Test amp draw on batteries?

Topic: Test amp draw on batteries? (Read 622 times) previous topic - next topic

Test amp draw on batteries?

October 19, 2020, 10:44:01 pm

Removed my 7 year old mk gels to test them. Was getting lower voltage at certain amp hours used recently versus new. Duh.

Cable ends where attached to the batteries were darkened some and some powdering was present.

Had not been touched since installed. Two sail batteries and one conventional terminal 8g8d's are the set.

Straight from the coach after a short drive they measured 13.24, 13.44 and 12.96.

hooked up a smart charger and all showed 95% SOC and took a few minutes to get to 100%.

Question is that I have three precision non UL(DaveS, haha)Chinese lab grade load banks that are adjustable from zero to 20 amps and am considering what exact load to put against the batteries to calculate their wear.

Been a tough life for them as my outside storage and the panels flat on the roof and only putting out 14 amps at best then lowered their charging amps in the winter at that low of the sun angle and so cal dirt on the panels.

Letting the batteries rest till tomorrow to see their starting voltages.

Lowering the batteries into a HF dolly was doable by myself. 158 pounds each. Returning them to the rack?

Not decided what discharge rate to use. C20 or C100? Seems to be 11.25or 2.65 amps load

Was going to replace them then thought better of it as I had put together enough equipment to test them all at the same time.

May rotate the 2 sail terminal batteries IF they test good upon reinstall.

We will see. Overkill on the test stuff but it's a hobby isn't it?

Re: Test amp draw on batteries?

Reply #1 – October 19, 2020, 11:10:25 pm

What is a sail battery?

Regards

Klaus

Re: Test amp draw on batteries?

Reply #2 – October 19, 2020, 11:23:51 pm

Flag post?

Re: Test amp draw on batteries?

Reply #3 – October 19, 2020, 11:49:31 pm

Corect on the flag post

Re: Test amp draw on batteries?

Reply #4 – October 20, 2020, 06:32:51 pm

Seems the batteries are really bad after seven years low power storage charging.

Did not need the fancy test setup but still testing.

Will test the red tops next

The higher numbers are after charging and before the load being applied.

The lower numbers were the volts with the 11.7 amp loads.

Will show the final numbers when the 50% of rated amp hours is consumed but the preliminary numbers show they are very worn.

Re: Test amp draw on batteries?

Reply #5 – October 21, 2020, 04:45:55 pm

Ran them down a 100 amphours per battery yesterday. Then let them rest till noon.

Recharging the 12.41 volt battery as it may test near enough to new to keep it and add it to three new 8g8d's I ordered today.

Ordered all three with sae terminals so they could be rotated versus 2 flag style that could not

Edit: my guru buddy thought I could get another 3 years out of the set.

I am picky and am replacing them still.

Anyone local here in so cal that could use 2 8G8D's that test excellent. Resting voltage is 12.94. Mk says 12.85 or better is per spec.

New is 13.1.

Tested at 200 amp hour capacity each now vs 225 new.

Flag terminals on these.

Re: Test amp draw on batteries?

Reply #6 – October 22, 2020, 02:13:24 pm

Interesting that the two flag terminal batteries did the vast majority of the work judging by the voltage drops under identical loads in testing now after seven years.

So the 2 flag batteries in essence did 10 or more years of the actual work.

Do not mix the terminals is the lesson I get out of this.

On the other side I will probably wire the good auto terminal into the 3 new ones for a 900 amp hour mk gel battery system.

We may do a certain amount of winter dry camping coming up so the ability to charge at below freezing temps may be needed

Re: Test amp draw on batteries?

Reply #7 – October 22, 2020, 06:13:51 pm

I wouldn't mix old batteries with new. The bad one will give the charger a charged signal when the others haven't topped off.

Re: Test amp draw on batteries?

Reply #8 – October 22, 2020, 06:22:31 pm

Quote from: craneman – October 22, 2020, 06:13:51 pm

The bad one will give the charger a charged signal when the others haven't topped off.

Suspect I misunderstand the theory but absolutely agree with the point.

Say the old battery has a bad/weak cell. So, instead of being a 12 VDC battery, it is a 10.XX battery. That will signal the converter or charger or inverter/charger to KEEP CHARGING since it knows that it should continue charging before going into float until voltage reaches the upper 13.XX's. All other batteries (the new ones) will keep receiving a charge (likely still at bulk voltage). That will well-overcharge them and materially shorten their life.

Re: Test amp draw on batteries?

Reply #9 – October 22, 2020, 06:27:09 pm

Quote from: wolfe10 – October 22, 2020, 06:22:31 pm

Suspect I misunderstand the theory but absolutely agree with the point.

Say the old battery has a bad/weak cell. So, instead of being a 12 VDC battery, it is a 10.XX battery. That will signal the converter or charger or inverter/charger to KEEP CHARGING since it knows that it should continue charging before going into float until voltage reaches the upper 13.XX's. All other batteries (the new ones) will keep receiving a charge (likely still at bulk voltage). That will well-overcharge them and materially shorten their life.

Correct I had it backwards. But knew it was a bad idea.

Re: Test amp draw on batteries?

Reply #10 – October 22, 2020, 06:31:59 pm

Quote from: craneman – October 22, 2020, 06:27:09 pm

Correct I had it backwards. But knew it was a bad idea.

Totally AGREE!

Re: Test amp draw on batteries?

Reply #11 – October 22, 2020, 09:55:49 pm

I agreed enough as my long experience showed just what was posted.

So I called Scott(DSD) this afternoon and made him an offer he could not refuse and sold him all three batteries which he will pickup tomorrow.

If you had had the number of battery issues the older coaches had you would not doubt my dislike of mis matched battery sets.

Replaced hundreds of sets as a matter of course on every used coach I sold.

I spent countless hours with battery hygrometers and charger as sales manager just to try every possible fix.

IF the third battery had precision tested to be nearly identical specs as new. Unfortunately still worn. Not close enough.

Supporting Scott's project in my own way.

I am happy that I have a set of useable mk oem gels laying around to help a forum member.

As a sort of prepper the need to have nearly perfect batteries is paramount for us.

But thanks for the thoughts from all of you.

We all agreed

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Test amp draw on batteries?

October 19, 2020, 10:44:01 pm

Re: Test amp draw on batteries?

Reply #1 – October 19, 2020, 11:10:25 pm

Re: Test amp draw on batteries?

Reply #2 – October 19, 2020, 11:23:51 pm

Re: Test amp draw on batteries?

Reply #3 – October 19, 2020, 11:49:31 pm

Re: Test amp draw on batteries?

Reply #4 – October 20, 2020, 06:32:51 pm

Re: Test amp draw on batteries?

Reply #5 – October 21, 2020, 04:45:55 pm

Re: Test amp draw on batteries?

Reply #6 – October 22, 2020, 02:13:24 pm

Re: Test amp draw on batteries?

Reply #7 – October 22, 2020, 06:13:51 pm

Re: Test amp draw on batteries?

Reply #8 – October 22, 2020, 06:22:31 pm

Re: Test amp draw on batteries?

Reply #9 – October 22, 2020, 06:27:09 pm

Re: Test amp draw on batteries?

Reply #10 – October 22, 2020, 06:31:59 pm

Re: Test amp draw on batteries?

Reply #11 – October 22, 2020, 09:55:49 pm

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