Thread: Mixing AGM and wet cells...

Is this true? It seems odd.

Originally Posted by Fridge&Solar

Standard car and truck alternators are designed, for various good reasons to recharge car batteries to only 70-80%, and this works very well for normal cars and trucks, ....

Noting most cars get used for short journeys and have a lot of start/stop cycles, wouldn't this be very bad for a battery?

Originally Posted by p38arover

Is this true? It seems odd.

Noting most cars get used for short journeys and have a lot of start/stop cycles, wouldn't this be very bad for a battery?

Hi Ron, this is the “Shopping Trolley Syndrome” I mentioned earlier in this thread. It is really not relevant to most people on this forum as their vehicles are more likely to be driven for quite a few hours between uses while on a trip, when the auxiliary battery is required.

As I also pointed out, the article is based more on a sales ploy than on the reality of long distance driving.

Tim, like many people who use the 'net, I've become increasingly sceptical of stuff I read.

As you know, I'm an electronics tech by training (not that I've done much in the past few years) but batteries are not my field of expertise. I rely on the experts. I don't know who to believe!

I'd have thought that blokes like Collyn Rivers would know their stuff (I first came across him back in the Seventies or Eighties when he was editor of Electronics Today International).

I've just been hunting around the 'Net for some of his stuff. I see he also mentions the 70% charge for car batteries.

Originally Posted by Collyn Rivers

A vehicle charging system is deliberately designed to drastically cut back charging at 70% of full charge. The only really safe ways to approach 100% charge (90% is a realistic target) is via adequate capacity solar modules and solar regulator; or via a ‘smart’ charger – also increasing known as a three-stage charger

I do note he says about himself (elsewhere):

Originally Posted by Collyn Rivers

This is a field that's a long way from rocket science and I seek no credit for apparently uncovering it. Any electrical engineer would have done the same (and probably much quicker because I'm a research engineer). But there appear to be hardly any electrical engineers working in the practical side of the RV industry.

Sorry i cannot help myself - broken promises i know!

Originally Posted by r.over

Interesting articles, but they appear to deal with solar and other power systems. They do not seem to deal with motor vehicle batteries.

Yes they deal with Deep Cycle batteries what i have been talking about not your standard car battery.

"By the graph in one of the articles, at 14.5 volts (alternator output), you will charge them to 90% plus. To most of us, that is close enough to fully charged. " Yes agreed - for me that is close enough too while driving. But not fully charged which is how this all started!
When i get home i make sure the DEEP CYCLE is looked after, fully charged using a three stage charger so that i get more cycles and have a full battery for my next trip.
"It appears that you are attempting to argue fine points that are not overly relevant to motor vehicle drivers, or it might mean that your fridge cuts out an hour earlier." Without a doubt i am discussing a optimised situation and maybe the extra hour of fridge life is important to ME especially when i have been charging using solar or other means because the car is stationary while i am fishing . This may not suit all but i think it wrong to completely dismiss the research and say these chargers are just for SALES and that the alternator is perfect. I think the system that drivesafe has designed and sells appears to be great (BTW i didn't know that when i started these posts), reasonably priced and practical for an automotive application. I use a similar system! I NEVER said an alternator based charging system wasn't practical just pointed out the research about charging and care of DEEP CYCLE batteries and was told i was wrong.

"Based on your articles, an alternator will not fully charge a car battery, but it will get close." YES that is all i have said all along. We could argue about % but in the real word in doesn't really matter if you need more hours add more batteries. For ME cycles is also important because they are expensive batteries so i take a bit more care

Better go to work to earn the money for my next trip.

cheers
Remy

Originally Posted by drivesafe

Hi Ron, this is the “Shopping Trolley Syndrome” I mentioned earlier in this thread. It is really not relevant to most people on this forum as their vehicles are more likely to be driven for quite a few hours between uses while on a trip, when the auxiliary battery is required.

As I also pointed out, the article is based more on a sales ploy than on the reality of long distance driving.

So - stupid question.... if you'll permit me.

In between the long trips, when I don't need the auxiliary battery, should I leave it sitting in the battery box connected up, constantly being topped up by the alternator. Or should I disconnect it? Which would keep the battery in the best condition?