BFL13 wrote: The acceptance rate would double but so would the required AH to restore. Where is the time saving coming from?
Time x to do a 50-90 on a 110 at 20amps twice = 2x
Time y to do a 50-90 on a 220 at 40amps once = y
How is y less than 2x?
Not sure what you point is here....In fact I think you are missing the point of the thread, or arguing for the sake of it.
But if you are charging off a converter, you will get far more output from the converter if 2 batteries are connected, as much as double at certain points along the SOC/acceptance curve. Not to mention the higer likelyhood of the converter going into "boost" mode. If you are charging from 1 undersized charger, the batteries will take more amps later in the charge cycle, but never less.
If you have 2 battery chargers, then yes, you could charge them seperately, but why would you? Why have 2 chargers, when one larger one will work with less effort?
Or how about the fact that this thread was about getting more battery life, and not about charging?
* This post was
edited 04/15/12 12:33pm by Hybridhunter *
I think what the OP was looking for was an answer about connecting the 2 batteries, not about charging.
I recently added a second battery, and everything runs with less voltage drop. Less dimming of the lights when the pump runs, almost complete elimination of low voltage warnings and shutdowns with my 1500w inverter.
Everything runs better, and if you are not too concerned with how long the life of the batteries are, I can tell you, usuable range for the batteries extends to the point of them being almost stone dead, where as with one battery, the pump gets wimpy, the lights get very dim, etc.
Overall, I think joining the batteries was an excellent upgrade for us, and we get up to far more than double the usable power, I would say we get around 2.5 times more run time between necessary charges.
Not to mention that our WFCO goes into boost, and uses the full capacity of our generator, and stores a lot of power, very quickly, cutting necessary charging times dramatically.
That reality, not theory. Good Luck!
* This post was
edited 04/15/12 12:39pm by Hybridhunter *
Ok, so the scenario is hit the 110 with a 45amp smart charger and do a 50-90, then do it again and get the total time. Then bank the two and use the same 45amper on them and time that.
I have figures for 70 on 220- 32% rate-( that 130 min) so two of those in a row would be 260 min.
So 70 on 440 would be a 16% rate. The story is that it would be faster than 260 min ??.
This would be if the total time with tapering amps is longer doing them one at a time. Maybe. So it could be shorter with a 50-90 but not if you were doing a 40-80. That is why I asked that the SOCs for start and finish be given along with the charging rates.
Hybridhunter wrote: I think what the OP was looking for was an answer about connecting the 2 batteries, not about charging.
The OP was asking which is "better", having two separate batteries or hooking both together? If you're going to talk pros and cons of each, how do you NOT talk about charging?
I believe the Peukert effect is a logarithmic scale and will not be a huge increase once you are discharging over 48+ hours. Here is a graph from USBattery that shows some data points from 1 to 20 hour discharge rates.
If you graph out the data you possibly can estimate the additional power available by adding the second battery and doubling the discharge time or reducing the discharge rate by half.
Hybridhunter wrote: I think what the OP was looking for was an answer about connecting the 2 batteries, not about charging.
The OP was asking which is "better", having two separate batteries or hooking both together? If you're going to talk pros and cons of each, how do you NOT talk about charging?
And you snipped a 400 word post to reply with that? Seriously? Did you read my prior post? Ugh.
Anyhow, I should have added that I get around 3 - 4 full days from my grp 27 & 31 batteries. And for the gentleman above that posted the discharge cycle info; remember that RV loads are sporatic, and depending on the user, fairly high peak withdrawal levels are what should be factored in. To be clear, just because the OP may not discharge the battery completely for 3 days, does not mean that the losses associated with higher current loads do not apply, just because the batteries sit unused for periods in between.
It may well be sporatic and at the same time the discharge for each battery is still cut in half when the pair runs in parallel. The higher the discharge rate the more benefit from having the batteries in parallel. You can very well discharge sporatically at the 20 hour rate over a 72 hour period and your benefit will be compared to the 10 hour rate if the batteries are used individually.
Now visit the link and you can find 89 vs 105 amp hours for a 27 at the 10hr vs 20hr rates. That is an 18% improvement for running in parallel.
Actual use is never constant or consistant so of course your results it will vary.
Folks, I am really confused by the foregoing debate. I am surprised that there is not a "best practices" consensus -- parallel is best, or single makes more sense, or whatever.
I am a low power user -- rarely more than an amp or two at any one time, except when the water pump is on (a few minutes a day) or the furnace (also maybe 10 minutes a day). So my guess is that the draw is so low that the Peukert effect will be subtle.
Someone said that the way I am using my batteries will shorten their lives. Not sure why -- I never let them drop below 12.1 volts, which (I think) is 50% charged, which (I think) is the recommended minimum. Am I wrong?
These are fairly new batteries (over a year old) and were purchased at the same time. They are well-maintained -- water is topped up, and they are on a batteryminder plus.
Again, thanks for your insight.
But
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