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Off grid batteries - test results

Off grid batteries - test results

Off grid batteries - test results

This is pretty damning



...The reports clearly show that many batteries have been inadequately tested before being put on sale. Problems have included:

- Difficulty physically installing and connecting batteries.

- Problems with communication between batteries and inverters.

- Parts vital for installation that are not “off the shelf” haven’t been supplied with batteries.

- Instructions for installation were often not included with batteries or were inadequate.

- The majority were not delivered on time.

- Testing has shown some batteries losing capacity or “fading” rapidly. This may result in many future warranty claims for currently installed battery systems.

One area identified as being desperately required is standardised protocols for communication between batteries and inverters....


Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Off grid batteries - test results

There is definitely a lot of garbage being sold into the battery market at present- it's an early adopter Wild West akin to computers in the early '80s. Suppliers going out of business and not supporting their product, shipping defective or incomplete product, offering warranties that their product can't meet etc.

The good news in that report was that if you buy a product of a reputable brand (LG Chem, Samsung), the cycle life is looking good, i.e. beyond the ~3,000 cycles to 20% capacity loss that is likely the limit of a Li ion battery unless you refrigeration cool them. They are also reporting a 92% efficiency, excluding inverter losses on the output. The shocker was the terrible performance of Tesla's Powerwall 1- dreadful cycle life...

RE: Off grid batteries - test results

Nice report. There's so little real info on these things that I've been afraid to pull the trigger. We have a place in Puerto Rico that screams for solar.

RE: Off grid batteries - test results

I got the best deal ever just recently.

Our electric boom lift's lead-acid pack was nearing the end of its service life, with one of the six 6V L16 batteries having lost a cell. So we swapped out the entire pack, and I got to choose two batteries in return for paying the "core charge"- which I'll of course get back again when they are actually finally dead. My little garden lights/fountain pump/emergency back-up for my sump pump and hydronic boiler just got a huge boost in capacity for basically zero dollars...

I would imagine that a polite conversation with a company which maintains forklifts, scissor and boom lifts (perhaps accompanied by a case of beer) would give access to many such batteries, which won't last forever but which will be happy to supply a few Ah at low currents in their retirement, as long as they are properly maintained by a solar charge controller.

RE: Off grid batteries - test results

My experience, talking to folks who run forklifts and similar electric equipment, is that they get used and abused until you just can't get your employees to deal with them anymore. By then the batteries are just too far gone. They would consider giving them away to an innocent bystander only when they see it as getting you to remove their problem for them.

I have successfully used a very different strategy. Like automobiles coming off of a lease, and like wide-screen televisions at christmas, there are people who will just get rid of something because, in their minds, "time is up". This seems to be true for back-up and UPS battery systems, when they are run by corporations such as ISP's, grocery stores, and urban emergency services. Consider the cost to them if the backup doesn't work, and you can appreciate their motivation to guarantee the up-time. So they do things like dispose of perfectly good batteries because the warranty expired. This is your opportunity to step in and remove the so-called old batteries. That is how I received about 19,000 kW-hours of batteries, and I've given them TLC ever since.

It's important to note that the kinds of companies I listed tend to have battery back-ups installed by electrical contractors who are very specialized and not likely sympathetic to your desire. They have probably already paid for the removal service, maybe even contractually obliged to it, and it's very difficult to insert yourself into that transaction, especially as an "innocent bystander". You have to know the right people, be lucky, persistent, and prepared to arrive with your own forklift within, at the most, 30 minutes, otherwise you are just inconveniencing everyone. I may not get the same opportunity I had again.


RE: Off grid batteries - test results

Back, after reading the article (and helping my neighbours move their fridge)...

That's a terrible track record for so many residential battery sets. In defense of the suppliers for at least one complaint, delivery from anywhere in the world to Australia is difficult at best. When handling such heavy items, consider the customs officials mucking about with every shipment. Much of the delivery time is not under the supplier's control (though in the case of Tesla, I also don't believe they were shipped on time).

They also seem to be choosing the "bottom dollar" cells for their tests. They point at problems with the GNP Sonnenchein - which are gel=cells known to be the most vulnerable to temperature variations. All lead-acid gel cells should be kept indoors under controlled temperatures. Their test with floating temperatures is not fair. Exide/GNB has some very high-quality batteries, able to withstand 1,200 cycles @ 80% depth of discharge and they claim design life 20 years. I believe it, because my "free" Absolytes are 25 years old.

Otherwise, thank you Greg for the article. Valuable "real life" testing.


RE: Off grid batteries - test results

SparWeb: all four of the batteries I salvaged charged up to the full balance charge voltage. My two are happily purring along under the watchful eye of my solar charge controller- they accept and deliver charge just fine, at the low rates I'm asking of them. What their ultimate capacity will be when I put a 500 W load on them for 30 seconds every half hour to run my sump pump until the power goes back on is anyone's guess, but I'd guess that its still several times the capacity available from the 80 Ah marine battery I had for this purpose beforehand. And when they die, a local scrapyard will give me over $60 each for them based on their weight, which is over twice what I paid for them. Best deal ever as far as I'm concerned!

RE: Off grid batteries - test results

Well done! What type batteries?
The sump-pump load doesn't sound very extreme. If run like that for days/weeks it could depend more on the solar panel capacity than the battery storage.


RE: Off grid batteries - test results

They're L16 sized 6V lead acid batteries (floodies) from our Genie boom lift. They weigh about 110 pounds each- fortunately I didn't know that when I lifted them into and out of the trunk of my Spitfire to haul them home... I paid $25 each for them...I took two and my neighbour took two, and we ran his backup sump pump by way of an AC inverter. The draw was 500 W and the batteries hardly noticed...

The solar setup is mostly for the fountain pump and garden lighting (and my own education/amusement). The sump pump backup is a secondary benefit- I had already hooked that up. The secondary pump is actually a 2000 gph 12V boat bilge pump with its float set higher than the float for the main AC pump- and it discharges to the sanitary sewer by way of the laundry tub. So I have a back-up against loss of power, against a plugged discharge hose (which happened once already- a check valve flapper broke off and turned it into a "don't allow flow in either direction" valve...), and against a failed pump too. Important, as during heavy rains the pump does need to run frequently, and they don't last as long as even a pessimist like myself would expect. Water would way rather flow down into the fill beside my foundation than into North York clay till- it's a bastard, as I discovered when I had to dig my own underpinning trenches in the gawdforsaken stuff by hand...I lost 20 pounds in a month doing that. Gained it all back and more though...We store about 200 gallons of this water to use on my wife's gardens and hanging baskets. As I get bored I build more automatic watering stuff so we can go away without having to bother someone to come water for us.

RE: Off grid batteries - test results

And here's some data I've been looking for for a long time. This explains why my laptop batteries last forever, because I basically don't use them. The interesting point to me is if you multiply DoD by cycles, you get a total number of electrons. Then you can figure out the most cost effective battery size for a given application.



Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Off grid batteries - test results

Actually, Li ion batteries don't like being kept at high SOC especially when hot, so not using a laptop battery is a good way to kill it. Get it to 50% SOC and then don't use it- that is optimal for battery life. Cycling does result in capacity fade too, and for multi-cell packs, deep discharge runs the risk that a cell will be reversed which is lethal to that cell and hence to the pack.

RE: Off grid batteries - test results

From that Battery University article:
"Environmental conditions, not cycling alone, govern the longevity of lithium-ion batteries. The worst situation is keeping a fully charged battery at elevated temperatures. Battery packs do not die suddenly, but the runtime gradually shortens as the capacity fades."

Lead acid batteries? Totally different animal. They like being kept at high SOC and they like shallow cycles. There's a "maintainer" charge pattern that optimizes their life.

RE: Off grid batteries - test results

We just decided to put lead acid batteries in a portable measurement unit. Even if the "heart" needs only 1.8 or 3.3 V and it would be a nobrainer to fix that, we also need to supply a few other things. Sealed lead batteries have been used for so long, and field-proven, that we feel confident that they will stay until our unit needs to be replaced because it gets out of fashion.
An unexpected plus is that the box now is more easy to manipulate. With the smaller and lighter options it yields and slides away when you touch the panel buttons.
This is not about solar, though.

Gunnar Englund
Half full - Half empty? I don't mind. It's what in it that counts.

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