By John Nixon, Otra Vez #728 (1988 wing keel)
Ed. Note: This piece was compiled from a series of Message Board essays that John Nixon wrote in late May 2008. While there is a weighty discussion of the characteristics of the Xantrex product line, you will find much in this applicable to any charger or charging situation. It's well worth the read, and be sure to read the companion piece by Michael MacLeod on his Xantrex XC3012 [installation] because he was the guy who started this whole discussion! The discussion began with a question about remaining plugged into shore power all the time, and the possible harmful effectst that might have on batteries due to excessive charging.
First, let me say that I am a mixed-bagger: I keep (for the last 20-ish years) AC power on the boat 24/7 to keep the beer cold, and to keep the inside temperature of the boat reasonable with my wonderful 16,000 btu of reverse cycle air-conditioning. Down here in north central Texas, the boats never leave the water, and our temperatures can change about 100 degrees F from February to August. We don't have to worry about salt induced corrosion up here, but I did the same thing while I had the Stamas 44 on the Texas gulf coast for 9 years by exercising reasonable preventative measures to prevent salt from causing potentially dangerous electrical hazards at the dock and on the boat. Having said that, the explanation for my veiled comment about not leaving the battery charger on 24/7 ( but not for the reason you might think ) is that I have no problem with AC power on all the time, but I have some technically sound reasons to not keep any kinds of deep cycle batteries on a charge 24/7.
All battery do not like having residual charge current flowing through their plates for extended periods of time. However, for our discussion here, I'll limit my comments in particular to deep cycle lead acid batteries. As Stu accurately quoted some of our direct correspondence, the problem created by continuous charge/residual current flow through lead acid batteries in positive grid corrosion. This is something that happens anyway during the charge process, but when the charge to float mode time ratio becomes mostly float mode, the grid corrosion continues to happen with no useful effect on the battery, so that the positive grid corrosion is highly accelerated. The grid corrosion produces increased internal impedance ( i.e. - reduced cranking capability ) and reduced deep cycle capacity from the loss of effectiveness of the positive plates. The relative reduction of capacity percentages I cited due to continuous charging versus cycle charging come from 2 primary sources: manufacturer's data, and my own empirical data from messing about with deep cycle batteries extensively since 2000. The primary manufacturer I have worked with is Concorde Battery, who manufactures not only the Lifeline AGM batteries, but also a complete line of aircraft and aerospace batteries in civil and military applications. The same family that owns Concorde Battery also owns Trojan Batteries, so the experience base there is pretty broad. Trojan was the premier manufacturer of submarine batteries during the diesel/electric submarine era. They are also still the leading manufacturer of golf cart batteries, among other batteries.
The stated 35 to 40% maximum reduction in useful life of a deep cycle lead acid battery due to continuous float charging was based upon Concorde's own testing and their experiences in field applications of their batteries in solar power applications ( the ultimate cycle charge environment ). My own customer experiences and the results of my own studies with the Lifeline batteries supports the stated range of useful life reduction with some reduced effect if the float voltage is temperature compensated and well regulated at the lower end of the allowable float voltage range. In the last several years, Concorde/Lifeline has reduced their recommended float voltage range from a nominal 13.4 volts to 13.2 volts, and this will further reduce the rate of positive grid deterioration in the float mode. In one of my own examples, the new AGM 4D batteries I installed on my Stamas 44 lived about 3.5 years in constant float mode at a temperature compensated 13.4 volt nominal. At the end of that time, the measured cranking power ( CCA ) and deep cycle capacity was reduced by about 20%. The next 1.5 years was spent using cycle charging, and the measured CCA and a-hr numbers were only about an additional 5% lower. I have to note that these examples are from premium grade AGM deep cycle batteries, and the results from a relatively inexpensive flooded battery would probably be significantly worse.
So, if 24/7 float charge is bad, what to do about 12 volt refrigeration ( i.e. - your Cold Machine )? The simple answer is to provide a suitable AC-to-DC power supply to run the fridge when you are at the dock, and then run it on the batteries when away from AC power. I have been doing this since 2002. There are a number of inexpensive and suitably reliable small switching power supplies out there that will do the task admirably.
One last quick comment: I like the TrueCharge + series because it has been an extremely reliable product with good features and performance at a fair price. I have never seen one fail at all in normal service in 8 years, and more importantly, never fail in a mode that produces an uncontrolled high output voltage across the batteries. This is in stark contrast to may of the other charges that were in use on boats over the same period of time. I think the TrueCharge II has excellent potential, but I want to see some in operation over time before I offer any additional opinion. I think the XC series is over-priced and touts primary features that offer little benefit in the real world.
Part 2: Xantrex charger review and associated comments
The actual comparison tabulation is attached Xantrex_Battery_Charger_Comparison_June_2008.pdf. 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.
Xantrex product summary
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.
Here are few random comments on various topics emerging in this discussion, in no particular order.
Xantrex Echo Charge Function If you are using the built-in function contained in the larger Freedom Series inverter/chargers, be advised that you do not want to use the Echo Charge function with any low internal discharge batteries: i.e. - any form of AGM or Gel battery technologies. The way the Echo output(s) receive their power internally in the Freedom unit causes high voltage spikes to propagate through the Echo output and can result in float voltages appearing across connected low loss batteries up to 16 volts. This will result in rapid degradation of the positive plates in the battery and seriously reduce the useful life of the batteries. I haven't specifically looked at the stand-alone Echo charge module in detail, but I have seen the same problems appear with them when used with a few older chargers and some alternators that had "dirty" outputs.
Link 10 Replacement The old Link 10 has been directly replaced by the new Link LITE, and with one or 2 features unavailable in the basic Link 10. Of particular interest, the Link LITE provides for the display of a second battery voltage on the internal display much like the Link 1000 provided. The accuracy of the Link LITE is comparable to the original Link 10, and I think retails for a little less than the Link 10. The Link PRO has all the features of the LITE but at higher internal accuracy for voltage and current measurements, and therefore all computed charging parameters are also more accurate. The PRO also offers a few features not available on the LITE, and the retail price is about 15 to 20% higher than the PRO depending where you buy it.
Truecharge2 I noticed that Xantrex has now dropped the ridiculous idea of having this charger available in 7 different output current levels. It is now produced in either 20 or 40 amps like it's predecessor. If you are using flooded cells, you will definitely be using the equalize function, and without the optional remote panel you will only be able to activate the equalize function from the control panel built into the charger, which means you will have to provide for physical access to that part of the charger unit. Unlike the remote panel option for the Truecharge+ series ( which was almost worthless ), the remote panel for the Truecharge2 will let you fully utilize/program any features available from the charger.
Microwave Ovens and Psuedo-Sine Wave Inverters With a large fully charged battery bank, a non-smart "psuedo-sine wave" ( i.e. bastardized square wave ) inverter will sort of work a microwave, but always at reduced power output. I have used one that way, and it was better than heating up the cabin in the summer with the regular stove or oven. As the battery voltage reduces, however, the microwave power starts to drop in a hurry and quickly becomes almost useless. If you want to use the microwave a lot and effectively, you will have to go with a smart true sine wave inverter that will allow the microwave to maintain it's normal peak power output over a larger battery output voltage level range. As an added bonus, the microwave and some fans and power tools won't "growl" at you as the battery voltage level drops.....
Xantrex XC Series Chargers In my on-going evaluation of this product, I have discovered some disturbing characteristics when used with low internal loss batteries ( AGM for sure, and maybe Gel ) that I have discussed with Xantrex personnel and am still awaiting their response to my disclosures and questions. I'll update my previous product review on Xantrex chargers once I have received a response from Xantrex. For now, I will caution everyone to only use the XC Series chargers with flooded cell batteries.