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Open Roads Forum  >  Tech Issues

 > Proper AGM Charging - help - battery specification gurus

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Bryan

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Posted: 01/25/13 02:40pm Link  |  Print  |  Notify Moderator

I20 is the current associated with C20 or about 5 amp ( per hour) for 100 ah C20 .
.1A is a lot less than that it also is per hour

HiTech

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Posted: 01/25/13 03:52pm Link  |  Print  |  Notify Moderator

Mex if you are out there can you translate these specs at all to be applied to manual charging or a basic solar controller?

Jim

wa8yxm

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Posted: 01/25/13 06:04pm Link  |  Print  |  Notify Moderator

1ulk 30% of C (20 hour rate) at 1.75 vpc (volts per cell) OR 6 times I20 at the same cell voltage (no idea what I 20 is?)

A1urrent looks good but voltage is way low, I that a typo?

2:Absorption 2.35-2.40 vpc until charge in current < 0.10A per Hr/ Max Time 12 hour (I'm not really sure what 0.1 amp per hour means?? Is that .1 amp per amp hour capacity, or 9.2 amps for each of my batteries? Seems high?)

a2:Yes, that is 0.1 amp per amp hour as in the first. So for a 100 Amp hour battery that is 10 amps.

3:LFloat 2.24-2.26 vpc no time limit (Seems like a tight specification)

a3: Yes, and it is also the proper specification.

4qualize (!) 2.40-2.43 vpc until charge in current <0.10A per Hr/Max Time: 12Hr

a$: see 2

As for the temp coefficient, I can not comment there.

It looks like they only cary the chart to the max recommended operating temp of the battery.


Home is where I park it.
Kenwood TS-2000 housed in a 2005 Damon Intruder 377


MEXICOWANDERER

las peƱas, michoacan, mexico

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Posted: 01/25/13 06:43pm Link  |  Print  |  Notify Moderator

What in the world are these idiots smoking? AGM are zero antimony batteries able to take a higher voltage absorbsion and float limit. To properly administer AGM you really need a decent amp hour meter and better yet a kWh setting in the meter.

Run a baseline "test" charge profile and repeat charge discharge cycles for a week using the controller. Then at the end of the week, test and find out how easily it is to "fit" more kWh into the battery at a set voltage. Let's call it 14.6 @ 25C. In an hour with say 10 amperes POTENTIAL available your batteries end up accepting more than say .07 kWh the charge profile bulk setting is inadequate to keep the batteries charged. Purchase and use a cheapo IR thermometer device like the HF, and if you see the temp rise at all, the batteries are accepting power too quickly (high amperage) or too much quantity (excess + amp hours).

VRB reach a point, where at REASONABLE absorbsion limit voltage, they become less hungry and amperage falls off. This exercise must be done with good batteries as a sulfated VRB has skewed characteristics. Do it when the batteries are new.

With my el cheapo WallyWorld 29, I top charge it when voltage degrades to 12.7. I connect a HF 10-amp charger set to 2-amps. It starts off at around 6 amperes charge rate and voltage rise gradually becomes faster and faster. It may take 3 hours for voltage to rise to 14.10. But then within 15 minutes it'll rise to 15.0

Your VRB will tell you the same story if you let them. Even with solar panels if you have a regulator. You are asking "how much?". I am saying, use a NOMINAL voltage test limit of say 14.6 and watch and see what happens when you use this "new" increased limit over what your normal absorbsion limit is. If the batteries gobble up power like crazy raising to 14.6 you have an excellent indication your normal setting is inadequate.

Try this with anything other than a newer good battery and what you'll see will drive you nuttier than an outhouse mouse.

You will be comparing what you and they "think" is enough charge for the battery versus what the battery demands. I wouldn't get too carried away raising the test voltage limit too much.

Remember, you are comparing what you SEE as far as amperage charging, with voltage (watts) in relationship to the amp hour or kWh meter. Use the -+ amp hour totalizer (accumulation on the meter) to give you a better feel for this.

Again, this is to see where the battery is "AT" when everyone days it should be "full" to what the battery actually demands. The battery always wins the argument.

HiTech

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Posted: 01/25/13 08:26pm Link  |  Print  |  Notify Moderator

My typical charge discharge cycle in a given week will really be quickly going into float after the sun rises, and no draw in a day other than self discharge overnight which I am hoping is extremely low. Can I substitute something else reasonable to test, since 99.9% of the time these will be basically standby UPS batteries? I could simulate my parasitic draw of .2 a, but I am avoiding this as a daily draw of 5% or less on the batteries is supposed to be bad for them long term. I could also simulate 20a per day draw which would be my draw if I ever have to run the fridge long term, but it is the rare exception rather than typical. My inverter draw of running the microwave from batteries is also rare - a few times a year, and I don't yet have the equipment to simulate that.

Is this the thermal gun?

Ir thermometer

On sale for $25.

Jim

* This post was edited 01/25/13 08:48pm by HiTech *

mena661

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Posted: 01/25/13 09:48pm Link  |  Print  |  Notify Moderator

HiTech wrote:


Is this the thermal gun?

Ir thermometer

On sale for $25.

Jim
Yeah, that's good. I have a similar one.


2009 Newmar Canyon Star 3205, Ford F53 V10
Trojan L16 6V's 740 Amp-hours


pnichols

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Posted: 01/26/13 01:12am Link  |  Print  |  Notify Moderator

Quote:

To properly administer AGM you really need a decent amp hour meter and better yet a kWh setting in the meter.


Those instruments even may be overkill.

My AGM batteries come up to a "hard stop" on current acceptance when they reach full charge. I use a simple ammeter permanently wired into the main negative lead of the two parallel AGM batteries. Whether I've charged them for 10 days at only 13.8 volts or charged them first for 3 hours at over 14.X volts and then for 10 hours at 13.8 volts - the ammeter at the end says "zero" amps flowing into the AGM batteries in both scenarios or any voltage-time combination in between.

I just charge the AGM batteries at whatever voltage at whatever hours until the ammeter shows no current flow. However, I guess it must be a big deal to wire an ammeter into some RV battery setups.


Phil, 2005 E450 Itasca 324V Spirit

HiTech

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Posted: 01/26/13 06:38am Link  |  Print  |  Notify Moderator

I think you and Mex are saying that same thing about absorption limits. I have a cumulative Amp hour and Watt hour meter, but I am not sure how high it will record and if I just leave it running. I have two actually so I can reset one each charge and leave one over multiple cycles to find out.

Here I was thinking that at an overnight resting voltage of 12.92 I MIT be charged up finally, but the batteries still accept the same as they did at a resting voltage of 12.71v. On the 2 amp setting they are taking in around an amp at 13.4 (I would have thought that too low to charge, but it does seem to charge them as the resting voltage after charging at this rate does go up), or 3.5A at the 8 amp setting and an indicated voltage of 14.65v, and no discernible temp increase by hand but I am sure I would miss a small heating going on just by touch.

Hmm on edit, just after sitting overnight, the batteries now go quickly from 14.x up to 15.x volts on the 8 amp setting at less than 2 amps, even though they start of briefly at 5 amps and 14.4v.

I think maybe I am done, though the behavior change after just letting a pretty low level of surface charge soak in is dramatic!

Interestingly, on these batteries as with yours (apparently), 13.8 v is considered a charge voltage not a float voltage, and I saw them take a lot of charge on at 13.8. If you have the time it really seems to be a gentle yet productive setting for charging them.

Jim

* This post was edited 01/26/13 06:46am by HiTech *

HiTech

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Posted: 01/29/13 05:40am Link  |  Print  |  Notify Moderator

Ok I see what is going on here. The voltages given may be initial. Every line has an end condition underneath it, and I did not enter it for bulk. So maybe bulk voltage is the start condition?? The end condition for bulk is:

Max time (hr) = Ahr * 1.2/average current, voltage limit equal to ""Absorbtion "regulation" stage limits"

So really it looks like bulk can be up to 1.2 times amp hours that were taken out, or until voltage voltage hits 14.6v, whichever comes first.

Am I reading that right?

I am running some normal-ish cycles on the complete system trying to do what Mex suggested above. The bank started with a little over 38 amp hours (this would be 20% discharged if the batteries were at full capacity) drawn out after a full charge (current tapered to 1.5 A on an 8 amp charger and volts jumped). This is still pretty full so charging will not take advantage of all the amps the solar cells could give, but it is worth learning hits behavior as recharging from small discharge will be typical.

The solar cells are flat, in an area the has full sun only a couple hours a day and partial tree shade the rest. It was cloudy yesterday. The system put back 12.7 Ah. This morning the voltage is 12.69 after resting 12 hours. East Penn's chart says 12.80 or higher static voltage (24 hours rest) indicates a full charge. So it all agrees more or less, though I would guess I will gain more than 5% capacity after 15 cycles. We shall see.

Jim

* This post was edited 01/29/13 05:52am by HiTech *

mena661

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Posted: 01/29/13 07:27am Link  |  Print  |  Notify Moderator

HiTech wrote:

So it all agrees more or less, though I would guess I will gain more than 5% capacity after 15 cycles. We shall see.
Not AGM's but mine gained a little capacity after about a year.

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