Re: (ET) Battery charger and more

[jlantonucci <jlantonucci comcast net>]

I have both the Landis controller and the GE timer on my tractors.    I 
use both.    I use the timer for over charging a bit to get the pack 
voltage up and if I charge half way through a mow.    I also added a fuse 
to the AC side.    I can't believe GE didn't include one.
  

  

  

  
  
  
  
  
>   
> On Oct 12, 2021 at 4:14 PM, PH via Elec-trak  <elec-trak cosmos phy 
> tufts edu>  wrote:
>   
>   
>  Hi Dean and all,I agree about your comments on the Landis. This is a 
> great update for the ET charger.With the Landis, the pack stays charged 
> to about 38.5 vdc.I modified Landis small pot, with a ten-turn larger 
> pot and a counter dial.
>
> Batteries are Exide GC-135 from Rural King and Rural King delivered the 
> batteries to my home.The RK delivery guys would not leave until the 
> batteries were installed to watch the C-185 in action.
> In addition, I monitor the kwh before mowing with a Intertek power meter 
> and normally usage is about 2.5 kwh after a one week charge.
>
> Thanks,Paul HolzschuherLebanon Ohio
>
>
>
>
>  On Tuesday, October 12, 2021, 11:28:27 AM EDT, Dean Stuckmann via 
> Elec-trak  <elec-trak cosmos phy tufts edu>  wrote:  
>   
>  Hi,I’ve been charging my Elec-Traks with the built in charger since 
> 1980 and I’m NOT a battery expert. A timer failure 15-20 years ago 
> prompted me to replace the timers with Landis controllers. There have 
> been pro/con discussions about them over the years but, I think that 
> they work great. I have mine set to 41V (38V is the recommended setting) 
> and average 7 years of functional use out of a pack (typically East 
> Penn). I add water about twice a year. Now before people say that I 
> should get more life out of them, I cut about 4 acres of lawn a week 
> (for 5-6 months of the year) and the battery pack gets abused.  
> The built in charger may be a bit crude (so are the batteries!) but 
> gives me the convenience to plug in anywhere. Some of the lawn I cut is 
> the neighbor’s vineyard. Being able to plug in on location if needed, is 
> handy. Maybe you could do the same by mounting a smart charger in the 
> tractor but if you have multiple tractors, chargers could get expensive.
> The Landis takes the guess work out of charging a pack. No overcharging 
> or undercharging a pack. No checking battery voltages to see if you set 
> the timer right. Just plug it in and forget it. My tractors are 
> typically left plugged in all season and I let the Landis do its thing. 
> However, once they sit unused for extended periods of time (like my 
> snowblower tractor), I usually unplug them after a charge. About every 
> two months I’ll plug it in again to bring the pack back up and then 
> unplug it again. That is my charging maintenance mode. It also takes the 
> worry of overcharging due to a charger failure.
> It may not be perfect but works pretty good for me.  
> Regards,
> Dean A. Stuckmann5432 County Road UNewton, WI 53063
>
>
>
> On Oct 9, 2021, at 1:15 AM, David Roden  <etpost drmm net>  wrote:
> The GE charger is actually not an awful choice for the flooded golf car  
> batteries that most people use. It has some voltage regulation because  
> it's a ferroresonant design. Left to its own devices, it would probalby  
> overcharge, but the timer (if it's working) puts something of an upper  
> limit on that overcharging.  
>
> Think about it. Golf car batteries typically are rated for a life of  
> around 700 80% DOD cycles. If you use your ET every week, that's about 
> 14  
> years. From what I hear, most folks get around 10 years. So - not awful.
>
> But suppose your GE charger is kaputt, or you just want something easier 
> on  
> your battery.
>
> Below is a rather long article on smart charging, a piece that I wrote 
> for  
> the EVDL about 12-15 years ago. Lead batteries haven't changed much in  
> that time. :-) It might help you choose a smart charger for your ET.
>
> One thing I want to underscore in it is the importance of ENOUGH 
> CURRENT.  
> You might be temtped to buy a small charger because it's cheap. Don't do 
>  
> it! As explained below, your charger should be able to supply 20-25 
> amps.  
> At the very least, don't go smaller than 10 amps.
>
> Besides, charging at 5 amps takes about a day and a half just to get to 
> 80%  
> charged, and easily another day or so to finish. If you have work to do  
> with your ET, you may not have that kind of time.
>
> ----
>
> Smart Charger Algorithms - How smart chargers "think"
>
> Why You Need a Smart Charger: As long as you're using simple golf car  
> batteries, actually, you don't. Golf car batteries are relatively easy 
> to  
> charge, and fairly tolerant of a few charging errors now and then.
>
> But you might WANT one. Charging manually takes a fair bit of work and  
> attention. These days, practically every other rechargeable gadget has 
> an  
> automatic charger, or at least one we don't have to pay much attention 
> to.  
> So most of us just aren't used to manual charging.
>
> What a Smart Charger Does: It provides basic battery care and feeding,  
> automated, so you don't have to sweat it. It might have a microprocessor 
>  
> "brain," or discrete logic, or just linear circuits; but in some way it  
> tries to figure out the battery's current state of charge, and how to 
> get  
> it to a full charge as quickly and safely as possible. The rules it 
> follows  
> in doing that we call a charging algorithm.
>
> Alphabet soup: Probably the most common algorithms in smart chargers are 
> IU  
> and its variants, IUI and IUU. Here each letter represents one phase or  
> period of charging, so this is two phase charging or three phase 
> charging  
> The I stands for constant current, and the U stands for constant 
> voltage.  
> I'll explain those terms in a moment.
>
> Charging Phase One: The first phase of the charge is what we call bulk  
> charging.
>
> Initial Charging Rate: Theoretically, as long your charger is mindful of 
>  
> the battery's temperature, in this phase it can stuff in the electrons  
> about as fast as the battery can dish them out when you discharge it. 
> This  
> can be in the hundreds of amps for golf car batteries, and some AGM  
> batteries can handle charging currents in four figures! But the rule of  
> thumb on initial charge rate is somewhere between C20 / 10 and C20 / 4.
>
> That looks like some kind of code, doesn't it? C20 is the battery's 
> 20-hour  
> amp-hour rating -- that is, how many amp hours it can produce if you  
> discharge it over 20 hours' time. (The faster you discharge a lead 
> battery,  
> the fewer amp-hours you can get from it. Most battery manufacturers 
> specify  
> the battery's capacity at at least 2 different discharge rates.) 
> Amp-hours  
> are not the same as amps, but they're a handy way to express the size of 
>  
> the battery and its current requirements, so in this case, we use them 
> that  
> way. Thus for your typical 220 amp-hour (20 hour rate) golf car battery, 
>  
> you want to use an initial charging rate between C20 / 10 (22 amps) and 
> C20  
> / 4 (55 amps).
>
> Why Initial Rate Matters: Lead batteries aren't like the nickel cadmium 
> and  
> nickel metal hydride batteries you use in flashlights and cameras. Those 
>  
> little batteries appreciate being charged slowly, and they'll last 
> longer  
> (for more charging cycles) when they're treated that way. However, lead  
> batteries actually LIKE and NEED an initial charging rate of at least 
> C20 /  
> 10, some even more.
>
> I'm just a hobbyist, not an electrochemist, so I don't know the  
> electrochemical reasons behind this. What I do know is that that lead  
> batteries lose capacity (wear out) faster if they're not given this high-
> current jolt for at least a few minutes at the start of the charge cycle.
>
> Hawker Genesis AGM batteries from the 1990s were poster children for 
> this.  
> They could lose half their capacity in under a year without it. However, 
>  
> all lead batteries benefit from high initial current. The engineers know 
>  
> what they're doing when they recommend C20 / 10 as a minimum.
>
> Constant current: When a battery is flat, its voltage is low. This means 
> it  
> can take (and wants) a huge charging current. As it charges, its voltage 
>  
> rises, so a fixed-voltage charger's current falls. This slows down the  
> charge.
>
> But one of your smart charger's missions in life is to charge the 
> battery  
> as fast as it can. To do this, it sets its own voltage so the charging  
> current is as high as it and the battery can tolerate. Then, as the  
> battery's voltage rises, the charger keeps bumping up its own voltage so 
>  
> the charging current stays high until the last possible minute (we'll 
> see  
> when that is soon). This process is called constant current charging.
>
> During the bulk charging phase, nearly all of the charging energy goes 
> into  
> the charging reaction. As the bulk phase proceeds, with the current held 
>  
> constant, the battery's voltage rises. When the battery is about 80%  
> charged, it reaches the gassing voltage. From here on, more and more of 
> the  
> charging energy goes into heating the battery and dissociating the  
> electrolyte's water into hydrogen and oxygen. We'll soon see why this 
> heat  
> matters.
>
> Gassing voltage depends on the battery's design -- the composition of 
> the  
> positive and negative grids, and the chemical makeup of the electrolyte. 
>  
> For a typical flooded golf car battery, it's 2.4 volts per cell (VPC) at 
>  
> 25° Celsius. Other battery types will vary from 2.35 VPC to 2.5 VPC. 
> Check  
> your batteries' datasheet.
>
> Temperature Compensation: A good charger will adjust this voltage, and 
> all  
> the voltages that follow below, for battery temperatures significantly  
> higher or lower than 25° Celsius. You get the adjustment factor from 
> your  
> battery manufacturer, but a typical one is -3mv or -4mv per cell per  
> Celsius degree deviation from 25° C.
>
> This isn't ambient (air) temperature, but rather battery temperature. 
> The  
> ideal way to read it would be to immerse a temperature sensor in the  
> battery's electrolyte. However, the usual way is to bury a sensor 
> between  
> two batteries in the middle of the pack. I've also heard of attaching a  
> sensor to a battery terminal post.
>
> Temperature compensation (TC) is more important for valve regulated (AGM 
>  
> and gel) batteries than for flooded ones, but if you have it available 
> on  
> your charger, there's no reason not to use it with flooded batteries, 
> too.
>
> Charging Phase Two: Reaching the gassing voltage ends the bulk phase and 
>  
> begins the absorption phase. The battery is now about 80% charged.  
> Depending on the charger's algorithm, the remaining 20% may take about 
> as  
> long as the first 80% did!
>
> In the absorption phase of an IU charging algorithm, the charger holds 
> the  
> voltage steady (constant voltage charging) at the gassing voltage. 
> Remember  
> how the voltage rose when we held the current steady? Now the charger 
> holds  
> the voltage steady, so the charging current falls. The charger sits 
> tight  
> until the charging current has declined to about C20 / 50. For our 
> example  
> 220ah golf car battery, that would be 4.4 amps.
>
> At this point the battery is essentially full. The charger can shut off  
> now, or you can pull the plug manually.
>
> But maybe you shouldn't, at least not every time. That's because 
> although  
> the battery is full, some of its cells are a little fuller than others.
>
> Cell Imbalance: The cells in a battery vary a bit in how fast they 
> charge.  
> Part of this is down to slight differences in their manufacturing  
> tolerances.
>
> A larger factor in cell imbalance is that the cells vary in temperature, 
>  
> sometimes a lot. In each battery, the inner cell or cells will usually 
> be  
> warmer than the ones toward the outside of the battery. In a large 
> battery  
> pack, the inside batteries will also be warmer than the outside ones. So 
> it  
> isn't unusual for cell temperatures to differ by 10 or more degrees.
>
> Temperature affects a cell's fully charged voltage, and also its charge  
> efficiency. See the problem?
>
> In the short run, cell imbalance isn't a big deal. But over time, as you 
>  
> charge and discharge the battery, the differences get wider and wider.  
> Eventually the lowest cells can end up chronically undercharged. That 
> will  
> limit how much energy you can get from the battery, not just because of 
> the  
> cells' lower charge, but because chronic undercharging causes permanent  
> loss of battery capacity.
>
> You might think that the way to fix this is to charge every cell  
> individually. In fact, that's how many lithium EV batteries work. The 
> cells  
> are charged in series, as with any other battery, but each cell has its 
> own  
> bypass regulator. When the cell is full, the regulator diverts the 
> charging  
> current round the cell, so the charged cell can kick back while the rest 
> of  
> the cells finish charging.
>
> Most road EV owners with long strings of AGM or gel batteries use 
> similar  
> regulators. However, they can't put a regulator on each cell, because  
> modern lead batteries aren't built so you can access the individual 
> cells.  
> Thus they can only regulate the charge to each individual battery. 
> That's  
> better than nothing, but they still need to somehow balance the 
> individual  
> cells in each battery.
>
> Equalization (Charging Phase Three): Your charger fixes cell imbalance 
> with  
> equalization -- deliberately, but carefully, overcharging the battery. 
> The  
> fully charged cells dissipate the wasted energy through them as heat and 
> as  
> gassing, and the cells that aren't yet at 100% get topped off.
>
> To do this, instead of shutting off at the end of the constand voltage  
> absorption phase, the charger switches back to constant current 
> charging.  
> This time, it uses much lower current -- the same C20 / 50 that signaled 
>  
> the end of the absorption phase. Now our IU profile has become an IUI  
> profile. The charger holds that C20 / 50 current steady until the 
> voltage  
> rises to 2.5 VPC, temperature compensated.
>
> Or not; some engineers say to go to 2.55 VPC. Some say to hold C20 / 50 
> for  
> 2-4 hours, no matter how high the voltage goes. Some suggest constant  
> voltage float charging (2.3 VPC) with no limit instead, which is an IUU  
> profile. So as you can see, some opinion is involved here. If your 
> charger  
> has configurable equalization options, you might want to ask your 
> battery  
> manufacturer which one is best for their batteries.
>
> On the other hand, you might want to not to ask the manufacturer how 
> often  
> to equalize. Some of them -- US Battery is one -- will tell you to 
> equalize  
> on every single charge. That does give you the absolute maximum amount 
> of  
> stored energy, and thus the maximum range. However, overcharging 
> stresses a  
> battery, so too-frequent equalization is about as bad for your battery 
> as  
> too-infrequent equalization. My recommendation is to equalize only when  
> it's necessary.
>
> How often is that? Ah, there's the rub. Small differences in cell states 
> of  
> charge (SOC) can be hard to detect until they become big differences.  
> Unfortunately, although I know of one high quality (large, expensive)  
> industrial battery charger that keeps track and equalizes every 7 
> cycles,  
> most smart chargers aren't all that smart about equalization. Typically  
> they either don't equalize at all, or they equalize every time.
>
> If your charger is a never-equalizer, you might equalize your battery 
> every  
> 5 to 15 charges by restarting the charger after it's shut off. If yours 
> is  
> an always-equalizer, you could try to pull the plug on it when it gets 
> to  
> the equalization phase most of the time. The problem with these schemes 
> is  
> that now you're doing some manual charging. You paid good money for a 
> smart  
> charger so you wouldn't have to do that, no?
>
> Voltage-Based Charging Problems: Equalization strategy isn't the only  
> weakness in smart chargers. Straight IU and IUI chargers have another 
> one  
> that not many charger and battery makers own up to.
>
> A battery is a little like the water heater in your house. As your water 
>  
> heater ages, it starts to build up sediment in the bottom of the tank, 
> so  
> it holds less water. Well, as a battery ages, it builds up sediment too. 
>  
> This is not a joke; it really happens: the active material in the grids  
> crystalizes, falls off, and sinks to the bottom of the battery. With 
> less  
> active material in the grids, the battery's capacity to hold energy  
> declines. That also means that its fully-charged voltage declines.
>
> If your charger is programmed for a new battery's fully-charged voltage, 
> it  
> may overcharge an old battery. In fact, an old battery might never reach 
>  
> that magical 2.5 VPC above, so the equalization phase can go on too 
> long.  
> As the battery ages more, eventually it might not even reach 2.4 VPC. If 
>  
> that happens, the charger can get stuck in the bulk phase. Your battery  
> will get severely overcharged, aging it even faster.
>
> OTOH, another symptom of a battery in its golden years is that its 
> internal  
> resistance increases. This can cause the exact opposite problem -- the 
> on-
> charge voltage rises very fast, and that fools the charger into stopping 
>  
> the charge too early. Then the battery is undercharged.
>
> One way to help this situation is to add a safety time- or 
> amp-hour-limit  
> to your charger. I'll talk more about this later.
>
> DV/DT and DI/DT Charging: These are a more elegant solution to battery  
> aging. DV/DT and DI/DT stand for derivative of voltage (or current) with 
>  
> respect to time. If you took calculus in college, this probably brings 
> back  
> memories. You might remember that derivatives calculate the slope of a  
> curve at a given point. In this case, the curves are the rising voltage 
> and  
> falling current in a charge cycle.
>
> DV/DT charging takes advantage of the fact that as a battery charges at 
> a  
> regulated (constant) current, the voltage rise slows and eventually 
> stops,  
> regardless of voltage. DI/DT charging is based on the similar idea that 
> at  
> a constant voltage, the decrease in current slows and eventually stops.
>
> During the constant current bulk charging phase, in addition to watching 
>  
> for gassing voltage, the charger's brain watches for the voltage rise to 
>  
> slow down. A typical value to watch for is between 2.5mv and 5mv per 
> hour  
> per cell.
>
> During the constant voltage absorption phase, in addition to watching 
> for  
> the current to fall to C20/50, it watches for the current decrease to 
> slow  
> down. A typical value here is between 0.2 and 0.4 amps per hour.
>
> The battery makers usually specify DV/DT and DI/DT in hour increments 
> (if  
> they specify them at all). But IMO it's better to sample voltage or 
> current  
> more often than every hour. Also, the charger should look for the  
> specification (divided by samples per hour of course) to be met in 2 or 
> 3  
> consecutive samples, or for the delta (change) to fall to some much 
> smaller  
> amount. For example, Lester's Lestronic DV/DT chargers check the voltage 
>  
> slope every 15 minutes.
>
> Safety Limits: Whether the charger uses DV/DT or not, it should also 
> have  
> one or more backup methods that will halt the charge in case of really  
> weird or dangerous situations.
>
> One of the pesky qualities of lead batteries is that their fully charged 
>  
> voltage is lower at higher temperatures. This is called a negative  
> temperature coefficient. It explains why you should use temperature  
> compensation, but it's also a matter of safety.
>
> I mentioned above that once a battery charger goes beyond the battery's  
> gassing voltage at 80% charged, an increasing amount of the charging 
> energy  
> goes into heating the battery and generating hydrogen and oxygen. Well,  
> when the battery reaches 100% charged, all the energy goes to waste this 
>  
> way.
>
> It's the heat that causes trouble. As the battery gets hotter, its 
> voltage  
> falls. That makes a constant voltage charger send more current through 
> the  
> battery, which heats it up even more, which increases the current more 
> ...  
> and before you know it, you have thermal runaway.
>
> At best, the result is a hot, overcharged battery. At worst, the battery 
>  
> can actually catch fire. (Yes, this has happened, though I'm glad to 
> say,  
> not to me yet.)
>
> To prevent this, a smart charger should check for at least one of two  
> things. The first is negative DV/DT. If the on-charge voltage falls, the 
>  
> charger should stop the charge immediately. The second is high battery  
> temperature. If the charger's already using a temperature sensor to 
> carry  
> out temperature compensation, it should be able to keep an eye on this, 
> and  
> stop the charge if battery temperature exceeds something like 50° or 60° 
>  
> Celsius.
>
> If one of these conditions forces the charger to shut down, it's also a  
> good idea for it to let you know that something's gone wrong, maybe by  
> turning on a red warning light. That way, you don't find out the hard 
> way  
> that your EV isn't fully charged.
>
> Another good safety backup: checking whether the amount of charging so 
> far  
> makes sense. The charger should keep track of the total amp hours and/or 
>  
> charging time. If the charger knows what kind of battery it's charging,  
> it'll know if it exceeds, say, 150% of that battery's rated amp-hours. 
> If  
> it doesn't know, it can still make a guess at a reasonable amount. 
> Either  
> way, it should stop charging if things look odd, and warn you that  
> something might be wrong.  
>
>
>
>
>
> David Roden - Akron, Ohio, USA
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =  
> Note: mail sent to the "etpost" address will not reach me. To send  
> me a private message, please use the address shown at the bottom
> of this page :  http://www.evdl.org/help/
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>
>
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