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Old 01-10-2010, 21:43   #1
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Experience with Balmar Digital Duo ?

I need a solution for starting battery isolation, and I was considering the Balmar Digital Duo - does anyone have experience with this unit? I read in the manual that it draws half an amp while it is sleeping, that seems like a lot of load for doing nothing! It also says it has "programs" for different battery types (agm, gel, flooded) but does not say if they are multi-stage charge programs - does anyone know if this charger is able to top off a starting battery to a float charge? Seems like a big oversight for Balmar not to discuss the charging specifics...

I'm also open to other suggestions for smart battery isolation...
Thanks,
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Old 01-10-2010, 23:24   #2
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I have the Duo Charge used in conjunction with a Balmar MaxCharge regulator and am very happy with it. I only use it for charging from the alternator/regulator, I have a Mastervolt shore power charger (which I'm also very happy with) with one of the outputs to the start battery.

From what I can observe the duo charge senses when charging current is applied to the house bank, senses the charge state of the start battery, and supplies appropriate charging current. My start battery is relatively new and always nearly fully charged, so in my case it never applies more than a couple of amps. I should add that I just daysail and go out on several weekend trips over the course of a summer (we're in Michigan so the season isn't that long) so my batteries never really get discharged very deeply.

I have a hard time believing it actually draws 1/2 amp. I use a Blue Sea VSM 422 monitor, and when everything is off it only shows .1 amp draw which I asssume is the monitor itself.

Overall, I'm very happy with the both Balmar devices and would buy them again.
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Old 01-10-2010, 23:24   #3
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Not sure what your set up is. I have a manual switch that can combine house and starting batteries otherwise they are seperate. Then I have a blue seas combiner which isolates the batteries unless the charge is above I think 13 plus volts. Its worked without fail for 4 years now and is simple. Solar peaks up the house batteries then everything is combined until all banks reach full charge.
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Old 02-10-2010, 20:26   #4
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Thanks for the info and suggestions. What I don't understand is how the isolator knows when to
float" the starter battery? Sounds like it doesn't really do this in either case (the Balmar or the Blue Seas), it simply disconnects all charging current to the starter when the house batteries are no longer being charged. Of course, this also presents the opposite problem - when the house batteries require a long charge cycle to fill up then the starter battery will get overcharged, right?
I'm glad that you both have had good success with your isolators, I just am struggling with the theory of it before I decide which one to buy.
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Old 02-10-2010, 20:43   #5
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Thanks for the info and suggestions. What I don't understand is how the isolator knows when to
float" the starter battery?
An "isolator" is usually a diode based charge splitter than feeds two banks off one charge source. They incorporate blocking diodes to prevent current from one battery flowing into the other. The inherent problem with them is they can have rather high voltage drops and both batteries get the same charge parameters/voltage whether they need it or not.

A "combiner" is a device that automatically "combines" two banks into one large one when they are told to. These are large relays that do essentially the SAME thin you would if you flipped a 1/2/ALL/OFF switch to "ALL". Some, like the Blue Seas ACR and the Yandina combiners are smart and use a voltage sensing chip to combine and disconnect the banks automatically requiring you to do nothing but fire up the charger, solar or engine. Some combining replays are not as smart and use the ignition key or similar to combine the banks.

The Digital Duo Charger is neither a combiner nor an isolator. It is a DC to DC charger, as opposed to an AC to DC charger.
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Old 02-10-2010, 21:14   #6
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My understanding is that the Balmar Duo Gen ( and the similar Xantrex echo charge) are to some extent merely smart batteyr combiners. Ie they sense that the source battery is OK then connect the two so that the source battery "charges " the destination battery, once current falls below a set amount ( or terminal voltage rises, in Balmar I think) they disconnect.

These devices, like a simple combiner are very crude systems. There is no intelligent charging of the destination battery. Combiners are all very well but connecting a starter battery to a domestic set and then charging the domestic set always tends to overcharge the starter battery, Contary to the post above, paralleled batteries do not "equalise", yes their terminal voltage may be the same but the State of Charge is very different, Lead acid technology is such that the weaker battery will exhibit a similar terminal voltage but will remain undercharged. The bucket of water is not an appropriate analogy as the actual battery system is a way more complex model then that.

If you want a genuine DC DC battery charger with 4 stage intelligent charging of the starter battery try Sterling Power Sterling Power Products: Battery-to-Battery Charger Information There may be others out there too

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Old 03-10-2010, 06:04   #7
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My understanding is that the Balmar Duo Gen ( and the similar Xantrex echo charge) are to some extent merely smart batteyr combiners. Ie they sense that the source battery is OK then connect the two so that the source battery "charges " the destination battery, once current falls below a set amount ( or terminal voltage rises, in Balmar I think) they disconnect.

These devices, like a simple combiner are very crude systems. There is no intelligent charging of the destination battery. Combiners are all very well but connecting a starter battery to a domestic set and then charging the domestic set always tends to overcharge the starter battery, Contary to the post above, paralleled batteries do not "equalise", yes their terminal voltage may be the same but the State of Charge is very different, Lead acid technology is such that the weaker battery will exhibit a similar terminal voltage but will remain undercharged. The bucket of water is not an appropriate analogy as the actual battery system is a way more complex model then that.

If you want a genuine DC DC battery charger with 4 stage intelligent charging of the starter battery try Sterling Power Sterling Power Products: Battery-to-Battery Charger Information There may be others out there too

Dave
From Balmar:

When the Duo Charge senses charging voltage at the house battery, it works like a DC- to-DC battery charger, providing up to 30 amps of regulated charging current to support the starting battery.

The Duo Charge is designed specifically to enable its user to control charging voltage output -- making it possible to safely mix house and starting battery technologies. The Duo Charge features four different programs based on four battery technologies: Standard Flooded, Deep Cycle Flooded, Gel and AGM battery types. In addition, the Duo Charge can be programmed for 12-volt or 24-volt operation. When used with an optional Battery Temperature Sensor cable (MC-TS-B), the Duo Charge has the ability to respond to a battery over-temperature condition by automatically discontinuing charging output.





In multiple rather controlled bench experiments I have found just the opposite about combiners. The batteries after being combined and charged, test at the same level of charge after a 24 hour rest. I also confirmed with a hydrometer. The inventor of the voltage sensitive relay also strongly disagrees with the "over charging" theory of a start battery when using a combining relay...
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Old 03-10-2010, 08:50   #8
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I guess in the end what I want to confirm is that the Duo Charge really does use a smart charging program... The manual does say "The Duo Charge features four different programs based on four battery technologies: Standard Flooded, Deep Cycle Flooded, Gel and AGM battery types."
But what it doesn't say is whether it is a 3-stage program with a float stage. I just want to make sure the starter battery gets floated and not overcharged.
Thanks everyone.
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Old 03-10-2010, 10:26   #9
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I think both the duo-charge and the echo-charge are only one-stage chargers, but that stage IS the float stage. They're both current and voltage limited, so aren't really useful for charging a large battery bank. I've got an echo-charge on my starting battery, which is a cheap Sears auto battery. It makes me feel a bit silly to be protecting a $50 battery with $100+ unit, but the cheap battery has outlasted a set of house batteries so far.
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Old 03-10-2010, 10:47   #10
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The Xantrex EchoCharge (formerly Heart EchoCharge) is a voltage follower device which basically follows the charging regime of the batteries under charge. With a few exceptions.

1. It has a maximum capacity of 15 amps, more than enough for most cruising boat installations;

2. It is not programmable;

3. It will not overcharge your start battery;

4. It limits the voltage output even when the source voltage is very high, as in an equalizing charge.

For most folks with flooded or AGM batteries, this is the way to go, IMHO.

The DuoCharge is somewhat similar, but is programmable for different battery chemistries. And, of course, it has twice the capacity (30A) if that should be required (e.g., in installations which have high loads on their starting battery other than the starter itself). Like MainSail said, though, it has a design flaw in that it will shut down if a load of more than 30A is applied. And, it costs about twice as much as the EchoCharge.

Neither of these is a combiner. As MainSail explained, a combiner combines the attached batteries, just as if you manually switched them together. IMO, this is an inferior solution to the voltage-follower solution because, potentially, you could be combining (paralleling) a fully charged start battery with a much larger bank of deeply discharged batteries. Not a nice scenario.

Rhythmsmith: I suggest you go with an EchoCharge. It will handle things nicely and completely automatically. No switches to switch, no worrying about dragging down the start battery, etc.

Mine has worked flawlessly for the past six years, as have all those I've installed on customer's boats.

Hint: don't put it in the engine room. Heat will eventually shorten the life of just about any solid state device.

Bill
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Old 03-10-2010, 12:57   #11
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Neither of these is a combiner. As MainSail explained, a combiner combines the attached batteries, just as if you manually switched them together. IMO, this is an inferior solution to the voltage-follower solution because, potentially, you could be combining (paralleling) a fully charged start battery with a much larger bank of deeply discharged batteries. Not a nice scenario.

.

Bill

Bill makes a good point and one that is the reason I will not generally install a relay/combiner on Gels or AGM batteries. The high discharge and acceptance rates of these batteries can cause a very fast transfer of current between banks. On the bench I have seen a 100 amp AGM (Lifeline) take nearly all 90 amps of my charger for a considerable amount of time before the amps accepted began to taper off. The same 100 amp wet cell would only take about 20-25 amps from the 90 amp charger.

With wet cells the acceptance on banks of 150-300 amp hours can often limit the transfer of current from one battery bank to the other. I do know of one guy, a neighbor in his 70's, who was left dead in the water when he fired up the motor on the reserve battery after four days on the hook, which had killed the house bank. He & Jean let them charge at idle for about 10-15 minutes before heading out. He then proceeded to wrap a lobster pot buoy heading out of the cove, which killed the engine. When he tried to re-start, after diving on the tangle, both banks were now not strong enough to start the motor. While this is a very rare situation and I have only heard of or seen it once it can and could potentially happen again. Of course if you practice good battery management and don't deeply discharge your house bank then there is little issue. Bills combiner relay was "key on" which I really dislike as I prefer a low voltage disconnect.

Most of the combiners don't combine until the bank reaches about 13.2 volts anyway which means that the batts are not sitting at flat out dead when combined as it takes a while to increase the voltage from a point of flat dead to 13.2V.

With all that said my own boat had a West Marine/Yandina Combiner running on her for 2982 engine hours and many, many thousands of hours of solar charging, 5 1/2 years of solar charging, to be exact. The boat did a five year 24/7, 90% on the hook world cruise.

For the average coastal cruiser who does 100 engine hours per year or less that is nearly 30 years worth of engine charging time. 30 years!!!!! In that time the start batteries were never "over charged" and never took any more water than the house bank house bank did. They were also very comparable testing wise when measured with an EXP-800.

The first start battery & house bank was retired at the beginning of year seven after 5 1/2 years 24/7 use and nearly 2700 hours of engine run time, 27 coastal cruising years of alternator charging. It was only retired because a new bank was purchased.

The old bank was still perfectly fine and tested at about 85% of original stated capacity when measured with the Midtronics EXP-800 battery tester, a very expensive state of the art tester. The only reason for replacement was a re-configuration to a slightly larger bank and I did not want to mix ages.

I still use two of those batteries to this day in my barn for testing stuff and running a 12V stereo for music when working. The start battery is still going strong on my brothers Mako and is now over 10 years old. It regularly starts a 225 HP two stroke outboard though is admittedly finally starting to get weak and will soon need replacement.

When I re-wired the boat this past winter I stuck with a combiner because I already had one and it served me very, very, very well for the "charging equivalent" of roughly 30 years, if measured in coastal cruising time. I was going to go with an Echo but decided to save the money and use the Blue Seas ACR that I already had kicking around the shop. Would have used the nearly 3000+++++ hour Yandina but broke a mounting ear off it when I dropped it during the re-wire. It still works fine, though only has one mounting ear left.

If you have a very large wet cell bank or AGM or Gels then I would probably opt for an Echo or perhaps the Duo if you know you'll never need more than 30 amps of acceptance to the start/reserve battery. If you have a moderate wet cell bank a combiner can be a fine investment, and less money, that will work very well too..
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Old 03-10-2010, 20:39   #12
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I appreciate the detailed replies, it's great to learn from others' experience. I'm planning on a 400 A.H. house bank (SeaVolt or Lifeline AGMs). I was also planning on a smaller AGM for the starter/reserve. It sounds like I might be OK to go with an Echo Charge. What will happen if the starter wants more than 15 amps? Will the Echo blow a fuse? I know those AGMs can take a lot of charge current, but it sounds like you're telling me 15 amps will be "more than enough" to replace what is taken by engine cranking. Is this true even if the starter were drawn down low for some reason?
FYI my charge sources are:
Balmar 110amp alternator w/3-stage reg.
D400 wind gen
125Watt solar
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Old 03-10-2010, 21:17   #13
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What will happen if the starter wants more than 15 amps? Will the Echo blow a fuse?
It will be fine the Echo will just plod along putting out 15 amps if necessary and won't shut down like the Duo will. Do give it some air to breath though..
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Old 17-10-2010, 21:47   #14
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thanks for the recommendation

Quote:
Originally Posted by btrayfors View Post
Rhythmsmith: I suggest you go with an EchoCharge. It will handle things nicely and completely automatically. No switches to switch, no worrying about dragging down the start battery, etc.

Mine has worked flawlessly for the past six years, as have all those I've installed on customer's boats.

Hint: don't put it in the engine room. Heat will eventually shorten the life of just about any solid state device.

Bill
Thanks Bill, I did go with the Echo Charge in the end. What sold me is that it specifically states that it will "float" the starter and not overcharge it. I'm sure the Digital Duo would have done fine as well, but IMHO Balmar should add some words to their manual about "floating" the battery if indeed it does float. Thanks for the recommendation, it made my decision easier!
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Old 10-03-2011, 20:25   #15
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How to wire the battery switch(es) ?

I just started looking into the Echo Charge and Digital Duo Charge functionality.

Right now we have what are essentially two identical 200 Ah house banks wired through an off/1/all/2 battery selector switch. As far as I can tell (messy wiring to be traced and untangled) the switch controls both which battery bank is being charged (by the alternator) and which is being drained (by the house and the starter). I'm not sure how the shore power charger charges both with the switch in the off position, but it does and I'll worry about that later.

I want to take the two separate house banks and turn them into a single 400 Ah house bank (all batteries bought recently and are identical). Then I want to install a dedicated starter battery which is charged with the Echo Charger per the above discussion.

What I'm wondering about is how to use the off/1/all/2 battery switch in that case ? For the house I'd obviously want a switch so I can turn the house off. But for the starter I'd like to be able to use the off/1/all/2 option so if the starting battery suddenly dies I can start off the house bank.

So, will I need two switches ? One to just turn the house on and off, and the second to give the off/1/all/2 for just the starter ?

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