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2x 12v BB 100AH batteries

guidecca

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2x 12v BB 100AH batteries provides 100AH at 24v or does it provide 200AH at 24V?
 
Answer: 100 ah at 24v

When you connect batteries in series (positive to negative) the voltage goes up but the amp hour stays the same.

When you connect batteries in parallel (positive to positive) the voltage stays the same, but the amp hour goes up.

In either case, the actual energy capacity (measured in watt-hours) remains the same. In other words, either configuration would allow you to run a 100 watt load for the same period of time.
 
So to get more time add more batteries and wire them in parallel. I've got a Samlex EVO that cannot run an AC more than two hours. Now, it can't run the AC at all without alerting with a Battery Low Voltage alarm. Can I add a cheaper 12V battery to the bank?
 
Are your batteries wired for 12V (parallel) or 24V (series)? If parallel, then yes, you can add another 12V battery in parallel with the other two and you’ll gain whatever Ahr capacity it provides. You can‘t add another 12V in series with your 24V setup because then you’d have 36V and that will blow your inverter.
 
So to get more time add more batteries and wire them in parallel. I've got a Samlex EVO that cannot run an AC more than two hours. Now, it can't run the AC at all without alerting with a Battery Low Voltage alarm. Can I add a cheaper 12V battery to the bank?
Correct. To increase only the capacity (not the voltage) you would add more batteries in parallel.

Can you add a cheaper 12v battery? Yes, you "can" but whether or not you "should" is another question. Generally, the recommendation is to stick with batteries of approximately the same size, age and condition.

It sounds like the heavy load of air conditioning may have worn down your existing battery. When you turn on your air conditioning, a load is placed upon your battery. This load causes the voltage of the battery to decrease. The bigger the battery (higher capacity) the less effect the load will have on the battery voltage.

As your battery wears out, it essentially gets smaller (loses capacity). It sounds like what has happened is that the capacity of your battery may have dropped (as a result of being used) to the point where it is no longer large enough to support the load imposed by the air conditioner. Remember, when the load is applied, the voltage drops, and it drops more with a small battery than a large one. Now that your battery has less capacity, the voltage drops far enough to cause your inverter to object.

I do not believe that you will find ultimate success by adding a cheaper battery to the bank. It might work for awhile, but the bottom line is that an air conditioner is a large load that requires a large battery. I think you need a new battery, properly sized for the job you are asking it to do.
 
The two 12v 100aH batteries are wired in series and are about one year old. Not sure if they can withstand high temperature (90+ F) inside a van. Never had a problem with them before powering smaller loads but only have 400W of solar on the roof. People who are powering air conditioners are using 750W and higher banks of solar panels. Could I add two cheaper 12v batteries in series for 24v? Would that increase capacity? How do I test the two BB batteries for any damage? Do I do a capacity test on them?
 
The two Battle Borns should be able to dump 100A to the inverter for one hour. Now the question is how much load does the A/C impose on the inverter. If you have one, what does the SAMLEX control panel show for the AC load? A typical air conditioner is around 1000W, so at 24V with 90% efficiency that is ~ 47A from the batteries.

Another possibility is the two batteries are not charging properly. I remember reading something about BB where they recommend that series batteries be disconnected and charged separately once in a while.
 
Whether the batteries are in series or parallel ... you will have the same amount of power.

The voltage will increase when you have them in series ... and the AH will increase when you have them in parallel.... but the amount of power is the same.

If you are going to add batteries, you would have to add 2 more in parallel to keep the 24V your inverter requires.

2 100 AH batteries is not very much to run an air conditioner for very long.
You need to know how much power the air conditioner requires and size the batteries for how long you need to run the air conditioner.
You also need to have enough charge capacity to replenish the batteries.
 
Something like this?
 

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Correct. To increase only the capacity (not the voltage) you would add more batteries in parallel.

Can you add a cheaper 12v battery? Yes, you "can" but whether or not you "should" is another question. Generally, the recommendation is to stick with batteries of approximately the same size, age and condition.

It sounds like the heavy load of air conditioning may have worn down your existing battery. When you turn on your air conditioning, a load is placed upon your battery. This load causes the voltage of the battery to decrease. The bigger the battery (higher capacity) the less effect the load will have on the battery voltage.

As your battery wears out, it essentially gets smaller (loses capacity). It sounds like what has happened is that the capacity of your battery may have dropped (as a result of being used) to the point where it is no longer large enough to support the load imposed by the air conditioner. Remember, when the load is applied, the voltage drops, and it drops more with a small battery than a large one. Now that your battery has less capacity, the voltage drops far enough to cause your inverter to object.

I do not believe that you will find ultimate success by adding a cheaper battery to the bank. It might work for awhile, but the bottom line is that an air conditioner is a large load that requires a large battery. I think you need a new battery, properly sized for the job you are asking it to do.
I will charge the two BB batteries separately and then do a capacity test on each one to see if there is a problem. I will let you know if I find a problem.
 
I didn't realize you had Battleborn batteries. That is a very good idea to do a capacity test on each battery. Those batteries should be good for many cycles. What is the current draw of your air conditioner? How have you been charging your batteries?
 
I think the portable air condition draws 7.5 Amps @ 120 VAC = 900 Watts =~ 45A (after efficiency etc). The batteries are connected to a Samlex EVO 2224, 24v inverter-charger connected to the grid and it is in charging mode. So, the batteries should be charged.
 
900 watts is 75 amps at 12 volts. Each of your Battleborns is rated for 100 amps continuous, 200 amps for two batteries in parallel. Voltage should not be sagging enough to alarm your inverter with just a 900 watt load. The batteries you have should be adequate to run the AC for at least a couple of hours. It will be interesting to see what your capacity tests show. It would also be a good idea to check all of your connections to make sure they are all clean and tight. You can also place your hand on each connection while the AC is on. If a connection feels warm or hot that is an indication that the connection is not good. What gauge wire connects your inverter to your batteries, and how long are those wires? Is your charger set for charging LiFePO batteries?
 
So .... If you keep with the universal language of watts .... 2 battleborn batteries would have 2600 WH of power if you use 13V as the average voltage. That would be if you use a full 100% of the capacity.

If you figure using 80% of capacity to be safe ... that would be 2080 WH .... and that would equal about 2.3 hours of powering the air conditioner at the full rating.
 
You guys are smart! That is some good information. I will check the system for heat, loose connections, etc. One symptom I'm getting that I noticed was not there before I tried using the air conditioner is the numbers in the Bayite meter attached to a shunt to measure volts, amps, power, and energy fluctuate up and down abnormally. Using 1/0 gage wire about 3'-4' in length. Configuration on the SCC was set for lithium. My SCC is attached to the inverter-charger which controls charging. A Samlex tech sent the attached configuration settings today.
 

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