Fully charging Aux Battery

Hi Norm C, you are probably right about the state of charge in your auxiliary batteries being way over the mythical 70%, you can get at least a 95% accurate idea of the state of any type of vehicle battery with a humble multi meter.

Simply let the battery stand with no load or charge connected to for 72 hours, then measure the voltage at the battery terminals.

The best way to obtain a no load, no charge situation is, after your next trip, on arriving home, where your battery is not going to be needed, take the Negative lead off the battery.

NOTE : - For safety reasons, leave the Positive lead connected.

When you disconnect the battery, note the make, type and size of the battery and then do a search on the net and get the relevant details regarding charge voltage as an indicator of the percentage of battery charge for that battery.

Hi TonyG, not being able to get your battery charged over 70% is an urban myth. In all fairness there are a few factors that have to be taken into account but for the vast majority of people who read this site, their driving requirements would put them in a situation where attaining 80 to 90% charge will be the norm and 90 to 95% would be common place.

Cheers.

Hi drivesafe,

when using a multimetre to get battery voltage, both batteries read about 12.8 volts.

From reading other posts, this seems to be reached when the battery is at 70%

This made me beilieve the urban myth was true

Hi TonyG, I’m not sure what you mean by “ this seems to be reached when the battery is at 70% “.

Although not knowing your specific battery's details but if a battery has been sitting for a while and has a reading of 12.8 volts then it is 100% charged and even allowing for the 5% error when using a multi meter, this is still at least 95% charged.

Have a look at the site I have posted below. The address I have posted takes you straight to a section on how to test your battery but have a look around the whole site. It is an exultant place for loads of battery related data.

Battery Data

Hope this is of some help. Cheers

Norm this is unrelated to batteries, how did you go with your brake contoller? i have installed the prodigy to tne 05 hilux and picked up our new eagle outback and found the same as you re not locking up. have it on b3 and 13 and have adjusted brakes on camper up also have 6mm positive and neg wires. still does'nt do what instructions say.
thanks christian

Much the same TW.
I operate on b2 at around 10.

Could never get the trailer brakes to lock up. Although you don't want your brakes locking up, I was trying to get there, then back off so that I knew they were adjusted for maximum braking. Suspect you were trying to do the same.

In the end I am happy with how they work. They pull me up very well with the trailer on and fully loaded.

Just would have been happier if the adjustment worked as described in the instructions.