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Solar controller who can charge lithium ?
#1
Big Grin 
Hello, here is my 2nd thread.

I ve done about 0.5-0.6KWH  of 4S5P and 4S10P battery ( 4 battery ) from laptop cells with bms, all is working great

Now i m installing all the 12V outdoor lights ( LED ) and i can't continue because i m afraid of something.....


My lights and battery are okay, but i ve 2 unused solar panels that i don't use (too much for my roof ) it produce in a range of 30-37V DC ( using/not using voltage )   at a max of 7.5A.

I have a solar regulator who give me 24DC 20A,  and my battery are 14.4V  ( 16.8V in charge if i don't make mistakes ).

My question is :   is that dangerous to use a DC-DC voltage adjuster to down the voltage at 16.8V and use it to charge the battery's ? 
I mean : is it not a problem to let the BMS cut the battery when overcharged ? 

also it bring me to another question, does it exist on ebay/aliexpress or something like that ( because i am in france, not US ) a solar regulator who can stop when batterys are full ( special for lithium ) i m afraid that the BMS deffect and makes batterys burn ! ! ! ( it is outside but if it don't burn i prefer :Smile
or does it exist a small chinese pcb who can accept 24VDC and charge my batterys at 16.8v and stop ?

any advices are great Smile
Sorry for my english, i m french and english is not my best part at school  Smile
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#2
Look for a "solar charge controller" - there are lots of then on ebay & aliexpress.
If you want a better quality one, then look at Victron eg:
https://www.victronenergy.com/solar-charge-controllers
Running off solar, DIY & electronics fan :-)
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#3
(01-21-2019, 10:26 PM)Redpacket Wrote: Look for a "solar charge controller" - there are lots of then on ebay & aliexpress.
If you want a better quality one, then look at Victron eg:
https://www.victronenergy.com/solar-charge-controllers

hello redpacket, but like i ve said i already have a controller charge, but it is a 24v controller charge, i don't really find a controller charge at 16,8V.

Do you think this can make the job if i set a charge voltage between 16-16.5v ? ( hope it is not a problem to send link on the forum)


https://www.banggood.com/fr/10A-DC-DC-LC...rehouse=CN
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#4
(01-21-2019, 11:39 PM)vivi0512 Wrote:
(01-21-2019, 10:26 PM)Redpacket Wrote: Look for a "solar charge controller" - there are lots of then on ebay & aliexpress.
If you want a better quality one, then look at Victron eg:
https://www.victronenergy.com/solar-charge-controllers

hello redpacket, but like i ve said i already have a controller charge, but it is a 24v controller charge, i don't really find a controller charge at 16,8V.

Do you think this can make the job if i set a charge voltage between 16-16.5v ? ( hope it is not a problem to send link on the forum)


https://www.banggood.com/fr/10A-DC-DC-LC...rehouse=CN

Links on this forum are OK, as far as I know :-)

The unit in your link is not the best way, sorry.
A proper solar controller (an MPPT one) will take in a higher voltage & convert it to the lower voltage (with good efficiency). 
Power supply devices like in the link are not designed to work the same way as a solar charger and probably will not work well.

If you look at specs for a typical MPPT unit (even a PWM type one), you need one that does  adjustment for the battery voltage settings.

If you look at this manual:
https://www.victronenergy.com/upload/doc...-ES-SE.pdf
you can adjust the battery voltages

Maybe search ebay for "solar charge controller lithium"
maybe this for a cheaper one:
https://www.ebay.com.au/itm/MPPT-Solar-C...2947929651
vivi0512 likes this post
Running off solar, DIY & electronics fan :-)
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#5
the victron is top of the top, but you know my goal is to have free outdoor lights with 1 or 2 of my panels i already have.

It is like an eco(nomic)logic act, and the victron is almost 100€ so it will take years to rentabilise it ...... but i follow your advice and write keywords :  "mppt ajustable lithium"

And i found this one : https://www.ebay.fr/itm/312328990721    ( i also saw youtube video about this product ) seems well,  but adjustable output voltage range is higher than my battery..... it cost only 30€  ( 3x less the victron price ). and it will make my project succeed ..... in one condition.....

  • Repack all my batterys to make higer voltage battery ( rebuy BMS etc... and a lot of time )

    OR

  • Put 3 battery's in series

Last question and i stop bothering you  Smile 

Is that possible to use 3 of my 4S5P  (14.4V nominal)  in series ? i don't see why it can't work but just in case..... like my 3 batterys were a unique battery of 3x14.4 = 43.2V  

this way i can set mannualy the voltage of the battery with this product.
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#6
[quote pid='44132' dateline='1548158292']
vivi0512-
I've just have gone through this whole process myself with some packs of 4s5p 18650 batteries. What you need is a controller that has customizable settings (User defined). Most controllers that are listed for Lithium batteries are referring to LiFe PO4 batteries which run at a lower voltage than Lithium-Ion that I am using. You will need the ability to turn off both float and equalization charging.  If you study it a normal Li-Ion 18650 4s5p pack will charge up to a little over 16 volts and discharge down to about 12 volts. Most 12 volt Invertors will not accept voltage over 16 volts, so good to keep batteries below that, plus it lengthens their life.. Do not let your batteries get below 12 volts or their life will be shortened also. There is a new PWM 20A controller that has a li-Ion setting from Renogy Called the Renogy Voyager
Good Luck
[/quote]
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#7
Yes but doing that i preserve the battery but i lost 30-40% of capacity, because pack is ready to go to 16.8V and i will lose a big part of the charge....

I ve bought this one : mpt-7210a from ebay. for 31€ only this way i will be able to control all parameters.... just need to have an high voltage so :

I will put 3x 4s5p in series and i will let you know how does it work Smile i will receive it in 2 weeks ( chinese order so a litlle long but free).
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#8
Unfortunately the MPT-7210 is a step-up unit only, as it is designed to boost the voltage from a single low voltage panel source to a higher voltage battery pack.

You could always use something like this.
https://www.ebay.co.uk/itm/DC-DC-Convert...2999966553

There are three adjustable resistors
1. Low voltage cut-off (set this to the MPPT voltage around 29V)
2. Current limit (set to max/high)
3. Output voltage (set to 16.8V)

I did not think that these type of units worked well as step-down units but I have used one (30A version) to step down a 50V power supply to 47V low at 20A to charge a pack.
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#9
If you want to go the diy route: https://circuitmaker.com/Projects/Detail...-with-MPPT
you can request the lt8490 ic for sample for free from analog devices.
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#10
also it bring me to another question, does it exist on ebay/aliexpress or something like that ( because i am in france, not US ) a solar regulator who can stop when batterys are full ( special for lithium ) i m afraid that the BMS deffect and makes batterys burn ! ! ! ( it is outside but if it don't burn i prefer : 

On my solar system I use an overvoltage relay to disconnect the solar panel at a certain voltage. This is like a deadman switch, if the controller fails or the bms fails, the relay will stop the charging. Its cheap insurance the overvoltage relay cost less then 6 dollars, the 30 amp automotive relay is like 4 dollars. In the picture is the diagram how to set it up, I wouldn't run my solar system without the overvoltage relay.

For the batteries to overcharge, the bms has to fail and the overvoltage relay have to fail, both at the same time ,would be a rare event.

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