Charging an AGM battery

Hi teege

Any advice from me on this subject may be a case of the blind leading the blind (lol) - but why wouldn't you simplify things and upgrade the wiring to your rear power outlet, and simply connect the battery to that?

I have a slightly different setup, in that I have a separate circuit running to the rear through some sort of controller fitted at the main battery. When stopped I use the inverter to charge those things that need it, otherwise I run lights and stuff direct from the outlets on the portable battery.

George_M

The alternator direct will give you quicker bulk charge, but will only get to about 70% full.
The inverter and Ctek as you describe, will give you a much 'fuller' charge to your AGM, but you don't say how big the Ctek is.

The next alternative is to add a Redarc between the 2 batteries and use the Ctek as well. This will give you the best of both worlds.

Cheers,
Peter
OKA196 Motorhome

Hi Teenge,
A 300 watt inverter only puts out about 1.5 amps and a agm at 80 % charge can accept 10amps. I feel it would be far better if you charge the the battery via your cars charging system using a cut out solenoid, Anderson plugs and 10 mm. wiring.
Arthur

Teege,
Interesting responses above :-))

The 7amp CTek charger is the biggest that you could run off a 300watt Inverter. (Input for XS7000 Ctek is listed at 240V @ 1 amp which equals 240 watts).

If you recharge off the Ctek, you'll be limited to 7amps.
If you recharge off the alternator, you'll initially recharge at over 30 amps and this will taper as the battery is recharged.

So I would only use the Ctek when you have access to 240V.

Cheers
Phil

Hi Teege,
This will work with a Ctek charger up to a theoretical maximum of the 25 Amp model.

Note I said theoretical maximum of the 25 Amp model. In reality with loses you'd be restricted to the 15 Amp Ctek.

The biggest problem as I see it will be when you plug the inverter into the cigarette lighter which I assume from your post is the standard one in the dashboard of your car.

The Inverter will be attempting to draw a shade over 25 Amps at full load. There are no cars made in this world that I'm aware of capable of supplying 25 Amps continuous or intermitent from their cigarette lighter socket!

The factory wiring is just way too small for the job you are planning.

To make this work you'd need to run a dedicated cable of appropriate size back to your starting battery complete with fuses or circuit breakers and a relay to disconnect the inverter when the engine was switched off.

Geoff

Teege,

I have the setup your mention and it works great for me. I have a dedicated power supply with heavy duty wiring (can't remember the sizing) to the tub in the rear. It is switched via a relay to cut power to the anderson plug when the engine is switched off. On top of the battery, I have a 300W inverter (electrically isolated) and a 6 amp 3 stage charger. I find my 100 a/h AGM receives a full charge (goes into float mode) after about 5 hours driving. Prior to putting in the heavy duty wiring in, I tried it with lighter gauge wire, but the inverter continually protested and would not fire up to run the charger. Problem fixed with the heavier wiring.

Cheers,

Dave

Read what Collyn River says....

Cheers
Peter
OKA196 Motorhome

teege,
You want to " attaching a Ctek smart charger ... to charge a 120 ah AGM battery while on the move ... on packing up attach the charger to the battery and top up at least some of the charge while driving "

Take your vehicle to a smart auto leccy
ask him to test the *Alternator output* for you!

You want to charge a 120 ah AGM, so the battery will NOT be 'dead' when you pack up in the morning and your about to go driving again!

Forget the hassles of extra charging via the Inverter, your alternator (if it's working correctly) will charge the AGM with-out problems, so many MEMBERS here on EO have proven it time an time again!!

Check for your self, run your fridge for at least 24 hours, then turn it OFF in the morning.
A few hours later check the battery voltage BEFORE you start the engine, to eliminate false surface voltage readings.
Go for a drive for just 30 mins and recheck the AGM voltage 3 hours later.
(please post your voltage results)

Mainey . . .

In effect what you propose is a system that will work but ,and its a big BUT , it is a very poor use of power ,, vehicle alternator to inverter to Ctek to battery = 13.8v to 240v to 13.8v to battery , , inverter generates heat =power lost , 7amp Ctek also generates heat = power lost ,,,,, a better alternative is a dual battery controller [ Redarc / Piranah ect] mounted under bonnet near starting batt and running 8mm sq pos and neg wire to a 50amp Anderson plug to same plug at your proposed portable battery box , save your Ctek for home / dedicated 240v power supplies ,,, less complicated , less equipment to go wrong and a f
ully charged battery.

PS. another "bad" aspect of the system you propose is that when you are on the move /stop/ start the inverter and Ctek are also subject to stop /start ...... not so good for either unit or the battery that you are trying to charge as the Ctek will need resetting and or go through all its differing voltage stages every time you stop / start even if only for a min or two.

Thanks guys.
I think the overall consensus is that my suggested system is not ideal. I am leaning towards the suggestion by Axel and others . I guess that having the inverter I thought I should be using it. But it will certainly come in handy for other purposes.
Thanks again

teege