Help: Lots of A/C and not enough panels/batteries?

Re: Help: Lots of A/C and not enough panels/batteries?

Koj,

Here is a nice web page that explains how to wire batteries in parallel for proper current sharing (probably already have posted in your thread--but it does not hurt to be a bit repetitive).

Smart Gauge Battery Wiring

And here is a nice write up on series/parallel connections of batteries:

Deltran Battery Charger Company series/parallel tutorial (PDF).

Hmmm.... Trying to increase the capacity of an existing battery bank. Always a tough call on how to do it "right".

Ignoring all of the suggestions that we keep repeating--Don't simply add mixed age/types/models of batteries into an existing battery bank... :roll:

Remember that batteries are chemical animals and the chemistry that produces the voltage is very "exact" and related to temperature, stuff added to the lead plates, and acid strength.

When you add batteries in parallel, ideally you want them to share the current load equally. That means "identical strings" of batteries in parallel (same brand/model/size/date code). The farther you deviate from this "ideal"--the less well the batteries will share the loads.

So the first choice is to build the correct size battery bank with all new batteries (that ship has sailed).

So--The "ideal" second choice would be to simply purchase 24x new 2V, 500 AH cells and connect them in series, then connect the second string to the first string per the above web page and with an additional fuse/breaker (for safety).

That will give you a 48 volt 100AH battery bank. It will be "oversized" for your needs a bit--but assuming you have enough charging current for 5-13% of the 1000AH bank capacity--you will be fine.

If you need 700 AH (money, other reasons), then 24x 2V, 200 AH or 48x 2V, 100 AH (two parallel strings of 100 AH batteries) are other options.

If you do use smaller batteries--Ideally you still would want the same brand and type of battery (i.e., flooded cell, same plate configuration/chemistry, --for example, don't mix deep cycle AGM for one string and flooded cell starting batteries in the parallel string). In theory, the smaller string should share the current in proportion to their capacity (ie., 500AH/700AH for one series string and 200AH/700AH for the second string). You would need some sort of shunt or DC Clamp Amp Meter to ensure the strings are sharing current/loads correctly.

Can it be done--probably. It will work well for you, maybe. Is there any guarantee you will have a long and happy life with the mixed battery bank--I cannot say.

-Bill