Battery Charging

Hi Geoff,

this depends on how often you're near a 240V power outlet.
If you get access to one regularly, I'd use a mains powered charger.
If you're out and about for most of the time, then you should consider DC/DC or solar.
But it also depends on how deeply you discharge the batteries on a regular basis.
What type of batteries? AGM, flooded, gel?

cheers, Peter

G'day Geoff,

You don't say what model Prado you have. I don't know what the alternator system on the 90 series did, but the 120 Series present the low output problem. I have a 120 Series and have dealt with this.

First up, I'd recommend you keep your auxiliary and camper batteries topped up on the mains powered smart charger as a matter of course. If they're not in use, top them up every month or so.

Personally, I think it's best practice to use a DC-DC smart charger for your two extra batteries, regardless of the alternator output. That way your batteries are getting exactly what they need for best life.

The 120 Series Prado charging system is notorious for its low output, down to 13.2 volts once the engine battery has come up and the system has warmed up. Other manufacturers have or are following suit in their later models.

13.2 volts might get an AGM or deep cycle battery up to about 80% charge. If that's all it ever gets, it will gradually sulphate. Sulphated batteries lose capacity. For a start you will never get that 20% back and secondly, the sulphation will slowly increase so that your battery gradually loses capacity untill it's useless.

The trouble is, it's insidious - the battery looks like it's ok because on light loads it continues to work, but put a heavy load on it and it will run flat sooner and sooner as the condition progresses. It will appear to re-charge, but the load on it will tell the story. Eventually, even with a light load it will just die.

You might get three years life out of it, maybe less, whereas a well cared-for AGM battery could last 6 years.

If you can afford it, my recommendation is to install a dc-dc smart charger for each extra battery.

PM me if you like

Cheers

Frank

Geoff it depends if you are using much of your battery power and the type of battery in your camper. If you deplete your battery far with your camping the Prado will take ages to charge it. I mean ages, as they are renown for dropping back the available voltage to batteries when the engine warms up.

The beauty of the DC - DC charger is that it can use the low voltage as supplied to it and the main start battery and output a potential 14.4v that can charge your camper more quickly. With the battery bank I had in the Kimberley, it was the only way I could ever see a day to day 100% charge from the 100 Series.

I have a switch in my charge line as I also can charge my secondary battery in the car with the Ranox

Hi Geoff, I think Peter from battery Value summed it up perfectly. My initial comments would be that you aren't having any problems at the moment but you have become concerned for the long term reliability of the batteries. If you are not regularly discharging the batteries to a dangerous level then the alternator issue isn't as critical. Top the batteries up with a high quality 240v mains charger regularly and you'll be fine. If you are going to put more load on the batteries consider solar as Peter mentions.

Hi Geoff,

I would suggest you first learn how your alt works, no standard alt in any vehicle will charge any battery to 100% of its capacity.

A smart charger is also a good investment.

Col.

Hi Geoff,

Unless your cable run from the primary battery and isolator through to your auxiliary battery is inadequate, the chances are your auxiliary battery in the rear of your Prado is getting a good charge.
I agree with Peter that a charging routine using an AC charger is good practice from time to time to ensure full charging of the auxiliary battery.

The battery or batteries in your camper however, extend the distance considerably and this is where a dc-dc charger will ensure a full charge to this remote battery bank.
The dc-dc charger boosts the voltage received to an optimum level, then applies a multi-stage charging routine to these batteries while travelling.

It would be beneficial to also use an AC charger on the camper batteries from time to time, to ensure a thorough charging process is applied to prolong battery life.

Thanks guys,

I was originally of the opinion that my Alternator was charging all my batteries to 100%, and because I have never had any battery problems I was happy with that knowledge.

I have an Arlec automatic 5000 battery charger at home for Lead Acid batteries at 12.4 Volts, hope that will give close to 100% charge.

There is a c-tek charger which came with the van so I'll top up all the batteries on a monthly basis from now on while I research a new system for the whole setup.

I have a 20 watt solar panel which might be ok for maintaing the van battery.

Plenty of research to do now that I've started this.

Regards
Geoff

Hate to upset anyone but an Alternator can fully charge a car battery, infact if not operating correctly can well overcharge a destroy it.

A standard Alternator (pre heavily compensated) will output around 14.2V ~ 14.5V. This is approximately the same as a smart charger will output for the bulk charge.

The only time you need to exceed this is if the battery cells need to be equalised and this would not normally be the case for a battery in constant use and in good condition. Charging the battery with a smart charger that has an equalising function (most don't) every 6 months so will overcome this issue.

Devices are available to increase the output voltage of todays heavily compensated Alternators.

As for DC DC chargers, they have their place but in most normal setups can be more of a liability than advantage adding more complexity and lengthening recharge times.

Cheers
LeighW

Correction all batteries these days use calcium and ultra pure lead grid plates as they offer greater mechanical strength and lower gassing.

Cheers
LeighW

Geoff,

And, perhaps lastly :-), this car charging need to be kept in perspective.

If you do a lot of touring, away from 240V for long periods, then your car needs to be the functional equivalent of a mains charger so that from time to time you can fully charge the batteries. Depending on how much has been taken out of the batteries, a 6 hour drive could hopefully be the euivalent of overnight on the mains.

If, on the other hand, you only drive a couple of hours to a few favourite spots, or base-camp for long periods so that you don't drive often, then what the car does is less important. For that you need solar and/or generator with a mains powered smart charger.

Cheers

Frank