Maplin Bench Power Supplies

[samtheeagle]

I've just grabbed a 13.8V regulated mains power unit from my local Maplin. For some reason they seem to have the 7A and the 10A versions for sale at the same price. I'm sure that in the past when I looked at these the 10A version was a good £20-30 more expensive. It seemed like too good a deal to pass up. I've seen lots of people recommending these, so I thought I'd grab one now, in anticipation of my obsy being ready.

http://www.maplin.co.uk/13.8v-regulated-mains-power-units-231

[keithatrochdale]

It is very easy to convert a computer PSU, just do a search on the net.

Why, because it cost a lot, lot less!

[samtheeagle]

A very good point! I'd never considered that, which is daft considering I always build my own pcs from scratch!

[Photosbykev]

the downside of using a computer psu is it is regulated to 12v exactly and any volts drop down the cable means you are undervolting the system. Whereas the maplins units are at 13.8v, replicating a fully charged battery, which most 12v systems will work better at especially the mounts.

[keithatrochdale]

As the OP said it was for his obby, I assumed it would have mains available and thus the PSU would be quite close to the mount.

I do not know what length of 12v supply cable you were thinking of, but voltage drop will be minimal.

And I thought a fully charged lead acid battery gave out 14.2v

[malc-c]

PC power supplies are switching supplies. The Maplin 13.8v regulated supplies tend to be linear mode, which IMO are more suited to supplying power to driven mounts, dew controllers etc.

[Photosbykev]

I don't think I've ever seen a fully charged battery give out 14.2v? It might for a few minutes but it will quickly drop down to 13+ volts and then level out in the high 12 volts range.

It doesn't take many amps or cable distance to very quickly drop a 12v supply down to 10 volts or less unless you use a cable with a decent CSA and most mounts will benefit from be supplied with 12 - 15 volts

[David JM]

For vehicle batteries 12.7v is 'fully charged', the charging circuit puts out 13.5v at tickover and tops out at around 14v where the regulator stops any higher voltage passing to the battery and cooking it.

A Honda CB500 will travel just under 20 miles on a fully charged battery with the lights off but normal use of indicators and brake light if the charging circuit fails. The last 200 yards home can be easily pushed if the swearing is kept to a minimum.

[Rols]

Thanks for the heads up i just reserved myself a 10A PSU.