A constant current 10AMPS load with Batt low disconnect @ 10.5 volts...
Need to design a MOSFET current source with huge heatsinks and a timer clock.any ideas...?

 

If time is not of the essence hook it up to a 10 to 30 watt solar panel (12V) and let it sit for a few weeks (monitor the fluid). The high output voltage from the panel along with the low amps will slowly unsulfate the cells if they are not too far gone. I did this with a RV Deep Cycle batt this summer for about a month and it finally came back. I had to service it once during the process(distilled water ONLY). It worked great backing up a solar slowpump with a 60 watt solar panel for the rest of the summer.

 

I'm thinking that your charger is not very good. It must have rather poor regulation if it approaches 14V no-load, but drops to 13.2V (and stays there) with the battery connected. Presumably, when the battery was new, your "float charger" got the battery voltage to ~14V?

If your battery is a flooded-cell deep-cycle type, I'm guessing that you have floated it at too high a voltage for too long, and the battery is now shot due to grid corrosion. Lead-acid Batteries are very intolerant of chronic overcharging. A flooded-cell battery in standby service should be floated continuously at 12.9 to 13.1V, with a monthly equalization charge for several hours during which the battery is driven into the gassing range (14.5 to 15V) for ~4 hours.

__________________
Mike ML.

 

Sivankls,

Just some expert batt input here. I forgot to post this earlier - sorry.

I have a few ??'s of my own regarding your post seeings I consider myself to be a batt expert - esp when it comes to any common Automotive FLA type, or Deep Cycle FLA type. That also includes all VRLA AGM or GEL type batts, as well as all other rechargeable types of household batts.

1st of all - how do you know it's a 100ah rated batt? Are you just guessing here, or does it actually state the Ah rating on the batt itself? If so - then it also has a brand name on it. What is it?

Reason I say this is because if it's a FLA Deep Cycle batt then it is NOT truly rated in Ah capacity - beings it's an Automotive or Marine type FLA batt factory rated in CCA or MCA, and both in RC. Only up until recently did the RV & Marine industry insist that Ah ratings be part of the specs on FLA Deep Cycle type batts. It is however a false sense of Stored Energy (capacity in Ah) rating seeings the type batt to begin with - namely FLA. After all - car batts - because of the nature of the Flooded Acid inside - have far less energy storing capacity just by nature of design. This coming from pure Physics 101 understanding of Stored Wattage Capacity - as measured by W/cm2.

2nd of all - how much DOD (Depth of Discharge) are you taking this batt down to? How big an inverter are we talking about here, and what are you running for a LOAD on it (how many watts total if you know)?

If you're taking this AGM batt down to the Inverter's Cutout Point (Low batt Alarm or Shutdown point) then you surely have lessened the lifecycles on this batt severely. Normal cyclic cycles can be as high as a 1000 over the lifetime of a good quality AGM batt - depending on if you follow good practices on the DOD part, and then on the care in recharging the batt. I've had almost all my AGM batts used in cyclic apps last me well over 9 years with good care and proper maint.

Anyway -

At one point you are saying it's a - quote - "tubular...Deep cycle battery" - unquote.

That would most likely be a Johnson Control made OPTIMA spiral wound batt, and would also be an AGM type as well, and not a FLA type batt. In other words an AGM batt is a NONE SERVICEABLE type batt. All 95% of the batt acid inside is held in suspension within the Glas-mat Matrix inside.

If you somehow have opened one (it) up, and hopefully you haven't btw - I would also hope you haven't tried to add raw SULFURIC acid like you at one point hinted on doing! At which point in either case the warranty would be NULL & VOID at that point, as well as that batt no doubt being then sulfated beyond any hope of a good desulfation!!

Everything not withstanding - you never did say which brand name charger and model # you are using to charge this batt.

Not to mention that JC has not had the luck they had hoped for when they first started making those OPTIMA batts for automotive use. They first were just intended as a SOUND SYSTEM backup - so as to ease the power drain on the main charging system in automotive use (ie cars, etc), and then people got the idea to replace the main car batts with them as well. That is when the failure rate went way up there! The failure rates were VERY HIGH, and I personally know of people in the "car show business" that have to replace them on a yearly basis. Not that the once a week car shows destroyed them, but more like because they go bad just from not being used as much. They (AGM type) just aren't meant for car use period! Not only that - the price is ridiculous as well.

Sounds like you are using one there by the way you described it be tubular (round celled)!

Charging an AGM batt is not Rocket Science, but then again sometimes choosing the right Rocket (charger) sometimes is!

If you need a great over the counter AGM batt charger do me a favor and let me know what you are using now.

Brand and Model # please?

Pix of the charger and/or the batt would be nice as well.

Frank