Discussions about solar, wind and radiant energy. Electronics and projects dealing with energy savings.
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Location: Illinois


Post by tazmanddevil67 » Sun Nov 17, 2013 4:33 pm

I am really suprized that no one has thought about getting a old or used APC unit and disconnect the internal batteries and connect Deep Cycle 12 volt batteries in parallel for more amp hours. Troy it would be a Idea for your PC and Monitor, And a L.E.D. light or 2. So when the battery bank is down you can unplug it from the inverter and still be able to use the PC without draining the Main Battery Bank. Just a thought.

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Post by hi_tech_guy_18 » Sun Nov 17, 2013 7:19 pm

PC UPS Inverters are 24V (2x12V) for the 1200VA (720 Watts) ones anyway
Only problem with them is they have a nasty cheap & weak battery changer that's incapable of charging up larger spec battery's outside there approved battery spec

Sadly Being off grid it not recommenced due to the 2nd waste efficiency loss by the 2ND Charger + 2ND Battery + Inverter means your full system will consume more power in the Double losses

- You do better looking for TV's / Monitors where they use a External power supply brick and run on 12V / 24-28V
> allows you to use a DC DC Converter Regulators (12v to 12v) or (12V to 24-28V)
This way you can connect to the battery DIRECTLY and avoid the efficiency losses of a DC to AC inverter and have more runtime

You can also get Dual Battery Bank Regulators that allows one MPPT Charge controller to effectively charge 2 independent & Separate battery banks simultaneity

Dual Battery Banks have many configurations and setups

Bank 1 Can just be 4x Battery's that just run LED lighting and low power draw Devices due they don't use much
- in this setup the Bank 1 will be the fastest battery to recharge to gets recharged first
Bank 2 Would be 6x - 20x Battery's for higher load devices and take a little longer to recharge but if bank 1 fills up quickly it soon gets Bank 1 Charging Power and fills up faster

Another dual battery setup is where you have 2x banks with the same number of battery's and you switch between them for use however they both get simultaneously changed still
10x on Bank 1
10x on Bank 2
- This setup you can allow a Bank to get a extra days worth of charge without use while still using the other bank daily

When say Bank 1 has Hit its max Charge level every 2-3 days means you can use heavily appliances every other day in a while for the day then switch to it so becomes the Dally bank while bank 2 gets 2-3 days of Full Charging

and in a Emergency you can use Both banks together More Ah or a Quick recovery by allowing a more charged 12v bank to balance charge a lower voltage bank due you went a little too low 8v battery levels on the one bank (with Ture solar Deep Cycles you can go that deep into them and they recover just fine but don't make habit out of it)

mr bugsier5
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Location: Brielle , west coast of holland(europe)


Post by mr bugsier5 » Mon Nov 18, 2013 6:47 am

that's the exact way we connect systems in boats and of grid rv's here at my company VRM marine, one small battery set for starting, big battery set (mostly agm or better) for users (ligts and inverter, pumps etc)
what we do in some installations is even use a thirt battery bank, to keep light and inverter seperate.

or lights and inverter and bowproppellor

in some cases even more battery banks, one for starting engine, one lights and pumps , one inverter and one for the bow prop.

(mostly we combine the bowprop with one of the other , but some customers want everything seperate!)

we also use spesialized batterys for seperate purposes, agm battery's for lights and inverter (less amps over longer tyme, low cranking amps but lots off amp hours)(asking more and longer charging amps),
and normal start battery's for starting and bow prop (lots off amps in short time)(high cranking amps but low amp hours ,)(these do not ask a lot of charging amps)

we connect these sets together with a Fett diode bridge (Victron)(low losses) for the charging alternators from engine(s) or generator(s)
in these cases we conect a system to switch the solar system to the battery's seperate by means of a battery combynerswitch.
or via electronicly regulated parralef relais (Victron Serix)(these relais work with a electronic mesuringand tymer computer , if loading volts are available (master battery becomes over 13,5 volts,) its switches the battery banks parralel,

we mostly make the inverter battery box the biggest one , using it as main battery, connecting all equipment to one battery bank, keeping the engine battery seperate so jou can always start the engine , even if you have drained the master batterybank.
( so a two bank system)

we build (and still do) lots of these systems , they work great!( we are Dealer off Victron energy, mostly used here in europe.)
(see the internet side of them on, on this site you will find the systems we often use in off grid, combined on/offgrid and boats/rv's with interesting tips etc.)
dont be afraid to ask!, a stupid question does not exist!
forgive me my bad English!, as long as you know what i mean it,s fine for me!
(you thry dutch, wont be easy to! HA HA!)

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Post by techman » Tue Nov 19, 2013 7:29 pm

I have often considered the idea of ripping one of them apart to experiment with but now I have the pure sine wave inverter in my RV. I do have an APC in storage waiting for a project one day though.

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