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adamj12b 04-20-2010 01:25 PM

Open Source 6Kw Charger. Who Whats What Features?
Hello Everyone,

Clyde (williamson) came to me a few weeks ago with plans he has put together for a 6kW Charger. He has many years of experience designing high output power supplies. This charger is PFC corrected and Isolated. It can take 85-265VAC input at 50 or 60Hz. With the output being isolated, You cannot easily be shocked if you are working on the car while charging. The charger automatically detects what voltage it is powered with and adjusts it max draw as to try and not trip the circuit breaker. 15A for 115VAC and 30A for 230VAC. There will also be an adjustment knob on the front of the charger for turning the max current draw on that voltage down, if other loads are on the same circuit.

The limits of the charger right now is that it can only charge the battery voltage that is was wired for. While this can be changed, It requires removing or adding winds to the transformer to decrease or increase the voltage output. A small resistor mod is also required at the same time.

I am hoping to put together kits for people to build their own chargers specific to the voltages they want. This will be a modular design that you will be able to get different modules that will plug in to change the output stage to the voltage needed to charge the pack you want.

The charger should cost somewhere in the range of a few hundred dollars and each new output module will most likely be around one hundred each. I am not certain of these prices yet, as It is still in prototype phase.

So I need to know what you guys are looking for in a charger. Wether it be Higher Power, Wide Output, Narrow Output, Isolated, Non Isolated, Also what Kind of controls.

With the module setup, The controller could be programmed to remember a profile for each one, With different setpoints and charge currents.

Also, For reference, The Manzanita PFC 30 charger is alot like this one. It is not isolated and has an output range of 12-450VDC.

I want to know what you guys think!!


Bicycle Bob 04-20-2010 04:01 PM

I'm not shopping these days, but if I was, I'd be mostly concerned that the charger was smart about prolonging battery life. Perhaps a "fast charge to X%" control would be a great feature, too. In a portable charger, I'd want at least two cords, so I could take advantage of split duplex outlets. Even better would be cords set up to accept any combination.

jackbauer 04-20-2010 05:43 PM

I want a charger with wide voltage range , a simple digital display and controls and lots of amps! Not worried about isolation.

sawickm 04-20-2010 08:36 PM


Originally Posted by adamj12b (Post 171372)

Also, For reference, The Manzanita PFC 30 charger is alot like this one. It is not isolated and has an output range of 12-450VDC.

Spec's similar to a $2,700.00 Manzanita PFC 30 would be nice !!!! :thumbup:

rmay635703 04-20-2010 09:39 PM

For a charger an analog or digital (I could care less) display of volts/amps is nice. I like haveing a fairly wide range of voltages and a trim for finish.

Meaning something like my schumacher multivolt except I would like a simple cutoff so it doesn't severely overcharge. Even better would be 2 stage like my old K&W BC-20 where I can set the amps and the finishing charge voltage trim.
(I loved my K&W BC-20)

Output current isn't extremely important (but control of it might be since I opportunity charge and 10amp outlets need to be ramped down), but overcharge protection is (since I can't design that well myself)

In other words, the thing should shut down once the batteries are fully charged unless equalize or some other setting is chosen.


dcb 04-20-2010 09:51 PM

Something for us cheapskates to try to revive old batteries of various chemistries and sizes with would be cool, with a built in smart charger :)

NiHaoMike 04-20-2010 11:59 PM

I don't think there's any point in isolation since it is expensive, inefficient, and does not really provide much of a safety advantage since the output is still high voltage. If anything, isolation may make for a false impression of safety in a high voltage circuit. (I know of an electrical engineer who got zapped by an isolated 300v power supply because one side was grounded by the scope probe. She lived to tell the story, but it shows that isolated high voltage power supplies are not safe!)

PFC is normally unnecessary for home use, but it is easy to integrate it into a charger design. Just have rectified AC supply a buck/boost converter (buck followed by boost, with a shared inductor), with a few small, high ripple current capacitors to ensure a low source impedance. It will support a very wide range of output voltages. up to 450v or so is reasonable depending on the rating of the components. Regulation compliance can go all the way to 0v.

There will definitely have to be some analog control circuits. A good and simple way to control a buck/boost converter is to use double hysteresis current mode control. Basically, the buck part has a slightly higher setpoint than the boost part, such that the hysteresis ranges do not overlap. The setpoints are determined by more control circuits. There will be a comparator to set a "dead band" during which the converter stops operating, since efficiency is poor during low instantaneous input voltage. A clamp circuit can limit maximum input current as desired by limiting maximum control voltage. Another circuit will limit maximum output voltage.

The charge control can be either analog or digital. For lead acid, simply adding a timer to reduce the output voltage a time after the setpoint voltage is reached is enough. For Lithium or other chemistries, a microcontroller can be used to provide primary charge control. It can also use a control signal from the BMS.

One of my current projects is a high efficiency inverter-based power supply/float charger for a home network. It operates at much lower voltages and power levels, but the basic concept is the same.

velosolex50 01-18-2011 02:52 PM

How about a 48v lead acid charger that can run off a small generator without stalling it? I have a Reva G-Wiz :turtle:and a 1 kva generator but the on-board charger draws nearly 3kw in the early charge phase, so I can't use it for topups. A 3kva generator is too big and awkward for the car. A charger as above would be very handy

TheSGC 01-20-2011 06:56 AM

I'm looking for something that has the automatic input voltage adjustment, automatic shut down and I can move between lead acid and lithium easily. Also, a cost less than $400 would be nice.

I have a K&W BC-20 right now and it's a great charger, I just wish it shut down when done. And provided more power, I have access to 120 volt and 220 volt plugs but don't have a charger capable of handling 220v. Yet.:D

jackbauer 01-20-2011 02:41 PM

The open source charger of Simon Rafferty and myself fits that bill. Mine has been working for over a year now and just recently switched to lithium. Holds within 0.2v on cv phase.

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