My supplier told me once, on some of their sealed maintenance free batteries, if you have doubts, pull off the stickers on top ... there are caps underneath them to open and refill. 

If you don't want, keep them sealed. 

1 hour ago, The Terrible Triplett said:

My supplier told me once, on some of their sealed maintenance free batteries, if you have doubts, pull off the stickers on top ... there are caps underneath them to open and refill. 

If you don't want, keep them sealed. 

Yes I have done this on old Excis sealed flooded cell batteries, and it did marginally extend the life of the battery - I have also tried it on an AGM before I understood the technology and completely destroyed what was still a serviceable battery (fortunately only 1 in a bank of 4).

AGM do not have liquid electrolyte, so filling them with distilled water will be the end of them.

On 02/05/2017 at 5:31 PM, plonkster said:

TTT will say different, but I'd go with the Omnis with the proviso that the cycle number I googled is correct. Doesn't @Chris Hobson have Omnipowers?

Nah sorry boys CB Solar batteries. The  Omnipower specs are better than my batteries.

So i look the decision to buy the 240omnipowers. Now i have more questions, on the battery it states that the minimum current should be 30 amps, i have 4 batteries in 24v configuration so my minimum amps should then be 60amps 24v. My axpert gives max 30 amps. Will this affect my batteries negative? Also the system goes into float charge very quikly? Could that be because i don have enough amps? These batteries were 20k so would really not like to mess them up

Unfortunately the OPR240's are better suited to the Axpert 5K (or 3K-48v plus) which can both deliver the recommended 40amps charge (with enough panels or grid assisted charge if too few panels).

You would have been OK with 1 battery string getting 30amps, but I think 15amps per string will not be a good match for the OPR240's. If your budget can do it I would recommend getting the one of the systems suggested above and trade/sell your Axpert 3k 24v. Your batteries are always going to be the major expense component and it will be worth the change to protect them in the long run.

10 hours ago, pilotfish said:

Unfortunately the OPR240's are better suited to the Axpert 5K (or 3K-48v plus) which can both deliver the recommended 40amps charge (with enough panels or grid assisted charge if too few panels).

You would have been OK with 1 battery string getting 30amps, but I think 15amps per string will not be a good match for the OPR240's. If your budget can do it I would recommend getting the one of the systems suggested above and trade/sell your Axpert 3k 24v. Your batteries are always going to be the major expense component and it will be worth the change to protect them in the long run.

Would it not be better to just ad a 30amp charger to the system?

Give us more detail on your full setup before we can provide a useful answer - is the system off-grid or grid-assisted.

If you have 2x 24v strings of OPR240's you will require minimum 24v/60amp charger (30amps per string), preferably an 80amp charger (40amps per string). This will probably cost more than the Axpert 5kA, but have a look around and see what you come up with.

Also where is the charger power source coming from? If solar then you will need about 3kW of panel (2kW for charging and 1kW overhead to supply the load).

 

I am off grid with no eskom option. I have 500watts of panels, axpert mks. I think it is around 2000watts. I have 4 omnipower 240 batteries. 8kw generator for backup. I am only on the farm over weekends so the panels must charge the batteries when i am not there and when i am there i top them up with the gennie for a hour or two.

This topic is interesting. You see, if the batteries are fairly close to full, you're not going to need 30 amps to do the job, that much is uncontroversial. From that it follows that at shallow discharge depths you will do just fine with 30 amps, but that begs the question: Why did you buy such a big bank then? Okay, you did it so you can discharge them on the weekend and they can take the whole week to recharge? I don't see why it wouldn't work, but then, I suppose that if you take too long to fully recharge a battery, sulphation starts to set in. On the other hand, they will only be cycled very infrequently, so you might not notice. This all feels like just way too much handwaving, and batteries are too expensive to rely on a hand-waving argument. So I'm thinking that if it was me I'd probably look at adding an external charge controller and a few more panels.

I thought such a big bank because if i only do 75% DOD on 4 batteries and not 50% DOD on 2 batteries the life expectancy of the bank will by much better. I should get 10 years put of the battery bank

13 minutes ago, Leondk said:

only do 75% DOD

I'm inclined to think that if you employ the generator with a faster charger for times when you did a deep discharge, and PV for the rest of the times, you can probably get away with it... though of course, don't take my word for it... I'd feel much easier about it if there wasn't parallel strings involved.

1 hour ago, plonkster said:

I'm inclined to think that if you employ the generator with a faster charger for times when you did a deep discharge, and PV for the rest of the times, you can probably get away with it... though of course, don't take my word for it... I'd feel much easier about it if there wasn't parallel strings involved.

I was thinking along similar lines. If you use the gennie early morning and give your required 30A per string and then monitor and switch to PV as it tails off.

3 minutes ago, Chris Hobson said:

I was thinking along similar lines. If you use the gennie early morning and give your required 30A per string and then monitor and switch to PV as it tails off.

Indeed, I remember from a Victron training day this was advised for deep discharges. When the power comes back, complete the bulk phase using grid power (generator in this case) and then use PV to finish the job. There is some sound science behind it too:  Below 80% SoC a lead acid battery is fairly efficient and it charges very efficiently, but as it approaches full charge (from 85% onwards) the efficiency tapers off significantly. If you're going to spend money, spend it on the part with the good efficiency, and use the free power you get from the sun to do the inefficient bit.

This will require some proper discipline from yourself. Get a BMV. At the very least.

20 minutes ago, Chris Hobson said:

If you use the gennie early morning and give your required 30A per string and then monitor and switch to PV as it tails off.

The problem is that to get 30amp per string you will require a 60amp charger, the MKS 2k24v has a 20amp AC charger, 30amp max including PV - so the most you will get into each string is 10 to 15 amps, even with the generator.

Given the low usage you may get away with it to a certain degree, but I still think that it would be advisable to upgrade to the MKS 5k which has an 60 amp AC charger and a 60 amp PV charger - that way you can comfortably use your generator to give an initial charge of 30 amps (into a single string at 48v), and you can add PV panels in future up to 3kw instead of being limited to the 600w of the current inverter.

So my best plan is to take 2 batteries out of the system for now, buy a 48v axpert and then put the 2 batteries back. What is your opinion?

4 minutes ago, Leondk said:

So my best plan is to take 2 batteries out of the system for now, buy a 48v axpert and then put the 2 batteries back. What is your opinion?

That sound sensible

5 minutes ago, Leondk said:

What is your opinion?

That would be a viable solution for now.

What I would do is start by leaving all 4 on charge for the week while you are away so that they are fully charged when you arrive on the weekend.

Then when you arrive disconnect one string and leave the other string connected through the weekend and the whole following week to fully recharge (leaving the disconnected string also fully charged).

On arrival the next weekend swap over for a week etc.

That way your batteries will be used equally until you are able to install the MKS-5K.

Note that it is important that the string used on the weekend is left on charge through the week, don't leave your batteries in a discharged state.

Guys, thank you all for contributing in this thread, I for one have learned a lot about batteries and charge cycles (and in general about Trojans, Axperts, Isuzus and Fords) and this is what makes this Forum great.

My battery bank is made up of 200Ah Vision AGM batteries, 4 in series. We are completely off-grid now for a year. I do have a Honda inverter genny for stand-by use when there is no sun for a day or so. In the morning before the solar charging kicks in, the batteries are standing at 51Vdc. I presume this is acceptable?

The 5kVA Axpert (not the plus one) does the bulk charge at 56V, and then tapers down to 54V. Does that sound right for the AGM batteries? I have not fiddled with any settings on it since I installed it.

My thinking at the beginning was to buy the cheapest batteries of reasonable quality, with the intent to replace it after 3 years with something better. I paid R16k for the 4, on a PCLink special last year. I anticipated that the price of batteries and especially Li-Ion options will come down. 

Bought a Trojan watering kit for a client, who decided he does not need it anymore.

Seeing as I have a 24v bank, I never bothered. Last week I decided to install it, even thought it is a 48v kit, I do have a lot of spare parts now.

Where the arrow is, connect the rubber bulb hand pump, pump until there is no more water movement in the pipe, and you are done. Takes less than 2 min, no wastage and no mess.

It is, for me, as close to no-maintenance batteries as can be.

Notes:
I doubled on the pipes between the batteries, just because.
Wooden battery box are on wheels. Got tired moving them around at times. Obviously, as Murphy dictates, since they are on wheels, I have never had to move them.
The black cables between the batteries, are flexible busbar 250amp cables. Got tired of crimping.

 

O, FWIW, every 4 weeks the one Victron controller (there are 2 on the bank from 2 different arrays - long story) that auto-equalizes.

And I make sure that the batteries are fully charged at least once every 7 days, although I read they can go once a month.

The are about 3-4 years old now, not 100% sure, if I replace them one day, it will be with J200RE which are 12v 200ah Trojans. Less batteries, less cables and I may decided to double up to 400ah.

Why? Less connections on a 12v 400ah bank than on a 6v 450ah bank. 50ah less but seeing as I seldom go below SOC of 80%, it makes no difference.

Trojans are supposed to go for 4000 cycles, so Lithium's and all that I will wait until it becomes the norm to buy electric cars, then their price will have dropped a LOT (so they say) and the tech will have jumped forward in leaps and bounds.

Until then I will stick with my Granny Wagon (280TD LE Isuzu) and Trojan batteries.