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Wiring & Installing A Battery Monitor

58K views 58 replies 24 participants last post by  freedoman 
#1 · (Edited)
The battery monitor is a very useful tool for a boat-owner who has to survive on battery power. When properly installed, calibrated and monitored they can extend the life of a battery bank especially when used smartly.

With new battery technologies costing three to ten times what wet cell technology does and many boaters moving to newer technologies such as Gel, AGM, TPPL and LiIon accurate monitoring of an expensive bank is almost a prerequisite.

People often ask me questions about how to install a battery monitor so I took some time and tried to make it simple. They are actually easy to install but there are a couple of "gotcha" traps that you may find your self falling victim to.. .

There are a fair number of monitors on the market. Blue Seas, Xantrex, BEP, Victron and a number of others make them. Currently the Victron units are the most simple to install and also the least expensive making them a good value. A Victron BMV-600S single bank monitor can be purchased for just $184.25. I chose to do this article with the Victron BMV-602S. I personally use a Xantrex Link Pro but they all do basically the same thing.


From left to right I have three generations of battery monitor represented. The original Link 10 was manufactured by Cruising Equipment Company and they really started a good thing. Despite many of the "LINK" products tending to be a little buggy they were generally well regarded and loved by boaters.

Somewhere along the way Cruising Equipment became Heart Interface and then Xantrex bought Heart Interface.

Xantrex then found TBS Electronics in the Netherlands and began importing and re-branding the TBS monitor as the Xantrex XBM (pictured in the middle). The XBM was the identical monitor to the Victron 501 and was a very, very reliable device. It also offered a computer interface option.

Eventually Xantrex made the switch to all TBS built battery monitors such as the current Link-Lite and Link-Pro. They have proven to be solid units.

About the time Xantrex signed on to re-label the TBS monitors Victron found a new manufacturer to build their units. The Victron BMV-602S is pictured on the right and bears little resemblance to the TBS built monitors.


The Victron shunt is quite unique because they have added a printed circuit board to it so that wiring is easier. Shunts are not really directional but because Victron added the printed circuit board / UTP cable connector it does make it directional.

The shunt is labeled -LOAD and -Battery. DO NOT wire this backwards or it will not work properly. The side labeled -BATTERY must be connected to the battery neg post and the side marked -LOAD must see the system negative loads.

This monitor is VERY easy to install. It has just two wires, a UTP cable & a power cable. The UTP cable is the only cable that needs to be run the monitor display and is literally "plug & play". The UTP cable is very similar to phone cable, only slightly more robust. The power supply wire simply connects to the positive battery post and the B1 terminal of the Shunt.

This shunt has two power supply inputs for two banks as it can monitor the voltage of a second reserve bank.


I tried to wire this up on the bench to replicate what one might see on-board a boat. This is explanation is just far to dificult to illustrate on a boat. I actually photographed this a while ago, on a boat, and decided not to use the photos.

Obviously the house bank would be multiple batteries but the point is the same and a single battery was used for illustrative purposes only. If your boat is not wired with a positive or negative distribution buss it can help organize the wiring tremendously.

I have also shown a Blue Seas double MRBF (marine rated battery fuse) block on the battery post. I use one for the house bank and one fuse for the alternator which I generally always wire direct to the house bank.


OK here's the gotcha we talked about. Nearly every instance of trouble shooting battery monitors I've come across can be lead directly to where you have connected your DC negative wires.

A shunt reads the loads on the system as measured across the shunt. This shunt is a 500 amp 50 millivolt shunt. This means that at 500 amps there will be a 50 mV drop across the shunt. Knowing this the monitor manufacturer can make the display correspond to any load from 0 to 500 amps or 0 to 50 Mv..

If any load, such as a bilge pump ground, is wired ahead of the shunt or on the -BATTERY side of it, it will NEVER be seen or measured by the monitor. All DC loads on-board should be read by the battery monitor. inverters, battery chargers, solar, wind, alternator, distribution panel, LPG detectors etc., etc., on and on.

Keep in mind that many marine alternators are case grounded and thus the system ground, which on most boats is the engine block, is the ground path for the alternator. While I much prefer an isolated ground for alternators most boats just do not have them. Due to this the ships main ground connection should be connected to the -LOAD side of the shunt and NOT ahead of it or on the -BATTERY side.

Anywhere you see a green arrow is safe to connect DC negative wires. The ONLY wire that should connect to the battery is a single negative jumper wire from the -BATTERY side of the shunt. No other wires should be connected on either the neg battery post or the -BATTERY side of the shunt.


In this photo I have a Guest battery charger connected to the system. The battery monitor is reading a positive +5.68 amp charging current as it should. Note the location of the black alligator clip in the next picture for a good example of why it really DOES matter where your negative system wires are connected.


The ONLY thing different in this photo is the location of the chargers negative lead. The charger is still putting out about 5.68 amps. Because it is on the wrong side of the shunt and it can not being seen or measured by the battery monitor. Don't "jump the shunt"...

Whether you are drawing a load or feeding the system a charge current the negative load wires MUST be on the load side of the shunt not the battery side.


I am a strong believer in over current protection or fusing of battery banks, even start banks on smaller axillary engines despite this not being a requirement to meet in ABYC E-11.

This product made by Blue Seas is called an MRBF or Marine Rated Battery Fuse. These fuses are meant to protect the wiring from dead shorts and are easy to install. I use the double version for the bank and the alternator wire. As always choose your fuses based on the wire gauge you are protecting.

Every positive wire connected to a batter should be fused within 7" of the battery or as close as you can get. This includes inverters, alternators, battery chargers, bilge pumps or stereo memory wires.

Interestingly enough the black fuse holder for this Victron battery monitor is 7" from the ring terminal for the battery post.


This is the back of the BMV-602S. There is a port for the computer connection kit, which can be purchased at additional cost, an alarm and the UTP cable connection port.


Once you have chosen you location, drilled the hole for the monitor and run the UTP cable simply plug it in to the socket. If you can plug in a fax machine you already know how to connect the monitor to the shunt. This could not be any easier. Kudos to Victron for making this so easy!


Now plug the UTP cable into the shunt.


Click, that's it!


This is a close up of the crimped pin for the power supply cable. I would leave well enough alone and not cut the wire shorter unless it is absolutely necessary. This pin fits nicely in the shunt socket.


Use a small flat bladed screw driver and simply slide the orange tab towards the shunt to open the clamping mechanism. In this photo I have not yet slid the orange tab towards the shunt.


With the tab slid backwards simply push the pin into place. It will slide all the way into the socket just about up to the plastic.


Here's a prime example of why I like the Victron simplicity. This is an older Link 10 and it requires five wires to be installed and then screwed down at the monitor end. This is certainly not difficult but requires some level of precision, access and can be a tad tedious.

The current Xantrex monitors, Link-Lite & Link-Pro, still connect exactly like the old Link 10 and on top of that they cost more money.


Rather than a shunt mounted PCB, like Victron has chosen, which offers true "plug and play" simplicity the Link series shunts still require wire stripping, crimping, and the physical need to manually wire the shunt. The blue & red wires from the previous photo, and not seen here on the shunt, go to the positive battery post with in-line fuses.

Again not difficult to wire but more tedious. I still have a Link-Pro on my own vessel and I am of the opinion that the Xantrex units are slightly better built but you certainly pay dearly for that quality, which may not even be necessary.

That being said if you don't need to monitor the voltage of a second bank, really not all that necessary if it is just a starting or reserve bank, then Victron also offers the BMV-600S for just $184.25.

Ideally unless you are taking a "resting voltage" reading of a secondary bank it really won't tell you much of anything close to accurate.


Battery monitors can display many different values on the screen including voltage, amp hours consumed, amperage, state of charge and more.

The "V" screen, as shown here, measures voltage for the house bank. This voltage reading is showing the battery being float charged.

This particular model, the Victron BMV-602S, can monitor the voltage of two banks as can the Xantrex Link-Pro.


The "VS" screen tells you the voltage of a second bank. Seeing as I used one battery for this illustration the meter is showing the same voltage as the the "V" screen.

I should mention that there has been one person on the net complain that the V & VS screens, even when fed from the same source voltage are not in sync. This meter happens to be properly calibrated but an experienced sailor and electrical engineer on SailboatOwners.com has had two units with voltage readings from .01 - .03 volts off when sensed from the identical source.

Is a variance of .01 to .03 volts a big deal? No, not at all, but I just wanted to make you aware so that you don't panic if your V & VS screens do not completely agree. Victron might need to do some better QC with the V & VS screen readings!


The "I" screen shows current in/out. This shot is showing no loads or charge current.


This "I" screen shot shows the monitor measuring a negative load. A negative load is denoted by the - symbol.


This screen shows a positive charge current as denoted by the lack of the - symbol..


This is the CE or Consumed Energy screen. It shows the amount of amp hours consumed from the battery. After the battery receives a full charge this readout resets to 0.0 Ah denoting a fully synchronized monitor.

If you draw a current of 10 amps for a period of 4 hours you will show -40 Ah on the CE screen.


This is the SOC or State-of-charge screen. This screen is the best way to monitor the SOC of the battery with this monitor. This screen is only useful provided you have programmed the monitor correctly, it's synchronizing the way it should and is wired properly. This readout calculates the amount of energy available in the battery and is Peukert & CEF / Charge Efficiency corrected. The screen ranges from 0% = dead to 100% = full.

Counting amp hours is good but may not always reflect the true state of charge of the battery. For example if the battery is drawn down heavily & at a high rate of discharge current you will get less usable Ah's than its rating. If drawn slower than the 20 hour rating you can get more Ah's out of it. The SOC screen corrects for the Peukert component and CEF, the Ah screen does not.

Please take the time to read the manual for these monitors as they are generally more difficult to program and master than the actual installation!
 
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#2 ·
Excellent write up. My only complaint is that you didn't do this 2 months ago when I installed my Victron!!! Since my install, four other boaters around me have purchased and installed the Victron units and all of us love the simple installation and the useful information provided.
 
#3 ·
I just did my bmv600 install this weekend, and it's already proving it's worth. Confirmed my long standing suspicion that my boat has a stray current or voltage leak somewhere...now Maine, how about a writeup to identify oem wiring issues :D
 
#4 ·
You may not. Check the manual for:

Ith: Current threshold. When the current measured falls below this value it will be considered as zero Amps. With this function it is possible to cancel out very small currents that can negatively affect long term state-of-charge readout in noisy environments. For example if an actual long term current is +0.05 A and due to injected noise or small offsets the battery monitor measures -0.05 A, in the long term the BMV can incorrectly indicate that the battery needs recharging. When in this case Ith is set to 0.1, the BMV calculates with 0.0 A so that errors are eliminated. A value of 0.0 disables this function.

Insert a DVM measuring mA and check to see that you really have phantom load. The easiest way to check Ith is to disconnect all the "loads" and see what the monitor reads when only connected to the battery with NOTHING else in the path other than the battery. If it is not reading zero wwhen only conencted to the battery, with nothing else conencted to the battery then it is an Ith/noise issue whcih can be adjusted out. This is a step you want to perform anyway...
 
#5 ·
Nicely done Maine Sail.
 
#7 ·
Congrats on a really nice job, Maine! This will certainly be helpful to lots of folks out there.

One note on fuses: the new terminal type fuses you illustrate are one of only three common types of fuses which have an Ampere Interrupt Capacity (AIC) high enough to meet present ABYC standards for positive wires connected directly to the battery. The other two are ANL and Class T. Most breakers in common use DO NOT meet these standards, though the new class of Blue Seas Systems breakers do.

Thanks again for a very nice job.

Bill
 
#8 ·
Bill,

As per our previous conversations the AIC issue is an important one. I often see circuit breakers connected to HUGE banks that have sub 3k AIC ratings and owners who know nothing about what the AIC rating even is..

I only use ANL, MRBF's or Class T when connecting to a battery bank. With new battery technologies like TPPL & LiIon we could very well exceed the Class T AIC rating at some point...;)
 
#9 ·
Maine Sail,

Once again you have made my life easier with one of your tutorials. Based on this latest one I have ordered the Victron 601 for my boat. I just finished a fairly major rewire of the batteries and main panel. Your post took away any aprehension that I had concerning installing a battery monitor.

Thank you!

Bill
 
#11 · (Edited)
Maine,

I've had the battery monitor on my list of things to buy soon. However, I now am the proud owner of a Xantrex MS2000 Pure Sine Wave Inverter/Charger and the Xantrex System Control Panel. (Sequitur kindly pointed out that things like a washing machine need a pure sine wave inverter to work.)



The MS2000 has a battery monitor built into it. Do I still need the Victron?

Here's the screen shot that has me wondering.


Secondly, since I now have both the SW2000 and a Freedom 20 inverter charger, and neither are installed, I could do some serious side-by-side tests. Not sure I have time to test every aspect, and I don't have all your meters. That said, is there any test that you'd like me to run, to compare them side-by-side?

I'll be selling the Freedom 20 soon, since the SM2100 was a good-sized boat-buck. Got a bit of buyer's remorse too. I'm hoping the SM2000 is simply fantastic and a worthwhile base to build upon.

Note to all: I thought I got a great deal until I saw the sailnet shop's price. Next time I'm checking here first.

Regards,
Brad
 
#13 ·
Maine Sail has, again, done a tremendous job. As you may know, he's posted this on many message boards. In most of those, I've linked to what I call "The Gotcha Factor" about the logic in the battery monitors algorithms. The default values in the monitors are set up for 200 ah house banks and certain charging voltages, which can be adjusted to suit YOUR boat's system. It especially comes into play if you have a fridge.

Please enjoy: Link-series Charging Algorithms -- The "Gotcha" Factor!
 
#14 ·
Why does the battery charger + connect directly to battery?

In your photo, why does the battery charger connect directly to the battery, instead of onto the far side of the battery switch? I've always seen battery chargers connected this way, but I've always wondered whether this is really the right way to do things. Does this change if it's a charger/inverter?

Actually, I guess that brings up a related question: where would other charger sources come into this configuration? So, solar panels, wind generator, the engine alternator: which should connect in front of the battery switch and which would connect behind the battery switch?

How does the placement of these sources affect the power monitoring?
 
#15 ·
In your photo, why does the battery charger connect directly to the battery, instead of onto the far side of the battery switch? I've always seen battery chargers connected this way, but I've always wondered whether this is really the right way to do things. Does this change if it's a charger/inverter?

Actually, I guess that brings up a related question: where would other charger sources come into this configuration? So, solar panels, wind generator, the engine alternator: which should connect in front of the battery switch and which would connect behind the battery switch?

How does the placement of these sources affect the power monitoring?
If your system is wired appropriately none of the charging sources need to be switched. They should all feed direct to the battery un-switched, wind, solar, alt & charger.
 
#20 ·
MS's great tutorial notwithstanding, I have a basic question re battery monitors in general, particularly the "state of charge" function, common to all brands I know of.
I understand (I think) that in order to ascertain how much charge is left in a battery bank...starting from a fully charged battery or bank, one must tell the monitor how big the battery was in the first place...similar to the way the gas gauge works in your car...if you didn't know how much gas the tank could hold, how would you determine when it was half full, for instance.
So suppose you had a house bank of 200 AH. That's the capacity of "the tank" you would program into the monitor and, as energy is consumed, SOC would diminish accordingly and all be well. But what if you decide somewhere along the way you wanted to switch another battery into (or out) of your bank via the 1-2-B switch.
I have a client who does just that. He has a two-battery house bank, a start battery, and an "at large" battery which can be dedicated (by switch) to either house or start function. He likes the sense of redundancy he says this configuration gives him. He makes his decision, where to put the orphan battery, based on the SOC he reads from his monitor.
He brought the boat in complaining that his batteries were unreliable...says his system works all the time that way and there's something wrong with his monitor and would I replace it...and his batteries.
Advice??

Howard Keiper
Berkeley
 
#21 ·
If monitoring a "bank" the bank should be one bank with no ability to switch batteries on or out. If you do you've just royally screwed up the calculations the monitor is doing and made it all but useless.

Your client would be MUCH better served to apply his "at large" batteries to the house bank 100% of the time, hard wired, without a switch.

However, and this is the big "BUT", as he is using them the batteries will all now be at odd stages of life. The house bank could have 200 cycles to 50% on them and the "at large" only 20 cycles. Permanently combining these is not necessarily the best idea as the good batteries will be out of balance with the used batteries. Banks shoudl ideally be of the same exact battery, purchased at the same time and of the same date code. I actually take it one step further and use my expensive battery analyzer to match CCA when I buy batteries. Just bought two banks for customers in the last week and went though 13 batteries to get 3 matched batteries and two matched batteries.

I also print out a receipt from my analyzer so we have a reference baseline and something to compare to in the future.

The easiest way to get the most life out of a bank is; the biggest bank possible at the lowest possible discharge levels.

Your customer is actually doing himself a big disservice by using "at will" batts and it shows his lack of understanding. He ideally needs to listen to you and let you be the expert but I have customers like that too and they eventually do listen after their "great idea" backfires..

Your customers monitor is not the problem your customer and his lack of understanding are causing the problem. You CAN NOT use a monitor accurately they way he is trying to..
 
#22 ·
Hi Maine Sail,
I realize I'm opening up a old thread, but my question is directly related. I have a brand new Linklite battery monitor that I have yet to install. I got it for a very low price, so low that I could probably sell it for what I paid for it. I do not have the connection kit.

So that being said, would you recommend selling the Linklite, and starting over with the Victron? Would it be that much easier to install?
Thanks,
J
 
#24 ·
Jos,

I personally like the Xantrex Monitors slightly better than the Victron if price is not the objective. I use a Link-Pro on my own boat and have a pile of monitors to use anytime I want including a Victron BMV-602. The Links are harder to install but the total added time is about 20 minutes and once your done that's it.

If you got it cheap then buy the communication kit. The proper wire for these is very difficult to source in small quantities. I have looked high and low. If someone has a source PLEASE let me know I'll buy a 1000 foot reel and re-sell it and still save people TONS of money..:D:D It needs to be multiple twisted pair. The "twisted" part is important as it cuts any induced noise which can throw the monitor off.

Like most things Xantrex doe not build these monitors they "source" them. The price of the TBS built Link-Lite and Link-Pro is OFFENSIVE when you include the communication kits. If you knew my cost on a Victron you'd have a better idea of just how offensive....

Both are good products but I do think the LINKS are more robustly built. I have never once had a single failure or issue with a TBS Electronics built LINK monitor and I can't say that for the older Cruising Equipment Link-10, 20, 2000 & 2000R. TBS began making monitors for Xantrex with the XBM and make the current LITE & PRO...
 
#42 · (Edited)
I'm getting ready to buy a Xantrex Linkpro and came across this thread while doing my research. I'm going to buy a 25' cat6 cable to use for $4.44 instead of their connection kit that costs $120+. What a joke!

Thanks for the great info--hope I was able to give something back!

Oh yeah here's a link to buy the cable: http://www.monoprice.com/products/p...=10232&cs_id=1023210&p_id=2315&seq=1&format=2

Jos,

I personally like the Xantrex Monitors slightly better than the Victron if price is not the objective. I use a Link-Pro on my own boat and have a pile of monitors to use anytime I want including a Victron BMV-602. The Links are harder to install but the total added time is about 20 minutes and once your done that's it.

If you got it cheap then buy the communication kit. The proper wire for these is very difficult to source in small quantities. I have looked high and low. If someone has a source PLEASE let me know I'll buy a 1000 foot reel and re-sell it and still save people TONS of money..:D:D It needs to be multiple twisted pair. The "twisted" part is important as it cuts any induced noise which can throw the monitor off.

Like most things Xantrex doe not build these monitors they "source" them. The price of the TBS built Link-Lite and Link-Pro is OFFENSIVE when you include the communication kits. If you knew my cost on a Victron you'd have a better idea of just how offensive....

Both are good products but I do think the LINKS are more robustly built. I have never once had a single failure or issue with a TBS Electronics built LINK monitor and I can't say that for the older Cruising Equipment Link-10, 20, 2000 & 2000R. TBS began making monitors for Xantrex with the XBM and make the current LITE & PRO...
 
#26 ·
Thanks for the info, as always.

I'll stick with the Linklite, and work on figuring out the install. The downside is that I'll be installing a battery charger, echo charger, galvanic isolator, additional battery, and battery monitor pretty much all at once. I suppose that's also the good news.

Thanks again,
J
 
#27 · (Edited)
Nice to start from scratch. I know your boat well and have WAAYYYYYY to many Saber 34 customers. Worked on one all day Friday and another one all day today....:D I think I am up to 5 Sabre 34's I work on, all Mark I's ........

This is a Victron Shunt and negative buss I installed on a S-34 MK1. This is the aft wall of the quarter berth battery compartment. Fairly straight forward job.. If you have not replaced you battery cables yet it is about time... I measured a .4V drop today from the alt to the batteries in only 7 total feet of 1 GA battery wire with just 22 amps flowing. That volt drop should have been more like .02-.03...

 
#32 ·
Brian to the rescue again! OK - so, I looked on the "Allowable Amperage of Current Carrying Conductors Under 50V as suggested by the ABYC " chart and for AWG2 it says 210 Outside and 178 Inside.

So - a Terminal Fuse Block with a 175 or 200 amp fuse should do it, right? Or am I still missing something.

Thanks

Rik
 
#31 ·
Our instruction manual for our Link 2000 (which, BTW, is working just fine after more than about five years - lucky me!) includes instructions for making up your own twisted wiring loom: put the wires together and chuck 'em in a drill chuck! Really. You can make your own.
 
#33 ·
Rik

I generally fuse somewhere in the middle between the expected load and the wire`s ampacity. Too low and you can get nuisance blows but you want the fuse to blow before the wire gets too warm.

But ANL fuses are different than other fuses. The 175 amp ANL will blow with a 290 amp load after 500 seconds. You don`t have to go too high.

Are you fusing the house bank or the start battery.
 
#34 · (Edited)
Rik,

A 200 amp ANL or MRBF should be sufficient. If by chance you do get a "nuisance blow" the ABYC allows for the ability to go to 150% of the ampacity ratings of the wire. That would be 315A for outside engine spaces and 267A for inside engine spaces for 2GA 105C wire. Never round your fuse size up to the next size when going over 100% always go to the closest size down.

Also check your wires temp rating. We've been discussing 105C wire but many older boats are wired with 90C or lower..

We start our 4 cylinder 44hp on a 225A ANL but with 2/0 UL1426 wire I do have the ability to go larger and still be under 100%..
 
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