DIY Intelligent LiPo charger for 48v nominal packs

[joss]

I've been searching around both here on Endless Sphere and generally on the internet to find a home made/DIY configurable charger suitable for a 48v 13S/14S Lipo pack. I'm interested in purchasing the Grin Satiator but at the price its a bit out of reach and I don't really require it to be rugged or small as it would be located at home all the time.

Can anyone point me to some resources where someone has done this before? There seem to be some cool integrated circuits on the market which manage the charging algorithms in an all-in one package - perhaps integrated with a microprocessor/Arduino controller! I'd like to be able to charge my battery to different SOC set-points to lengthen the life etc.

Any help appreciated

 

[whereswally606]

there are some lipo chargers which you can determine max voltage upto 4.2v from about 1. something and amps up to 8amp but the greatest cell string is 9s.

un-a9+ or bcm168 (6s)

bad news they aren't that cheap circa £90 / £60 and you need a decent 12v-14v supply to power them.

good news for a 13s / 14s you could do this with

1 of each or 3 bcm168 chargers but to connect you will need to break the pack into 2 or 3 subpacks respectively. but it is a solution.

 

[ElectricGod]

another option is a PC power supply and some DC-DC up converters like this. I bought the up converters on ebay for like $6 each and another dollar for the terminal strip. The watt meter was like $12. I reused a PC power supply I had laying around. Use the highest wattage power supply you can scrounge or more specifically the 12 volt line. I terminated all the power supply wires to my terminal strip, but you probably don't need anything other than ground, +12 volts and the ATX power on wire.

This is my thread where I did this build. Most of the way down page one is where I show the power supply build. With Adjustable DC to DC converters, you can set your output voltage to whatever you want. I'm currently building a better one on a larger power supply and using four converters that go up to 96 volts.
https://endless-sphere.com/forums/viewtopic.php?f=35&t=75177

 

[joss]

Thanks for the replies. I'd be ok to use this sort of solution on my home made pack made from old laptop cells but I have recently purchased a bunch of brand new 3400ma cells and I need to follow the charging 'rules' with the battery pack I'm going to make (14s8p). As such it needs to follow the constant current/constant voltage 3 or 4 step process. I'm aware of the availability of cheap cc/cv dc/dc converters and indeed have bought some however they have potentiometers for set-up so re-configuring them quickly is a non starter. Most of these boost converters are good to 35V but you can get some higher voltage versions

For example...

http://www.aliexpress.com/item/DC-1...48&btsid=615b017b-2d1b-46fa-9147-050754769c1d

Note: I have not purchased or tested this unit I just reference it here as an example.

I guess t this sort of cost you could set up more than 1 unit ie one set to 58..8V (100%) and another or multiple ones at, say 57V, to achieve a lower SOC. Alternatively I guess you could have 1 unit then use an Arduino to switch in fixed resistor values (in place of the potentiometers on the power supply) to achieve the same result?

Perhaps I am answering my own question!!

 

[999zip999]

What 3400mah cells ? 27ah pack.

 

[joss]

What 3400mah cells ? 27ah pack.

LGDBMJ11865

https://www.fasttech.com/products/0/10004182/2762803-authentic-lg-18650mj1-3-6v-3500mah-rechargeable

The webpage says 3500mA but the data sheet says 3400mA minimum. I have 104 to make up into a (hopefully) a nice pack (13S or 14S) for my Bafang 750W motor. My intention is to rarely charge to 100% and normally only to ~80%. Similarly not allowing deep discharges if I can help it, thus doubling/tripling the battery pack life.

 

[ElectricGod]

Thanks for the replies. I'd be ok to use this sort of solution on my home made pack made from old laptop cells but I have recently purchased a bunch of brand new 3400ma cells and I need to follow the charging 'rules' with the battery pack I'm going to make (14s8p). As such it needs to follow the constant current/constant voltage 3 or 4 step process. I'm aware of the availability of cheap cc/cv dc/dc converters and indeed have bought some however they have potentiometers for set-up so re-configuring them quickly is a non starter. Most of these boost converters are good to 35V but you can get some higher voltage versions

For example...

http://www.aliexpress.com/item/DC-1...48&btsid=615b017b-2d1b-46fa-9147-050754769c1d

Note: I have not purchased or tested this unit I just reference it here as an example.

I guess t this sort of cost you could set up more than 1 unit ie one set to 58..8V (100%) and another or multiple ones at, say 57V, to achieve a lower SOC. Alternatively I guess you could have 1 unit then use an Arduino to switch in fixed resistor values (in place of the potentiometers on the power supply) to achieve the same result?

Perhaps I am answering my own question!!

These DC to DC converters work. They are good for 90+ volts. Keeping your cells balanced can be an offline task. I use a single 20S BMS that plugs into each of my packs for balancing when I want to balance charge. All the rest of the time I use the power supply set to the voltage that I want to charge the total pack. It is a good idea to use your pack at less than the maximum capacity so you get more life out of it. With an adjustable charger, just set it's output voltage to the voltage you want. So 80% of a 4.1v cell times the number of cells in the series gets you your power supply voltage.

 

[ElectricGod]

What 3400mah cells ? 27ah pack.

LGDBMJ11865

https://www.fasttech.com/products/0/10004182/2762803-authentic-lg-18650mj1-3-6v-3500mah-rechargeable

The webpage says 3500mA but the data sheet says 3400mA minimum. I have 104 to make up into a (hopefully) a nice pack (13S or 14S) for my Bafang 750W motor. My intention is to rarely charge to 100% and normally only to ~80%. Similarly not allowing deep discharges if I can help it, thus doubling/tripling the battery pack life.

Geez $6 a cell is UBER expensive. Look for them on alibaba. You should be able to get them for around $5 each.

 

[joss]

Geez $6 a cell is UBER expensive. Look for them on alibaba. You should be able to get them for around $5 each.

1off (pack of 4) = 24.02 3 to 4 = 23.17 5+ = 22.86. underneath this there is a link "looking for more?" Fasttech will quote a reduced rate for more quantities. I got 21.05 or 5.25 each, this included delivery which was airmail. I received the batteries in about a week (Australia). I'm ok with that. Fasttech are not the rock bottom price but I find them pretty reliable and as such they are 'all round' competitive. However, the nosedive that the Aussie $ has taken in the last year makes any few cents saved here is subsumed by the exchange rate movements.

Now we are off topic.....the question is has anybody made any home made/DIY/intelligent chargers!