Battery Pack Health?

have you googled battery charge management devices? There are ICs out there made just for this sort of thing.

been there, and of course wll you find is for Lioon packs, and such..

this is old skool,,

Flooded lead acid batteries.

NSS if you must have on the fly measurements look at Midtronics instruments. So far these are the only kind I have found that will come close to accurate indication.

As you have already been told, specific gravity is the most reliable way to determine state of health; but only when battery is fully charged. The Advantage of the Midtronic testers is they can determnine a good but depleted battery from a badly sulfted unit having nearly full voltage indication. Its a capacitance type measurement.

So you have quantity 8 6V batteries. Why? Is this a 12V, 24V or 48V system.

If you are running a 48V system then all batteries are in series. Sometimes you can get away with replacing the one bad cell if the rest are still good. The reason being in a series string the charging current goes through ALL the cells and it has the effect of keeping all the cell charging closer to each other.

BUT if you pair up a new and an old set of cells in parallel then you create problems due to diferrence in internal resistance.

Yes it is a 48 volt system.

NSS You have received a number of suggestions regarding how to determine battery pack health. If this is in fact an off grid or UPS installation there are a few differences compared to a mobile vehicular installation. You also have a few special issues related to such an installation. Wind and solar charging sources tend to be of the lower current variety. And battery capacity typically in the high amp hour capacities. You end up with a C/10 charge rate or worse. When a stationary battery pack is only charged with relatively low charge current levels the liquid electrolyte tends to stratify. In other words the electrolyte has stronger specific gravity in the botom of the jars and the upper levels tend to have less specific gravity. Submarine batteries had a special air bubbling system installed specifically to mix up the liquid level. Unless you have the special UPS type batteries this option is not available to you. Depending on what inverter system you use the equipment may include a battery monitor. It will read out the accumulated amp hours or kilowatt hours used. If the meter was properly calibrated when first installed it should indicate how much energy remains. Provided you have a decent source of charging current available that is capable of delivering at least 15% - 25% of the amp -hour capacity the best way to rejuvenate your pack is to cycle the battery down completely, then hit it with the full charge and cycle the pack back up. Continue the charging through all stages to finish float. As Andy stated in his post, it it also extremely important that you have proper charging equipment available. The charger must be temperature compensated. Sulfation is the natural consequence of discharging lead / sulphuric acis batteries. You must complete the charge right through to float stage in order to remove the acumulated lead sulfate. Failing to do so will cause premature cell failure. I have noticed a greater incidence of premature cell failure in cells located in the middle or towards the positive end of the pack. Unfortunately I have unsufficient data to form a statistically sound conclusion. I do use desulfators on my own battery pack and recommend it to all my clients. Good luck

With regards to health of battery, the only really reliable test of a battery is the specific gravity of the electrolyte. Another important issue is monitoring the temperature of the batteries while being charged- if they get too hot, you most likely have a faulty cell (assuming you are charging at an appropriate rate). Significant difference between temperatures of different batteries in the same bank while charging also indicates a possible failing cell.

Never replace just one battery in a bank- replace them all at the same time, when one fails. The problem is, the difference in capacity with aging can cause additional damage to the remaining cells.

To keep such batteries in a good condition, you need a high quality charger that NEVER over or under charges. The charger must be designed for the Lead Acid battery type and it must also regulate charging according to temperature of the battery.

Please define battery lead acid technology type:-

Car/starting battery, Leisure/deep cycle?

Read the following link through will also help:-

Lead acid batteryies

The best test is to measure each battery in turn with a voltmeter while connected together- with the charging method disconnected- so with vm across each + & -, the voltage will show if a cell is faulty. SG measurements can be ok but if cell has internal disintergration , will not be able to output amps- so hi load test is needed of each battery. The best test of a new battery is a meter that measures internal resistance- this is noted then subsequent tests will reveal the deterioration- this gives a very accurate indication. The best way to measure the actual amp hour capacity is to note the initial performance of the original pack- down to safe still voltage x time x load- then repeat periodically- this will be far more accurate than any averaged/assumed test!. Any battery/cell will last longer if lightly used- extremes will kill quickly- ideally correct charge/rate vs correct discharge/rate with correct maintenance of cell/battery/ies.

I have been blessed with a high priority vehicle that has 4, 12 volt batteries connected in parallel. The van was equipped with a "Batstat P-200" made by Batcon. They claim to load test each battery separately every time the truck is started. In 8 years, it has been very good. Your results of corse may vary. They can be reached at www.batconinc.com

Good luck.

Hi NSS,

I've given GAs to both elnav and cjw. One thing to add. to test for a dud pack, and this is infallible, put the bank on high current, either charge or discharge and measure the voltages aross each 6V block. You will find a faulty battery will be inconsistant with it's bank mates. A difference of 1V would be adequate to indicate that the unit is duff but of course you must replace the whole bank.

Regards

Chas

Twice a year I take all my batterys one at a time and charge them for 2 days using one of those rechargable battery packs. My grandad called this a deep charge. I have some batterys that are 9 years old or more.

I run one battery on a Massey tractor that has no generator or alternator to charge it. The battery never fails to start the desiel engine and it had been there over 9 years.