Still in Design Stage

[vicwa20]

I just purchased a 2017 Tiffin Allegro Breeze 32 BR motorhome. It currently has a 1250 watt inverter to run its Whirlpool refrigerator and other outlets in the coach. The current battery system consists of two lead acid 6 volt batteries in series under the entry steps and two 6 volt lead acid batteries in series in the front of the coach. The 6 volt batteries in the front are separated and a battery sits on each side of the generator.

I am considering a 24 volt system by replacing each battery with a 12 volt lithium battery. Can the lithium batteries be separated in this same fashion? Not only is the front series separated for each other but the two series are also separated. Will the Victron Battery Balancer control any issues?

I hope to eventually have a 24 volt inverter/charger, a 12 volt to 24 volt B2B charger, and a 24 volt solar system. I realize I would need to convert back to 12 volts to power the motorhome.

Any advise would be appreciated. Thanks.

 

[MichaelK]

Unless you can provide a wiring diagram, that really is not a question easily answered. Do you see any kind of isolator switch inside the RV? Something labeled 1, 2, BOTH?

One way you could check to see if they are wired in parallel is to fully disconnect the cables leading into bank #1, and hot-wire bank #2 so that only one single 6V battery in in the circuit. If the disconnected cables leading to bank #1 are now 6V instead of 12V, then you know that they are wired in parallel.

 

[vicwa20]

The four 6 volt batteries are in two series to make two 12 volt batteries. One 12 volt battery (two 6 volt) is located under the entry steps. The other 12 volt battery (two 6 volt) is located at the front of the coach several feet away. The batteries under the step are right next to each other. The batteries in the front are separated by the diesel generator. In other words, the four 6 volt batteries are separated by varying distances and cable lengths and therefore have varying resistance between them. I don’t think that is an issue with lead acid batteries. I understand it is an issue with lithium batteries. One pair of lithium 12 volt batteries (new 24 volt) will be situated right next to each other and the connecting cables will be maybe 12 inches long. The other pair of lithium 12 volt batteries (2nd new 24 volt) will have the generator between them and the connecting cables will be maybe 60 inches long. Plus, the cables between the two new 24 volt series batteries will be about 8 feet long. All of this will result in varying resistance between the 12 volt lithium batteries and therefore varying load and usage. Would the Victron Battery Balancer control this situation or do I need to move all the batteries to a new location? Unfortunately, that is only my first question in many to come.

 

[Solarcabin Channel]

Did you purchase the RV from a dealer and is it under warranty?

If so I would check with them and get the schematics so you don't void your warranty.

You need to know what voltage the RV charger is working at and you may need to replace that to charge at the higher volts needed for LFP.

 

[Supervstech]

Different lengths between series batteries can be mitigated by using larger conductors on the longer wires, but generally, you want equal length between ALL batteries, and you want the sets equal length positive and negative between sets.
Also, on a parallel set, you want the positive load cable going to one set, and the negative load cable going to the other set.

 

[vicwa20]

I am planning on getting a 24v inverter/charger, a 24v solar system and a 12v to 24v B2B charger. First question is can I reuse the existing cabling in the motorhome that is between the current 6v batteries and for the 12v lithium batteries and create the varying resistance issue between the 12v lithium batteries? I realize the existing 12v house battery system will need reworked and eventually be reconnected to a 24v to 12v converter before power the coach.