Charging voltages lead acid deep cycle vs starting

Re: Charging voltages lead acid deep cycle vs starting

myself and crewzer both had those batteries before. i used a morningstar sunsaver on those batteries, but not for the first year or 2 as i had no controller at all. those batteries didn't last long for me as it took me awhile before i realized that even though i had low current levels going into a large bank of those batteries, my batteries were still overcharging without something to control the voltages. the sunsaver failed due to a rare failure on a 120vac charger and i eventually got an sb50 just as those batteries croaked. now your manual should say the general settings the factory puts on it for charging a standard lead acid battery, but just in case it doesn't say my sb50 manual says acceptance kicks in when 14.3v is hit and then when the current falls back to 1 or 2amps it will kick down to 13.3v and output .1-.2amps for the float charge. these settings seem ok, but you probably could bump up the acceptance point to a higher point like 14.4v without problems. i don't know what crewzer had his charging at and he could chime in with what he did. with mine it was a hard lesson to learn as it is a myth that just because the current is low that you can get away with being without a controller. in retrospect, i suppose it is possible when the current is about 1/500 or 1/1000 of the ah capacity of the battery or an even lower fraction, but then it won't charge well either so controllers are needed. those batteries did not like the higher voltage on them when they were already full and it boiled out the water quickly and more often than it should have. my wally world batteries died of sulphation. do not let the water levels fall to the plates, ever, as sulphation will start immediately and those desulphators will not do anything for that condition that i've ever seen or heard of. of course you will have to add water to them at some point and make sure it is distilled.

Re: Charging voltages lead acid deep cycle vs starting

Are you sure the ECM is regulating the power? I was unaware of any car company using the ECM to regulate the alternator before OBD2 came out in the mid 90s. GM only started doing it in the new designs that came out after 2000, don't know about Dodge. Before then, the voltage regulator was built internal to the alternator, which started at some point in the 70s. I do know that an alternator with an oversized supply line to the battery will not really show any load change when accessories are switched on as the built-in regulator responds almost instantly. I had a 96 Tahoe with a 105 amp alternator, which I rewired all the primary voltage wiring with welding cable (2ga to the starter, 4ga from the alt to the battery and the battery to the main electrical center), and after that the voltmeter would not so much as twitch even when I intentionally turned on the AC at full blast and the headlights on brights (also had the headlights required so all 4 came on at once, all were powered by individual 12ga wire directly off the battery). The regulators in the alternators are very simple and quick to react.

Re: Charging voltages lead acid deep cycle vs starting

that would mean that one or more of the batteries is at a different soc or state of charge. if you have a dvm or dmm you should measure the voltages on the batteries seperately(disconnected from one another), but in any case seperate them and charge them individually rather than doing an eq charge. this is a better way for you to equalize the batteries without pushing the charged ones overboard. one cause for this may be resistance variations in the interconnecting wires or connectors. use of heavy wire on battery interconnections is highly recommended. it is also recommended to not use the same battery for both + and - charge input connections, but have the + going to say the battery on the left and the - connecting to the battery on the right. this helps to eq the charge between all of the batteries. the load connections should be the opposite with the + connection going to the battery on the right and the - connection going to the battery on the left. about once a year it is a good idea to shift the battery positions either staying all left moves or all right moves, but do not mix those moves. one battery will windup transposing to the other side.

Re: Charging voltages lead acid deep cycle vs starting

i'm not totally following or picturing this. it would seem to me that a heavy load on the batteries and or charger will bring the voltage downward. many chargers for auto and marine are not regulated though and when no loads are on the charger (including the batteries) it will show the voltage around 17v to 18v. placing a small load such as a small charge current for the batteries and it may very well show around 15v or 16v depending on the state of charge and the current supplied. now when putting a heavy external load to the batteries with charger going to it should show the voltage dropping and could go under 12v depending on the soc of the battery and the severity of the load even on a fully charged battery. please disconnect the charger, but leave the charger on and measure the open circuit voltage of the charger. you should not be getting voltages that high to your batteries if it is in fact getting to your batteries. i am going to try and reread your posts to see if i can grasp it better.

Re: Charging voltages lead acid deep cycle vs starting

without any unforeseen things due to missunderstanding of the circumstances i may venture to say the charger could be defective because of it showing that high of a voltage that it should not be showing being a regulated charger. read your manual on it to be sure it's not to show high voltages and i did try searching for info on your charger, but i didn't have any luck. i wish i could say something for certain, but i can't.

Re: Charging voltages lead acid deep cycle vs starting

rich,
even you are saying that the voltage should never have gotten that high because during bulk it won't be that high up and won't be higher (still less than 15v and dependant upon battery type, make, and model) until the absorb stage is hit where the voltage is then limited meaning the charger may be defective or it is not a regulated charger. it is difficult for me to say that is the case for sure as i didn't totaly understand the scenario given, but i do know if the battery voltage is allowed to go that high they are overcharging.

Re: Charging voltages lead acid deep cycle vs starting

it does give me the impression that it is regulated when set for 12 or 25amps and diminishing current means it has to hold the voltage to do it, hence voltage regulation. maybe you should contact them again before giving up and let them explain better as a regulated charger should not be showing voltages up in the 16v range even briefly imho.
did you look at my thumbnail to balance the battery charge below as i've just figured out how to post it no thanks to everybody else's help?

Re: Charging voltages lead acid deep cycle vs starting

landyacht.318 wrote: »

Thanks for the responses. I guess the stock sb2512 settings are close enough. One reason I ask is that I have a schumacher 2500 2/12/25 amp "smart" charger, and sometimes when I top off the batteries I see the voltage go as high a 16.4 volts. This charger says nothing about having an equalize function. This only seems to happen when the batteries are nearly full. If I run the charger with about 85% in the bank them it never goes above 14.7 volts. 95% and it climbs to 16.4 and I disconnect it.

The only reason I'm resurrecting this old thread is that I think I finally know the secret to Schumacher smart speed-chargers after having looked at the patents for them online, since detailed information is a bit scant in the manuals.

The patents reveal that like some other smart chargers, there is an optional pre-bulk desulfation stage. This boosts low-voltage (typically under 10.5v but not entirely dead) batteries to the point that it will accept a normal bulk charge. On some models there is an indicator that it is in this stage, and will eventually time out with a bad battery indicator if it is not successful. My NOCO will do this automatically too, although there is no indicator.

There is also an optional post-bulk/absorption test, that seems to measure the rate of discharge (and other metrics) before deciding whether to go straight into float, or into a high-voltage EQ & Desulphation stage both accomplished with the same technique. It is automatic, unlike my NOCO which takes a manual user-selection to forcefully go into an automated "16v boost" or recondition. CTEK's and others may have this user-selectable option.

The Schumacher patents says that this is programmed in - that if it detects a sulfated battery it will do this EQ and sulfation routine, and the time it takes it uP controlled. So while the charger is smart, it does not mean that it should be unattended especially if you start out with a bad battery to begin with.

The manuals state that while these units are capable of providing a float/trickle charge, they are not meant to be maintainers with large batteries as we usually think of them. They will usually time out after an eternity in absorb and will use a bad indicator if the current setting is too low. However, IF the unit was successful with a proper *full* charge cycle, it WILL maintain (or go into high-voltage desulfate first depending).

That's where this thread made the light-bulb go off for me, and look up the patents. I believe that if you try to "top off" an already fully charged battery, there *may* be instances where the charger is fooled into thinking you have a sulfated battery, which acts like a fully charged battery - that is an extremely quick rise to absorb, and a very quick self-discharge - and the charger may go into the high-voltage sulfation routine unnecessarily. This where I think some go wrong trying to use a Schumacher as a maintainer on an already full battery - it just might go into an long absorb, or go high-voltage unecessarily since a full charge did not precede it and wait for the timeout timer.

I think that in my testing the best results have been achieved by doing what you did - using the charger when the battery has about 12.5v or lower rested OCV, and charging from there. I also make sure that I'm using a charge current of approximately .1C or thereabouts and the battery chemistry selected accordingly. I do not try to trick it with very high or low charging rates significantly beyond .1C although there is room for experimentation staying within published current inrush limitations.

Obviously doing an EQ on an AGM is usually not recommended by many manufacturers, although there are some that will allow it following their own routine. For those that will, my other concern is that an extended high-voltage *may* desulfate the soft sulfation, but the flip side of the coin is that high-voltage contributes to acellerated grid corrosion. I guess you eventually choose the lesser of two evils and hope that the high-voltage doesn't burn off the anti-corrosion grid material in the process of light sulfation recovery.

It might serve as a diagnostic to determine if your batteries are indeed sulfated, which can also be from just old age and cycling. I suppose that if it *always* goes into the high-voltage desulfation, then perhaps the batteries are indeed on their last legs - if you trust the Schumacher uP determination. I don't know what their capacity determination percentage is when all is said and done - 80%? 70%? 60%?

At any rate, it puts my mind at rest knowing that the high-voltage routines are not a defect, but a design feature. It is up to the user to monitor the charger, and put an end to the high-voltage routine if they deem it unnecessary or damaging to the battery. I guess it comes down to trusting the Schumacher sulfation-detection, and either letting it try to recover the light sulfation, or just pulling the plug and carrying around a little unusable dead-weight capacity.