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

[PNjunction]

Well, ok - for learning purposes - even though the battery is NOT ideal for solar being an SLI, we can work with it:

Having no 20ah rating on it, all we have to go by is the "RC" value. That model has an RC of 70, which we can get into the ballpark rating with

70 * 0.6 = 42ah approximate. Only half of which is usable, so 21ah usable down to 50% DOD. (The 0.6 multiplied by RC gets you the ballpark value)

Or, put another way, in watt-hours:

42ah * 12v = 504wh. Again, only half of that is usable, so 252 watt hours. Keep this for reference.

A flooded battery should be charged between the C/12 to C/8 window for current. Thus, your 42ah Titan wants to see anywhere from 3.5 to 5.25A charge current. Go lower then 3.5a, and the battery stratifies. Go higher than 5.25A, and the battery burns up.

30 watt panel? A nominal 12v / 30 watt panel is in reality about 30 / 18v = 1.6A absolute best case, so you are well under the minimum. You actually need about an 80 watt panel, otherwise, your little panel is just acting like a little maintainer, and not really charging other than superficial surface charge. Set your charger to the 4A setting for best results.

See how even at the small end of things, details add up?

[SPFycool]

Yeah. Thanks for breaking it down!

I initially had an 18Ah battery lined up that was pulled from a UPS pack (again only for testing). It appeared good until I placed a load on it and it fizzled.

I won't be purchasing a bigger panel anytime soon as i'm not delving seriously into solar just yet. It seems the nominal battery size is between 12Ah and 18Ah for my panel. I have seen some so-called deep cycle batteries in this range on Amazon, but I doubt they are truly deep cycle. Most are classified as electric wheelchair batteries and don't list cycle data.

I'll probably stick with the current setup for a bit and put the battery on the 4A charger once a month or so. The Battery Doc has a 'refresh' setting that actually appears to have brought *some* life back to another battery in a portable jump starter I keep in my car. I may run the refresh cycle after the full charge every month.

Let's see how long it lasts.

[PNjunction]

Stopped the test!

I stopped the test when I found that someone has already done this.

It basically reiterates what Hawker says about treating SLI agm's this way - you are only going to get about a year out of them down to 50% DOD.

Essentially, they are degrading 4 times faster than the proper dual/deeper yellows and blue tops. Of course if you take them down to a max of 20-25%, cycle performance improves greatly. Then again, why buy an SLI agm 2-4 times larger than need be to work with the advanced degradation in the first place?

I knew this going in, but wanted some hands-on. NO, they didn't just fail outright after a 60 cycles, no drama etc. They just degrade faster that's all.

AND, this is with full charges when solar wasn't enough, plenty of absorb and float (although no EV-like IUIa charging was done), but in the real world of solar, add that lack of a good charge to the equation.

Essentially, if you get one as a freebie and don't know what to do with it, just use it until it croaks. Or pull no more than 20% or less DOD from it, and be happy. Definitely don't buy one on purpose to abuse this way - which accounted for the change in warranty when some chose a red-top on purpose based solely on warranty, rather than choosing what's best for the application, to attempt the free-battery-for-life scam.