Using 4 cell 18650 li-ion with 4 100W solar panel

[PNjunction]

What timing!

Our friends over at CPF (Candlepowerforums), specifically HKJ with his outstanding reviews, tests the Soshine 3.2v LiFeP04 26650:

http://www.candlepowerforums.com/vb/showthread.php?427483-Test-review-of-Soshine-IFR26650-3-2V-3200mAh-(Pink)&s=7fb377857e660a8f652f85a25c574ac3

You'll find this interesting. We are also assuming that your supplier did indeed supply REAL Soshines, and not fakes.

While the test goes up to a very high current level, here we are more generally concerned with long-term low-current housebank usage - like at .05C or perhaps less when you figure in day(s) of autonomy.

Anyway - have at it with your test gear. Still, keep wallet closed until you are absolutely sure that LFP in the first place will actually meet your needs, whether diy or commercial.

[PNjunction]

...EDIT: As I'm doing the maths with the true 2500mAh results $420 worth of these soshine cells would get me true 75Ah 4s, with 30 26650s per cell. YIKES, that's a lot of batteries I think, lots of weight.. The benefit I'm seeing here is the ability to shape the battery for the boat hull, otherwise it seems like a better bet to buy a ~$6-500 100Ah LFS meant for like a lead acid drop in, although I suspect these batteries are rated high too, 100Ah more like 60-75Ah anyway? If that's the case then I'm saving 200$ with this method but I have to build the pack.

Heh, at least you have a good tool to experiment. Most manufacturers in this league overspec the capacity. Maybe try a different brand. I got about 3100mah or more from Kingsolar's. But this is small stuff.

voltage sagged back down to ~3.43V per cell and 13.734V total. Seems like a pretty minimal gain for lowering the end current and upping hte voltage.. 2661mAh vs 2742mAh

That's a normal resting voltage for an LFP cell that is nearly fully charged. Not super accurate, but normal enough to spot a trend right off the bat if it were significantly lower. Or, 13.7 to 13.8v after a rest. And of course significantly higher like 3.5v or more per cell after a healthy rest means you overcharged it. Discharge it some immediately if you want any sort of cycle life from it if you are resting after 12 hours above 3.5v or so. You're doing ok.

I'd say I can expect to safely draw 2400mAh from these cells, although I will lose a tiny bit of capacity charging to 14.2 with a solar charge controller vs 14.4

What you'll quickly find out if you do a lot of testing is that any charge rate from 3.45 to 3.6v per cell only means a small reduction in time to fully charge to an end current target (unless the iCharger prevents that - mine will only do charge current / 10 at best. The overall results will be the same - just a time difference.

I think next I will try to cycle the battery without any balancing and see how well the cells keep balanced. The voltage sag after fully charged on LFP blows me away, it's clear how different this chemistry is to lithium polymer.. I actually use a 3 cell soft pack LiFePO4 in my RC radio.

I think you'll be surprised, as long as you don't have a total runt in the pack. But yes, you are taking a chance that if one of the Soshines or Kingsolars fails and turns into a shorted busbar, the two-terminal charging will totally overcharge the remaining 3. Or if you lose any sort of LVD, it will go reverse polarity. It is a risk one takes and the price to pay for KISS methods. This means you have to buy from reputable dealers with quality product in the first place.

You are doing well to question the cost / construction benefit from this experiment. Keep your cell count down, so a boat-full of Soshines may not be the best idea. Perhaps Headways. Or larger prismatics. Or as much as I dislike them, "drop ins". Just make sure of what you are getting. I'll bet the Victron LFP batteries are much better than some fly-by-night outfit never to be heard from again after purchase.

So just be careful if you go the drop-in route, since now that the whole thing is black-boxed, you have no way of confirming the quality of the cells they use internally. Plenty of fake A123 pouches with tabs cut off, zipper fuses missing, or decrepid old 26650's from motorcycle starter LFP, retack welded together, rewrapped, and case is sealed. A so-called BMS that cost less than a penny to make. You know what I mean.

So the thing is, if you go the DIY route, at least you know what you are getting up front - but if your construction / engineering skills aren't up to the task, just acknowledge it and go commercial.

Give your test rig some more time. The cost of this whole thing is going to paid back handsomely in first-hand, hands-on knowledge. Hard to get these days.

[drpatso]

Hey thanks PNjunction! Super stoked to be on the right track with batteries.

• series polarity looks good, quite familiar with parallel / series wiring
• balance plug is working, just experimenting here. I do not plan on balancing for the final battery
• being careful not to damage the shrink wrap, I had the pleasure of dismantling a hoverboard battery so I'm aware of the danger
• I'm impressed with the results for $3.50 per cell on eBay. I'm not sure if any of these 26650s do actually put out their rated 3200mAh, and if true A123 does, is it worth the extra cost for a project that is doomed to get lost at sea at some point.

EDIT: As I'm doing the maths with the true 2500mAh results $420 worth of these soshine cells would get me true 75Ah 4s, with 30 26650s per cell. YIKES, that's a lot of batteries I think, lots of weight.. The benefit I'm seeing here is the ability to shape the battery for the boat hull, otherwise it seems like a better bet to buy a ~$6-500 100Ah LFS meant for like a lead acid drop in, although I suspect these batteries are rated high too, 100Ah more like 60-75Ah anyway? If that's the case then I'm saving 200$ with this method but I have to build the pack.

I discharged and charged it while playing some rocket league tonight.

1st attempt, Note it was about 20F in Boise today, so I'd think my garage was somewhere around 35 degrees Fahrenheit

discharge rate: 2A
discharge time: 1hr 17min
end voltage: 2.55V
discharge: 2481mAh

Wasn't happy with that, thought it might have some more left in it and well, the final battery will be huge so I'll discharge again at it's current level at .5 amps

2nd discharge attempt on the same charge.

discharge rate: 0.5A
discharge time: 22min
end voltage 2.5V
discharge: 180mAh

2661mAh total draw from that charge.

When I went to charge it I went a bit more aggressive just to see what happens

end current: 4%
end voltage 3.65V per cell ( I know 3.6v is the safest but I had to for science)
charge current: 2.5A
charge time: 1hr 25min
capacity: 2742mAh,

voltage sagged back down to ~3.43V per cell and 13.734V total. Seems like a pretty minimal gain for lowering the end current and upping hte voltage.. 2661mAh vs 2742mAh


I'd say I can expect to safely draw 2400mAh from these cells, although I will lose a tiny bit of capacity charging to 14.2 with a solar charge controller vs 14.4

I think next I will try to cycle the battery without any balancing and see how well the cells keep balanced. The voltage sag after fully charged on LFP blows me away, it's clear how different this chemistry is to lithium polymer.. I actually use a 3 cell soft pack LiFePO4 in my RC radio.

[PNjunction]

OUTSTANDING! You get it!!

Those pics almost brought a tear to my eye. That nearly emulates my own test rig exactly. The only difference is that my cells are, um 3300mah "Kingsolar", LiFeP04's <grin>, and the holders have nickel, and not gold contacts like yours. Heck, I'm even familiar with the iCharger as I use a model 306B. Instead of electrical tape, I use velcro straps to keep it cleaner.

WARNING WARNING - Take it easy inserting those cells, and be SURE to get your series polarity right obviously. Just saying - because it is so easy to insert and remove them, you don't want to be in a hurry. Hey, how come I'm only reading 10v ???? OH CRAP! You don't have to ask me how I know.

Once you have determined that the Soshines are somewhat equal in capacity and IR (the iChargers do a good job of baselining that) for a sanity check, you can start to trust your results.

Some hints: since these cells behave nearly exactly like our larger GBS, Winston, CALB (except for the higher end) brethren, you can get a good handle on what to expect should you want to scale it up with large prismatics. And it will provide confidence in what you are doing if you actually do shell out the $$$ for those.

Now you can play the balance bleed-charge game. Which at least is 100% better than having vampire boards sitting on top of those cells all the time!

Next, once you are confident, you can experiment with only two-terminal charge / discharge, keeping an eye out to stay out of the knees. We've covered all that before. Note: even though the Soshines spec at 2v, yeah, don't go there. Give yourself a hedge at least 2.5v, preferably 2.8v being the minimum. We are playing with basically garden-solar cells at this end of the spectrum.

HINT: Just be aware that the iChargers will stop at only either a C/5 or C/10 end current. Take this into account when choosing a charge current, as C/20 is the usual manufacturer minimum for capacity. Huh? 3300 / 20 = 165ma end current. Thus, no more than 1.65a should be chosen when using the iCharger set for the longer C/10 charge. That's about a C/5 charge rate for these cells, so while they can take 1C, you won't fully charge them with the iChargers C/10 end current setting. Heh, see what I'm saying? Personally, if I was trying to measure discharge capacity with the iCharger, I'd only charge up first at low rates.

I know I threw a lot of "C" around there, but read it slowly. The iChargers kind of threw me at first when determining a proper end-current means determining a proper charge current first.

For total overkill, I also vet my cell voltages under charge with a Fluke (safely!), to make sure my iCharger isn't lying to me.

Congratulations. You have a fine test-jig to play with LFP, with some amount of safety and sanity, PROVIDED you take it slow when initially installing the cells into the holder to make sure you got it right. Perhaps use a silver-sharpie on the holders to clearly indicate polarity, and mark the cells as such as well.

Also note that these garden-solar-light 26650's, are not quite as robust as a *TRUE* A123 LFP, so treat them with a bit more kindness. Also note that Headways are another story, as they are very high-C rate cells, quite unlike ours as well. Similar overall LFP specs, but A123 and Headway are aimed for a more high-C environment.

... wipes tear from eye ...

[drpatso]

Thanks all for pointing me in the right direction. I have my first battery prototype, a 4s 26650 LFP. They are soshines which are suspiciously cheap, I charged them up last night and will be running a dicharge test later tonight. You can get these for $3.50 a pop on the eBay. They took around 300mah to reach fully charged voltage of 14.4 from the charge level they arrived at.

[mike3367]

i knew the battery's were fake. only paid 8 bucks for 16 of them, but like i said was just doing testing. i hooked them up and they are only 355 mah on average . i wasn't saying buy the battery's was just showing the battery bloc's. im sorry about the confusion

[PNjunction]

More research on the FAKE batteries. They are fakes of fakes! Also quite common.

Here is a test the op can do like this guy did with the latest 9900mah from GTF. Note that the fake of the fake mispelled the "T", and are now GIF. Apparently same claim to being flashlight experts. Hard to tell who is faking who. Even the hobby-chargers themselves can be counterfeited. About 5min in for result.

https://www.youtube.com/watch?v=hWmy-MWRZZc

EVEN IF they were real quality batteries, the lifecycle of non-lfp batteries is extremely poor and not suitable for your average solar housebank.

The magnets are nickel plated and the steel plates are zinc plated. Clamping pressure is provided by the nylon nuts and bolts. The common household nut and bolt hardware have nothing to do with the electrical conductivity. Google search "batterybloc endless-sphere" to see a discussion about this battery connection system.

Problems. Maybe best to leave this non-solar ebike app to those guys. Assuming PERFECT flat contact between the magnet and the anode/cathode surfaces with no oxide degradation, what is the voltage drop of the magnet under load / no load / and heat conditions? I'm assuming cell and overall voltage detection is post-magnet, so will that create any problems with a chemistry like this that is highly critical of overcharge? Is each magnet tested for compliance by the maker to make sure there are no duds / weaklings in the batch?

My own tests with my iCharger 306B and rare-earth magnets in this configuration had differing voltages depending on whether you were measuring at the terminals, or post-magnet, especially under load / charge.

The question is, would YOU be willing to reconfigure your own housebank with intervening magnets?

At any rate, I guess best to let the op speak for himself. A discharge test of each of those "GIF" cells would be interesting.

ALL of these issues go away, and increase safety if you change chemistry to LiFeP04, and get something along the lines of a 4S set of LFP Headway cells going, their mounts and links if you want to diy. Sometimes it is best to review the application, and start over.

And again, no disrespect to Mike, but by being fooled with fake batteries right at the start, shows that he needs *real world* lithium safety guidelines. Like a fuse for one, but perhaps that is out of the picture.

[karrak]

Ugh. Some dude with a spot welder, and his homebrew blocks, catering to the DIY ebike crowd. I should have known.

OMG. If not spot welded, they are using steel connecting plates, and common household nut and bolt hardware. In addition, the blocs are only held in place by magnets sticking to the anode and cathode. Can you say HIGH RESISTANCE? Even from an ebike stance, has NOBODY ever questioned what happens when you use these things in high humidity environments and there is a nice oxide layer developing?

The magnets are nickel plated and the steel plates are zinc plated. Clamping pressure is provided by the nylon nuts and bolts. The common household nut and bolt hardware have nothing to do with the electrical conductivity. Google search "batterybloc endless-sphere" to see a discussion about this battery connection system.

Would be nice for there to be some maximum voltage and current ratings on the website for this battery connection system.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger
Latronics 4kW Inverter, homemade MPPT controller

[karrak]

Do not rely on any passive-resistive balancing features inside that dinky little voltage monitor! They are TOO SMALL in the first place, and if any cell gets out of balance, will subject the other healthy cells to too much TIME waiting for the laggards to catch up. Instead, use your charger's balance leads. The lack of balance leads from the charger caught my eye right off the bat. And truth be known, most of their resistive balancers are too small for a battery of what you *think* you are using.

Balance - Now that you have paralleled 4 cells for a larger-capacity cell, how well are you going to balance if just ONE of them is sitting at 50% DOD perhaps? I'm sure you charged each one before assembly, but with those 9800mah fakes, this could easily happen and how do you suppose those cells will react? Since you are not putting any sort of balancing on EACH cell, if something like this happens with those fakes, you, anyone near you, or your property is in danger.

If you look at the original photo you will see a standard RC charger with balance input connectors. I would assume that mike3367 is using this to charge this battery. Most RC battery chargers will be able to balance this sort of battery and will not let any individual cell voltage go out of its safe operating range if the battery balance lead is connected to the charger.

I would think that the pack is connected to the DC-DC converter that mike3367 mentioned in his post. The "dinky little voltage monitor" voltage monitor will give an alarm if any of the cells go outside the normal operating range.

So it looks to me like mike3367 has thought about the safety aspects of this supply.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger
Latronics 4kW Inverter, homemade MPPT controller

[PNjunction]

.... <snip> this is where i got them he also has a you tube page showing how to use them

Ugh. Some dude with a spot welder, and his homebrew blocks, catering to the DIY ebike crowd. I should have known.

OMG. If not spot welded, they are using steel connecting plates, and common household nut and bolt hardware. In addition, the blocs are only held in place by magnets sticking to the anode and cathode. Can you say HIGH RESISTANCE? Even from an ebike stance, has NOBODY ever questioned what happens when you use these things in high humidity environments and there is a nice oxide layer developing?

I watched the videos. This is an accident waiting to happen, EVEN IF you are using real cells. I'd request a removal of the link as those batteryblocs are an outright danger.

No disrespect to Mike3367. He just doesn't know the dangers, and why the last words he says to the fireman, was that "it seemed to be working well".

And for the smarties in the crowd, no - switching to "protected" cells won't be safe either. Those circuits are all too commonly faked as well.

Mike - just STOP bro. Rethink, do some homework and redesign.

[PNjunction]

Mike3367 - here's what you do in the interest of safety.

First, visit this forum to get schooled on how to identify fakes. Also see the excellent reviews by op HKJ of what REAL 18650's do:

http://www.candlepowerforums.com/vb/...eries-Included

Safely discharge your fakes, and MARK them as bad and recycle. This way, dumpster divers may have second thoughts about recharging them.

It appears like you are just trying to make a nominal 12v battery setup. But by using the wrong lithium chemistry with higher nominal voltages you have to resort to dc-dc converters.

Instead, use LiFeP04, with it's nominal 3.2v rating (3.6v max charge), and make a simple 4S battery. You can ignore the dc-dc converter now.

Your charger should have setting for LiFe, LiFeP04, or in some cases is labeled as "A123", which is lifepo4. Do NOT use "lipo" or the like, which is the wrong voltage.

Choose your desired capacity, and strive to reduce cell count to minimize the rat's nest. Ideally, get cells that meet your capacity needs in the first place. You may want to look into Headway LFP cells.

What I suspect is that you got suckered into thinking you can make a lithium ion battery on the cheap, and the vultures saw you coming. Hit up Candlepower to get some background and do your project right. Change your chemistry to LFP and simplify, simplify, simplify.

[PNjunction]

i am testing a 18650 16 cell battery i made. so far for such a little battery it doing pretty well. i have it set up as a 16 volt battery, and run it thru a dc to dc converter that does constant voltage. the balance charger im using, just hooks up to my battery bank. it takes 11 to 18 volts in to make it work

STOP RIGHT NOW!

Look at your cells. There is NO SUCH THING as a 9800mah 18650. What you have are dangerous fakes. At the very least, purposely mislabeled to fool the unknowing. Do not trust those cells in the first place.

Do not rely on any passive-resistive balancing features inside that dinky little voltage monitor! They are TOO SMALL in the first place, and if any cell gets out of balance, will subject the other healthy cells to too much TIME waiting for the laggards to catch up. Instead, use your charger's balance leads. The lack of balance leads from the charger caught my eye right off the bat. And truth be known, most of their resistive balancers are too small for a battery of what you *think* you are using.

Balance - Now that you have paralleled 4 cells for a larger-capacity cell, how well are you going to balance if just ONE of them is sitting at 50% DOD perhaps? I'm sure you charged each one before assembly, but with those 9800mah fakes, this could easily happen and how do you suppose those cells will react? Since you are not putting any sort of balancing on EACH cell, if something like this happens with those fakes, you, anyone near you, or your property is in danger.

[Mike90250]

..... How about making your own solar panels?......

Yeah, that's going to work like a champ for a ocean going test craft. The odds of being able to mfg and seal a DIY panel in ocean spray for a couple months voyage is ZERO

[karrak]

I'll let the cat out of the bag here. We have a hull design in progress and a pid controller on the rudder servo with input from tilt compensated compass, iridium satellite link, GPS, and voltage monitoring. This power system will hopefully be floating around the ocean next summer..

Now I'm at a complete loss.. I just want a light, cheap efficient method of storing the energy from 4 x 100W panels. The guy who made the sea charger has a 5 cell lifepo4 connected to solar panels directly to the 5 cell pack with a balancing circuit, maybe that's not a great method but the thing has been out at sea and running for months and months. Ofcourse fire is a concern but it'll only kill the ship, I have considered lithium polymer as you can get 14.8V 16Ah for 50$ now.

I have had more of a look at the HQST/etracer MPPT controller and you can set up any voltage between 9-17 for 12 volt operation and 18-34 volt for 24 volt operation using the "User" battery type option. This gives you allot of flexibility of what battery you can use.

I agree that getting a decent commercial programmable BMS preferably with remote access is a pain! That is why I designed and built my own. There are a few other open source BMS systems around, not sure if you want to go down that route.

What exactly do you mean you have voltage monitoring, could you use this to monitor the individual cell voltages?

On first glance using the 5 cell LiFePO4 option on a 12 V panel doesn't seem like a particularly good option as the maximum panel voltage Voc could be around 22 volts which equates to 4.4 volts across each cell. Now if you could get a panel with a Voc of around 18 volts that arrangement could work quite well. How about making your own solar panels?

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger https://github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[mike3367]

www.batteryblocs.com this is where i got them he also has a you tube page showing how to use them