Wiring batteries 2volt to 24volt

[Sapphireminer]

Thanks for all the info more for me to look into. Dave

[Yet another Yeti]

The controller is 100 volts so I guess that would be 2 sets of 2 44v panels in series then connected in parallel to give 88volts . Thanks Dave

MOD Note. the following is guessing by the poster, and not to be taken as truth for your panels. You should
make note of the specs on the sticker on your panels, and what the values are:
Voc ___
Vmp___
Isc___
Imp___


The 44 Volts you mention , likely is Uopencircuit Uoc ,
not the Umaximumpowerpoint Umpp .

Sounds like early 72cell panels .

But that Uoc is the important one to get maximum allowed panels per string ,
and the Umpp is the important one to feed the battery .

48 V battery will need a range of 54 to 60 Volts to be feeded ,
and if the Umpp would be at 30 Volts , two in series would feed
a 48 V battery .


For a 24V setup , one panel per string would suffice to feed that battery
if Umpp at 26 to 30 Volts .

Tempetature coefficient needs to be included in Uoc math !

[ButchDeal]

Wow!

That's news to me.

I thought most charge had a max VOC input rating.

Most that I have looked at are between 100-150volts.

Ok we seem to be cross talking here the amps is rated on the output voltage. Yes they do have a max input voltage as well, but the max amperage is with the output voltage. This it handles more inout wattage at higher voltage on the out put ( battery ) side.

[PNW_Steve]

Charge controllers are rated on the output voltage not the input voltage. So to get higher voltage string the pv modules together in series ( increases voltage)
larger battery voltage allows the charge controller to handle more solar wattage.

Wow!

That's news to me.

I thought most charge had a max VOC input rating.

Most that I have looked at are between 100-150volts.

[Sapphireminer]

The controller is 100 volts so I guess that would be 2 sets of 2 44v panels in series then connected in parallel to give 88volts . Thanks Dave

[ButchDeal]

Hi ButchDeal the MPPT is 60amp 12v to 48v

Charge controllers are rated on the output voltage not the input voltage. So to get higher voltage string the pv modules together in series ( increases voltage)
larger battery voltage allows the charge controller to handle more solar wattage.

[Sapphireminer]

Hi ButchDeal the MPPT is 60amp 12v to 48v Hi MichaelK my biggest concern is total battery failure meaning end of life or worn out the cost in Australia to replace the batteries in a 48 volt system is in the 18,000 to 20,000 dollar range as against 8,000 to 10,000 on a 24 volt system that is the biggest consideration for me thanks everyone Dave

[MichaelK!]

48V is still a better option. You'll still have two parallel strings at 48V, which will be better to manage than four 24V strings. As Inetdog mentions, of you have one single battery failure, you can simply remove one battery from the string and adjust the voltage. As the voltage increases, this hecomes less problematic. Besides, if you need to remove 1 single failed battery, you'll need to remove three good batteries from the other strings, to balance things out. At 48 volts, this would be only one more battery.

[ButchDeal]

Hi I already have 28 190w solar panels there output is 44volts can this be boosted to run the 48volt system or is a total upgrade needed thanks Dave

Yes put them in strings of 3 or 4 and then parallel the strings and connect to MPPT charge controller
The number in series will depend in the charge controllers input voltage range.

[ButchDeal]

As far as I can tell the OP is talking about two strings. Is there any advantage of putting sets of two in parallel?.

OP has 48 batteries at 2v and wants a 24v bank so he is talking about four strings not two in parallel

[Ampster]

And for wiring of two or more parallel batteries or stacks of batteries, see http://www.smartgauge.co.uk/batt_con.
You generally do want to charge through the same set of terminals that you discharge, just not the same position on both halves of a parallel set instead of diagonal wiring.

As far as I can tell the OP is talking about two strings. Is there any advantage of putting sets of two in parallel?. This is commonly done with Lithium but I am unfamiliar with the issues around Lead Acid. The above link suggests this is possible as long as the interconnections are of similar resistance.

[Sapphireminer]

Hi I already have 28 190w solar panels there output is 44volts can this be boosted to run the 48volt system or is a total upgrade needed thanks Dave

[Sapphireminer]

Thanks for the info inetdog . Dave

[inetdog]

Hi thanks for the replies the reason for me to go 24v is the batteries are used if I have a failure I can still use 24v just at a lower amps if I had a total failure I would have a better chance of replacing 24volts of batteries Than a 48v set hope this makes sense . Regards Dave

It is most likely that a single 2V cell will fail rather than a set of 12 independent batteries. By simply cutting the failed cell/battery out of the series string and adjusting the charger set points down appropriately you would be able to continue near full power operation with 23 batteries instead of 24.
Replacing just one 24V string from a parallel set is definitely not a good idea since it can lead to premature failure of the "good" string.
Replacing one cell in a series string with a new unit will have less of a downside, since you will get the full remaining life out of the older batteries.

[Sapphireminer]

Hi thanks for the replies the reason for me to go 24v is the batteries are used if I have a failure I can still use 24v just at a lower amps if I had a total failure I would have a better chance of replacing 24volts of batteries Than a 48v set hope this makes sense . Regards Dave