Battery Charging Questions

[WanderingCanuck]

Background: I have 2x 6V FLA GC batteries only running a fridge/freezer. Charging is completely manual from shore power at this time. I've had them two weeks (or one?) and have been trying to get them back to full SOC as often as I can, mostly by intelligent guessing. 
 
I've purchased a battery hydrometer and received it a few days ago. After taking readings at different times I've discovered I'm never getting the battery up to full charge, based on the battery spec sheet.

Battery:
http://usbattery.com/products/6-volt-batteries/us-2200-xc2-lf/

Hydrometer:
https://www.amazon.ca/E-Z-Red-SP101-Battery-Hydrometer/dp/B000JFHMRU

It says SG at full charge should be 0.1270 but I can't seem to get it there. I've seen max 0.1240 and min 0.1225.

The charger is a cheap one with 2A/12A "auto" settings, autotransformer type. I know it's crap, but I thought I'd have the opposite problem - overcharging.

So, where do I go from here? I can get a better shore power charger but would prefer not to spend a fortune on the "best". Is there one that will do a decent job without breaking the bank?

Or, is there something different I can do with this charger to get better results?  So far I've been putting it on the 12A setting for a few hours (3-5?) in the evening then the 2A setting overnight (7-9h).

Also, recommendation for DC current measurements so I can tell what's flowing, maybe the clamp style. Something accurate but not NIST cert level.

Thanks

 

[jonyjoe303]

according to the manual for the battery the bulk should be 14.7 volts (7.35 volts x 2), is your charger getting the battery up that high? When you got the charger connected, measure the voltage at the battery terminals, that will get you a true reading of how high the charger is getting the battery. 

If its not ever reaching 14.7 volts, the battery will never get a full charge like what the specs recommend. Also there will be voltage drop between the charger and the battery, especially if the charger wires are thin, your battery might not even be getting to 14 volts.

If the charger is never getting the battery to 14.7 volts, it is underpowered. Other people might know a good charger that can get up to 14.7 volts, most generic ones only go to 14.4 volts a good safe voltage for most lead acids. But you guess right, they will be expensive chargers. 

Though this doesnt apply to your situation, when I charge my lead acid with solar, I had a tremendous voltage drop, over 1/2 volts. to compensate I had to raise the bulk voltage on the mppt controller to 15 volts, just to get 14.4 volts on the battery. Your going to have to do something similar, raise that charger voltage up. In my situation I was always charging my battery at less then 14 volts for years. I was basically float charging all the time. Thats bad for lead acid.


manual specs for your battery from the link above
Following is the charging recommendation and charging profile using 2 stage chargers for US Battery deep cycle products. *Equalization and float charge modes are not considered to be one of the stages in a charging profile. 
1. Bulk Charge Constant current @~10% of C/20 Ah in amps to 2.45+/-0.05 volts per cell (e.g. 7.35 volts +/-0.15 volts per 6 volt battery) 
2. Absorption Charge Constant voltage (2.45+/-0.05 vpc) to 3% of C/20 Ah in amps then hold for 2-3 hours and terminate charge Charge termination can be by maximum time (2-4 hr) or dV/dt (4 mv/cell per hour)
 • (Optional Float Charge) Constant voltage 2.17 vpc (6.51 volts per 6 volt battery) for unlimited time
 • Equalization Charge Constant voltage (2.55+/-0.05 vpc) extended for 1-3 hours after normal charge cycle (repeat every 30 days) Notes: Charge time from full discharge is 9-12 hours. Absorption charge time is determined by the battery but will usually be ~3 hours at 2.45 volts per cell.
Float time is unlimited at 2.17 volts per cell. Specific gravity at full charge is 1.270 minimum (float 2.17x6 = 13.02 volts)

For current meter, I highly recommend this TK15 High Precision LiFePO/Lithium/Lead Acid Battery Tester Coulomb Counter 50A, you can find on ebay for 25 dollars. You program your battery AH capacity and it counts all the amps charge or discharged, if at night you use 50 amps, you know the next day you need to add 50 amps, this will let you know if thats what your charger did. When your battery reads 12.1 volts, the reading on the LCD screen should be 50 percent, if not you lost capacity. They ship from USA so you get it fast.

tk15 coulombmeter

 

[WanderingCanuck]

I just went out and checked.

Battery is in the higher range of SOC right now, somewhere in the ballpark of 80-90% maybe based on SG.

I switched the charger to the 12A setting and with a decent DVM I saw between 14.1 and 14.3V at the battery terminals. About 30 seconds later the "charge complete" light came on and the voltage dropped to 13.4 (or something close, can't recall exactly).

So, I think I'll have to admit defeat with this charger. I suppose I could go poking around and try to adjust the voltage internally, but I really don't have the time (read: desire) to reverse engineer the thing even it it was possible. I wonder if there's an easy way to modify the charger to remove the "automatic" feature so that I can use it manually... meh, I should probably get something more suitable.

Thanks for the recommendation on Coulomb meters, and I'll consider this for the future. For now though I'm looking for something more generic, like an add-on clamp probe for my DVM or another stand-alone unit. Though I already have 2 DVMs, so I probably don't need a third.

 

[Weight]

It will take days, if ever, to charge a deeply cycled battery with a 2 amp charger. With your 230 amp hour GC get at least 10 amps for the bulk charging. Don't trust the indicator lights on any device.

 

[WanderingCanuck]

You apparently missed the 2A/12A part.

I was trying to use the 12A for bulk, the 2A for absorption, manually switching it. But clearly this has not been working to get me back to 100%.

When the light comes on, the voltage is dropped down to something like a low end float voltage. This is why I mentioned it. I haven't trusted it as an SOC indication.

 

[John61CT]

The charger is a cheap one with 2A/12A "auto" settings, autotransformer type.

Besides the quality issue, the amps output should be .15C - .2C, so 20A per 100AH bank size.

10A per 100AH would be very bare minimum.

Eight hours at a time is plenty, even 6-7 may be enough, **if** you verify amps (with an ammeter) are dropping to .05C - 1/2 an amp per 100 AH capacity - **before** voltage drops to Float.

And that's the quality part, the charge profile must be adjustable if you want good longevity.

The charger usually costs more than the bank.

But a good one can last decades, while most people only get 3-5 years out of their bank.

With proper care, maybe 8 or more if great quality.

Lousy batts and poor care, maybe 1-2.

So up to you.

 

[John61CT]

I was trying to use the 12A for bulk, the 2A for absorption, manually switching it.

The transition between those stages is not controlled, up to current and voltage naturally.

Are you measuring voltage at the bank posts?

 

[WanderingCanuck]

Are you measuring voltage at the bank posts?

Yes, and I trust the DVM.

 

[max+sophia]

Lone Wolf, may I add a battery question to your thread?

My vehicle has some kind of short or other problem that over time, will run the battery down.  I have a maintainer installed, but have been advised that a multimeter would be a good idea.

Can someone familiat with this please tell me if <a href="https://www.amazon.ca/stores/page/B...=AstroAI Digital Multimeter with Ohm Volt Amp"><b> THIS MULTIMETER</b></s> would be a good choice?   Max

 

[John61CT]

Dunno.

Uni-T

https://www.amazon.com/UNI-T-Digital-Multimeter-Frequency-Resistance/dp/B00AW6SHNO

But better IMO to get a clamp style ammeter while you're at it, includes most useful DMM functions

https://www.amazon.com/UT210E-Digital-Zangenmultimeter-Multimeter-Tester/dp/B06XSMDMYV

Better https://www.amazon.com/gp/offer-listing/B005VUBGZW

Mastech also

Fluke is best 376, but pricey

 

[max+sophia]

Thank you John.   How does the way the clamping type is used, differ from the regular type.

Also, is there any way to permanently attach a multimeter to the battery, and have a readout in the cab?  Forgive me for the questions, but I know nothing. :blush:   Max

 

[John61CT]

Clamp style is portable lets you measure amps "live" at any point, measure a load device while cycling, a charger at the various stages.

A shunt is usually hard wired at a given location.

An AH counter keeps a running tally, one way or both.

For a BM, at the target bank, so all charging and loads go through it, guesstimates SoC.

 

[max+sophia]

Wow John,   :blush: I think I may have missed a few hundred lessons in this course.  Thanks.

 

[John61CT]

Put keywords like clamp ammeter

into Google with the "site:" operator

Example

https://goo.gl/xRbuJT

And soon you'll be au fait.

Also read http:marinehowto.com Ctrl-F search for three articles with Battery Monitor in the title.

The Victron BMV-712 manual

 

[John61CT]

Dupe

 

[max+sophia]

Put  keywords like clamp ammeter ...And soon you'll be au fait.

Thank you professor, I'm on it.

 

[WanderingCanuck]

I was on shore power for the weekend, so I isolated the battery bank and left it charging on the 2A setting (because the 12A setting would stop shortly after plugging in the charger, thinking it was "full"). This has enabled me to get it _so_ close to what the minimum should be, as I measured 0.1650 when I was ready to go back to battery use. It should have been obvious, but taking the load of the fridge off while charging makes complete sense. It draws less than the charger can supply, but not by much when the compressor is running. I just plugged it into shore power via the adapter while the charger limped along. I think if I do this for the entire weekend I just _might_ get a full battery the next time I try it.

On a side note, when I picked up the batteries I asked the guy to confirm that it was charged. This was a place that _only_ sold batteries; most of them larger than what I was purchasing. Their sign said they had been in business over 50 years. So I believed him when he said it was. However, looking back at the 12.45V I measured before connecting my load for the first time versus the voltages I'm seeing now alongside the hydrometer readings, it couldn't have been anywhere near 100% - right? I wish I would have had the hydrometer at that point, or had them show me with theirs. Live and learn.

For those of you that have and use a hydrometer, how to you store it? I mean, you really don't want an accumulation of excess battery acid dripping out anywhere - at least I don't. I've been filling a small containing with water and after each use rinsing it out with the water so that any remaining acid is very, very dilute. Then I stick it back into the storage pouch that came with it. I don't think the pouch will last long though. It's made from that thin, supple plastic that only stays bendable for a year or so before getting brittle and stiff.

I'm still trying to decide what's best for a charger. I anticipate going lithium at some point in the future, and at that point I may not have easy access to shore power anymore. I just don't want to spend a lot of money on a charger that won't be useful to me in a year or two. But I suppose if I consider what's been suggested about doing some of the charging cycle with a generator, the battery charger would still be useful. I just need to select one that would be compatible with that setup. Lots to think about.

It's a good learning experience, and I give credit to many of the people here for their help and suggestions along the way. I'm sure there will be more.

 

[max+sophia]

It's a good learning experience, and I give credit to many of the people here for their help and suggestions along the way.

Wolf, your posts are also helpful to people like me who know nothing about the various needs of batteries, chargers, gizmos like multimeters and coulombr meters, because you relate your actual experiences.  I'm still in the Schultz excuse "I know nussing" but I'm learning.

 

[John61CT]

Yes charger current sizing needs to take average / maximum loads as the starting "zero" point.

Then **add**

.15-.25C for FLA or GEL

.2-.6C for AGM

LFP can go to 1+C as desired for charging speed, may be limited by BMS.

And of course temp comp / protection should be present in any case.

 

[WanderingCanuck]

After writing that last story I came across a great thread from a few years back. Anyone following along with this thread should go and read this one too:

https://vanlivingforum.com/showthread.php?tid=6809

I don't think I was here yet when SternWake passed on (at least, I think I read that somewhere - do correct me if I'm mistaken). But his legacy remains and I've benefited greatly from his generous sharing of knowledge.