Smartgauge w/ 3 batterys

[tml]

Doing my homework before purchasing a Balmar Smartgauge. Read several threads / reviews including Maine Sails excellent test results.
My setup which I assume is not uncommon is house bank #1, house bank #2, and a separate starting battery with its own switch. House bank #1 and #2 can be combined as both on the switch.
The Smartgauge installation guide connects to one bank for which it monitors / measures SOC (state of charge ) and a second bank which monitors voltage only. This makes sense for a two bank setup; one house and one start.
What is recommended for my situation? Monitor SOC continuously for House 1 and only voltage for house 2? In that case you don't know SOC for House 2.
Leaving House 1 and 2 combined as both would I suppose give SOC for the entire bank but that seems unwise for all sorts of reasons.
Advice much appreciated
TML

[Rusty123]

If you read more of MaineSail's stuff, as well as Nigel Calder and virtually every other marine electrical expert, I think you'll find that they all recommend a single house bank.

[ErikFinn]

Unwise for what sort of reasons exactly?
I'm in the camp to suggest combine the house bank to one single bank.. And Peukert gives you more usable capacity. Longer usable life from the bank due to less low depths of discharges.

[tml]

Separating the house banks gives redundancy. Accident or whatever can take one out and you still have a back up.
Not my area of expertise but have seen several opinions that charging batteries individually rather than combined is preferred. Using bat 1 on odd numbered days and bat 2 on even numbered days is a common recommendation.
TML

[Stu Jackson]

Originally Posted by tml

Separating the house banks gives redundancy. Accident or whatever can take one out and you still have a back up.
Not my area of expertise but have seen several opinions that charging batteries individually rather than combined is preferred. Using bat 1 on odd numbered days and bat 2 on even numbered days is a common recommendation.
TML

That's 1960-70 technology. Here's why:

Largest House Bank 101 (by Nigel Calder)

Calder battery sizing & stereo-battery connection

[john61ct]

Yes, one big bank is best.

A smaller "reserve" deep cycling bank can be used for cranking.

You need a separate SmartGauge per bank you want to monitor SoC.

[tml]

Thanks, get the bigger bank is better. The answer on the Smartgauge seems to be one gauge per battery bank for SOC.
TML

[ayates]

We run two house banks (2 x Trojan L16E-AC in each). The only reason for separate banks is to allow for isolation in the event of a battery (cell failure). This actually happened in recent memory on the ship, standard "deep cycle" batteries in that case, but it was enough to include redundancy when re-cabling for the new batteries. The battery banks are connected in parallel, via a battery switch, 100% of the time. So, other than a little longer cabling, and the resistance of the switch, they are essentially a single bank.

However, I also run a SmartGauge (in addition to a Victron BMV-702) and its instructions specifically indicate connection directly to the battery terminals and not through a switch. So I am really not sure if it is working correctly, as while I have it connected directly to one bank, it obviously connects to the other bank through a switch.


Allan.

[Exile]

Originally Posted by tml

My setup which I assume is not uncommon is house bank #1, house bank #2, and a separate starting battery with its own switch. House bank #1 and #2 can be combined as both on the switch.

I have a similar set up and have also been contemplating a Smartgauge. In my case I always leave the switch in the "ALL" position so my two house batts are treated as a single house bank. What I find confusing (to me anyway) is that the switch only affects the consumption/load(?) side, not the charging. The batt. charger hits both batts. no matter what, and I have a separate engine alt. that is dedicated to charging the house batts. only.

Not sure if this is how your system works as well, and it may not affect your question about installing the Smartgauge. I've just never been sure if there's anything unusual about my configuration or if I'm just confused . . . .

[john61ct]

Just makes no sense to me, in effect one large bank joined all the time, what is the point of a switch between the two sides?

I can see the SmartGauge getting confused by that sort of setup.

Make it one big Main bank, and if you want redundancy at that level a rarely used smaller Reserve. Usually kept isolated, except maybe when charging.

Allow essential/engine loads on the one hand, and auxiliary/house loads on the other, to be easily switched to one bank or the other.

And do so regularly for at least testing purposes.

A Smartgauge on each.

[a64pilot]

Originally Posted by john61ct

Just makes no sense to me, in effect one large bank joined all the time, what is the point of a switch between the two sides?

I can see the SmartGauge getting confused by that sort of setup.

Make it one big Main bank, and if you want redundancy at that level a rarely used smaller Reserve. Usually kept isolated, except maybe when charging.

Allow essential/engine loads on the one hand, and auxiliary/house loads on the other, to be easily switched to one bank or the other.

And do so regularly for at least testing purposes.

A Smartgauge on each.

I have two banks, joined with the switch to all. I have no separate starting bank. One is 440 AH, the other 220 AH, identical batteries, same age etc.
Reason to join with the switch is so that in the event of a single battery failure, the bank with the bad battery can be isolated.
The smart gauge works fine so long as you always leave switch to all.
Smart gauges are not cheap, and you don't need two

[john61ct]

I would still prefer my design, keeping them isolated, reserve bank hardly used, just cranking / testing.

Another good BM, AH-counting version is Victrom 702-BMV. Has the ability to "split" the bank, monitoring each half for an imbalance.

Likely would let you spot a bad cell long before catastrophic failure.

Just FYI

[Exile]

Originally Posted by a64pilot

I have two banks, joined with the switch to all. I have no separate starting bank. One is 440 AH, the other 220 AH, identical batteries, same age etc.
Reason to join with the switch is so that in the event of a single battery failure, the bank with the bad battery can be isolated.
The smart gauge works fine so long as you always leave switch to all.
Smart gauges are not cheap, and you don't need two

Helpful to know that the Smartgauge will monitor both batts. as long as they're combined into one bank by the switch. I imagine the installation shows how to run the wires for that scenario. Does your switch also serve to allow you to isolate which battery (or all) are getting charged by your batt. charger?

[sailcrazy]

Buy and use 2 Smarg Gages....on for the #1 house batt and the start batt, and the 2nd for the #2 house batt.. Combine them if/when you choose....or not. But you'd have a way of always determining the health of each of your batts. We're currently using 3 "house batts", each with an On/Off sw before they are combined on a busbar. We run an independent leg of the charger to each, and monitor each-plus an isolated "start" batt-with 2-Link 20 Batt Monitors. Old technology, and no longer available, but the same principle. If I ever detect one "house batt" going bad, its easy to ID and to isolate, without killing total DC power to the house. But...you'd have to buy 2 Smart Gages vs just one!

[john61ct]

To the extent the two banks are combined for extended periods other than while charging, both SmartGauges would get "confused".

If only joined by a VSR / ACR while charging, no problem.

Especially if a "SmartBank Advanced" was in control, may be able to get best of both worlds, I believe setpoints are adjustable.