[al]

Jerry, I am sure someone can answer your question, but I see a set up that is not factory original. I think to be on the safe side you may be forced to follow every cable until you find either a common ground, or likely from what I see, multiple grounds.

[George]

Looks like you’ll have to access the house battery ground from behind the batteries. Is the backside open for ventilation?

[al]

Tom, on my 98 CC the bottom of the battery bay had wire mesh covering an open bottom.

A suggestion, those three positive wire I see going to the inverters need to be shielded where they are touching the battery rack. Could start chafing and short out. I do see the fuses but still a possible source for a short.

Also slide the center control between the inverters out and look up in the ceiling above the right inverter and see if the ground is not on the coach frame.

[Jerry]

Thanks, those smaller red wires are going from the solar controllers to the batteries. Temporary installation. They are not chaffing on the battery rack. I will look up on the ceiling for the master ground in the morning. Thanks for the suggestion.

Jerry

[cal]

Yes, Tom, the back of that rack is open for venting. I don’t relish the thought of pulling out six of those heavy 8D AGMs after marking and taking loose all the cables just to find the master ground if I can help it. When I do the two house battery bank install as described in an earlier post then I will have to remove the 8Ds and redo the cables, but all I want to do right now is just add the large amp blue tooth shunt so I can map usage.

BTW, the earlier post about how to do this half AGM and half Li two house battery bank set up I failed to mention the need for a shut off switch between the large amp combiner and one of the two house battery banks. That is needed only if you have solar charging and are boondocking. Depending on the size of the solar array(s) the solar may put out enough to combine the two banks through the combiner, but not enough to offset the attempt the Li battery bank will make to bring the AGMs up to the same voltage, thereby depleting the Li bank unnecessarily. So, while boondocking you would wire one MPPT solar controller to each bank and turn off the shut off switch. Just be sure to turn it back on while driving, running the generator or on shore power so both banks will get recharged from any of those sources.

One of the major US Li battery manufacturers will offer a 255 amp Li battery in a 8D configuration later in 2020. It is out and being tested by OEMs now under their OEM marketing name. It likely will wind up being ideal for a 1 for 3 substitution for older AGMs since it is unlikely older AGMs still have anything close to the amp hour capacity they were rarted for when new.

This is one of the reasons I want to install the bluetooth shunt on my existing house bank. I know how these have been used since new and I can get a good handle on how much amp hour capacity they have lost over time. It will be nice if this dual house bank set up can allow us to get the benefits of Li in a true drop in replacement system with no special electronic controls other than a high amp combiner (and a shut off switch if solar charging is also desired).

Jerry

[Jeff]

Well, you are in luck. I have a 95 CC and all my batteries are out. Both grounds for bank a and b go to the top left and top right of the battery case, then right up here above the inverter on the right.

[Archived]

Jerry,

Relion already has 8D Lifepo4 in 200 or 300 amp capacity and there are 2 CC’s already converted by Jeff. Contact me for a price if interested.

[Archived]

Wonderful, that is exactly what I need. Thanks for the pics. We are leaving today for a run up the coast for a couple of weeks so this will come back on the front burner when I return.

Jerry

[Dick]

Jerry, you undoubtedly have done a lot of research on this but with nothing more than gut feel I cannot believe combining Li and AGM is a good thing.

I switched to Li earlier this year and they aren’t anywhere near AGM with respect to voltages or voltage range. I do not know what will occur if you merge Li batteries that operate at 13 plus volts and at 12.2 are near the point where their SOC is well under 30% and the voltage curve is in a near vertical drop off to the battery shut down point, where AGM operate at a 100% SOC at around 12.6 to 12.8 and are always in a slow fall to their dead state.

Or am I misunderstanding how you intend to use two distinctly different battery types? With AGM it is not even recommended you mix batteries with different ages so I don’t know how mixing with Li is going to work.

[Marshall]

Th key Jon is that Li and AGM they are never combined except when an external charge current is present. Under that condition the Li bank will not discharge trying to bring the AGM bank up to the same voltage. The Li bank will charge more quickly and the BMS will shut it off sending charge current only to the AGM bank. The presence of the AGM bank protects the alternator diodes from voltage spikes when the BMS shuts off charging to the Li bank without introducing any additional electronics. This moves us closer to true drop in replacement.

By using the Li bank for the heavy draw loads like running the refer and other appliances you get the benefits of the higher voltage regime of the Li and less voltage sag but you do not need to loose the remaining life in the AGMs as they only supply the lower amp draw circuits like LED lights and the like.

Overall one can gain the benefits of Li where needed (high amp draw circuits) without throwing away life still in the AGMs and can do so for half or less the investment of changing everything. Yes, this hybrid model seems to fly in the face of “conventional” wisdom, but so does simply taking out AGM batteries and expecting to be able to replacing them with Li in large capacity house battery banks without introducing a bunch of new electronic gizmos. Drop in replacement seems to work for small house battery banks of one to four 6vdc deep cycle lead acid batteries so long as you protect the alternator from the higher charge current the Li batteries will accept. It is in the large amp capacity house battery banks (the 6 to 8 8D or 4D lead acid batteries) that things get more complicated with respect to drop in replacement expectations.

My original articles touted full replacement but I got a bunch of push back from people asking for a lower investment way to get started replacing these larger banks on things like our bus conversions. I won’t be able to document the benefits and issues until I get a chance to try this hybrid model in the real world. May turn out to be a dud, may turn out to be a logical, less expensive way to make the transition from lead acid to Li. Only time will tell.

[terry]

If you have a single 50DN alternator the chassis batteries will handle the problem if the Li shuts down.

Unless something is wrong I do not understand how the BMS will shut down charging current if you have a dedicated house alternator. Inverters go to float, and an alternator, unless it has a high voltage output never puts a full charge in the house batteries.

Keep us posted because I think you are plowing new ground.

[Ed]

I am replacing my solar panels and Charge controller, 1992 Country Coach. My charge controller was mounted above the fridge, I can’t figure out where the battery wire terminates. Anyone have an early 90’s country coach? I have no documentation except for a 1995 CC manual. The controller has 3 wires, + from solar, + from Batteries, and ground. Wire shows Wire 106 goes from the batteries to the Charge controller. I don’t have 12v on this wire.

[glen]

Jerry can you explain what this “shunt” device will do for you?

[Rudy]

A shunt based battery monitor will measure very accurately the number of amp hours of capacity going into and out of a battery bank so you will always know the current state of charge. Very much like an accurate liquid tank sensor can tell you how much fuel is left in a tank. Voltage is a lousy way to measure remaining battery capacity. The shunt mounts between the battery bank negative terminal and all grounds.

Another article will appear in the next issue of Bus Conversion magazine that shows how you can easily establish two or more house Li battery banks. In my case I added 300 more amp hours of Li capacity to the 400 amp hours of Li I originally installed. The 300 ah bank now powers only the inverter/charger for the passenger side (where the residential refer is located on my coach) and the original 400 ah Li bank is connected only to the inverter/charger that powers the 120vac loads on the drivers side where the kitchen and AV systems are on my coach. The remaining 200 accessible ah of AGM lead acid batteries power only the 12vdc loads.

it all works like a charm and all three battery banks recharge automatically from the engine alternator while driving, from shore power while plugged in, from gen gen power while parked not plugged in or from solar while parked not plugged in with the gen gen not running. I use portable solar panels that rarely get deployed since there is so much Li available that we seldom are in a situation where they are needed.

in our coach the hot water heaters are powered only when plugged in or the gen is running or while driving via the heat exchangers. Water stays hot over night so we only need to run the gen to get hot water if parked off grid for two or more days. It sure is nice to be able to dry camp while going from point A to point B without even thinking about electrical needs.

I have yet to find a downside to this split battery bank approach. The BtoB chargers keep the lead acid and Li banks completely isolated one from another and by having two inverter/chargers and two Li banks for the 120vac loads you have built in redundancy in case something goes wrong with one or the other.

For this second 300 ah Li bank I used an 8D form factor 300 ah Li battery from Rebel Batteries in Texas. That company is owned by a disabled Navy vet and they warehouse in Texas and do all the warranty and customer support from Texas. They offer these apparently high quality 300 ah Li batteries for $1299 including shipping. I had them send me an open case unit so I could verify the internal build quality. All nicely done.

Jerry