[chbot] Scrounging for big switch mode PSUs

[Henri Shustak]

Hello,

I have some experience with something like this at a much lower voltage ≈12V. Basically, when you are pulling directly from batteries (which have a changing voltage), the power will come from the battery with the higher voltage. However, what you are talking about is banks of batteries. This is going to add significant complications to the way that all interacts unless you have a nice BMS. I would like to know how you manage as this is something I have messed about with at lower voltages and using chunky(ish) diodes to prevent one battery charging the other.

Thanks.
Henri


> On 8/03/2019, at 11:45 AM, Wes Edwards <edwardsw at steadfast.co.nz> wrote:
> 
> Hi Peter
>  
> Wouldn’t 3 x 1000W @48V units produce either 1kW @ 144V (series) or 3kW @48V (parallel)?  I don’t think you could get 3kW at 114V unless you had 9 units (3 banks in series, with each bank paralleled)?
>  
> In any case, I have serious doubts that you can combine PSUs like that either in series or in parallel –you can’t guarantee that the load would distribute evenly – it is more likely that one unit with very slightly different specs would end up taking more load and fail (possibly spectacularly).  I think PSUs are very unlike batteries in this regard.
>  
> There may be some exceptions with PSUs that are specifically designed to do this, or specialised control electronics to manage the load sharing, but I don’t know of any.
>  
> Wes
>  
> From: Chchrobotics <chchrobotics-bounces at lists.ourshack.com> On Behalf Of Peter Harris
> Sent: Friday, 8 March 2019 10:22 a.m.
> To: chchrobotics at lists.ourshack.com
> Subject: [chbot] Scrounging for big switch mode PSUs
>  
> Hi All
> As part of my domestic grid tied battery system I need an isolated DC power supply capable of producing 2.5kW at between 120V & 300V  The voltage does not need to be adjustable.
>  
> My plan is to purchase 3 x 1000W 48V caged units and series them to yield 3kW @ 144V however I thought I'd see what folks have gathering dust before I place the order. There a many configurations that would do the trick 2 or 3 x 76V or 96V or even a stack of meaty 24V units.
>  
> If you have a suitable combination you would like to dump, sell or swap for beer please let me know.
>  
>   Peter
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