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What’s the largest battery charger I can run on my 1kVA generator?

This is another question we get asked regularly. Taking the most popular 1kVA generator on the market today (Honda EU10i), this unit can produce a maximum output (for a short period) of 1000Watts. Continuous running, the EU10i can operate at approx 800Watts maximum.

The most popular battery charger’s on the market today range from 15amps-40amp for charging the average caravan/marine application with battery capacities between 100Ah-360Ah. So let’s look at the AC power consumption required by the top brands and see how much power they require to charge you battery bank.

Amp Rating
AC Power required@240v for maximum output
Watts Per Amp
CTEK XS25000 25A 696W 27.84W
CTEK M200 15A 696W 27.84W
CTEK M300 25A 696W 27.84W 
Projecta IC1500 15A (selectable 2-4-8-15A) 240W 16.00W
Projecta IC2500 25A (selectable 2-6-12-25A) 792W 31.68W
Projecta IC3500 35A (selectable 2-8-16-35A) 1080W 30.85W
Projecta IC5000 50A (selectable 2-6-12-25-50A) 1488W 29.76W
OZcharge OC-PRO1200 12A (selectable 1-8-12A) 175W 14.58W
OZcharge OC1225U 25A (selectable 2-15-25A) 720W 28.80W



40A (selectable 5-10-20-40A)





60A (selectable 5-20-40-60A)



All specification taken from the brands respective owners manuals on 20/11/2017

Based on the above table, the best bang for the buck is the Enerdrive ePOWER charger range. Based on 17.50W per amp the Enerdrive ePOWER 40A charger will run comfortably on a Honda EU10i generator at 40A. If you have a battery bank of 3 x 105Ah (315Ah), you could run the ePOWER 60A unit and dial it back when on the generator to 40A, then when back on mains power you can dial it back up for maximum charge.ePOWER Battery Chargers

Based on the original single stage charger back 30+ years ago, the equation to size your charger was 10% of the battery bank size, i.e. 100Ah battery = 10A charger. These days with multi stage charging, designated float algorithms and AGM/GEL battery technology, the equation is now closer to 20%. This being the case, your 2 x 105Ah battery bank (210Ah) is best charged with a multistage charger around 40A.

If you like what you’ve read, you can find even more helpful advice by joining our Enerdrive Unplugged Facebook group! The group is for sharing installations, errors in installations and best practice install guidelines utilising Enerdrive Products across Caravans, Campers and 4WDs. Acting as a space to leave feedback and comments, get inspired and learn from other veteran users along the way!