Thread: Deep cycle batteries

Iam looking at getting one of these batteries for our van "the 120 or 150 AH" Our caravan manufacturer "Kedron Caravans" has changed from lead acid to glass matt batteries for longjevity

http://www.absorbedpower.com/battery/products/12volt/

Hi MarknDeb, the main reason motor home, caravan and camper trailer manufacturers are fitting these types of batteries is because they can tolerate being left unused for long periods of time and not shorten the operating life anywhere near as quickly as conventional wet cell batteries.

If you have or are planning on fitting wet cell batteries and you maintain them properly, charging them regularly when not in use, you will get good operating life spans with these types of batteries.

The most important aspect to keeping ANY automotive type battery in good health when they are not being used, is to keep them fully charged.

Ok, so if these are dual purpose will they handle occassional winching ? and if not what will, can the Caterpillar dual purpose batts handle winching duties or am i best to hook the winch to the main start batt and use a deepcycle for lights/ fridge / other accessories ?

We have a Trojan 124 AH battery and was fitted in the van 3 years ago when made, its been great and we only use the van a few of time a year. Many other van owners use there vans on a very regular basis 2 or 3 times a month and there batteries only lasted a couple of years ??? this is why Kedron changed to a glass matt. I put the van on charge every couple of months and some times when charging i run a few lights to give the system a little work out (i think it does give it a work out and spose it sounds good) maybe this is why mine has lasted longer.

I stand by my assertion that GEL and AGM batteries usually do not charge fully in a standard automotive environment. They do not like the rough regulation as provided by alternators. they like smooth filtered DC with accurate voltage charge change points.

GEL and AGM covers a wide range of batteries and batteries these days are built physically and chemically for specific applications.

They can not be fuly 100% charged without a good quality multi stage charger with a temperature sensor on the battery. I know you can get close without the temperature sensor but run the risk of cooking the battery. I have plotted the current and voltage of batteries charging whilst monitoring temperature. It can be a close call on a warm day or in a warm spot , like under the bonnet, for a battery to cook. toward the end of absorbtion charge if the temperature rises (due to charging current or ambient) the current actually starts to inrease again and as that pushes the temp higher the current increases and before you know it the battery is too hot to touch and cooks, never to be the same again.

With a 3 stage charger the bulk charge (constant current = basically huge current and monitor the voltage as it rises) charges the battery very quickly up to maybe 60%.

Then when the maximum charge voltage is reached, say 14.7V it switches to stage 2 charging (contant voltage = maintain 14.7V and the current will slowly drop as the battery charges to around 95%) then when the current drops below a set threshold it switches to stage 3 float charge.

Float charge maintaind the battery at a voltage set by the manufacturer and is around 13.5V. The battery will achieve 100% as it equalises the cells over sevseral hours.

Now every battery has slightly different voltages for these stages and are specific within 0.1 to 0.2 of a volt. These require advanced electronic chargers designed for the purpose. Automotive alternators can not fulfill these charging requirements properly.

Any charging device i have seen for dual batteries in a car is designed to accept a wide variation of batteries and types and therefore does a generalised charge that will not get the best out of any battery type.

GEL construction is probably not up to the task of off road for physical construction reasons.

AGM is wonderfull technology and can be designed to be perfect for off road use. I have seen a battery with the case smashed and it still worked to start the car and drive away. But not all AGM is created equal. UPS batteries are often less physicaly up to the vibrations in the 4WD application as they are designed to sit in racks in computer rooms.

I am not tying to talk anyone out of buying UPS batteries and using them as i have done this myself, but batteries are fickle things and have lots of discharge rates and depths as well as charging parameters to get the best out of them.

Sorry but I am a bit anal when it comes to batteries. maybe i need regression therapy to unlock past lives or something?

zwitter

Lots of great info to ponder, might be best just to get an exide extreme for $115 with a 2 year warranty.

zwitter i was even thinking of changing the lead acid 12V 7AH battery in the brake safe unit to a 12V 1AH glass matt as the lead acid is dead. Now after what you had to say above iam wondering if it is wise as the brake safe unit charges from the AUX (blue) wire in the seven pin utilux, when we do a long drive it would be getting a permanant charge of 12v that could be as long as 10 hours a day. Do you think it would be wise for me to just replace with lead acid.

Do you know of any devices that can be used to correctly charge an AGM from an alternator?

I have even considered using an inverter from the vehicle battery and a 240V charger just to obtain the correct charge but it does seem a bit messy - and I would need to remember to turn it off when I stop!

It seems that 3-stage charger manufacturers only cater to folk who stop in "powered sites" overnight.

Even solar ones I have looked at don't seem to be true 3-stage. Humph!

Cheers,

Paul