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.

Brand
Model
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
Enerdrive
ePOWER 40
40A
(selectable 5-10-20-40A)
700W
17.50W
Enerdrive
ePOWER 60
60A
(selectable 5-20-40-60A)
1050W
17.50W
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.

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