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Truecabin
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# Posted: 14 Oct 2013 18:17 - Edited by: Truecabin
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solar question for people with more understanding than I have
can i use one 100w panel and 4 charge controllers to charge 4 different batteries? motorcycle, snowmobile and atv and a big 12v deep cycle that i use just for lights in my barn
i would get 3 cheap 2amp charge controllers ($11 on ebay) so each charge controller goes to its own battery. there is nothing using the batteries only there own self discharge from storage. normally 1/2amp is enough for these small powersports batteries.
the deep cycle battery has a bigger charge controller. since each battery has its own controller they are all isolated from each other and one bad battery cant drainthe others. and all the batteries get a charge if enough sun. the big deep cycle may be used a few minutes of 4watts lights once in awhile when I look in there at night.
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MtnDon
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# Posted: 14 Oct 2013 19:18 - Edited by: MtnDon
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No. Not with those three cheapy CC.
A typical 100 watt panel will have outputs in the range of...
Vmp = 18 volts +/- (max power volts)
Imp = 5.4 amps +/- (max power current)
That means that most likely each one of those charge controllers from ebay will be toasted when the amperage hits them. Maybe not all at once, but one at a time as they daisy chain. They are spec'd at 2 amps max input.
If the charge controllers all were able to handle the maximum volts and amps of the panel I'm not sure it is really workable. Never thought of ever wiring up this way. Maybe the CC's would sort out which battery gets full given sufficient time. I really dunno.
How long will the motorcycle, snowmobile and atv batteries be left unattended, unused? Those are the problem ones as I see it. A good CC can be left connected to panels and the main battery for months on end. The limiting factor is the battery electrolyte level. As long as the CC goes through a daily bulk, absorb and float charge cycle the battery should handle months of being left alone without any problems with the fluid level. Our 12 battery (6 volt golf carts) only needs fluid level maintenance twice a year.
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Truecabin
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# Posted: 14 Oct 2013 20:31 - Edited by: Truecabin
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good point, if all batteries were fully charged there could be 7amps
trying to think of a way that none of the 4 batteries can be drained by the system.
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MtnDon
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# Posted: 14 Oct 2013 21:27 - Edited by: MtnDon
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There are DC to DC chargers, but I suspect they are not cheap. Google Chargetek and Powerstream
It might be easier to use a separate low watt panel and controller for each of the motorcycle, snowmobile and atv battery. I have an old 10 watt panel and cheapy CC I use for our atv battery. If the panel has a low enough wattage it can be left connected w/o a CC as long as there are diodes to prevent dark time discharge. But I don't like those, but that may be just my nature. For a float / maintenance charge keep the output voltage down to no more than 13.2.
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Truecabin
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# Posted: 14 Oct 2013 22:35 - Edited by: Truecabin
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i looked at separate panels but all that will cost a lot more than one 100w
but will sharing one panel work?
was trying to make trickle chargers i think thats where i got off on the wrong foot theres no need foto trickle charge
why not just let the charge controller handle the whole thing if one of the batteries needs 7a let it have 7a
of course i might still be on the wrong foot
heres a 10a charge controller for $16 numbers look pretty good but 13.6 float
12 Volt or 12/24 Volt auto work, 10 Amps (for PV and load)
Equalisation voltage: 14.8Volt
High voltage disconnect(HVD): 14.4Volt
Float voltage: 13.6Volt
Low voltage disconnect(LVD) 11.1Volt
Low voltage reconnect(LVR): 12.6Volt
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MtnDon
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# Posted: 15 Oct 2013 00:28 - Edited by: MtnDon
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You will find a variation in what is recommended for a proper float voltage when researching. You can find numbers from 12.8 to 13.8 depending on source. I tend to the conservative side. AZ Wind-Sun states 12.8 to 13.2 volts in their FAQ section. I subscribe to their thinking and our batteries make it through winter and summer fine. 13.6 may be okay as long as that is the max.
One thing I have discovered is that the float voltage can vary a lot between individual items of the same model in the inexpensive category of chargers. It is just something that we noticed when setting up a variety of $10 float/trickle systems.
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Quoting: Truecabin why not just let the charge controller handle the whole thing if one of the batteries needs 7a let it have 7a
Not exactly sure what you mean... ... have 1 CC and hook it to all the batteries? That won't work as the 4 batteries will have different capacities, especially with the big main one.
Or maybe if the three small ones are close enough in capacity they could be grouped in a parallel string.
The main thing is I do not know for certain how two CC will react when accepting input from the same source panel and distributing the output differently. The issue that concerns me is that when a PV system CC realizes the battery it is charging is ready to switch to absorb or float charging it is designed to dump the excess current into a heat sink and it disappears as heat. That's why you see fins on many CC while some have internal cooling fins and thermostatically controlled fans. On a quiet afternoon I can hear the fan on our Outback CC cycle on - off.
If there are two CC connected to the same PV panel, and one reaches the float point what is going to prevent that CC from bleeding off the excess to its heat sink instead of letting the other CC use that excess? I think that is the crux of the problem.
Will those three small batteries be sitting unattended for more than a month or so at a time? I've never worried about mine for durations of a month or less. But for longer I can appreciate the concern.
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Truecabin
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# Posted: 15 Oct 2013 11:37 - Edited by: Truecabin
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Quoting: MtnDon If there are two CC connected to the same PV panel, and one reaches the float point what is going to prevent that CC from bleeding off the excess to its heat sink instead of letting the other CC use that excess? I think that is the crux of the problem.
4 charge controllers is what i need but example of 2 is a good way to discuss it
a charge controller for each battery and the batteries are different and the CCs operate discrete
don yes that it the crux thanks
i suppose somebody out there knows this and i hope they can post info
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MtnDon
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# Posted: 15 Oct 2013 15:36
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two batteries are possible from this dual CC
http://www.solar-electric.com/modubachco25.html
Batteries need a common negative though.
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Truecabin
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# Posted: 15 Oct 2013 20:22
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i can see a use for that on an rv with one panel on the roof
Quoting: MtnDon Batteries need a common negative though.
but on different vehicles grounding them together is one more thing to forget
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Rossman
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# Posted: 16 Oct 2013 14:56
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Ya, I was going to mention the sunsaver duo. I heard this works quite well! But it would only do two batteries for you...and its priced quite high compared to what you'd been mentioning/looking at.
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Truecabin
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# Posted: 18 Oct 2013 22:26 - Edited by: Truecabin
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To just spend money i would buy a panel for each battery but i want to save money and do something smart but thats asking a lot 
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MtnDon
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# Posted: 3 Jan 2014 20:04
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Did you resolve the problem of how to charge many batteries simply?
Here's what I did recently for a simpler problem of keeping one ATV batteries charged, along with the main battery bank. I used to have a small panel that did the ATV battery, but lost it to a falling tree.
We have an Outback charge controller. They have an AUXillary function. One of the options is called float. When the main battery bank has gone through the bulk and absorb stages it goes into float charge. With the float function engaged a device can be switched on. I chose to have the float function activate a relay switch.
The relay switch is connected to the on-off remote on the Outback inverter. So when the CC goes into float the inverter is switched on. We make sure that when we leave all lights, fans, pumps, etc are all turned off.
This time of year when the cabin is left unoccupied the charge system goes through a brief daily bulk charge, a one hour absorb charge and then into float. On an average day float lasts for 3 hours, maybe 3.5 hours.
In the barn I leave a 2 amp battery charger connected to the ATV battery. It is plugged into a timer that is plugged into 120 VAC power. When the CC is asleep, in bulk or in absorb the timer and battery charger are off. When the CC is in float the timer is running. When the timer clicks into "on" mode the battery charger begins to charge the battery. It is set to allow battery charging for 2 hours every 12 hours of float time.
I hooked it up November first. So far it has worked well. We went up just after C-mas. The ATV cranked over and started on one tap of the start button. Left disconnected overnight the voltage in the AM was 12.65; full.
It works for me and beats dragging the battery home.
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