What size genny for battery charging

Submitted: Thursday, Sep 13, 2012 at 18:35
ThreadID: 97997 Views:4131 Replies:7 FollowUps:8
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I am after a small 4 stroke genny just to charge batteries !...... I have a CTEK 15

AMP CHARGER = 1.8A rms at full out put..........my question is how SMALL of

a genny to power it????

& how much power is 1.8a rms?????

I have a 2.2 kva genny for the air con......but dont want to carry it when travelling

during the winter.
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Reply By: Ross M - Thursday, Sep 13, 2012 at 19:11

Thursday, Sep 13, 2012 at 19:11
G'day 1080 1
A 1.8 amp charger is a little bit bigger than the power required to run just ONE turn signal/indicator globe.
If you intend to charge a 1/2 flat 100ah battery by using the 240v from a generator it will take around 25 to 30 hours of running.

If using a compressor fridge off the battery being charged, the battery will go flat despite the generator running all the time and never being stopped.

A 100ah AGM battery can absorb about 20 amps maximum charge rate near this will be required from a battery charger to charge it in a reasonable time via the generator.

The 1.8 amps is ok at home though, to top up or maintain charge of a battery.

If for use out on the road/campsites a far bigger charger capacity will be required.

A 700watt generator is sufficient for most situations where a couple of batteries require charging. If using a Ctek or similar switchmode powersupply/battery charger it may be advisable to have an inverter generator, because the switchmode power conversion in these and laptops, sometimes don't want to start on power which isn't a nice clean SINE WAVE. Sometimes they burn out or overheat.

The normal generators are 240v but not the cleanest power or best voltage controlled either.

Aldi will have one soon, next week, which is inverter output and 4 stroke for about $350 but to make use of it a charger upgrade will be required.
AnswerID: 494819

Follow Up By: 1080 1 - Thursday, Sep 13, 2012 at 19:33

Thursday, Sep 13, 2012 at 19:33
Thnx Ross M.......

I didn't make myself very clear .... I have a 15amp CTEK

charger...in its spec sheet it states its 240v power use is 1.8a rms.....at its max

output (15 amps I guess)

& how much power is this 1.8a rmp????

thnx
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Follow Up By: Ross M - Thursday, Sep 13, 2012 at 22:00

Thursday, Sep 13, 2012 at 22:00
Possibly what you should have said is the FULL INPUT is 1.8 rms and at 240v that equates to a far higher charge current to batteries as others have also mentioned.
It does change the equation somewhat.
Akracy, acurcy, accuracy is the best thing. I just followed the path I was shown.
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Reply By: MartyB - Thursday, Sep 13, 2012 at 20:01

Thursday, Sep 13, 2012 at 20:01
Hi,
1.8 times 240 equals 432, Therefore theoretically 0.432 KVA.
A safe margin would probably be 0.8 KVA or 800 Watt generator.

from Marty.
AnswerID: 494821

Reply By: Member - Bruce C (NSW) - Thursday, Sep 13, 2012 at 20:27

Thursday, Sep 13, 2012 at 20:27
Gidday Ten eighty,
Does that mean you are poisonous. LOL

RMS = Root Mean Square.

240 volts X 1.8 amps =432 watts

This means you will need something like a 1Kwatt, or slightly, less charger.

There is some complex electronics in the Ctek so you should be looking at an Inverter genny so that it will have a clean sine wave and therefore not damage the charger.

Go for a 1 Kilo Watt genny and you will have a safety margin of around 100%.

Cheers, Bruce.
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Follow Up By: Member - Bruce C (NSW) - Thursday, Sep 13, 2012 at 20:42

Thursday, Sep 13, 2012 at 20:42
Actually 1080, you would be better thinking solar as a 200 watt panel will cost around $250 and a MPPT regulator will cost around the $100.

About the same price or less than a cheap 1 KW genny and be a whole lot more environmentally and people friendly as well.

My 80 watt solar beats a genny hands down. My 2 X 100 AH batteries are always fairly fully charged with a couple of hours of sunlight.

In fact I do not use the genny any more when travelling, it stays home.
And when staying in van parks I do not use their power as I do not need it, the solar looks after it all.

Just a thought. I have nothing against gennys unless it is under my nose.

Cheers, Bruce
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Follow Up By: Dennis Ellery - Thursday, Sep 13, 2012 at 21:56

Thursday, Sep 13, 2012 at 21:56
“My 80 watt solar beats a genny hands down. My 2 X 100 AH batteries are always fairly fully charged with a couple of hours of sunlight”

An 80watt panel and 2 hours of sunlight – What are you running, an electric toothbrush?
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Follow Up By: Member - Bruce C (NSW) - Friday, Sep 14, 2012 at 15:14

Friday, Sep 14, 2012 at 15:14
Dennis Ellery,
I have all LED lighting in the van, a 12 volt TV, the usuall 12 volt water pump and 12 volt powered piezo lighting on the gas stove. The frig runs beautifully on gas. I also have, but have not used in a long while, a Waeco CF35.

As I keep saying, everything 12 volt so that I do not waste power.

What I use is the tip of the iceburg of what I have available. From what I hear most caravan dealers are telling people that all they need is 1 X 80 watt panel. I can vouch for that philosophy but you are advised not to run inverters etc.

My 80 watt panel, I assume it is 80 watts, and poly crystaline at that, is more than edequate under normal conditions with my set up.

When on the road I turn on the telly, if reception is good enough, at about 5:30 and often wake up at 1:30 in the morning and turn it off. Batteries are topped up after a couple of hours of good sunlight so I do not worry about going to sleep with it on.

I was going to include in my previous follow up that I am about to fit a 200 watt Monocrystaline panel to suppliment the existing 80 wat poly on the van for the event of extended periods of overcast weather or camping in shady locations.
I did not mention it as I wanted to keep the comment brief.

However, if you keep your power consumption conservative and do not waste it then you can get away with fairly small consumption.

I have been experimenting with solar at home over the last 12 months as I had previously bought a folding 160 watt setup and tried several different PWM and MPPT controllers. I cannot notice a great deal of difference between any of them. Perhaps if I metered them I may have a better idea of difference.

One thing I have learned is that it would be a small jump for me to get off the 240 grid and go totally solar as there is so much available in 12 volts these days.
I even run 12 volt LED string lights in the house of a night. Plenty of light to see to get around with just 2 metres of LEDs.

So, what are you people doing that I am not, that you need so much power?.

BTW. I cannot afford an electric tooth brush, I am a pensioner after all. LOL.

Cheers, Bruce.



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Follow Up By: Dennis Ellery - Friday, Sep 14, 2012 at 16:42

Friday, Sep 14, 2012 at 16:42
Hi Bruce,
I must admit my wife and I are big consumers of electricity - about 120 ah/day – compared to you at approx. 12 ah/day (80 watts X 2 hours).
We have gas cooking and a 3 way fridge but 12 volt usage includes a 40l Engel as fridge, CF 40 Waeco as a freezer, TV and a few other bits and pieces.
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Reply By: Member - Rob S (NSW) - Thursday, Sep 13, 2012 at 21:02

Thursday, Sep 13, 2012 at 21:02
This is probably what your after?

chargers can supply enough charge in as little as 5 minutes to start machinery. Campers can run car fridges for 24 hours and charge their batteries in as little as 1 hour. Ideal for backup power in emergency situations. Designed and built for the marine industry, backup for solar powered sites, emergency services, earthmoving contractors, mobile mechanics, or anyone working in the outback. Note, some wet cell deep cycle batteries will not accept a fast charge & may require trickle charging for a long period of time. For an efficient system with faster recharge times AGM or cranking batteries can be used.


.christie engineering.




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AnswerID: 494824

Follow Up By: Member - Markthemilko - Thursday, Sep 13, 2012 at 23:09

Thursday, Sep 13, 2012 at 23:09
I'm thinking of buying a 2kva Honda genny for about $1900, as that will cover us for when we have a power outage at home (Perth Hills) such as we had a few months ago (30 hours), and it would charge our fridge battery when we travel outback and/or supply 240v power. The battery charger @ $1408 + freight would come close to the genny cost.
Any comments welcome please.

thanks
Happy 4WDriving
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Follow Up By: Dennis Ellery - Friday, Sep 14, 2012 at 16:51

Friday, Sep 14, 2012 at 16:51
Hi Mark
For the camper or caravaner the 240v genset is a more versatile option – compared to a dedicated 12volt dc generator. You will normally have a 250v battery charger anyway, for use when on mains power.
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Reply By: Life Member - Phil B (WA) - Thursday, Sep 13, 2012 at 23:18

Thursday, Sep 13, 2012 at 23:18
You could try this




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AnswerID: 494831

Reply By: CheapJeep - Saturday, Sep 15, 2012 at 08:51

Saturday, Sep 15, 2012 at 08:51
In Answer to your original question; I have and use a Honda EX350 2stroke Inverter generator (300 Watt) over the last 6 years which powers a CTEK 15 Amp Charger into a 100 AH battery. Excellent machine and can be picked up with your little finger.
Consequently - Your answer = 0.3kVA
Good Luck
AnswerID: 494934

Reply By: Nomadic Navara - Saturday, Sep 15, 2012 at 14:11

Saturday, Sep 15, 2012 at 14:11
If you put a small resistive load (say a 60 or 100 W light globe) on the output of a cheapie generator it does wonders in cleaning up the waveform when running things like switched mode power supplies.

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AnswerID: 494960

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