Battery selection

[Szabie]

Hi guys as I have the wrong type batteries ie telecom ones that are not designed for daily usage I was looking for advice on new ones . What I am running is a fridge freezer which I hook directly to batteries as it only 12/24 v . Through the inverter I run small tv stereo toaster . I have 6 x solar panels 210 w 5 .95 a in parellel a Morningstar 60 charge controller to a enerdrive 24 v inverter / charger . As the fridge is direct to the battery I turn the inverter off during the day so there is no loads from inverter unless I'm in camp . The batteries I am looking at are off eBay they are 2x pro power 280ah agm deep cycle batteries that will set me back $1350 would they be ok for my situation or should I keep looking for better ah etc Thanks

[jflorey2]

First figure out your ENERGY (not power) requirement. You can do this roughly by measuring the current while the fridge is running, then noting how long it's on and how long it's off. If it takes 10 amps at 12 volts while it is running, and it runs half the time, then per day you are going to need (120*.5*24=1440) watt hours a day, or 120 amp hours a day. Then add the additional energy you need for your toaster etc.

Let's say you need 200 amp hours a day with all your loads at 12 volts. That means you are going to need about 1200 amp hours total (3 days to 50%.) Six S2-1175 batteries from Rolls will run you around $3810. Do NOT get AGM; from your info so far you will probably abuse the batteries, and AGM's do not recover from abuse very well.

[Mike90250]

Since this is going to be a grand experiment anyway,
try 4 cheap golf cart batteries. ($500 total) Wire in series for 24V
Get a 24V 400w pure sine inverter for the TV and and small electronics ($300)
Get a separate 24V 2,000w mod sine inverter for the toaster. ($250)
Way less expensive than the giant AGM batteries you can't lift or afford

You will soon learn if you need more PV or more batteries.

[Sunking]

As Jeff says you are going about this wrong. You have to know your daily watt hour requirement, location, and time of year use. Then you design a system that will work, not hope and pray.

But here is what I can tell you just based on what you have. You have 1260 watts panels improperly configured if they are in parallel. With your controller and 6 panels you want your panels configured 3S2P. With 1260 watts the minimum battery you can safely use is 24 volts @ 400 AH up to 24 volts @ 600 AH. Presuming you are in a good location can provide you with 2 Kwh up to 3 Kwh per day which may or may not be enough.

You do not want to use AGM unless you have a specific reason. 280 AH is not large enough. AGM cost twice as much as FLA and last half as long. That means 400% higher cost than flooded. So unless you have money to burn or need a AGM performance, no reason to throw away money.

You DO NOT WANT to parallel batteries. If you want 400 AH buy 400 AH batteries. Do not buy batteries from Flea Bay. A decent quality battery that is not overly expensive is US Battery model # US RE L16 XC2 a 6-volt 400 AH battery so you would need 4 of them. Moving up in quality is a Trojan L16P a 6-volt 420 AH battery.

[Sunking]

Since this is going to be a grand experiment anyway,
try 4 cheap golf cart batteries. ($500 total) Wire in series for 24V
Get a 24V 400w pure sine inverter for the TV and and small electronics ($300)
Get a separate 24V 2,000w mod sine inverter for the toaster. ($250)
Way less expensive than the giant AGM batteries you can't lift or afford

You will soon learn if you need more PV or more batteries.

Mike normally I would agree with that tactic for a beginner. Problem I see is with 1260 watts @ 24 volts is 52 amps of charge current. A bit much for 200 to 225 AH FLA golf cart batteries don't you think? Trojan T-105 can do that, but budget GC batteries is a bit to much IMHO. He can do that with AGM, but a 225 AH AGM cost as much or more than 400 AH FLA.

That is why I suggested a USB L16 model. Less than Trojan with decent performance. Those can easily handle a 2 Kw Inverter if need be.

[Mike90250]

It's unlikely the panels will try to dump 52 amps at noon. There will be some ramp up. And compare the price ($100) of golf cart 6v - 200ah to the cheap L16 ($250). I don't expect the GC battery to last more than 2 years, but it will give a good baseline to plan a more balanced system from. Yugo or Toyota ?

[Szabie]

Ok thanks guys looks like I've ****ed this up right from the get go ...appreciate your advice that tin hat ranch can go and join the clintons as far as I'm concerned.. I'm totally over solar power

[AzRoute66]

Szabie, the answer to your question is 'yes'. I think the batteries you proposed will do the job.

I think you have gathered that these folk (and I) would love to have just a little bit more information, especially concerning the average consumption of the refrigerator and how much TV you watch, but since that information may not be readily available you will just have to live with MY assumptions.

I assume that your current batteries do, or did at some point, run your fridge, tv, and toaster adequately, which tells me you have enough solar panels to do the job. From this, assuming that you are getting no more than 5 full solar hours hitting them, you have been running under 6300 Wh/day.

For a 24V battery system to store that power you want 6300Wh / 24V = 262.5 Ah. As you proposed 24V @ 280Ah you should be good to go. Please note that I am now assuming that you are running lower than the full 6300Wh/day (as you mentioned no problem with cloudy days etc.)

You say this system is "in camp". If shading is a problem "in camp" your wiring those panels in parallel might be the best way to go, but if not you might get some more stored power if you do wire them in two strings of 3 panels in series (or three strings of two panels), this will probably change your fusing. Also, I like using 12V batteries because using 4 6V batteries is just more clutter and lifting 'in camp'.

I don't see any real problem with AGM batteries, and they have some 'in camp' advantages, but you might get off [quite a bit] cheaper and have longer longevity with flooded lead acid batteries.

The other way you might save some money is that based on a little experience with "in camp" appliances, this whole system may be significantly more than you need. Only by knowing more about the consumption, or trial and error in this case, could I say with confidence.

[max2k]

Szabie, the answer to your question is 'yes'. I think the batteries you proposed will do the job.

I think you have gathered that these folk (and I) would love to have just a little bit more information, especially concerning the average consumption of the refrigerator and how much TV you watch, but since that information may not be readily available you will just have to live with MY assumptions.

I assume that your current batteries do, or did at some point, run your fridge, tv, and toaster adequately, which tells me you have enough solar panels to do the job. From this, assuming that you are getting no more than 5 full solar hours hitting them, you have been running under 6300 Wh/day.

For a 24V battery system to store that power you want 6300Wh / 24V = 262.5 Ah. As you proposed 24V @ 280Ah you should be good to go. Please note that I am now assuming that you are running lower than the full 6300Wh/day (as you mentioned no problem with cloudy days etc.)

You say this system is "in camp". If shading is a problem "in camp" your wiring those panels in parallel might be the best way to go, but if not you might get some more stored power if you do wire them in two strings of 3 panels in series (or three strings of two panels), this will probably change your fusing. Also, I like using 12V batteries because using 4 6V batteries is just more clutter and lifting 'in camp'.

I don't see any real problem with AGM batteries, and they have some 'in camp' advantages, but you might get off [quite a bit] cheaper and have longer longevity with flooded lead acid batteries.

The other way you might save some money is that based on a little experience with "in camp" appliances, this whole system may be significantly more than you need. Only by knowing more about the consumption, or trial and error in this case, could I say with confidence.

not sure how much field experience you have with batteries and I openly admit I have 0 but reading this board led me to believe if you want your batteries last you shouldn't drain them more than 50% which requires double capacity from the get go for daily used system. AGM again from just reading this board simply drives costs up without providing much advantages in this application.

[AzRoute66]

Exactly right. We have no consumption data. I am assuming the depth of discharge will be fine. Why are you assuming it won't?

[max2k]

Exactly right. We have no consumption data. I am assuming the depth of discharge will be fine. Why are you assuming it won't?

your estimate was 262Ah and deep cycle FLA batteries should be discharged no more than 50% leading to requirement to have 500Ah battery if this cycle repeats daily. If it is discharged deeper number of cycles (its lifespan) drops very quickly, manufacturers publish correspondent charts. OTOH this is happening in a cabin, may be he needs to discharge it 10 times a year when he is there.

[AzRoute66]

My worst case was 262Ah. My assumed estimate is very much lower.