battery setup with future solar expansion

mojorisin · June 2014

Hello all, this is a great forum and I am grateful to have come across it. I've gone through numerous articles and think I'm beginning to pick up the design aspects of a solar system.

my electrical needs are as follows:

2 refrigerators - ~6amp, ~4.9amp
large exhaust fan - 3.3 amp (I've wired in a speed controller so have control of current use)
espresso machine - 10 amp (maintains pressure while idle pretty well, i expect the surge to 10 when actually in use)
grinder - 3.2 amp (intermittent use)
blender - 10 amp (intermittent use)
food processor - 10 amp (intermittent use)
electronics - phone charger ~0.5 amp, laptop charger ~4 amp
battery bank charger - ???

I have installed a panel box with the intention of have 2 main inputs (with independent 30amp breakers), depending on the situation. Ideally we will have power available that will supply 120VAC at 30 amps. the other option is a 4kw, 30 amp onan generator

Now, I have a 12vdc shurflo water pump that needs power, and I'd like to be able to power my refrigerators while on the road. So how do I size these power needs accordingly?
I'm saying 6 hours max on battery duty, would more likely be closer to 1-2 hours when away from a plug and/or stop to use generator.

water pump: 12vdc, 7.5amps max I believe this is when first starting the system with priming and getting pressure everywhere.. assume 4 amps?
@ 12vdc - 4 amp x 6 hours = 24AH
fridge 1: 120vac x 6 amp (again, cycling... safe to assume half?) 120vac x 3 amp = 360 watt / 12vdc = 30 amp x 6 hour = 180AH
fridge 2: 120vac x 4.9 amp (assume half, 2.5 amp) 120vac x 2.5 amp = 300 watt / 12vdc = 25 amp x 6 hour = 150AH

total load for battery sizing ~ 354AH

I was looking at the 6v, 225AH Trojan deep cycles. 4 of them in series/parallel = 12VDC, 450AH
what would be recommended for a battery charger when plugged in?
what would be a recommended inverter?

I've talked to a couple solar guys in my area (Florida) and the consensus is to determine loads required, size the bank then go from there. One of them has some used 100w panels (monocrystalline? unsure, he said they were the oldest/best type of panel) for 100$ each. Is that a decent deal?

I understand this is a lot of information.. I appreciate any and all input.

Thanks

AuricTech · June 2014

Re: battery setup with future solar expansion

mojorisin wrote: »

Hello all, this is a great forum and I am grateful to have come across it. I've gone through numerous articles and think I'm beginning to pick up the design aspects of a solar system.

I am building a mobile kitchen (food truck) and have some design questions I'd like to get some feedback on if possible. my electrical needs are as follows:

2 refrigerators - ~6amp, ~4.9amp
large exhaust fan - 3.3 amp (I've wired in a speed controller so have control of current use)
espresso machine - 10 amp (maintains pressure while idle pretty well, i expect the surge to 10 when actually in use)
grinder - 3.2 amp (intermittent use)
blender - 10 amp (intermittent use)
food processor - 10 amp (intermittent use)
electronics - phone charger ~0.5 amp, laptop charger ~4 amp
battery bank charger - ???

Are these loads all at 120VAC?

Cariboocoot · June 2014

Re: battery setup with future solar expansion

Welcome to the forum.

Your loads are not trivial. Refrigeration has large start-up demands and consumes significant Watt hours. What's more the nature of use means predicting the Watt hours of other devices is pretty much impossible. Fortunately you have a generator for when the batteries go down and so does the sun.

You do not want a 12 Volt system if it is at all possible to avoid it. It would be better to run the 12 Volt pump from a DC to DC converter than to put up with the high current demand on 12 Volts the rest of the equipment will demand.

Do not try to estimate loads in Amp hours. Always use Watt hours. Only convert to Amp hours when sizing battery banks. That way the power requirements can be added together equally regardless of whether they are 120 VAC or 12 VDC.

And while we're on the subject of estimating loads, since you already have the equipment get a Kill-A-Watt meter and measure each item under typical usage conditions. You may be amazed at how different this is from calculated estimates.

450 Amp hours @ 12 Volts or 225 Amp hours @ 24 Volts is not a lot of power when it comes to running to refrigerators, never mind the rest of it. You're realistically looking at 2.4 kW hours for those batteries @ 50% DOD, and the 'friges will just about eat that up or I miss my guess.

Time of use will make a difference too, as PV can provide some power directly during daylight hours. Being mobile unfortunately puts a limit on how much PV you could have.

How much do you want to run that generator? How much power must you supply from batteries in between grid connection times or gen run times? These are important considerations.

mojorisin · June 2014

Re: battery setup with future solar expansion

AuricTech wrote: »

Are these loads all at 120VAC?

my apologies. yes all of these are 120VAC, the only required 12VDC is the water pump

mojorisin · June 2014

Re: battery setup with future solar expansion

You do not want a 12 Volt system if it is at all possible to avoid it
I've seen that in the forums before and it did not dawn on me as too why.. because of the high current and subsequently the bigger gauge wires?

It would be better to run the 12 Volt pump from a DC to DC converter
do you mean AC to DC?

Do not try to estimate loads in Amp hours. Always use Watt hours
Thank you for the tip, I was getting a little confused going from unit to unit, I understood AH for battery sizing... it is appreciated.

get a Kill-A-Watt meter
picking one up tomorrow. makes sense to see what the appliances are actually pulling instead of wild estimates

How much do you want to run that generator? How much power must you supply from batteries in between grid connection times or gen run times? These are important considerations.
My original thought was I have this real estate on my roof (~8'x18') to mount panels that could power my batteries that are needed to power fridges while in transit.. or in case of emergency. When parked at my house I'll always have the truck plugged in, so the fridges will always be cold. When its time for an event, unplug, switch fridges over to inverter/batteries and go. Arrive at destination, either plug in or start up the genset. If when I'm out and about I can get 4-5 hours of good sun why not have the means to charge up the batteries.

How much power must you supply from batteries in between grid connection times or gen run times
I guess the watt meter will tell me that... 2 fridges which should start cold, switched over to inverter/battery..

I appreciate your time caribocoot
Thanks

mojorisin · June 2014

Re: battery setup with future solar expansion

mojorisin wrote: »

my apologies. yes all of these are 120VAC, the only required 12VDC is the water pump

in hind sight I should of gotten an AC water pump... but then I wouldnt of starting researching batteries, then chargers/inverters, then panels, then never found this forum, etc etc

Cariboocoot · June 2014

Re: battery setup with future solar expansion

mojorisin wrote: »

You do not want a 12 Volt system if it is at all possible to avoid it
I've seen that in the forums before and it did not dawn on me as too why.. because of the high current and subsequently the bigger gauge wires?

It would be better to run the 12 Volt pump from a DC to DC converter
do you mean AC to DC?

Nope: DC to DC. A unit that drops higher battery Voltage to lower DC Voltage so you can run a 12 Volt pump from a 24 Volt battery bank. One example: http://www.solar-electric.com/sa24voto12vo.html

How much do you want to run that generator? How much power must you supply from batteries in between grid connection times or gen run times? These are important considerations.
My original thought was I have this real estate on my roof (~8'x18') to mount panels that could power my batteries that are needed to power fridges while in transit.. or in case of emergency. When parked at my house I'll always have the truck plugged in, so the fridges will always be cold. When its time for an event, unplug, switch fridges over to inverter/batteries and go. Arrive at destination, either plug in or start up the genset. If when I'm out and about I can get 4-5 hours of good sun why not have the means to charge up the batteries.

It sounds like you'll need to base your battery bank on the amount of power used between AC hook-ups, and possibly that will be only keeping the refrigeration going in transit? That will be much easier than trying to supply the whole lot. Your PV, if any, is going to be limited to how much you can fit. Don't be surprised if this reduces it to merely extending battery time; full charging will probably need to be done by the next AC connection.

ILFE · June 2014

Re: battery setup with future solar expansion

mojorisin wrote: »

I've talked to a couple solar guys in my area (Florida) and the consensus is to determine loads required, size the bank then go from there. One of them has 8 used 100w panels (monocrystalline? unsure, he said they were the oldest/best type of panel) for 100$ each. Is that a decent deal?

First, let me preface this by saying I am NOT in the US. Nor have I resided in the US in almost 15 years. (I currently live in Cambodia.) So, I am only going by what I read others are finding in the US.

If I were you, I would consider looking at current pricing for solar panels, due to the drop in cost of them over the couple / few years. I would imagine that you should be able to get what you are looking for, brand new, for that price - if not cheaper, shipped to you.

So, in my opinion - no, it isn't that great of a deal. Look around, though, first, to make sure what I am saying is accurate.

mojorisin · June 2014

Re: battery setup with future solar expansion

Cariboocoot wrote: »

Nope: DC to DC. A unit that drops higher battery Voltage to lower DC Voltage so you can run a 12 Volt pump from a 24 Volt battery bank. One example: http://www.solar-electric.com/sa24voto12vo.html

It sounds like you'll need to base your battery bank on the amount of power used between AC hook-ups, and possibly that will be only keeping the refrigeration going in transit? That will be much easier than trying to supply the whole lot. Your PV, if any, is going to be limited to how much you can fit. Don't be surprised if this reduces it to merely extending battery time; full charging will probably need to be done by the next AC connection.

I see. Since I have AC power (shore or genset) I thought an AC to DC converter.. but if I were to have a system higher than 12v I can step down. Seems to be a piece of hardware for everything.

Those trips will most likely be between 30 minutes to a couple of hours. I am going to setup the watt meter and see if more accurate estimates can be had, then size the bank. Are there any other disadvantages to using 12VDC besides needing heavier gauge wire, and requiring it for 12VDC equipment? If everything else needing power is 120VAC then going to an inverter with higher voltage seems logical.

What are some above average brands of batteries out there? I've also read to avoid parallel configurations if possible.. what is the thought there?

Thanks again

Cariboocoot · June 2014

Re: battery setup with future solar expansion

mojorisin wrote: »

I see. Since I have AC power (shore or genset) I thought an AC to DC converter.. but if I were to have a system higher than 12v I can step down. Seems to be a piece of hardware for everything.

Those trips will most likely be between 30 minutes to a couple of hours. I am going to setup the watt meter and see if more accurate estimates can be had, then size the bank. Are there any other disadvantages to using 12VDC besides needing heavier gauge wire, and requiring it for 12VDC equipment? If everything else needing power is 120VAC then going to an inverter with higher voltage seems logical.

What are some above average brands of batteries out there? I've also read to avoid parallel configurations if possible.. what is the thought there?

Thanks again

Avoiding parallel battery connections is a good idea because keeping the current flow even through the parallel strings becomes problematic. Not impossible, just more likely to go wrong. Increasing the system Voltage can eliminate this problem by storing the same amount of energy in one string of batteries instead of two (for example). Higher Voltage systems are more efficient: for any given Watt output the power is delivered more as Voltage than as current, and current creates heat. Heat is energy that is being used but not doing any work. That's why we try to avoid it.

Battery brands. Oh boy. That's a hot topic all right. From what I've seen your best off with the cheapest you can get, especially for a first set because it is so easy to ruin batteries.
Surrettes are to be avoided in my opinion. They are expensive and there have been many reported problems with them. Not so many problems with Trojan, but again they come at a premium price.
Crown, Deka, East Penn, US Battery - all seem to be 'happy owner' reports. Likewise the no-name warehouse golf cart batteries.

mojorisin · June 2014

Re: battery setup with future solar expansion

ILFE wrote: »

First, let me preface this by saying I am NOT in the US. Nor have I resided in the US in almost 15 years. (I currently live in Cambodia.) So, I am only going by what I read others are finding in the US.

If I were you, I would consider looking at current pricing for solar panels, due to the drop in cost of them over the couple / few years. I would imagine that you should be able to get what you are looking for, brand new, for that price - if not cheaper, shipped to you.

So, in my opinion - no, it isn't that great of a deal. Look around, though, first, to make sure what I am saying is accurate.

Thanks for the tip.. will do

mojorisin · June 2014

Re: battery setup with future solar expansion

Cariboocoot wrote: »

Avoiding parallel battery connections is a good idea because keeping the current flow even through the parallel strings becomes problematic. Not impossible, just more likely to go wrong. Increasing the system Voltage can eliminate this problem by storing the same amount of energy in one string of batteries instead of two (for example). Higher Voltage systems are more efficient: for any given Watt output the power is delivered more as Voltage than as current, and current creates heat. Heat is energy that is being used but not doing any work. That's why we try to avoid it.

Battery brands. Oh boy. That's a hot topic all right. From what I've seen your best off with the cheapest you can get, especially for a first set because it is so easy to ruin batteries.
Surrettes are to be avoided in my opinion. They are expensive and there have been many reported problems with them. Not so many problems with Trojan, but again they come at a premium price.
Crown, Deka, East Penn, US Battery - all seem to be 'happy owner' reports. Likewise the no-name warehouse golf cart batteries.

Ah, yes that makes perfect sense.
I appreciate your input, I will report back with the watt meter findings and other confirmations.

Thanks

BB. · June 2014

Re: battery setup with future solar expansion

Are you building a coffee truck or similar lunch coach? Restaurants are notorious for their large power consumption (heating lots of food/drink, hot water for cleaning, large refrigeration for food, etc.).

Conservation is your friend--But not always possible in a commercial environment. Propane can be a big help (pretty dense energy storage vs a lead acid battery bank). It is getting close to where certain Li-ion chemistries are becoming cost competitive--But that is just another variable here--You already have a lot of those.

-Bill

vtmaps · June 2014

Re: battery setup with future solar expansion

Cariboocoot wrote: »

It would be better to run the 12 Volt pump from a DC to DC converter than to put up with the high current demand on 12 Volts the rest of the equipment will demand.

I have a 24 volt system, an inverter, and a 12 volt shurflo pump. I use a 12 volt power supply (that runs from my 120 volt inverter or generator) rather than a DC to DC converter. The power supply is much cheaper than a DC to DC converter.

One thing for sure... don't buy a 120 volt shurflo pump. Here's why:
http://forum.solar-electric.com/showthread.php?22792

--vtMaps

mojorisin · June 2014

Re: battery setup with future solar expansion

BB. wrote: »

Are you building a coffee truck or similar lunch coach? Restaurants are notorious for their large power consumption (heating lots of food/drink, hot water for cleaning, large refrigeration for food, etc.).

Conservation is your friend--But not always possible in a commercial environment. Propane can be a big help (pretty dense energy storage vs a lead acid battery bank). It is getting close to where certain Li-ion chemistries are becoming cost competitive--But that is just another variable here--You already have a lot of those.

-Bill

Yes liquid propane will run 3 major appliances and a water heater. I went with LP for the major power requirements to lessen my electrical needs. It seems most mobile kitchens inherently have to do a power dance depending on the situation.

mojorisin · June 2014

Re: battery setup with future solar expansion

vtmaps wrote: »

I have a 24 volt system, an inverter, and a 12 volt shurflo pump. I use a 12 volt power supply (that runs from my 120 volt inverter or generator) rather than a DC to DC converter. The power supply is much cheaper than a DC to DC converter.

One thing for sure... don't buy a 120 volt shurflo pump. Here's why:
http://forum.solar-electric.com/showthread.php?22792

--vtMaps

I see, I will look into the 12v power supply run off AC power. I appreciate the heads up on the 120VAC version of shurflo's pump. I currently have the 4088

battery setup with future solar expansion

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