Battery charging gurus

I have a requirement to use two normal starting batteries every 2 to 3 months for about 3 hours to power 12V motors on two separate machines that are remote from the building. Batteries will not be flattened.

240V power to operate a battery charger is only available one day each month. I would keep the barreries connected to the charger so that it will turn on when we turn on the power to the building.

What would be a suitable charger to keep these batteries in top condition?

Can I charge both batteries from one charger?
Happy 4 wheeling

Woodsy

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Reply By: Bigfish - Sunday, Jun 14, 2015 at 09:51

Sunday, Jun 14, 2015 at 09:51
Why not use a small solar panel and regulator? No need for 240 volts and will trickle charge whenever there is some sun.
AnswerID: 555938

Follow Up By: Member - ACD 1 - Sunday, Jun 14, 2015 at 10:00

Sunday, Jun 14, 2015 at 10:00
x 2 on Bigfish' reply.

I have a cheap battery maintenance "solar charger" from SupercrP that charges the emergency generator battery. Works well, never had a flat battery yet.

Cheers

Anthony
VKS 3539
Work - a 40 hour interuption to my weekend!
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Follow Up By: Roachie.kadina.sa.au - Sunday, Jun 14, 2015 at 14:27

Sunday, Jun 14, 2015 at 14:27
Ditto here.... I have a pair of batteries from my Landcruiser which, whilst still okay when I removed them a couple of years ago (when I fitted a 270 amp alternator to it, I decided to treat it to 2 new batteries as well).

The 2 "old" batteries were consigned to my shed for duties such as running a 14" Davies Craig extraction fan on a model paint booth and the other one provides power to my model railway's point motor solenoids. As such they don't get used regularly or for long periods of time; nor is the current draw very high even when they are being used.

I have a (supposedly) 120 watt fold-up solar panel that I bought with the idea of taking camping....but we rarely go much these days.

I have equipped both batteries (which are located in different areas of the shed) with an Anderson plug and small digital voltmeter. The solar panel is also fitted with an Anderson plug and I simply monitor the voltage in the battery which isn't connected to the solar panel and move from one to the other when I see that it has gotten down to about 12.6v. The one that IS connected to the panel usually shows around 13.7v.

I don't bother moving the solar panel during the day....it simply lives in one spot and I move it to another part of the outside of the shed when I want to charge the other battery.

Costs me nothing to keep both batteries "right" all the time.
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Reply By: Peter_n_Margaret - Sunday, Jun 14, 2015 at 18:21

Sunday, Jun 14, 2015 at 18:21
Any good quality 3 stage charger that is set to the battery chemistry would be fine to charge both batteries together.

Cheers,
Peter
OKA196 Motorhome
AnswerID: 555952

Reply By: Member - Woodsy - Sunday, Jun 14, 2015 at 19:42

Sunday, Jun 14, 2015 at 19:42
Thank you all so far for your ideas.

The solar system could be an option. I will follow that up.

The batteries would be left unattended for at least 4 weeks and up to 7 weeks at a time so any system has to be reliable and 'bulletproof'.

I am still open for more suggestions and ideas.

I would prefer to have a quality system rather than a Supercheap type system, or am I being biased?
Happy 4 wheeling

Woodsy

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Follow Up By: AlbyNSW - Sunday, Jun 14, 2015 at 21:17

Sunday, Jun 14, 2015 at 21:17
Solar sounds like the go or have you considered a different battery type like AGM or Cad etc that can sit unattended for long periods of time without self discharging
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Reply By: brendan l4 - Sunday, Jun 14, 2015 at 21:46

Sunday, Jun 14, 2015 at 21:46
I'm a solar/off grid installer and i agree that solar will be your best option, if you have good sun exposure. Especially if you're only running your load every 2 or 3 months solar will keep your batteries constantly topped up and therefore keeping them in good condition.10 amps of solar minimum for 2 batteries and a good regulator will do the job.

And yes if your 2 batteries are connected to each other they will both get charged.
AnswerID: 555967

Follow Up By: Sigmund - Monday, Jun 15, 2015 at 15:10

Monday, Jun 15, 2015 at 15:10
Though connect to +ve on one and -ve on the other in that case.

If you are yet to buy the batteries take a look at ACDelco Calcium hybrids; they will serve as starter and deep cycle batteries.
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