Voltage for charging Exide Nautilus batteries (with solar) - Dutchmen Owners

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Old 01-13-2012, 04:20 PM   #1
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Voltage for charging Exide Nautilus batteries (with solar)

I am putting together a solar charging system for our TT. I'll be using a Morningstar Tristar PWM 45A charge controller. I'm not very knowledgable regarding battery charging, but I have read a lot online about the importance of the voltage level during the absorption stage for achieving full charge and the "standard" of 14.4V seems to be generally accepted as too low for flooded cell batteries. 14.8V is a number thrown around, especially since Trojan 6V golf cart batteries apparently recommend this level. Interstate Batteries recommend 15.5V. Advice is always "contact the battery manufacturer". Well I've been trying, and searching the internet, but I don't have an answer yet for what voltage my two NC-24 Exide Nautilus batteries should be charging at during the absorption phase. Can anyone tell me? Without any other input, I think I'll set things up at 14.8V since I don't know of a difference between these batteries and other deep cycles. Thanks.

Exide Nautilus Dual Purpose. Part Number NC-24

Info found here http://www.exide4u.com/exide/JSP/mas...g/ser_tips.htm
is for Industrial Exide batteries and they throw around a value of 2.75 VPC (volts per cell?). Does that suggest 2.75 * 6 = 16.5 volts? That sounds too high. The Tristar doesn't even seem to be able to be set that high anyway (15.0V max with the built in algorithms)

Interstate Deep Cycle batteries. http://www.batteries-faq.com/activek...p?questionid=1
What does C/10 mean?
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Old 01-13-2012, 09:15 PM   #2
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Re: Voltage for charging Exide Nautilus batteries (with sola

C/10 means charge at 1/10th the capacity, (3000mAh at 300mAh, 2400 mAh at 240mAhs).

Forget all you've read.
I'd do a 10 amp charge for 14 hours on a battery pack(multiple batteries) and a 10 amp 6-8 hour charge on a single battery.

From the web:
Do a C/10 (c = capacity i.e. 2400mAh pack is charge 1c at 1.2A) charge for 14-16 hours, the magic of "slow charge" is that it equalizes the cells. As the cells fill up some will get full before others, but at the C/10 rate there is no danger of over charging because the cells that are full can safely dissipate the "over charge" as heat, without damage, giving the other cells time to fill up. This is also why it's a good idea to occasionally C/10 charge all your packs, in normal use over a number of cycles they will start to become unbalanced and the C/10 charge will rebalance them.

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Old 01-13-2012, 09:58 PM   #3
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Re: Voltage for charging Exide Nautilus batteries (with sola

Thanks for explaining C/10. My Exide Nautilus are rated at 70 Ah each, wired in parallel for 140 Ah capacity. C/10 = 14 Ah?
I'm not sure how this fits in to my absorption charging voltage with the solar controller question.
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Old 01-17-2012, 11:32 AM   #4
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Re: Voltage for charging Exide Nautilus batteries (with sola

12 volt panels actually put out about 17 volts in full sun. In Montana in the winter, you won't have much daylight, so you need more wattage. Your charge controller will supply what voltage the battery needs (whether charging or maintaining) - it will also prevent the panel from draining your battery when it is dark.
Here in South Carolina, I can charge and maintain my batteries with 60 watts. Now that it is winter, I have to use 120 watts to keep them up (they are mainly in shade the first part of the day). Not sure what you will need.
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Old 01-17-2012, 12:06 PM   #5
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Re: Voltage for charging Exide Nautilus batteries (with sola

Quote:
Originally Posted by nelsonjo
12 volt panels actually put out about 17 volts in full sun. In Montana in the winter, you won't have much daylight, so you need more wattage. Your charge controller will supply what voltage the battery needs (whether charging or maintaining) - it will also prevent the panel from draining your battery when it is dark.
Here in South Carolina, I can charge and maintain my batteries with 60 watts. Now that it is winter, I have to use 120 watts to keep them up (they are mainly in shade the first part of the day). Not sure what you will need.
Thanks for the reply, Nelsonjo. I'm actually not looking for how much wattage I need or nominal panel voltage, but for what voltage to set up as the absorption setpoint on the controller. The controller will supply the voltage that its algorithms tell it to and a solar controller with a 3-stage charging process will start by delivering all the available current (bulk charge) until the batteries show a certain voltage level. This is the absorption setpoint. Then the controller holds the voltage level at the absorption setpoint and begins to taper off the current until charging is done. Then it switches to maintenance/float. If the controller allows for adjusting that absorption setpoint (mine does, Morningstar PWM Tristar), then setting it to what the particular battery manufacturer recommends will get you maximum battery performance. At least that's what I'm told, I'm still building my first system...
I'm starting with a single 140 watt panel and I'm overbuilding the rest of the system to allow for future expansion.
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