Maintaining dual battery set up when rarely driver?

[Jonesy_sa]

Hi guys,

Sometimes the Maverick doesn't get driven for a few months - resulting in dead batteries. It currently has dual batteries with a simple isolator solenoid and it appears the auxiliary battery only powers a socket in the rear.
I noticed SCA have cheap solar chargers however I would still need two, one for each battery, I have read over the forums regarding solar of which most focuses on heavy users with fridges etc. I would prefer not to have my batteries connected to a mains trickle charger 24/7 plus I would still need to rotate between batteries I think.

Is it possible and sensible to have a permanent charger powered by solar that would monitor the batteries for extended periods? If so what would I need? I'm happy to permanent mount a panel on the shed roof if need be.

[megatexture]

If your willing to keep the car plugged in (solar or 240) i would just get a 240v trickle charger and put a manual link switch between the positives and it will maintain both batteries when linked, It would cost bugger all to maintain 2 batteries on 240v and a small charger would cost peanuts .Alternatively the same could be done with a solar panel and reg maybe 40watts? You wouldnt need much.

link the batteries and maintain them as one.

[MudRunnerTD]

I'd be tryin to figure out what is draining your system or replace your batteries. You should be able to park it for a Year and not have dead batteries, I certainly can.

Trickle charge would work fine but there are other issues I reckon.

[megatexture]

There could be an issue but A battery will also naturaly discharge, even some of the agm I looked at recently were 3% per month and the older they are the higher it will be

[Jonesy_sa]

Ideally I would like to keep the batteries in the car and connected. The only items constantly on is the digital clock, flashing led for alarm. There might be something else but I haven't found it.
I like the solar idea as I could always buy a larger panel at a later date if touring.

[Cuppa]

Three things.

The self discharge rate of wet batteries is far higher than AGM’s.

Solar trickle charging is a good idea, need to ensure more going in than is going out. Check clock etc, & ensure no phantom loads.

Connecting solar just to start battery will keep both batteries charged provided they are fully charged when you park the vehicle up for a few months (put on mains smart charger first).

Note. It would still be wise to check battery fluid in wet batteries now & again when in ‘storage’.

[Throbbinhood]

Do 240v chargers charge at 13-14ish volts? Just wondering if I connect it to my main, if it will produce enough voltage to enable the dual battery solenoid and charge both at the same time. Save me mucking around setting up an override.

[BillsGU]

I have had trickle chargers on both the motor bike and the ride on mower for many years without a problem. A trickle charger is much cheaper than a battery so they pay for themselves in a very short time.

If it were me (solar or 240 V) I would use two chargers. Charging batteries in parallel is not the best way to go because the battery that has the higher charge gets more current than the lesser charged battery and because most chargers are voltage sensing the flatter battery may never be fully charged. I'm not saying it won't work but it is not ideal.

[Cuppa]

. Charging batteries in parallel is not the best way to go because the battery that has the higher charge gets more current than the lesser charged battery and because most chargers are voltage sensing the flatter battery may never be fully charged. I'm not saying it won't work but it is not ideal.

Once the battery connected to the charger reaches the threshold voltage of the VSR (solenoid) & the two batteries become connected, the voltage between the two batteries equalises & the charger views the two batteries as a single battery. Provided the cables between the two batteries are of sufficiently heavy gauge & the two batteries are of similar type, capacity & age I can’t see there would be any problem at all. Even if all those criteria were not met, charging them in parallel via a trickle charger would still be a massive improvement on the current battery killing arrangement.

[Cuppa]

Do 240v chargers charge at 13-14ish volts? Just wondering if I connect it to my main, if it will produce enough voltage to enable the dual battery solenoid and charge both at the same time. Save me mucking around setting up an override.

Yes that will work fine. As per previous post, best if both batteries are of similar size,age, & type, but not critical. I charged a bank of 24v AGM’s paralleled to a bank of 24v wet starter batteries with no problem. The starter batteries lasted me 5 years (would have lasted longer, but I ommitted to check fluid for several months & they dried out!). The AGM’s were still going strong at 8 years old when I sold the vehicle recently. They spent several years total connected to a mains smart charger, as well as significant periods in daily use charged via alternator & solar.

[Throbbinhood]

Yes that will work fine. As per previous post, best if both batteries are of similar size,age, & type, but not critical. I charged a bank of 24v AGM’s paralleled to a bank of 24v wet starter batteries with no problem. The starter batteries lasted me 5 years (would have lasted longer, but I ommitted to check fluid for several months & they dried out!). The AGM’s were still going strong at 8 years old when I sold the vehicle recently. They spent several years total connected to a mains smart charger, as well as significant periods in daily use charged via alternator & solar.

Thanks. Off to buy a charger haha

[the evil twin]

Hi guys,

Sometimes the Maverick doesn't get driven for a few months - resulting in dead batteries. It currently has dual batteries with a simple isolator solenoid and it appears the auxiliary battery only powers a socket in the rear.
I noticed SCA have cheap solar chargers however I would still need two, one for each battery, I have read over the forums regarding solar of which most focuses on heavy users with fridges etc. I would prefer not to have my batteries connected to a mains trickle charger 24/7 plus I would still need to rotate between batteries I think.

Is it possible and sensible to have a permanent charger powered by solar that would monitor the batteries for extended periods? If so what would I need? I'm happy to permanent mount a panel on the shed roof if need be.

I know you mention a preference against mains power charging but...
Simplest easiest cheapest solution is a CTEK MXS 5 Charger $90 (or equivalent).
Connect to either battery or plug the output in anywhere, even the socket in the back.
If you have a capacity around 160 AH or less flick the isolator on.
The CTEK will draw minimal mains power and will keep the batteries in much better nick than the el cheapo solar stuff.

If you have two large capacity batteries then desulphate and charge the Aux and leave the Isolator open when teh vehicle is laid up.

Total cost around $100 and you have a quality battery charger as well

[Hodge]

So, I have a 105AH agm as my dual battery. The battery is in the car, 100% of the time, and hooked up to the redarc bcdc. The only time battery gets used is during camping for fridge/lights etc... The rest of the time it just sits there topped up by the charger and no juice being sucked at all. Which is most of the time...

So, in a nutshell....
If I simply disconnected the battery and the charger, and pulled the battery out of the car and leave it in the garage, until I DO go camping... It's bad for the battery right ??? And going by some comments in this thread, I'd have to hook it up to some type of charger in the garage to keep it topped up / maintained??


This would save me lugging around 35KG under the bonnet for nothing, as well as save the battery, being battered by the turbo heat for no reason.

[the evil twin]

I would have absolutely no issues with leaving a fully charged AGM in a shed and maybe giving it a hug once every month or two or even three for 24 hours with a quality charger.

FWIW I only charge the AGM's at work every 3 to 6 months and then only if the rested terminal voltage is down a couple of points (I write the values on the batteries with a Texta).

They are in a relatively cool spot and sometimes spend a year or two between deployments.
They last 5 to 10 years

[Jonesy_sa]

Once the battery connected to the charger reaches the threshold voltage of the VSR (solenoid) & the two batteries become connected.
Many thanks for the replies. I could be wrong, and I don't know much about battery isolators, however I was told the solenoid only operates when the ignition is on for my vehicle; It was installed in the early 90's.
My batteries are different however im not sure how much of an issue it is? The main battery is a SCA Marine 560cca:
http://www.supercheapauto.com.au/online-store/products/SCA-Car-Battery-N70ZZL.aspx?pid=293208&menuFrom=40602#Recommendations
The auxiliary of the top of my head is a Supercharge 250-390cca (I remember it being about half the main when I charged it) and it is Calcium type.

Due to the cost of batteries I am happy to invest in a better isolator or permanent mounted charger for solar. What would be required for a solar set up that Is used for charging, however with the possibility to expand later?

[the evil twin]

Many thanks for the replies. I could be wrong, and I don't know much about battery isolators, however I was told the solenoid only operates when the ignition is on for my vehicle; It was installed in the early 90's.
My batteries are different however im not sure how much of an issue it is? The main battery is a SCA Marine 560cca:
http://www.supercheapauto.com.au/online-store/products/SCA-Car-Battery-N70ZZL.aspx?pid=293208&menuFrom=40602#Recommendations
The auxiliary of the top of my head is a Supercharge 250-390cca (I remember it being about half the main when I charged it) and it is Calcium type.

Due to the cost of batteries I am happy to invest in a better isolator or permanent mounted charger for solar. What would be required for a solar set up that Is used for charging, however with the possibility to expand later?

Solenoid -
I am guessing it is just a straight out solenoid with no smarts if that is the case
Nothing basically wrong with that idea.

Aux Battery -
Because your Aux is a Calcium I would invest in a DC/DC charger with onboard Solar Reg.
A smart Isolator like the SBI12 etc will work but a DC/DC will be better for the Ca battery and also allow you Solar in the one box

Setup -
1. If I am correct find the switching wire to the Solenoid that is powered when the IGN is on, cut it and put a switch in it (on the dash or underbonnet is up to you. This switch will normally be Off
2. Leave the heavy battery size cables to the existing solenoid as they are.
3. Mount the DC/DC charger as per manuf instructions for a Ca/Ca Battery

That will mean your Calcium Aux gets optimum charging under normal operations and at the flick of the switch the "old" solenoid will pull in and parallel your Aux to the Cranker if you are winching or want to jump start or whatever.

You can pull the old gear out if you wish, totally up to you

[Jonesy_sa]

Setup -


I can see how this would charge the Aux via solar however how would it maintain the Start battery too?

Do the Redarc BCDC1225/1220 etc charge both the Start and Aux? The diagrams suggest the start battery is maintained by the alternator and the Aux is maintained by the alternator or solar via the Redarc?

[the evil twin]

I can see how this would charge the Aux via solar however how would it maintain the Start battery too?

Do the Redarc BCDC1225/1220 etc charge both the Start and Aux? The diagrams suggest the start battery is maintained by the alternator and the Aux is maintained by the alternator or solar via the Redarc?

It won't... you are mixing battery technologies so there is no single device solution.
The chargers need to run at different settings for the standard and calcium batteries

The Mains Charger will look after your Cranker and the DC/DC charger will look after the Calcium

[megatexture]

The Mains Charger will look after your Cranker and the DC/DC charger will look after the Calcium

This would depend on what the voltage on the crank battery is as to if the bcdc will remain connected to the aux once charging finishes and float begins, to low a voltage and it will disconnect and only maintain the crank and not the aux.
hence the manual switch I mentioned earlier.