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

[inetdog]

am i aloud to give you the url to the place where i bought them?

I think so, but recognize that your post may not be visible immediately if the software decides that it needs approval by a moderator first.

If you were the person selling them at that URL the answer might be different.

[mike3367]

am i aloud to give you the url to the place where i bought them?

[inetdog]

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

Interesting mechanical arrangement. 4S4P?
What are those black and red blocks?

[mike3367]

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

[inetdog]

If you are charging the batteries at home then I would use a hobby BMS charging system. If the plan is to use solar cells on the craft to keep the batteries charged to extend the "voyage" then it may be harder to find a BMS system that works with solar but it may not matter if all you want to do is just perform some type of trickle charge to get a few more hours of use out of the LiPo or LFP.

I may be wrong, but I get the impression that the OP is looking at long distance unattended travel or station keeping, in which case the system would be sized for multi-day unattended operation, with PV supplying the entire power budget of the craft.
That sort of use actually, IMHO, puts a lot more emphasis on increasing the performance and reliability of the array than increasing the energy density of the battery.
Energy density would be a major factor if the voyage would start with charged batteries and lose net energy with every hour or day of operation.

[SunEagle]

Ok, now that we know what the application really is :

Headway LiFeP04 cells. Provides the cycle life and energy density which is appropriate for a boat already having 400w worth of panels and all that other gear.

Unlike large prismatics that top out at about 3C, the Headways are 10C (burst) capable. As individual cells, you'll need to make your own pack conveniently with the holders. Fortunately large enough to handle without doing something stupid like trying to diy solder tabs onto 18650's. Choose your voltage and capacity and make your own xSxP pack.

For additional assistance see the message forum on the Wheelchairdriver "Everything Wheelchair > Step by Step Lithium Conversion" thread. There is a reason they choose these high-rate LFP's, one of which is that they are inches below their butt, but they have the performance necessary for motor propulsion that typical large prismatics come up short with. And since they sit on top of these things, the packs are built RIGHT, with safety in mind.

Since those guys rely on hobby chargers (like the very nice PL8) to do all the balancing during charge, and not vampire boards, you'll probably want something like this instead:

CleanPowerAuto LLC's own bms, which incorporates HVD, LVD, relay contact points, etc - all the stuff your tech will want when putting together the Headway pack for the target voltage and capacity.

But before you buy, be sure to calculate your power draw over time, and if your 400w panels will be able to recharge between the typical 80% and 10% DOD during your use timeframe and solar insolation hours of the geographical area, which should be done with the WINTER data.

If you are charging the batteries at home then I would use a hobby BMS charging system. If the plan is to use solar cells on the craft to keep the batteries charged to extend the "voyage" then it may be harder to find a BMS system that works with solar but it may not matter if all you want to do is just perform some type of trickle charge to get a few more hours of use out of the LiPo or LFP.

[PNjunction]

Ok, now that we know what the application really is :

Headway LiFeP04 cells. Provides the cycle life and energy density which is appropriate for a boat already having 400w worth of panels and all that other gear.

Unlike large prismatics that top out at about 3C, the Headways are 10C (burst) capable. As individual cells, you'll need to make your own pack conveniently with the holders. Fortunately large enough to handle without doing something stupid like trying to diy solder tabs onto 18650's. Choose your voltage and capacity and make your own xSxP pack.

For additional assistance see the message forum on the Wheelchairdriver "Everything Wheelchair > Step by Step Lithium Conversion" thread. There is a reason they choose these high-rate LFP's, one of which is that they are inches below their butt, but they have the performance necessary for motor propulsion that typical large prismatics come up short with. And since they sit on top of these things, the packs are built RIGHT, with safety in mind.

Since those guys rely on hobby chargers (like the very nice PL8) to do all the balancing during charge, and not vampire boards, you'll probably want something like this instead:

CleanPowerAuto LLC's own bms, which incorporates HVD, LVD, relay contact points, etc - all the stuff your tech will want when putting together the Headway pack for the target voltage and capacity.

But before you buy, be sure to calculate your power draw over time, and if your 400w panels will be able to recharge between the typical 80% and 10% DOD during your use timeframe and solar insolation hours of the geographical area, which should be done with the WINTER data.

[Sunking]

But if his project is a surface RC then LiPo would be my first choice depending on the distance and course being traveled. There are a lot of 4S flying RC that can go multiple km and get back using the RTH technology as well as a programmed flight pattern. Why not one using a nautical GPS program. It would be interesting to hear about the outcome of his experiment.

OK I must be missing something. As you know I am a RC pilot with around 100 LiPo packs lying around in a fridge. LiPo's are used for 1 primary reason, they can deliver extremely high Continious Discharge Rates up to 50C or 1 minute. That is one reason they are so popular with E-Bikers and EV Drag Racers. LiPo' have 3 significant disadvantages: Very high $/Wh, Very Unstable requiring Fire Proof Charge Bags to contain them, and short cycle life. If his project demands such high performance and has the budget OK.

If not then LiFeP04 would be a batter choice, perform better for his application, and a whole lot less expensive. As an RC Pilot I am sure you are aware the larger E-Planes use a separate battery from the LiPo Traction Battery. They use a small 2S LFP like 1500 mah for the RX and Servos. They do that because LFP is more reliable and gives them the ability to do a Dead Stick Landing if they do not get the plane down before exhausting the Traction Battery.

Or he could use the LiPo now that he knows why you would chose one over the other. Bottom line is chose the best technology for the specific application. No such thing as Best Battery Type for any application. Sounds to me like that is the trap the OP fell into with Lithium.

Anyway to OP we as consumers in reality only have access to 3 basic types of Lithium Batteries and a rare forth kind. The really good ones we cannot buy. Your choices are LFP, LCO, and LiPo. Ironically LiPo is not a Polymer Battery, it is a LCO hybrid on steroids using an organic Gel Electrolyte which makes them unstable and HOT. Each has a different application and operating voltage. LFP = 3.2 volts, LCO = 3.6 volts, and LiPo = 3.7 volts. LFP is the safest and longest lasting of the 3 that works up to at least 1C charge discharge rates.

There is a 4th and you can buy them in 18650 form factor called Lithium Titinate (LTO). They are used in 1 EV. On paper the longest lasting battery of 10,000 cycles but never has been documented or tested. There claim to fame is like LiPo with extremely high charge and discharge rates coupled with the safety of LFP. They have two huge disadvantages Extremely expensive ($4/wh), and a Energy Density that of a Lead Acid with a LTO voltage of 2.4 volts meaning WH to WH weigh about the same 50Wh/Kg. LTO = 2.4 volts

Lastly go read this quick White Paper on Lithium Batteries. There is more than one type. Hopefully you will pick up that the higher the cell voltage, the greater the energy density. So from the 4 I spoke of highest to lowest energy density is LiPo, LCO, LFP, LTO a range from 250Wh/Kg to 50Wh/Kg. Lastly the most important thing if you intend to use Solar as the charge source means you need to use a Lithium cell compatible with Lead Acid battery voltages. That leaves you one choice, LFP

[SunEagle]

Look forget LiPo an extremely unstable battery with a very short cycle life of 200 to 300 cycles.

You can certainly use lithium battery for your project. It does not require any BMS, just a good strategy like NASA uses. NASA uses Lithium Batteries in all satelites and NO BMS. They cannot afford the the weight or space. Use 4S LFP cells, perform an initial Bottom Balance, and set the charger voltage to 13.6 to 14.0 volts and you are good to go.

If you insist on a BMS, then buy a 12 volt LFP battery with built-in BMS. All they require is a 14.4 volt source which means set your charge controller to 14.4 volts and call it done. Personally I would set the voltage to 14 volts so the BMS is never used which gives you twice the cycle life.

But if his project is a surface RC then LiPo would be my first choice depending on the distance and course being traveled. There are a lot of 4S flying RC that can go multiple km and get back using the RTH technology as well as a programmed flight pattern. Why not one using a nautical GPS program. It would be interesting to hear about the outcome of his experiment.

[Sunking]

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.

Look forget LiPo an extremely unstable battery with a very short cycle life of 200 to 300 cycles.

You can certainly use lithium battery for your project. It does not require any BMS, just a good strategy like NASA uses. NASA uses Lithium Batteries in all satelites and NO BMS. They cannot afford the the weight or space. Use 4S LFP cells, perform an initial Bottom Balance, and set the charger voltage to 13.6 to 14.0 volts and you are good to go.

If you insist on a BMS, then buy a 12 volt LFP battery with built-in BMS. All they require is a 14.4 volt source which means set your charge controller to 14.4 volts and call it done. Personally I would set the voltage to 14 volts so the BMS is never used which gives you twice the cycle life.

[Sunking]

Indeed it does. And yet EV manufacturers, renewable energy manufacturers and battery manufacturers use balancing circuits -

True but rarely if ever used. No EV manufacture allows their customers to fully charge the EV battery. they only allow you to use 60 to 80% of the capacity.

Tesla uses the the same TI chip most BMS manfacture uses. All work on the exact same principle. Fact is once a Lithium battery pack is balanced rarely ever needs to be rebalanced. Additionally the last thing any user wants to do is fully charge their battery packs as that is extremely FOOLISH, thus why EV manufactures do not allow it to happen. In order to Top Balance you must fully charge the battery. Do that and you cut cycle life in half.

Lastly BMS are usefull in say a 32S and up packs where 3 volt swing is normal. However on a 4S, battery even 1 volt off is going to get your attention real fast Set the LVD to 12 volts, an initial Balance, and charge to 13.6 volts. No BMS is required or ever needed.

[Sunking]

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

Well budder my butt and call it a biscuit. Now tell that idiot Karrak.

[Sunking]

Indeed it is - as is true with any battery (or solar) technology. Hopefully forums like this one help people make better decisions on such issues.

How is that working? Everyday fools come here that have already bought equipment and want to know why it is not working.

[Sunking]

[QUOTE=drpatso;n336341]Appreciate all the input guys. Manual balance is not in the question for me, and I'd like to get better density than LiFePO4. I have been amazed at the lack of options for batteries other than lead and gel./QUOTE]

Purely market driven and simple economics. A FLA battery is 1/4 the cost and last twice as long than any lithium battery. Why would any fool buy lithium for a solar application when there are better and less expensive options.

An EV can justify the expense, but not solar. That is why you are not finding a lot out there, There is no MARKET for it.

Which gas station would you use and which one stays in biz. The station on the Corner that sells gas for $2/gal, or the one across the street that sells gas for $10/gal. It is that simple. Only a fool would pay $10/gal.

[drpatso]

I think motor will be the last thing we decide on when we have a better idea of the weight and hull. Definitely won't have variable pitch, likely a brushless for efficiency and they typically have a very wide throttle range, we'll control it with PWM or a DAC if it's a simpler motor controller. We will be monitoring the pack voltage and GPS clock for the throttle setting. Battery must be topped off before sundown and we'll try and design it to run on 3-4amps all night and of course shutting the motor off if the voltage gets too low.

I will hopefully be getting one of the 100W panels the boat will have and a charge controller shortly after christmas and try and do some prototyping on the battery.