Identifying batteries

WillBkool

Hi everyone, new member, but I've been lurking and learning from this site for a couple months now.

My workplace recently, May, changed from an old PBX phone system to a VOIP system. The maintenance guys had a cart full of batteries and let me have some, six to be exact, although I could have gotten more if I had wanted, then I would need more panels, but that's a different story. They may not be the best batteries for solar, but they were free. They are heavy, around 70-75 pounds each, and they are in good condition, they hold a resting charge above 13 volts, and they were hardly used. There is a big diesel generator that kicks in quickly, so they probably only have a few minutes here and there on them. Although I also understand that float charges aren't the best to always use either, like I said above, they do hold a 13+ volt charge, even after several days. I've been charging them every week or so with a trickle charger, and I put a 10A charger on each one last week.

I plan on wiring them in a 24v system with 3 parallel banks. Don't worry I am going to use bus bars for connections. Right now I only have a 15A mppt controller that doesn't have much adjustment besides setting the type of battery and to equalize or not, but I plan on eventually getting another charger to bring my wattage up, and I hope to get one like the Schneider c35 where you can set the voltage, so I would lle to know if the 360's numbers will work.

I need some help identifying them, I've found what looks to be very similiar, but the numbers are slighly different. The ones I have are HRS12-400XP. The specs I found online are HRS12-370FR and are from the same company. I figure they are 100AH and maybe just a little bigger in the watts per cell/WPC than the 370 model. The 370 spec says to charge it to 14.4 - 15 volts and the float to 13.6 - 13.8 volts. The battery itself has a similiar float charge printed on it, 13.5 - 13.8 volts, but doesn't have a charge rate, so I think the one for the 370 will be okay. What do you guys think?

Well, sorry to be so long-winded, here is a pic of one of them. Sorry it's such a low res one.
Attachment not found.

Cariboocoot

Re: Identifying batteries

I don't know these batteries specifically, but they do appear to be AGM type which means you have a fair latitude on the charge current. Even with standard flooded cells you could go to 20% max current. So if you think they're about 100 Amp hours this would mean a net peak charge current of 5 to 20 Amps; lots of range.

The important thing with a sealed battery is to not overdo it on the Voltage, which is what makes the bubbling and gassing and thus causes the vents to open. Again it looks like you're in luck because it says up to 15 Volts. I'd suggest you stay with the 14.4 (typical AGM Absorb level); the 15 may be for occasional recommended EQ (not usually done on AGM's).

Floating at 13.5 to 13.8 is pretty normal too. Resting Voltage staying above 13? Good. Price free? Good. Looks like you've got a bargain for sure. If they do go kaput you're not out $, so the only issue then is how critical the application is. Not critical? You just scored 100%!

Did a quick search and they appear to be 102 Amp hours like these: http://www.latco.com.mx/pdf/mr12-400.pdf

WillBkool

Re: Identifying batteries

Thanks for the quick response! I found that same spec sheet and had hoped that's close to what I have. Their for an emergency backup system that I will also use for small loads daily. So, if they die a quick death, so be it. Now for the calculations I learned on this site.

Since I have 3 parallel strings of 24 volts, that gives me 300AH.
300 * 0.05 * 29 *1/.77 = ~565 watts to charge at 5%. I had calculated the 15 amps, and that is why I bought a 15A charge controller, but I didn't figure the 77% rate of the panels. So my 370w of panels needs about 200 more watts just to reach the 5%. Oh well, live and learn. lol

I'm also going to buy one of those Iota 24v chargers, would the 15A be okay or should I get one a little bigger?

Cariboocoot

Re: Identifying batteries

The 15 Amps net to the battery is okay, it's how much panel you need to get it.

Since current is at its maximum when Voltage is at its minimum (charging only - no loads) you get a calculation like this: 15 * 24 = 360 Watts less derating = 468 Watt array. Your 370 Watts will fall short, and if you have loads running at the same time you'd want even more panel to keep ahead of that drain.

Same thing with the Iota charger: net charge rate okay, but if you draw from them while charging that rate goes down. How much drawn will make the difference.

vtmaps

Re: Identifying batteries

WillBkool wrote: »

I plan on wiring them in a 24v system with 3 parallel banks. Don't worry I am going to use bus bars for connections.

Welcome to the forum.
You should read and learn about the issues with parallel battery banks. Three parallel strings of AGM batteries will not be stable and you need to be vigilant about monitoring the individual strings for current flow.

for background read: http://forum.solar-electric.com/showthread.php?14674

After reading that, consider that because AGM batteries have lower internal resistance than flooded batteries do, the problems with parallel batteries are worse with AGM.

As the individual cells in a bank age and diverge in their electrical properties, you may find that after charging your batteries, current will flow between one string and another. When one cell finally shorts out, these currents can be dangerous (too much heat). It is recommended to have fuses and switches in each parallel string.

Another way of dealing with the problem is to have a battery selector switch, but individual switches in each string makes for a more flexible system.

btw, I am not saying that three strings of parallel AGM batteries can't or won't work. There are folks who have more than three parallel strings, but it takes a huge amount of effort to monitor it, and then disassemble and rearrange the batteries as needed.

If you find a weak cell in one battery you may want to try a "gentle" equalization on just that one string. If you find two weak batteries, you may want to put them in one string together for that equalization.

--vtMaps

Cariboocoot

Re: Identifying batteries

Three parallel strings on a 24 Volt system correctly installed with equal wire lengths to bus bars will not be a problem.

WillBkool

Re: Identifying batteries

I have equal length wires to go between the batteries and bus bars, but can the wires between the batteries in series be a little longer than those?

I have a cabinet that I was going to put 3 on the bottom and 3 above, but the wires would need to be about 4-6" longer for the series connections. If that's a problem then I could lay the cabinet on its back and keep them all at the same level and use the same length wires between them as well as between the bus bars. I could also probably put 4 on one level and 2 on the other if need be to keep the series wires the same. I got the cabinet at work as well when they were going to throw it away.

mtdoc

Re: Identifying batteries

WillBkool wrote: »

I have equal length wires to go between the batteries and bus bars, but can the wires between the batteries in series be a little longer than those?

Not a problem as long as the lengths are the same for each string of batteries.

H2SO4_guy

Re: Identifying batteries

I have used 'Diverted' AGM batteries for years with generally very good results. I use 14.2 volts to charge them per 12 volt string, so in your case 28.4 volts is where I would set the controller. If they are in use, depending on how much they are discharged, I set absorb for 2 hours and float at 13.6 (27.2 per 24 volt string) but if they are basically in float status and not used, then 30 minutes absorb and float them at 13.5 volts.

Free is great and you can even make money on these too when you go to trade them in or sell them outright. I'd get all you can if that is an option.

The 15 amp charger should be fine, you could even get a higher amperage unit, just find out before purchasing what the charging voltage is and if it is adjustable.

Let us know, and good find!

Skip

WillBkool

Re: Identifying batteries

I appreciate all the answers, one last question about batteries for now. I think that I need to put a fuse in each string, but will that affect the length of the cables? I plan on putting the fuses on the positive side of each string going to the positive bus. Will the length of the fuse and holder need to be added to the length of the cable? Or can I just use 1 foot wires and not worry about the length of the fuses and holders?

Cariboocoot

Re: Identifying batteries

Per battery string use all the same fuses/holders and then the lengths still equalize. Nice reason to use the Blue Sea post terminal fuses.

BB.

Re: Identifying batteries

The idea is to keep the total wire length+gauge the same... I.e., you can have a longer negative lead on one bank and a longer positive lead on the other bank to get to the common battery bus points. The total cable length being equal between strings is the goal.

-Bill

WillBkool

Re: Identifying batteries

Cariboocoot, those things are awesome, never saw or noticed those before. I think those are exactly what I need. I plan on using Blue Sea 2126 bus bars, but I think these fuse holders should be attached to the battery, or should they be attached to the bus bar?

Ok BB, I could put one on a string's positive side and one on a string's negative side, but since I have 3 strings, what to do about the third string? The only way I can think of balancing the lengths is to put one on both sides of each battery string, which is kind of redundant from a fuse standpoint, but will make equal lengths.

Cariboocoot

Re: Identifying batteries

Those Blue Sea fuse holders are meant to go right on the battery terminal. You'd have one on each battery string's positive.

The thing about the wires is ... say you have three strings of two batteries each, so each string has a negative cable, an interconnection cable, and a positive cable: A + B + C

But they do not have to all have equal 'A', 'B', and 'C' wires. One string could be 1 + 2 + 3, the second 3 + 2 + 1, and the third 2 + 3 + 1 if that is what is necessary to get them to fit. But in the end the three wires in each battery string add up to the same length and therefor (hopefully) the same resistance. The idea is to make the battery strings' resistance as even as possible between the two points where they connect in common.

inetdog

Re: Identifying batteries

Cariboocoot wrote: »

The idea is to make the battery strings' resistance as even as possible between the two points where they connect in common.

And the more connections there are along the way, the more important it is to keep all connections clean and tight to minimize the voltage drops there. The wire resistance is not the only thing that can vary from string to string.
The best way to test your connections is to use a sensitive voltmeter between the two sides while the connection is carrying current. Low-ohm-range ohmmeters are very specialized and expensive, and the ohms range on your multimeter is not capable of the job.

Cariboocoot

Re: Identifying batteries

inetdog wrote: »

And the more connections there are along the way, the more important it is to keep all connections clean and tight to minimize the voltage drops there. The wire resistance is not the only thing that can vary from string to string.
The best way to test your connections is to use a sensitive voltmeter between the two sides while the connection is carrying current. Low-ohm-range ohmmeters are very specialized and expensive, and the ohms range on your multimeter is not capable of the job.

Yup. We used to call it measuring Voltage potential. In essence this is how a battery monitor works on a shunt.

inetdog

Re: Identifying batteries

Cariboocoot wrote: »

Yup. We used to call it measuring Voltage potential. In essence this is how a battery monitor works on a shunt.

Which reminds me that in addition to keeping all of the contributions to the string resistance as low as possible, you can do a separate check by measuring the voltage from the far - battery post to the far + battery post on each string. If those values are unequal, then either you are getting an unequal current flow because of battery problems or you are getting unequal voltages at the batteries with the same applied voltage at the CC because of different resistances. Both should be investigated if large.

Cariboocoot

Re: Identifying batteries

Yes, and you can further diagnose it by leaving either the negative or positive lead in place and moving the other to the respective spots on each string to see where the difference is coming from.

Er, yes. It starts to get complicated at that point (this from a man who spent years measuring Voltage differences at dozens of points on hundreds of circuit boards until he was nearly blind from it).