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

[drpatso]

Been digging through google for weeks and I can't find out if using a 4-6 cell 18650 battery pack is even feasible.

I can't seem to find any sub 300$ MPPT chargers that support lithium-ion. My 4s 18650 pack would have a nice high amperage BMC but from what I understand the BMC won't like the input voltage from an MPPT even if I can set the cutoff voltage to 16.8 (4.2v fully charged 4s)

What are my options here to store the solar energy in a lithium ion battery?

I'm thinking with 400W of solar panels peak time with 80% of rating (peak like 11am-3pm?)I'll be pulling down like 26amps at peak. A 65-75amp hour 4 cell (14.8V average) should be able to get charged from this, but how? Is my best option to switch to a 5s 16V lifepo4 hooked directly to panels?

[Sunking]

What are my options here to store the solar energy in a lithium ion battery?

I'm thinking with 400W of solar panels peak time with 80% of rating (peak like 11am-3pm?)I'll be pulling down like 26amps at peak. A 65-75amp hour 4 cell (14.8V average) should be able to get charged from this, but how? Is my best option to switch to a 5s 16V lifepo4 hooked directly to panels?

You have way to much wrong.
Last thing you want to use is LiCo, you use 4S LFP and use any charge controller you want set to 14.2 volts.

[drpatso]

You have way to much wrong.

Just because everyone else is using lifepo4? What's wrong with Li-ion? Good energy density, and with the right equipment no risk of fire.. This is what Tesla powerwall uses no?

[Sunking]

Just because everyone else is using lifepo4? What's wrong with Li-ion? Good energy density, and with the right equipment no risk of fire.. This is what Tesla powerwall uses no?

Tesla does not use LFP aka LiFePo4. No EV manufactures would use LFP. Tesla uses a hybrid LiCo 18650 cell made specifically for them.

You specifically said you wanted to use LiCo or anything but LFP. You did so with this statement

BMC won't like the input voltage from an MPPT even if I can set the cutoff voltage to 16.8 (4.2v fully charged 4s)

Either that or you have no idea what you are talking about. Solar users who are silly enough to use a lithium battery would use a LFP cell in either 4S, 8S or 16S configuration so they can use any Charge Controller made for lead acid batteries. LFP or LiFeP04 as you called it is a 3.6 vpc charge, not 4.2 volts. A 4S LFP battery is charged at 14.2 to 14.4 volts, exact same voltage as lead acid. at 1/5 the cost. No off grid person would be silly enough to use 18650 cells as that is very foolish. Nope they use Large Format Coffee Bag Cells inside a plastic case. They are forced to use Chi-Com cells made by CALB. A Chi-Com cost roughly 60-cents per watt hours. A 18650 cost 4 times that at $2.40 to $3.00 per watt hour.

You can do what you want, you are just going about it all wrong. The reason you cannot find what you are looking for is because it does not exist. No on eis going to use anything other than LiFeP04, and no one would use them is a 18650 cell above 2 AH. You mention 60 to 80 AH cells which is fine. Just buy them like these 80 AH cells from CALB. They make 20, 40, 60, 80, 100, 160, and 200 AH cells. One of the CALB 80 AH cells is going to cost you $140. No dang fool is going to build them with 18650 cells. It would take 40 to 50 of them in parallel and the nightmare of soldering them up. plus to add insult to injury cost you 5 x more than the CALB. That is why you are not finding anything.

If you use LFP, they are drop in replacement for Lead Acid. They use the exact same voltages so any charge controller can be made to use with them. You just need the ability to set all modes to = 14.2 to 14.4 volts. Not hard at all if you go about it the right way.

[drpatso]

Either that or you have no idea what you are talking about. .

OK, I started the thread off with trying to find out if charging a li-ion 18650 pack was feasible. A simple no would be fine instead of making me feel like an idiot. This is why I am here. I need help and I appreciate your time. I miss-typed and all I was saying is it seemed like a BMS (balance circuit) would not like the input from an MPPT charger meant for lead acid. Basically you've answered my question in that there are no MPPT or PWM charge controllers that are compatible with lithium ion cells.

I perfectly understand lifepo4 / LFP cell voltage vs li-ion cell voltages. That's why I asked at the end of my post (should I just be using a 5s LifePo4 hooked directly to the panels?) This is a method that has been done and works along with a BMS if you aren't familiar with the sea charger. www.seacharger.com

It would take 40 to 50 of them in parallel and the nightmare of soldering them up. plus to add insult to injury cost you 5 x more than the CALB. That is why you are not finding anything.

The method you shun IS the way to do it for DIY. Ofcourse you don't solder them up with wires you make a nice pack with nickel tabs and spot welder.

The 80Ah LFP battery you link is $155 shipped. That's just one cell, you're talking about a 80Ah 4s LFP battery that costs 600+ dollars. As a basic example you can get 40 26650 LFP cells for $148 on eBay at 3200mAh that's 128Ah if you wire them all in parallel. I'm sorry but shunning the method of a 18650 26650 series / parallel pack is just silly unless I was a professional business or trying to make money off this. This is exactly what you find in tons of battery powered retail items. (Drills, electric lawn mowers, weed eaters, hoverboards, e-bikes, ETC ETC ETC ETC)

I appreciate your time as you helped me understand that li-ion is just not going to be feasible but you are scaring users away from this forum. If you're going to take the time out of your day to help answer questions and point people in the right direction, why bother being a jerk? Ofcourse I have no idea what I'm talking about, that's why I came here.

Tesla does not use LFP aka LiFePo4. No EV manufactures would use LFP. Tesla uses a hybrid LiCo 18650 cell made specifically for them.

I was referencing Li-ion then said "this is what the tesla power wall uses no?" I didn't say anywhere that Tesla uses LFP. I didn't realize that Tesla was using anything but panasonic 18650 li-ion cells so this is a misunderstanding on my part. My theory was if big companies like Tesla nad solar city are using li-ion why is it such a bad choice? Honestly, li-ion 18650s are more mAh and just barely more $ than LFP 18650s. 4$ for a 1200mAh LFP and 7$ for a 3200mAh Li-ion.

[Sunking]

Basically you've answered my question in that there are no MPPT or PWM charge controllers that are compatible with lithium ion cells.

Wrong again, I never said any such thing. Every MPPT and PWM chargers will charge a LFP battery just fine. The problem is you do not know what a Lithium Ion battery is. Lithium Ion batteries is a useless term. It is like calling a Chocolate Layer cake just a cake. No one has any idea of what you are talking about. What kind of cake? If you want to use solar, use LFP batteries.

If you understood a 4S LFP battery charges at 14.4 to 14.2 volts with a 12.8 volts nominal is identical to Lead Acid batteries, You based your conclusion on using the wrong battery type lithium Cobalt. LCO charges at 4.2 volts per cell, while LFP charges at 3.6 volts.

So the answer to your question is yes you can use just about any charge controller made for Lead Acid batteries. FWIW when you buy a BMS, you must specify what type of Lithium battery you are using. If you already have one and it says it is 4.2 volts is not made for LFP.

Additionally you missed MPPT Charge Controllers doing your searches. Genasun makes them. For $150 you can have one. They have fixed output of 12.5, 14.2, or 16.7 volts depending on which Lithium Ion battery type you are using.

[drpatso]

Wrong again, I never said any such thing. Every MPPT and PWM chargers will charge a LFP battery just fine. The problem is you do not know what a Lithium Ion battery is. Lithium Ion batteries is a useless term. It is like calling a Chocolate Layer cake just a cake. No one has any idea of what you are talking about. What kind of cake?

There are over 1 dozen types of Lithium Ion cells on the market to date. Lithium Cobalt (LCO), Lithium Manganese (LMO), Lithium Iron Phosphate (LFP or LiFePO4). You stated 4.2 volts lumping all lithium cells together because you are unaware there are over a dozen types and each has a different charge voltage. 3.6 is for LCO and some LMO cells. LFP is 3.6 volts and nominal is 3.2 volts. Some lithium Ion cells charge as low as 2.4 volts.

If you understood a 4S LFP battery charges at 14.4 to 14.2 volts with a 12.8 volts nominal is identicle to Lead Acid batteries, thus compatible with your BMS. You did not understand that as you were looking at the wrong lithium battery type. LFP = 3.6, LCO = 4.2 charge voltages.

I get it, I am wrong about things, not saying I'm right about anything. When I said li-ion I was talking about a standard 18650 cell, such as panasonic https://www.amazon.com/NCR18650B-Rec...anasonic+18650.. These batteries that charge to 4.2V per cell say LI-ION in the product description so sorry for my ignorance there.My experience with batteries has been with RC and the terminology used is completely different from here. It seemed simple to me because a LiFEPO4 battery will say LIFEPO4 or a lithium polymer that will say LiPO... I didn't realize lithium-ion described ALL those battery types.

Product description of the 18650 cells
Max 3.7V 3400mAh Rechargeable Li-ion Battery-Green
-Brand Panasonic
-Color Green + black
-Material Lithium
-Quantity 4
-Type Lithium ion


Seems like we have major disagreements on pricing and the way to build a battery pack and that's fine. From what I am gathering the easiest solution for me will be some sort of 4s LiFePo4 battery (I've never seen anyone use the abbreviation LFP) with an MPPT charge controller set to cut off 14.2V (slightly under the fully charged voltage of 14.6V (3.65 x 4) to increase the amount of cycles I'm guessing?

Would something like this work along with 4 100W panels?

https://www.amazon.com/HQST-MPPT-Solar-Charge-Controller/dp/B01B28RV96/ref=sr_1_4?ie=UTF8&qid=1479703038&sr=8-4&keywords=mppt+charge+controller+30amp

[inetdog]

Lithium Ion is a very general description of a lithium chemistry battery.
LiPo, Lithium Polmyer, is a general method of constructing a lithium battery, mostly independent of the chemistry.
LiFePO4 is a very specific lithium chemistry that can be physically manufactured in a variety of ways.

Part of the conflict is that people are mixing the terms in a false opposition and getting very confused.

Note also:
1. The higher the specific energy (per volume) of the battery, the more dangerous it is if and when it breaks down.
2. Some chemistries have temperature characteristics that lead easily to thermal runaway when charging. Others generate short circuits internally when cycled incorrectly over time.
LiFePO4 is relatively insensitive to those problems and so is safer for DIY.
Some chemistries and constructions are dangerous even when done commercially by engineers who do not understand the trickier parts of the picture and when control system and battery engineers do not talk to each other. Boeing found that out the hard way.

[Mike90250]

.........

Would something like this work along with 4 100W panels?
https://www.amazon.com/HQST-MPPT-Sol...ntroller+30amp

Never heard of them, Looks fake to me, No input voltage rating, which is very important with a MPPT controller

[drpatso]

Thanks Mike, scratch the HQST MPPT charger. I guess my last 2 questions are:

When I find a good charge controller when using potentially LFP 26650s or huge single LFP cells in a 4s pack, do I need some kind of balance circuit on the pack?

Is there a charge controller you guys might recommend for 400W ( 3 x 12v 100w panels)? I was thinking 30 amps, since the panels would go over that maybe for an hour mid summer.

[PNjunction]

Been digging through google for weeks and I can't find out if using a 4-6 cell 18650 battery pack is even feasible.

Easy commodity item - I run a few myself. I prefer the ANKER brand of li-ion battery packs, since their 18650 cells are usually Panasonic or LG-Chem or similar high-quality cells. I use a generation back, the Anker "Astro" series, the E5 and E7 right now.

Charge via solar with a 21w folding panel. Also by Anker. There are others. 5v usb output regulator built-in to the panel. Direct attachment to the battery packs.

Why hack together what today is a common commodity item shipped to your door overnight if you want. Easy peasy.

No large panels - no mppt controller, nothing like that. Brainless operation for the most part.

I'm thinking with 400W of solar panels peak time with 80% of rating (peak like 11am-3pm?)I'll be pulling down like 26amps at peak. A 65-75amp hour 4 cell (14.8V average) should be able to get charged from this, but how? Is my best option to switch to a 5s 16V lifepo4 hooked directly to panels?

I run a small 40ah LiFeP04 nominal 12v 4S battery bank quite successfully from a simple 100 watt panel. GBS cells. Similar cells would be CALB. Different chemistry than what is in the Anker packs, which is important because if you don't differentiate the chemistries and their voltages, you'll definitely burn stuff up.

Do some more reading found right here to get the background you need, rather than having us write up a laundry-list of componentry. This way you'll know what you are doing, and be safe not only to yourself, but also to others. Close wallet. Start reading.

Actually, open wallet and pick up an Anker Astro battery pack, and a folding panel to satisfy your li-ion appetite. Close again and start reading before thinking about going big with lithium.

[karrak]

As far as I can see the HQST MPPT controller is actually a Tracer MPPT controller made by EPSolar who are based in China. I have installed a more upmarket version of their MPPT controller in a friend's LFP offgrid system that has been working well for over three years.

Ideally for a 12 volt LFP battery for the longest lifespan you want to set the charge/bulk/boost voltage to 13.8 volts and the float voltage to 13.4 volts. At a pinch you can use the "Gel" settings. I think you can set user programmable values via an external programmer. Here is a link to the manual https://www.epsolarpv.com/en/index.p...wnloadF/id/678

As with your RC batteries which are most likely Lithium Cobalt (LCO) batteries you have to balance an LFP battery before you use it and have some way of checking that it remains in balance and that the individual cell voltages do not go outside the voltage range 3.65-2.50 volts.

One big advantage of LFP batteries over LCO batteries is that you will get maybe ten times the lifespan if you use them conservatively. The batteries in the Powerwall are another lithium-Ion variant, Lithium Manganese (LMO)

One question springs to mind, what exactly do you want to use this power supply for?

Simon

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

[jflorey2]

Thanks Mike, scratch the HQST MPPT charger. I guess my last 2 questions are:
When I find a good charge controller when using potentially LFP 26650s or huge single LFP cells in a 4s pack, do I need some kind of balance circuit on the pack?

In general, yes. Most lithium battery BMSes provide some kind of balancing. This can be very simple (accurate zener function at 4.2 volts per cell) or complex (charge transfer.) They are often not needed for packs that start out well balanced, but will generally prolong the life of an average pack.

The issue here is that while lead-acid batteries can deal with overcharge by boiling off electrolyte (which can then be replaced) lithium ion batteries have no such mechanism. So if one cell has a slightly higher leakage than the others, it will drop in voltage, and will continue to drop until it is almost dead even when all the other cells are fully charged. At that point the BMS will look at cell voltages and shut the pack down to prevent overcharge and overdischarge. That will greatly restrict the usable range of the pack. (And while some BMSes do not offer balancing, ALL lithium chemistry BMSes must offer over/under voltage monitoring.)

People who use large lithium cells (generally LiFePO4) for home storage sometimes balance them manually, then forego any balancing at all in favor of monitoring the cells. If the cells get out of balance they rebalance them manually. Several people have had good luck with this approach.

So for 4S you are generally going to want to use balancing. There are plenty of good BMSes out there that will do this for you.

Is there a charge controller you guys might recommend for 400W ( 3 x 12v 100w panels)? I was thinking 30 amps, since the panels would go over that maybe for an hour mid summer.

You are going to want an MPPT charge controller just because of its better control of output voltage and current. Make sure the input can deal with your voltage from the 3 panels in series. Then you are going to want to set the voltage to approx. 16.8V for a 4S lithium cobalt pack (or 14.6V for a 4S LiFePO4) and you are going to want to set the max output current to less than the maximum C rate of the pack. If the pack is 10ah and has a maximum charge rate of 1.5C then limit the maximum current to 15 amps.

[PNjunction]

In general, yes. Most lithium battery BMSes provide some kind of balancing. This can be very simple (accurate zener function at 4.2 volts per cell) or complex (charge transfer.) They are often not needed for packs that start out well balanced, but will generally prolong the life of an average pack.

Bzzt. Most balancing circuits are the CAUSE for killing packs. The "balancers" are what kills them. The balancing circuits are too small in the first place, vastly extending the time to do a so-called top balance and turn into vampire parasitic draw cell killers. They are frequently out of spec within regards to each other. And when they fail, all hell breaks loose, unbeknownst to the owner who likes watching blinky lights. Or watch their EV which operated ok for a month go into flames as their infrastructure burns first, regardless of which li-ion chemistry they choose.

This lesson was learned many years ago. Most newcomers to LFP and lithium in general disregard the effects of TIME, coming from a Pb based world to their banks detriment.

In other words, even if the balancing circuits don't fail, they are usually too feeble to do the job quickly enough cycle to cycle, extending the time the OTHER cells spend at high voltage twiddling their thumbs waiting for the feeble balancer to bring the lower cell(s) up. This time factor is what the marketers of balancing boards don't tell you.

Well, we know one thing. No mention was made about DISABLING temp-comp with your typical Pb based controller you mentioned, which usually incorporates that.

You know that you can fully charge a 4S LFP cell anywhere from 13.8v to 14.6v right - the only difference being that of time to absorb to reach full charge. Again TIME is the factor here, so a fixed voltage is not always the right answer with LFP. It depends on your application. and of course assuming good balance in the first place.

Much of this has been discussed elsewhere here.

My biggest issue is that we can't just toss out a laundry list of things to buy to someone who doesn't have a clue about li-ion in the first place. It isn't that easy from a financial and safety standpoint.

The second biggest problem I personally faced when getting my LFP setup going, is that most of the material passed to me came from well intentioned NON-OWNERS, who were just repeating back tech specs that "should" work, when in fact they were wrong, or at most ineffective.

[jflorey2]

Bzzt. Most balancing circuits are the CAUSE for killing packs. The "balancers" are what kills them.

Completely wrong. You are talking about consumer grade junk, not the balancing circuits used in most lithium-ion batteries. Contrary to what some think, battery, EV and renewables designers are not fools, and would not add devices to their batteries that reduce their life (and thus cost them money.)

The balancing circuits are too small in the first place, vastly extending the time to do a so-called top balance and turn into vampire parasitic draw cell killers. They are frequently out of spec within regards to each other. And when they fail, all hell breaks loose, unbeknownst to the owner who likes watching blinky lights. Or watch their EV which operated ok for a month go into flames as their infrastructure burns first, regardless of which li-ion chemistry they choose.

Your argument is akin to claiming that most seatbelts are what cause traffic fatalities, based on stories of seatbelts trapping people in their cars, and homemade seatbelts doing more good than harm in accidents.