Minimalist car systems charging C/T batteries

Who tows their camper at night time except Friday night after work - you should have your battery fully charged with a mains charger before you leave.

PeterD

disco, it also depends on the depletion of the batteries if you happen to use them a bit as I do with ours overnight.

Mike, I was interested to know the thoughts on that and so appreciate your comments. It was what I thought was an interesting comment from a manufacturer with what I would believe a sizeable turnover of gear. I won't tell you which, but obviously not a neighbours gibbon or friend, or a Harding. I had asked him a particular question as I was interested in the demands of what I was looking at, bearing in mind my useage through an inverter cuurently. He gave me the specific reference to a Prado and the difficulty.

Glad you can charge the AGMs on the bench charger over two days, but when people have heavier discharge, they don't always have the opportunity to run their vehicle for that long..........

I'm surprised to hear you were talking directly to a manufacturer of AGM batteries in Oz? I didn't know there were any and they generally wouldn't sell direct. Or do you mean a distributor?

Perhaps you could ask whoever it was to supply a data sheet giving details of the required charging technique for their batteries and we could then comment or learn from that but until I see different in writing from a _manufacturer_ I'll stand by my previous comments.

Mike Harding

Mike Harding posted this followup
I'm surprised to hear you were talking directly to a manufacturer of AGM batteries in Oz? I didn't know there were any and they generally wouldn't sell direct. Or do you mean a distributor?

Mike please show me where? I did mention a manufacturer, I think you assume of batteries. I actually had mentioned C/T manufacturer in the other post, where the manufacturer wants to guarantee his product.

Yes Mike, I think there are potentially several problems including all the ones you mention. I had not thought of thos fridges as I have never had to think about them. I think we seldom actually know from day to day, hour to hour what is actually stored in our battery systems.

It actually arose after I asked a question. The 10mm sq cable I used to an Anderson plug and the Nissan alternator is capable enough as I understand. The Prado ws identified to me as having caused a problem to this particular C/T manufacturer.

"- Not recognising that you can't charge a WETCELL Deep Cycle in a four hour drive, even if you do feed it with 14.4 volts"
Yes Mike many push the theory that the average 4x4 can't charge a wet cell deep cycle but in reality that's certainly not the case. I run 2 x 115 amp hour Deep Cycle batts in parrallel in a diesel 105, start the engine with them, run the fridge, lights & winch regually & so far have lasted 3 years, have never let me down & only been put on a charger twice as a check to see if they where being fully charged. Even with short 1 to 2 hour runs into camp the batteries were still being charged to 90%+ giving me over 210 amp hour to use. When towing the van which has another 115 AH, still it has no issue bringing that up to 90%+charge in a 2 hour drive despite both the 3 way fridge & 73 litre Autofridge running. Why does my system work when most experts say it wont?............35mm & 16mm heavy duty cables & connectors, 50 amp Anderson plugs & NO fancy electronic battery management systems which IMHO don't allow proper charging when used in cicuits that include both deep cycle & regular starting batts.
Cheers Craig...............

Craig

Interesting - what manufacturer and model is each battery ?

mike

Trojan 27TMH.
In the past I have always run deep cycles together with the standard Toyota starting batteries, firstly using a Sure Power diode isolator which only lasted 2 years then on other cars joining both batteries together only isolating with a 200amp key switch as required. These rarely lasted more than 3 years. With hind sight I put this down to the batteries being under sized requiring me to flatten the 85AH deep cycles too frequently. I put my current system together as an experiment (against some expert advice). I was told by someone in the solar buisiness that the key to long battery life was to install batteries of the same age, size & construction & minimise discharging them below 30%. By installing 2 x 115amp Hour batts in parallel I have achieved almost 4 days running of the fridge & lights in up to 35 degree heat & still able to start the car. All this with no expensive isolator systems, solar panels or generators. I understand that it's unlikely the battery's will ever be fully charged (above 95%) particually after short trips but with so many amp hour to spare it doesn't really matter & now just over 3 years since fitting this doesn't appear to be affecting the life. Will be interesting to see how long they do go.
Cheers Craig........

Craig,

Your setup definitely sounds interesting and I'd like clarification on a couple of points.

1. Since you do not have any sort of isolator, how do you monitor/determine if your batteries are getting too low? Particulary too low to start the vehicle?

Do you have some sort of backup or do you always drive somewhere every couple of days whilst camping, therby eliminating the problem?

2. Would this system work in a vehicle that has an ECU? I have a 79 series turbo diesel and am in the process of deciding what dual battery setup to go with.

I know that with dissimilar batteries that I need to use something like a Redarc but not sure if this is still a problem if using identical batteries.

The general consensus on this site seems to be Redarc + AGM, which is what I had decided to go with until I read your post. Even though most don't see an issue with mounting an AGM battery under the bonnet, and many have done it, there still seems to be a slight question mark regarding excessive heat, as far as I can tell.

Regards,
Peter

Peter, most of my trips are touring not base camps stopping for no more than 3 days so I rarely bother to monitor the voltage other than out of interest with a multi tester. I did have a Jacar volt meter with low volt alarm but it packed it in after 4 weeks & never replaced it. As a back up you could install a simple (& cheap) low voltage disconnect switch on the fridge & light circuit but haven't bothered on mine yet. 6 months after I fitted the batteries I found out some of the Vic Police 4x4s had the same setup to run their winches & communication gear.
The one downside I have found is the need to regually check the electrolite levels as they normally need topping up 2 to 3 times a year. For a battery that is not supposed to be any good for starting, by cranking off 2 it spins the motor over very quickly. With no electronic isolater I can't see any problem with running on a vehicle with an ECU as in reality my system is just one big battery & Trojan apparently now make a 130 AH battery in the same case. With 260 AH even if you left 60 AH to start the car, it still leaves 200AH to run the fridge. In 25 degree heat some fridges could theoretically go a whole week:-)
I was also looking at fitting 2 AGMs but the cost v's the amp hours made it hard to justify, in fact I would have needed to fit 3 to match the capacity of the Deep cycles. The trade off is they do take longer to charge & if you don't regually drive the car or do like base camping I doubt this system would be as successfull.
I too have seen AGMs fail apparently due to the heat but was unaware it was a common problem.
As previously stated I'm still only trialing this set up but a few friends are now running the same, unfortunately it takes many years to see if it's actually reliable.
Cheers Craig.............

The Trojan 27TMH have a Cold Cranking Amps rating of 630 - so with two of them in parallel, there is plenty of reserve, which will help them to live for long.

Mike

Craig,

Thanks for your reply; helped to clarify exactly how you're using the setup you described. As I said, it definitely appeals to me and I think that is the way I'll go. I wouldn't have considered this option except for your post.

I like the idea of not having to install a battery isolator; keeps things very simple, as long as one is aware of the limitations. I believe that I can live with the limitations.

I was fairly certain that 2 identical batteries in parallel would not be a problem for an ECU but wanted confirmation.

So, once again, much appreciate the feedback.

Peter

Why would it not put out 80 watts when charging a battery?

Because an 80 watt Solar Panel can put out a MAXIMUM of 80 watts, but ONLY at a voltage of around 17 volts.

A solar panel at a particular level of illumination is a constant current source - at 17 volts it will put out 4.6 amps (80 watts), at 14 volts it will put out 4.65 amps (65 watts), at 7 volts it will put out 4.7 amps (33 watts), into a dead short it will put out 4.75 amps (zero watts).

Mike

Very interesting, Thankyou