DIY Open Source EV Charger - Page 26 - Fuel Economy, Hypermiling, EcoModding News and Forum

williamson · 02-04-2010, 04:29 PM

As was suggested on this site, 230v full-wave gives about 150 volts as you all know, but the white wire can be the negative lead. In NY state, they require the traction voltage (motor, controller & Batts) to be floating. So such a charger would be isolated from the chassis. You are absolutely right about a PFC cicuit, unless you don't care, like me. I ran a #6 cable (60 amps) into my garage, from a 100 amp breaker. I know-I'm a bad boy! What about the PFC circuit doing voltage regulation?

williamson · 02-04-2010, 04:31 PM

You could reach 12 batteries with a 12volt AC filament transformer, rated about 40 amps.--not too big--added to boost the line.

williamson · 02-05-2010, 04:27 PM

I'm having a pcb laid out for a SLA lights and accesory battery on-board charger. Open-source. 14.5 volts, target 90 amps. From the 144v traction batt's. Does any one know of a similar project forum, or where if someone starts a forum for me, I will publish all progress.

NiHaoMike · 02-05-2010, 06:03 PM

Quote:

Originally Posted by williamson

I'm having a pcb laid out for a SLA lights and accesory battery on-board charger. Open-source. 14.5 volts, target 90 amps. From the 144v traction batt's. Does any one know of a similar project forum, or where if someone starts a forum for me, I will publish all progress.

http://ecomodder.com/forum/showthrea...rter-8520.html
I'm working on something similar that converts 340v DC (voltage doubled 120v AC) to 12.8-14.6v DC (externally controlled) at up to 35A, but it's for IT use. The idea is to eliminate the very wasteful DC-AC-DC conversion in a standard UPS setup. It's something like the 48v DC system used in some data centers except it is intended for home use.

With a different transformer and inverter components, it should be possible to design one that runs from 144v.

jackbauer · 02-12-2010, 10:38 AM

Ok major progress today. I've been dogged by the voltage readings going very high at anything over 10 amps. Charging 4 batts i had to set it to 200v to charge at any real power despite the voltage never exceeding 58v in reality. Its a pure noise issue related to the layout of the components etc and its a generally noisy environment for the sparkfun board in any event.

Last night I had a brainwave. The voltage measurement is fine with the charger off so i coded the voltage measuring subroutine to put the pwm at 0 , take a few readings and average and then return the pwm to its previous value! What a difference! Today I ran the batts down a bit and opened the charger up to 30amps! Voltage read perfectly and the heatsink topped out at 33C! Ran a full 3 stage charge with voltage based transisitions not a problem. At high currents the inductor makes a tick-tick-tick sound. Reminds me of faulty tv line output stages!

Another unintended consequence of this setup is that the charger is measuring the pack voltage at zero charger current. This makes the voltage reading much more vaild. I subscribe to Jack Rikard's views on the bottom balancing / bms issues and i have seen that the voltage of a battery on charge is entirely dependant on charge current. Even today on absorbsion charge i had set the charger to an equivalent of 14.5v per battery. 14.8 being the max. Voltages were 14.5 , 14.3 , 14.2 and 14.4. I had the opertunity to speak to odyssey yesterday and they confirmed that they no longer recommend charging to 14.7v for anything more than 2 series connected batteries. they suggest setting the charger to 14.4v to allow for the slight tolerance in capacity.

MPaulHolmes · 02-12-2010, 11:29 AM

That was a brain wave! Very Very nice idea! Isn't is so much fun when you think of something and it actually works! So elegant and simple. You are the man... We need to write to Jack Bauer, and tell him that he has been replaced by a new and improved Jack Bauer.