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Old Oct 21, 2011, 08:35 PM
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Joined Jul 2004
270 Posts
Neptune SB-1 charge problems I have encountered and solved

I am posting this because someone PMed me and they have their account set up not to receive PMs. So here is my reply. and this is what "I" have encountered

Right. Well when you have no load on the battery after being charged with the supplied charger.the voltage would indeed read 12 v if the battery is fully charged the voltage would be 12 volts or 11.9 under a load,not 11V and when you ask the sub to move foward or draw in water, you will draw even more current then the voltage will fall at around 10 or lower. Had the same problem. When you have a battery that is 12 votls you need to rise above the threshold of that voltage to get it up to it's rated voltage, that is why an automotive electrical systems and devices are actually rated for 13.5 V since that is the true voltage in an automobile. Because the battery needs a volt or volt in a half to get it at 12 volts and have reasonable current flow at that voltage. SO My advice is to ditch the charger that came with it, get a motorcycle battery charger put bananna plugs on the wires to plug into the charging jacks. The motorcycle battery charger has much lower ampacity and won't charge that battery too fast. That is what i would do. I am using a powa caddy charger. Powa caddy is a powered golf bag cart. The battery is the same size as the neptune battery. The run time would be much longer if you take my advice. The charge would be only an hour. The slower the charge though the more the battery likes it. Also I would tighten the screw terminals and make sure the terminals on the battery are tight. If all tight then it is most probably a charge issue.
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Old Oct 23, 2011, 05:09 AM
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Joined Oct 2007
101 Posts
Good idea.
I agree that the fully charged voltage should be about 13,5V and not 12V.
Also the charger of my old Neptune was charging the battery up to 12,5V only.
But, to be honest, I checked a charger of a friend of mine, who bought this submarine recently. It seems that TT is now supplying a charger with better output, capable to obtain fully charged voltage of 13,5-13,6V.

There's just one thing I reccommend: don't charge the batt too fast.
I am surprised that your charging time is just one hour, unless this figure refers to initial and not to full charging operation.
If it really takes just one hour, it means that you are using 1C charging current, whis is too much for a lead batt (reccommended: 0,1C current).
If the current is too high, the battery may release a little amount of hydrogen, which is dangerous if contained in a small environment like this.
So, have a good ventilation of the WTC when charging and, if possible, use lower charging current (0,2-0,3A).
Charging will take more time, but safety always comes first.


Maybe I'm wrong. Did you write one hour charge meaning the charging time or the discharging time = endurance during use?
If so, I'm sorry. Please ignore my post.
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Old Oct 23, 2011, 07:40 AM
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USA, OH, cambridge
Joined Sep 2001
1,003 Posts
Some of these have bad batteries from the start. A friend got a new one with a bad battery and they sent a replacement which works great.

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Old Oct 23, 2011, 04:22 PM
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Joined Jul 2004
270 Posts
RIght. I forget how long it takes to charge the sub, when I had it at the regattta last year it took me about two hours to have the light on the charger switch to charged. IT is an automatic battery charger for that size of battery. I haven't run my subs since being in seminary I hope the batteries can take being idle for almost a year. I have one of them with me here in Wisconsin and want to run it before the winter sets in. Speaking of Wisconsin,,, any submariners here in the Milwaukee area? Thanks Tom.
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Old Nov 15, 2012, 04:58 PM
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Joined Nov 2012
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Is it normal that the charger only flashes for a second when you turn it on, and remains off ? Ive started my first charge and the charger light is OFF, and has been off (unlit) for about an hour so far.

Any tips to know when the charge is complete ? Does one need a voltage meter or something ? The QUICK START manual mentions something about checking the voltage but there are no lights or anything to look at...
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Last edited by mP1; Nov 15, 2012 at 05:03 PM. Reason: minor edit
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