solar users find out how their systems react. Some will get a real surprise when they wake up to a grid tied system and no power. Even the ones with battery backup and no ability to recharge get a wake up call.

The gridtie-no power thing is starting to be noticed here in aus. With SO MANY grid tie installations, people are wondering why they have no power when the mains goes out.
Its why tesla is bringing their powerwall here first, as we have some amazing sun here, and a huge grid tie installation base thanks to the government rebates a few years ago. In some suburbs you might only see 1 out of 10 houses without a 2-3 kw grid tie install.

[PNjunction]

Some will get a real surprise when they wake up to a grid tied system and no power. Even the ones with battery backup and no ability to recharge get a wake up call.

That brings up a good point - I wonder how many think about how important it is to conserve under these conditions, or just want to run the house full-tilt like they did on the grid? Powerwall or not, a little conservation training can be a good thing. Like turning the *backlight* on backlit lcd tv's down as far as you can stand it.

For instance, even those living on-grid with a solar off-grid backup should try a dry-run of just using the system for an entire weekend to prove if they can make it, or if they will want to drop the whole project and hit the nearest motel with power when it really happens?

As ridiculous as it might seem, those doing solar grid-tie and don't want any hassle with the existing grid-tie rooftop setup, changing hardware, permissions and the like, could just bite the bullet and DIY a smaller backyard ground-mount system for the basics to get them through. Just an option - although I know it would drive some crazy staring at all those panels on the roof when they have a make-do little backyard setup.

[lkruper]

That brings up a good point - I wonder how many think about how important it is to conserve under these conditions, or just want to run the house full-tilt like they did on the grid? Powerwall or not, a little conservation training can be a good thing. Like turning the *backlight* on backlit lcd tv's down as far as you can stand it.

For instance, even those living on-grid with a solar off-grid backup should try a dry-run of just using the system for an entire weekend to prove if they can make it, or if they will want to drop the whole project and hit the nearest motel with power when it really happens?

As ridiculous as it might seem, those doing solar grid-tie and don't want any hassle with the existing grid-tie rooftop setup, changing hardware, permissions and the like, could just bite the bullet and DIY a smaller backyard ground-mount system for the basics to get them through. Just an option - although I know it would drive some crazy staring at all those panels on the roof when they have a make-do little backyard setup.

Tomorrow SCE is taking the power down from 8AM to 6PM. I get to test out the UPS systems that keep my TV and Computer working and then after an hour or so, I will hook up my generator to my transfer switch and see how it keeps the cabin working, including my new fridge. I am looking forward to it.

Finally finished replacing all my incandescents and CFLs with Leds!

[PNjunction]

60-day report

Ok, so this is month two. The first month was spent discharging to only 25% DOD. The last 30 days I increased that to 50% DOD (roughly 20-25ah daily at the .10C rate).

No problems. Still, we'll see after a year. My prediction is that I'm just tearing this battery up 4 times as fast as I would with a yellow / blue top since it is not made for this kind of cycling.

Anyway, no drama from the battery yet.

[Mike90250]

Thanks for the updates

[SPFycool]

I'm curious how this works out for you too. I have actually been doing something similar in my shed.

I bought a massively discounted (75% off retail) Titan 40Ah SLI battery locally to test in my solar shed. I expect it to last a year or two MAX. I'm only about 6 weeks into my experiment though. I estimate my DOD is between 5-15% with a rare 25% DOD when I use it to power some small power tools. I only have a 30W panel and a cheap PWM controller, but they seem to be doing a good job keeping the battery at 12.9V after sundown.

So far so good. I expect some deterioration come Spring time though.

[bcroe]

As ridiculous as it might seem, those doing solar grid-tie and don't want any hassle with the existing grid-tie rooftop setup, changing hardware, permissions and the like, could just bite the bullet and DIY a smaller backyard ground-mount system for the basics to get them through. Just an option - although I know it would drive some crazy staring at all those panels on the roof when they have a make-do little backyard setup.

I don't see any connection between solar grid tie, and backup power. I want power when I want
it, not when (if) the sun decides to shine. The decades old generator does just fine, running it
every few hours takes care of the (propane) furnace, the well, and the fridge. No I can't use
the welder, the electric oven, or resistance heat; just trying to get through with reasonable
comfort and no damage. Certainly I don't want to be saddled with some battery PV system
that is practically never used, and adds big time maintenance to my list. Bruce Roe

[PNjunction]

I'm curious how this works out for you too. I have actually been doing something similar in my shed.

I'm just doing it out of curiosity since I'm operating well outside the design parameters.

Still, I did have the thought that *maybe* the degradation won't be as bad as predicted, because I'm using no more than 0.1C charge / discharge, which might be much easier on the sli-type grid-paste and other materials. In addition, it is getting fully charged each and every day (well, layman's full charge anyway) with a few extended floats when possible.

Time will tell - or until I get so bored that I trade it in as a core exchange for something else.

[SPFycool]

Time will tell - or until I get so bored that I trade it in as a core exchange for something else.

Pretty much the same for me. My setup could be classified as the sacrificial/learning phase now. Had parts laying around that I wanted to put to use for a small fall project on my shed. Didn't want to bother running an ext. cable (dogs would probably chew it anyway) to my shed. See what my 30W panel, HQRP 10A PWM controller and a cheap SLI battery would do.

Out of curiosity, I brought the battery inside a few days ago and connected it to my charger/maintainer. Even though the PWM controller show full at 12.9V, the charger ran the bulk charge stage @ 4A for almost an hour. Absorption stage took another hour. I disconnected it and let it sit overnight to check resting voltage the next day. It settled at 13.06V.

So I guess my PWM controller either doesn't have the correct logic to float charge the SLI battery, or the panel wasn't outputting enough current to complete the charge cycle even though battery LED was flashing green (I assume that means float). Though 12.9V to 13.06V isn't a HUGE difference. Maybe 95% charged or so from the panel. Not sure how quickly that would degrade the battery over time. At such light usage (maybe twice a week to 15% DOD) or once a month to 25%, I'm not really worried about eating up cycles anyway.

[PNjunction]

Well, that battery will most likely sulfate and walk itself down if you haven't done your homework first, nevermind that it is an sli type. Good thing you put a charger on it.

What exactly is your battery manufacturer / model #? Is it new, or was it used?
What is the charger make model?

Ideally, how much current does the fan draw, and how many hours per day are you using it?
And finally, where is your location - close is fine enough - to determine how many hours of solar-insolation you have (these are different from sunrise to sunset).

So even at the small level, instead of winging it, we can get in the ballpark so that your battery doesn't die a premature death - although the charger will save it perhaps.

[SPFycool]

The battery is an Exide Titan. LINK It was 'new', MFG date Dec 14 when I picked it up in September. Discounted to $22 from $90. The core charge was almost as much as the battery itself. I knew this was a short-term battery from the get-go so for the cost of a case of beer I could power some tools and get my solar feet wet.

The charger is a Battery Doc 2/4/8AMP charger/maintainer. LINK

I don't have a fan on it. Just using it to power a couple small sander's, charge a laptop, cell phone, some 1-2W LED's, really not much at all. I use between 20-75Wh and maybe a bit over 100Wh once or twice so far when I charged up my 40V mower batteries.

I'm in RI, USA. The panel is facing due South, but I have trees on either side of the Horizon. Mostly unobstructed sun between 8am and 2pm.

I may just store the battery inside over the winter to keep it topped up and use it again in Spring after I finish my shed project. Not like i'll be working in a un-insulated sub-freezing anyway.