Two Battery Banks, One Trimetric

[BFL13]

This may be a useful idea for some, who knows?

I have two separate battery banks in the Class C, and want a Trimetric for each of them. But I only need one at a time. I already have one Trimetric. Costs too much money to get a second. Needs a work around.

I got a wiring kit for 4-pin towing and already had another 4-pin connector doing nothing. The Trimetric wire was miles long so I cut some off to use with the second set-up, and bought an extra 500a shunt for $35.

You guessed it! I cut off some wire coming out of the Trimetric display and added a 4- pin connector to that. Now I have the two wires one from each shunt. I put an opposite-end version of the 4-pin on each of the two wires from their shunts. I marked one of these for which battery bank it is from.

So now all I have to do is pick a battery bank and plug that one's 4-pin into the display's 4-pin. ( I do not use the Tri for history and all that--just as a voltmeter, ammeter, and AH counter.)

I only need the Tri for one of the banks (the AGM bank) for the ammeter when at home recharging the AGM bank to full. But then I really need it on those AGMs. (The AGMS are just for the inverter and I don't need the Tri on that bank while camping--the voltage shows on the inverter.)

When camping, I have the Tri on the main bank that runs the rest of the rig to use it as normal--AH counter, ammeter, voltmeter. In particular for doing 50-90 recharges to see when I am at 90 and can shut down the recharge.

So the Tri is left on the main bank most of the time, but I can swap over to check the AGM bank easily and don't need two displays.

The wire from the display goes down the wall under a metal cover so it looks neat, and all the ugly 4-pin stuff is under one of the dinette seats where the converter and water pump etc is hiding, so it is all out of sight, but easy to get at.

(I do know about the various eBay type monitors available, but this is how I chose to do it.) No idea if anybody else would do this, but there it is.

[MEXICOWANDERER]

Easier.....?

Clickity clickity click click click. No center off. Up or down.

https://www.ebay.com/itm/12-Pin-4PDT-Toggle-Switch-Red-Panel-Mount-Type-ON-ON-/301427366212

[brulaz]

Ah thanks, that makes sense.

Our usages are a bit different. The wife now expects to be able to work on her computer even when boondocking. Brings along a big screen just for that, but reluctantly agreed to forget the printer. So it seems the inverter is necessary.

And when in Florida over-winter it's more hot than cold, so we try to use the inverter to cook inside, rather than propane. When it's cold, we pretty much use propane for all cooking as the additional heat is appreciated. So less inverter use then, more furnace fan ...

Have a nifty campfire toaster that works well on the propane range, but usually just use a frying pan.

[BFL13]

No, I mean the SOC of the main bank can be run down below 50% with furnace use etc and you can still make toast with the inverter.

Also inverter use is optional ( stove top available, read a book instead of watch TV) but furnace is not so optional.

Voltage drop is wrt battery internal R so 12s do better than 6s and an AGM 12 beats a wet 12, but I am not claiming 200AH of AGM has lower R than 4 sixes at 450AH. Just that the two AGMs is enough for our inverter use between recharges and they stay above the 11v alarm.

[brulaz]

BFL13 wrote:
Now I have the two AGMs on inverter and four Wets on the rest (two T-1275s and two 6s).

BFL13 wrote:
An advantage to having the inverter on its own set of batteries is that can free it from the 11v low voltage alarm issue.

1. You can run the main battery bank down low if needed for some reason, but the inverter can still work on its set of batteries.

2. You can get away with the original thinner wire for the main bank to rig since it will only be doing ordinary size loads same as any RV has.

SO you are saying that you have less inverter V drop issues with two 12V AGMs (~200Ah total?) versus 4 6V FLA (~400Ah total?)?

I have heard that AGMs are better that way, but didn't realize they were THAT much better. I would have put the Inverter on the 400A FLA.

Also, its been my impression that our major increase in daily loads over the last few years has all been because of the DAM inverters (first a hand held, then 1000W and now 2000W). And now that the Microwave is in play, it will just get worst. A slippery slope, but I really have to do a more careful log of energy usage to be sure.

Anyway, that impression would also have me put the inverter on the 400Ah FLA bank.

[MEXICOWANDERER]

Inverters love to be properly fed. Tough to beat 2,000 CCA

[BFL13]

An advantage to having the inverter on its own set of batteries is that can free it from the 11v low voltage alarm issue.

1. You can run the main battery bank down low if needed for some reason, but the inverter can still work on its set of batteries.

2. You can get away with the original thinner wire for the main bank to rig since it will only be doing ordinary size loads same as any RV has.

[MEXICOWANDERER]

My $28.00 WIRELESS

Battery monitor purchased off eBay is still working great. Amps, volts, amp hours, kWh, high low set alarms for every individual function*. Alarms are relay outputs. Can trigger an ocean liner horn if a person wants - or a strobe.

*When alarming, display changes to alarm triggered event and flashes.

[time2roll]

BFL13 wrote:
I only need the Tri for one of the banks (the AGM bank) for the ammeter when at home recharging the AGM bank to full.

Why not just get an ammeter for the AGMs?

[landyacht318]

I have been in need of a new 4 wire connector, for my cruise control. I wound up using the molex connectors which come with PWM computer fans.

I sealed the ends where the wires enter with clear rtv. Been that way for 10+ years now, no issues.

I'd likely use Amazing Goop instead of clear rtv if I were to do it again today.

Nice solution to your needs.

I very much enjoy having multiple ammeters. My Sears clampmeter is suprisingly accurate at low currents. I bust it out to check the other ammeters or wattmeters incase they drift.

Most recently I used it on a '30 watt' woodburner which was running through a router speed controller. 0.22 amps was too hot, but 0.18 amps was perfect for what I was doing. On the 360 degree dial there was about a 3 degree difference from 0.22 to 0.18 so dialing in the heat via amperage was much easier and more precise.

Could not have done it withuot the clampmeter.

My point is, a ac/dc clampmeter is extremely useful, and in the states can be as low as 32$.

[BFL13]

I am just trying to set up the Class C so we can do as much off grid as with the 5er. I have a good collection of chargers and solar from before, so I can have two systems.

I can't combine my AGMs with the old Wets as one bank because the AGMs are inside too far away from the Wets outside, plus that would not be good for the newer AGMs if left banked with the old Wets very long. Some day I will have all AGMs in one bank doing it all, but this is now not then.

I have two different solar arrays each with its own controller, one on each bank. Same ones I had before with the 5er and TC. I have two converters, one on each bank for shore power.

I would re-charge each bank from the portable generator, using my 100 amp adjustable voltage PowerMax as a portable charger on the big bank, and the adjustable 55 amper on the AGMs (which is also their Float charger when on shore power.) I also have a Vector or two as spares.

I figure that the banks will not get down to 50% the same day, so it would be one at a time, but if needed I could do two at a time.

I did all this before in the 5er, only then I had the two T-1275s just on inverter and four 6s on the rest. Now I have the two AGMs on inverter and four Wets on the rest (two T-1275s and two 6s). Six batts is way overkill for summer when solar works, but is good in winter with no solar.

Only thing now is the Class C does not have the big open front bay like the 5er, so I can't get the Wets in where I can also get at them from above to check their water and do hydrometer work. These Wets are getting near to replacement, so that will be more AGMs simply because I would not need to get at them once tucked away. I can't do it with a battery tray either.

What's funny (or sad) is the rig came with a solar set that the original owner had installed in 1996. One 75w mono with 33 cells and an SC3/15 shunt controller. It appears to be wired down to the 12v connection at the back of the fridge to get at the battery bank. It cost him $771.40 at the time. (Sales slip still in the solar manual) I will leave that set there as it is not in the way and won't bother my solar.

[brulaz]

Operating two separate and different banks (AGM and FLA) simultaneously rather than sequentially is an interesting option.

In your simultaneous system, the AGM bank is dedicated to inverter loads only. From another thread you said there are two separate solar chargers. Will they each have separate panels as well so you can charge simultaneously rather than sequentially?

And will you run your generator sequentially and change the settings on a single charger each time you switch banks? Or do you have 2 separate 120VAC chargers, one set up for each bank with the generator charging both banks simultaneously?