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Small Cabin Forum / Off-Grid Living / Recharging Solar Battery Bank with generator question?
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hallamore
Member
# Posted: 14 Nov 2010 09:06
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Don, one more question about your Iota. Is the plug that is attached to the charger an AC 3 prong plug?

hallamore
Member
# Posted: 14 Nov 2010 09:07
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Don,

One more question, Does the Iota charger have a AC plug that is attached to the unit that I can simply plug into the AC recepticle in the Honda generator?

MtnDon
Member
# Posted: 14 Nov 2010 13:15
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Yes, my Iota comes with a short (3 ft?) AC cord attached with 3 prong plug. The DC cables connect via a srew terminal; strip off a little insulation, insert the stripped end and tighten a set screw.


We've never been to Iowa, but one never knows. Next summer is going to be absorbed with a western states trip. Maybe in a future year. Thanks very much for the invitation.

hallamore
Member
# Posted: 1 Dec 2010 22:28
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Don,

Another question for you if you don't mind. I just purchased three Sharp 123 watt 12 v panels (7.16 A each). Since I have a total of 8 six volt batteries for a bank total of 900 ah and give the fact that my C35 charge controller is capable of doing equalization. Can I simply charge/equalize two of the batteries (in series to make 12v) at a time? If I need to get to a 5% or greater output from the array this might work...basically 3 new panels putting out approx 20 amps / 225 ah bank = 8.8%. I would then move on to the next two and so on until all are finished. Funds are low right now and I can't justify purchasing a charger that can equalize since I just purchased the panels. What do you think?

MtnDon
Member
# Posted: 1 Dec 2010 22:48
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A purist would likely say it is best to do them all at once, and that may be true. However, I don't see any harm in splitting them into pairs to accomplish the equalization. At least it has the advantage of getting the task done, even if over a slightly longer period of time.

I basically do a similar thing when I want the RV batteries equalized. I back the RV up close to the cabin, disconnect the cabin batteries from the charge controller and use jumper cables to connect the RV to the CC. That equalizes a string of 4 instead of the twelve in the cabin.

Anonymous
# Posted: 30 Oct 2011 14:42
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I just purchased a xantrex freedom sw3000 to be used in a backup residential set up. I also purchased 3 trojan AGM-31 100Ah each.
My goal is to reach a minimum of 800 Ah soon and grow to 1800AH of batteries capacities in the future.
Are there 6v AGM trojan that I can purchase to mix with the 12V AGM-31. Also can all the batteries on that setup be charged at the same time using my sw3000?

MtnDon
Member
# Posted: 30 Oct 2011 20:42
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Not a good idea to mix different types/sizes/capacities of batteries. Also not a good idea to add batteries over a period of time. One year between oldest and newest is pushing it.

kd5edp
# Posted: 31 Oct 2011 13:03
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I have everything setup on 12v except the televison. I have an RV power distrubution panel which has a built in charger. So when I do need the generator not only does it supply power for my needs it charges the battery. No change over nothing to do but monitor voltage. Also to reduce cost and storage porblem I have converted my generator to propane. Sure works well.

MtnDon
Member
# Posted: 31 Oct 2011 14:19
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Some RV power panels are better than others. Does yours have a 'staged' charge system; bulk, absorb and float? Some don't and offer a compromise which is not a high enough charge rate to get the charge done as quickly as possible and yet too high a charge rate to be called a float. It's one reason many folks with RV ruin their batteries in a couple of years. That and not paying attention to fluid levels. Just mentioning it because I know some people who have used RV equipment and had some issues. Newer and better RV's have better chargers.

The auto switching is a very nice thing to have.

Anonymous
# Posted: 31 Oct 2011 16:13
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Don,
Can the freedom sw3000 used to charge 6v batts, also I am planning on going solar soon, would I be able to use the inverter
portion of the sw3000. If yes is there any special setup.

MtnDon
Member
# Posted: 31 Oct 2011 17:47
Reply 


That is a 12 VDC based unit, so two 6 volt batteries in series can be used (or multiples of two when in a series-parallel configuration.

Is it ideal for an off grid system? A small one, IMO. You'd have to check the manual to see the max charge rate to see how large a battery bank could be charged with whatever time you'd have great sun every day.

Jb
# Posted: 6 Nov 2011 09:07
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Don,
I have a portable Honda generator Eu2000i. This unit produces 1600 pick/2000 watt surge it has 16.7 amp current. Would I be able to use that generator to charge a battery bank of 4 6V Trojan @ 200Ah each (800 ah total) using a Xantrex sw3000 Inverter/Charger. I think the sw3000 has a 150 amp current (plse confirm).I s this possible? Also is there a math formula to determine how many hours it will take to fully charge these batteries? Assuming the generator will solely be dedicated (at that time) for the charging function.
Tkx

Rob_O
# Posted: 6 Nov 2011 10:01
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Jb:

Unless you are running a 6V system, you do not have an 800AH battery bank, you have either 400AH at 12V or 200AH at 24V. Add voltage in series strings or amperage in parallel strings of batteries

Bulk charging rate should be around 10% of the bank capacity, the charger will allow you to dial back the max current to match your battery bank. That will require around 5 amps from the generator so you will still have plenty of overhead available when the genny is running

As a rough guess, I'd say you will need an hour for every 10% of discharge below 90% SOC and 2 hours for that last 10% - As the battery gets closer to a full charge you have to drop the current and increase the voltage

razmichael
Member
# Posted: 6 Nov 2011 10:44
Reply 


Rob_O - I think your estimate is pretty close. I have a HF1800 Xantrex inverter/charger which can put out 40 amps for charging but I only have 2 6v Trojans so I dial it back to 20 amps for the first phase of charging. When I need to charge (my use has exceeded my solar panel capability for whatever reason) I have a Honda 2000 that I plug the HF1800 into (auto switch-over). Your figures for charge time would seem to match my experience (given the smaller battery bank). The last 10% takes most of the time.

Jb
# Posted: 6 Nov 2011 14:56
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Rob_O

Thanks for your quick response to my post, but I am a bit puzzle by your evaluation of my battery bank capacities. I was under the impression when connected 2 6v batteries in Series, double the system's voltage (6v + 6v = 12v), connecting in paralel keeps the voltage but double the capacities (in my case I would have a system of 6v with a capacity of 400ah). My taught was connecting those 4 batteries in Series/Paralel would of increase my voltage to 12 and Ah to 800, I guess I have been wrong all along. To reach that 800ah plateau, I will need to purchase 4 more of those same Trojan 6v agm.
Going that route, is there a limit of the number of batteries one can string in 1 bank?

You mentioned at one point during the charging process, I will have to drop the current and increase the voltage. Are those functions not done automatically by the Xantrex Iverter/Charger sw3000, or do I have to manually get involve? Also do you know how much Amp does that unit put out to charge the batteries. I think have read something about 150 amps, if that so would 'nt such power be harmfull to my batteries?

Thanks,

Jb

Rob_O
# Posted: 6 Nov 2011 15:26
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Quoting: Jb
To reach that 800ah plateau, I will need to purchase 4 more of those same Trojan 6v agm.


Yes

Quoting: Jb

Going that route, is there a limit of the number of batteries one can string in 1 bank?


You can keep adding batteries as long as your charging system can keep up. Above 1200AH your generator will be the limit and you will charge at a slower rate

Quoting: Jb
You mentioned at one point during the charging process, I will have to drop the current and increase the voltage. Are those functions not done automatically by the Xantrex Iverter/Charger sw3000, or do I have to manually get involve? Also do you know how much Amp does that unit put out to charge the batteries. I think have read something about 150 amps, if that so would 'nt such power be harmfull to my batteries?



The charger will handle the charging process automatically. You will need to manually adjust the output of your charger in the setup menu.

J W
# Posted: 9 Mar 2012 13:29
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I ran into that same problem some months back. My solution then was to get a 4 pole double double throw 150 amp dc switch and wire everything to it in the right configuration.

on each side you have 4 poles to connect to on side A and 4 center connectors and 4 poles to connect to on side B.

Generator AC "hot" hooks up to pole 1A and to the charger. Center 1 hooks up to the AC electric panel hot incoming to furnish power directly when the generator is on.

Pole 1B hooks up to the inverter hot to provide power when the battery is used to the electric panel.

Pole 2A connects to the charger DC+. Center pole 2 hooks up to battery positive. Pole 2B goes to inverter DC+ in.

Pole 3A connects to generator neutral. 3center connects to panel neutral. Pole 3B connects to inverter neutral. This prevents backfeed through the negative terminal isloating the generator from the inverter. The inverter will be damaged if not.

The generator I use is the Harbor freight 900 watt model, the charger is a2/10/50 amp automatic car charger. I leave it on 50 amps usually to charge batteries up to 14v This little generator serves my needs well, runs over 5 hours on a gallon of gas and can handle 6 120ah deep cycle batteries easily bringing them to full charge in only 5 hours and still provide enough AC inside to run my computer, several tool battery chargers of different sizes and some lights.

I am changing this configuration slightly now to allow the automatic use of a solar PV system with this. The fourth set of poles on the switch will be used to include the PV system charge. Two sets of wires will go to the battery, one being incoming from the generator powered charger and the PV charger. Each battery has a schottky diode to allow power to the battery but no reverse currant. The solar charger has a diode to prevent power from the generater charger from going to it. Capacitors to connecting the DC+ to DC- filter out stray AC from the generator from reaching the solar charge controller. The solar charge controller is set at 15 volt. After passing through two schottky diodes it becomes 14v.

The positive from the batteries providing power to the inverter and to DC powered lines pass through a schottky diode mounted on each battery to isolate all batteries. This reduces the voltage by 1/2 volts. The power then goes through a buck booster to bring the power back up to 13VDC.

If I could afford the Xantrex inverter/charger described above I would not need the switch and my complicated wiring.

stoverr2
Member
# Posted: 20 Mar 2012 08:43
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A buddy of mine was mentioning something that he has for his sailboat that acts as a multi-input charge controller. As the boat is in drydock he's not able to look at the name and information for it. Basically it allows for input from his solar panels, his 4hp outboard with an alternator attachment, and wind power if he ever gets around to installing it.

I was thinking of adding something similar to this myself. No chance for wind power, and of course I'll not be using an outboard, but I was thinking of tying in a generator.

Have any of you heard of such a beast? I'm still reading through this thread to see if I stumble across it. If not this avenue, how about a simple marine trickle charger? I've used them for years on my boats and love them. Granted, the ones I've used had multiple connections for batteries that are not tied together, but I know I can pick up a single output one for a fair price.

MtnDon
Member
# Posted: 20 Mar 2012 10:15
Reply 


A good trickle charger is good for what they are meant to do; place a small charge into the battery to make up for the self discharge characteristic of lead acid cells. In the alternative energy industry trickle is generally referred to as a float charge. A float / trickle charge is pretty much useless for recharging a battery that is not near the full charge point though.

I have no idea what that marine unit is like. There are major differences between what a charge controller for a PV system has to do compared to the controller in most wind generators. There are charge controllers that are sold that can be used in either function, but not one unit doing the two tasks at the same time.

Engine driven alternators, like auto and marine alternators, usually have internal regulation and do not require an external controller.

marvin42
# Posted: 10 Jul 2012 09:26
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I have a solar system that can't quite keep up with my power needs, so I now have a generator and an "intelligent battery charger" to recharge the batteries when they get low. Can I charge them with solar and generator simultaneously? The solar system has a regulator, and the battery charger throttles back as it nears full, so I'd guess yes, but I don't want to risk killing the batteries

Anonymous
# Posted: 24 Jul 2012 17:03
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MtnDon
Hi Don,
I have a 8 panel system (110W each) into a charge controller, to 5 AGM batteries wired in series then up to my inverter. The cabin is wired for AC so everything is inverted. I introduced a refrigerator and I now struggle at times for storage. I am limited to space so adding more batt's would solve my problem however I was thinking about charging them up periodically. Is it best to D/C the batt's from the charge controller and charge them offline? Thx

MtnDon
Member
# Posted: 24 Jul 2012 21:24
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Refrigerators are energy hogs; but we do need them.

Is the plan to use a generator and a battery charger to charge the batteries? No real need to disconnect the CC.

The best plan, IMO, would be to use the generator and charger to bring the batteries to 75 to 80% full charge in the evening or early morning hours. Chargers run by a generator will make best use of the fuel during the early stages of recharging. If your charger is a good quality 3 stage charger that would be best as that type begins with a high ampere bulk charge. Someplace around 75 to 80% they switch to a low ampere but higher voltage charge. This is the absorb or acceptance stage.

Absorb lasts several hours as a rule and is quite inefficient use of the gasoline. The solar panels, however, excel at delivering a low amp higher voltage absorb charge. They should then have plenty of time to bring the charge to 100%. Of course I am assuming you have a 3 or 4 stage charge controller.

Canavan
# Posted: 3 Mar 2013 16:43
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I want to have a battery bank with two (or four) RV deep cycle batteries for my cabin

I do not want an inverter

Can I connect solar panels / charge controller and a 110v Xantic style 110 volt charger to the battery bank at the same time

When the generator is running I can use 110v items, 12 volt items, and charge the battery bank.....when the generator is not running I will have the solar panels adding charge and using 12v lights and items

if this will work where can I get a wiring diagram with disconnects and fusing layout?

Moving Pictures
Member
# Posted: 4 Mar 2013 07:06
Reply 


Your panels are insufficient to charge your batteries; and further, your inverter is probably too large for them as well.

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