Battery charging a long distance away.

I am looking at a battery bank of 8 - 6v 225 ah trojan batteries and a samlex 1000w sinewave inverter for a barn which is about 1000' from any electricity. The owner is going to run a small fridge, some 12v lights, a tv on occasion and a laptop computer, he is sort of the minimalist hippie type. My first thought would be to charge those batteries with 4 evergreen 115w and an MX 60. The owner asked if I could just run 1000' of extension cord down and just hook up a battery charger to the batteries and skip the charge controller and PV modules. Not being too knowledgable about battery systems here are my questions, which will probably be answered by more questions:

1. Does the first system sound like it is sized properly for his usage?
2. What sort of charger would be best to use, and what gauge wire would it require to run an illegal cord down the hill without catching the grass on fire. This is not an option I want to go with, but I need to see if it could be legitimate, or have a reason why it's not.


  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Battery charging a long distance away.

    that's an interesting thing to need to do by running it 1000ft away. as to the pvs being enough it would depend on his usage, but odds are it won't be enough even for just the frig. if he can't get utility 110vac to his place he then needs to invest more into his place with pvs. now if you can or must run wire 1000ft then it should be 110vac or even 220vac as this reduces losses. no extension cords in doing this either, but a hardwired pole type arrangement would be in order with larger sized wires. you must determine if the batteries will deliver what the current requirements would be over the course of a day and if so then the rest can be roughly figured. the better bet is running the 110vac on poles with good sized wire and a fused box at the end of it for power distribution.
    now if going with the pvs then you know you must provide the watts for the loads plus the losses and factor in the time for use and charging. now i roughly would figure the evs to give 400w ptc. with all of the losses involved this could go down to 300w and this would be delivered for every hour of full sun. keep in mind the winter sun is far less than that of the average or summer sun available and this varies as to locations. so 300w/14.5v=20.5amps approximately. this is about a 2.3% max charge rate and you should be at or better than a 5% charge rate for those batteries. to use those batteries the pvs need more than doubled. now this would be a 900ah battery system at 12v so you can utilize 450ah before needing to recharge the batteries, but the rate of charge should minimumly be at 45amps and if you can go with 90amps.
    i'm not trying to actual do a setup for you, but rather show you a basic way of thinking for roughly estimating this. you always must account for the power used over a day before the rest can be worked into this. the 110vac max power indicates the inverter w rating to be used for all of the 110vac stuff. some things could also be run on 12v and should be as the losses from the inverter use could be lessened. all of this represents the total power used over the day that the battery must deliver without exceeding 50% of the battery capacity.
    from there you move onto the controllers and pvs. it all works backwards from the needs(power used in a day plus leadway for cloudy times) to the storage(the batteries not to exceed 50% depth of discharge and lower for cloudy periods) to the source(the pvs or other power sources).
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