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Small Cabin Forum / Off-Grid Living / Charging solar batteries from generator
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bobrok
Member
# Posted: 7 Oct 2015 17:01 - Edited by: bobrok
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This has been discussed before, but every situation is different and I wanted to see if I could pick your brains about my setup.

I have 12 very old 4v. batteries wired series/parallel on my system. They recharge OK if in ample sunlight and still give decent service, but now that fall is here and the sun angle is lower I am relying more on my EU2000i so I don't constantly drag these batteries down.

I am planning to upgrade my system, but in the meanwhile how can I best take advantage of the generator to recharge these batteries without damaging them?

I wouldn't think a direct connection between the generator and the batteries is advisable without some sort of line protection.

I do have a Schumacher float charger. I use this at home to maintain my deep cycle battery which I use on the water pump at camp. Could I use this at camp with alligator clips and directly charge my solar batteries?

I'm trying to keep this question simple but if I've overlooked any info I'd certainly appreciate hearing.

This forum has been so helpful to me with my recent propane piping project. Here's hoping I don't wear out my welcome!
battery rack
battery rack
battery specs
battery specs


MtnDon
Member
# Posted: 7 Oct 2015 17:10
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Twelve 4 volt... wired for what system volts? 12, 24.....

MtnDon
Member
# Posted: 7 Oct 2015 17:13 - Edited by: MtnDon
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I see they are rated at 125 AH. Is there mfg info on the recommended charge rate? Listed as "xx" amps or as a function of capacity. "C"... like C/10....

bobrok
Member
# Posted: 7 Oct 2015 17:31
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Quoting: MtnDon
Twelve 4 volt... wired for what system volts? 12, 24.....


Std 12 volt, and running the standard 12 volt el-cheapo cigarette lighter plug-type inverter. Wasteful

Quoting: MtnDon
I see they are rated at 125 AH. Is there mfg info on the recommended charge rate? Listed as "xx" amps or as a function of capacity. "C"... like C/10....


These were here when I bought the place and they date back to 1998/1999! They still work!
They were, ummm, borrowed, from an AT&T cell phone tower when the phone company did an upgrade (seriously, they weren't stolen, but the guy had some connections). I have no info on them unless I turn them over and find more stickers!!!

Soooo, I have nothing on this to share.

I am counting my blessings as far as longevity on these babies and I just don't want to screw 'em up, if you know what I mean! Read: I will be back and picking brains when I get to redoing my system.

creeky
Member
# Posted: 7 Oct 2015 17:58
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whaddya think Mtn Don?

use the Schumacher float charger running off the genny? keep the batteries as a 12v set up. as you're using a 12v charger I assume. and probably best to charge the two sets of 3 one set at a time.

neat batteries.

MtnDon
Member
# Posted: 7 Oct 2015 18:28
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Sold under the Lucent name; they make all sorts od cell tower equipment. Batteries made by Deka. Valve regulated battery which is basically an AGM type. That means being careful about maximum charge rate is important.

Google found info sheets with everything but the cgarge rate! ???
One data sheet here
Another

MtnDon
Member
# Posted: 7 Oct 2015 18:33
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Here's more info right from Lucent, 1998.....

There's charge info in that but I can't seem to find an amp rate.... in a rush as we have a dinner date.......


In General, AGM batteries can be charged fairly fast. But too fast can spell death by bubbles forming and not going away. So it would be nice to know the max charge rate recommended.

A lower rate of recharge just wastes gasoline, that's why I was/am after the recommendation.

More later..........

bobrok
Member
# Posted: 7 Oct 2015 19:14
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Quoting: creeky
you're using a 12v charger I assume


My Schumacher is supposed to read 6v. or 12 v. and adjust accordingly, AFAIK. I will check the manual on this.

Quoting: creeky
best to charge the two sets of 3 one set at a time.


Maybe hard to see on the photos but I have buss bar connections. I'd think that would be an awful PITA to disassemble and reassemble every time I want to charge up.

Quoting: creeky
neat batteries


yeah, not too bad for 20-year old batteries, IMO!

Quoting: MtnDon
AGM batteries can be charged fairly fast. But too fast can spell death by bubbles forming and not going away


...and my 20-year old 50 watt panel could explain the slow charge rate and longevity, eh?

pizzadude
Member
# Posted: 8 Oct 2015 01:51 - Edited by: pizzadude
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Quoting: creeky
neat batteries.

Boy, I'll say.
Lucky buzzard bobrok

creeky
Member
# Posted: 8 Oct 2015 09:15
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Quoting: creeky
one set at a time.


bobrok. to me it looks like the three batteries are tied together into one set. the two sets are then linked with longer cables.

you could charge one set (of 3) at a time. but it's probably not necessary.

what is the voltage right now? if it's really low you would want to give it a bit on a very low amperage. 2 amp trickle for example. if it's not bad, you could charge at 10 amps. Or, assuming the charger has the capacity, 15 amps. I don't know, does the Schumaker have set points or is it all auto?

My marine charger can be set to 2, 10 or 15. That's why I ask.

good luck.

bobrok
Member
# Posted: 8 Oct 2015 10:23 - Edited by: bobrok
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You are correct in how the batteries are harnessed, but I'd still have to make disconnections from each gang every time I want to charge, plus my charging times will triple since I have three sets.

I don't even own a proper meter with which to take voltage measurements. I have an el-cheapo HF meter that says not to use it on large batteries or it might blow up, so I've avoided that scenario. A good meter is on my wish list once I start on this project.

The Schumacher is an SEM1562A auto 6v./12v. and does not have any external settings.

My panel and charge controller are as ancient as my batteries and charge in full direct sun only at 2.25 - 3 amps maximum. This slow charge rate could be why everything has lasted so long. My guess.

As an aside, I used to keep my original Schumacher (same model) plugged into a power receptacle when I was using the generator for power tools. I'd leave it plugged in permanently to charge up my deep cycle battery for the water pump.

It blew up after a while. I guess it couldn't take the constant surges and off/on cycles of the generator. I no longer do this.
controller
controller
amp meter
amp meter


creeky
Member
# Posted: 8 Oct 2015 12:27
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ya. it's not worth disconnecting the parallel strings. You should have a bus for the four strings tho. to keep the loads/charging distributed between the parallel strings better. do you?

I missed that you had 4 sets of 3. The pic only showed two sets. heh heh heh.

it would be interesting to do a capacity test on those batteries. I mean 4 parallel strings at 125 amps means you may have 500 amps of storage there. somehow I'm thinking reality is a little lower.

one tech note tho: with batteries a slow charge may be necessary to get them warmed up. but a high amp / voltage charge breaks down sulphites and in theory should result in a longer lasting battery pack.

all this goes out the window with your system as you are basically just floating the batteries. not using them in any sense of 100 amps of discharge per day, day after day, year after year.

You should have, at 20% dod, 1200 watts of power to use daily. How much do you use?

I mean 5 hrs at 3 amps solar charging means you're putting back 200 watts a day.

I'd suspect that's why your batteries appear to have lasted that 15 or so years. even if capacity has fallen to 50% you're still not using even 20% dod.

and you should be able to charge at 30 amps no problem. with batteries that old tho. I'd sure start lower.

bobrok
Member
# Posted: 8 Oct 2015 17:11 - Edited by: bobrok
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Yeah, I have a dozen 4v. units. The second set is behind the first. They weigh a ton!

How does one do a capacity test? That'd be very telling as to how good or bad these batteries are.

Quoting: creeky
You should have, at 20% dod, 1200 watts of power to use daily. How much do you use?


We tend to go up and stay for a week or week and a half. The batteries are fully topped off when we arrive.
Typically we use two 8 watt LEDs on at the same time, occasionally a 3rd light for brief periods. Perhaps 2-3 hours of TV, but not every night (small screen early model digital TV, think it uses 14 watts???)

If the sun is out next day we are topped off again by evening.
If its consistently overcast we can usually expect 3 days of battery life before the dreaded red light glows on the controller, more if we don't use the TV.

Its not like we're power starved, but I was thinking, if I'm switching to generator due to low battery, can I take advantage of it and top them off?

So do you think I can alligator-clip my Schumaker to the main posts? I mean, remove the inverter clips and attach clips from the generator?

bobrok
Member
# Posted: 8 Oct 2015 17:32
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Quoting: MtnDon
There's charge info in that but I can't seem to find an amp rate...In General, AGM batteries can be charged fairly fast. But too fast can spell death by bubbles forming and not going away. So it would be nice to know the max charge rate recommended.


How do the cell phone companies recharge their battery banks in emergencies?
I just saw a Verizon commercial on TV a day or two ago saying that they are installing generators at select cell sites for emergency power (and to recharge batteries during outages, I dunno) but I thought that was interesting.

MtnDon
Member
# Posted: 8 Oct 2015 18:43
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The remote tower near us has a propane fueled generator that auto starts after "xx" condition occurs, according to the tech I saw up there once. He told me it can run for days in winter when the roads are impassable.

bobrok
Member
# Posted: 10 Oct 2015 10:51
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I don't mean to belabor this thread, but I'm reading the manual for my charger URL and it says that the output current rating at 12v. is 1.5A.

My solar panel charges at no more than 3.25A at maximum and usually hovers at a midpoint around the 1.5A - 2A range before dropping off to roughly .25A at maintenance.

Since the outputs are so similar shouldn't I be able to use the charger?

The only concern I have is that while charging at any output the PV controller will constantly cycle to "0" output for a second before resuming charge. I figure that's some sort of protection built in.

Would it work to run my charger thru the PV controller (probably disconnecting the panel while doing this)?

Or am I playing with trouble?

Tnx.

creeky
Member
# Posted: 10 Oct 2015 12:18
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run the charger full on. that thing is not the best for your use. (ps. that's classic creeky understatement )

with those batteries and that size. you are wwwwwaaaaayyyyy over batteried and under charging.

you could put a 50 amp charge into those guys. well. when they were new. you should probably beg or borrow a better charger.

bobrok
Member
# Posted: 10 Oct 2015 12:34
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Thanks, creeky.

I'm trying to get a handle on upgrading my system. I was supposed to meet with a tech but that fell through. I'm probably not a big enough customer to make it worthwhile for her.

So I'm picking brains here (specifically yours and a few others) in order to see how to go about an upgrade.

With what your telling me perhaps I should invest in a new higher output panel along with a new charge controller as my 1st step. Maybe my batteries are still good enough for my needs.

creeky
Member
# Posted: 10 Oct 2015 13:15
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those batts are way past the due date. from what you've said about how you're using them and the time/charge factors ... it sounds like you're at 50% <or much less> capacity.

and yer past the best before date on the whole system.

sorry to say. but hey. all that lead is worth quite a bit.

if you want to try to get more out of the system i would definitely get a more powerful panel on 'em. and a better controller (which is any controller). and if you're going to genny charge. a stronger charger. 15 to 30 amp range.

but you're kind of in that ugly spot. if you spend money eeking out the final value ... are you going to get your money back vs just starting anew.

kind of like a car. are you at that point where the repairs cost more than just buying a new (or in my case, new to me) vehicle?

the best first start is putting a 15 to 30 amp charge with a decent reliable charger on 'em and see what happens. i would trickle charge to warm them up and then hit 'em.

can you borrow a good deep cycle charger? 10 amp minimum. 50 amp max.

bobrok
Member
# Posted: 10 Oct 2015 16:25
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Unlike when I just ripped out and redid my propane lines, I'm kind of hoping that solar can be done piecemeal, or doesn't it work this way?

I thought if I upgraded my panel and controller now then I could maybe get a new inverter and then new batteries at another time.

The quality components I've read about here are kind of pricey, especially the batteries.

Maybe not such a good idea to do this piecemeal?

creeky
Member
# Posted: 11 Oct 2015 11:19
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Ya. you can do it piecemeal. as you know I'm a big fan of piecemeal.

i'm just thinking that if those batteries are really 15-20 years old. i wouldn't count on them.

so really. you have to ask yourself what do you want to do.

upgrade your CC (I really like the new victrons and they're pretty cheap for what you get).
add a new panel. see what happens.

powermax makes some good offgrid chargers that are cheap. Maybe find a deep cycle boat charger on sale?
15 amps minimum? 30 amps? don't want to run that genny forever.

and you can't go wrong with the new CC/panel idea. that's money spent that pays you back for decades.

bobrok
Member
# Posted: 11 Oct 2015 13:24
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Quoting: creeky
and you can't go wrong with the new CC/panel idea. that's money spent that pays you back for decades


Ahhhh, them's the magic words I was hoping to hear.
I don't think I'm going to pursue charging batteries off the generator, given their status.

There's been much discussion here about panels, controllers, inverters, etc.
Time to go back, re-read and digest all that discussion.

And thanks for the recommendation on the CC. Appreciate all the help.

MtnDon
Member
# Posted: 11 Oct 2015 14:54
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If it was I, I would look at it this way...

You have one big advantage that most people starting out do not have. You now know how much energy you use in a 24 hour day. You also have an idea of how much more energy you might like to have, what new stuff you might like to run. So before spending anything work up a list of what equipment you would need to continue.

Size of new battery pack.... then how many watts of PV to recharge that fully each day.... then the CC that can handle that much PV... then any other changes such as inverters, etc.

bobrok
Member
# Posted: 11 Oct 2015 16:30
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Quoting: MtnDon
You now know how much energy you use in a 24 hour day. You also have an idea of how much more energy you might like to have, what new stuff you might like to run.


Correct. I think that'll be the easy part.

What I'd really like to accomplish is running my RV 12v. demand water pump off the system so I won't have to lug a dedicated battery back and forth, as well as having a transfer switch between solar and generator.

I really need to hook up with a consultant who can put eyes on my place and figure something out that will work.

I think I've used up a lot of forum time already with my anal retentive posting.
I'll be looking into this and (of course) posting my outcome.

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