Since a 120V nominal pack should be charged to approx 150V, why not buy a PFC 2kW switching power supply for approx that voltage and add a small external circuit to limit current and voltage? The additional circuitry has been discussed in many threads on Endlesssphere as the E-bike folks like to use a cheap power supply as charger. Since most switching power supplies have a feedback circuit around a 431 regulator that has 2.5V reference, all that is needed is for the external circuit to act on that reference to get the supply to limit to a different (adjustable) output voltage or limit the current (this only requires a shunt resistor and an op-amp). The switching power supplies can typically be turned up/down by 5-10% in their default configuration, but an external circuit often expands this to about 30% so a nominal 120VDV power supply can be expected to regulate its output based on current limit and voltage feedback between approx 90 and 160V. Most switching power supplies have a limited range of duty cycle for the switching part, so they cannot be regulated too low or they will simply go into their protection mode - typically a hiccup after a timeout, so this won't charge your pack in a decent time. Best to check if someone has already tried this or buy one that you can return and first verify without making permanent changes that the output can be controlled down far enough.
Hope this clarifies, Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bruce EVangel Parmenter Sent: Friday, May 10, 2013 5:58 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Looking for adjustable charger (used) 96-120V The Schumacher charger link that was posted, only goes to 72V. Usually, in the $300 price range, that is an older charger technology item: a dumb charger that weighs too much and you have to watch it, as it might either cook or under charge the pack. If a viable charger does not present its self, then I have a different idea. The difference between your driver's 96V and your proposed upgraded 120V pack (using 8V PbSO4 wet-cells) is 24V. I am thinking four less-expensive 24V chargers to charge the 96V pack, or five 24V chargers to charge a 120V pack. Before anyone jumps in stating multiple points of failure, I have used multiple chargers to recharge my S-10 Blazer EV's pack. Years ago, I found it was less-expensive to grab the various models of 12V boat chargers (some brands offer 1, 2, 3, 4+ bank models to recharge 12V deep-cycle troweling batteries) http://brucedp.150m.com/blazer/dualprose030706-rear.jpg It worked and worked fine. However by today's standards, not as good as what can be had for an even lower cost. [This is what I did with my EV for the 15 years I had it. It was like a rolling test bench for EV charging: I would try out different chargers and report to the evdl.org what I had found. If I had my Blazer EV today, I would likely try-out the following idea.] I will assume your EV owner charges off level-1 a 120V 20A outlet. We would need to ensure the total AC input current draw (all the chargers added together) is not more than 16A. Now, let's see what charge current is possible when pulling off 120VAC 20A outlet drawing no more than 16A 120VAC * 16A = 1920watts. I found the dedicated 96V or 120V chargers closer to your price range ($300) were still too expensive, but they did show a recharge current flow of 10A for a 96V pack and 8A for a 120V pack. Researching some more, I found there are an abundance of low-cost, low-current 24V chargers used to recharge wheel-chairs, mobility-scooters, and kids-scooters. The lowest cost ones are 24V 2A smart chargers which I am thinking ca be clustered and used in parallel to get the charge current up to 8A. If you bought 20 of these, you could use them in either with a 96V pack or a 120V pack: 96V pack: 5 in parallel for each set of three 8V wet-cell batteries for a charge current of 10A or 120V pack: 4 in parallel for each set of three 8V wet-cell batteries for a current of 8A Someone might state that since all these chargers are smart, each of them will want to buck the other. While this is possible, I have found this to not be concern. Of the paralleled chargers I had on, one by chance, would be set slightly higher. All the other chargers would lower their output current as the dominant charger kept raising the surface voltage. During the 'bulk' charge phase (before the PbSO4 60%SOC point began tapering the current), all charger's outputs their max current. When the pack's tapering surface voltage was reached, the chargers would each taper accordingly. We are not talking about cooking a pack, but as the dominant charger finished its charge, the other chargers were either finished or their output current was very low. If any had concerns, then a good test for this case, would be to purchase three of these chargers, and use them in parallel to recharge a 24V PbSO4 pack. Then the current and voltages could be monitored to ensure all went well. I found some of these low cost chargers at: http://www.amazon.com/s/ref=sr_st?keywords=24V+2A&qid=1368163884&rh=n%3A 3375251%2Ck%3A24V+2A&sort=price Searching ebay, I found one http://www.ebay.com/itm/24V-2A-AC-DC-Adapter-Power-Supply-Cord-Charger-5 -5mm-Tip-For-LCD-Monitor-Printer-/290846323487?pt=Laptop_Adapters_Charge rs&hash=item43b7cab31f smart 2A 24V charger that can run off of a level-1 120VAC or a level-2 208-240VAC source (input: 100-240VAC). Choosing this type that can run off either would be wiser as in the future your customer could upgrade to be able to use the public J1772. These were $10.59/ea+free-shipping Quantity 20 = $211.8 which is under your price range. This idea may not be pretty, but if you want to keep the costs down, Yankee Ingenuity at the ready ... {brucedp.150m.com} ... http://en.wikipedia.org/wiki/Yankee_ingenuity - On Thu, May 9, 2013, at 03:04 PM, Steve Powers wrote: > I recently sold an EV with not much of a charger. It has a variac with > bridge, basically a bad boy charger. I'd really like to see the new > owner > with a better charger. He has it setup with 12x8V for 96V and may > upgrade > up to 120V max. It has a 120V controller, so he won't go over that. I > am > looking for something betterthan a bad boy charger, but in the $300 or > less > price range. I want it adjustable so he has the flexibility to increase > the voltage. I am thinking BC-20, Russco, etc. > > I didn't see anything on the EV Trading post that meets his needs. > > If you have one to sell, regardless of price, contact me off list. - -- http://www.fastmail.fm - Same, same, but different... _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
