Charge level and settings

[jacr]

Hi there,

I'm new to the forum and fairly new to the world of solar so would appreciate advice from you seasoned veterans...

We are off-grid with the following set up:
6 LG390N2T panels wired in 2 strings of 3.
8 S6-L16-HC batteries in series for 48V.
MS4448PAE
ME-PT-100
MS-PAE

Charging settings (which are adjusted from BTS):
Battery type: custom
Absorb volts: 60
Float: 54
EQ: 62.8
EQ time done: 4h

Absorb Done: 2h
Max Charge Rate: 100%
Final Charge Stage: Multi

I have a generator giving 240V 25A.

After equalization charge I checked the gravities of a few random cells. Most were about 1.230 (uncorrected @ 8C accord to BTS), which I think is undercharged.

Batteries are <6 mo old but I didn't get a generator until recently so they may have been undercharged for a while.

Are these settings about right?
They are all the same as listed on the Rolls website except the EQ voltage. Their range is 62.4-63.6. Should I push mine up?

Thanks in advance,
James

[Bala]

What is BTS?

From the chart in the link below you are well down, run your generator until you get them back up. Short story for SG you are looking for them to be all the same, check them all.

http://support.rollsbattery.com/support/solutions/articles/208145-specific-gravity-temperature-correction

[jacr]

Thanks for your reply.

Battery Temperature Sensor

The Rolls manual says to use settings for 25C if BTS installed - the red column in attachment - and the BTS adjusts as required.

This is is what happens. I can see on the remote display that the target voltage is adjusted.

E9D8E460-764A-4FBF-92C8-FEE57746C925.png

[Bala]

The problem is not likely your charge settings but your usage and sun to recharge.

Have a read of the stickies in the off grid section. Are you killing your batteries and any others that look of interest to you.

For now, my advice is to use the SG chart from Rolls that I linked, and run your generator for as long as it takes until you get that SG to where it should be.

SG is your real time, any time, way to tell your SOC and you also looking for even SG for all cells.

[jacr]

So at 8C I’m looking to get all cells to 1.275. Should that be on every cycle or just on EQ? So do I increase bulk voltage target? Or EQ voltage?
Thanks again

[Bala]

Basically with lead acid batteries to achieve longest life you want limit there DOD as much as possible and return them to full charge asap, that is every cycle.

Equalize is to restore balance to the cells. If you monitor and understand your SG, rather than a monthly equalize for a set time you equalize when needed and for as long as needed.

Your charge controller settings are not necessarily the problem with your batteries being down on charge. It will not matter what they are set at if you use to much from them and do not have enough sun hrs to replace it.

As I suggested, for the moment if it were me, I would have the generator on until I get the SG back up across all cells, it may take 4 hrs it may take 24hrs.

While that is happening you can work on how much you use and what your system can put back in.

[Mike90250]

To save fuel. run the generator in morning start at 5am, and by the time 10am arrives, the sun should be able to take over the final hours of charging.

[jacr]

As I suggested, for the moment if it were me, I would have the generator on until I get the SG back up across all cells, it may take 4 hrs it may take 24hrs.

So should I just use the existing settings and keep the generator running? It will go through the regular bulk and absorb and then float for as long as necessary while I check SG. Or should I extend the absorb charge time and keep monitoring SG?

Thanks again

[Mike90250]

If you are able to extend the absorb times AND monitor the cell temps, and add water to the cells at the end of the day, that's good . Add water after the charge cycle, sometimes a full cell, when it warms up from charging, and all the bubbles, will overflow the cap and make a mess. But you don't want the plates to be exposed - air ruins the exposed plate area.
And an extended absorb will get the electrolyte stirred up really well from all the gassing, which is important to do before measuring the SG.

Many more batteries are ruined from undercharge & the resulting sulfation, than from slight overcharge and forgetting the water replacement

[Bala]

So should I just use the existing settings and keep the generator running? It will go through the regular bulk and absorb and then float for as long as necessary while I check SG. Or should I extend the absorb charge time and keep monitoring SG?

Thanks again

As Mike said you can extend absorb. For solar timed absorb is really just a default setting. Absorb should take the batteries to 95% or so before switching to float.

If it were me I would run at absorb Voltage until Sg is up then Equalize if needed, ensuring you monitor water and temp. Leaving batteries undercharged will be more harmful than extended absorb.

I fitted new batteries last year and a Morningstar Tristar regulator. It has a default 4 hr absorb but in the manual says if there is load it will stay in absorb longer. It rarely goes into float unlike my older regs that would switch to float at the preset time.

Mike also made a good point about generator use. If you have enough sun to hold absorb then you dont need to use the genset.

[jacr]

Well my first attempt failed. I extended the absorb time but after 8.5h of charging on the generator my wife told me to turn it off so our daughter could go to sleep. At that point the cells were around 1.250. The days are fairly short here in Canada at present so didn't get much solar input yesterday. I'll try again once we have a sunny day in the forecast.

[Bala]

Well you have not failed, 1.25 is better than 1.23 and it would have been lower of you had not run the generator all day.

You will always need to run the generator at some point so need to either sound proof it or get a silenced unit, there are many options depending on what you already have and your budget.

Your generator charging my not be big enough. When you are charging you are still using power so the generator and charger need to be big enough to charge the batteries in a reasonable time as well as run the house power. Every situation is different but I have a 10kva diesel generator enclosed in a purpose built silenced room. It is about 30m from the house. I can hear it when it is running but it is not annoying. It is large enough to run everything at once. I can charge batteries, wash and dry clothes, heat water and run the house. I never let the batteries get to far down so a charge run will generally only be a 2 hrs or so.

For long battery life you are going to need to have a look at how much power you use and when, you may be able to change some habits or may need to upgrade some system components. Otherwise more generator run time.

[jacr]

Thanks Bala.

We are in a temporary situation - living in an RV with a small annex. I wanted to live on the land for a year or so before I decide on house location and design.

I could move the generator a bit further away and build an enclosure. We don't have funds for a bigger generator at this stage. The one we have is a Yamaha EF7200DE (6kW).

We aren't using much power right now (which has me a bit concerned for the future). We have a few LED lights, laptops, and a fridge. We are hauling water by hand, heat is from a wood stove. I suspect the fridge is the biggest energy user (the plan was to use our 2-way fridge in the RV but that has broken). The battery voltage drops a couple of volts overnight (50-51 to 48-49) when only the fridge is plugged in.

[chrisski]

I think expecting a perfect Temp adjusted 1.277 may be asking too much, not impossible, just not worth the last bit of effort.

I have a temp corrected 1.270, 96%, after a good day of charging. Talking to a guy with Trojan batteries similar to mine, he sees 1.265-1.270. To get to 1.277 takes an entire day of charging and an equalization.

My Fla batteries are set up to 12 volts. 2s2p. My batteries are capable of taking in 60 amps or 13% of the 20 hour rate but my generator and converter only deliver 15 charging amps. My panels deliver 45 amps for about 3 hours and another three hits I can get 30 amps.

[Bala]

I moved onto our property when it was just a sugar cane paddock and started off living in a tent. Eventually built a house etc. It can be a long road.

You have bought good quality gear so either something is not working correctly, you have just fallen well behind in your charging from solar or that fridge is a real power hog.

If you dont have them get yourself a Kilowatt meter and a AC/DC mutlimeter/clamp meter. For reference I looked on Amazon Canada, Killowatt meter $20 and DC Clamp Meter $50. You an get them as most hardware stores or automotive stores for the DC meter. Both are inexpensive and whilst they dont have calibrated accuracy can get you good data quickly. If your not sure what to get I can post some links.

The inverter charger has a 60A dc capacity and your generator should run that so I dont understand why your batteries did not come up better after 8hrs of charging. With those two meters you can take some readings and see what is happening.

The generator is air cooled so you cant just put it in a box. You need cooling air in and out ans intake air in and exhaust out. Putting it behind a sheet of ply or a car can take some edge off.