Cheap car batt charger?

Conachair

Conachair

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I liveaboard & have 200Ah batt bank typically goes down to about 70% overnight. Charging is solar \ wind & honda genny (1kw) connected to sterling 20a mains charger. Solar will keep up with fridge during the day and put tiny bit ontop but not enough to get back to full charge. Right now sterling is putting about 14a into bank. It takes forever. I´m considering getting a cheap car mains charger, maybe 50a, and using this to get a load of charge quickly back into the batts in the mornings, up to, say, 85%, then in the evening using the sterling to back to near full charge( charging laptop at same time).
Any holes in this cunning plan? Not sure how many amps I´d get out of a cheap charger either, maybe I´lle try to borrow one for a morning. Would love more solar and bigger mains smart charger but money aint there.

TIA
 
Hi Conachair
I have 220Ah battary bank and to fully recharge would take about 5 days. My cheap charger (halfords)only gives out 2amps weither this is enough to keep you topped up, but i have seen some reconditioners on the shelf that do 8amps but they were about £50.
Cheers
Rich.
 
I suspect that the cunning plan is limited by the size of output from the genny. If it is 1000w, then you have about 4.5 amps to use for charging, whether you use the genny via the charger or directly via a 12v output socket. What model Honda is it ?

To cope with your power consumption you need a bigger genny or an integrated system with bigger solar panels, bigger wind generator, and an empty bank balance.

The more systems you route a charge through, the more power you will lose through transmission and conversion inefficiencies.
 
Most Car chargers are in the 4 - 8A range with odd ones have boost at 10A ... not often to find one that is higher than that.

Even the pro job we have for our truck batterys is max 15A at 12V, 10A at 24V .....

To get a high ampage rate - you'd be looking at a professional garage unit and they are usually designed to quick boost charge - not to stay charging a battery + they'd be expensive.

Think you have to think up another plan of action on this ....
 
A standard charger will not output a high enough voltage to provide a full, quick or effecient recharge. Most are clamped at 14-14.1V. You should be attempting to acheive around 14.8V. Because the output voltage of the charger wouldn't be able to overcome the internal resistance of the batteries, you will see a tapering off charge - meaning that it will take hours and hours and hours of charging to get anything meaningful back into the batteries.

Quite right about the limit of the generator - a 50A charger, in theory would use 700 watts. However, most car chargers - especially cheap ones aren't power factor corrected, meaning that a 50A unit will pull around 1400 watts.

A car charger is probably a false economy. Through decent power factor correction (which makes the charger more effecient and puts less load on the generator), and being able to charge the batteries quicker, you would really be much much better off buying a PFC Corrected 4 Stage smart charger.

Why don't you run your Sterling unit off the generator? You'll find it will outperform a 50A automotive charger anyway.

Don't throw good money after bad would be my advice!

Cheers - james
 
All I am saying is the following:

The wish is to use a 50 A 12 V car charger.
The output is 50 A x 12 V = 600 Watt. If the charger has a 100% efficiency it will need 600 W input so the genny will run at 60% load. The higher the input voltage the lower the input amps. In this case 240 V from the genny which means 2,5 Amps from the genny.
And, yes, the 12 Volt side wiring in a 50 Amps charger is quite impressive!
 
Forget all what all of these doomsters are saying. When we lived aboard we had a solar panels, the engine generator and a battery charger. We kept our 220ah domestic and 110 ah starter battery banks right up to the mark with these three with the battery charger doing the lions share when in port.

When we started out we didn't have the solar panels and we bought the battery charger in Lisbon. It was a bit of whopper, certainly not a Halfords cheapy, and it kept the domestic batteries right up to the mark merely by leaving it on until the charge indicator dropped to low. This usually took about 2-3 hours. Our electrical requirements, when in port, were for a fridge, cooling fans and a bit of domestic lighting.
 
Cheers all, there goes my cunning plan. No idea where I got 50a from, just did a quick google and, indeed, cheap car chargers do all seem to be more in the 6a range. Better off keeping to the genny running sterling mains charger as I do at the moment. The genny (eu10i) has a 12v output but seem to remember this is only a few amps. Oh well, never mind. /forums/images/graemlins/frown.gif

Cheers
 
Can we keep this factual?

A 50A charger DOES NOT pull 600watts. You have to incorporate the power factor. The Power Factor of a non-corrected ferro resonant charger is between 0.5 and 0.7 - Divide the wattage by the power factor to get true power drain.

James
 
I was keeping it factual. I'm not disputing your undoubted technical knowldege in this area all I 'm doing is reporting on what we actually did.

BTW, you don't need to pull that huge wattage unless you want to charge flat batteries pronto, but what do I know I'm not technical.
 
I'd increase the size of the battery bank so you don't cane it so hard. This will have the twofold effect of being quicker to recharge and lasting longer.
 
Sorry Chris - not meaning you! Flying Dutchman was saying that chargers were 100% effecient. None are!

A 10A 4 stage smart charger (good quality one) will be very close in terms of performance to a car charger - even a 50A rated one.

Cheers - James
 
You can get 50A chargers, but the battery bank will probably not draw 50A unless charging is very much boosted in volts.
You could divide the bank and use more than one smart charger.
You could try to reduce consumption, maybe by spending the money on more efficient stuff.
Increasing the size of the bank may well be best.
 
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