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Author Topic: Small charger with big inverter?  (Read 1386 times)
SimonD
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« on: April 29, 2015, 03:12:46 PM »

Hi,

As a temporay measure I'd like to use a 1kw 48v charger with a 8kw 48v low frequency inverter. Will this kill either the inverter or charger? They would both be connected to the batteries and when the generator is running to pump water and charge the batteries there is a good chance that the inverter could pull 3kw. Do you think it would harm the charger, which would be connected to a 5kw generator. This is a temporary measure whilst I rearrange things and get the solar sorted, at which point I'd swap to a 5kw inverter/charger. Should I avoid having the charger and inverter doing their stuff at the same time?
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knighty
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« Reply #1 on: April 29, 2015, 04:31:25 PM »

so you're going to have....

generator > charger > battery bank > inverter


if you're charging at 1kw
and using 3kw via the inverter

the batteries will supply the extra 2kw.... it's actually beneficial to run your charger when the loads are the highest.... because there'll be less strain on the batteries :-)


how big is your battery bank ?
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SimonD
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« Reply #2 on: April 29, 2015, 04:56:32 PM »

Hi,

The batteries are used forklift, I think the bank is over 1000 kw (does that sound right?) I'd have to look it up to be sure. Under normal use we use less than 1 kw and until recently we only had a 1 kw inverter with direct power from the 5 kw generator for larger items such as hoover, iron!, hair dryer!! and workshop. All the lights are LED, heat is wood, cooking is wood and gas bottle. having lost the inverter to a hair dryer, I'd like to make the 1kw charger last a few more months until I have the solar installed. 
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knighty
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« Reply #3 on: April 29, 2015, 10:56:01 PM »

it could be 1000ah ?  (amp hours)


whatever the capacity, if it's an old forklift battery, you'll be fine drawing 3kw out of it :-)


(I just wanted to make sure you didn't have a single old car battery you were trying to use!)
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oliver90owner
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« Reply #4 on: April 29, 2015, 11:13:30 PM »

An obvious question might be 'why not plug everything into the generator, while running?'  I could understand your problem if the generator was rated at less than the power needed.

Assuming here that you are running two items at 230V 50Hz.  You seem to be pulling only 1kW from your genny when you could be using more like its full, most efficient, output.
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SimonD
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« Reply #5 on: April 30, 2015, 09:17:14 AM »

Hi,

Yes it's over 1000ah (not kw... durr).  We've been on generator only for a few weeks, we'd like some lights and TV in the evenings without the generator running and the fridge is starting to smell a bit with only being on for a few hours a day. Also, the 8kw inverter would allow me to put the water pump back onto the batteries.
It's going to take at least 6 weeks before I get solar sorted and I have a Chinese 8kw inverter doing nothing. I was just concerned that the 8kw inverter would harm the little 1kw charger if they were on at the same time but that's just my ignorance and being over cautious!! I'll have to watch battery levels with only a little charger but I've got everything on 16amp plugs and sockets so it's easy to swap things around from generator to battery.
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