Mixing Batteries on Float-- Mex Test Update 2

[BFL13]

UPDATE 1 on 23 Dec post
UPDATE 2 on 25 Dec post
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Mex is driving me crazy! He said do not mix my used 12s (Scrubber batteries, he calls them--humph! They are respectable golf car batteries I'll have you know. Humph!) with my regular bank of 6s or they would evilly interact, and I would ruin my good 6s. I asked if that were still true if they were all on a Float charge.

Mex said they would still have evil interactions even when all on a Float. So I have gone ahead at some inconvenience to keep the used 12s and the good 6s apart.

Now all of a sudden, Mex pipes up in another thread with this!!!

MEXICOWANDERER wrote:
Batteries should be separated after the charging protocol. Connect all batteries together and apply 1 nominal 14.2 charging volts and there is no way any of the batteries can detect it one battery or a hundred are online, or the chemistry of any of them. The only requirement made of a charging system is that it not under or overcharge the battery. Voltage requiments for flooded 5% antimony batteries and pure lead AGM is similar enough for multiple warhead work.

It's when the charging ceases that the problems arise.

So go ahead and use a smart solenoid to parallel charge the batteries. I have done this too many times to count.

What is going on here? Are there evil interactions or not as long as they are charging or on a float? Does this leave the time they are discharging together as when the evil interactions get going?

If they are banked on solar, they discharge at night and charge during the day. So the evil interactions come out after dark? Can I just call Ghost Busters?

[MEXICOWANDERER]

Words I dreaded

"I DID turn on the light"

"Honey, where's the flashlight?"

"The heater quit. You're the genius. YOU get up and find out what's wrong"

[BFL13]

Thanks Mex. I have recharged and put everything back to Float as between camping trips. I am happy I have a good batteries going into next year based on your tests, and on the way they have been working recently while camping. I'll have to find something else to fret over. 🙂

[MEXICOWANDERER]

I believe starting the test immediately after conducting a "Top Charge" will offer a dependable base for comparisons. Putting a one to two ampere charge across the terminals and waiting until the voltage reaches 15.00 then terminating, is the way I used to prepare a flooded battery for a capacity test.

The reason for confounding information between acid density and electrical performance is that plates that shed or warp their active material have little effect on acid density and less than expected derogatory effect on square wave resistance testing. A 20 hr capacity test is most relevant, along with a SG dip, then load testing with a carbon pile.

It would be interesting for several readers to conduct a 200 amperes for 15 seconds load test on a pair of their GC-220 golf car batteries then post the results on the forum. With this baseline, it would be difficult to get fooled whether a battery is good or not. Memory fades here, but I remember something about 9.9 volts.

[BFL13]

I think Mex meant to do a load test using the AH it took to raise the voltage from x to y, but you would need the battery to be somewhere below full to do that! 🙂

[NinerBikes]

.18 amp hours to max out the surface charge to 14.40V. Will be a learning experience to hear what Mex has to say about that, and what it tells us about condition/state of the battery.

I'd think you'd want to put a known load on the battery and run it for time until it drops the voltage to 12.16V or whatever is 50% times the known draw item in amps, to test total residual capacity of an older battery.

[mena661]

pianotuna wrote:
Hi mena,

By inference 1.8 amps x 6 minutes. That's 0.18 amp-hours.

Oh, duh. LOL!

[pianotuna]

Hi mena,

By inference 1.8 amps x 6 minutes. That's 0.18 amp-hours.

[mena661]

How many amp hours going from v12.58 to v14.40?

[BFL13]

Looks like we have completed this part of the test:

They seem to have stopped dropping in voltage so quickly.
was 12.72/12.66, then 12.66/12.61, then 12.63/12.59, now 12.62/12.58

Next is the recharge test from 12.6 to 14.4. I will try that on one of them first to see how long it takes, and if any tricks to it using a Vector charger set at 2 amps (does constant 2.2a according to its read-out and it goes to 14.6v). Then I'll know how to do the other one

EDIT--I think Mex left out what starting SOC to use! I was wondering if they would hit 14.4 right off since they are already 'full'

"The one amp (2 or 3 amps is acceptable) recharge kWh test is easy to do. Stop charging when voltage stabilizes at 14.4 then see how many kWh have accumulated."

So I clamped on the charger to Battery B and the voltmeter and watched the time. Charger ran at 1.8 amps steady the whole time.

It took 6 minutes and five seconds to get from 12.58 to 14.40

I let it run and voltage got to 14.62 in another minute and a few secs, then the charger stopped, said FUL

[mena661]

NinerBikes wrote:

And the nice thing about running things on solar during the day is that the voltage is higher, so it draws less amps during the day, leaving more amps to go into the battery for recharging purposes. Seems like a win win to me.

X2

[NinerBikes]

mena661 wrote:

BFL13 wrote:
I think what mena meant by "masking" with solar is just that you don't need as much battery capacity when on solar, since during the day you can run things from the solar. So if your battery has less capacity than rated, you won't notice because you never get down near 50% anyway.

This. 🙂 I'll add that most RVer batteries die due to sulfation from never getting a complete charge although that seems years in the making for a good portion of people here. There are some shorted cells thrown in there too.

And the nice thing about running things on solar during the day is that the voltage is higher, so it draws less amps during the day, leaving more amps to go into the battery for recharging purposes. Seems like a win win to me.

[BFL13]

Today they seem to have stopped dropping in voltage so quickly.
was 12.72/12.66, then 12.66/12.61, today 12.63/12.59

Should be an initial drop from losing surface charge, then a slow drop from self-discharge. I wonder if these numbers mean my resting voltage at full charge is more like 12.60 instead of 12.73.

Trojan says 90% is 12.58v

Now I know that "evil interactions" is between cells in the same battery and I don't have that, so Mex's test has been very helpful in giving me the picture here what I can do. I think it is safe to bank them all while camping like I want to do, and keep them separated at home like I do anyway.

I can have the one bank for solar to worry about instead of two, plus get some Peukert going, plus the Trimetric can monitor the whole thing instead of just part of it. When going home from the seasonal off grid site as we do anyway fairly often, I can take two of the six batts on rotation for their 100%, leaving four as the working bank in the trailer, and those four can be two 12s and two 6s at times. No need to do all that complicated split bank solar equalizing.

[mena661]

BFL13 wrote:
I think what mena meant by "masking" with solar is just that you don't need as much battery capacity when on solar, since during the day you can run things from the solar. So if your battery has less capacity than rated, you won't notice because you never get down near 50% anyway.

This. 🙂 I'll add that most RVer batteries die due to sulfation from never getting a complete charge although that seems years in the making for a good portion of people here. There are some shorted cells thrown in there too.

[BFL13]

Battery life is measured in cycles and also in how deep those cycles are. An RVer unless a full-timer just doesn't do many cycles per year, so that is not an issue. That leaves battery maintenance as the real issue for RVers. Undercharging, etc.

I think what mena meant by "masking" with solar is just that you don't need as much battery capacity when on solar, since during the day you can run things from the solar. So if your battery has less capacity than rated, you won't notice because you never get down near 50% anyway.

It seems I don't have any bad cells as such in my used T-1275s, they have a lower than rated "resting voltage" when full, indicating some lost capacity. Apparently they also have that antimony poisoning thing which makes a drain that needs making up by the float charger adding more float current than it would normally supply. I am not concerned about the wasted energy doing that, but somebody with a huge bank like a telephone company would. I am not sure how short that makes battery life though, compared with other battery-life shortening things an RVer like me does.

Before taking home the free used T-1275, just stick an hydrometer in it and if you are in the white in all cells, you can probably nurse them all into the green later. If one or two are in the red and the rest are white or green, I wouldn't bother taking it home. EDIT that's with its voltage up too. Of course if its voltage is down they will all be in the red.