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+--- Thread: concern over battery banks (/showthread.php?tid=10630)
concern over battery banks - GregOConnor - 12-02-2015 16:07
I am redoing the house bank on my LXi and trying to make sense of the power path engineering. There now is not a way to shut off the house inverter supply 'so I think'. I did find a big marine style dial switch A-B-Both-Off but I see that only A enters and it carries all 6 of the oem Positive input. If you shut it off there is still current to the inverters and with the start batteries not enabled, I think the only path would then be via the detroit charging system. I fear this path would damage the detroit path so I removed the start batteries ( just took the neg cable off) prior to making house battery changes.
Way too many cables and I hope to eliminate redundant and unnecessary connections.
My concern is having a demand for power and a path that is undersized to carry that demand which then become a heating element.
RE: concern over battery banks - halkading - 12-03-2015 00:40
Greg,
My main AC power panel has two breakers to power inverters (only one inverter in my LX so one breaker doesn't do anything). Shut off the breaker and it kills the battery charger.
Question for you - do you have a odd looking round thing with cables hooked on each end near the marine style rotary switch (maybe a large diode)? One of the cables comes from the rotary switch and the aux battery contactor and the other side from the inverter. If it is a diode mine is shorted. I'm not at all sure what it is supposed to do. Any info will be appreciated.
RE: concern over battery banks - davidbrady - 12-03-2015 14:21
Hi Greg,
Normally BB used a 4 position battery cutoff switch similar to this Blue Sea switch, but BB only used it for a single battery bank so having the switch in position A is the same as having it in position BOTH, and OFF is the same as having it in position B. I think BB did this because at the time the four position was cheaper than the two position as pictured here.
The three shunts are for (1) alternator ammeter gauge, (2) coach loads, and (3) battery charge, which are the gauges on your dash and overhead. If the battery disconnect is wired properly then you can completely remove your house bank from the circuit. In this case the only way the chassis batteries will deliver power to the house or to the inverters is if the aux-bat switch is thrown. If that happens then you need to see what the gauge of wire is from the chassis batteries to the shunt and use the calculator at the bottom of this page to see if you're okay, keeping in mind your common amperage use and transients. The calculator shows a 3.5' run of 4/0 can sustain 1000A with only a 3% voltage drop.
You might find this charging circuit interesting. Unfortunately it's for a WB; I'm unable to find a similar diagram for the LXi.
Hal, that's a Class-T fuse in a rather unfortunate wrapper.
RE: concern over battery banks - GregOConnor - 12-04-2015 14:16
thanks David, I split the house banks to A and B on the BlueSea switch. A has 4 of 145 ah and B has 3 of 145 ah 12v batteries, this eliminated two post connections prior to the switch. I now have an empty top right tray where I will set my yamaha lp inverter. My confusion is the with the way these batteries get charged when the detroit is running.
with the Detroit BA alternator producing charge, it seems that both banks (House and Start) are being charge irregardless of the dash switch choice. the dash led lights up in my WB and LXi without making a toggle choice.
if, if, if,,,,
, ; the house bank was depleted prior to starting the bus.;The Inverter is on, ;Some appliance like the Air conditioner and Microwave makes a large demand for inverted power,
than,,,,,
??will the start batteries contribute power to the inverters
??is yes, what is the path,
??will the BA Detroit alt be suppling power directly to the inverter like the Yamaha does, Or does it go to the batteries first?
I have been charging my house batteries up all the way prior to starting the bus, in fear that demand path has been causing issues with V regulators, Detroit BA aLts and Inverters.
RE: concern over battery banks - davidbrady - 12-04-2015 15:32
Yes, the ignition switch 'on' also energizes the 'aux-bat' constant-use solenoid connecting the chassis batteries to the house batteries and allowing the 50DN to charge both banks.
Yes, as soon as the ignition switch is turned to accessories the house batteries will connect to the chassis batteries immediately pulling the chassis batteries voltage level down to that of the house batteries. When the engine starts the alternator takes over charging both banks.
It's good that at idle the alternator is only generating a fraction of it's rated output so we're probably not going to overwhelm the 200A constant use solenoid. It's bad that when the key is switched the chassis batteries dump lots of current into the house bank and in the process create an inrush which probably briefly overwhelms the solenoid - certainly creates a big-ass spark at the solenoid high amperage contacts.
In cases like this I always start my generator to get the 240A of BULK charging going to help bring the house batteries up before starting the engine. A complete solution would have some sort of differential voltage sensor and battery isolator isolating the two banks if their voltage deltas are extreme. BB tried to do this with the M450. You may find this thread interesting.
SpongeBob has two completely separate systems: an alternator and battery bank for the house, and an alternator and battery bank for the chassis. I do have a dash switch to temporarily connect them for the case of dead chassis batteries, but the solenoid is never energized automatically by the ignition switch.
RE: concern over battery banks - davidbrady - 12-05-2015 13:54
Hi Greg,
These Automatic Charging Relays provide a better solution. Blue Sea makes a bunch and I'm sure there are lots of manufacturers offering similar products.
RE: concern over battery banks - dentmac - 12-05-2015 14:39
Not wanting to hijack this ,I have started a new thread for the 450 battery separation.
RE: concern over battery banks - halkading - 12-06-2015 01:25
The chassis batteries on my LX 40 had a 1/2 amp draw with everything off so I decided to rewire the batteries to be able to shut them off independently. I have added two more perko switches to the existing one. One switch is for the two chassis batteries and two for the four coach batteries. I am able to shorten some of the cables with more direct routing and hopefully less voltage loss.
Discovered the coach batteries have no direct negative tie to the alternator or engine block for charging. It is apparently accomplished through a shunt in the inverter/charger. Inverter/charger instructions say not to connect the coach battery negative to the chassis, yet a few pages later a drawing shows both sets of battery negatives connected to the chassis ground system. What is correct for a 2003 LX 40? I do not have schematics showing coach battery and inverter wiring.
David, thanks for identifying the fuse for me.
RE: concern over battery banks - davidbrady - 12-06-2015 11:58
Greg,
Here's a Niehoff document that talks about the excessive load of AGM batteries and the availability of an alternator mounted thermal switch which can limit alternator current with heavy loads. I know my LXi lacked any thermal protection on it's 50DN, so I'd say owners routinely load their alternators beyond rated current capacity. How many times have you started your bus only to see the 50DN ammeter peg!
Hal,
The battery fuel gauge provided by your inverter depends on the ground shunt, so I think you want that house battery bank grounded at the inverter and thru the shunt. This way the inverter senses battery ampere-hour loads consumed thru inverting as well as those consumed by 12VDC loads, and it senses ampere-hour charging produced by the inverter's charger as well as those produced by the engine alternator.