Author Topic: Panels layout and Batteries layout  (Read 401 times)


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Panels layout and Batteries layout
« on: March 17, 2022, 05:31:08 AM »
Hi all,

I read that the Solar Panels and Batteries layout should be the same ie. if panels in series then batteries in series and if panels in parallel then batteries in parallel.

Is that an essential or a recommendation. I ask because I have bought a motorhome (ex HINO BD186 Bus) which has a native 24V system. When I bought the bus there were 4 batteries interconnected in 24V layout and all 4 were being used as starter and house. I have separated the batteries to have a standard 2 x starter batteries (24V) layout.

Because the 4 batteries were all joined providing 24V, there are a number of 24V to 13.8V converters for DC stuff like lights, radio, water pump. The cabling is a bit difficult to trace so not sure whether or not to set up the house batteries in 24V config and power the converters from the "new" house batteries setup and leave the rest as is.

There is a 12V/24V fridge connected directly from the DC load on the Solar Charge Controller.

There is also a 240V Shore supply for Microwave, lights, TV, water pump etc.

I would prefer to completely redo it all but its too difficult without stripping the interior of the bus and isolate everything not part of the original electrics of the bus. A bit of a nightmare really.
1 x Classic 150; 8 x 100Ah AGM Deep Cycle batteries, 24V 400Ah configuration, Latronics 3000W inverter, 2 strings 3 x 260W Trina panels

Sandleton, South Australia


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Re: Panels layout and Batteries layout
« Reply #1 on: March 17, 2022, 10:55:45 AM »
Yes good idea to separate starting batteries from the ones used by loads.
Usually that would be the way it is done in that a starting battery is not a deep cycle battery.
I suggest you get an inexpensive DC clamp amp meter - some can be found for $30 to $50. It should be a help in diagnosing your system ( along with voltage too).
To begin you shouldn't have to worry about all the auxillary circuits - just the main connection where all the loads go to the 24v battery.
That is the point where you will charge with your solar charge controller. And that is where you would want to install a shunt on the negative lead of the battery . There will only be one connection going from one side of the shunt to the battery. On the other side of the shunt will all other negative wires. That way you can monitor every amp going into and out of the battery.
Not sure what kind of controller you have - both the Kid and the Classics have capability to monitor the SOC ( state of charge) of the batteries via a Whizbang installed on the shunt. That give you valuable information on what is going on ( how many amps your use and are charging at) . Many charge controllers might only tell you how many amps the controller makes in a day. 
Depending on your level of computer and electronics skill there is an inexpensive DC monitor option that costs under $20 - the Peacefair PZEM 017 . Keep in mind that device requires a 75 mv shunt compared to more typical 50mv shunt that the Whizbang uses.
I don't have time right now to go into the layout considerations of PV. 
Regarding the batteries - not sure what you plans or budget are but there are lithium battery options these days that are inexpensive compared to the past prices and should give much better performance than lead acid.
Depending on what kind of fridge you have - if it is one that usually runs on LP gas you don't want to run it on 12 or 24v because it will suck a ton of power compared to what you get for cooling. If it is a compressor type you are much better off.
You probably don't have to redo all your wiring - just keep the low voltage parts but figure out where the 24v to 12v converter is and replace that if it is not very efficient. You should be able to figure out where circuit are fed from by pulling fuses - hopefully there are fuses or breakers and if not you can add them. But if your electrical system was a DIY project and not done well you might be better off replacing some of the wiring.
I guess I would start by drawing out what you know - label the wire gauges and draw in any fusing or breakers.
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , Jakiper 48v LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batteries