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First PB Deep-Cycle pack advice appreciated.
#1
Hey all,
I know 18650's are the preffered storage (I'm still harvesting these) but have sufficient Lead-Acid deepcycle batteries (from unused UPS replacement packs) to at least utilise the 100W (18v) panel and crappy cheap 10a PWM controller I have sitting idle.

So for now I've got:
4x RBC55 18AH (12v)
12x RBC43 5.5AH (12v)

Any suggestions on how to string the batteries together (still have all the 100amp fuses and Anderson connectors etc from the UPS) or what else I need to get up and running?

Initally I'll be looking at powering the shed, mainly to charge up tools or RC batteries as and when needed; pretty sure I've got an invertor somewhere...

Cheers
---
Tony
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#2
You didn't say what voltage you were designing for. Just because the solar panel is 18V, doesn't mean that's your design build as charge controllers can boost that up to 48V nominal.

I would match 3x 5.5Ah with each 1x 18Ah.
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#3
(09-27-2019, 11:52 AM)Korishan Wrote: You didn't say what voltage you were designing for. Just because the solar panel is 18V, doesn't mean that's your design build as charge controllers can boost that up to 48V nominal.

I would match 3x 5.5Ah with each 1x 18Ah.

Thanks for answering so quickly.

I'm thinking 24v as I'll be able to charge my RC stuff straight off the grid without a step-down.

So assumably (6x5.5ah and 2x18ah) in Series?
Would I need a way of balancing these (same way I would with Li-lithium packs)?
---
Tony
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#4
Sounds like something similar to my setup for RC charging.

I am using lithium battries which are charged off solar in a "24 volts" configuration.  In the photo I have a series cable which allows me to quickly change to "48 volts" I can use if I need to charge at higher rates.  Most of the time I leave it at 24 for convenience and because my solar setup wont charge at the 48v pack voltage.

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#5
>So assumably (6x5.5ah and 2x18ah) in Series?
Do you mean
1) 6x5.5ah in parallel (12v@33ah) and then 2x18ah in parallel (12v@36ah) and then put these in series for 24v@34.5ah and then do a 2nd one in parallel for 24v@69ah?
Or
2) parallize 6x5.5ah with 2x18ah for a total of 12v@69ah and then put those in series for 24v@69

I would go with #2. As far as BMS... I don't have experience with LA BMS except to observe that in #1 you would have 4 'cells' to manage (with BMS) and in #2 you would have 2 'cells' to manage.
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#6
(09-27-2019, 05:33 PM)OffGridInTheCity Wrote: I would go with #2.    As far as BMS...  I don't have experience with LA BMS except to observe that in #1 you would have 4 'cells' to manage (with BMS) and in #2 you would have 2 'cells' to manage.

You don't really need a BMS for LA. 

I would however connect everything in parallel first for a couple days and allow everything to equalize before making the series connections.

Most commercial products like a APC UPS wont have any "cell" monitoring.  They only look at total pack voltage and perhaps apply a low voltage disconnect at most.
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#7
If you go 24V, then I'd go with 2x 18Ah with 6x 5.5Ah all in parallel, then series the 2 sets. This will give you equal capacities in both parallel packs. A total of ~69Ah.

The other option is to have 2 strings. Pair up your 2 18Ah batteries for 1 string, then parallel 6x 5.5Ah *2 to give you the second string. Then parallel both strings together.

Either option will work. First option is electrically 1 battery bank. The second option is electrically 2 battery banks and allows for disconnection of one bank while the other one is still connected. This means 0 interruption in your power delivery as long as you aren't consuming too much current at the time.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
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#8
(09-27-2019, 06:13 PM)Korishan Wrote: If you go 24V, then I'd go with 2x 18Ah with 6x 5.5Ah all in parallel, then series the 2 sets. This will give you equal capacities in both parallel packs. A total of ~69Ah.

The other option is to have 2 strings. Pair up your 2 18Ah batteries for 1 string, then parallel 6x 5.5Ah *2 to give you the second string. Then parallel both strings together.

Either option will work. First option is electrically 1 battery bank. The second option is electrically 2 battery banks and allows for disconnection of one bank while the other one is still connected. This means 0 interruption in your power delivery as long as you aren't consuming too much current at the time.

Awesome, thanks for your help - I'll take some photos assuming the British weather holds out over the weekend for the install.
---
Tony
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#9
Realised I'd probably need 2 panels to charge a 24v bank with the crappy Chinese/Generic PWM... Will setup as 12V for now to get the cells charged up,.

Options for a MPPT?
---
Tony
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#10
(09-28-2019, 06:00 PM)amerrigan Wrote: Realised I'd probably need 2 panels to charge a 24v bank with the crappy Chinese/Generic PWM... Will setup as 12V for now to get the cells charged up,.

Options for a MPPT?

MOST solar charge controllers are BUCK controller, meaning the PV input has to be higher than the battery voltage.

They are a handful of BOOST controllers... less common, but they do exist.  The most popular crappy Chinese one is the MPT-7210A, which I have mixed feelings about.  It's not that great, but it does work... I actually use it more as a DC-DC boost charger in my car to charge a 24v pack from a 12v alternator.

Companies like Genasun makes awesome compact charge controllers, and they have a boost models as well.  I have a few of their controllers and they are great. 

If you can add more panels, I would do that and use a buck controller as its a lot more common.  I know ur going cheap, but those Victron SmartSolar units are great.
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