Thread: AGM Battery Charging

Contact drivesafe, sounds like bs to me.

I don't have an idea of the system you've got on board and whether it includes a dual battery isolater.

As advised above , contact Tim (drivesafe) Home Page | TRAXIDE - RV | Traxide - RV 07 5569 2557 - he's very helpful over the phone.

A lot of members here (incl me) have his dual battery system and even if you aren't using one of his I think he would be the one to give you the right info.

Thanks two Up.

Hi Peter and as two up posted, it is BS.

It also sound like your whole set up might not be up to the job.

First off, you can safely charge AGMs mounted in a camper trailer or caravan, by your alternator.

Most new AGMs will tolerate 14.7v but even the older type AGMs, with maximum voltage tolerances of 14.4v will not be harmed if your alternator goes to 15+v during the start-up boost cycle that newer Land Rovers now do.

The reason for this is that the LONG cable run between the alternator, via your cranking battery, and then all the way to your house batteries, will act as a quasi voltage/current regulator.

Next, you should have at least 6B&S ( 13.5mm2 ) cable running between the cranking battery and the house batteries and this can be protected by a 60 amp fuse or circuit breaker, at both ends of the cable.

If your setup has a 30 Circuit Breaker, it sounds like the cabling might be too thin to allow proper charging of your batteries.

This diagram might be of some help.

Hi Peter and as two up posted, it is BS.
It also sound like your whole set up might not be up to the job.
First off, you can safely charge AGMs mounted in a camper trailer or caravan, by your alternator.
Thanks Tim, The guys selling the batteries warned me that AGMs do not handle the AMPs of modern day alternators, said it would go egg shaped!!!

My set up has a relay activated by the alternator light connecting a large cable from the alternator to the battery via a 30 amp circute breaker (all that is in the battery bay under the L/F seat) then on to an anderson plug at the back of the cab (as in a 130 dual cab one meter) and then to the back of the Slide On Trayon battery bay adistance of two meters.
What do you think should I up grade the circute breaker and put another one in?
Appreciate your help Peter

Hi again Peter and if your two batteries are in a low state when you start your drive, they could easily draw 60+ amps.

So first off, make sure all the cabling from your cranking battery to your house batteries is 6B&S or thicker.

Then I would recommend you fit 50 automatic resetting circuit breakers at each end of the positive cable.

Originally Posted by drivesafe

Hi again Peter and if your two batteries are in a low state when you start your drive, they could easily draw 60+ amps.

So first off, make sure all the cabling from your cranking battery to your house batteries is 6B&S or thicker.

Then I would recommend you fit 50 automatic resetting circuit breakers at each end of the positive cable.

I'm thinking that would be 50A breakers - not 50 of them

Just FWIW - I've had a 130Ah AGM aux battery in my county for a couple of years now, just charging from the alternator via a SC80 controller. Works perfectly, and no sign of the battery dying.

Steve

Moved to communications, Audio and electrics as its not really defender specific

Originally Posted by pjlhat

Having just installed 2 X 100amp hour AGM batteries into my Trayon Camper at considerable cost I was advised that I should now install a costly metering device to protect the batteries from the charge of the
alternator.
Prior to this I had two 6v lead acid batteries in the land rover and one AGM in the Trayon all being charged via the alternator through a 30amp circuit breaker and all seemed to work OK.

If I install a smaller circuit breaker, say a 10 amp will this give some protection to the batteries.
Peter

I must say that I have my doubts about charging differing battery types from the alternator.


Different battery types require differing charging voltages as can be seen from this Projecta 15A charger manual.





The AGM battery is charged at 14.4V during the bulk cycle and the Wet/Calcium gets 14.7V. This would lead me to believe that if the alternator puts out more than 14.4V you are overcharging (and thereby reducing the life of the AGM battery).


I'm no expert on the matter but have had an AGM fail on me and I believe overcharging was a part of the problem. I also have 2 x GEL's (which require a lower charging voltage than AGM's) in the van which charge off the alternator but these have a DC/DC charger in front of them that regulates the charging voltage.


On the other end of the scale, I believe that undercharging an AGM will also shorten its life.