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Old 08-21-2016, 05:15 PM   #21
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hidee ho

Thanks Herk for the response! I was really concerned about putting cable from the + of one battery to the - of the other. Happy Camping!
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Old 08-21-2016, 07:18 PM   #22
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It can get confusing with 4 batteries as the orientation can get you turned around. I suggest connecting the "interconnects" first so you have two 12 volt banks; then connect the two banks together; then the positive from the camper to one set; and finally, the chassis ground to the negative of the other set.
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Old 08-21-2016, 07:31 PM   #23
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If there is an active load on the circuit when you connect the batteries, you will get a spark no matter which terminal ( + or -) you connect last. The main reason for connecting the negative ( ground terminal) last is to prevent a major arc should the wrench you are using to tighten the connection touches the frame or other grounded metal part.
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Old 08-21-2016, 07:56 PM   #24
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If there is an active load on the circuit when you connect the batteries, you will get a spark no matter which terminal ( + or -) you connect last. The main reason for connecting the negative ( ground terminal) last is to prevent a major arc should the wrench you are using to tighten the connection touches the frame or other grounded metal part.
Good answer, just a little clarification. The main reason for connecting the negative terminal last is to prevent a major arc should the wrench you are using to tighten ( one of the positive terminals ) touches the frame or other grounded metal part.

Without the ground(s) attached if you are tightening one of the positive terminals and your wrench touches ground while still connected to the positive terminal nothing happens because there is no complete circuit.

In the two six volt battery graphic both negative terminals must be connected last to prevent an accidental shower of sparks.
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Old 08-21-2016, 08:43 PM   #25
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In the two six volt battery graphic both negative terminals must be connected last to prevent an accidental shower of sparks.
Just the bottom battery negative. There is not complete circuit until the wire to the frame is made.
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Old 08-21-2016, 09:03 PM   #26
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Just the bottom battery negative. There is not complete circuit until the wire to the frame is made.
The caveat here is that, if the bottom negative is not permanently attached to the jumper cable with both cables in one sta-kon lug then yes only the bottom.

However if it is permanently connected then be carefull!!
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Old 08-22-2016, 10:44 AM   #27
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I was at that seminar too and also have six 6VDC batteries in a series~parellel configuration. My converter is the Progressive Dynamics 90 amp unit so I was concerned when the presenters said there was a problem. The next day, I spoke with Gary Bunzer and asked him about it. Gary said he was not aware that there was the problem that Brian & Drew claimed. Brian & Drew state that 6VDC batteries actually only deliver 5.5VDC per battery so, two of them wired in series give 11VDC. The Progressive Dynamax unit drops into its' heavy charging mode when the battery voltage drops between 10.75 ~ 11 VDC. The result is that the battery cooks off water because of the frequent heavy charging cycles. When I had my 6VDC system installed, I also had the easy watering system installed. My system does need to have water added periodically but, how often is too often? Greg, the service tech at Dynamax, was not aware of any problem with the Progressive Dynamax unit when used with 6VDC batteries. I guess I'll have to get in touch with Progressive Dynamax and get information straight from the source.

At last year's seminar, Brian & Drew stated that Simple Green cleaner damages the membrane in HepVO one way valves. Gary Bunzer was not aware of that tidbit either. I now have to wonder about the validity of what Brian & Drew say.
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Old 08-22-2016, 01:27 PM   #28
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Brian and Drew are flat out wrong about 6V batteries. Two 6V batteries have the same number of cells as a 12V battery - which determines voltage.

They are free to come measure my 6V batteries, which always measure 12.7 to 12.8V when fully charged.

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Old 08-22-2016, 03:20 PM   #29
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I had a long talk with Drew & crew about 6 vs 12V batteries and they came up with the stupidest reason I've ever heard.

" If you have two 12v batteries and one shorts out, you will still have one working battery until you can get the bad one replaced."

Two obvious errors with this quote:
1. Batteries should be matched - definitely not one well used one and one new one. (After replacing the shorted battery.)
2. If a cell shorts in one of a pair of parallel batteries, the shorted cell will cause the good battery to fully discharge through the bad battery's shorted cell. Once the good battery is fully discharged, you'll need a few hours of charging to determine which one is bad. You'll probably end up replacing both batteries anyway - see #1 above.

RV house batteries for many units are actually marine hybrid batteries. I believe the ones that FR installed in my 2011 Georgetown are actually only around 85AH, if discharged at 10% of capacity rate, the traditional way of testing deep cycle batteries. Most deep cycle batteries today are discharged at a 1AH rate to determine the capacity to improve the marketing numbers for the battery.

Reserve capacity in minutes for 12V hybrid batteries is the amount of time for a fully charged battery that's lost its surface charge voltage to be discharged to 10.8V with a 25A load on it. It's the only number on the battery that's useful for comparing the capacity of different batteries - assuming the manufacturer hasn't cheated on the test.

Golf cart batteries reserve capacity numbers are determined in a similar manner but with a 75A load. To compare the reserve capacity of a golf cart battery to a marine hybrid one, the golf cart reserve capacity time needs to multiplied by at least 3, and somewhere between 3.1 and 3.3 may be a better multiplier because there's more losses inside the battery as the current draw rate increases.

Golf cart batteries have solid lead plates, best for extended service without the high current draw capacity needed to run a starter motor. They're also more resistant to damage when subjected to deeper discharge cycles than batteries with grid type plates (starting and hybrid types).

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Old 08-22-2016, 04:27 PM   #30
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So far all I read is nonsense. Perhaps they were misunderstood. Lead acid batteries are made of individual cells, 3 in a 6 volt battery, 4 in an 8 volt battery and 6 in a 12 volt battery. A lead acid cell measures 2.1 volts when fully charged and under no load.

Now 2-6 volt batteries have 3 cells in each case for a total of 6 cells between them, just like a 12 volt battery. Fully charged voltage is about 12.6 in both cases. You can't change the chemistry. We have all heard the "if one fails you still have 12 volts in the other" but another poster has correctly stated that if one 12 volt battery in a parallel installation gets a shorted cell, the first thing that happens is the good battery discharges into the bad one, since the bad battery will now only have 5 cells and a back voltage of 10.6 volts which the good one overpowers at 12.6. In addition, the converter will dump all of its current into the battery with a shorted cell since it has less back voltage and a lower resistance. It will fully charge the remaining cells but still come up short at 10.6 volts.

Forget what they said. 6 volt golf cart batteries are more durable and designed for very deep discharges.

The fact is that a converter cannot tell if there are 2 6 volt batteries in series of one or two 12 volt batteries in parallel.
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Old 08-22-2016, 08:33 PM   #31
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Originally Posted by pmsherman View Post
IGolf cart batteries reserve capacity numbers are determined in a similar manner but with a 75A load. To compare the reserve capacity of a golf cart battery to a marine hybrid one, the golf cart reserve capacity time needs to multiplied by at least 3, and somewhere between 3.1 and 3.3 may be a better multiplier because there's more losses inside the battery as the current draw rate increases. Phil
Phil, while I agree with most of what you stated, this one rocked me a bit.

This is the first I have seen anything about multiplying 6 volt RC by 3.

In fact the conversion factor between RC and Amp Hours (AH) is well established at 0.4167 times RC.


"Reserve Capacity (RC) is the number of minutes a fully charged battery at 80 o F (26.7 o C) is discharged at 25 amps before the voltage falls below 10.5 volts. To convert Reserve Capacity (RC) to Ampere-Hours at the 25 amp rate, multiple RC by .4167. More ampere-hours (or RC) are better in every case."

Ampere-Hour (or Reserve Capacity) - Pacific Power Batteries - About ...
https://www.pacificpowerbatteries.co...../dcfaq4.html


What is your source to for that new information?

As to the 6 volt vs 12 volt debate, I think this quote from the Battery School at Northwest Batteries is most relevant:

"It would appear that there is no significant difference in capacity and voltage between these two examples. But this really is not the case. The plates designed for the T-105 use the same active material and alloy of the group 27 deep cycle batteries but both the T-105 negative and positive plates are 60% thicker than those found in the deep cycle 27 group sizes. The significance of this is that these 6 Volt batteries should have a longer lifespan than the two deep cycle 27 group sizes, if properly cared for. While the capacities are similar (220 versus 225 Amp Hrs.), battery longevity favors the two 6 Volt batteries. Why? Because a major cause of deep cycle battery failure is the shedding of active material from the battery plates."

http://www.batteriesnorthwest.com/ba...m?TID=20#ANC20
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Old 08-23-2016, 08:42 AM   #32
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I was at that forum and after I went to him and said I had 2 6v batteries he said something about som would work. Mine have worked in 2 trailers very well. My 2 12 volters gave me more problems if 1 was weak it would draw the other down.
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