Battery 6 or 8 v

junglejoe39

Noticed Sams has 6 and 8 volt batteries. The 6 volt are cheaper per ah but I dont want to miss something either. Any chance the 8 volt might be better because of 1 less battery and 1 less link cable to = a 24v bank ?

Vic

Hi ..joe..,

Personally,  like to run the lowest battery voltage possible.   This way,  if one cell happens to tank,  you will be throwing out fewer good cells.

Also,  seems to me,  that 8 V batteries are not that common.

Could you get the AH Capacity that you need,  if you used 8 V batteries?

Opinions,   FWIW,   Vic

junglejoe39

That,s a good point about the bad cell thing and about uncommon. I usually check the benefits of all options.

junglejoe39

Im a little bit crazy. I think Im going 8 volt x 3 = 1 less cable and it fits my schedule

vtmaps

junglejoe39 said:

That,s a good point about the bad cell thing and about uncommon. I usually check the benefits of all options.

About 'uncommon'.... uncommon may mean it's been sitting on the shelf awhile... make sure you know how to read the date code on the battery BEFORE you get to the store.  You should also realize that there may be a sticker with a month and year marked with a date for the warranty, but that sticker is NOT the manufacturers date code. 

About 'the bad cell thing'.... Vic makes a very good point about the bad cell.  Having 2 volt batteries in a 24 volt system means 11 interconnects which, as you realize, are potential points of failure.  But having those connections opens up a world of possibility for monitoring and diagnosing with a volt meter.   I have 6 volt batteries in my 24 volt system and I really wish there was an easy way to know the voltage of the individual cells... it can be done, but it involves sticking an electrode into the electrolyte of the cell.  By the way, having less-than-perfect connections (which may occur over time) is a disaster in a battery bank with parallel strings.  It's not such a problem, and it's very easy to diagnose, in a single string battery bank.

If you have a cell fail shortly after purchase, presumably the warranty will replace the whole battery, so it doesn't matter what voltage battery you use.  When your battery bank with multi-cell batteries is old, when one cell fails you will probably replace the whole bank... if you replace one multi-cell battery (1/4 or 1/3 of your bank) it will rapidly age to match the rest of the bank.   When you have 12 single cell batteries, you have the option to replace just 1/12 of the bank. 

If my bank was 5 years old and I thought I could get another 2 years out of the bank by replacing 1/3 of the bank, I would not do so.  I would replace 1/12 of my bank to gain another 2 years on the other 11/12 of the bank.

--vtMaps

Photowhit

Look at your choices as building a system and know what you want to do with the system.

I think you said you had 1500 watts of panels? 3 - 8 volt batteries would be roughly 140Ah at 24 volts storage. This might be a little small normally for a 1500 watt array, but if you are home and hope to be using energy when available it might be fine.

It does give you less storage for over night use, the typical setup uses more energy from storage, but it makes sense to use energy when sun is hitting your panels. You only get 75-80% return of energy stored. Particularly if you have the grid and are not connecting the 2 systems.

westbranch

Regardless of manuf. date, If the store says they will do a boost charge, you really want to see what the pre-charge and SG on each cell is, and same after charge...  if they are down to start and low SG as for another set