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eltel72 avatar image
eltel72 asked

system help dual battery bank shared negative

my system originally for my motorhome conversion

1 solar array of 5 x 300w (3 panels in parallel and 2 in serial) linked via 1 to 5 split on each + and -. the solar cable +/- goto a solar on off switch which then goes to my mppt contoller

from mppt 10a 12v output is a 12v blade fuse board to my lights

mppt 12v output - positive to main + bus bar after battery bank connection pole (all + terminal cables from each battery, parallel 12v 120a/h lead sealled batteries x 4.

mppt negative to - bus bar after negative battery bank connection pole

from main bus bars these connections were added to a further set of bus bars as main electric cabling in cupboard other side of a wall via battery on / off positive switch

from secondary bus bars are 2 x 12v blade fuse boards (1 for permanent powered loads, cable to 12v 30amp fused water boiler tank (high powered relay switched) and cable to 12v / 230v 1500w inverter.

the above is a closed system not linked to vehicle electrics

i also had victron Cyrix Battery Combiner which i had installed to starter battery and solar battery by linking negative cables and positives via combiner.


I have now bought another bank of 12v 140a/h batteries x 3

again ive added in parallel to separate positive and negative connection poles.

From negative connection poles of both banks i have joined then to a joined bank connection pole


I found that there is a permanent drain on my starter battery so i have disconnected it from positive terminal. i have a small trickle charge solar panel to keep topped up and disconnected cyrix


i tried adding victron argodiode but the solar charger would not work? so i have now added to cyrix to battery bank b positive pole and bank a positive pole

this i am hoping will keep my bank b charged.


i am not sure whether i should put a fuse/shunt before or after main bus bar of secondary bus bar or both?

i would like to buy the victron battery monitor ( 1 for each bank ) and eventually for each battery in each bank, if possible, and ive upgraded my Chinese inverter to victron phoenix 12v 3000w smart inverter (yet to install). i probably will need buy victron ve direct dongle and i will upgrade my mppt but at a later date. and finally buy cerbo gx

is there an auto switch that could switch from bank a to bank b when bank a is low power and would this affect the cyrix? or would i have to use pole a on pole b on both off control switch for manual switchover?

and can i also add another cyrix for my starter battery instead of solar trickle charger or a battery to battery charger?? connections would be between battery and battery positive isolator switch which alternator lead connects to also. (as there is vehicle drain disconnected when parked up) and liked to battery negative terminal?

any help with any additional products on areas in my circuits that need changing?


also maybe add battery protect module? but where to add into system









Not sure - Admin please assign or create
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1 Answer
Justin Cook avatar image
Justin Cook answered ·

Hi, welcome to the Community! Please have a look at our Community Guidelines before posting; as the first guideline it will be noted that this really isn't the place for complex system design questions.

Such multifaceted and lengthy design questions are better directed toward your local dealer/distributor and/or an experienced, reputable systems installer in your area who can work with you to determine what you have, what you want, and what you'll need to get between those two points!

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