12 volt freezers?

[Duane Dunn, Allegro]

I don't think I'd put the backup on the opposite side. When the combiner kicks in you may get a wierd current flow and not register the correct amps put back in. They specifically say ALL negative load conections on one side and ALL battery connections on the other. For what you are doing you really need the dual bank link 20 meter.

I've had my link 10 in two boats now for over 8 years and it is truely a great tool. So much so that I did away with all the silly multiple banks, combiner junk and switches. I just set up one large parallel bank. With the link 10 I always know the battery state and never have to worry about power. Plus this cuts in half the amount of discharge from each battery which will greatly increase their life. My cheapo dual purpose group 24 wet cells are still going strong after 4 years of use.

I almost added a third battery for our 3-1/2 week trip but decided to just keep a close eye on the power. The lowest we ever got was at the end of a 4 day period anchored out at an island park. We were down 26 amp hours. That's with 3 young boys on board, lots of lights, charging gameboys, watching DVD's on the laptop through the inverter. The mac is a simple boat with simple needs. Keep your power system simple as well.

ps- I do have one of those jump starters on board as a backup, plus I can hand start the Tohatsu as well as my backup 6hp dinghy motor on the transom bracket and lastly, I have sails. Boats have crossed the seas for centuries without power so I don't think a dead battery is that big of a deal.

[Moe]

Here's the schematic of how I recommend the wiring be, with the Link 10. It's very simple, and there are no weird things going to happen to the reading regardless of whether the combiner is open or closed. If you don't understand the current flow, let me know:



The shunt ONLY measures current going into and out of the primary batteries. That's why you set the Link 10 for 210AH.

--
Moe

[Jack O'Brien]

Thanks Guys.

I think I did it per Moe's schematic, but it's been a year and I forget. I'll check it. I haven't set-up the Link yet as I wanted to study the instructions better and I've been procrastinating. I also figured it only necessary, and cheaper, to use a single bank monitor as only the one bank would be "active". This was before I thought of the windlass.

If I ever get the windlass, and actually get it installed, I interpret the schematic as showing the windlass/backup battery use will not affect the Link in any way and the Link will correctly monitor only the house/motor bank. This is counting on the Combiner 50 not closing the circuit unless the charging side voltage is up to the 13.3V cut-in threshold. The windlass will be connected directly to the backup battery in the bow with fuse and relay.

Moe: What is the blue line on your schematic between the Link and the positive side?

[Tom Spohn]

When we purchased our new M we added an Indel B Travel Box. I believe it is of the same type as the Engle and others in that it uses a Danfoss condenser. I suspect (but don't know) that all Danfoss units will operate about the same. The max draw is when you start the unit up with warm food inside. After it cools down it draws very little current. We had no problems on 4 day cruises. We usually start ours off at the dock while still on shore power and while we are loading all the stuff into the boat so the max current drain hits the shore power and not the batteries.

BWY obtained a lot of these at very good prices if you would like to check them out in addition to the Engle and Waeco.

[Moe]

IIRC, the Link 10 has a blue fused voltage sense line. If, for example, the meter was located far away from the battery and the red power line was connected to a power cable far away from the battery, it would be important to connect the blue line directly to the battery so the voltage drop of the cable to the red line, which may be powering other things, wouldn't affect the reading.

--
Moe

[Bobby T.-26X #4767]

The Indel B Travel Box appears to be the same unit as the Isotherm 36.

I actually like the drawer concept although it is extremely small, but only uses .6 watts/hr.

http://www.e-marine-inc.com/products/re ... icr36.html

http://www.commercialproducts.net/tb36.html

[Tom Spohn]

The Indel and the Isotherm both use the Danfoss BD35F compressor, but the Indel is a bit smaller in capacity at 26 liters. (At least mine is)

[Duane Dunn, Allegro]

Moe,

On mine both those fused links to the positive side of the battery are just two wires in the same twisted pair cable that runs back to the batteries. There are the two power cables with fuses, a ground to the negative side, and two shunt sense leads that go to each side of the shunt. These are the two that must be twisted pair. I just used a chunk of Cat 5 twisted pair data cable for all the leads in the same sheath. Works great.

Xantrex sells special cable that puts it all in one sheath as well at two to three times the price. I'm sure at some long length the lighter cat 5 cable wouldn't work, but in our boats you can go end to end and around many times before the cable is to long.

[Moe]

Cat 5 cable should work fine. If you don't have any twisted pair, putting the ends of two wires in a drill chuck, having someone hold the other ends, and firing it up, will solve that problem quickly. I do this to all my power and ground runs when I'm wiring a boat, especially for the electronics.

--
Moe

[Dimitri-2000X-Tampa]

Cat 5 is neat stuff. Besides the normal phone and data usage, I wanted to put a rear center channel into my home theatre system but I had never wired for 6.1 only 5.1 (two rear channels). The area where the receiver is has no attic or wall access at all and I had to put the wires in when I built the room. Luckily, I had put in a cat5 cable though (for future Ethernet use) and so I used one side of the 4 twisted pairs for one speaker conductor and the other side of the 4 pairs for the other speaker conductor...basically turning 8 conductors into 2. It worked great...can't tell any difference from my "monster" speaker cables that run the other two rear channels...and these are 100 watt ceiling speakers (600 watt receiver). Cat5 saved me on that one. Although so far, I have only ever seen 1 or 2 DVD's that support 6.1 sound

Question about the link 10 and link 20:

I have the big red 1-2-both switch and two batteries. When I'm mostly powering around, I leave it in both. I only switch to 1 or 2 when I'm doing a very long sail or trying to conserve a battery at night, etc. Would it be a problem for me to use a link10 and it would just monitor 1 or the other or both? Afterall, if I'm in the both position, it is the same setup as Duanes. Sounds like it has a programmable setting for battery capacity so I suppose "percentage used" might be off if it is programmed incorrectly. But if it has amp hours used, wouldn't that be good enough?

Similarly, if I bought a link 20 and then stuck the switch in the "both" position, wouldn't that also mess up its preset data values or would it "know" that the switch was in the "both" position?

[mike]

Question about the link 10 and link 20:

I have the big red 1-2-both switch and two batteries. When I'm mostly powering around, I leave it in both. I only switch to 1 or 2 when I'm doing a very long sail or trying to conserve a battery at night, etc. Would it be a problem for me to use a link10 and it would just monitor 1 or the other or both? Afterall, if I'm in the both position, it is the same setup as Duanes. Sounds like it has a programmable setting for battery capacity so I suppose "percentage used" might be off if it is programmed incorrectly. But if it has amp hours used, wouldn't that be good enough?

Hmmmm.... if your batteries were permanently tied together as one bank, this wouldn't be a problem. But since they can be run independently, you could have a confusing situation, as you wouldn't know how many amp hours had been drawn out of each.

Similarly, if I bought a link 20 and then stuck the switch in the "both" position, wouldn't that also mess up its preset data values or would it "know" that the switch was in the "both" position?

It sounds like perhaps you have a similar battery setup to mine. I have a pair of identical AGMs... either of which can supply house power (but only one is wired to the motor for starting). A combiner allows simultaneous charging, though my 1-2-both-off switch could accomplish the same thing.

Anyway, it doesn't have to know what position the switch is in... it measures amps going in and out of each battery independently. A few examples...

1) If I've been running off one battery for most of the day, then connect to shorepower for charging, once the combiner joins the two, I can look at each battery and see how much charge its accepting. For instance, the charger's own indicator might show a total of 20 amps of charge rate, and when I toggle back and forth between the two batteries with the Link 20, I can see that the one that had been discharged is actually accepting the vast majority of the 20 amps, while the other one that was mostly full is just taking on an amp or two.

2) If, again, one battery is mostly discharged (60% discharged is my "dead" setting), and the other is mostly full, and I tie the two together with the "both" switch (not connected to a charger though), the Link 20 will show a hefty discharge rate on the full battery and a similar charge rate on the empty one. While there's no real practical purpose for this (I rarely, if ever use the both setting... I just let the combiner tie the two together for shorepower or motor charging), it's interesting to see the two batteries try to "equalize" themselves.


Now, given this, Duane's "one big bank" concept is superior in most respects, as this amp swapping between batteries probably loses quite a bit in the process, so if you are going to keep your batteries separate, keep this in mind.

But in my case, it's not as much of a concern, as mine are never tied together unless they're being charged. My rational for having two separate batteries is that I want to have one battery that is primarily the house battery, and another primarily for starting but that can be used for house loads if I need it. But at a certain point of discharge, I want to "set aside" the remaining power in this battery for starting purposes (my 1-2-both-off switch simply controls which battery is connected to the house bus).

This gives me a margin of comfort, but in hindsight, I'm not sure if it's really worth it. I feel better having my batteries separated, but on the other hand, having one big bank would eliminate the "hmmm... which battery should I pull from this evening" question, and would simplify the wiring a bit.

In short, if you want separate (but interconnectable) batteries, get the Link 20. Otherwise, parallel them and get the Link 10.

--Mike

[Duane Dunn, Allegro]

Mike,

The other thing you gain with the single bank, beside simplicity and cheaper components (link 10 vs 20, no combiner, no 1/both/2 switch, etc.) is longer life.

Say you normally pull 30 amps out of your house battery. This probably is about 1/3 of it's capacity. It will be able to tolerate this for a certain number of cycles. While you do this your starting battery sit's there with almost always a full charge contributing nothing to your daily needs.

Wire them in parallel as one bank and pull out the same 30 amps and you will only be going 1/6th into each batteries capacity. Discharging a battery only half as deep will nearly double the number of cycles it will provide before it gives up the ghost. Why pick on the poor house battery all the time.

For me this babying of the batteries has allowed me to use cheap 'dual purpose' batteries for the last 4 years without any perceptable decline in capacity. I've yet to find the need for expensive deep cycle ones although I wouldn't mind having AGM's for other reasons.

[Dimitri-2000X-Tampa]

Mike, thanks for the examples and explanation. I guess the conclusion would be that using either of the LinkX setups with the big red switch would still be somewhat useful (maybe just as an Amp meter with memory though), but I wouldn't get my complete money's worth of the device unless I made some changes to the configuration. It certainly sounds like a great gadget from everyone's accounts, but so far, I'm not doing enough long term boat camping to really justify it than more than as a fairly expensive toy. Ie, for day trips or single night trips like I have mostly been doing, I always have plenty of capacity (even with occasional microwave usage). Still, its on my list for one day and perhaps I'm leaning a bit towards Duane's simple setup. Btw, I currently have one group24 and one group27 battery. So far, the different sizes don't seem to be a problem. The smaller battery fills itself off the larger battery first if I use the both setting.

Which brings me to a question for Duane. Don't you have some sort of on-off switch for the whole bank? And if so, where is it wrt to the link10?

I know in my previous boat, the bilge pump and VHF were connected before the big switch so that even with it off, those two devices would still work. They had their own separate fuses and were connected directly to the batteries. I don't think its like this on my X, ie, everthing is connected after the master switch.

[mike]

Mike, thanks for the examples and explanation. I guess the conclusion would be that using either of the LinkX setups with the big red switch would still be somewhat useful (maybe just as an Amp meter with memory though), but I wouldn't get my complete money's worth of the device unless I made some changes to the configuration.

Not necessarily... I think your current configuration would be fine with the Link 20. The only catch is that the only thing that can be connected to each battery's negative terminal is the Link 20's shunt. The negative wires for everything else on the boat (such as the panel feed, and anything connected directly to the battery like a bilge pump) needs to connect to the shunt.

So far, the different sizes don't seem to be a problem. The smaller battery fills itself off the larger battery first if I use the both setting.

For what its worth, the experts strongly recommend against using different capacity batteries together in a bank... this "cross-feeding" action supposedly has a significant effect on efficiency. Actually, they suggest that you not only get batteries of identical capacity, but also of the same manufacturer, age, and, if at all possible, the same lot number. If I remember correctly, there was some sort of way to test two batteries to see if they'd make an optimal pair (if you REALLY want to get fancy about it). But for me, I simply got two identical batteries (though separated a few months in age). Then again, mine don't get tied together during discharge, so it's not that important.

--Mike

[Moe]

Duane's "always paralleled" batteries are used in almost every travel trailer and fifth-wheel large enough to have dual batteries from the factory, and there is rarely a problem with that configuration. The same should be true for a boat that isn't powered fast enough to pound in chop.

The more common failure of a _good_ battery, and even this is pretty rare, isn't a short, its an open, where one of the internal cell connectors fail. An open battery will have no effect on the one paralleled with it.

But in overall failures, including batteries used until failure, the most common failure is indeed the short, and that most commonly is a result of sulphation in an old battery flaking off and building up in the bottom of the cells. A shorted battery, even in only one cell (which brings the voltage down to about 10.5), will quickly drain the battery its paralleled with.

So if you're going to put all your eggs in one basket, my advice is to not try to stretch the life of the batteries (which may be someone's motive for this configuration), and change them out more frequently.

The best reason for running two batteries in parallel is for use with an inverter, where they cut the much higher amp draw in half, and that has a significant benefit on charge life, due to the Peukert Effect.

I personally prefer having two dual-purpose deep cycles that I can alternate between starting and house uses, but always having one designated as the starting battery.

--
Moe