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Originally Posted by hingarfi
I just bought a 2004 3023 with the Parallax 7300 converter. I will mostly be boon docking so I installed 2 golf cart batteries (225AH) on the A frame. My goal is to recharge in as short a time as possible. I am not considering solar panels but will buy 1KW "quiet" generator. I plan on adding the Progressive Dynamics PD9145 or PD9160 with the Charge Wizard. There is #10 wire from the battery back to the converter.
(1) Does anyone have an opinion on how difficult it would be to replace this #10 with #6 or # 8 wire? I am talking about the difficulty of physically pulling the wire in tight spaces.
50 feet of #6 has about 0.02 ohms. 50 Amps would see a voltage drop of about 1 Volt. The PD allegedly puts out 14.4 volts initially so the battery would only see only 13.4 V
(2) Seems this voltage drop would prevent the PD from charging at the 50 Amp rate for any significant length of time. Your comments / experience will be appreciated.
My gut feeling at this time is to:
Leave the Parallax 7300 as is.
Buy the PD9145, connect it directly to the battery with 2-3 feet of #4 booster cable with alligator clips and plug it into my 1KW generator. Then the PD can do its thing charging the battery intelligently. Since this unit is housed in my garage, this arrangement seems feasible during storage.
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As Bob notes above, true deep cycle batteries should
never be charged at a rate higher than 20% of the rated capacity and are best charged at rate that's about 10% of their rated capacity. That converts to about 45 amps maximum and around 23 amps optimum. The problem is true deep cycle batteries have very thick plates...that thickness leads to long lifespans but also severely restricts the amount of electrical/chemical exchange with the surrounding electrolyte. Very high charge rates will likely cause damage to the plate structure that in turn will greatly reduce the battery's capacity. Same thing on discharge...deep cycle batteries should not be subjected to more than momentary high discharge currents (over about 20% of their capacity). By comparision, automobile batteries (which are primarily designed to provide very high currents for starting) have very thin plates and
can safely accept high rates of charge (100 amps plus). The bottom line is a high rate of charge (preferred because it greatly reduces charge time) that's fine for an automobile starting battery would be very damaging to a true deep cycle battery.
Therefore, since 40 amps is about the highest safe charge rate you should subject the batteries to (and 20 to 25 amps would be much better), I would strongly recommend that you simply leave the existing TM wiring alone since a 10 Ga wire is more than sufficient for 40 amps. Also consider that battery voltage gradually rises to around 13 volts during charging...and that alone will cut the charging current to around 20 to 30 amps anyway.
Personally I'd just replace the Parallax unit with the PD and let it intelligently handle charging of the battery from its position in the TM power center. Then simply plug the TM's shore cable into the generator.
As a point of reference, I'm still happily getting by with the old 6300 series converter in my trailer...despite it's relatively small 8 amp battery charging section. I've thought about retrofitting a 7300 series or a PD converter but simply haven't seen a need even though I do have dual Golf Cart batteries. The reason is that my solar panels provide enough power every day that the batteries never go much below 70% charge even after 3 to 5 days of boondocking...and usually are back to 100% of charge by early afternoon every day. And even if I have several days of cloudiness, one overnight at a campsite with an electrical hookup is enough time for the 6300 to bring the batteries back to full charge. After 4 camping seasons, I've learned that the TM's water limitations (mostly waste water and potentially the toilet) tend to make boondocking for more than 2 or 3 days at a time a bit of a hassle. So I no longer really even plan to stay at one boondock campsite for more than 3 or 4 days at a time.
If you're going to be mostly camping where sunshine is fairly common and the campsites are not very shaded, solar is much better for battery recharging than a generator. The reason is that solar's typical low (10 to 20 amps depending on array size) but
steady current is an ideal match with the optimum recharging current requirement of deep cycle batteries.