E-Trek Battery Monitor Install

[booster]

Originally Posted by gregmchugh

I guess the basic question is that if larger RVs with 8 6v AGMs configured for 12v seem to work fine without any sort of balancing of the 6v batteries why would an 8 6v AGM etrek configured for 24v require balancing? Or is the issue that these other RVs are getting some reduced performance in terms of battery life, charging, capacity, etc. that balancing would mitigate?

I think it all boils down to the fact that any big bank could benefit from balancing, but is the cost, complexity worth it? The Roadtrek setup sucks in so many ways, that it will be worse than a block of 8 batteries in one place no matter what configuration you use. There are two batteries, 20 feet from the other, in an area that is generally much hotter, with no temp compensation anyway.

Lifeline says if you get your 6v batteries from them all out of the same production batch (they claim you can do that) they will match extremely closely, and should age at the same rate and stay matched. The 4 that we got do match well, although you can still see some variations as the charge and discharge. The do all come to exactly the same resting voltage to within 1/50 volt.

I don't think there is any RV out there that isn't getting reduced battery life and performance from their batteries, as none of the systems (that I have ever heard of) does all that it would take to optimize things. This may be the correct thing to do when you balance optimizing costs vs benefit in battery life and performance.

I didn't notice if anyone said how much parasitic the balancer cause? Significant?

[avanti]

Bluesea makes a "DC Shunt Shifter" that permits putting a shunt on the positive side:

https://www.bluesea.com/products/8242/DC_Shunt_Shifter

It is typically used when one wants to measure alternator output.

[booster]

Originally Posted by avanti

Bluesea makes a "DC Shunt Shifter" that permits putting a shunt on the positive side:

https://www.bluesea.com/products/8242/DC_Shunt_Shifter

It is typically used when one wants to measure alternator output.

I had to go back to my old notes to remember what was up with them, as I did look at the shifter. I think they have changed the spec callout a little since I talked to them about it, as the accuracy is much better now than it was. It appears to be that originally the just gave a % accuracy, so I called and asked what it was a % of, reading or full scale, as folks do stuff both ways. The tech said of full scale, so on a 500 amp meter that is a lot of error. They also strongly recommended against using on a different shunt or meter than theirs. Now it says % of reading, but only if on their, very spendy, meter. I was after good accuracy in the very low ranges of under 5 amps with 200 amp+ capability, so their accuracy didn't look good enough.

If it truly is a pure shifter, it should work on other meters and they imply that in the literature. Perhaps Bogart could comment on the if they had looked at them or not. If it worked, and the accuracy was reasonable, it might be a good solution, although having the shunt hot is a bit of a hassle as it also has to get air for cooling, limiting covering.

[gregmchugh]

I still think you can install a Bogart Trimetric with a shunt on the +24v end of the bank unless I am missing something about how it gets installed. I won't be surprised if I am wrong, I just don't see any issues based on the installation diagrams. That configuration is not shown but I don't see any issues with setting it up. I'm likely missing something...

[avanti]

You can also put the shunt on the positive side if you power the meter via a floating DC-DC power supply. The problem only occurs if you are trying to power the meter from the same battery that is being measured.

[booster]

Originally Posted by avanti

You can also put the shunt on the positive side if you power the meter via a floating DC-DC power supply. The problem only occurs if you are trying to power the meter from the same battery that is being measured.

Does that mean you would run the meter on whatever it normally would plus whatever voltage is on the shunt, so that there would a net of having negative being at whatever the shunt was at and rest of the meter at normal operating voltage above that just like if ground was zero.?

That would work, I imagine, as long as you were within the max unit voltage.

[markopolo]

How would a shunt on the positive side work if you're pulling 12v+ at the panel and 24v+ at the inverter. The charging source inputs (alternator, solar, inverter charger) might be in a few other places also.

[markopolo]

Page 10 of this pdf has me a bit puzzled: http://www.nyc-arecs.org/batt1.pdf

Would the cause of the voltage imbalance problem they mention be wire length? I just also see 24v at other points so am wondering why that (Figure 13) is the recommended way to connect the charger. Why is it optimal?

Assuming it is correct, in an etrek, which batteries would be the optimal 24v charging + & - connections to avoid the voltage imbalance they mention?

[markopolo]

Originally Posted by booster

I think it all boils down to the fact that any big bank could benefit from balancing, but is the cost, complexity worth it? ...................

This doesn't look like it would cost much:

http://camdenboss.com/media/category/files/ceq.pdf

[avanti]

Originally Posted by booster

Does that mean you would run the meter on whatever it normally would plus whatever voltage is on the shunt, so that there would a net of having negative being at whatever the shunt was at and rest of the meter at normal operating voltage above that just like if ground was zero.?

I'm not sure I follow the above. But, as I understand it, the problem with shunt-on-positive is simply that the design of most meters assume that the powering battery is the same as the one being measured. Because of this assumption, the designers of the meter tie together the ground of the meter power and the "low" side of the shunt. But, if you power the shunt using a floating source (either a dc-dc converter or another isolated battery), you can tie together the two circuits at any point you like, thus defining "ground" as you please. So, the negative side of the meter power source can be connected to the "low" side of the shunt, even if it is "positive" with respect to the measured circuit. The meter, of course, is merely measuring voltage drop across the shunt, so as long as it is being powered properly, all is well. The reason why analog meters work is simply that they aren't powered at all, so the issue doesn't arise.

[avanti]

Originally Posted by markopolo

This doesn't look like it would cost much:

http://camdenboss.com/media/category/files/ceq.pdf

Not as cheap as it looks:

https://octopart.com/ceq12a-camden+boss-24469553

[booster]

Originally Posted by avanti

I'm not sure I follow the above. But, as I understand it, the problem with shunt-on-positive is simply that the design of most meters assume that the powering battery is the same as the one being measured. Because of this assumption, the designers of the meter tie together the ground of the meter power and the "low" side of the shunt. But, if you power the shunt using a floating source (either a dc-dc converter or another isolated battery), you can tie together the two circuits at any point you like, thus defining "ground" as you please. So, the negative side of the meter power source can be connected to the "low" side of the shunt, even if is "positive" with respect to the measured circuit. The meter, of course, is merely measuring voltage drop across the shunt, so as long as it is being powered properly, all is well. The reason why analog meters work is simply that they aren't powered at all, so the issue doesn't arise.

Yeah, I think we are saying the same thing is different languages, basically floating the ground up to system in the meter.

I wonder if Bogart does something differently. I think they say they can do up to a 65v system, so that would be a lot of voltage on the shunt side.

[gregmchugh]

The Bogart Trimetric has separate power and shunt signal lines so I think there is a way to use it with a shunt on the +24v side assuming of course that there is no other load tap in the bank. 24 to 12 converter used to power the 12v loads.

[markopolo]

Originally Posted by avanti

Not as cheap as it looks:

https://octopart.com/ceq12a-camden+boss-24469553

Thanks for the pricing link. It's a lot more expensive than I thought when 7 (I think) would be needed to do the job in an etrek.

[gregmchugh]

I missed before that the balancers, Victron and this one, only activate during charging while the Cooper equalizer/converter is obviously always active even during discharge.

[markopolo]

Originally Posted by markopolo

Page 10 of this pdf has me a bit puzzled: http://www.nyc-arecs.org/batt1.pdf

Would the cause of the voltage imbalance problem they mention be wire length? I just also see 24v at other points so am wondering why that (Figure 13) is the recommended way to connect the charger. Why is it optimal?

Assuming it is correct, in an etrek, which batteries would be the optimal 24v charging + & - connections to avoid the voltage imbalance they mention?

I understand this a bit better now. Kirchhoff's circuit laws would apply. (KVL or KCL, not clear on which or both)

Basically, it's all about achieving balance.

There's some good info here: SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

[avanti]

Originally Posted by markopolo

Thanks for the pricing link. It's a lot more expensive than I thought when 7 (I think) would be needed to do the job in an etrek.

Yeah. In our quest for technically optimal solutions, we have to remember to also look at ROI. Sometimes it may be cheaper to accept slightly shorter battery lifetimes or capacities rather than to invest in the theoretically "perfect" system.

[avanti]

BTW: Does it make sense to periodically "rotate" the batteries if one has a less-than-optimal wiring setup?

[markopolo]

Would adding the 4 parallel wires drawn in yellow in the attached schematic cause any problems?

(attachment deleted, caused shorts)

I'm still stuck on trying to balance the voltages with minimal effort and cost and working within the confines of this system.

In this example I would leave the Cooper in place functioning as an equalizer. (not as a converter)

This example completely ignores trying to add a monitor to the system.

We need some input here. Maybe fresh eyes could check connection points with a virtual voltage meter. I'm not suggesting anyone do this before it is determined to be safe.

[markopolo]

Originally Posted by avanti

BTW: Does it make sense to periodically "rotate" the batteries if one has a less-than-optimal wiring setup?

We think alike: http://www.classbforum.com/forums/f5...html#post30000

It wouldn't be that easy in an etrek though - need a good plan.