12V or 6V Batteries - Which charge Better?
I plan to switch to two 6V batteries in series, but before I do, I need to ask this question. When the batteries are drained and in need of charging, which will charge back up to full FASTER? Two ...
Forum Discussion
Ron,
Your question is good, and if you have read the thread through, you may feel more confused than answered. I did a lot of boat work before the depression and I got asked variants of this question by almost every owner to whom I wrote a quote. Let me try to give you a complete answer.
Lets start with the first fact: Lead acid (l/a)batteries do not play well in parallel. To answer why in detail will take another half of an hour. Trust me on this one. Avoid paralleling batteries.
Another issue of semantics that we have to clear. Recharging any l/a bank to true full density without damaging either the bank or the connected hardware will take hours. From a 50% discharge, the majority of the bulk charge can be done in about four hours with the right system, but that will end at the 85~90% area and the last 10~15% will take at least another four and maybe more hours.
You have to realize the that entire existence of an L/A battery is between 12.0 (~50%) and 12.6 (~100%) when it is in use. Its charging home is between 13.5 and 14.4. Less takes forever and more starts to hurt things.
The only thing that can improve the charging rate is to go to a variety of l/a battery called an AGM. Price these and you may just stop there. They are good, but you pay for it up front.
If you had a pair of 12V in parallel and a pair of 6V in series of roughly the same Ampere-Hour capacity, and both banks were drained the same amount, Recharging them to the original density would take the same time with the same hardware. That is all there is to that. Except, as they age the two 12V will get cantankerous and you may have a hard time getting both to density at the same time. See the second paragraph.
So, If you want to have a house bank that lasts well and you can recover it relatively quickly with your APU (genset), a very simple recommendation will be: a pair of GC2 batteries in series,
A good three or four stage "smart" converter charger (Progressive Dynamics or Iota or ??), The converter mounted as close to the bank as practical and connected with short Heavy Cable.
Why???
GC2s are golf cart batteries and they are real deep cycle. Most 12v that are sold as Marine Deep Cycle are not. They will not stand the abuse that a GC2 will take in stride.
A good smart converter/charger will sense that the bank is low and go into bulk mode as soon as it has power. It will, however, not exceed the mid-14s as higher than that has a tendency to toast the DC powered stuff and heat the batteries (not good).
The short heavy cables are essential. The charger only knows what it can't exceed and if you burn off even a tenth of a volt on the way to the bank, your required charge time will be extended.
That is most of what you or anybody else needs to know and think about. If you want to know what is really happening, get and install a real battery monitor system. (~250$us for hardware) These have names like Trimetric, Victronic and Xantrex and will report the real bank status based on the ampere-hours taken out and replaced. If you put one in, be ready to learn a lot fast.
Matt
Your question is good, and if you have read the thread through, you may feel more confused than answered. I did a lot of boat work before the depression and I got asked variants of this question by almost every owner to whom I wrote a quote. Let me try to give you a complete answer.
Lets start with the first fact: Lead acid (l/a)batteries do not play well in parallel. To answer why in detail will take another half of an hour. Trust me on this one. Avoid paralleling batteries.
Another issue of semantics that we have to clear. Recharging any l/a bank to true full density without damaging either the bank or the connected hardware will take hours. From a 50% discharge, the majority of the bulk charge can be done in about four hours with the right system, but that will end at the 85~90% area and the last 10~15% will take at least another four and maybe more hours.
You have to realize the that entire existence of an L/A battery is between 12.0 (~50%) and 12.6 (~100%) when it is in use. Its charging home is between 13.5 and 14.4. Less takes forever and more starts to hurt things.
The only thing that can improve the charging rate is to go to a variety of l/a battery called an AGM. Price these and you may just stop there. They are good, but you pay for it up front.
If you had a pair of 12V in parallel and a pair of 6V in series of roughly the same Ampere-Hour capacity, and both banks were drained the same amount, Recharging them to the original density would take the same time with the same hardware. That is all there is to that. Except, as they age the two 12V will get cantankerous and you may have a hard time getting both to density at the same time. See the second paragraph.
So, If you want to have a house bank that lasts well and you can recover it relatively quickly with your APU (genset), a very simple recommendation will be: a pair of GC2 batteries in series,
A good three or four stage "smart" converter charger (Progressive Dynamics or Iota or ??), The converter mounted as close to the bank as practical and connected with short Heavy Cable.
Why???
GC2s are golf cart batteries and they are real deep cycle. Most 12v that are sold as Marine Deep Cycle are not. They will not stand the abuse that a GC2 will take in stride.
A good smart converter/charger will sense that the bank is low and go into bulk mode as soon as it has power. It will, however, not exceed the mid-14s as higher than that has a tendency to toast the DC powered stuff and heat the batteries (not good).
The short heavy cables are essential. The charger only knows what it can't exceed and if you burn off even a tenth of a volt on the way to the bank, your required charge time will be extended.
That is most of what you or anybody else needs to know and think about. If you want to know what is really happening, get and install a real battery monitor system. (~250$us for hardware) These have names like Trimetric, Victronic and Xantrex and will report the real bank status based on the ampere-hours taken out and replaced. If you put one in, be ready to learn a lot fast.
Matt
