How much battery power do I have?

[dom88]

Hi

I live in Spain, running a solar system backed up by a generator, completely off the grid. I'm learning fast about my set up which was inherited when I moved in.

It seems to me that the obvious area that my system is lacking is in sufficient power battery storage. Since the sun shines nearly every day and I have 10 solar panels (not sure of their power capabality, but they are appx 1m x 0.5m each).

However, in trying to work out how to upgrade my battery bank, I need to know what it is I have already. There are no markings on them except they are made by BAE systems. There are 12 x 2v batteries.

Is there a method of calculating how many Amp hours this gives me? Maybe by simply measuring the size of them? They run off distilled water.

Any advice would be hugely appreciated.

Regards

Dominic

[DanG]

Hola Dominic!

First task before you is to familiarize yourself with what you already have!

You need to inspect the items in the system - getting manufactuors names and part numbers, serial numbers and date codes and just share the general information here for recommendations. To keep it safe as possible and for your own background information you need to draw out an "as found" schematic diagram so you can track any changes made!

Please post back with more data on specifics!

[DanG]

The BAE systems battery may be old NATA surplus, BAE is surrently building light armored vehicles and weapon systems and are partnets with everyone from SAAB to Airbus!

Providing a picture and dimensions may help someone recognize it, if it is a re-labeled product.

[dom88]

Hi

Unfortunately there is simply no markings on the batteries whatsoever, except the BAE systems on the caps where the water is added. They are solid black in colour, approximately 40cm x 10cm x 15cm.

[Flux]

With no identification you will never know their original capacity.

You could measure them now and find out what you have, but you will have no idea how they compared to original state.

From dimensions I would guess 100AH as Plante but may be a fair bit higher with shorter life technology.

It may not be a good idea to add others in parallel with a bank of unknown parentage.

As they seem to be flooded cells you can use a hydrometer to see how much a known discharge takes them down.

Flux

[dom88]

Thanks very much for the help.

I think i might need to replace them nonetheless, everywhere i look i read that the better the batteries the more efficient the system.

[alancorey]

If you think it's possible that they might have been left partially discharged for a long time, you could look into trying to restore some capacity by using a desulphator.  See http://www.flex.com/~kalepa/desulf.htm for some plans and kits.

If these are connected as one 24 volt bank you should be able to connect another 24 volt bank, you just don't want to mix parts of the two banks.  Connecting one then the other should work, or maybe putting the banks in parallel.  You could connect a new bank and keep this around as a backup, just charging it once in a while.

I've seen it stated somewhere that the single largest cause of inefficiency in battery systems like this is not having enough storage capacity: the sun's shining and your batteries are fully charged, so there's nothing useful to do with the excess power.  On the other hand you don't want to pull batteries down below about 80% charge or sulphation (or worse) sets in, so it's good to keep them charged.  There's a tradeoff and you need to look at numbers to balance capacity, generation capability and power usage, plus allow for cloudy days.  You should be able to get a sense of the amp-hour/watt-hour capacity you've got now by getting them fully charged according to a hydrometer, then discharge them at a known rate to about 80%, recording hydrometer readings and time until you reach the specific gravity for the 80% point.  If they won't charge with much current or supply much current, they sound like a good candidate for desulphation.

Then again, the only solar system I've got working is a silly solar light I found in the dump and fixed, but I read a bunch.

  Alan

[nothing to lose]

I would say the first thing is to find out what you have for solar pannels.

I have seen 35 watt and 55 watt about the same size pannels with different designs. WidthX length probably is not a good way to guess at them. 10X35watt=350watts or 10x55watt=550watts, big difference in how much power your getting. Same basic length and width.

Since the system is already there now does not mean it was correct when built either.

I would start by trying to figure out how much power is made. To to find out what the pannels are etc..

In the first post,

"It seems to me that the obvious area that my system is lacking is in sufficient power battery storage. Since the sun shines nearly every day and I have 10 solar panels (not sure of their power capabality, but they are appx 1m x 0.5m each). "

Ok as I mentioned above, need to know how much power is being made to know how much is available to store in the first place.

 I did not see a mention of how much power you use either.

Of course if you use 100amps and the pannels only produce 90amps, you have a problem of not enough power being made. Upgrading the batteries here will not help though because you would be using more than is made and would still have the same problem.

It is better to not mix new and old batteries, so if you upgrade your battery bank it's best to start with all new matching batteries. If you do this, then what you have now does not matter anyway, it still falls back onto how much power the pannels make and how much you use.

Testing the capacity like others have mentioned already is good and you should do that also. I just did not see your reason posted for WHY you think the batteries are the problem really.

In other words just because it's a bright sunny day and you have alot of pannels does not mean you are making as much power as being used. You need to measure your useage also.

[bob golding]

hi, cant add much but bae systems took over hawker batteries some time ago. i had some of thier gell cell  batteries but got nowhere  with getting any specs. best guess is to go by size and hydrometer readings. there is plenty of basic battery info on the web. try one of the desulfator sites. good luck.

bob golding

[dom88]

Thanks for all the comments. It's a steep learning curve trying to manage all this!

The reason for the post in the first place was nothing more than "gut feeling", I check the batteries as often as I can and they are always nearly full.

I do not have a measure of how much we use, but will see what i can put into place. It's not so much, water pump, dishwahser, washing machine, tvs, internet etc...all low usage. HOwever, we do have an electric oven and electric central heating (don't ask me why the person i bought the house from thought it was sensible to have electric central heating in a house with no electricity mains!). Everything listed above will run without need for generator back up so long as the sun is shining and we don't run them all simultaneously. We need the generator for an hour or so every evening to top up the batteries so long as we don't use the oven.

anyway, I think the most sensible approach is to stop wasting everyone's time with my waffling and go get some facts...

thanks for all the tips for now!