MPPT or PWM charger? For LiFePO4 battery?

[jumpjack]

Hi all,
I have a 60V/24Ah li-ion battery 16S/6P coming from my e-scooter. It can't anymore provide enough current for the scooter (25-50A), but it can easily provide 4-5 A I need to turn on my fluorescent lights (100 W in total at 230V).
I also have two 240 Wp solar panels, which currently charge two 12V/65Ah Pb-gel batteries using a "standard" charge regulator.

How could I "move" my system to lithium so I can count on 1440 Wh rather than 780 Wh?

I read somw of you use lead chargers with lithium battery "equipped with balancer and BMS" and whatelse.
Does it exist a ready-made solar-lithium charge regulator for 60V batteries?
Or, which is the alternative?

[inetdog]

Hi all,
I have a 60V/24Ah li-ion battery 16S/6P coming from my e-scooter. It can't anymore provide enough current for the scooter (25-50A), but it can easily provide 4-5 A I need to turn on my fluorescent lights (100 W in total at 230V).
I also have two 240 Wp solar panels, which currently charge two 12V/65Ah Pb-gel batteries using a "standard" charge regulator.

How could I "move" my system to lithium so I can count on 1440 Wh rather than 780 Wh?

I read somw of you use lead chargers with lithium battery "equipped with balancer and BMS" and whatelse.
Does it exist a ready-made solar-lithium charge regulator for 60V batteries?
Or, which is the alternative?

Hi and welcome to the Forum!

Not very many solar charge controllers come with support for that high a battery voltage. 48 volts is the usual high end. But some do support 60.
If the connection between the battery and the rest of the scooter, including the charger, is only two wires, + and -, then the battery management system, or enough of it for the scooter use case, will be integrated into the battery. The only things that the external charger will have to do is control the voltage and current to the profile needed for that battery.
Without charging information from the battery manufacturer or the scooter manufacturer, it is hard to know what those setting should be.

If the battery is connected by more than just two wires, then it is likely that the charging circuit has to receive and act on information (signals) sent back to it from the battery. This could include an end of charge alert, battery temperature, and a host of other things which a controller not designed for that battery will not be able to process properly.

The other side of the problem will be to find an inverter which can handle 60 volts input to give you 120 or 240 volts out. They exist, but they tend to be either large and expensive or hard to find and expensive.

[Sunking]

Hi all,I have a 60V/24Ah li-ion battery 16S/6P coming from my e-scooter.

So why are you HJ an old thread?

[T1 Terry]

I would first check the voltages of all the Li cells at the end of charge. there is a very big chance the BMS has failed to properly balance the cells and some of the cells are just flat. Charge each cell seperately to 3.6v till no more amps flow into that cell, then try the scooter again. If it still doesn't work properly check all the cell voltages, when the scooter seems sluggish before recharging, number each cell and post what the voltages are and I will see if I can help you build a hose battery from the old cells that are still any good.

T1 Terry

[rreinha]

Hi all,
I have a 60V/24Ah li-ion battery 16S/6P coming from my e-scooter. It can't anymore provide enough current for the scooter (25-50A), but it can easily provide 4-5 A I need to turn on my fluorescent lights (100 W in total at 230V).
I also have two 240 Wp solar panels, which currently charge two 12V/65Ah Pb-gel batteries using a "standard" charge regulator.

How could I "move" my system to lithium so I can count on 1440 Wh rather than 780 Wh?

I read somw of you use lead chargers with lithium battery "equipped with balancer and BMS" and whatelse.
Does it exist a ready-made solar-lithium charge regulator for 60V batteries?
Or, which is the alternative?

This pack in a brand new state was only 1200Wh, the 60V label is at full Charge (3.75/cell) and not the nominal of 51V. New it should have produced 2200W for 45 minutes, until 44V.
I suspect the BMS is very limited on what it does and I agree with Ti Terry, that you may have a few 0V cells, sometimes you can re-charge them (IF THERE ARE LFP) and have no huge negative effect. BUT If they have any Cobalt in them DON'T try to charge them (BANG!).
Do you know the scooter maker name?

[Beanyboy57]

Link to advertisement

Hi Williams,

I'm also looking for a charger solution or provider. Would you please share with me once you get any update? I'll do the same for sure.

Since I'm designing a standalone solar generator for disaster recovery, I am keen to integrate LiFePO4 into my system in order to replace the Lead acid type.

with kind regards
Thomas

Unsure if I should be posting this link, but there are manufacturers supplying LiFe batteries with BMS, I wonder if anyone has any experience with batteries from this supplier, good or bad.

[T1 Terry]

Unsure if I should be posting this link, but there are manufacturers supplying LiFe batteries with BMS, I wonder if anyone has any experience with batteries from this supplier, good or bad.

These 2 lines from the PDF tell me they either haven't got a clue or they are scare mongers Why a Battery Management System (BMS) is needed:
1. A LFP cell will be destroyed immediately if the voltage over the cell falls to less than 2,5V.
2. A LFP cell will be destroyed immediately if the voltage over the cell increases to more than 4,2V.


This of course pure and utter nonsense so I stopped reading at about that point. It's a pity because Victron have a great reputation for selling quality equipment so I don't undrstand why they would be putting such nonsense forward trying to pass it off as fact. Simple too much of this nonsense out there, all from BMS sellers.

T1 Terry

[T1 Terry]

This pack in a brand new state was only 1200Wh, the 60V label is at full Charge (3.75/cell) and not the nominal of 51V. New it should have produced 2200W for 45 minutes, until 44V.
I suspect the BMS is very limited on what it does and I agree with Ti Terry, that you may have a few 0V cells, sometimes you can re-charge them (IF THERE ARE LFP) and have no huge negative effect. BUT If they have any Cobalt in them DON'T try to charge them (BANG!).
Do you know the scooter maker name?

Well spotted up, the 3.75v per cell is also the nom. voltage for lithium polymer cells. I sure wouldn't mess with these things, they are a fireball waiting to happen so be very aware of what you are doing if you want to recharge these cells individually. The model aircraft enthusiasts use these cells but they also use Kevlar sacks to charge them in and never travel with them fully charged, these type of lithium batteries can burst into flame at the drop of a hat.
I would strongly advise against building lithium polymer house battery pack unless you are right at the top of your game and can build a suitable charge and discharge system complete with a fire containment system.

T1 Terry

[rreinha]

Terry if you had read all my post you would have seen I put on each cell a 3.9v zenner and a 10 ohm resistor to make sure no cell goes above that voltage and use a low voltage cut off switch set to 10v..This is more important as the cell voltage drops very quick below 2.8v and if a cell drops to below 2.2v it will die a sad death.Im only using 10ahr cells so 1w zenners are more than adequateas voltage levellers.. Make sure your charger cant do an :equalizing" charge.

I have found when you ask the people that are always saying how wonderful MPPT chargers are ,if they have done a direct comparison between a MPPT and a PWM on their panels and batteries and what were the differences,The answer is NO but they "know" they are better.

John
You will get better life out of those cells if you cut the voltage at 3.75v per cell. They can take 3.9, but that is extra work on them with no benefit
Also you diffidently want to get them above 3.4 as this is the near the top of the curve, but does not insure a full charge.

[choyak]

Terry if you had read all my post you would have seen I put on each cell a 3.9v zenner and a 10 ohm resistor to make sure no cell goes above that voltage and use a low voltage cut off switch set to 10v..This is more important as the cell voltage drops very quick below 2.8v and if a cell drops to below 2.2v it will die a sad death.Im only using 10ahr cells so 1w zenners are more than adequateas voltage levellers.. Make sure your charger cant do an :equalizing" charge.

I have found when you ask the people that are always saying how wonderful MPPT chargers are ,if they have done a direct comparison between a MPPT and a PWM on their panels and batteries and what were the differences,The answer is NO but they "know" they are better.

I have done a comparison between the old PWM and new MPPT and my opinion is that the MPPT is significantly better. THe old PWM gave me a maximum of 30 amps charge, the new MPPT I observed 36 amps a few times! This is with LiFePO4.

[choyak]

Hi Williams,

I'm also looking for a charger solution or provider. Would you please share with me once you get any update? I'll do the same for sure.

Since I'm designing a standalone solar generator for disaster recovery, I am keen to integrate LiFePO4 into my system in order to replace the Lead acid type.

with kind regards
Thomas

I am here with 180AH 24V LiFePo4 with the solar charger that it seems that I got it functioning well. The Solar Charger is the same as AIMS SCC40MPPT, and I had an old PWM charger, and the MPPT is significantly better. The AIMS and the one I have brand MPP Solar are the same.....I got it on ebay and it is great there are two relays you can configure. What I did was configure to switch off (return to utility) when battery goes below 24.3. I have the facebook group 'solarages' that displays what I did!!!

[choyak]

Terry if you had read all my post you would have seen I put on each cell a 3.9v zenner and a 10 ohm resistor to make sure no cell goes above that voltage and use a low voltage cut off switch set to 10v..This is more important as the cell voltage drops very quick below 2.8v and if a cell drops to below 2.2v it will die a sad death.Im only using 10ahr cells so 1w zenners are more than adequateas voltage levellers.. Make sure your charger cant do an :equalizing" charge.

I have found when you ask the people that are always saying how wonderful MPPT chargers are ,if they have done a direct comparison between a MPPT and a PWM on their panels and batteries and what were the differences,The answer is NO but they "know" they are better.

Since I actually did the comparison between my old PWM and new MPPT charger, I will confirn that the MPPT charger is better, and I am using LiFePO4. On my charger, I set 'float' and 'equalize' to the same value.

[choyak]

These 2 lines from the PDF tell me they either haven't got a clue or they are scare mongers Why a Battery Management System (BMS) is needed:
1. A LFP cell will be destroyed immediately if the voltage over the cell falls to less than 2,5V.
2. A LFP cell will be destroyed immediately if the voltage over the cell increases to more than 4,2V.


This of course pure and utter nonsense so I stopped reading at about that point. It's a pity because Victron have a great reputation for selling quality equipment so I don't undrstand why they would be putting such nonsense forward trying to pass it off as fact. Simple too much of this nonsense out there, all from BMS sellers.

T1 Terry

My LiFePo4 cells DID get to the horrid voltage of 2.1/cell once with NO noticeable degredation in performance.....so that scaremonger PDF is a LIE!!!!! I have NO BMS, and after about 9 months, my Celllog shows maximum delta V is EIGHT POINT THREE millivolts. I sort of lied, I have a SIMPLE BMS that has opamp and switch on balance resistor if voltage rises past 3.65 (I think) but LiFePo4 will not become 'immediately destroyed' if voltage decreases less than 2.5.. I think if the voltage goes below 2.0, you will suffer a degradation in performance, though.

[T1 Terry]

MPPT or PWM charger? For LiFePO4 battery? interesting

Very interesting findings. Does the MPPT regulator return to boost mode or have you set the float high to compensate? Have actually measured the amps in with an independant meter, or are you trusting the meter that came with the controller? The reason I ask that is, I had 2 BZ MPPT controllers that gave outstanding improvements over the PWM controller, till I independantly tested the readings, the two MPPT controllers read high by a consistant 20%, the actual output was less then the PWM controller. the only time I saw an advantage was were there was a major panel MPP mismatch, 32v MPP charging a 13v battery, MPPT was always gong to win with that type of arrangement, but all the panels with an advertised 16.5v to 18.5v MPP performed better with a PWM controller than any of the MPPT controllers I tested, the GSL 60 amp unit included.

T1 Terry

[choyak]

The MPPT will never boost since I have the panels in 'serallel' So I routinely get over 70 volts into the MPPT, with a battery of 24 volts. I actually measured the amps with a DC ammeter you squeeze onto the wire like amp clamp. The MPPT controller amp reading is pretty accurate. I also have an LED meter with a 50ma 100amp shunt that displays the reading, positive when charging, and negative when discharging.

Charging:
photo(5).JPG

Discharging:
photo(4).JPG