Deka 8L16 charge perameters

cohippy420

Hi I need some advice. I have 500watts of panels a midnite classic 150 and 2 Deka 8L16 batteries. My charge parameters are as follows:
Absorb v:14.7 absorb time:3:00hrs
Float v:13.6
Eq v: 15.6

Here's my situation. These batteries are about 18 months old. They were abused last summer as there were too many people and too much power being used. OK well I handled that. No problems since.....except that when charged my voltage with settled batteries no load is about 12.6v. Ok next I have the batteries in their own out of the way spot.....out of sight out of mind....well they were forgotten about for about 6 months zero problems till one evening a few weeks ago the inverter alarm went off.....plenty of sun mind you.....well turns out batteries were "low" on water......almost 2 gallons low! So well I refilled them and shut the inverter down went on generator for a few days. Got them charged back up eq'd them they got to about 118f I think way too hot. Oh and the plates were dry before I added water.

So anyways I haven't had any more problems since.....but
1 what should my charge parameters be? I was told the classic can be set up not to rebulk the batteries everyday....do I need to set that up and if so how?
2 how bad did I likely sulphate my batteries? I Dont have any heavy loads I can use on my inverter....only a 2000w so it won't run the washer or miter saw.
3 is my absorb too long? It was set for 4 hrs prior to my trouble so I cut it by an hour.

Thank you

BB.

You really need to get a Hydrometer (this one is well liked) and measure/log your temperature corrected specific gravity for each cell.

You can equalize the battery if you have any low cells--And you can equalize/charge the battery until the SG no longer rises (after 30-60 minutes between readings, the SG no longer rises). That is your "new" 100% state of charge SG levels. Note, you normally try for >~90% of charge a couple times a week. Do not try for 100% every day--you will damage the battery (equalization is "hard" on a battery bank).

While taking a battery bank to low voltage cutoff/inverter alarm is not great--"boiling" (gassing/equalizing/normal charging) below the top of the plates is even worse. Oxygen from the air gets into the plates/grids and causes corrosion. So--That event probably did kill your batteries (or at least dramatically shortened their life).

Charging wise--You should be charging at a 5% to 13% rate of charge or so (and does your Midnite have a remote battery temperature sensor?).

• 370 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 348 Watt array minimum (weekend/seasonal cabin can be OK)
• 370 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 697 Watt array nominal (full time off grid minimum suggested)
• 370 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 906 Watt array "cost effective" maximum

So, you probably have enough solar panel for your use--And the starting numbers for charging do not look bad. A good way to tell if you are charging correctly is how much water does the battery bank use... More or less if you have to refill the batteries every ~2 months (DO NOT EXPOSE PLATES)--you are probably OK. If you fill every month or less, cut back on absorb voltage/time. If you are 6 months or more between fillings, you probably are under charging (a hydrometer will help you decide too).

And, lastly, a 2 kWatt inverter is pretty large for a 370 AH @ 12 volt battery bank--The largest inverter I would typically suggested for a flooded cell battery bank is ~1,000 watts (rule of thumb is ~400 AH @ 12 volts per 1 kWatt of AC inverter--Similarly, 1,000 watt maximum solar array per 400 AH @ 12 volt battery bank).

If you really need 2,000 Watts from your AC inverter--You may want to go to an 800 AH @ 12 volt battery bank--Or better yet, think about 400 AH @ 24 volt and a new AC 24 VDC input 2kWatt inverter... (it is hard/expensive to wire up a 2kWatt AC inverter to a 12 volt battery bank with ~0.5 volt drop at full/rated inverter output).

If your average loads are low--A 300 Watt TSW 12 VDC inverter may be good for most of your usage--Save the 2kWatt inverter for when you are running your power tools. Less wasted power by the inverter (6 Watts vs 10-20 Watts for a typical 2kWatt inverter--Plus the Morningstar has remote on/off and "low power search mode" to help conserve battery/solar power).

-Bill

vtmaps

cohippy420 wrote: »

is my absorb too long? It was set for 4 hrs prior to my trouble so I cut it by an hour.

Why use a fixed amount of time for absorb? You have a midnite Classic! You can control your absorb time with "end amps". All you need is an inexpensive shunt and Midnite's inexpensive whizBangJr.

The whizbangJr measures charging current (amps) into the battery. During absorb charging two things happen: 1) SG goes up (as Bill mentioned), and 2) charging current goes down. When the charging current stops going down (and SG stops going up), you are done with absorb and ready to float.

With a whizbangJr, your Classic can switch from absorb to float when "end amps" is achieved.

One more thing that Bill mentioned, but is worth repeating: Make sure you have Midnite's remote temperature sensor on your battery.

--vtMaps