Battery charging info
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Jun-08-2015 07:57 AM
We've installed a variety of systems and lived with equipment from many manufacturers, and this is all the info -- in plain language -- that I wish I'd had access to when we were designing and installing our systems and scratching our heads trying to understand how everything really worked once it was installed.
I'm not pretending to be an expert, but we've spent over 2,500 nights living off of battery power and have learned a lot in the process. In the hopes that I might help out other RVers, I thought I'd post the links here.
RV (& Marine) Battery Charging Basics
- Single vs. multi-stage charging, in depth
Converters, Inverter/Chargers, Engine Alternators
- How "artificially powered" charging systems work
Solar Charge Controllers
- How to optimize battery charging from a "naturally powered" charging system
I hope this info proves helpful to others...
2007 Dodge RAM 3500 Long Bed / Single Rear Wheel
Traveling full-time in an RV and sailboat since 2007
Our full-time blog: http://roadslesstraveled.us
-Stories, photos, and lots of RVing tips!!
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Aug-22-2015 05:39 AM
I have posted some info about what happens when solar charging is combined with battery charging via electric hookups or a generator or an engine alternator... I hope it is helpful:
RV Battery Charging - Solar Power and Shore/Alternator Power Combined
2007 Dodge RAM 3500 Long Bed / Single Rear Wheel
Traveling full-time in an RV and sailboat since 2007
Our full-time blog: http://roadslesstraveled.us
-Stories, photos, and lots of RVing tips!!
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Jun-12-2015 07:50 AM
400 AH would be fully charged as current approaches 2 amps. But you cannot set it for 5% (45 x 5% = 2.25) because usage may keep you in absorb all day.
I would try something like 50% duty cycle and 15 minute timer. This should give a short time in storage and extended time when in use. Adjust the duty cycle if absorption seems too short or long while in use.
I think there is a help function in MSView to make suggestions. Not sure if the duty cycle % applies to your solar amps or the controller rated amps.
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Jun-11-2015 10:38 AM
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Jun-11-2015 10:11 AM
Storage; a short absorption is fine.
Normal; usually needs a couple hours. (mine is programmed to extend at 12.5)
Severe; holds absorption voltage all day. (mine is programmed to cancel float at 11.9)
Bogart or Victron that ties into a battery monitor will have a better shot at dropping to float right at 100% charged.
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Jun-11-2015 09:42 AM
So, these controllers that adjust Abs Time must be looking at beginning Vbatt (which is not that reliable, seeing as the controller has no idea if the bank is under load, or how big a load), and considering how long it took to get voltage up to the Vabs set-point. Obviously, a 20% rate would do that quicker than a 10% rate. So, a 50-80%, (+129Ah's), at a 20% rate (86a), would take about 1 hour 30 min., while a 50-90%, (+172Ah's), at a 10% rate, (43a), about 4 hours. And that extra 2 1/2 hours in 'bulk' would correspond to another 20 minutes in Abs.
So, yes, I see now, how that could be done, but with limited accuracy.
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Jun-11-2015 06:42 AM
Compare the constant vs tapering times in the three sets.
on Ford E350-460-7.5 Gas EFI
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2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.
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Jun-11-2015 06:10 AM
In that case, they would need to spend more time in bulk/cc... Abs/cv would not differ. Charge Rate and Vabs setpoint decide how long Abs will take, not dod beyond the transition from bulk to Abs.
Real World vs. Marketing
Like I've said, a 50-100% charge at a 10.5% C-rate will cause amps to taper (i.e; go into abs) at 89.5% soc, and a 70-100% charge will likewise cause amps to taper (i.e; go into abs) at 89.5% soc. The numbers don't lie. The depth of discharge beyond the point of tapering is irrelevant, regardless of what any marketing strategy would suggest.
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Jun-10-2015 02:53 AM
Morningstar handles this by looking at what the lowest voltage was that the batteries reached overnight. If they got below a certain level, they stay in Absorb longer, and if they got to a really low level they don't go into Float at all...
The only limitation to that approach is that if they got really discharged overnight but some other charging system got going before the sun came up, they might be fully charged at sunrise and not need to spend much time in Absorb.
This would happen if you had a big alternator on your MH or boat engine and you started driving/motoring at midnight and went all night... by sunrise you wouldn't need much solar charging if any.
2007 Dodge RAM 3500 Long Bed / Single Rear Wheel
Traveling full-time in an RV and sailboat since 2007
Our full-time blog: http://roadslesstraveled.us
-Stories, photos, and lots of RVing tips!!
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Jun-09-2015 01:51 PM
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.
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Jun-09-2015 01:34 PM
In this particular case, I would be forced to do 50% dod's, just to get the bank fully charged using that 2X time factor... thus decreasing battery life, either by chronic undercharging, or deep discharging.
No predetermined 'factory formula' will do.
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Jun-09-2015 12:00 PM
Absorption can go on forever, so some kind of cut-off is needed so it will start Float. Many chargers use about 97% SOC as their cut-off point to drop to Float (such as the PD converters) and the typical "automatic" charger will shut itself off there too.
That is where all this " 2% acceptance rate means full" comes from that I hate so much, when to me, "full" means 100% not 97%. 😞
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.
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Jun-09-2015 11:41 AM
I fail to see how time in bulk is relevant to time in absorb? At a given voltage, and a given current limit, amps will begin to taper when the bank is at a particular soc. This will not change, whether the the bank was at 50% soc or 70% soc to begin with..
The point at which bulk/cc switches to abs/cv is determined largely by charge rate and Vabs setpoint. How long it takes to get to this point in no way affects how long it will take to get from this point to full.
I have my parameters set such that amps will taper when % C-Rate = % dod, and Amps to bank = Ah's depleted. So, a 45a charge on my 430Ah bank (a 10.5% C-Rate) will result in amps tapering at 10.5% dod (-45Ah's). But the time spent in bulk/cc, before this occurs, does not effect this. A 50-89.5% bulk charge will take about 3.8 hours, while a 70-89.5% bulk charge will take about 1.9 hours. But either way, amps will begin to taper at 89.5% soc/10.5% dod, and will take the same time from there to 100% full, regardless.
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Jun-09-2015 09:51 AM
2007 Dodge RAM 3500 Long Bed / Single Rear Wheel
Traveling full-time in an RV and sailboat since 2007
Our full-time blog: http://roadslesstraveled.us
-Stories, photos, and lots of RVing tips!!
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Jun-09-2015 09:46 AM
pnichols - We actually upgraded to AGM batteries on our trailer in April and had them for all our years on our boat as well, so I discuss them at length in the first post in the series on battery charging (you probably didn't check out that post since you've been around that block already... no problem!). I really appreciate all your detailed notes on AGMs and will add the tidbits I missed! Thanks for reading my other goodies in the past too!!
2007 Dodge RAM 3500 Long Bed / Single Rear Wheel
Traveling full-time in an RV and sailboat since 2007
Our full-time blog: http://roadslesstraveled.us
-Stories, photos, and lots of RVing tips!!