27DCs and SG Lag Problems

[BFL13]

Here is what I mean. Got two rebuilt 27DCs from Interstate as "Econo Power" models, which means they are whatever brand and type they decided to renew and sell at under half price. So just right for my purpose. But first to get them up to speed at home same as any battery first thing off the shelf before using it.

The batts seem to be Johnson Controls, all black, weigh 58 lbs, and are marked 27DC-845. Original date 5F (assumed to be June, 2015)

Doing one at a time, put the VEC1093 40 amper on them and let it get to "Full", which I know isn't quite full. I then ran an Equalize as I normally do to get to "real full" and it ran for a couple hours at 15.7v until it said Full.

SG all across was 1.300, so looking good. Then I ran my 10 hour 20 hour rate load test in hopes of finding out what the AH capacity is of the mystery battery (no rating shown--the 845 is no doubt the marine cranking)

It did take 10 hours to get to 50% SOC at 5 amps (I picked 100AH as most likely result) and proved 50% by seeing 1.200 SG and bounce back overnight to 12.17 volts. AH down from full was 51.6 by Trimetric, so Capacity came out as 103.6 AH at the 20 hr rate.

Now the fun part--recharge from 50% after ONE deep draw down, never mind after doing several 50-90s in a row.

Put the charger on same as before starting at 40.4 amps and let it run at 14.8v till it said "full" Sure enough SG was only 1.245ish in the white. So ran an Equalize which took a couple hours at 15.7 and SG was now 1.260ish. Ran a second Equalize for another couple hours till it said Full, and SG now 1.265ish, just barely into the green.

Rats! This is just like old times with 27s 😞 I used to tip them on their sides at this stage to try to get them up to full SG. But today I have a new weapon I did not have eight years ago-- my PowerMax Adjustable that can do 16.5 volts (with 15 minute shots, so you have to be there to keep doing that. It drops one volt after the first 15 minutes, and then stays at that--15.5 in this case, so unplug and start again at 16.5)

So after two of those--30 minutes at 16.5, the darned SG has hardly moved up at all still 1.265ish. I decided to give it time to cool down when SG will go up a bit with colder fluid, and I will leave the batt on float overnight at 13.8 and give it another kick or two tomorrow.

So what's with these 27s anyway???? There they were at 1.300 and you do ONE drop to 50% and it is like pulling teeth to even get back into the green, never mind 1.275 or above. I hate 27s !!!!!!
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Background info--not needed unless you are bored 🙂
Eight years ago, I swore off 27s because of my difficulties getting them back to proper full as seen by hydrometer readings. No such problems with 6s or the Trojan 12v T-1275s I have been using since. They come right up. No fuss.

I just got these two 27DCs as a stop-gap for rounding out the battery bank now that my two T-1275s finally died, and I need two batts to go with my six-year old pair of 6s that are still going but for only another year most likely. (I need about a 400AH bank) Then next year I can start over with all new whatever.

[MEXICOWANDERER]

https://www.ebay.com/itm/Electric-Electrical-Power-Outdoor-Switch-Timer-for-Extension-Cord-Christmas...

[MEXICOWANDERER]

https://images-na.ssl-images-amazon.com/images/I/71V7Mwr4mqL._SL1172_.jpg

[lawrosa]

Yes adjustable... I would need access to the dial though....And be able to read the meter.. Dont know if I can do it...


http://www.bestconverter.com/Boondocker-BPCM-60-60-Amp-Adjustable-Power-ConverterCharger_p_585.html#...

[lawrosa]

MEXICOWANDERER wrote:
There is the HARD WAY then there is the EASY WAY. Choose wisely

Watts that!!!!!

[MEXICOWANDERER]

There is the HARD WAY then there is the EASY WAY. Choose wisely





Damned near thinking about assembling KITS for the MEANWELL and MEGAWATT

• AC power cord 3/16 wired to Intermatic 4-hour timer then to correct PIN terminals
• Twin color coded 12-gauge battery cable connectors -clips- soldered

[BFL13]

The battery has an "acceptance rate" in amps for its SOC and the charging voltage set. As SOC rises, the acceptance rate declines so you get that tapering.

Also, at whatever SOC and the acceptance rate then in effect at that set voltage, if you jack up the voltage, the acceptance rate in amps goes up. Some of the charging amps are wasted as heat if you over- do this idea.

So naturally you can do more amps at that 15.3 than at 14.4 at whatever SOC they are at now.

In fact since the SG is hardly rising your batts are near full as they are going to get. The sulphation is mostly now "hardened" so high voltage "de-sulphation" won't do much good.

Those 24s are worth about $20 each for core charge when you buy the new 6s. (at least that is how it works here)

[lawrosa]

BFL13 wrote:
Go back to the basics and then read that again.

When you start the recharge, the charger is set at some voltage or other. Say 14.8. The battery voltage rises to that. That was the Bulk stage. Now you want to hold that voltage there and do the Absorption stage, which has the amps tapering until the battery is charged up. Then, you want to go to the Float stage voltage so you don't overcharge the batteries by staying at that high absorption voltage.

The Iota is set at 14.8, gets the batts to 14.6 (not 14.8) and then it drops to 14.2 and does the absorption stage. It drops to 14.2 shortly (15 minutes) after getting the batts to 14.6.

How long is the bulk stage? It depends on the charging amps of the charger compared with the AH capacity of the battery bank and how low that was in SOC at the start. The higher the amps per Bank AH, the faster it will get the batts to 14.6. and at a lower SOC before Absorption starts. It will only do all that time it says there in Bulk if the charging amps are low and the battery bank is big.

If you are only charging on shore power, you have lots of time to do the recharge, but if you are doing it while camping running a generator, then you want to get it done quickly. Fast recharge means with the high amps, so you don't want it to drop to 14.2v and slow the recharge way down. You want to stay at 14.8 the whole time it takes to do your "50-90"

Understood. 14.4 wins out..

So riddle me this..

I have these 12volters on the sears charger. Charging 10 amp setting @15.4 volts and 4 amps going in. SG is now at 1.250.

Its been 2 hours.

Can I conclude any information from this?

Why wouldnt the PD put in the amps @ 14.4? I know you say about the false voltage so just trying to grasp it..

Im not trying to beat a dead horse..

Going 6 volt and seeing how they charge all these issues may go away so it probably will be a mute point.

[BFL13]

Go back to the basics and then read that again.

When you start the recharge, the charger is set at some voltage or other. Say 14.8. The battery voltage rises to that. That was the Bulk stage. Now you want to hold that voltage there and do the Absorption stage, which has the amps tapering until the battery is charged up. Then, you want to go to the Float stage voltage so you don't overcharge the batteries by staying at that high absorption voltage.

The Iota is set at 14.8, gets the batts to 14.6 (not 14.8) and then it drops to 14.2 and does the absorption stage. It drops to 14.2 shortly (15 minutes) after getting the batts to 14.6.

How long is the bulk stage? It depends on the charging amps of the charger compared with the AH capacity of the battery bank and how low that was in SOC at the start. The higher the amps per Bank AH, the faster it will get the batts to 14.6. and at a lower SOC before Absorption starts. It will only do all that time it says there in Bulk if the charging amps are low and the battery bank is big.

If you are only charging on shore power, you have lots of time to do the recharge, but if you are doing it while camping running a generator, then you want to get it done quickly. Fast recharge means with the high amps, so you don't want it to drop to 14.2v and slow the recharge way down. You want to stay at 14.8 the whole time it takes to do your "50-90"

EDIT-- That high charging rate desired for a fast recharge means doing exactly the wrong thing for Marine/RV batts to get their SGs up, as revealed earlier in this thread. They like low and slow.
Another good argument for getting 6s!! 🙂 They like the fast recharge and their SG comes right up no fuss.

[lawrosa]

BFL13 wrote:

lawrosa wrote:
Looks like the iota is the way to go too.
14.8 bulk
14.2 absorp
13.6 float.

http://www.bestconverter.com/IQ4-Smart-Controller-1224-Volt_p_321.html#.Wrk0sojwaUk

Not really IMO. What you want is for it to get the batts to 14.8 and hold them there at 14.8 for a length of time as the absorption voltage. Dropping to 14.2 to do that is contrary to the charging specs for many battery brands and types of battery.

Your PD with CW will do a better job on your new 6s even at 14.4.

The Iota's IQ4 does not have that boost button like your CW has, so you cannot make it stay at 14.8.

Says 4 hours bulk or high trigger..14.8

Then 8 hours absorp at full current or constant voltage 14.2.

And the float 13.6 is beneficial no? 13.6?

Im trying to find specs on other modules.

BULK STAGE - During this state, the charger will operate either at Full Current output or Constant Voltage output depending
on the discharged state of the battery. A discharged battery will dictate the voltage and force the charger into constantcurrent
operation. As the battery charges, the charger transitions to a constant-voltage operation. This BULK STAGE will
continue for either 225 minutes or until the battery voltage reaches the “High Trigger” value (whichever occurs first). At this
point, the BULK STAGE will operate for another 15 minutes before switching to the ABSORPTION STAGE.
ABSORPTION STAGE - This state is limited to 480 minutes (8 hours) during which the charger will operate either at Full
Current output or Constant Voltage output depending on the discharged state of the battery. During Full Current output, the
charger is providing its full current rating and will slowly increase the battery voltage to the “Absorption Stage” voltage. At the
end of the 480 minutes, the charger will revert to the FLOAT STAGE.
FLOAT STAGE - This charge state holds the batteries at Constant Voltage for a period not longer than seven days. During
this state, the charger not only floats the batteries, but it can also provide load current up its maximum rating for other loads
without depleting the battery capacity. The FLOAT STAGE will end when either the battery voltage drops below the “Low Trigger”
point or at the end of seven days when the IQ4 initiates an equalization stage to remove sulfate layers from the battery
plates. In either situation, the unit exits the FLOAT STAGE and enters the BULK STAGE

[BFL13]

lawrosa wrote:
Looks like the iota is the way to go too.
14.8 bulk
14.2 absorp
13.6 float.

http://www.bestconverter.com/IQ4-Smart-Controller-1224-Volt_p_321.html#.Wrk0sojwaUk

Not really IMO. What you want is for it to get the batts to 14.8 and hold them there at 14.8 for a length of time as the absorption voltage. Dropping to 14.2 to do that is contrary to the charging specs for many battery brands and types of battery.

Your PD with CW will do a better job on your new 6s even at 14.4.

The Iota's IQ4 does not have that boost button like your CW has, so you cannot make it stay at 14.8.

[lawrosa]

Oh and looky here... They now make many different IQ moduales... wow.. Never saw that before..

Ill have to research what they all do...

I may sell both my converter bottom ends and get one of these...

Ill stuff it somewhere...

https://www.iotaengineering.com/IQ/#!/

[lawrosa]

Looks like the iota is the way to go too.
14.8 bulk
14.2 absorp
13.6 float.

http://www.bestconverter.com/IQ4-Smart-Controller-1224-Volt_p_321.html#.Wrk0sojwaUk

[landyacht318]

I went through this on the screwy 31.

Long version short I bumped up Absorption voltage and duration. Absorption to 14.9 then a float of 15.3 for the rest of the afternoon while the sun shined.

With plug in charging sources of higher amperages applied at the lowest state of chagre the Absorption voltage and duration could be lower, somewhat

Even with that excessive regimen the SG still walked down and after 15 cycles a 16v EQ charge was required for 50 minutes.

At about deep cycle number 500 during an EQ one of the cells bottoms was 10 degrees hoter than the rest of the battery and I removed it from my rig in june 2015

it still lives, but is only shallowly cycled. it has had its plates exposed as my 'smart' schumacher has an affinity for 16+ volts, but will still hold 12.82v 12 hours off the charging source.

Flooded group 24/27/31s are, in my opinion, poor at recovering from deep cycling without excessive voltages and durations at which they are held, and regular EQ charges.

And 14.4v is not enough for them.

[lawrosa]

Im afraid to go 6's but I think ill bite the bullet... State income tax is coming soon... I already have the battery boxes...

[BFL13]

Believe the SG, not the voltage. Read this again that mex posted from Rolls:

"....becomes a major and noticeable problem. This under charge condition is caused when batteries are deficit cycled. The bank receives less of a charge each cycle and starts to sulfate. Eventually, the sulfate will cause a resistance to charge and a “false high voltage” reading will occur. The “false high voltage” is measured by the charge controller, which further lowers the charging current to maintain the voltage set point. This further increases the undercharge condition. This is one reason why specific gravity measurements are so important as “false high voltage” readings can be misleading"

I think those batts are near their end at some lower AH capacity than new, not sure how much lower, but the SG is saying they are at about 75% of rated 150AH My 135AH WAG from the incomplete test run may be too high.

You and you alone have to assess the risk of going camping with them again if they will cause trouble or not, and if you have a work-around if they do.

If you have the height allowance, 6s have the same footprint as those 24s and two 6s will give you more like 225AH instead of 150.