Battery charging

[Dodgey]

Ive been using pc power supplies for charging rc heli batteries for years. As mentioned above, all you have to do is connect the , usually green, power detect lead to ground, and then put a resistor accross the 5v rail to increase amperage ( not totally nesc but it ups the amperage normally)

This way you get a 300w (25amp) 12v psu for £17 (pcworld) which is more than enough for your fridge (around 40w) , plus your other bits and bobs, and your charger, and your stereo providing you are not running a sub

One simple relay and it replaces the zig unit completely.

[g8dhe]

Just some words of caution about using PC PSU's;
1. They are regulated to 12.0 - 12.6 volts so L/B or S/B charging isn't going to be very effective at all.
2. Make sure that they PSU is an ATX12v specification and NOT an older type where the 12 volt line would only handle 1-2 amps!!
3. Make sure you spread the load over ALL the +12 volt wires and connectors.
4. Remember they need cooling and ventilation don't block the path of the fan and that the air intake is cool air.

[Observer]

I hard wired and fixed inside my conversion a Lidl Ctek alike......wired to the LB and I just select the mode and it charges both LB & SB in 18 hrs...via the willinton set up... works for me...

I would like to do this. There's about 6' of cable at the battery side of my Lidl job so assuming that you spliced in an extension cable to yours to reach your charger site (in a cupboard?), what size (rating mm2) did you use and how long in feet? My charger says max 3.8 amps so I'm hoping to use 2mm2

Cheers Pete

[Dodgey]

Just use cable that when stripped, looks similar to the existing cable - it really is low amperage stuff with trickle chargers. Grab some wire from Halfords or similar that is rated at 7 amps or above. The 17amp stuff they do is more than enough.

[Dodgey]

Just some words of caution about using PC PSU's;
1. They are regulated to 12.0 - 12.6 volts so L/B or S/B charging isn't going to be very effective at all.
2. Make sure that they PSU is an ATX12v specification and NOT an older type where the 12 volt line would only handle 1-2 amps!!
3. Make sure you spread the load over ALL the +12 volt wires and connectors.
4. Remember they need cooling and ventilation don't block the path of the fan and that the air intake is cool air.

Only just saw this !

1 - I don't use the 12v PSU for battery charging - I use a relay that simply puts the PSU 12v supply inline instead of the LB when the PSU is powered up - works well - powers my fridge, radio etc no probs.

For charging the LB I use an Optimate 12v trickle charger that is plugged into the 240v circuit in the van. The 12v charging output is also on a relay so it is disconnected from the LB when the mains is off. This is because the Optimate LED glows when the mains is off and it is still connected to the LB - and I think it was draining my battery.

3- All the wires inside the PSU go back to one terminal on the PCB - I used two lives and two earths, twisted together, to get a sufficient thickness of wire. We are only looking at 10Amps max in my setup. I cut back most of the other cables for neatness.

4. Good point about venting - though the PSU's are hardly doing any work at all so they don't get hot so I didn't loose any sleep over providing fresh cool air.

[Observer]

Just use cable that when stripped, looks similar to the existing cable - it really is low amperage stuff with trickle chargers. Grab some wire from Halfords or similar that is rated at 7 amps or above. The 17amp stuff they do is more than enough.

What if the LB got very flat, would the load on the smart charger increase or is it 'smart' enough to sort it?

[Dodgey]

The smart chargers like the CTek and Optimate are low amperage chargers - they max out at a few amps. They won't go over that. They are not "power supplies" - i.e. they will not provide enough current to power a fridge etc. They charge in pulses, monitoring the voltage of the battery and decreasing the current as the battery fills, or increasing it as it needs to if the battery is low.

Certainly, the Optimate will just switch between "modes" as it "sees" the state of the battery change.

Either way, you won't bet getting more than a few amps out of the charger.

[Observer]

1 - I don't use the 12v PSU for battery charging - I use a relay that simply puts the PSU 12v supply inline instead of the LB when the PSU is powered up - works well - powers my fridge, radio etc no probs.

For charging the LB I use an Optimate 12v trickle charger that is plugged into the 240v circuit in the van. The 12v charging output is also on a relay so it is disconnected from the LB when the mains is off. This is because the Optimate LED glows when the mains is off and it is still connected to the LB - and I think it was draining my battery.

3- All the wires inside the PSU go back to one terminal on the PCB - I used two lives and two earths, twisted together, to get a sufficient thickness of wire. We are only looking at 10Amps max in my setup. I cut back most of the other cables for neatness.

4. Good point about venting - though the PSU's are hardly doing any work at all so they don't get hot so I didn't loose any sleep over providing fresh cool air.

Are all PC PSU's 12 volt output?

[g8dhe]

PC power supplies have MULTIPLE outputs, ranging from +12,+5v,+3.3,0,-5v & -12v, more modern ones probably won't have the -ve supplies. Each output voltage will also appear on several sockets via multiple wires in some cases as you can be talking of LOTS of amps (10-20Amps) for the lower voltages!