Running an electric cooler in my van on solar

[winnie]

Clearly the answer is to use a Crosley Icyball. https://en.wikipedia.org/wiki/Icyball

Though I admit to being partial to using CO2 fire extinguishers to make dry ice as needed.

To seriously answer the OP: if you actually want to run a cooler using solar power you will certainly need to charge a battery and then use the battery to run the cooler. The cooler will very likely not play nice with changing power output as sun conditions change. This means that you would need at least some energy storage.

With that said, small fridges tend to be inefficient, especially 'solid state' fridges. The 'use ice' suggestion is the one I'd follow, unless for some reason you need a refrigerator on site; say for precise temperature control above freezing, or because you go on long trips away from your 'home base' ice source, or because you really really want the convenience of being able to make cold 'on demand' and not need to plan ahead for ice.

If you really want to use solar power to for cooling, you are better off getting solar panels installed on your home and using your home freezer to make ice.

-Jon

 

[dereckbc]

http://www.amazon.com/Blue-Sea-Sy...&redirect=true&ref_=oh_aui_detailpage_o06_s00


It's called an "automatic charging relay". When it senses charging, it combines the batteries and both get charged. When not charging it isolates the batteries so you don't run down the starting battery. It differs from a "battery isolator" in that it doesn't use a diode. I checked on the "isolator" but found out that due to voltage drop across the diode that you never truly get a full charge.

I bought a motorcycle battery and put it behind the seat. I use it for my inverter. I don't keep a cooler cold with it but I suppose I could. Mainly for battery chargers and times when I may need to power something small temporarily.

Bill that is not entirely correct, and leading you to the wrong conclusion. Depends on who's Isolator you use. The ones I linked to from Sure Power are Manufacture specific like Ford, GM, Chrysler, and so on. Why Manufacture Specific is the question you need to ask. The reason is the voltage regulation is taken out of the Alternator, and put into the Isolator voltage regulator. The Ports can be set to whatever voltage your specific battery requires from 13.2 to 13.8 volts.

You are correct using the Diode types, but they are even better than Mechanical Relay types. Vehicle batteries are SLI batteries, and vehicle alternators run at higher voltages (14.2) than Deep Cycle battery requirements of 13.2 to 13.6 volts. So the Diode types actually drop the voltage down to something more usable and friendly to the Deep Cycle battery.

Mechanical types have a nasty habit of contacts being welded together. When the Deep Cycle battery is discharged, the voltage is lower than the SLI battery. When you close the relay, you exceed the relay contacts current rating capacity, thus welding/melting the contacts together. The only thing that regulates the current is the wire resistance and battery Internal Resistance. The flip side of that coin is burned and pitted contacts when the relay opens under DC load. Either side of that coin is failure.

 

[dereckbc]

It's great being able to run one battery set totally dead and still be able to start the vehicle.

Don't make a habit of doing that. Deep Cycle batteries don't take kindly being fully discharged.

73.s

KF5LJW

 

[K8MHZ]

Don't make a habit of doing that. Deep Cycle batteries don't take kindly being fully discharged.

73.s

KF5LJW

Well, then they should be called Shallow Cycle batteries instead.

 

[Fulthrotl]

Well, then they should be called Shallow Cycle batteries instead.

shallow cycle is what you end up with after you zorch your deep cycle batteries a couple times.

i've been using oddesy batteries for a while now, and they aren't all that tolerant of zorching,
and they are about the best i've found for recovery.

 

[dereckbc]

Well, then they should be called Shallow Cycle batteries instead.

Yeah I know it is ironic. Seriously you do not want to go more than 50% DOD, or ever leave a Pb battery in any discharged state as that is a recipe for short battery life. In solar system to get maximum battery life of 4 to 6 years, you only discharge them 20% DOD per day. That gives you about 2-1/2 3 Cloudy days before you hit 50% DOD, and have to go on a generator to recharge. Pb are just not ideal for Partial State of Charge applications. Lithium is great for that, but today is just not economical.

Trojan has come up with some Pb improvements with what they call Carbon Technology, but you have to pay extra for it in their Renewable Energy and Industrial product lines. It considerable slows down sulfation.

 

[mgookin]

Yeah I know it is ironic. Seriously you do not want to go more than 50% DOD, or ever leave a Pb battery in any discharged state as that is a recipe for short battery life. In solar system to get maximum battery life of 4 to 6 years, you only discharge them 20% DOD per day. That gives you about 2-1/2 3 Cloudy days before you hit 50% DOD, and have to go on a generator to recharge. Pb are just not ideal for Partial State of Charge applications. Lithium is great for that, but today is just not economical.

Trojan has come up with some Pb improvements with what they call Carbon Technology, but you have to pay extra for it in their Renewable Energy and Industrial product lines. It considerable slows down sulfation.

10-15 years ago I was reading an article where the author suggested golf cart batteries (gel, I believe) because they are used to getting a full charge and being heavily drained, charged, repeat.

Anyone agree or disagree? Or have a preferred battery technology for solar?

 

[GoldDigger]

10-15 years ago I was reading an article where the author suggested golf cart batteries (gel, I believe) because they are used to getting a full charge and being heavily drained, charged, repeat.

Anyone agree or disagree? Or have a preferred battery technology for solar?

Golf cart batteries have their place in RE, as do forklift batteries. But they are not ideal for many situations. The biggest advantage, IMHO, to golf cart batteries is their low cost and high availability for a first system. Once you have made all of your mistakes you can go for the more expensive batteries.
I do not think sealed batteries, neither AGM nor GEL, are commonly used in golf carts.
The typical GEL battery is no good for PV use because it cannot be recharged at a high enough rate for solar purposes.
And, of course, when it is available the power grid is your best "battery" for energy storage.

 

[jaggedben]

If it's not already out of date to say lithium isn't economical, I think it will be within the next few years. That may apply better to somewhat larger scales where the BMS is cost effective, rather than the OP's goal.

 

[GoldDigger]

If it's not already out of date to say lithium isn't economical, I think it will be within the next few years. That may apply better to somewhat larger scales where the BMS is cost effective, rather than the OP's goal.

There is a strong argument that by preparing the pack initially "by hand" and then keeping it within the 20% to 80% SOC range you are actually better off without a BMS. At least when using LiFePO4.

 

[dereckbc]

10-15 years ago I was reading an article where the author suggested golf cart batteries (gel, I believe) because they are used to getting a full charge and being heavily drained, charged, repeat.

Anyone agree or disagree? Or have a preferred battery technology for solar?

Well first there were no Gel Golf Cart batteries 10 years ago, at least none worth having. Gel batteries are just not a good solution for long term energy storage, and really bad for Solar. Gel is perfect for Float , slow charged Emergency Stand-By power like Emergency Egress lighting, and Fire Alarm where they are used. Gel big downfall for the most part is they require slower charge rates at lower voltages. They cannot tolerate fast or over charging. Charge them too fast, and you dry out the electrolyte Gel leaving voids and cracks which is permanent damage. Solar and RE applications including Golf Carts require much faster charge rates up to C/4 and higher. Gel batteries just cannot handle that and typically charged at C/20 rate. Second fact is Gel batteries cost twice as much as FLA and last half as long. That makes them some 400% higher cost than FLA. So much for Gel batteries.

Golf Cart batteries like Trojan T-105's are really hybrid batteries as opposed to a true Deep Cycle battery. They operate on a different end purpose. They are intended to be discharged 80% DOD daily and recharged over night, and last 2-3 years. If they match your solar application daily watt hour needs, no greater than say 50% DOD daily, make a great beginners battery. Used in that fashion will last 3 or 4 years with great care. But beginners will never likely experience that as they usually destroy their first set of batteries. As stated Golf Cart batteries are readily available and inexpensive. But make no mistake they are not ideal solar batteries. For that you want a true deep cycle battery. Example Trojan also makes a T-105RE, their Renewable Energy product line. Now I know some of you are saying to yourself it is the same battery as the T-105, but you would be dead wrong. The T-105RE is a True Deep Cycle battery. Don't believe me huh? Well check out the specs yourself. The T-105 is a 62 pound battery, and the T-105RE is a 67 pound battery in the exact same case. The T-105RE have heavier thicker plates. Warranties are different The T-105 is 2-year warranty, and the T-105RE is 5 years.

As for AGM Golf Cart batteries they do exist. But like Gel's, AGM cost twice as much and last half as long as FLA. AGM has their place as they can be charged and discharged at much higher rates, do not freeze as easily. amd do not spill so they have their place, but you will pay for it.

 

[mgookin]

About 15-20 years ago we had golf course developers (Lennar) spec'ing gel batteries in the golf cart storage areas (it's a ventilation thing).
I can't speak for whether they were "any good" and I'm not saying they're any good for solar. I was only referring to something I read a long time ago.
Thanks for the insight.

Maybe OP should buy a dorm fridge and plug into the t-pole on the jobsite.

 

[GoldDigger]

About 15-20 years ago we had golf course developers (Lennar) spec'ing gel batteries in the golf cart storage areas (it's a ventilation thing).
I can't speak for whether they were "any good" and I'm not saying they're any good for solar. I was only referring to something I read a long time ago.
Thanks for the insight.

Maybe OP should buy a dorm fridge and plug into the t-pole on the jobsite.

If they needed batteries which did not vent gasses under normal use they should have gone to AGM batteries, not GEL. Both are categorized as Valve Regulated Lead Acid (VRLA) but they have very different electrical characteristics, as described by Dereck.

 

[Little Bill]

Bill that is not entirely correct, and leading you to the wrong conclusion. Depends on who's Isolator you use. The ones I linked to from Sure Power are Manufacture specific like Ford, GM, Chrysler, and so on. Why Manufacture Specific is the question you need to ask. The reason is the voltage regulation is taken out of the Alternator, and put into the Isolator voltage regulator. The Ports can be set to whatever voltage your specific battery requires from 13.2 to 13.8 volts.

I read several articles and visited a couple of forums for boat owners and everyone to a
tee said the same thing about the isolators. They even listed the voltage drop of .7V that "K8MHZ" mentioned.
That's all I have to go on as I've never had one or measured the voltage and/or drop.
That's also why I chose the "ACR" (automatic charging relay) because it made sense.
I checked the voltage after I hooked it up and had 13.78V when the relay was closed and battery was charging.

 

[dereckbc]

If it's not already out of date to say lithium isn't economical, I think it will be within the next few years. That may apply better to somewhat larger scales where the BMS is cost effective, rather than the OP's goal.

Cost analysts models tell the story. With respect to Solar Off Grid systems in the USA you are pretty much limited to using Chi-Com LiFeP04 large prismatic cells as that is about all you as a consumer can buy and afford. Example a CALB 100 AH cell runs you about $160 per cell or $500/Kwh. A CALB cell is claimed to last 2000 cycles or 5 years which ever comes first. Consumers cannot access premium cells from like A123, but even if you could the cost jump to $2000/Kwh. So in the model I will use CALB cells. For FLA batteries a good high quality 5 year Rolls series 5000 battery cost $220/Kwh.

With LiFeP04 you size the batteries for 3-day autonomy to equal FLA 5-Day Autonomy. So for 1 Kwh-day requires a 3-Kwh LFP, and 5-Kwh FLA. So a LFP cost = 500-Kwh x 3 = $1500, and FLA cost $220-Kwh x 5 = $1100. So just on that alone is significant difference. But what is really interesting is what are the Kwh cost just for the batteries. This is something you have to be aware of, especially if you plan on taking something Off-Grid. You would be surprised how many people think it is less expensive to go off-grid. But is it really?

Both models deliver 1 Kwh per day of usable power. In 5 years at end of life when it is time to replace the batteries will have delivered 1826 Kwh. So each Kwh battery cost alone is:

FLA = $1100 / 1826-Kwh = $0.602/Kwh
LFP = $1500 / 1826-Kwh = $0.821/Kwh

What does your utility charge for a Kwh delivered? Where I live in TX with all charges added up is just under $0.09/Kwh for the first 2500 Kwh in a monthly cycle, and drops to just less than $0.08/Kwh for anything over 2500/Kwh in a monthly cycle. I would be looking at a voluntary self inflicted 600 - 1000% rate increase to go off-grid. No thank you, I will pass on that. Then some will say well I do it to have less environmental impact which is a false narrative. At least for FLA batteries it takes more energy to make the batteries, than they are able to deliver over their life cycle. It has a negative Energy Return On Investment or EROI. You would be wasting energy. As for LFP I have not ran the EROI numbers because no data exist that I can find.

 

[dereckbc]

There is a strong argument that by preparing the pack initially "by hand" and then keeping it within the 20% to 80% SOC range you are actually better off without a BMS. At least when using LiFePO4.

I think you might be referring to Bottom Balance which has merit. But from a commercial product POV is not doable. A commercial product is forced to use Top Balance which requires a BMS.

I have converted 3 golf carts to NEV's in the last 5 years. First one I used standard FLA Trojan 8-volt golf cart batteries for a 48 volt configuration and 400 pounds of dead weight in batteries. Pretty boring when used with a Series Wound DC motor and 500 amp controller. 30 mph was about it. Sold that cart, and bought another used one for second project.

Second Project I used GBS LiFeP04 (LFP) configured 16S (48 volt) 100 AH cells, an AC 3-phase Induction Motor, and a 550 amp Controller. Lifted the golf cart 3-inches, changed the differential gear to 6:1, and 22-inch tires. It was a little more exciting at 50 mph. I Bottom Balanced the cells. After about 6-months I noticed a capacity loss and was disappointed with Chi-Com cells. So for my third project was really just an upgrade. A friend and I found a salvaged Nissan Leaf and bought the battery pack and divided it up. I removed the GBS cells, and controller. In their place I used the Leaf Cells configured at 96 volts @ 66 AH, and upgraded to a 650 amp controller. The cart now goes 72 mph at 7000 RPM limit and get to 72 mph in about 6-7 seconds. Battery pack now weighs 200 pounds, half of FLA with a range of about 50 miles. I bottom Balance the Leaf Cells.

Point here is Bottom Balance Lithium can realistically only be done by someone with a good operating knowledge of lithium cells. As you noted a BB pack is never charged to 100% or allowed to go below 10-20%. This doubles cycle life. But as a Consumer Product is just not feasible or technically possible to have a BMS using Bottom Balance. Thus Consumers are stuck with Top Balance systems.

 

[jaggedben]

.Thanks for numbers. I haven't been keeping close track, but I gather lithium numbers have come down quite a bit and will continue to. Am I wrong?

Depends on which market you are talking about. I design build quite a bit of Off-Grid systems for Cellular Telephone companies, help homeowners with remote log cabins, and piddle with DIY EV's-NEV's, and Golf Carts. Telco's are strictly Lead Acid users as it is proven and still the most economical for now.

In the lithium Market there are really two markets. Commercial applications of EV's and Consumer Electronics. Joe Blow has very little access to grade A Commercial grade lithium batteries like Panasonic (Tesla EV) LG Chem, Sanyo, etc. About the only commercial grade Lithiums you and I can get access too are A123 Systems. Problem with that is the cost around $2-Kwh.

For the rest of of us we have Chi-Coms like CALB, Winston, Sinopoly, and GBS. Those are the large Prismatic cells as small as 40 AH to 400 AH per cell (3.2 volts). Initially back in 2007/2008 when they were released cost were high at $1.50 WH. That declined to around 40-cents per WH late 2014, bottom out by end of 2014, and have started to rise to about 45 - 50 cents per Kwh today. So those are as cheap as those are going to get for now.

The only other Market we can tap is the Battery Module sector like 12 volt units like Car, Trolling Motors, RV etc. But those cost are fairly high at $1.20 to $1.50 WH.

Kind of hard to justify when you can buy a top of the line Lead Acid battery that will last as long or longer (5-6 years) at 21 - 24 cents per WH

Also at a certainly point some advantages to the lithium batteries (lighter, smaller, less maintenance) start to kick in, no? Obviously a lot less important for stationary applications though.

True but you have to justify the cost like an EV where weight and space are at a premium. Weight and Space is not really a factor in a stationary Off-Grid system in your home or cabin.


EDIT NOTE:

Please accept my apologies for messing up your post. I screwed up and used EDIT instead of QUOTE. My bad.

 

[kwired]

You would be surprised how many people think it is less expensive to go off-grid. But is it really?

To be clear, I'm not one of those people. Exception might be a building that has never been on the grid

I agree, and will add a remote location may cost a lot to get the grid to it. And if the actual power used is not all that high might take a long time to get a return on investment. Life expectancy of on the grid supply equipment is likely much longer then off the grid equipment.

 

[iwire]

You would be surprised how many people think it is less expensive to go off-grid. But is it really?

I did not want to go off grid I just wanted to save money so I contacted a vendor that sold PV equipment and I was impressed that they where honest. They told me the best way for me to save money while on the grid was to buy more efficient appliances.

They said unless I was off grid PV was not going to save me money. Of course this was about 5 years ago but I was impressed they where up front with me instead of just selling me a bunch of equipment.

 

[dereckbc]

I did not want to go off grid I just wanted to save money so I contacted a vendor that sold PV equipment and I was impressed that they where honest. They told me the best way for me to save money while on the grid was to buy more efficient appliances.

They said unless I was off grid PV was not going to save me money. Of course this was about 5 years ago but I was impressed they where up front with me instead of just selling me a bunch of equipment.

Lucky you, most would not do that. Once they got you trapped into Off-Grid, they have a pigeon to pluck for life replacing batteries. :ashamed1: