Aquar Battery Bank issue

[Jon Dubee]

I have an remote cabin that is 300 feet uphill from my proposed Aquair site. I need to design an battery bank within 100 ft of the cabin (or 200 ft from the Aquair .) This would allow me monitor batteries and inverter throughout the winter. I am looking for suggestions other than using 2awg wire. This is in upstate NY where snowfall an ice will make going down the bank dangerous. Ultimately I hope to build enough of an high-brid system for a home to be powered there. Deeded rights for hydro go back to 1908. All ideas are greatly appreciated. Thank you in advance for your time and thought. Jon

[Rob Beckers]

Hi Jon,

Welcome to Green Power Talk!
What size is the hydro turbine (Wattage)? Voltage? What loads is the battery bank supplying? I assume there's no real need for multi-day backup energy storage, since hydro power is fairly consistent.

Give us a bit more info.

-RoB-

[Jon Dubee]

Rob - Thank you for the prompt reply. I have yet to determine actual loads although I anticipate to operate the 12V Aquair @ 65 % output ( 1.2Kw/week) but this may change due to the formation of ice in Jan.- Mar.. I do not have the battery bank yet either . Ideally I would like to run a fridge, laptop , well pump, several 25 watt lights. The Aquair came with only 18ft of wire connected to a resister plate. I have tried to contact them via email for suggestions but have yet to receive a reply. The sight could support a array of these units if this one proves functional as I suspect. I had an Certified NY State alternative energy installer look at the site , but due to the fact that it was not grid tied and ineligible for NYS grant monies, and also that he had little hydro experience he declined to accept the job. He had mentioned the use of transformers on each side of the run , but I have not been able to find information on the installation of these. I will be doing all work myself and if need be will invest in the 2awg wire needed for this run. The terrain is rocky and steep (40 degree). As you folks are the pros any and all suggestions are appreciated whether they may imply a cost savings or not. Thanks Rob. Jon

[Rob Beckers]

Hi Jon,

If my information is correct, the Aquair delivers DC voltage, not AC. That means a transformer is not an option. These things are 100 Watt at full power, right? So, if you run one at half power, 50 Watt, it would produce 0.05 * 24 = 1.2 kWh per day (your number is "per week" but that can't be right).

I modified a little wire loss spreadsheet I have to use 12 Volt and 50 Watt (and therefore a current of 4.17 Amp), and here are the results in wire losses for 300 feet of wiring (assuming I didn't make a mistake):

8 AWG - 13.1%
6 AWG - 8.2%
5 AWG - 6.5%
4 AWG - 5.2%
3 AWG - 4.1%
2 AWG - 3.3%
1 AWG - 2.6%
0 AWG - 2.0%

So, depending on how much loss you are willing to accept, it looks like 4 or 3 gauge (around 5% losses) would be a good choice. If the batteries are kept fairly well charged their voltage will be somewhat higher, and therefore the current (and losses) somewhat lower than indicated here. This is worst case.

Do you already have the Aquair? It looks like they also make this in 24 Volt. That would be a better choice for using thinner wire, and to run all those loads that you are planning on.

Talking about loads: A regular (fairly efficient) fridge will use up 1.1 kWh per day all by itself (that's taken from a new 22 cu. ft. fridge). The well-pump, lights, laptop will depend on how many hours a day you estimate you'll run those. The upshot is that you are going to be running low on power by quite a bit if that 1.2 kWh per day is all that's coming in. For the fridge, you can cut down on use by going with the special off-grid DC fridges, such as a Sundanzer. One of those would use around 0.2 kWh/day for a 8 cu. ft. fridge.

You also mention that during the winter months the water flow comes to a halt. If that is so and you have no other source of renewable energy, you'll need a generator to keep those batteries charged (if you plan on drawing those same loads).

If you have the water resource, why not use a somewhat larger hydro generator? Something like an LH1000 from Energy Systems & Design (http://www.microhydropower.com/). Hydro is not my specialty, so for what it's worth; The place to start is to take a look at the available 'head' (the drop you can create in water), and the flow. Some turbines are intended for low-head, others for high-head situations. The Aquair is a very low-head turbine, all it needs is sufficient flow. The LH1000 requires about 1 to 3 meters (3 - 10 feet) of head, and a certain amount of flow.

Hope this helps!

-RoB-

[Jon Dubee]

Rob - all great info. Yes the aquair is 12V, and I have it. 10 ft. of head is obtained over 168 ft of river. I looked at Pelton turbines first. The river is producing 6 - 10 MPH right now (max. operating velocity) . It does not freeze solid in the winter and I have manually moved many stones to create a "winter pool" but I expect it to slow down and not freeze. I have an 6500 watt Onan generator at the cabin as well as some solar panels (40 watts). The cabin is used for 2 or 3 days max. in the winter access by snowmobile only. So the batteries should remain charged. Based on your calculations, if 300 ft of 5 awg is used even with the loss this should be ample watts for my initial stage. What would you recommend for battery bank , size and brand , keeping in mind that the Adirondacks get some cold -20F temps. I have a root cellar that keeps most items from freezing that I was going to use for the batteries . It is always damp there though. The inverter, if placed in the cabin, would only be 20ft away from the bank. I know you very busy but you have helped greatly. Am I correct in calculating amperage at the bank after the 300 ft run with 5awg wire as only a 6.5% loss in amps ? :confused: Thank you . Jon

[Mark Parsons]

Greetings Jon,

Have you looked into DC-DC Converters? Put one that boosts the nominal 12 volt at the Aquair to say 95 volts and then put another at the battery bank that drops it back down or forego that end and use a charge controller capable of accepting the high DC input voltage like a MX60. This would greatly reduce your wire size issue.

Here is a link to a relevant product sheet for a family capable of 200W: http://cdn.vicorpower.com/documents/datasheets/ds_vi-200.pdf

Regards,
Mark

[Rob Beckers]

The Adirondacks, that's not all that for from where I am. Pretty area!

Well, let's see if I got the calculations right:

50 Watt from 12 Volt makes for a current of 50/12 = 4.17 Ampere

5 AWG wire has a resistance of 0.3133 Ohm per 1000 feet.

For 300 feet this makes 300/1000 * 0.3133 = 0.09399 Ohm

That makes for losses per line of 4.17*4.17*0.09399 = 1.63 Watt

We have two such wires (positive and negative, since this is DC),
so the total loss is 2*1.63 = 3.27 Watt

In terms of percentage of 50 Watt this is 3.27/50*100 = 6.5%

This is a bit of a simplification, since it does not take the loss of current as a result of the increased line resistance into account, but then again it assumes somewhat of a worst case by using 12 Volts instead of the (usually higher) battery voltage. So, it should be about right.

Now that you know how to do this you can calculate it for other wire sizes and lengths. :cool:

Fully charged batteries don't freeze until the temperatures dip under -70F (-57C), and for 50% discharged batteries -10F (-23C). You want to try avoiding going below 50% discharge since battery life takes a nosedive from there. That's for flooded lead-acid, I don't have the numbers for gel or AGM lead-acid batteries handy, but they should be similar. In other words, any somewhat protected location should be fine. Some people build a battery box, and line it with rigid foam to keep the batteries from temperature swings. Besides freezing, the more profound effect of temperature is on battery capacity. At 0C (32F) the battery has about 80% of rated capacity, below freezing that gets worse. Another reason to try and keep the batteries at a reasonable temperature.

Maybe the veterans of battery care can chime in here. I don't think a damp location is an issue. You do want to be able to have a little venting. Not really because the hydrogen gas that batteries produce can explode (hydrogen disperses quickly, and it's hard to build up a concentration that's large enough to combust), but because the battery gases are acidic and will make a big mess of the wiring and battery tops if they constantly sit in corrosive gas. You would be cleaning off the battery tops all the time.

As to sizing, as mentioned you want to ensure that under normal use you don't get below 50% depth-of-discharge. So, it's a matter of adding up all the expected loads, expected production, and how long you want to run on batteries. In your case the scenario is probably one where you want to aim for no more than 50% discharge of the batteries during the day (when people are running loads), then top off the batteries during night using hydro.

Hope this makes sense!

-RoB-

[Jon Dubee]

Great information Mark and Rob. Thanks , wish I had found this site last year. Anyway Rob, Mark has suggested a DC/DC converter at the generator site , stepping up voltage to 48V running on a smaller AWG wire to the battery bank/ inverter site. Do you concur ? I have found an inexpensive 12v to 48v converter ( http://www.powerstream.com/Wire_Size.htm ) and as Mark suggested , I will drop back down to 12v at the battery bank using an MX 60 charge controller. What are your individual thoughts on this application ? The 300 ft run then presents a smaller wire which I am not sure of the resistance by gauge. I am hoping that I may use an external 16/2awg or 14/2awg. Is there somewhere to lookup this wire resistance chart? What designs problems could present themselves with this application if any? What type of grounding is needed for lightning and at which point? The generator came with a resister plate to be used at the battery side to prevent back feed. Could this then be eliminated as the DC converter is non- isolated? I have attached the specs below. Again thank you both for your expertise. I feel as I am getting closer to installation. The cabin sits on a trout pond I have stocked for 5 years if either of you like to fish.........let me know!

Converter Specs.
This DC/DC converter is useful for voltage conversion to operate 48 volt electronics off 12 volt vehicles, best for radios, stereos, DVDs, CB radios, transmitters, for example the Cisco Aironet 350 Bridge. They closely regulate the output voltage over a range of input voltages. Model Number PST-DC1248
(formerly PST-DU100-48) PST-DC2448
DC/DC Converter
Input Voltage Range 10 VDC to 15 VDC 20 VDC to 30 VDC
Peak Output Power 100 Watts (1 to 5 minutes) 100 Watts (1-5 minutes)
Peak Output Current 2Amps 2 Amps
Continuous Current 1.5 Amps 1.5 Amps
Continuous Output Power 72 Watts 72 Watts
Output Voltage 48 volts DC 48VDC
Output Range Adjustment Approximately 44 to 52 volts by internal pot (VR1) Approximately 44 to 52 volts by internal pot (VR1)
No-Load Overhead 150 mA 150 mA
Line Regulation 0.5% (± 0.12 Volts) 0.5% (± 0.12 Volts)
Load Regulation 1% (± 0.20 Volts ) 1% (± 0.20 Volts )
Efficiency over 85% over 85%
Topology DC Boost, Non-isolated DC Boost, Non-isolated
Input Connection Cigarette Plug With 1 m Long Cable Cigarette Plug With 1 m Long Cable
Output Connection 5.5mm/2.5mm DC Plug With 1 m Long Cable, center positive. (5.5mm/2.1mm DC plug or others available as an option.) 5.5mm/2.5mm DC Plug With 1 m Long Cable, center positive. (5.5mm/2.1mm DC plug or others available as an option.)
Protections: (1) Load Input Drop Out at 9.5V DC (2) Input Polarity Protect
(3) Input Fuse
(4) Output Short Circuit Protect
(5) Output Current Limited
(6) Output Over Voltage Protect (1) Load Input Drop Out at 19V DC (2) Input Polarity Protect
(3) Input Fuse
(4) Output Short Circuit Protect
(5) Output Current Limited 2 Amps
(6) Output Over Voltage Protect 52V ± 2.6 volts
Fuse size 10 Amps 10 Amps
Temperature 5 to 55°C (41 to 130°F)
Click here for dimensioned drawing
Dimensions 40 x 150 x 43 mm
1.6 x 5.9 x 1.7 inches
Weight 200 grams, 0.44 lbs

[Jon Dubee]

Rob - I found a chart. How does this calculation fair....
assuming the DC converter of 12 to 48 volt boost
Aquair max output = 100watts
Assuming max output>>

100watts from 48 V= @2.08 amps
16 awg wire has a resistance 4.016 / 1000FT or 1.2048 Ohm / 300ft

loss = 2.08ampere x 2.08ampere x 1.2048 Ohm = 5.21watts
5.21 x 2 (wires) = 10.42 , 10.42/100watts = 10.42%loss

Providing I did this right ; would this be an acceptable loss ? May I assume that proportionately if operating less than 100 watts the loss would also drop ? :confused:
Thanks Rob .

Jon

[Rob Beckers]

Jon, some time ago I published the wire losses spreadsheet I wrote for the wind turbines we import/sell. It's over here (http://www.greenpowertalk.org/showthread.php?t=191). While not so interesting for your particular application (it's for 3-phase AC), it has a little table in it with the resistance vs. wire gauge.

You nailed the calculations! If you are expecting to produce full power (100 Watt) regularly, I would try to get the losses to be a bit lower. At 10% I have a feeling that the voltage drop over the line is going to affect power output, so it won't quite be 100 Watt any more (besides the 10% losses). On the other hand, if you expect to be running at 50 Watt most of the time then these losses are fine; Just as power losses go up with the cube of the current (meaning current * current), they come down equally fast when current drops. At 50 Watt it's half the current, so 1/2 * 1/2 = 1/4 of the losses, or about 2.5%.

How well it'll work with a DC/DC converter and MX60 I can't tell. The Outback MX60 is intended for use with solar panels (photovoltaic). The software it has tries to find the maximum power point for PV, and how well that translates to hydro I don't know. It's not cheap either, thicker wires should cost less. Then there are the losses, adding an 85% efficient DC/DC converter, plus around 95% for a MX60, makes 0.85 * 0.95 = 80%, or 20% losses off the bat. Wiring losses come on top.

-RoB-

[Rob Beckers]

Jon, you mentioned grounding with regard to lightning protection. Some time ago I wrote up a very long story about just that. It mainly focuses on wind turbine use, but much of it is generic. While the recommendations there are massive overkill, especially for hydro use where the risk of a strike is very much smaller, it may still be of interest to you, to get an overview of how lightning does its thing and what to do about that.

This is a link to it. (http://www.solacity.com/Lightning.htm)

-RoB-

[Mark Parsons]

Hi Jon,

Outback specs say consult factory for approved turbines for hydro / wind applications. You may wish to see if they bless the Aquair.

Other charge controller options are available. With research you may find one that accepts the higher DC input and provides a diversion load control function. When the batteries are topped up the charge controller would divert the excess power into a heating resistor and help to keep your batteries warm. The MX60 could also perform this function in charge control mode using the AUX output.

I would use larger than 16 AWG wire. Especially if you plan to expand the system in future. I buried NMWU 12/2 wire from my charge controller to my wind and hydro turbines about 150 feet away. I recall the 12 AWG wire wasn't that much more expensive than 14 AWG, I don't think NMWU is available in 16 AWG. NMWU is direct buryable (sp) rated so dig a shallow trench and lay it in.

Mark

[Jon Dubee]

Gentleman,
I have found a source for my wire and am wondering about charge controllers. I am going to use 4/2 awg without the boost , may I be alright in using a "solar controller" that can handle 10 amps, ( 12V @ Max 100 watts= 8.3333 amps) ? Or due to the constant power input (I hope!) should a different type of controller be used? Also wondering about the rectifier on the Aquair . Could this be removed and run AC to the battery bank ? Please note attached Aquair link info. page 3 . http://www.boost-energy.com/UserFiles/Downloads/UW_100_manual.pdf

Thx. Jon

[Mark Parsons]

Hi Jon,

A 'solar charge controller' would do the job fine. When the batteries are full the power is denied. This will cause the Aquair to speed up. I'm sure the unit is designed for this eventuality.

A 'diversion controller' would make use of all the power from the Aquair. A Xantrex C40 allows both of these operating modes. Your 10 amp charge controller selection is a little tight. The Aquair is capable of over 10 amps output.

The manual you link states it is preferable to mount the rectifiers near the batteries.

Take care,
Mark

[Jon Dubee]

Mark - If I am to run 300ft with the 4 wire AC to the ratifier which would be placed next to the Battery bank, I will assume that I only need half the AWG wire gauge as seen on page 4 of the manual . Would you agree , This would allow me to use 2 wires of 8/2 AWG UF instead of 4/2 AWG . This would entail splicing off the rectifie rand splicing in at the end of the run. Thanks again !
Jon

[Rob Beckers]

It would seem that electrically there's no difference between running AC wiring (4 wires) all the way to the batteries and mount the rectifier there, vs. running DC wiring (2 wires, double the size of the AC wires) from a location close to the turbine, with the rectifier also mounted in close proximity to the turbine. Whichever is cheaper to do.

When using a solar-type charge controller (they disconnect the batteries from the turbine when fully charged) be aware that the unloaded voltage of the Aquair is much higher than 12 Volt. According to the table on page 13 it can go as high as 47 Volt! Be sure that whatever controller you are using is capable of handing this input voltage.

Jon, let us know how the install goes, and post some pictures!

-RoB-

[Jon Dubee]

Ron - Is the Xantex C40 a better charge controll choice considering the 47 possible volts output? I am also looking for a good source for my batteries if you can suggest anyone. Thanks.

[Rob Beckers]

Hi Jon,

A Xantrex C40 should certainly do the job, if anything it is overkill since it can handle 35 Ampere while your turbine doesn't normally go above 10 Ampere. It can handle an input voltage of 55 Volt, so you should be OK in that area too.

We've been talking about using a series-type controller (as one would for solar panels). That works, but you're throwing away potential energy from the turbine at the times that the batteries are full. By using a charge controller as a diversion controller (so it sits parallel to the batteries) you could use the excess energy to do something else, such as water heating. Then again, maybe with the loads you have there won't be much time when the batteries are actually full for extended periods. The C40 can be used either way, series or diversion controller.

As to battery suggestions; as mentioned before it's nearly impossible to say anything without having a really good idea of the loads you're going to have, and when they'll be drawing down the batteries. What it comes down to is that you do not normally want to draw down the batteries to less than 50% of capacity, and be able to recharge them within a reasonable time. Going below 50% on a regular basis and/or rarely giving batteries a full charge are the fastest ways to kill a set of perfectly good batteries. Within those parameters you have to estimate the needed battery size in Amp-hours. There are several good brands of batteries, Deka/East-Penn, Surrette, Trojan. They all make multiple sizes, they all publish how many cycles to expect (so you can estimate life-time and "per cycle" cost). It comes down to what brand(s) you can get locally without paying for shipping, and how much you want to pay for batteries (the more expensive ones tend to be cheaper in the long run because they give you more cycles).

-RoB-

[Rob Beckers]

Jon, snap a few pictures when you install the turbine! Let us know how it goes, and how well it works.

-RoB-

[Stellar Gellar]

wow thanks for the info here. :bigsmile: