E-Trek Battery Monitor Install

[gregmchugh]

If you are going to the trouble of adding an equalizer why not just use the converter option instead and remove the 12v load tap on the battery bank? I guess there might be some added losses due to the converter in the system but you are also getting some losses from the balancer aren't you?

[booster]

Originally Posted by gregmchugh

If you are going to the trouble of adding an equalizer why not just use the converter option instead and remove the 12v load tap on the battery bank? I guess there might be some added losses due to the converter in the system but you are also getting some losses from the balancer aren't you?

That has always been what I have thought is should be, as it is easy and leaves the 24v system as only 24v. No good reason to do it other ways, I think.

[markopolo]

The 12v battery separator would likely have to go or be fed to 12v load line if permitted. No loss there if it has to go that I can think of.

[photolimo]

Originally Posted by Davydd

Silly question? I am assuming every Roadtrek E-Trek so far is still under warranty. Wouldn't this be something that should be worked out with them? If Roadtrek engineers are following I would hope they would get in touch with Photolimo. It would be in their interest to do so as speculation like this is damaging to their brand.

Yes, it is still under warranty so we are discussing with them possible solutions. Our inverter was replaced over a year ago and I asked for a battery monitoring solution then. I did not receive any substantial answers.

[photolimo]

Originally Posted by markopolo

1. What is the brand and model # of the battery equalizer in your E-trek?

It is a Cooper Bussmann 21060X00. Although I am not sure the amperage rating on the actual unit as it is installed in a difficult to view spot.

Originally Posted by markopolo

2. Is there (or was there) a wire from batteries C+ to G+ in your RV?

I double checked this and there is a wire connecting those two points. I missed this when I remade this diagram. There is a huge rats nest of gigantic wires making it difficult to see that one connector right in the middle of it all.

Here is the latest updated diagram. I added some more information like alternator/generator and the vehicle battery. I am not positive they are inserted correctly. If one did switch to a pure 24V system would you remove the 12V connection to the battery separator?
E-Trek Battery Layout (2).jpg

[photolimo]

Originally Posted by markopolo

This site: What Battery Equalizers Do | All About Lead Acid Batteries - looks to me to show that, in a 24v system such as yours, 12v loads are supplied through the battery equalizer.

Utilizing an equalizer that way would eliminate tapping in for 12v via a direct wire to the battery.

Using the equalizer to directly supply 12v loads is what these installation instructions show: http://www.cooperindustries.com/cont...ST_180156a.pdf

This was very helpful. Why would RT not install the equalizer like this? This would allow one to have two 24V banks which would seem better in many ways. No more balancing wires and full 24V double battery bank inverter runs.

[gregmchugh]

So there are cables between the two sides of the battery bank at 6, 12, and 18 volts? Is this a normal configuration for battery banks in larger RVs or other appications like fixed solar systems? Does this actually help keep the batteries in balance or help to isolate batteries that are degraded or some other type of function?

[booster]

Originally Posted by gregmchugh

Not relevant to this exactly but in an effort to get at least one of the 24v lithium battery Etreks working Roadtrek removed the 12v tap that supplies the 12v loads and replaced it with a 24v to 12v DC converter. Not sure that helped getting them working in any cases, did not work in that case, or what configuration they are now delivering with the 24v lithium sysytems.

This kept bouncing around in my head today (with all kind of other debris). If Roadtrek is using a center tap on a 24v lithium system to get their 12v, how in the world do they keep the cells balanced. It is bad enough on AGM, but from all we hear it is critical on lithium. If they did make it that way, it sure would be interesting to hear how they expected it to balance cells.

I guess that Roadtrek had one correct statement when they claimed nobody else made a system like their lithium system.

[booster]

Originally Posted by gregmchugh

So there are cables between the two sides of the battery bank at 6, 12, and 18 volts? Is this a normal configuration for battery banks in larger RVs or other appications like fixed solar systems? Does this actually help keep the batteries in balance or help to isolate batteries that are degraded or some other type of function?

I asked Lifeline about it a while ago when I was making the cables for our 4 battery setup, and they said all it really does is give you a better chance of having similar strength batteries at each voltage point, because you get the average of two. If the batteries were matched, as in all bought at the same time and same p/n, they didn't feel there would be any practical noticeable improvement in life or performance. Of course, it will never hurt anything either.

[gregmchugh]

Who knows what is inside the Ecotreks but I suppose they could be set up as 12v batteries with 200 & 400 amp hour capacities that have BMS including cell balancing internal to the physical module. These modules are then combined to make 800 & 1600 amp hour banks configured to 24v. But who knows, I have only seen an internal picture the smaller capacity modules. Posted that picture from one of the files posted by Roadtrek here awhile ago.

[gregmchugh]

Originally Posted by booster

I asked Lifeline about it a while ago when I was making the cables for our 4 battery setup, and they said all it really does is give you a better chance of having similar strength batteries at each voltage point, because you get the average of two. If the batteries were matched, as in all bought at the same time and same p/n, they didn't feel there would be any practical noticeable improvement in life or performance. Of course, it will never hurt anything either.

I just had never seen it done on larger RV battery banks, 8 AGM 12v setups for instance have no connection across the 6v batteries, so wondered why they might be doing it...

[markopolo]

Originally Posted by photolimo

This was very helpful. Why would RT not install the equalizer like this? This would allow one to have two 24V banks which would seem better in many ways. No more balancing wires and full 24V double battery bank inverter runs.

It really does look like a better solution.

Where does the positive 12v line to the fuse panel come from? (I see negative 12v in the schematic)

Are there any really large 12v loads? Fridge, pump, fan & lights could be handled easily by an equalizer. Does your etrek have instant hot water? Is that AC or DC? If DC is it 12v or 24v?

Is the solar 24v also?

[booster]

Originally Posted by photolimo

It is a Cooper Bussmann 21060X00. Although I am not sure the amperage rating on the actual unit as it is installed in a difficult to view spot.


I double checked this and there is a wire connecting those two points. I missed this when I remade this diagram. There is a huge rats nest of gigantic wires making it difficult to see that one connector right in the middle of it all.

Here is the latest updated diagram. I added some more information like alternator/generator and the vehicle battery. I am not positive they are inserted correctly. If one did switch to a pure 24V system would you remove the 12V connection to the battery separator?
Attachment 2947

I like the improved drawing, thanks.

One big question is why is there a battery separator at all? When the engine in running the 24v generator will charge all the coach batteries, so the 12v charge isn't needed. The only time it would ever do any good wood be to charge the starting battery off the 24v charger, and at that point it would mess up the charging balance by adding more on the 12v side of the bank. At best it should be a one way separator from the coach to the starting battery, never needed the other way.

I think we are back to using a pure 24v system and a 24 to 12 converter. That way the 24v shore charging systems could charge the coach and starter without balance issues. At that point, a one way separator or isolator would be all you need as the starter will be charged off the van alternator anyway.

[markopolo]

Straight 24v in a system with new batteries might be fine. Even long term. 4 batteries isn't really a long string.

The current problem of voltage imbalance in the series connected batteries in this etrek still exists. Link: http://www.classbforum.com/forums/f5...html#post35798

This site explains imbalance: Lee Hart's Minimalist Battery Regulators and provides a DIY solution.

This IC - LTC3305 - Lead Acid Battery Balancer - Linear Technology - balances up to Four 12V Lead Acid Batteries in Series. I wonder if it could be made to work in an E-trek?

You could try to charge the low batteries individually or a group in parallel on a 6 volt charger to see if brings them back to near full capacity.

[booster]

Originally Posted by markopolo

Straight 24v in a system with new batteries might be fine. Even long term. 4 batteries isn't really a long string.

The current problem of voltage imbalance in the series connected batteries in this etrek still exists. Link: http://www.classbforum.com/forums/f5...html#post35798

This site explains imbalance: Lee Hart's Minimalist Battery Regulators and provides a DIY solution.

This IC - LTC3305 - Lead Acid Battery Balancer - Linear Technology - balances up to Four 12V Lead Acid Batteries in Series. I wonder if it could be made to work in an E-trek?

You could try to charge the low batteries individually or a group in parallel on a 6 volt charger to see if brings them back to near full capacity.

The etrek at 24 volts is really a 4 battery string of 6 volt batteries, so I think you could use the 4 battery string balancer on it. You would need each "battery" in the string to be two 6v batteries in parallel. Not perfect, but way better than having eight batteries all on their own.

There is one thing that I think would need to be done in the diagrammed system for the etrek if you were going to go to 24v and wanted maximum balance in the wiring. The two front batteries are currently in series as the first two batteries in one of the 24v banks. The other bank has all the batteries together, so it will have considerably less resistance in charging and discharging so to less resistance, so the banks will be imbalanced. I think the thing to do would be to make those front batteries setup in parallel, and the with one of them on each of the two 24v strings. It would take two cables to them, one on each + from the third batteries of the strings, and then the negatives to ground. That way both banks would be seeing the same cable length and resistance so they would be much better balanced.

This could be done with the current system with the balancer, also, I think. A secondary benefit is that it would put both of the negative battery cables in the same spot so easy to mount a shunt in them.

[gregmchugh]

Seems like the idea of splitting the two front batteries between the two halves of the 24v bank is a good idea, does make a single shunt feasible for the whole bank. What gauge cables currently run from the front to the back for the 6 and 12v connections? same size I would hope...

[gsm]

Comments on AGM Battery layout in RT E-Trek

First post. Joined a couple of weeks ago, but I have followed this board for some years. I go by the name GSM or GerryM. I Own no RV of any type at this time. I have no connection with RT.

I was very interested when RT announced the AGM battery based E-Trek, followed by announcement of a Lithium battery based version. I planned to purchase one of these, but I wanted to see reviews by satisfied owners first.

Before long owners reported problems and RT became defensive and secretive about their designs. This prevented owners to analyze and help RT.
Gradually, in spite of RT, the veil is being raised on the problems.

Now to the meat of this post.

The configuration of Lithium battery based version is still deeply hidden in RT generated fog, but at least the AGM battery based configuration is being revealed by curios owners saddled with problems.

From the recently available schematics of the AGM battery wiring and the previously available photos of the physical layout of the hardware, it is abundantly clear that RT either ignored or was ignorant of the basic electrical engineering of battery systems.

To operate a string of two six volt batteries located in the normally hot environment under the hood, in parallel with a similar string of two six volt batteries situated in a much cooler environment at the rear of the coach, is a fundamental engineering error.

To exacerbate the situation by using battery cable-runs in excess of 20 feet between the two battery strings brings the engineering disaster to the next level.

The addition of the 20 foot plus bridging wire between the six-volt points of the two strings shows that someone totally unaware of all electrical principles played with this project at RT.

Beyond the above the two parallel battery strings use what appear to be different chassis grounds, again adding differing amounts of resistance to the two strings, only worsening the situation.

The idea of placing a coach battery under the hood is a highly questionable one. It Certainly will not result in maximum battery life. In this case the two strings of batteries will age very differently.

The most immediate problems is of course that the under-hood string will consistently overcharge and fail too quickly as a result, while the string in parallel at the rear of the coach will likely never be completely charged and fail from relatively rapid sulfation. In the meantime while the system limps along the parallel strings will in total be less charged and experience deeper discharge with each cycle, thereby also speeding failure. This means these four six-volt batteries will most certainly die first.

My caveat here is that I do not know the layout of the charging and discharging circuitry. Until RT finds the backbone to published this information, or owners take matters out of RT's hands i.e. trace (including module connections, wire sizes. Run-length, fuses, voltage and current measurements etc.). An Annual Class B Rally might be ea good opportunity to go nose to stern on an E-Trek. This would gather very necessary information.

In my opinion RT's claims regarding the proprietary nature of this ongoing disaster, and their efforts at stifling information flow to dealers and between owners, only makes their legal liability greater.

For two batteries now under the hood, RT should have found space at the rear where the other six batteries are located by either enlarging the main compartment or creating a compartment in the fender-area as was done by GWV and others. This is of course a major change that current owners with coaches still under warranty cannot be expected to undertake.

There is a partial solution that might even get the blessing of RT. It is not an ideal solution but will work much better than the current configuration.

- Essentially the re-configuration creates a 440 Amp-Hr six-volt block under the hood. Connecting the batteries in parallel makes sense since they both operate at the same temperature.

- In the rear battery compartment create another 440 Amp-Hr block by connecting in parallel with each other, the other two batteries of the former parallel strings. Again this makes sense since they operate at identical temperature.

- These two 440 Amp-Hr battery-blocks are connected in series via the existing two cables and fuses. They replace the 12 volt block of the original configuration. These two cable -runs in parallel offer the desirable lower resistance and hopefully much higher charging rate of the 24 Volt battery-system.

- NOTE: - I am not responsible for stupidity. Turn all main power off. If anyone attempts this be sure to open all wiring at the terminal-posts of all four six-volt batteries making up the original two parallel strings. For safety use temporary electrical-tape on all the cable ends. Check and Double Check every stage. These are not step for step instructions.

- The two 440 Amp-Hr six-volt blocks connected in series give 440 Amp-Hr at 12 volts. The remaining two 440 Amp-Hr six-volt blocks of the original configuration are re-connected to add the other 12 volts to the battery stack, again giving a 440 Amp-Hr, 24 volt system.

- Of course in making all the connections care must be taken that each of the eight six-volt batteries sees the same resistance at its terminals

- The proposed configuration ends up with one battery ground-point under the hood near the second alternator. (NOTE: - In my opinion, in this configuration, moving the battery-system's chassis-ground-point to the rear only adds to the needed wire-runs and unnecessarily adds resistance. Particularly for charging the battery-system from the high-current alternator,. it is in our interest to have the charging current to at least approach a multiple of four of the maximum discharge current.

In the rear of the coach add of a large electrolytic or similar capacitor, 0.1 Farad or greater at 35 to 50 Volt DC, between chassis-ground of the inverter/charger and the 24 Volt battery supply. This capacitor will filter spikes from the inverter and charger and potentially prevent false triggering of digital electronics.

- There should not be a battery-tap at the 12 volt point. This is what unbalances everything right at the outset. The application of a battery-balancer to correct this is outright nuts.

Use a 24 Volt to 12 volt converter to run the normal 12volt DC coach loads. As has be pointed out by others on this board this is the appropriate solution.
Measure the 12 volt current needed and be generous.

Only now does it make sense to connect a battery monitoring system. It will be in its simplest configuration.

Regards All

GerryM

[gregmchugh]

Clearly the temperature differences between the two battery locations is a significant issue in many ways. I have the standard two house batteries under the hood which is the normal Sprinter configuration for aux batteries. Roadtrek has never included a temp probe on the older Tripp-Lite charger even though that option is available so battery charging is far from optimal. Do they include the temp probe on the newer chargers? With the temp difference between the two battery locations you are going to get suboptimal charging on one set or the other even with a temp sensor, handier to put the sensor on the rear batterues close to the charger but you are going to have issues with the colder/hotter front batteries. Does the Balmer module on the aux alternator have a temp probe?

May also be handier on the reconfigured layout to put the shunt in the 24v end of the bank rather than run the signal cable up to the engine compartment where the negative ground is located.

[markopolo]

Trying to keep up with the ideas ............

Booster is this the basic idea?

AB parallel 6V
ACEF series 24V
BDGH series 24V
ACEF / BDGH parallel 24V

Welcome GerryM - that's a heck of a first post!

Is this a partial summary of your idea?

AB parallel 6V
CD parallel 6V
AB / CD series 12V
EF parallel 6V
GH parallel 6V
EF / GH series 12V
AB/CD EF/GH series 24V

[booster]

Originally Posted by gregmchugh

Clearly the temperature differences between the two battery locations is a significant issue in many ways. I have the standard two house batteries under the hood which is the normal Sprinter configuration for aux batteries. Roadtrek has never included a temp probe on the older Tripp-Lite charger even though that option is available so battery charging is far from optimal. Do they include the temp probe on the newer chargers? With the temp difference between the two battery locations you are going to get suboptimal charging on one set or the other even with a temp sensor, handier to put the sensor on the rear batterues close to the charger but you are going to have issues with the colder/hotter front batteries. Does the Balmer module on the aux alternator have a temp probe?

May also be handier on the reconfigured layout to put the shunt in the 24v end of the bank rather than run the signal cable up to the engine compartment where the negative ground is located.

All the shunt setups I have seen have to go on the ground end of the system, as the meters can't handle having battery voltage on them. The exception would be if you used a plain analog meter. You could reverse the positive and negative ends, but then you would need to get your power in and out from the front and that would be harder than running the monitor leads. Most of the monitors just need a Cat5 and the twisted shunt Calvin leads, sometimes with a +12v hot lead. Very easy to run.

There is another possibility that might work. Inpower makes an inductive pickup that can go in any voltage of line. They claim it can replace shunts in many cases. You would have to check with them to see if it can replace the shunt in a monitor like a Trimetric.