Capacity Testing and 20 HR Rating

The Trimetric is set up for 430Ah, so it may be off somewhat. I'll be keeping a close eye on things, throughout, so I'll keep track of the average amps being drawn. I'll log everything down about every 20 minutes to half an hour.

jrnymn7 wrote:
o.k., good to know (i did wonder about that)

I think I'll have to grab a couple of pigtails, and run a pair of 100w bulbs. Then I can add a 7w, 10w, and/or 15w to it if necessary. I'm guessing 200w may be a little low?

It will be a bit low if you use your Xantrex maybe. I moved my 2000w Vector inverter to the truck camper and now have a 2000w Can Tire Xantrex instead in the 5er.

The Xantrex draws fewer amps to run the toaster, kettle, or microwave than the Vector did, which was close to the divide by 10 rule. So the newer Xantrex might be more "efficient" and so 200w would be a bit low perhaps. Try it and see before your actual tests.

(One thing I don't like is the Can Tire 2000w Xantrex (was on sale for $169) has its 11v alarm spec as 11 to 11.3 ish and mine is near 11.3, which is bad when you are down in battery and want to use the toaster. OTOH the alarm is not very loud, unlike the Vector's air raid warning siren at 11v, so it is easy to ignore! :)

o.k., good to know (i did wonder about that)

I think I'll have to grab a couple of pigtails, and run a pair of 100w bulbs. Then I can add a 7w, 10w, and/or 15w to it if necessary. I'm guessing 200w may be a little low?

Using inverter loads to get 21.5 amps draw average over the 10 hours would be say 200w of 120v lights using the divide by 10 rule for inverters (yours might be a little different from that, they do vary somewhat)

Start with the 200w of lights at 20a and let it run so by the 5 hour mark amps are up to 21.5 and by the 10 hour mark amps are 23

SG is supposed to decline linearly with SOC down past 50% so you can use SG without worrying about "SG lag" like you get with a recharge.

BFL,

That makes sense to me. I'll try my best to take all things into account... SG, OCV, Ah countdown.

And your point about loads creeping up on inverter use rings true. I discovered the other day, my microwave does indeed draw 1080w, but the current is at 10.3a, instead of about 9, because of line loss. The kill-a-watt continues to prove itself as being a rather useful little device.

I figure a 250w/120v load should average out nicely. So, what can I use? hmmm.

Mex,

In the video, the guy uses a 2.3a load on a 105Ah battery. He then recharges the battery using solar. Then he compares Watt hours in and out, at least I think that's what he did. He lost me from the get go.

You first charge them up to baseline SG near as you can.

Then run them down at their 20 hr rate ( 430/20 = 21.5) for 10 hours or till they get to 50% SOC by SG (around 1.190 depending on brand) whichever comes first.

The trick is to find the constant amps load. Your DC lights draw fewer amps as time goes on and battery voltage drops. (lights get dim, so draw fewer amps) You keep turning on another light to stay even. With an inverter load, the amps creep up as battery voltage goes down, so you have to juggle that.

It isn't a science lab, so somewhere close is good enough to get you the info you are seeking.

So let's say it took 9 hrs to get to 50% instead of the 10 hrs. Your capacity is less than rated AH. How much less?

9 x 21.5 = 193.5AH your capacity is twice that = 387AH and 387/430 = 90%. (I keep thinking 9 out of 10 for half is 20% missing, so I have to do it this way to get it right)

EDIT if you have a Trimetric, you can confirm the AH count to 50% (by SG) and compare with the time based calculation above to see if it all "matches"

https://video.search.yahoo.com/video/play;_ylt=A2KLqISaflJVqHwAJBUsnIlQ;_ylu=X3oDMTByZWc0dGJtBHNlYwNzcgRzbGsDdmlkBHZ0aWQDBGdwb3MDMQ--?p=How+To+Do+a+Battery+20+Hour+Capacity+Test&vid=8dfb5f2968df78e0a87777641a7fe212&l=3%3A59&turl=http%3A%2F%2Fts1.mm.bing.net%2Fth%3Fid%3DWN.LP7TLZ3p%252fN%252bjXLKK8312Yg%26pid%3D15.1&rurl=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dhrq67tYV1Pw&tit=Battery+Capacity+testing+-+Part+1&c=0&sigr=11b3mlj4m&sigt=1110tug12&sigi=1238n274a&age=1303892518&fr2=p%3As%2Cv%3Av&fr=yhs-mozilla-001&hsimp=yhs-001&hspart=mozilla&tt=b


Video player does not work in this machine. But this otter get you started...