Battery Charger Query

Submitted: Thursday, May 29, 2003 at 10:32
ThreadID: 5168 Views:3981 Replies:8 FollowUps:5
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Does anyone know of a Battery Charger that will charge and cut out on demand two 100 Trojan Deep Cycle Batteries running in Parallel? The idea is to hook this up to the Batteries and when I want to go away they will always be fully charged. I have just brought the Batteries and they were not fully charged ( I reckon about 50% ) and it took me days to charge them.
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Reply By: Dargo Mathews - Thursday, May 29, 2003 at 11:23

Thursday, May 29, 2003 at 11:23
Trojan deep cycle batteries are not designed to accept float charging.

Suggest you read the instruction sheet and technical information you should have been supplied with the batteries. From the supplied instructions you should have received it says "Periods of inactivity can be extremely harmful to lead acid batteries." It then goes on to tell you how to store, check and maintain Trojan batteries. Float charging Trojan batteries is not recommended.

Trojan batteries are more suitable to a constant use cycling application like connected to solar panels and a use supply like a shed/house/campervan.
Trojan batteries are not suited to auxillary battery occassional or emergency type use. You would be better off with a conventional lead acid deep cycle battery. This could be a case of where the battery supplier has sold you the incorrect battery type for your application.

If the batteries were only 50% charged, it proves the batteries from when they were filled with acid have not been maintained correctly in a stored state.
AnswerID: 21371

Reply By: David N. - Thursday, May 29, 2003 at 12:45

Thursday, May 29, 2003 at 12:45
Float charging at the correct voltage BETWEEN use won't hurt them at all- quite the opposite! What they are getting at is they don't recommend that continuously eg. month after month, year after year and as the SOLE means of recharging- it won't charge them properly. Any battery which is damaged from "float" is because the voltage is wrong...(too high.) For float the secret is to get the voltage down to the point where the battery is not gassing ie:losing electrolyte- needing regular topups. The voltage needed for float is a lot less than that needed for a proper charge. ( say 13.4 vs 14.2v )- but it varies depending on the battery and the temp. There's a huge amount of info available in some decent libraries, and no doubt on the web.
Certainly yes they should have been more than 50% charged- but sadly very few battery suppliers EVER charge batteries which have been sitting around for a while.
Best option is to buy your battery from somebody with lots of turnover ie: buy a battery which is new- not been sitting around for 6- 12 months.
As for chargers there are a huge range with auto cutout or you can buy the kit to modify a charger (available from DSE or Jaycar) With these kits you can adjust a variable resistor to get desired voltage.
You can also buy "3 stage" chargers but of course these cost more $$. You could have two chargers- one with some grunt to charge them properly and then one small one with a circuit to float it at the desired voltage. This works very well for me. (Have some very old deep cycle batteries still going strong!)
Hope this helps.
AnswerID: 21375

Follow Up By: Dargo Mathews - Thursday, May 29, 2003 at 16:47

Thursday, May 29, 2003 at 16:47
David N you need to read and digest the information sheets that comes with Trojan batteries for correct and proper charging and storage.

Battery suppliers like ourselves do not fill batteries till they are needed
If we do fill batteries and they sit around for longer than we anticipate we would then charge the units.

Our business only fills batteries that we are fairly confident of selling in the next 2 weeks
FollowupID: 13944

Reply By: Rod - Thursday, May 29, 2003 at 17:01

Thursday, May 29, 2003 at 17:01
From the Trojan Website:

'Trojan recommends using a 3-stage charger. Also called "automatic", "smart" or "IEI" chargers, these chargers prolong battery life with their well programmed charging profile. These chargers usually have three distinct charging stages: bulk, acceptance, and float.'

I recently bought a new Trojan Deep Cycle and was not supplied with a sheet. Thanks for the tip as I'll go back an ask for one as I can't find your advice on the website. I don't doubt you, I too want to do the best thing for the battery.
AnswerID: 21394

Follow Up By: Member - NOBBY - Thursday, May 29, 2003 at 19:12

Thursday, May 29, 2003 at 19:12
OK. Guys. Put the mouthguards away and shake hands. All I want to know is what do I use to solve my problem? How do I charge the two Trojans without taking them out of the trailer and doing them seperately?
FollowupID: 13950

Reply By: Peter - Friday, May 30, 2003 at 11:44

Friday, May 30, 2003 at 11:44
Look at a WACO MBC 800 series It is a switched mode (Like in a PC) power supply and has a 8AH continious charge rate. When battery is charged to 95 %, it goes into float mode.
the peak voltage is 14.1
Thes are available from batteryworld shops. Call Waco for more info
They are about 100 dollars
I would recomend a high current plug and socket wired to battery and charger so to get rid of gater clamps

AnswerID: 21452

Reply By: Member - Nigel - Friday, May 30, 2003 at 23:15

Friday, May 30, 2003 at 23:15
Buy the highest amperage fully automatic charger you can afford. Many cheap ones tend to overcharge when they have supposedly switched themselves to float.

If your batteries are 200 Ah then it will take a small charger a long time to switch to float.

I use a LEAB and find them good. As well as all the programs and sensing, they will switch to float after 24 hours if they haven't already to avoid cooking the batteries.
AnswerID: 21491

Reply By: Wazza (Vic) - Saturday, May 31, 2003 at 01:43

Saturday, May 31, 2003 at 01:43
For your interest, check out:

and their catalogue:

I use the AC250B to keep both batteries charged on the car while I am away. (I work a rotation of 6 weeks at sea and 6 weeks break). Both batteries are Exide Extremes (ie, I know they are not Trojan deep cycles), however their catalogue may be of interest to you. Cost me $60 at Autobarn, however K-Mart had them a bit cheaper at $55. I get my housemate to flick a switch every weekend that changes the charge from main battery to accessory battery and vise versa, so they are only connected half the time. Had problems with the starting battery being flat every time I came home. ARB replaced battery under warranty, even though technically my fault for letting them discharge too far.

Works for me.

AnswerID: 21498

Follow Up By: Member - NOBBY - Sunday, Jun 01, 2003 at 19:25

Sunday, Jun 01, 2003 at 19:25
Thanks for that info. That is what I wanted, not all the scientific stuff.
FollowupID: 14068

Reply By: Member- Rox - Tuesday, Jun 03, 2003 at 18:22

Tuesday, Jun 03, 2003 at 18:22
Nobby Batteries best charge is 10% so 200amp will need 20 amp charger to be best eficent. try 12 volt shop, I just bought 1 and it can be left on perment charge till you go away. (3 stage charge)Around Oz 06/2004
AnswerID: 21750

Reply By: -OzyGuy- - Sunday, Jun 08, 2003 at 12:26

Sunday, Jun 08, 2003 at 12:26
The simple answer is use a Projecta "charge controll BM140" connected to a projecta "Trademsman" battery charger, total cost would be about $140 from K-mart. The batteries remain wired in parallel and will trickle charge at 13.2 volts or 13.6 if the gell switch on the BM140 is used. Connect Positive lead to the first Positive post and Negative lead to last negative post.
AnswerID: 22065

Follow Up By: Member - NOBBY - Sunday, Jun 08, 2003 at 18:06

Sunday, Jun 08, 2003 at 18:06
OzyGuy.. Thanks for that info. Unfortunately it's a case of " to late she cried". I rang Projecta with my "problem" and they said that the only solution they had would cost about $600. I then rang a mob in Bris called Com-pak that make Battery chargers and they put me onto a charger that puts out 15amp on demand and costs $195. Said this would charge both batteries and cut out when same are full. I bought one and am waiting for the things to go flat so I can give them a squirt. I charged them full with a Christie Gen set. Thanks for the response..
FollowupID: 14503

Follow Up By: -OzyGuy- - Monday, Jun 09, 2003 at 13:24

Monday, Jun 09, 2003 at 13:24
Hi, I have recieved an E-mail from Projecta confirming that the "BM140" will do the job of monitoring both 'lead acid & gel batteries' when wired in parallel, with an initial charge of 14.4 volts and then maintaining the battery voltage at the levels I have stated above, I use this system.
FollowupID: 14520

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