Thread: Battery Charging Complexities

i have been told a car alt will charge the battery to 75% with in 30 min then to fully charge could take hours , the best set up which i was told was run the car for 30 min then a sola pannel to top up the battery through out the day

Peppercorn, There are now several brands of DC to DC 3 stage chargers, some as high as 35 Amps.
These will charge a auxilliary battery exactly like a proper charger, and give you an idea of how charged it is. If I had a device that I really needed to be available I'd just buy one and then maybe look at solar later.
they vary in price from just over the $200 mark, up to I think close to $1000.
I'll be getting one before this summer, as I've already destroyed a $500 AGM battery with a normal dual battery system (batt was very low, weather was very hot, and I drove for 4 hours. the TD5's alternator supplied too much current and the battery overheated, that was that)

Fraser

Originally Posted by fraser130

I've already destroyed a $500 AGM battery with a normal dual battery system (batt was very low, weather was very hot, and I drove for 4 hours. the TD5's alternator supplied too much current and the battery overheated, that was that)

Fraser

Another example of how AGM battery technology is not appropriate for use in motor vehicles.

Garry

Garry, I have had an AGM ( Absorbed Power 90AH in N70 size)for almost 6 years now fed by its own 85 amp alternator with no problems. It is in the second battery position in a V8 RRC 92.

I only have a relatively thin wire to it from the second alternator which I see in my laymans ignorance as a current limiter. It charges to about 90% from 11 volts in about 2 hours driving and has been perfect, although now its getting a bit weaker than its 90AH would suggest.

So I think its not true that they are not suitable for car use in all cases. If you had one up against the Turbo in a diesel disco , then its probably too hot and probably lead acids would also have a short life.

By the same token I have read over and over that deep cycle batteries are unsuitable as second batteries as they cannot take fast charge.

Nothing has the same energy vs size as an AGM outside of a Lithium and at present that is very immature tech.
regards Philip A

It can take 4 plus hrs solid driving to charge a car battery up from nearly flat. Just starting and idling a car does not charge very well at all.

Sorry Gary, I disagree, no good as a main battery, and no good in the engine bay, but with a proper charging system, they are a fantastic battery.
Long lasting, vibration proof, install in any position, no explosive gasses.

Fraser

Hi Peppercorn, you are looking at at least 5 hours idling time to bring the battery back to around 90-95% SoC.

Next, if you use you vehicle as your daily drive vehicle and then drive for at least 3 hours going to and returning from your camping location, there is no reason to ever have to use a battery charge, on either battery, because alternators will not only fully charge your batteries, it will do both at the same time.

If on the other hand, you only drive it periodically, then charging the batteries would be a good idea.

A tip, if you find you need more power to be able to camp in one spot longer, simply add an additional auxiliary battery and you will take no longer to fully charge three batteries while drive than it takes to charge two. This is the biggest advantage of using an alternator as the primary charging source.

Originally Posted by fraser130

Sorry Gary, I disagree, no good as a main battery, and no good in the engine bay, but with a proper charging system, they are a fantastic battery.
Long lasting, vibration proof, install in any position, no explosive gasses.

Fraser

Ok - but the scenario you described of the car alternator killing AGMs is coming up more and more in forums. They just do not seem to be able to take the variability of the in car environment. Having said that, there are clearly plenty of cases where the batteries work fine - but increasingly people are reporting issues.

Garry