Building a charger for 100V battery pack

[peters]

I need to design and build one to charge my 29s Lifepo4 pack.
In fact it must be a switched-mode power supply (inverter) with regulated 106V output voltage and around 10A limited current (but variable voltage and current is a nice to have). My cell balancer is in the BMS, so only one high voltage output is needed.
It should be small and light, portable (max. 1kg including box...?) and high efficiency (without a fan if possible).
The mains input is 230VAC. The output must be isolated, but I don't have experience in designing with HF power transformers yet.
Has someone already made a similar charger? Maybe schematics of a similar inverter, or any idea where to start? (operating frequency, transformer sizing, control circuit, etc.)

Thanks,
Peter

 

[circuit]

Hi Peter,

Take two 48V chargers and connect them in series. Adjust voltage as needed.

 

[dnmun]

or you can just buy the EMC-1000 and have them set it to 106V for you.

 

[peters]

Thanks for the ideas, but I prefer fabricating my own charger anyway.

 

[dnmun]

you gotta be kidding.

 

[heathyoung]

I'm doing a 150V @ 10A one at the moment (just need to post up some pics + schematics).

It isn't a trivial exercise, and there is some hefty maths behind the design, but it is doable, depending on your background (I was an EE) you may be able to make one. I expect to send some silicon to hell doing it (at $15 per device, this gets annoying)

I decided to use an unisolated buck topology, simply due to the prices of getting custom magnetics wound here was way too expensive. It does have the downside that the output is referenced to 1/2 rectified mains supply (output is not isolated, and is dangerous).

There is an electronics magazine here in Aus that documented how to convert a PC power supply to a valve plate supply (~180V) - it gives you a good idea of the things to keep in mind when rewinding etc.

What are your abilities? Making your own charger is only worthwhile (cost wise) when you pass the >1.2-1.5Kw mark.

 

[dnmun]

i was able to find the big IGBTs for $4 each. plus $4 shipping and then $.10 for each one after that. they are $13 from mouser before shipping.

 

[peters]

Not kidding, I'm interested in this. But I don't want to waste too much time.
I'm also an EE, and thinking of a forward or flyback converter, but I need to dig more into the details. For sure I'll have to wind my transformer, and there are a lot of controller IC-s from Texas Instruments and others that are suitable in these topologies.

 

[dnmun]

why not fix the chargers all these people wanna send me if you wanna waste a lotta time? maybe you will learn how to build a charger by fixing them. i certainly realized i would never waste my time reinventing the wheel if someone else can make a living building it for me for 1/10 the cost of parts to me.

 

[peters]

No, it's not about reinventing something, but I like to make things in the way that best suits my needs.
For example I prefer a dust- and waterproof charger, and with a fan inside it cannot be like that. Even more, if it is light and small, then it could be integrated inside the battery box, so only a power cord is needed to charge anywhere.
Or another example is the serial communication of my BMS, controller and display: they are connected together on an optically isolated bus, so the display will show the voltage of each individual cell without reconnecting any cable - you cannot do it with off-the-shelf components.

 

[Kingfish]

No, it's not about reinventing something, but I like to make things in the way that best suits my needs.
For example I prefer a dust- and waterproof charger, and with a fan inside it cannot be like that. Even more, if it is light and small, then it could be integrated inside the battery box, so only a power cord is needed to charge anywhere.
Or another example is the serial communication of my BMS, controller and display: they are connected together on an optically isolated bus, so the display will show the voltage of each individual cell without reconnecting any cable - you cannot do it with off-the-shelf components.

Have you mined Meanwell.com? They have all sorts of options and ideas that are IMO well above average. Creating a sealed charger is just a matter of re-casing of course. You could even use the same thermal sense circuit to trigger an external cooling pump.

For myself, I have been thinking how I'd like mine to be for the road - which is presently cumbersome cos I have to drag out the whole shebang. Better if all I had to do was roll out the extension cord and plug it in. Alas - I am at that voltage where I need two units in series to make a go of it, which is two kgs I'd like to loose. But I'm not quite bought off on the idea of making my own with so much potential is sitting there off the shelf. :wink:

Dennis, did you finish your charging station, and if so - what are your outlets & capacities?
Your first customer, KF