Agreed re: open source. I will host code on Github as GPL, circuit diagrams etc, probably creative commons. I am right now in the process of moving house (done december 8), so I don't think I will post much of consequence - but I can post a framework of sorts so people feel ok about sharing.
Thanks for the input.
On Mon, Nov 11, 2013 at 1:52 PM, Kevin Pemberton <pembertonkevin@gmail.com> wrote:
I have not purchased ready made off shelf circuits. Many FET drive circuits have a drive for a flyback FET. FETs can be stacked for higher Amp loads with little extra component count. Over size your fet, (double voltage ratings at a minumum). That would be if you expect a max voltage of 50 v your FET should be rated for at least 100v. If you love your prossesor you should use opto isolators for driving the FETs. My buck boost circuits use P channel FETs, they are easer to implement. Expect to loose some fets.
On another note. Consider establishing an IRC for developing this if you are working on an open source project. It is time now to submit the project code with license so others know that can join your project without fear it will not be released later.
Kevin
On Nov 9, 2013 2:21 PM, <white74@telus.net> wrote:my only question on the ford escape cells is why use sanyo 5.5 ah cells when the tenergey ones are rated at 10 ah?
---In electricboats@yahoogroups.com, <mark.internet@...> wrote:
food for thought on the building of a 48 volt pack.
http://www.eaa-phev.org/wiki/Escape_PHEV_TechInfo
be very careful when taking apart 330 Volts !!!!!
These ford escape packs are nicely packaged in 6 volt strings that bolt together.
I have used a set for my 48 volt ebike.
I have setup my electric runabout boat with dual 48 volt packs.(my range requirements are quite minimal)
I hope to be able to charge multiple banks without manual intervention.From: oak <oak_box@...>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Thursday, November 7, 2013 12:20:15 PM
Subject: Re: [Electric Boats] RE: Battery Charging Basics - homebrew chargers
Dominic,The really cool thing about mosfets is that they have very, very little resistance. That's their claim to fame.With very tiny resistance, you don't need as much bulk.But you have a good point. Wasn't there something like 6 transistors on the board? So if you blindly do the math (don't do that, but just for giggles) - you're talking about 5A per transistor. And yes, you can pass 5A or 30V through a single wire of reasonable guage - for a VERY SHORT distance.But your "proof of concept" is also pretty much were I was going with my question (should I have pointed that to MIKE instead of "Eric??" - OOPS!!). Anyway - proof of concept is one thing. But the concept may not practically scale up to the huge power demands that our motors have.And even if it does - you need to be very careful about the noise that will be generated, back emf currents, etc...If you haven't tried controlling motors and relays with micro-controller boards - play with that a little bit first.If you haven't done it, go find a good article on driving small dc motors with controllers.You need to be sure you ALWAYS put diodes and/or capacitors across the switched device, so that the current backlash doesn't flip out, if not destroy your controller.Like you, my first and most immediate project is to get a reliable charger going so that I can get out and sail again without worrying about whether my batteries are charged.After that, I'd LOVE to have a chance to experiment, and tinker with other circuits. It would be nice to be able to run my 48V Torqeedo off a 24V battery bank so that I can play with it and lug half the weight (at an understandably much lower power and range).JohnFrom: Dominic Amann <dominic.amann@...>
To: electricboats@yahoogroups.com
Sent:
Subject: Re: [Electric Boats] RE: Battery Charging Basics - homebrew chargers
John - understood. I wouldn't expect to run 30A through the shield. I am using it as a proof of concept - a prototype that can charge one or two batteries. I would probably run single digit amps through this as it is configured.That said - the connectors on the mosfets themselves are pretty tiny. How would they achieve the claimed power?On Thu, Nov 7, 2013 at 2:33 PM, oak <oak_box@...> wrote:
Dominic,It's an interesting shield. But I'm not sure you really want to push up to 30A at 60V through those mosfets without at least adding huge heatsinks and a beefy fan. The sum of the device ratings may give you that, but it shouldn't be taken as a statement of what you can pass through the board. Certainly not through the itty bitty connectors on a shield board....
ERIC >>I've seen circuits and descriptions for capacitor based "charge pumps" or "voltage doublers". I've used these on cards with Maxim chips to provide the +/- 12V(ish) power supplies for RS-232 lines.But do you think that type of circuit can practically be used on a high power basis?There was a reference that I saw that claimed one of the Prius models used a boost type regulator to double the voltage so that the motors could operate a twice the voltage without having to double the number of batteries. But I don't think they were using capacitors to do it.I don't need to go over 48 volts, but it would be nice to be able to use a 24V bank to run a 48V motor - with, of course, the understanding that the same power drain at lower voltage means yet higher current, which is already getting tough on these banks....JohnFrom: Dominic Amann <dominic.amann@...>
To: electricboats@yahoogroups.com
Sent:Subject: Re: [Electric Boats] RE: Battery Charging Basics - homebrew chargers
John - here is a link to a useful circuit: <https://www.sparkfun.com/products/10618> providing up to 30 A at up to 60 V.On Tue, Nov 5, 2013 at 4:20 PM, oak <oak_box@...> wrote:
Kevin,I'd be VERY interested in learning a bit more about power supply design, since it is so useful in so many projects.I've seen the wiki pages, and a tutorial or two describing buck boost power supplies, but they're pretty vague.I've also seen references for parts (Maxim) that are designed for creating power supplies - but they're pretty much low voltage and low amperage.Do you have any references to current sample circuits using readily available parts that would deliver something on the order of 28-60 volts at maybe up to 2-5 amps?JohnFrom: Kevin Pemberton <pembertonkevin@...>
To: electricboats@yahoogroups.com
Sent: Tuesday, November 5, 2013 12:35 PM
Subject: Re: [Electric Boats] RE: Battery Charging Basics - homebrew chargers
Why not just add a capacitor across the output of the charger that is large enough to smooth the ripple? That is after all how power supplies give clean DC power.If you want to regulate output using an arduino controller consider using a buck boost circuit. James electonics had a nice PDF on the design info at one time so look for that. Using a buck boost with FET devices for the switch and flyback will reduce power input considerably. PWM is very lossey in comparison. If you are considering using this project for multiple inputs you need to leave PWM to less demanding projects.Most high tec batteries show signs of heat build up when no more chemical reaction takes place. The best chargers use this temp change to signal a full charge. An arduino can keep track of temp changes and make the design simple for a smart charger that would excell over any other design you may come up with.You can also get the atmel AVR programmer from digikey and get unprogrammed IC's and build a board without any outside components. This move could make the controller a 5 dollar project plus power devices.What I just discribed was my MPPT solar project. It can be done.KevinMark Stafford here agreeing with OakBox about the "very, very slow pulses" to finish charge lead-acid batteries. Define very very slow: 1.5 seconds between voltage spikes. This lets the nascent hydrogen or oxygen bubble dissipate instead of grow.
I can't document this 1.5 second number; I only recall it being between one and two seconds from previous info hunting. You could experiment with a fully charged FLA, then vary the pulse frequency to avoid bubbles over time. Or observe the behavior of smart chargers prior to float charging: they pulse about every 1.5 seconds.
Or just buy super cheap 10A LA or Li chargers from batteryspace.com. If they are not conformal coated already, you could disassemble and spray/paint/dip the boards for better moisture resistance.
Mark Stafford
--- In electricboats@yahoogroups.com, oak <oak_box@...> wrote:
>
> How are you stepping UP your voltage?
>
> Also - be careful about the PWM. Â If it were very, very slow pulses, then that might be ok. Â But if you're using fast pulses (in the sense of pwm), you could have problems. Â The following couple of paragraphs were in the BatteryUniversity.com web site under Lead Acid Charging:
>
> Ripple voltage imposed on the voltage of large stationary batteries also causes a problem. The voltage peak constitutes an overcharge, causing hydrogen evolution, while the valleys induce a brief discharge that creates a starved state that results in electrolyte depletion. Manufacturers typically limit the ripple to five percent, or 5A for a 100Ah battery.
> Much has been said about pulse charging of lead acid batteries. There are apparent advantages in reducing sulfation; however, manufacturers and service technicians are divided on the benefits, and the results are inconclusive. If sulfation could be measured with accuracy and the pulses applied as a corrective service, then the remedy could be beneficial. Assumptions without knowing the underlying results can be harmful.
>
>
> ________________________________
> From: "dominic.amann@..." <dominic.amann@...>
> To: electricboats@yahoogroups.com
> Sent: Tuesday, October 29, 2013 2:26 PM
> Subject: [Electric Boats] RE: Battery Charging Basics - homebrew chargers
>
>
>
> Â
> Hi John,
>
> I am embarking on a similar project. I expect to use a PWM source signal to charge the batteries. Ultimately, my goal is to have a super-charger, capable of having several inputs connected simultaneously (solar, alternator/generator, wind, "pushed" electric motor), charging multiple banks of batteries using per-bank profiles, and covering all popular types - FLA, AGM, Lithium. A smart controller such as the Arduino would be at the heart of the system - and it could produce a NMEA message string output for standardized monitoring.
>
> At the moment, I have a basic one-profile (FLA) charger configured that can control a single input between 8 and 18 v (yes, it will "step up") and charge the battery smoothly in the "best" time.
>
> I will open source the arduino code (written in "wiring") once I have properly tested it.
>
> In the end, the connectors will cost more than the MCU.
>
>
>
> ---In electricboats@yahoogroups.com, <electricboats@yahoogroups.com> wrote:
>
>
>
>
> I hope this will be both fun and educational....
>
> I'm trying to build a small, home brew battery charger. Â From what I see, it sounds like the primary difference between FLA, AGM, and Li batteries (from a CHARGING) perspective is the charging profile - notably, the voltage level of the charge.
>
> Granted, if you're trying to do a FAST charge with lots of amps, there are a lot more details to worry about. Â But given the limits of readily available parts, I'm looking at 1-2 amps charging current - so I think I can simplify things a LOT.
>
> It sounds like building a "constant current supply", attaching it to the battery (at 1-2 amps), and monitor the battery till the battery voltage comes up to the prescribed level, then disconnecting the current source.
>
> According to the Battery University (http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery), it looks like I can use a constant current source for the primary charging (stage 1), then maybe connect to a regulated power supply for the topping charge (stage 2), and then use a small microcontroller (Arduino) to monitor the voltage over the next few days / months, and occasionally turn on the "float charge" voltage for a couple of hours. Â (stage 3)
>
> Does this sound reasonable?
>
> For charging Lithium batteries, is there any difference, other than paying a LOT of attention to the voltage levels for the peak charge level?Â
>
> From the BatteryUniversity.com site, it sounds like charging Li batteries to 4.1V per cell, and stopping there will extend the life of the battery bank, and provide a bit more guardband to avoid problems.
>
> Thoughts?
>
> Thanks!
> John
>
--Dominic Amann
M 416-270-4587
Dominic Amann
M 416-270-4587
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