Hey Cor Thank you so much for all the great info! The solution suggested sounds very economical. As well thanks again to everyone on the list here, once again great response, help and info!
Cheers Dan On Wed, Apr 23, 2014 at 10:47 PM, Cor van de Water <[email protected]>wrote: > The datasheet for this module can be accessed from this page: > http://www.digikey.com/product-search/en?KeyWords=jw150a1 > (the other module that shares the same PCB that it is mounted on > is the JW150C1, the same 150W but 15V output instead of 5V) > The output from the JW150A1 can be trimmed from 3V to 5.5V > So from a nominal 48V battery bank, you can create a charging > voltage of between 51 to 53.5V which should allow charging > your boat batteries quickly to at least 80% from a half-empty > solar pack. > > The module has both a "trim" input as well as a remote on/off > so it is relatively straightforward to create a max output > voltage limit as well as a power down when the output voltage > goes over the max you want to provide. > Since you are charging sealed lead-acid batteries, I expect that > you like to keep the charging voltage below 14.2V per battery > and in case it does (if you are plugging in your boat during a > sunny day and the solar bank is also charged to its max voltage) > then you'd want the DC/DC converter to drop out, which might still > allow leakage from the solar bank to the boat, but never at a > higher voltage than the solar bank and since they are the same > batteries and configuration (4 series) this should not be > a problem in this case. > But if you never leave your boat plugged in and just want to > charge for a couple hours, then run the boat, the simplest solution is > to set the DC/DC converter for a fixed (boost) output voltage and > just run it all the time while charging your boat. > Note that this converter has current limit and it is allowed to run it > in current limit mode continuously which makes it a charger with a I-U > type profile. (Current limit until max voltage, then voltage limit) > The current limit is typically around 120% (36A). > The modules I have come with a small heatsink attached, but you > may need to add a larger heatsink or blower to remove excess heat when > running it in current limit mode, since the efficiency can drop to about > 83% at current limit, which means around 35 Watts may need to be > dissipated > during full-bore charging, if the unit overheats it will throttle itself > back but the internal electronics will not be too happy at that temp. > > If you want to run a controlled output voltage then it will be needed to > add a little circuit to trim the output based on the voltage > measurement, > but when you just need it to provide a fixed voltage the circuit is as > simple as a resistor attached to the trim pin. > If I am not mistaken, I have offered these converters on a board in the > past with 2 converters > (1 for 5V and 1 for 15V, so both a JW150A1 and a JW150C1 on a PCB with > some external components to regulate the 48V inrush and filter noise) > for $25 plus shipping. > > Here are the datasheets for the two converters: > http://www.digikey.com/product-search/en?KeyWords=jw150a1 > http://www.digikey.com/product-search/en?KeyWords=jw150c1 > > Let me know if you have any questions. > > Regards, > > 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 Lee Hart > Sent: Tuesday, April 22, 2014 2:18 PM > To: Electric Vehicle Discussion List > Subject: Re: [EVDL] Charging your EV pack from other batteries? > > Dan Baker wrote: > > Thank you everyone for the replies so far- as hoped lots of fantastic > info! > > So it sounds like Cor's idea and Marco's drawing are my best bet. > So I > > guess my only other question would be around this charging scheme is > would > > I need to regulate the charge control once the EV pack reaches full > charge > > (i.e. prevent overcharging)? Would I have to implement a timer? > > Cor, please yes send me info and pricing on your brick DC/DC module. > > Cor's solution is a good one. The DC/DC can boost the voltage so the > destination pack can reach "full" even if the source pack isn't full. > > You will need to decide what charging algorithm you want to use. Then > provide hardware to do it. > > The simplest algorithm is just a constant voltage charger. You would > wire the control input of the DC/DC to hold the *total* voltage applied > to the destination battery at something like 2.25v/cell (13.5v per 12v > battery; 54v for a 48v pack). That will work, but could take a day or > more to reach full charge. > > Or, you can set the DC/DC's output to charge as fast as it can, until > the destination battery reaches something like 2.5v (15v per 12v > battery, or 60v for a 48v pack). Then hold the battery at this voltage > until a) the current falls under 2% of its amphour capacity, or b) the > current stops falling, or c) some period of time has elapsed (1/2 to 4 > hours). This would take a lot more effort to set up, but would also > reach full charge much faster. > > -- > Any intelligent fool can make things bigger, more complex, and more > violent. It takes a touch of genius, and a lot of courage, to move > in the opposite direction. -- Albert Einstein > -- > Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm > _______________________________________________ > 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) > > -------------- next part -------------- An HTML attachment was scrubbed... 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