Battery configuration for 400 watt system

[Higgo11]

For 400 watt system, 40 amp controller, 12V 100ah, can I use 4 AGM batteries instead of 3 and should they be in series or parallel?

 

[TexasViking]

An answer would depend on the voltage that your inverter can accept and what your battery storage needs are (i.e. kWh usage and hours\days of autonomy required.)

 

[DASH]

Also depend on the watts/volts your solar panels will deliver to the controller, what voltage the controller can deliver to the batteries, and if the Controller can handle the watts/volts delivered from the solar panels.

 

[Higgo11]

An answer would depend on the voltage that your inverter can accept and what your battery storage needs are (i.e. kWh usage and hours\days of autonomy required.)

Inverter is AIMS 1500 watt (3000 peak) and usage is 400 watts / day for water softener and filtration system as well as the occasional power saw for 2 minutes per day. 4 - 100 watt panels.

 

[Higgo11]

Also depend on the watts/volts your solar panels will deliver to the controller, what voltage the controller can deliver to the batteries, and if the Controller can handle the watts/volts delivered from the solar panels.

4 - 100 watt panels and epever mppt controller 40A 12v/24v

 

[snoobler]

For 400 watt system, 40 amp controller, 12V 100ah, can I use 4 AGM batteries instead of 3 and should they be in series or parallel?

Technically, you can use however many AGM batteries you want. If you want a 12V system, you need to have them in parallel. If you put them in series, their voltages add, and you don't have a 12V system anymore.

Did you mean usage of 400Wh per day? If so, that's not much for the battery capacity you have. Furthermore, your inverter likely draws somewhere around 7-12W, so your inverter might be increasing your expected load by 50%.

Are you sure your power saw won't overload the inverter? The SURGE current of a power saw is likely 5-6 times higher than its run current. You shouldn't count on the overload rating of an inverter as that may only mean it will hold that surge for 10 milliseconds.

Your 400W panels should be fine for 3-4 100Ah AGM batteries.

 

[Higgo11]

Technically, you can use however many AGM batteries you want. If you want a 12V system, you need to have them in parallel. If you put them in series, their voltages add, and you don't have a 12V system anymore.

Did you mean usage of 400Wh per day? If so, that's not much for the battery capacity you have. Furthermore, your inverter likely draws somewhere around 7-12W, so your inverter might be increasing your expected load by 50%.

Are you sure your power saw won't overload the inverter? The SURGE current of a power saw is likely 5-6 times higher than its run current. You shouldn't count on the overload rating of an inverter as that may only mean it will hold that surge for 10 milliseconds.

Your 400W panels should be fine for 3-4 100Ah AGM batteries.

Many thanks! Really appreciate the information. I will look into the potential saw issue.

 

[DASH]

4 - 100 watt panels and epever mppt controller 40A 12v/24v

With that equipment, You can have Your battery bank setup as 12 volts or 24 volts. There's Pro's/Con's to use either system.

 

[Zil]

At 400 watts, I would stay with 12 volts. If you need to upgrade the inverter to handle the saw, over 2000W inverter, start thinking about 24 volts and more panels.

 

[Philo DuFresne]

At 400 watts, I would stay with 12 volts. If you need to upgrade the inverter to handle the saw, over 2000W inverter, start thinking about 24 volts and more panels.

Is there a reason you wouldn't go 24v? I purchased a renogy 400w solar kit, and plan on pairing it with a 2000w 24v inverter and 2x 12v 100ah lifepo4. Will i have issues, or is it just not necessary?

 

[MisterSandals]

Is there a reason you wouldn't go 24v?

If your only use is a 24v inverter then that sounds like the way to go.
Usually folks upgrade from 12v batteries to 24v batteries when the amps start to get unmanageable with wiring and fuses. 2000w @ 12v = 166.6amps. Thats a thick wire and a big fuse.
With a 24v system, that becomes a more manageable 83.3a.

If you are putting this in an RV with 12v lights, pumps... then you need to get a buck converter to go from 24v to 12v for those items (not awful but its an extra thing to buy and wire into your system).

The rule of thumb here is usually 12v up to 3000w then you really need to go 24v or even 48v.
There is no problem having a 24v battery, especially if you already own a nice expensive 24v 2000w inverter!

 

[Philo DuFresne]

If your only use is a 24v inverter then that sounds like the way to go.
Usually folks upgrade from 12v batteries to 24v batteries when the amps start to get unmanageable with wiring and fuses. 2000w @ 12v = 166.6amps. Thats a thick wire and a big fuse.
With a 24v system, that becomes a more manageable 83.3a.

If you are putting this in an RV with 12v lights, pumps... then you need to get a buck converter to go from 24v to 12v for those items (not awful but its an extra thing to buy and wire into your system).

The rule of thumb here is usually 12v up to 3000w then you really need to go 24v or even 48v.
There is no problem having a 24v battery, especially if you already own a nice expensive 24v 2000w inverter!

Thank you! I do have the 2000w 24v inverter, and will series the batteries into 24v, so i wanted to make sure it was just unnecessary, not improper. I'd like to expand at some point, and wanted to keep wire gauge down inside the step van. I really appreciate the information!

 

[Philo DuFresne]

@MisterSandals Can I ask this; if I have 2 12v 100ah LiFePo4 batteries in series, will that come out as 24v 100ah or 2400watt hours, or something different?

 

[MisterSandals]

@MisterSandals Can I ask this; if I have 2 12v 100ah LiFePo4 batteries in series, will that come out as 24v 100ah or 2400watt hours, or something different?

The watt hours will never change no matter how you wire them.
2 x 12v x 100ah = 2400wh
24v x 100ah = 2400wh

 

[Philo DuFresne]

The watt hours will never change no matter how you wire them.
2 x 12v x 100ah = 2400wh
24v x 100ah = 2400wh

I was of that mind, but something got me tripped up, thank you for setting me right. I just got Wills book on rv/van solar today, and it has been elucidating. Thank you again.