Dual batteries with Traxide SC80 and a 40A alternator

[steveG]

Its time to buy a second battery for my Isuzu powered 110.

Primarily its to run the Evakool fridge, but will also be running a winch occasionally. Typical use is weekend trips with a few hours driving each day, but also needs to cope with a couple of weeks with a couple of non-driving rest days included.
Main cranking battery is an Exide N70EX, and I've got a Traxide SC80 controller connected to an old 65Ah SLA battery retrieved from some upgraded equipment at work. Better than nothing, but its time to get a proper second battery.

I was thinking about an Optima yellow-top, but I spoke to the guy at Battery world today and he suggested either a Century Marine Pro 720 which is a dual purpose crank/deep cycle battery, or a Century AGM - both are N70 size and 100Ah. The Optima is AGM and 55Ah

What I'd like to know is how the 40A alternator on the Isuzu fits into the equation.
I've read that AGM batteries will take recharge faster than conventional batteries, but with charging the cranking and aux batteries in parallel via the SC80 I'm not sure that the 40A alternator is going to have the output to make use of that feature. Pointless spending extra money on an AGM if the Marine battery is going to do the same job for me.

Any comments?

Steve

[drivesafe]

Hi Steve and while I like sell gear, I would strongly recommend you look at upping the size of your alternator before you do anything else.

You are going to be having problems if you what to fit a driving light or two and if you do fit a dual battery system, if you run the batteries down a fair bit while camping, you are going to need to drive for many hours to recharge them and thats only if it’s day time.

A night drive, it would be almost impossible to recharge low batteries.

[steveG]

Hi Steve and while I like sell gear, I would strongly recommend you look at upping the size of your alternator before you do anything else.

You are going to be having problems if you what to fit a driving light or two and if you do fit a dual battery system, if you run the batteries down a fair bit while camping, you are going to need to drive for many hours to recharge them and thats only if it’s day time.

A night drive, it would be almost impossible to recharge low batteries.

Thanks for the feedback.
AFAIK there aren't too many options for the Isuzu alternators as it also needs to have the vacuum pump on the rear, and most of the truck ones locally are 24v. There's a 70A model which is readily available, and I think maybe a 120A one but $$$ from memory.

70A is going to be a lot better than the one I've got now, but is still quite a bit smaller than the 100A ones common on D1's etc. Not sure what other landy's run.
I'll ask over in the Isuzu section and see what people are running, but would you consider the 70A a worthwhile upgrade, or still marginal?

Steve

[drivesafe]

Hi Steve, and even a 70 amp alternator would be a major improvement.

The problem with a small alternator is not just it’s limited battery charging capability.

As above, if you have low batteries and drive at night, not only would you have a hard time trying to charge the batteries but the current draw caused by the low batteries would lower the alternator’s output voltage and this would have a major effect on just how bright your headlights would be.

Note, this would be the case without driving lights and the use of driving lights, even a couple of 55w lights, would make the problem dramatically worse.

A 70 amp alternator, would actually give some surplus power available to use for things like lights and improved battery charging.