New Batteries and Old Battery Banks

IMHO... Seems that you have had a pretty good run with your existing batteries and that they might need retirement (recycling) sometime in the near future. Mixing old and new batteries will almost always lead to problems. After 9+ years, advances in battery construction and chemistry may make the old/new gap even wider that you expect. I highly recommend a whole new bank when the time comes.

The "Some" are correct.

Dear Skywalker

9 years is an extremely good life for battery. Speaks volume of how well you have maintained it. To further check on the life of battery, check the time backup available from fully charged state. If backup time is significantly lower than what you use to get earlier, then it is a clear sympton that battery is coming to end of life. One option to extend the life further is to change the electrolyte in battery & do a very very slow charging ( approx. 2-3% rate ), followed by discharging again charging & discharging, then charging and then putting it back into the system.

Once again, I repeat, it is your passion due to which you have extracted this much life from battery for this application.

For info., at one of our customer's substation, they got 19 years from a tubular lead acid battery & it was still going alright before they decided to change, just in case it fails and causes catostrophic problems in their plant. But this application is completely different from solar application where battery is repeatedly discharged and charged, every day.

Thanks and regards

Ashok Toshniwal, Bangalore, India

Lead -acid batteries looses capacity due to acid stratification. Sometime with Overcharging ( Bubbling of electrolyte) ,this can be taken care off. Another option you can try is to shake up the electrolyte by turning sideways ( without spillage) 2/3 times. If you can plug the hole 100%,then 180 degree turning is best. You may see that ,you are getting higher capacity.

You can also try some battery chemicals available,which takes care of hard sulphation of plates and give better result for some time.

New battery must not be mixed with old batteries.

For long life, 14.4 volts is simply too high for charging. Over the long term (more than 2 years), it damages the battery. Thats why cars need regular replacements of their batteries....but it does get 100% charge into the batteries for the shorter life span....

I was unable to find the Interstate L 16 HD on the Interstate web site, so I have no idea if these are leisure, SLA, GEL or car batteries or what.

I would buy an electronic activator for each battery and see if that helps, but it may be too late, it sounds as though a single cell is shorted out.....the money is well spent as you can use them on the new batteries as well from day 1.....

A battery specialist can clean them out and refill/recharge/readjust the acids to get a few more years of life.....but only if you do it yourself (dangerous) is it financially sound......I learnt it all years ago, but would still probably not do it!!

Buy leisure type batteries the next time if the activators do not recover the old batteries. Use the activators on the new batteries from new.....

By the way, I do NOT mean chemical additions to the batteries, I am talking about small electronic circuits that pulse the battery......never ever add chemicals to a battery, no matter what the ads say!!!

Never gas with charging and never let car type batteries go for long under 12.6 volts. Even leisure batteries will last longer if you follow this rule...

SLA may not gas externally, but overcharging still damages them......

I keep my caravan battery between 12.6 and 13.4 volts only. It has had a small amount of water added once in 7 years.....the need to add water more often is an indication of overcharging/gassing.

Charging only to 13.4 volts means only about 70% capacity, do not forget this!!

I build my own chargers as I have not found anything that will charge exactly as I want.....but keeping between 12.6 and 13.4 volts also means no temperature compensation is needed, which simplifies the design considerably.....

Thanks Andy for the details. The L16s were commonly used in the NW US rail industry for rail switching. The L16 is lead acid, 135 pounds of lead per each six volt battery. The HD denotes heavy duty. L is the size, once auto battery sizes leave the numeric coding (such as Group 24, 27, 31, etc., the next size coding used letters). The paperwork with the L16s indicated over charging to 14.4 once every 60 days, if the battery had been down to 10.8 a number of times. Fortunately, the controller and inverter have a smart brain (smarter than mine) in them that when set correctly per specs, take care of equalizing (over charging) for me. So I did keep to manuf spec recs at the 14.4v. I have heard of the elec activators, and I will certainly be searching the web for info/data on these, thanks for the good rec. I'll be skipping the refurbishment ideas from both you and Ashok, as it seems that won't get me another 9 years, new batts with activators possibly will allow more than 9 years on next round. Thanks all.

Due you mix new and old batteries in a flashlight same principle.