Battery Charging Techniques

[Jon Schneider]

Ray Irvine had wored out a nifty solution many years ago. 

Yup, that sounds like what I was going to do, though I'm not quite sure I follow Ray's switching description.  I would love, though, to avoid the dedicated battery/separate-charging set-up if possible, and it sounds like John's found a way to do that. 

[Michael]

Jon - Regarding the new TrueCharge2 battery chargers from Xantrex, I talked with the local Battery Direct outlet in Burnaby (home also to Xantrex). They have a pre-production version of the TrueCharger2 on hand but don't know when production models of the TrueCharger2 line will be made available to them for sale.  Two other Xantrex dealers here did not have them yet, and the lady at the Xantrex Outlet Store knew nothing about them.  The Battery Direct fellow thought Xantrex was still working on them.

[Jon Schneider]

That's classic.  Xantrex is advertising the new line (Truecharge2) in print, but haven't told their distribution channel about it yet. 

[jmnpe]

Here we are again with installment #2, and the main topic here will be the AC-to-DC power supply usage with the Adler-Barbour Cold Machine.

First, a little background and history of the Adler-Barbour compressor. Prior to early 2000, all the compressors were fixed speed, brush commuted motors that had a very nasty current spike when the compressor started, but also were very electrically noisy while they were running. The installation manual for these units made a strong point of using big wire from the battery and the fact that you had to have a battery on the feed circuit to help "absorb" the current feedback of the motor back into the voltage source. Upon starting, the peak starting current was in the neighborhood of 17 amps for a couple of hundred milli-seconds. However, my discussions with the engineering folks back then ( pre-WAECO ) confirmed that with a reasonably "stiff" power supply ( i.e. - AC-to-DC power supply ) there was no reason that the compressor wouldn't be happy without a battery in the feed circuit. Of course, I had already tried it by then and knew that to be the case, but it made me feel better having them agree with me...... I used a 250w 12 volt nominal switching power supply with the output voltage set at about 13 volts, which meant that I had about 19 amps available. I used this from the end of 2002 with no problems on my Stamas 44, and the next owner is still using it. The power supply had a cooling fan that ran all the time, and the fan quit after about 3 years. However, since the run current of the compressor was only about 5 amps, the cooling fan wasn't really necessary anyway, and it wasn't an issue. However, the supplier of that power supply no longer carries or makes that power supply, so to duplicate what I did will require some adaptations ( at least at a reasonable price..... ).

For the post-2/2000 Cold Machines, the compressor was changed to a variable speed brushless motor in a slightly larger and more efficient compressor, the Danfoss BD50. The variable speed motor starts "softly", and the maximum start current is less than 10 amps. This means that a 150w power supply provides ample reserve to start the compressor, and really coasts along at the 4 to 5 amp run current. The motor also runs more electrically "quiet", which is a very good thing if you have other radio receivers on the boat. This is what I have now on Otra Vez.

For change-over from AC to DC power, I use a standard SPDT 30 amp automotive relay with the relay coil power by the AC power supply. The common terminal of the relay goes to the compressor, the NC contact of the relay goes to the DC feed circuit breaker, and the NO contact of the relay goes to the output of the AC power supply. If the AC power supply is powered up, the compressor runs from shore power; if not, it runs from the house battery bank. When I'm away from the boat with the charger turned off, I leave the fridge DC power turned off at the distribution panel: if shore power goes away, I don't want the batteries run down just to keep the beer and bottled water cold for a few days.......

The power supplies I have used on both the Stamas and the current C34 both came from www.mpja.com. The 150w power supply I use for the newer compressor is part number  16020 PS and costs $40.75. If you have an older compressor, you can use a pair of the same units in parallel after carefully setting the outputs to have equal voltages before tying the outputs together. If you want to pay more and have a better warranty, you can use part number 709-S150-12 from www.mouser.com at $57.96 each. I should note that the cheap units from MPJA have worked without a hick-up for 5 years and counting being turned on 24/7.

When I have the schematic diagram of the power change-over relay scanned into a suitable format, I'll post it here as well.

For installment #3, I'll summarize my comparison of the TrueCharge+, TrueCharge2, and XC series of chargers. We'll of course ignore the fact that the TrueCharge2 is currently still marketing blue sky.......

Until later.

John

[Jon Schneider]

Thanks John; this is really helpful, though I haven't quite followed it all yet.  Can't wait to see the diagram, if you get around to it.  BTW, I'm in marketing, so "marketing blue sky" is actually reality to some of us ;)  In fact, those of us in marketing actually think of it as engineering or manufacturing blue sky ;-0

[Craig Illman]

John - Thanks for the description. Now if I could just engineer a way to remotely close the lid and power the fridge up about four hours before I get to the boat so it would be cold when I get there.  And for the winter months, fire up the diesel heater a couple hours ahead of time......

Craig

[jmnpe]

As a follow up to Installment #2, here is the schematic ( attachment ) for the AC-DC change-over relay and power supply wiring for the AC power supply addition to your Cold Machine. After looking over my original notes on the subject, I determined that the original 250w power supply that I used with my older Cold Machine compressor ( pre-2000 vintage ) was rated as 12v/17a. I also noted that I had adjusted the output voltage up to about 13.2 volts for maximum efficiency for the compressor. The 17a current rating is a continuous rating, and this power supply easily handled the substantial starting load surge of the older compressor.

Based upon this information, there are actually 2 better options for power supply selection for the pre-2000 compressors. If you don't mind configuring a pair of units for parallel operation, you can use a pair of 100w units from www.mpja.com, part number PS1-100W-SF12 at $32.80 each. If you would rather have a single unit, use a 240W unit from www.jameco.com, part number 137649 at $106.85. This unit has a 2 year warranty and a cooling fan that only runs on demand, which in this application will be almost never.

Craig, if you add the AC power adaption to your fridge, it can be cold all the time if you have shore power available at the dock . I think I'll stay away from remote diesel heater starting............

John

[Michael]

John - Purchase of an XC3012 for Hali is on hold pending your comparison of the Xantrex battery chargers!  We are looking forward to your installment #3.

[jmnpe]

Installment #3: Xantrex charger review and associated comments.

The actual comparison tabulation is attached as a pdf file. I tried only to list the areas that could be meaningful in normal usage. There are other shared features with small technical differences, but I judged them not worthy of much discussion. All of them have various protection features for either the charger or the batteries, so there wasn't too much point in dissecting the small print.

If you scan across the product offerings, you will note that the Truecharge2 (when it ever is actually available...) is a poor substitute for the Truecharge+. If the offered price at WM holds, the Truecharge2-40 charger + BTS combo costs more than the equivalent price of it's namesake. Not only that, it offers a significant feature loss with the elimination of the 2 stage charge protocol option ( more on that later ). The only advantage that the "2" offers over the "+" is being about 5 inches shorter in length and about a half inch shorter in height. If that is not an issue, the "+" wins hands down.

After careful reading of the product information for the XC series, I can see a few things to like compared to the "+". The on board control/display panel insert is removable and can become a fully functional control / display panel, which I think is a nice improvement over the pretty dumb and way-too-big remote display-only panel offered with the "+". The XC also retains the option of either 3 or 2 stage charge protocols, with the addition of an improved float mode which, although not well described, appears to have the ability to function in a pseudo-inactive float mode after spending a reasonable amount of time in the active float mode. For the record, a full charge can only be achieved by either an active float mode charge ( constant regulated voltage at less than bulk ) for many hours, or at the absorption voltage for an extended period of time, or a charge at the absorption voltage until the actual battery charge current gets below a relatively low threshold. If the pseudo-inactive float mode works as implied, the 2 stage charge protocol becomes less important except for a few limited number of specialty cases.

The big advertising hype for the XC focuses on the ability to mix battery chemistries between the 3 banks. While this sounds good, in most practical applications is has little importance. A mix of flooded cells and AGM batteries can be done using only the AGM charge parameters. Not many people use true gel cells any more, and if they do, it's usually all gel cells because of the problems associates with single source charging from the main engine alternator. While it's true that the multiplexed or sequential charging of the 3 banks means that each battery will be presented with an optimal charge step series based upon the charge state of the particular battery bank, the down side of this scheme is that as you sit on your boat at night with the cabin lights on, there will be periodic and noticeable light intensity changes as your house bank goes from being on charge to off charge. In this scheme, only one battery bank at a time is actually under charge. [ Jon, can you comment on how noticeable this is in the real world?? ] Since on my boat my primary battery charger will be the Prosine 2.0 inverter/charger, I am pretty committed to single source charging at the dock or underway, and the equivalent of multi-source charging for my single house bank and dedicated starting battery ( all AGM ) is not a big issue.

If you spend long periods of time away from your boat, and you don't have "shore power phobia" , then the XC series offers an optimized solution to keeping all your batteries well cared for in your absence with the sequential/multiplexed charging and the pseudo-inactive float mode.

If you are only away from your boat for a less than a month at a time, either the "+" or the XC versions can keep your batteries and your boat safe in our absence. You can accomplish 90% of what the XC can do in this situation with the "+" by placing it in the 2 stage mode after you have fully charged your batteries before your departure. Any of the Xantrex chargers with the 2 stage mode available will automatically come out of the inactive state and initialize a new 2 stage recharge if any battery falls below 12.5 volts for more than 15 minutes. In addition, it will automatically initialize a new charge cycle every 21 days from the last recharge cycle, or upon a new application of AC power to the charger. Those of you who worry about your Mother Of All Bilge Pumps running for hours at a time in your absence can rest easy as long as you have shore power available.......

For those you still using flooded cells, the automatic full recharge cycle every 21 days is especially important to you if your are away from you boat for significant lengths of time. Flooded cells have one not well recognized problem associated with sitting with no charge or on a float charge for long periods of time: acid stratification. What this means is that when a flooded cell sits still for long periods of time, the acid separates into different levels within the cell based upon the specific gravity of the acid. The portion of the acid that has the highest specific gravity settles to the bottom of the cell, with decreasingly lighter acid in layers above the denser acid. If you recall basic lead acid battery chemistry, low specific gravity is associated with lower charge levels, and higher specific gravity ( within certain limits ) with higher states of charge. Once this happens, the average state of charge of the battery decreases because most of the plates are in contact with a non-optimal acid mix. This can produce a significant loss of usable capacity. The good news is that it can be easily corrected by bringing the cell voltage well above the gassing voltage ( i.e. – to the absorption voltage ) and producing lots of bubbles: the flow of the bubbles up through the cell plates causes the acid to remix and restore a homogeneous specific gravity throughout the cell. This action also replaces charge lost through internal self-discharge of the battery ( only when left off charge: it doesn't occur on float charge ), which with flooded cells can be as high as 20 to 30% of capacity per month. To make matters, the lead sulfate which forms because of self-discharge turns in the crystalline form more quickly than that which results from heavier discharge, and the crystalline form does not readily convert back into lead dioxide during normal recharging. Lead sulfate will turn into the crystalline form in about 45 to 60 days. Once your battery has lead sulfate in crystalline form, your battery has what will usually become a permanent capacity loss. This is what having your battery "all sulfated up" means. Most flooded cells need to be completely recharged every 30 to 45 days to avoid permanent sulfation.

OK: time for the BOTTOM LINE.

Truecharge 40+: Old but very good. Best feature set per amp of charge capacity. Can deliver first rate battery care in probably 90% of all applications. Has an exceptional field reliability history. Probably will get scarce once the Truecharge2 is available in large numbers. For now, Practical Sailor John gives it a "Best Buy" rating among the Xantrex selections.

Truecharge2-40: Newer than new ( not available currently ), "cute" with it's modern look and smaller size, and capable of handling most normal applications. Lack of 2 stage charge protocol makes it less able to deal with unique situations. It will likely be reliable after the bugs are worked out of it ( and there will be some.... ). I doubt that the small current steps between models will be maintained once the product is out in the real world: too many production and inventory variants, and no justification technically for less than about 2:1 steps in charging current between models.  I would buy a "+" now rather than wait on this one to become available.

XC3012/XC5012: I wanted to not like this series based upon price and what I initially considered to be some gimmicky features. However, after careful study, I have to revise my opinion. Yes, it costs more per amp than a near equivalent "+" unit, but it does have some features that offer the possibility of longer battery life in a more automatic, transparent manner than other Xantrex or other brand offerings. Also, the fixed/remote control/display panel included as part of the basic package is a plus in some applications; if you already have a battery monitor system that can tell you all you want to know about your batteries ( and why wouldn't you??? ), the remote display is not a big deal.  If the pseudo-inactive float mode works as indicated, that is a big factor in achieving true "plug-it-in-and-walk-away" battery care that has been unavailable in the consumer market up to now. Even though I need yet another battery charger like another hole in my head, I'm probably going to buy one just to put it through it's paces and see if it can realize the potential I think it may have. I won't say that I think you should go buy one, because I generally only do that based upon positive personal experience. You can buy one and experiment with me, or wait for my update in 6 months or so.

Well, I still have some battery and charging things on my list to pontificate about, but that will have to wait for Installment #4.

Hope this is useful.

John
 

[Jon Schneider]

John, I would say "useful" vastly understates the value of what you have written.  You should write for Practical Sailor (and thus up their standards). 

Regarding the light intensity change due to charging on/off input, I have not noticed this yet.  I will be aboard tonight at dock, so I will check, but the only on/off cycling I will experience is between low input in float mode to zero-input in float, because my starter bank is charged via a Duo Charge, so I'm not sure I'd ever experience the change you're forecasting (i.e., the house bank is always the charge target).  I can, however, report that the "pseudo inactive float mode" does indeed work as advertised.  When I return to the boat after being away during the week, the charger reads 0 amps charging.  It stays that way while I'm using minor amounts of electricity (stereo, occasional water pump, etc.)  For me, the combination of this no-fuss approach, along with the battery temp sensor (one supplied), and the digital read-out are worth the price.  If I ever get an electric windlass, I may also use it to directly charge what will surely be a separate AGM battery (versus my flooded house bank).  That said, I thought I would do the same with my current AGM starter battery, but I went with the Duo Charge method instead, and I may do that with a dedicated windlass battery as well. 

Thanks again for doing this.  It's truly the most superb and educational product comparison I've ever read.

[jmnpe]

Thanks for the editorial endorsement, Jon. Your check is in the mail......

You are correct about the lack of any "flickering" if you only have one battery connected to the XC. Under those conditions it would have "disqualified" the other 2 banks and would skip them in the sequential bank charge cycle, leaving only 1 battery in the "loop". You would never see any intensity change for all practical purposes under those conditions.

Thanks for the info.

John

The COMPLETE Charger Evaluation is here:  http://c34.org/bbs/index.php/topic,4352.0.html