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Forum Index : Electronics : alternative battery charging

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Murphy's friend

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Joined: 04/10/2019
Location: Australia
Posts: 576
Posted: 09:21am 13 Jul 2022
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When off grid its always good to have an alternative way to keep the battery bank full when the sun goes hiding behind rainclouds.
Fortunately that happens rarely here in Perth and I get by with 3 days battery bank endurance for my normal power usage.

But I have a portable generator and it would be nice to turn this into a powerful battery charger. As it is, there is only a 8 Amps @ 12V charger built in, useless for me.

What I needed was to transform the 1.8KW 240V AC output to a suitable lower voltage which, when rectified, is acceptable to my spare 60A MPPT controller.

Having already a 2KW wound toroidal transformer from an early inverter project sitting neglected on a shelf I realised I had most of the parts required for this project on hand.

The biggest challenge with such a project is to find a suitable enclosure for it, one that does not cost an arm and a leg.
It needed to be compact to be portable but also robust enough for the quite heavy transformer.
I decided to make my own, a plywood and aluminium composite as shown on the following pictures.
















And this is the finished charger:




So, does it work? Much to my surprise, yes. I was worried the rather high ripple current I saw when I loaded the rectified secondary up might upset the MPPT input.

Apparently not so. I was running the generator to charge my spare 48V battery bank via this charger. With 1KW charging power I saw around 7V ripple at the input to the MPPT. I will test this again to the full generator output on the next rainy day, when I'll try to charge the house battery bank with a big load on it.

The nice thing with this MPPT is its auto battery voltage adjusting, so it can charge 12V, 24V & 48V batteries without having to switch anything.
Nice for my caravan battery too, it has a 24V lithium battery.
 
Revlac

Guru

Joined: 31/12/2016
Location: Australia
Posts: 960
Posted: 12:26am 14 Jul 2022
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That is Excellent Murph,  I agree its not often you need a charger off grid but its great to have one when the weather has gone bad.
Cheers Aaron
Off The Grid
 
BenandAmber
Guru

Joined: 16/02/2019
Location: United States
Posts: 961
Posted: 06:15am 27 Jul 2022
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wow very nice no suprize there                                                                i need to build one for a friend                                                               he will not have money for a extra mppt                                                        is there a save way to hook it into his mppt
with his solar panals with a swith
be warned i am good parrot but Dumber than a box of rocks
 
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