Charging an 18Amp Hr battery
Submitted: Tuesday, Apr 12, 2011 at 21:20
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Drew - Karratha
G'day everyone
I am after a bit of advice... In a few days I am heading up north with a few mates on a fishing / dive trip. We will be heading out in the boat and staying on an island for about 5 nights. One of the guys has bought an 18 amp hr battery to run a flouro light off each night (the flouro draws .75 amps). I was intending on making up a lead with alligator clips on each end and just connecting the 18AHr battery to the boats starting battery to charge it as we are driving around each day - will this work (it is a 90hp Yamaha 2 stroke - if this makes a difference??).
I do have a small Projecta 300W inverter that I am taking to charge camera batterys, and have a Purecharge 3 stage battey charger - that I wasnt intending on taking (8 Amp I think). If the first idea doesnt work - would the charger run off the 300w inverter???
i have spent enough on the trip already - so arent keen on spending any more if possible........
Thanks heaps
Drew
Reply By: Notso - Tuesday, Apr 12, 2011 at 22:03
Tuesday, Apr 12, 2011 at 22:03
It should be right to charge it from the boat system. You would need to make sure it was all secure etc, you don't want cables coming loose and shorting out etc.
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Follow Up By: Drew - Karratha - Tuesday, Apr 12, 2011 at 22:14
Tuesday, Apr 12, 2011 at 22:14
Thanks, I am a bit concerned by that - maybe include an inline maxi-blade fuse (beacuse I already have one in the shed)??
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Follow Up By: Member - Boobook - Wednesday, Apr 13, 2011 at 08:33
Wednesday, Apr 13, 2011 at 08:33
Drew, as per Notso's reply, it will work fine, just make sure the connections are reliable and secure. I do this in my 4wd. I have made a connector on the battery, with a mate on the main battery ( you boat battery) and the light system so you can plug it into the boat to charge and plug it into the lights to use it. Croc clips etc will be a pain and unreliable. It is worth the extra effort to make it "plug and play" so to speak.
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Follow Up By: Mike DiD - Saturday, Apr 16, 2011 at 14:05
Saturday, Apr 16, 2011 at 14:05
Keep in mind that a short from EITHER battery will cause heavy current to flow which could set the insulation on fire or spew out globs of molten copper.
You really need fuses as close as possible to EACH battery positive terminal.
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Reply By: ABR - SIDEWINDER - Wednesday, Apr 13, 2011 at 07:52
Wednesday, Apr 13, 2011 at 07:52
Make sure you don't leave the inverter connected to the boat battery as it can drain the battery overnight.
Your priority should also be to keep the boat battery fully charged.
Regards
Derek from ABR
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Follow Up By: Drew - Karratha - Wednesday, Apr 13, 2011 at 22:28
Wednesday, Apr 13, 2011 at 22:28
Thanks Derek - I will make sure I remove it as it wouldnt be ideal to wake up with a flat battery - pull starting the 90hp is hard work!!
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Reply By: Robin Miller - Wednesday, Apr 13, 2011 at 10:47
Wednesday, Apr 13, 2011 at 10:47
Those Gel cells types suffer from to fast a charge easily Drew so take care.
Typical inital inrush current is only around 5 amps else bubbles form under gel limiting contact with plates and they degrade.
If it wasn't used much you may be ok , but I always reccomend charging thru something that limits this peak current.
Even a 0.47 to 1ohm 10watt resistor will do or a long piece of thin cable.
Don't leave on to long either as they are a bit touchy with over 14.5 volts.
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Follow Up By: Drew - Karratha - Wednesday, Apr 13, 2011 at 22:30
Wednesday, Apr 13, 2011 at 22:30
Thanks Robin - would a smaller inline fuse help?
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Follow Up By: Member - Boobook - Thursday, Apr 14, 2011 at 07:01
Thursday, Apr 14, 2011 at 07:01
A smaller fuse wont help what Robin is talking about. But chek the specs on the outboard, I doubt if it could put out much more than 5 A especially when the battery is is parallel to the main battery.
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