Battery Monitor

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Battery Monitor

Postby RonBarr » Sun May 17, 2009 5:03 pm

We want to install a battery monitor on our F32. The Xantrex LinkLite looks good and handles two battery banks. Never installed one of these so given we have a starting battery and 2 house batteries in two separate banks but which can be joined together with the Guest switch "BOTH" setting - what happens to the monitor when one does this ---ie combining batteries witch - is it monitoring all three batteries at once? Thanks... Ron
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Re: Battery Monitor

Postby GeoffSchultz » Mon May 18, 2009 5:56 pm

I don't have one of these, but I'm sure that the amps in/out count will be thrown off. It assumes that each battery bank is independent and has no way to realize that they're combined. Thus if you drawing off of battery bank 1 and you combine the batteries using the Guest switch, the LinkLite won't know about the amps drawn from the starting battery nor will to know about the increased capacity of the combined batteries.

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Re: Battery Monitor

Postby Michel » Tue May 19, 2009 6:04 am

I've always had battery monitors with Ah in/out count. It's like Geoff says. Normally it's not necessary to monitor a starter battery because it's hardly depleted. And it's charged within the first few minutes when the alternator runs (I suppose you have the alternator connected to the starter battery).

You should also know that the Peukert formula to calculate degree of charge, is unreliable anyway. If the monitor is capable of keeping track of two banks (this means two shunts; one on each bank's minus) it will probably divide the charge and discharge current along the two banks when they are combined. But in a two bank system with a third battery for starting, you should design the installation so that combining is only necessary in emergencies. If you have other reasons to regularly combine the banks, what's the use of separate battery banks anyway? I did away with mine because I made too many mistakes with the 0-1-2-both switch. And deep-discharging one bank because you forget to switch in time to the other bank reduces the total life expectancy of the banks much more than discharging one double sized house bank to half the discharge.

I now have one house bank and one starter battery. the starter battery has just a volt meter, the house bank has a one battery monitor with Ah counter.
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Re: Battery Monitor

Postby GeoffSchultz » Tue May 19, 2009 6:22 am

I woke up this morning and realized that my reply was probably wrong as I don't know where the shunts are placed. If the shunts are between the battery and the combiner switch, you're probably OK.

I will also point out that on my 40/40, the way that Freedom designed the changing circuits, with feeds coming from both an inverter/charger and the alternator, that there isn't any good way to separate (monitor) the amps in/out from the batteries if you charge using both sources.

I also agree with Michael's point about why are you combining them? A starter battery is typically much smaller (although my 40/40 came with an 8D starting battery) and it should only be used for that purpose if you want to be sure that you'll be able to start your motor.

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Re: Battery Monitor

Postby RonBarr » Tue May 19, 2009 7:48 pm

My F32 set up has a single starting battery #1 on the Guest switch and two deep cycle (Walmart!!) house batteries on the Guest #2. After starting the engine one obviously needs to charge the starting battery albeit for a short time BUT one also needs to charge the house bank since it has also been used. So that's when I combine them by using the Guest BOTH switch. What other way do people do it? My trawler had a West combiner which simply kicked in and out based on the voltage high low-- about 11.5 and 14 V as I recall.

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Re: Battery Monitor

Postby Michel » Wed May 20, 2009 2:54 am

I have my alternator connected to the house bank. The alternator can deliver 80 Amps, which is a bit much for the starter battery hence the connection to the house bank of 350 Ah. Normally, I don't charge the starter battery with the alternator. The Xantrex Freedom 15 inverter/charger has a second smaller (max 15 Amps) charge circuit ('echo charge') in addition to the main charging circuit. This echo charge circuit charges the starter battery. However it is a voltage follower, so the house bank voltage is conclusive for the voltage supplied to the starter battery, which is not ideal.

When I'm away from the dock for longer times, I have a generator that feeds the Xantrex inverter/charger. Or I can manually connect the starter battery to the house bank via a solenoid combiner switch on the main panel. This switch does the same as your Guest main switch, only it has a red light warning me all the time that the batteries are combined. When using the anchor windlass, I also use this switch to combine the batteries so the windlass does not work on the starter battery only. I still have to change this so the windlass (and perhaps later the bow thruster if I install one) are fed by the more robust AGM house bank.
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Re: Battery Monitor

Postby GeoffSchultz » Wed May 20, 2009 5:57 am

I have a Xantrex PathMaker that automatically combines the batteries when the voltage reaches 13.2 V on either battery. This would mean that I'm charging the batteries from either the inverter/charger (which connects to the house batteries) or from the alternator (which connects to the starter battery.) When the voltage drops below 13.2 V, then the batteries are separated unless I both the battery combiner switch in "both."

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Re: Battery Monitor

Postby JimD » Wed May 20, 2009 12:52 pm

I have a very simple charging system. My house bank is either charged by the alternator or the inverter/charger. Then there is an echo charger that diverts up to a maximum of 15 amps to the starting battery. The echo charger is designed so that it won't over charge the starting battery. Had this system for years and works like a charm.

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Re: Battery Monitor

Postby THATBOATGUY » Thu May 21, 2009 6:53 pm

Thing is, you can combine up your banks during charging and they will each only take what they need. No need for anything fancy. This is not true of course if you mix battery types. But so long as you stay all lead acid you are fine.

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