Charging Batteries from a petrol generator

basewindow

Hi, all the way from Victoria Australia.

I've tried searching the net for forums on this subject in Australia but can't seem to find too much, especially on 'off grid' stuff, and usually find stuff by companies or businesses that just want to sell you something.

Last year I sent up a very small 'Off Grid' system for my small shack on my bush block, which has none of the normal services connected. As I said it's very small at the moment but with a little bit of scope for more down the line. I only have at the moment 1 x 120w panel and 2 x 12v 100AH AGM in parallel, 1 Manison 30A Reg and I recently put in a Bogart Trimetric RV2025 battery monitor. I only have 4W LED 12v lights x7 which are never on at once and a 12v water pump. I run a small 600w/1200w pure sine wave inverter, for the few 240v devices, such as a small LCD TV, Radio, laptop computer etc.
I only get up to it a few days a month so what I have at the moment seems to work ok. I will probably add another 1 or 2 panels in the future and probably another 100-200AH of Batteries.

Now comes my question. Actually one of a few but I'll ask the others in a different Thread I suppose. On the rare times I do actually need to charge my batteries by the generator (4KW Digital Inverter Petrol) with 3 stage 20A charger (240v over here)

A: Where do I physically connect the leads from my genny and charger to my system, ie: At the battery terminals themselves or somewhere else?
B: Do I need to shut off the breakers to the solar array, Reg, DC load etc or is it okay to leave everything on. (I assume that since the Regulator is supposed to Regulate all that stuff and the panel has a reverse polarity diode etc I wouldn't need to......

Cheers,
Cam

westbranch

Re: Charging Batteries from a petrol generator

welcome to the forum, recommend you go to the NAWS FAQ section on batteries and have a good read.
http://www.windsun.com/Batteries/Battery_FAQ.htm
Q1 connect the leads from the charger to the battery terminals
Q2 NO need to disconnect the PV connections, the charge controller will sense the batteries are in a charged state and go to float setting.
you will need more solar panels as you are undercharging the batteries.

hth

niel

Re: Charging Batteries from a petrol generator

i agree to the batteries and you can make it more equal of a charge by putting the plus of the charger to one battery and the minus of the charger to the other battery.

most controllers will block any loss of power back through the pv at night, but i am not familiar with that controller to say for sure. you could try to measure for any current flow with a dmm and if it does it should be on the low in milliamps side of things and not in amps.

i would think you'll be running the genny fairly often with those loads. a 120w pv will not do as much as you may think. i guess you know that already as you have a battery monitor. be sure not to drain your batteries beyond 50% to help preserve battery life.

basewindow

Re: Charging Batteries from a petrol generator

Thanks again.

You may be surprised how many hours of sun we get here per day and even during winter. When I designed the system, I punched all the numbers into a universal calculator for my area etc and found that it just fall into the limits. As I said I dont get up there much, only a couple of days a months. Lights are all 4W LED. The only thing that draws constant power is the 4w 12v fan on the composting toilet. The lowest I have seen the voltage on the battery, after four days was 12.4. I didn't have the Trimetric at that stage so I don't exactly know how much I used,but according to the Reg I was putting back 20+AH per day. I suppose now with the Tri I will get a better idea of what's happening.

Cam

techntrek

Re: Charging Batteries from a petrol generator

Whatever amount of energy you think you are getting from your PV you are most likely getting half of that available to you from the battery, due to various losses within the system. Including the charging process, efficiency of the inverter, wiring losses, etc. Also don't forget the idle current of the inverter itself (the amount it uses to run).