Home made charger?

[Justme]

I have a damaged (by slugs) Victron inverter charger (1500w 12v 50amps).

Its not repairable as the slugs have eroded the PCB & components.

However the transformer is still in good condition. I was thinking of making a simple "bulk" phase charger to supplement my existing charger.

It could be controlled purely by total running time per activation or to go off when the V hits a set level. Or poss even by the VS in my main Victron but I did have other ideas for that.

As the bat bank is so big (2800ah) I dont think that a 50 amp charger is going to be to much of a risk as that is about its end charge level. The main unit has a 120 amp charger but tends to hold around the 100amp mark.

I know I will need a rectifier pack to change the AC to DC. I already have a cheapo 50amp charger that could donate its innards if needed but not sure if that will actually gain me any thing above using the cheapo charger.

Will a simple 4 diode rectifier be enough?

There are 3 thinner input leads & 3 thicker output leads.

Each set of 3 connects to each other but not to the other set.

Resistance is very close in all permutations.

I guess I can wire up the input in 3 dif ways & see what the output measures in the 9 different ways (3 ways by 3 inputs).

Any suggestions?

[Justme]

Here is a pic of the transformer

[SimonHobson]

You need to find out how the transformer is connected. It may be that the secondary is centre tapped, or it might be that there are two tappings to allow adjustment of voltage (and hence current) - although that's more normally done on the primary. Also you'll need to know what the voltage(s) is/are.

The type of transformer will affect the rectifier connections you'd want.

As to controlling it, one method that comes to mind would be to switch it on/off based on the main charger current. Eg, switch it on when the main charger goes above (say) 70A, and off when it drops below (say) 30A. That way the main charger will take care of voltage (and hence charge) regulation, and your second one will just assist it when demand is high.
On the other hand - if the main charger is 'intelligent' then the last thing you want to do is add another charger as that will give the monitoring a false indication of battery state and upset it's program.
It might be better to keep your 50A as a reserve and just use it manually if the main charger breaks down.

[Justme]

I ran it up a few days ago.

The primary is centre taped as is the secondary.

Depending on how I power the primary (either end to centre or end to end) the secondary is between 15v & 30v OCV for end to centre or end to end.

Not quite sure how the current will pan out. You have to remember that its first use was as an inverter & charger so was set up for both ways.

Dont think I will need to worry about the charge levels as my bank is so big (2800ah @ 5C). So it can soak up all I can chuck at it.

So even with all charge sources (inverter/charger 120amps solar 80 amps charger 50amps) running flat out I am still under 10% charge rate.

Even the 100% SOC float amps rate is quite high.

The simplest way to control it would be to have it cut out 0.05v below the absorb voltage setting on the inverter. I could even use the inverter charger output relay to do that but its in use as a genny start for high load control (battery SOC control is done by another system). My solar controller also has a controllable relay but not sure what configuration settings it has available yet.

[Alan]

Quote “ I have a damaged (by slugs) Victron inverter charger (1500w 12v 50amps). “


The transformer does not look very big.

12 volts at 50 amps will only give 600 watts.
It looks a bit small for 600 watts just trying to gauge a size from the bar going
across the wooden chair.

Was the transformer just for a trickle charge. ?

Regards

Alan

[Justme]

I guess you have never picked up a Victron unit.

Its about 15kg inc the box.

The actual transformer is 7" x 6" x 5". The wiring on both the primary & secondary are quite large / thick, the secondary being almost solid bar.

The inverter charger was a 1500w/50amp/12v unit.

They are never evenly matched for inverted & charger outputs. My current unit is 3000/120/12. When inverting it uses 250amps but can also run at 6000w for a few seconds so 500amps is possible.