Andina I don't understand what you are saying. If I have one battery that is 100% charged, then anything above the proper float voltage will overcharge it, won't it? If it is in parallel with another battery that is 50% discharged and connected to a multi-stage charger, won't the bulk and acceptance charge voltages exceed the float voltage? Wouldn't that overcharge the battery that started out at 100%? Jim Fidler "Fiddlesticks", confused? ---------------------------------------------------------------------------- ---- OOooo - that makes my electrolyte boil - its time that myth was put to sleep, and double shame on Calder if he did say that. This is one of the most common fairy tales I face on a daily basis. I should be directing my service calls to Calder to answer if he is responsible for creating this bloody mess. OK, pay attention. snip Andina Foster,

I really think that you guys should go to Andina's website and read what he has to say. Although I'll stick to using only identical batteries in parallel in a bank, I use a combiner and my shore powered charger will handle three separate banks. The starting "bank" is a single type 31 for a 4 cylinder, 240hp diesel. Other bank is two T105 Trojans bought from same lot, same day. Why do we get snagged on attempts to explain theoretically what is common sense? Combiners make sense if you lack a dual output alternator. External regulators make sense if you want to treat your batteries right underway. When I was safety chair of a 52 boat sailing club, I had a radio technician and his assistant check all VHF radios for output and SWR. With the exception of 2 bad radios, all problems on the other boats were due to poor voltage/current being delivered to the radio. Bad wiring and poor charging arrangements were prevalent. One fellow improved his current by stepping on the cabin sole! There are some true technical disagreements among true experts, but no one has suggested that combiners are bad, multiple output shore chargers and alternators are bad, nor that multistage regulators are bad. You pays your money and takes your choice. For those of you who can't support my view, do what my Father and his fishing friends on Long Island used to do - buy new 2 year warranty batteries every year. No problems mon. Ron Rogers

NO, Jim, it is no longer at 100% when you put them in parallel. When you put them in parallel, current flows from the fully charged one to the discharged one. The amount of this current is limited by the combiner to a safe level and it may cycle on and off for a period of time until the charge levels are equal. The combiner delivers a limited amount of amp-hours per minute until they equalize. The charge levels will equalize at some mid point that depends on the relative capacities of the batteries. >From then on battery to battery current ceases. And they share the incoming charge current so both remain at the same percentage of charge all the way up to fully charged. Andina Foster, tech@yandina.com > Andina > > I don't understand what you are saying. > > If I have one battery that is 100% charged, then anything above > the proper float voltage will overcharge it, won't it? > > If it is in parallel with another battery that is 50% discharged > and connected to a multi-stage charger, won't the bulk and > acceptance charge voltages exceed the float voltage? > > Wouldn't that overcharge the battery that started out at 100%? > > > Jim Fidler "Fiddlesticks", confused? >

Ron wrote: -----Original Message----- I really think that you guys should go to Andina's website and read what he has to say. Why do we get snagged on attempts to explain theoretically what is common sense? REPLY I did, a long time ago and again this evening. We get snagged with the real world suddenly smacks you from behind with a swift back hand. While working at Xantrex, I was tasked with looking into exactly this kind of problem. The dockside scuttlebutt had it that our chargers were boiling batteries. In theory it can't happen! - or can it? Turns out it can provided the user happens to do certain things and provided that the wiring is not according to the book and providing lady luck has taken a holiday. < grin > The point being Andina's answer on the website is correct - provided certain assumptions hold true. But they don' always. House banks are often depleted over several days between recharges. This causes an accumulation of sulfate which harden with time. The sulfate created at the beginning of the depletion cycle will be much harder to reverse than recently formed sulfate. A start battery by comparison is rarely deeply depleted and is immediately recharged fully when the engine runs. Sulfate causes the internal resistance of a battery to rise. Therefore a deeply discharged battery may have a low internal resistance except when it is also badly sulfated to the point it cannot easily be recharged. This now means the theoretical example given by Andina is disrupted by an unknown amount. By now we al know that charging many batteries in parallel often results in unequal charging. Charger manufacturers have for some time now recommended that you "equalize" the paralleled batteries to remove this sulfate so as to equalize the SG readings in the multiple cells wired in parallel. A combiner places several batteries in parallel. This is no different than wiring batteries in parallel and the same sort of result will come about over time. Regards Arild --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.516 / Virus Database: 313 - Release Date: 9/1/2003

Arild there are exceptions to most generalities. You can find situations where every thing presented on this subject may be debated. But I have to deal with hundreds of customers, who don't understand the fine ramifications you are describing and I certainly don't need to confuse them any more than they are. The facts I'm presenting will apply to MOST situations. > However in many systems; people - especially mechanics, who really do not > have a solid base in electrical theory, tend to use undersized wires which > causes a voltage drop in the conductor during the charging voltage. > As the voltage drop is proportional to current flow there is a voltage gradient > from source to final destination. > This gradient does not have to be very much only about half a volt, namely the > difference between 14.1 and 13.6 > Charger designers recognize this problems and some charger have remote sensing. > This means that the charger holds the voltage up until it sees the actual > sensed point reach the threshold point. > The majority of chargers, especially shore power charger, sense voltage at the charger terminals. Only fancy regulators made to work with obsolete diode isolators typically have an external sense. So your argument about resistances in the long runs to batteries doesn't affect 99.37% of the users out there. If the voltage at the charger is regulated to a safe level, you can only have LOWER voltages at the batteries and unless there is something wrong with the battery this won't overcharge it or gas it. The wiring resistances don't lower the level of charge reached because as the charging current drops to zero, so does the voltage drop along these leads drop to zero as you get to a full charge, although it might lengthen the charging time slightly. > Sulfate causes the internal resistance of a battery to rise. > Therefore a deeply discharged battery may have a low internal resistance except > when it is also badly sulfated to the point it cannot easily be recharged. > This now means the theoretical example given by Andina is disrupted by an > unknown amount. > True - batteries of different ages will have different characteristics but it works out nicely that as their capacity goes down with age, their internal resistance increases in proportion and they will still charge according to the supplied voltage when in parallel. There is little the average person can do about it anyhow so little is gained by second order factor analysis. If it is "badly sulfated to the point it cannot easily be recharged" then go get a new one. My theoretical example is disrupted by hundreds of obscure situations, including sinking. > > By now we al know that charging many batteries in parallel often results in > unequal charging. > Charger manufacturers have for some time now recommended that you "equalize" > the paralleled batteries to remove this sulfate so as to equalize the SG > readings in the multiple cells wired in parallel. > WAIT a minute here. The "unequal charging" of cells is due to the fact that the cells are in SERIES. It has nothing to do with the fact that they are in parallel. You even have to equalize individual batteries that have never been in parallel. When you "equalize" a battery you force all the cells in series to charge until they reach the gassing point so that they all have a maximum charge. Since each cell will have a slightly different capacity, charging to "full voltage" will leave some cells with "higher than full" and some with "lower than full" charge at the time when the total of all cells reaches the optimum. During equalizing you force excess current through the fully charged cells (causing them to gas) but that current is still charging the cells that had not reached a full charge until eventually they all gas. > Ron wrote: > -----Original Message----- > I really think that you guys should go to Andina's website and read what he > has to say. > Correction - "and read what she has to say." > A combiner places several batteries in parallel. > This is no different than wiring batteries in parallel and the same sort of > result will come about over time. > I agree - this is not really a discussion of combiners but the ramifications of charging in parallel irrespective of how they got that way. Andina Foster, tech@yandina.com