Whats normal voltage drop from a 4amp load? (210ah)

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My watt meter is not accurate anymore. Under load it was reading 12.15v but it turns out the real voltage was 12.3v as confirmed with 2 different multi meters.

time2roll wrote:
I am not convinced the batteries are fully charged. Did the charger hold 14.7+ volts until amps charging was less than one amp?
Have you verified full charge with a hydrometer?
Did you let them rest unconnected 48 hours and observe 12.7+ volts?

I agree the battery tender didnt get the flooded batteries fully charged. Was silly of me to say that its closer to expect 90%?

I want to say the watt meter read 12.61 today after resting 2 weeks. Hooked up 4amp for about 30 minutes. Batteries have rested an hour and are at 12.63v.

Maybe its normal to sag to 12.3v?

My fancy german hydrometer called them 1.285-12.280 brand new from the store. Which is higher than fully charged...?? It temp compensates. It worked good for repeating numbers. Accuracy i have no way to tell. I did not test them after the battery tender charge.

wopachop wrote:
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My watt meter is not accurate anymore. Under load it was reading 12.15v but it turns out the real voltage was 12.3v as confirmed with 2 different multi meters.

That changes nothing.....that is still too low for the circumstances you described. As others keep telling you, your batteries don't appear to be getting fully charged....not even close.....

wopachop wrote:
I think the battery tender goes to 14.3 or 14.4v while my flooded batteries want 14.8?

Pretty sure the battery tender is 5amp. Im using it as a temporary charger to cycle the batteries in the garage once a week. Bought the new batteries for a camping trip back in Feb and didnt need them. Should have waited as im plugged in most the time.

Your batteries ARE seriously undercharged!

Even with a 5A charger your batteries may not ever see 14.3 or 14.4V for weeks. A 5A charger connected to a 210Ahr battery simply cannot sustain a high enough voltage until the batteries have been sufficiently charged to 99%. Only then will a 5A charger be able to continue to increase the voltage..

Your 5A might be fine for a small motorcycle battery, but for 210A GC batteries it simply will not cut it and soon you will be replacing the batteries and still wondering why you only got a yr or two out of them.

For proper charging, you NEED a REAL charger capable of min 10A-15A or higher. The higher the better.. Like I said, you NEED to wallop the batteries, small chargers simply are not able to provide a high enough continuous voltage to charge at a high rate.

You ALSO need to fully recharge the batteries AS SOON AS POSSIBLE, it is critical the moment you are back to get them charging AT A HIGH CHARGE RATE. The longer they sit around in partial discharge the more irreversible damage is done.

Good battery management makes the difference, not the brand, I have no issue getting 9 yrs out my one pair of GC batteries and they play a critical role since I depend on them to power my home fridge conversion.. Failure is not an option in my use..

For about $40 with 20% off coupon you can get an old school non smart 2A/10A battery charger at Harbor Freight.. If you watch for sales they often have them for $29!

HERE

You do not need a "smart" charger or multi stage charging for what you are doing, you simply need a charger which can get your discharged batteries filled up as quick as possible.. That HF charger will do the job within a day or two and you do not want to leave it on for much longer than that.. Otherwise you will boil the batteries dry!

Alternately if you find a deal for a 35A-45A RV converter you could use that instead.. Perhaps watch your local Craigslist for used WFCO units.. Folks tend to replace them with better units but they can function as a battery charger with multi stage charging..

A maintainer will never fully charge a pair of GC-2's. Period.

They are designed and intended to maintain a fully charged battery, at full charge.

0.5 amps is never going to cut it as a charger on a battery larger than 20Ah capacity, even if it will output that much amperage until battery voltage climbs to 14.4v.

You are destroying your new batteries.

A hydrometer will open your eyes. So many people have ridiculous faith in their product's marketing, when a hydrometer will prove that their whizzbang charger is incapable of doing anything that its marketers claim it can.
'But the green light was on!!!!!"

SMACK!

We have the red HF charger here too. I trust the battery tender more to be honest. I wanted to leave it overnight. Instead of pumping in 10amps for a certain amount of time. I understand it has a "normal flooded" setting.

So i restarted the test. Batteries rested for 1 hour and were at 12.64v.
Plugged in 4amps and lights and at:
1. 10 mins 12.43v
2. 20 mins 12.42v
3. 30 mins 12.41

Not sure why i got 12.3v earlier.

So lets start over. Lets pretend we trust the voltage of my new batteries and theyre at around 90%. Is that normal to sag to 12.4v with a 4amp load?

For a pair of GC2 at 90% that could be normal. GC2 does sag a bit more under load than the 12v combo batteries.

Also a GC2 will take 10 to 25 cycles to reach full capacity. Although don't expect to gain much.

wopachop wrote:
We have the red HF charger here too. I trust the battery tender more to be honest. I wanted to leave it overnight. Instead of pumping in 10amps for a certain amount of time. I understand it has a "normal flooded" setting.

So i restarted the test. Batteries rested for 1 hour and were at 12.64v.
Plugged in 4amps and lights and at:
1. 10 mins 12.43v
2. 20 mins 12.42v
3. 30 mins 12.41

Not sure why i got 12.3v earlier.

So lets start over. Lets pretend we trust the voltage of my new batteries and theyre at around 90%. Is that normal to sag to 12.4v with a 4amp load?

NO.

Not "normal".

Not good.

12.64 is not FULLY CHARGED AT REST, should be right around 12.8V.

THEY ARE PARTIALLY DISCHARGED.

You are on the road to ruining them by allowing them to continue on at that state.

Throw that "maintainer" out, forget about it for THIS PURPOSE.

USE THE STUPID HF CHARGER FOR WHAT YOU ARE DOING.

That HF charger WILL NOT "PUMP" IN 10A for the entire time, it WILL TAPER as the voltage of the batteries rise and will do no harm (or much less harm than severely under charging which is what you are doing).

LEAVE IT ON FOR AT LEAST TWO DAYS TO ALLOW THE BATTERIES TO GET FULLY CHARGED.

Get it?

Gdetrailer wrote:

Get it?

Yes i get what youre saying above but it doesnt relate to this particular example. Thanks for trying to help though.

"My fancy German hydrometer called them 1.285-12.280 brand new from the store."

Ok, so that is right. You then pulled them down by 20AH, which is not much, so they should be doing better. So the question is - how did you measure that 20AH? Perhaps it was more than that?

The big question is what is the SG now? If not too bad, then we have to question the other numbers. Mostly, believe the hydrometer.

Another thing about voltage drop is where you measure it on some wires to a meter. Long and thin wires can give you a bigger drop than taken right from the battery posts.