Solar / low voltage charging

[dermot]

Quite some time back, I commented on a thread about a DC-DC converter I was designing to charge up to 72V from a 12V DC input to charge my folder while it was in the car.

Well, it sort of worked, but not reliably or efficiently enough to want to post it here.

Recently, I bought several of these:

http://www.ebay.co.uk/itm/1pcs-Boost-DC-DC-Converter-Power-Supply-Step-up-Module-10-60V-to-12-80V-600W-mah-/251286948321?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item3a81de89e1

At less than £12 each, there are very cost-effective.

I wouldn't care to comment on the 600W rating, but I've run it at half that entirely successfully - it has adjustable voltage and current limit (interestingly, the current limit sets the *input* current, so the output current limit isn't exact - though once set, seems repeatable.

I have many dozens of old Dell DA-2 mini-desktop external power 'bricks' rated at 12V 18A - marrying up one of each makes for a fine low-ish power (~150W) charger.

The limit is the input current to the DC-DC converter - running 24V in from a series pair of the Dell PSUs and the converter seems happy to run at 300W indefinitely (but if you want to do this, there are a couple of tweaks you'll need to do with the Dells first...)

Dermot

 

[major]

Hi dermot,

I bought one like that a few months ago. I was thinking of using it to charge a 45V battery from a 30V PV panel. I had to resolder the caps as it arrived it bad shape. I guess that's what you get for free shipping from China. It did appear to work on the bench. I managed to blow the fuse so it seems current limit can be adjusted above safe spot. I wasn't able to really take it far enough to try charging from the PV before winter set in here. In the mean time I bought another similar unit to play with: http://www.ebay.com/itm/171122662244?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 Free shipping again and again it arrived damaged. 2 months later I did get replacement board which works but I can't seem to get much over 80W out of it. No instruction or manual is available. I'll just keep playing around with it.