Just another battery voltage drop question!

[Grenadiers]

Wife and I have been adding on to our 1985 Saurer 6dm, for example, a 110v electrical system via generator or shorepower, along with a 2000w a 24v-110v inverter piggy-backed to batteries. I installed three sets of outlets, two for the 110v inverter, and one for the 110v via gen/shorepower. The original 24v/230v system is in place as well. And, we lengthened the cabin by 30", putting in a Splendide washer/dryer, a Thetford Cassette toilet. We have been working on the unit for the last two months, and recently been using the inverted battery power to run fans and power tools. The sun is low these days in northern Arizona, and at 6500 feet in the mountains we have a yard full of tall Ponderosa Pines blocking some of the sun's rays during the day.

Anyway, for the last few weeks, the batteries have topped out at 24.7 volts or so; the solar charge controller indicating 100% battery charge. Last night though, the bells and whistles on both inverters sounded off, the batteries were at 21v and change, shutting down the system. We ran a large fan all day, and a palm sander when needed.

I'm wondering if this is considered 'normal' for this time of year, and the usage it's been subjected to?
And further confusing the issue, is that since we got the solar panels reconnected to the original system, the solar charge controller has indicated a 100% battery charge even when the voltage indicated was 21v (batteries were at 96% while disconnected for three months).

We have a Steca PR3030 solar charge controller. Solar power is 320w. The 24v/230v inverter is a Victron Energy Phoenix Inverter Compact 1600w. The batteries are Lifeline AGM, GPL-4DL, 210ah each, connected in series. Right now I have shorepower connected to our Powerbright 110v to 230v/50hz step-up transformer which is connected to a Swiss-made 850w battery charger. The voltage increased to 24.7 in a few minutes, but the charging light is still on on the charger, indicating that that battery is still taking some juice.

Finally, in the Steca manual, direct attachments to the battery may affect the performance of the solar charge controller. Do you think having the piggy-backed 24v/110v inverter affected the battery voltage? Thanks. Dave. PS, I've left both inverters 'on' during this time as well.

 

[john61ct]

I never trust charge sources to accurately measure bank SoC.

You need independent tools, ideally calibrated with a pro's, to measure amps and voltage accurately.

Use these to adjust the charge sources' regulators to ensure:

A Absorb volts setpoint is at the high end of the mfg spec'd range, and

B transitioning to Float is not premature, not until trailing amps has reached the endpoint mfg spec

So e.g. maintain 14.5V until current has fallen to 1.5A

This usually means some trial and error adjusting the minimum absorb time setting, and of course needs to take into account any Loads running, taking current away from the charging process.

Only after you know your bank is getting to 100% Full every day can you judge whether your bank needs greater capacity.

If solar isn't enough, then you need to figure out how long to run the genny, get the bank up to 80-85% before the solar day starts.

A good SoC meter can help.

 

[john61ct]

For a 200+AH bank, 30-40A would be bare minimum for a shore power charger. Up to 120A would not be a waste of money, and increase proportionally if you think you'll be expanding bank size.

 

[john61ct]

If you think the SC might be broken, a Victron 75/15 is a great one for only $100, buy from a source with good return policy and you're only out the shipping cost if that's not the problem.

How old is the bank?

 

[Grenadiers]

June 2014.

Thanks for the info, from the manual it appears that the SoC or charging, is not programmable.
For generator, we have a 4000w connected to an Isola Basics 4000 voltage regulator (up to 40 in, 30 out) we bought in Mexico. The line connected to that is a 30amp 20 foot long RV extension cord which can plug into either shorepower or to the generator via a 30amp box I installed, which pigtails into a twist-lock 30amp plug to generator. If we're ever in Europe, there's a 230v shorepower plug-in on the side of the cabin, we're covered~!

 

[jonyjoe101]

if you can take the float voltage up to same as the bulk/absorb voltage. Just keep it at that voltage the entire time its connected to solar. The controller is probably cutting off too early and switching to float before battery is fully charged.
With the higher float voltage, when it switches to float, it will still be charging. Also measure the actual voltage at the battery if it differs from what the controller is seeing, you can raise the bulk voltage accordingly. I was 1/2 voltage short on my controller, it read 14.4 volts but the battery read 14 volts, I raised the controller absorb to 15 volts to compensate, now battery reads 14.4 volts.

Recently I got a coulomb lcd meter to track the SOC of my lifepo4 (works on lead acid also) Once program with battery capacity (up to 590 ah) and battery min/max voltage (handle 8 - 80 volts ) it keeps track of the amps going in/out of battery pack. For 22 dollars that I payed (50 amp version) its working pretty good. They got ones to handle higher currents. I'm going to get one for all my battery packs, instead of just relying on voltage to measure battery condition.


TK15 High Precision LiFePO/Lithium/Lead Acid Battery Tester Coulomb Counter 50A

 

[Grenadiers]

Nice, I'll look into that. My voltage at battery and then controller has been spot on. I looked into the programming, and the controller was set to Liquid/Acid batteries instead of AGM. Ooops. I changed it.

 

[Grenadiers]

Um, just thought of something, the controller was disconnected from the batteries for almost three months this summer. Would said controller, once reconnected, revert to factory settings? AKA, to acid battery, which is the default? I'm thinking that maybe the 1600 dollars in batteries might be toast. I changed over to AGM today, after charging, voltage is 25.3v. I'll know more by tomorrow I guess on voltage stability. PS, the Leab Automotive LPC-2425 (aka, ABC), finally found manufacturer's name, installed, charging the battery is in 'alert' mode, but is charging the battery. Indications from the diagram says 'bad battery', or, I could be wrong. Grrrrr! Online manual is in German. Me English. Can't justify buying cheap 150 dollar batteries to replace them. But...

 

[dwh]

3.5 years old, fairly heavy use, not charged to optimum...yea I'd say the batteries are probably shot. One indication is the voltage going up quickly. It should be taking quite a while to bulk charge.

The Victron 75/15 isn't big enough for 320w of solar. I've got 300w and a Victron 100/30.

Yes, disconnecting the charge controller from the batteries will probably reset the controller. The controller is powered by the battery, not the solar, which is why they all say to connect the battery first, then the solar.

Connecting the solar but not the battery might power up the controller, but could also fool its auto-detection of battery voltage causing it to possibly, for example, apply a 12v charge profile to a 24v battery, or vice versa.

Always connect the battery first, then the solar.

 

[Grenadiers]

Ooops, after reading your post, and then my last post, I was mistaken. When I removed the front wall of the camper and had to move the electrical panel, I removed the solar, not the battery from the controller. So, the PO might have had the battery type mistaken on the controller.

 

[Grenadiers]

Well, looks like the system fixed itself! I changed the battery type over to AGM on the controller, so far battery bank is holding around 24.3 volts. This is with our Waeco MDC-90 refrigerator running 24/7 for the last two days as a test. There has been 42ah consumed by fridge, and 48ah added to battery bank by the limited solar exposure. I had reset the cumulative totals on each to zero to get a baseline. Learning as I go, perhaps. The SoC is 99% which is encouraging versus it was stuck on 100% during the low-voltage situation. We have one of these to charge the batteries via 110v line voltage to our step-up transformer. Not sure if this has worked to pump up the batteries as it is in 'rot' (red) mode and supposedly, not charging a dead battery. http://www.leab.eu/en/products/battery-chargers/24v/abc-chargers.html we have an older version of the ABC-2425. The manual online is in German, so not quite sure how this is supposed to work. I 'assume' it should provide charging while Euro system is active, running lights, fridge, etc.

 

[Grenadiers]

Well, the battery situation has not fixed itself; what a surprise~! Anyway, last night I disconnected the batteries from each other, and connected two separate 12v trickle chargers. By morning, the voltage on each went up, but the SoC dropped from 99 to 64%! Weird. However, when sun was up in the afternoon, the voltage going in was in the 27v range, a first. So, am wondering if I 'shocked' the batteries into behaving, or just another dead end? I tried charging the batteries with the built-in charger, cooking along at 27v as well, but the SoC never went up. Do I just need to give it an overnight charge? I'm trying to avoid the 1100 bucks for a new set of batteries. The charging 'green' light was on for the first time using the charger.

 

[dwh]

How are you getting a SoC reading?

A 24v battery bank should be absorb charging at 28.4v (minimum) to 29.4v (my AGMs require 14.7v so x 2 for a 24v bank). They should be at a full charge resting voltage of 25.6v (minimum... 12.8v x 2).

It seems like every voltage number you've posted is too low for a properly functioning 24v bank.

 

[dwh]

And no, there is no magic. You can't "shock" lead-acid batteries into behaving. If they are sulphated (they are) there is no quick fix for that.

 

[Grenadiers]

After much fiddling, one battery at rest is 13.8 volts, and the other one is 13.5 volts. Hmmmm, bad second battery?