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Author Topic: second battery bank and stuff  (Read 3523 times)
eabadger
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« Reply #15 on: May 09, 2017, 08:04:44 PM »

work in progress, 3rd mppt along is the faulty one.
had fantastic day today, blue sky and windy, need to get second victron online as 1st one complains when running house and imersion, collecting the ashp for dhw next week when in in uk.

steve


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Scruff
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« Reply #16 on: May 09, 2017, 08:36:27 PM »

ok, other than i use Ethernet the same.
but what do you do when you save settings? disconnect solar input?


I isolate the pv input to begin with because they go bang if you disconnect the battery before the array. In order to reset the controller I need to periodically disconnect the battery input.

Manual?

but what do you do when you save settings? disconnect solar input?

Return to Custom Setpoint Summary Window and hit Program TriStar, reset tristar, reconnect PV.

Did they let you keep the broken one?


1 good battery + 1 bad battery = 2 bad batteries. The good one discharges into the bad one that just loses charge. So effective lower capacity and holding voltage, higher self discharge, decreased efficiency and increased cycling. Like most things battery related it's a slow death.  


« Last Edit: May 09, 2017, 10:27:33 PM by Scruff » Logged
camillitech
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« Reply #17 on: May 09, 2017, 11:24:08 PM »

I know everyone says two banks in parallel will kill one... but why ?

unless one bank is knackered to start with and losing power while standing.... (so would discharge the other bank)  then what's the downside of paralleling them both ?

with OPs 1000ah and 650ah, you've got enough capacity that both bank voltages will be identical, you won't pull more from one bank than the other because you'll be pulling such a low C rate - a 5C rate is 8250 amps - almost 100kw




Because one bank usually is knackered (or at least worn out), or else why would you have two? Two banks make no sense in anything other than a 'critical system'. It's like replacing a cell or battery in a good bank, unless the cell/battery is the same as all the others in terms of capacity/spec it will feck them or they will feck it. I have much experience of this having lived 'off grid' since 1985 and looked after many battery banks at work since 2001. If you have two battery banks of the same age and spec then all will be peachy but that is seldom the case. All the posts I see on here and elsewhere are about about dudes like myself who acquire a used bank of unknown provenance or replace their own with a new/better one and then like to get some extra mileage out of their old one.

No matter how clever your charger is it either needs to carefully monitor voltage/current or have some clever algoritham for monitoring SOC. None of these methods will work with batteries of different spec/charecteristics, which is inevitable if the bank is your old one, came with that ole forklift off eBlag or 'the back of a lorry'. Sure you may well be lucky or Irish  ralph, or be able to make one out of milk cartons but in 90% of instances it will end in tears. Trust me, I speak from experience, I can quite catagorically say that I have ruined more batteries than most people  Grin

« Last Edit: May 09, 2017, 11:31:20 PM by camillitech » Logged

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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
jonesy
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« Reply #18 on: May 09, 2017, 11:28:46 PM »

Does this sound right.
The older battery will have a higher impedance.  Charging current will preferentially go to the newer battery due to its lower impedance,  meaning the old  battery will only get a decent current once the newer one is nearly fully charged. You may not even hit float .
The new battery could end up charging the old one if float isn't hit, thus reducing overall efficiency.

You could come up  with a scheme to use all power to charge main, then swap to older battery. Then discharge old battery first, swapping to new one as required.  This would use up the old one getting it to the scrap yard before it let's you down on age.
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camillitech
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« Reply #19 on: May 09, 2017, 11:37:23 PM »

Does this sound right.
The older battery will have a higher impedance.  Charging current will preferentially go to the newer battery due to its lower impedance,  meaning the old  battery will only get a decent current once the newer one is nearly fully charged. You may not even hit float .
The new battery could end up charging the old one if float isn't hit, thus reducing overall efficiency.

You could come up  with a scheme to use all power to charge main, then swap to older battery. Then discharge old battery first, swapping to new one as required.  This would use up the old one getting it to the scrap yard before it let's you down on age.

Yes it does sound right Jonesy but the voltage on the new bank is dragged down by the older bank, result, new bank gets cooked, charger overworked and the old bank is just as bad as it ever was.

You could come up  with a scheme to use all power to charge main, then swap to older battery. Then discharge old battery first, swapping to new one as required.  This would use up the old one getting it to the scrap yard before it let's you down on age.

Exactly what I'm aiming for and also what I think Steve had in mind.

Paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
Scruff
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« Reply #20 on: May 09, 2017, 11:42:53 PM »

Sure you may well be lucky or Irish  ralph,
 Wink


I see no problem with it if: both batteries are isolated have their own chargers and the feckered battery can only feed the good but not vice versa. In which case series diodes are acceptable because something is better than nothing and it's just a contingency.

So voltage/soc controlled contactors and diodes or charge controllers i reckon there's potential.

The simple answer is no, don't make a bi-directional loop unless you want to accelerate the ageing of a good battery for very little gain.
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eabadger
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« Reply #21 on: May 10, 2017, 07:38:22 AM »

i want to use all my pv whenever possible with some redundancy without any chance of killing my main bank, yes the second one i was sort of given, it is ok and whilst i have been moving stuff it has ran our house two days withiut any charge, so maybe ok, but at least proved good as a backup.
we live in the countryside and i go away to work a fair bit, if something breaks whilst i am away i have to talk wife through fixing it, it puts a strain on me going to work, so wanted redundancy.
so plan is now, left multi main house supply, middle multi ashp, but both these can be swapped with a manual changeover switch, to feed main house supply, the righthand side inverter works like multi sort of in as far as it works in ups mode, so left multi is genset connected, its ac2 becomes live, this powers w7 inverter and fires a relay to start it up, the output then feeds through to middle multi, both multi's are charging the good bank, the w7 charges other.
to get the power back out of the old bank i manuly switch on the w7 inverter, which will power the multi as if grid connected, as for solar charging, my soon to be installed 3rd array can be diode split at the controller with possibilty to turn off second feed to smaller bank in the winter.

update on the MPPT, new one on the way, the broken one "please recycle however you see fit".
from what i now understand, do not commit any changes to the software with the solar connected, do not use the reset control feature on msview when solar connected. page 33 on the new manual is not as clear cut as i thought, just says dont disconnect batteries when solar connected, anyway, now we know what not to do, if i were them i would remove reset control from msview or at least put a second knock on the commit button.
if i can fix it, i think the fets gone, i will experiment with wind turbine mode.
morningstar support are very very good, i think they should make this issue more clear, but cant knock the backup.

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1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
Scruff
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« Reply #22 on: May 10, 2017, 08:46:44 AM »

my soon to be installed 3rd array can be diode split at the controller with possibilty to turn off second feed to smaller bank in the winter.

Unless you get wan of them ideal lossless diode jobs like Sterling does I'd stay the damn away from series diodes in charge circuits they're woeful. It'll drop your regulation voltage by 0.7V best case scenario. If you fit it upstream the controller then it's fine or at the very least have the sense wires bybass the diode.

I've run parallel controllers off the same array to isolated batteries before. Works great, self-regulating too.

update on the MPPT, new one on the way, the broken one "please recycle however you see fit".

I'll give you 15+P&P fer it. fingers crossed!  Grin

Open it up and send us some nudey photos  (of the TriStar not yourself) might be salvageable.


from what i now understand, do not commit any changes to the software with the solar connected, do not use the reset control feature on msview when solar connected. page 33 on the new manual is not as clear cut as i thought, just says dont disconnect batteries when solar connected, anyway, now we know what not to do, if i were them i would remove reset control from msview or at least put a second knock on the commit button.

What and stop giving people free replacements? Quiet you!

if i can fix it, i think the fets gone,

Would be my suspicion too.
Overcurrent, smoke.

morningstar support are very very good, i think they should make this issue more clear, but cant knock the backup.


The only tech support I've contacted who haven't first replied with "have you read the manual?"  fight

Mine comes with mechanical protection. I can't fit the RS232 in at the same time as PV inputs.  ralph

« Last Edit: May 10, 2017, 10:03:41 AM by Scruff » Logged
Tinbum
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« Reply #23 on: May 10, 2017, 09:58:22 AM »

I've had one go and repaired it. see https://www.navitron.org.uk/forum/index.php/topic,16171.30.html
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Fionn
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« Reply #24 on: May 10, 2017, 10:56:43 AM »

A DC changeover contactor betweeen each bank and the inverters / chargers might make most sense but it could be hard on the electronics.
As has been said I think checking in the old bank for it's recycling value is the best course of action though.
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Justme
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« Reply #25 on: May 10, 2017, 11:19:03 AM »

IF both banks are in good condition & the same type then you should combine the banks. Even if they are different capacities. When wired correctly they would share the load & charge proportional to their size.

IF one bank it stuffed or a different type then you should not combine them.

The only exception is IF you need to keep mission critical functions at all times.

IE life support or military defense to name two.
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FX80 Solar controller
Victron 12v 3000w 120a
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24 x 2v cells 700amp/h 5C
Total bank 4350 amp/h 5C
eabadger
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« Reply #26 on: May 10, 2017, 07:40:31 PM »

Hello,
if as i have you have dissimilar bank sizes, you will always be limited to smallest capacity one, which will be less than when new and unknown, plus self discharge and greater loss's are a given, not going that route myself, has anyone else who is off grid?

anyway, got it working and worked well, connected the w7 to the second multi, which is connected to the immersion heater, the w7 is off the dodgy (for want of a better word) bank, when w7 powered up the victron sent power through and also charged the main battery bank, i assume very lossy but good way of separating and gives me redundancy.
i hear what is said about redundancy, military/hospital etc, but tell that to my family if i am away for 10 days and they have no power, who do you call in to fix our things?
new mppt is on the way, i will take pics as i open up the popped one, if i get chance before Sunday i will get new parts from rs next week.
when the new mppt arrives i should have got the third array up to charge the dodgy bank and set up the rd1 to control it all.
we did 18kw today in pv which is a first plus we heated all dhw to 64* 250l of it, chuffed.

steve
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1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
eabadger
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« Reply #27 on: May 10, 2017, 07:53:25 PM »

timbum, thanks for heads up, will explore further, the new manual gives a power down and up method, but doesnt mention not clicking reset control on msview until after you click pv disconnect, tech support said you must.
i wonder if on boot it can handle it?
last two i had fail, one possible after reset, one maybe static after storm, i had to send back to dealers who sent out a new one.
anyway whatever new one on way, if i fix old (thanks for offer scruff) i will try as turbine controller mode.

steve
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1600w PV main array at 24v, excide 2v 1000a forklift cells now x 2, 320w PV secondary array at 12v. Enfield 1944 ex RAF 5.6kw diesel genset (now in pieces, big ends gone), Petter AC1 28v diesel charging set at 2.8kw.
1kw wind turbine.
26kw wood stove back boiler to underfloor heating and dhw
Scruff
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« Reply #28 on: May 10, 2017, 08:37:54 PM »

has anyone else who is off grid?


I'm sure Justme probably has.

I did for a while, in the summer the PV could feed the losses in the Autumn I retired the dud and not much changed...'cept I'm sure the remaining battery had suffered for the cause. Ah back in the days of 100% discharge and asymmetric loading. That lead owed me nothing.
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Justme
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« Reply #29 on: May 11, 2017, 07:17:58 PM »

Having a small bat linked to a bigger one will not limit you to the size of the smaller one.

If the cables are sized & wired correctly each bat will supply & receive a charge proportional to its size.

The biggest factor is, are both bats the same type & in good condition.

If they are it will work fine.

If one is duff, why the hell are you wasting energy trying to charge it?



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Navitron solar thermal system
30 x 58mm panel 259L TS
1200watts solar 120vdc
FX80 Solar controller
Victron 12v 3000w 120a
6kva genny
6 x 2v cells 1550amp/h 5C
24 x 2v cells 700amp/h 5C
Total bank 4350 amp/h 5C
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