diy solar

diy solar

A little hesitant

B

BobbyP

New Member
Joined
Mar 27, 2022
Messages
43
Any suggestions would be appreciated.
A 100amp MPPT Charge Controller rated to Max Voc 96v, Vmp max 72v, 2600w max, has some new buddies ie. 4 - 275 w,
Panels rated Voc 39v, Vmp 32.1v, Imp 8.5 amps. How should these panels be connected to gather the most energy and still remain within the limits of the Charge controller?? Thanks friends
BobbyP
 
Make 2 sets of 2 in series (39×2=78v at 8.5amps) then parallel those 2 sets. (8.5a×2=17amps at 78v)
 
BobbyP said:
Any suggestions would be appreciated.
A 100amp MPPT Charge Controller rated to Max Voc 96v, Vmp max 72v, 2600w max, has some new buddies ie. 4 - 275 w,
Panels rated Voc 39v, Vmp 32.1v, Imp 8.5 amps. How should these panels be connected to gather the most energy and still remain within the limits of the Charge controller?? Thanks friends
BobbyP
Click to expand...
2s2p.......no other way, if you dont want sparks to fly
 
Berseker said:
2s2p.......no other way, if you dont want sparks to fly
Click to expand...
Thanks Berseker, short and straight to the point. How would you wire 8 - 6v 225 amh batteries for this panel set up? My inverter is a 24v pure sine wave. Do you recommend breakers or in line fuses?
I've had some experience with small 12v rigs and thought I'd try this upgrade. And I agree, I don't want sparks or me frying up either. I do, appreciate your time and help.
 
Might be good to fully charge all the 6V batteries first, so they are balanced when connected in series.

I would do 4s2p. After making two 24v strings, either connect to inverter through fuses (or breaker) using matched length cables,
or connect in parallel with short cables, then connect diagonally opposite corners to inverter with two cables.
Goal is exactly matched cable length for each 24V string.

Was that "agm" batteries? Or something else?

Short circuit current should be relatively modest, maybe 5000A per string, 10,000A all together for AGM.
You want a fuse or breaker with 10,000A interrupting capability at 30V or higher. (5000AIC if separate fuse for each string.)

For amperage I suggest (if one for the whole bank) at least:

(inverter wattage) / (full load efficiency maybe 85%) / (20V low battery) x (1.12 ripple factor) x (1.25 margin to avoid nuisance trip)

Midnight Solar has 175A and 250A breakers, which provides a disconnect.
 
BobbyP said:
Thanks Berseker, short and straight to the point. How would you wire 8 - 6v 225 amh batteries for this panel set up? My inverter is a 24v pure sine wave. Do you recommend breakers or in line fuses?
I've had some experience with small 12v rigs and thought I'd try this upgrade. And I agree, I don't want sparks or me frying up either. I do, appreciate your time and help.
Click to expand...
For the batteries, 4s2p. I prefer suitably application sized breakers.

rmaddy said:
4P would work too but 2S2P would be better. 4S is no bueno.
Click to expand...
4p for mppt CC?, I wouldnt even think about it. Just like the nose, its always there, but the brain disregards seeing it, except only when you look down or think about it?
 
Hedges said:
Might be good to fully charge all the 6V batteries first, so they are balanced when connected in series.

I would do 4s2p. After making two 24v strings, either connect to inverter through fuses (or breaker) using matched length cables,
or connect in parallel with short cables, then connect diagonally opposite corners to inverter with two cables.
Goal is exactly matched cable length for each 24V string.

Was that "agm" batteries? Or something else?

Short circuit current should be relatively modest, maybe 5000A per string, 10,000A all together for AGM.
You want a fuse or breaker with 10,000A interrupting capability at 30V or higher. (5000AIC if separate fuse for each string.)

For amperage I suggest (if one for the whole bank) at least:

(inverter wattage) / (full load efficiency maybe 85%) / (20V low battery) x (1.12 ripple factor) x (1.25 margin to avoid nuisance trip)

Midnight Solar has 175A and 250A breakers, which provides a disconnect.
Click to expand...
The batteries are 6v lead acid (golf cart).
All things considered where is optimum placement for fuse/breaker?
 
FLA wet-cell?
In that case, need periodic watering. Check cell (or battery) voltage periodically, equalize as needed. That will cause outgassing, so arrange in a manner to keep corrosive fumes away from electronics.

Because they can be equalized, easier to get in balance while assembled as a pack, but still best to start out with all identically charged full.

Not sure the exact short-circuit current, but assuming 5000A per string should be safe, with one 10kA rated OCP device.
Fuse/breaker should be located close enough to pack that wire from battery to it can't contact anything that would make an unprotected short.

FLA prefers a particular charge rate, probably about 0.12C, whatever manual says. Ideally you can configure your electronics so it delivers exactly that to the battery, while providing additional current when needed by inverter. Some equipment can, but of course a stand-alone SCC wouldn't know where its current goes.
Make sure your PV and loads always permit full charge and absorption cycle.

If MPPT SCC has no knowledge of anything happening in system except its output, then best you can do is configure for no more than maximum charge current and over-panel so sufficient charging can be attained most days. Then control loads, depth of discharge and time of day, so full recharge can happen.
 
Hedges said:
FLA wet-cell?
In that case, need periodic watering. Check cell (or battery) voltage periodically, equalize as needed. That will cause outgassing, so arrange in a manner to keep corrosive fumes away from electronics.

Because they can be equalized, easier to get in balance while assembled as a pack, but still best to start out with all identically charged full.

Not sure the exact short-circuit current, but assuming 5000A per string should be safe, with one 10kA rated OCP device.
Fuse/breaker should be located close enough to pack that wire from battery to it can't contact anything that would make an unprotected short.

FLA prefers a particular charge rate, probably about 0.12C, whatever manual says. Ideally you can configure your electronics so it delivers exactly that to the battery, while providing additional current when needed by inverter. Some equipment can, but of course a stand-alone SCC wouldn't know where its current goes.
Make sure your PV and loads always permit full charge and absorption cycle.

If MPPT SCC has no knowledge of anything happening in system except its output, then best you can do is configure for no more than maximum charge current and over-panel so sufficient charging can be attained most days. Then control loads, depth of discharge and time of day, so full recharge can happen.
Click to expand...
Thanks Hedges... Valuable info duly noted, esp. periodic H2O checks.
 
BobbyP said:
Thanks Hedges... Valuable info duly noted, esp. periodic H2O checks.
Click to expand...

I forgot to say check specific gravity, with a hygrometer. I think that is the gold standard for cell SoC, and it lets you see individual cells, whereas most 6V batteries don't have access to measure voltage of individual cells. Wear old clothes, because they will be after a while.

You may be able to get catalytic recombining caps to minimize watering.
You can get a hose manifold with float valves per cell, so one squeeze bulb waters all, as NVS suggests.
 
Hedges said:
I forgot to say check specific gravity, with a hygrometer. I think that is the gold standard for cell SoC, and it lets you see individual cells, whereas most 6V batteries don't have access to measure voltage of individual cells. Wear old clothes, because they will be after a while.

You may be able to get catalytic recombining caps to minimize watering.
You can get a hose manifold with float valves per cell, so one squeeze bulb waters all, as NVS suggests.
Click to expand...
I looked into NVS's suggestion and now with your additional info, (hydrometer) I've got to ask, how often should this procedure take place? Is it recognizable in loss of storage/power or is there a "tell tale" that one becomes aware of before problems occur in the bank? Thank you so much guys, in advance.
 
I don't actually have lots of experience in the care and feeding of batteries.
After some time maintaining it, you find how fast the cells diverge.
Objective is to keep them at similar, fully charged state because they would deteriorate if not fully charged.
 
Hedges said:
I don't actually have lots of experience in the care and feeding of batteries.
After some time maintaining it, you find how fast the cells diverge.
Objective is to keep them at similar, fully charged state because they would deteriorate if not fully charged.
Click to expand...
Hedges said:
I don't actually have lots of experience in the care and feeding of batteries.
After some time maintaining it, you find how fast the cells diverge.
Objective is to keep them at similar, fully charged state because they would deteriorate if not fully charged.
Click to expand...
I've done some research and found a hydrometer, the multi cell fill gizmo and a "desulfator" on YouTube, worth a looksee. Thanks for your time.
 
BobbyP said:
I looked into NVS's suggestion and now with your additional info, (hydrometer) I've got to ask, how often should this procedure take place? Is it recognizable in loss of storage/power or is there a "tell tale" that one becomes aware of before problems occur in the bank? Thank you so much guys, in advance.
Click to expand...
The hygrometer angle to check SG, should be a one off thing, as SG shouldn't change much, once its correct from the get go...you can however reconfirm every 2 yrs or so.

charge the battery till full, then check each cell one after the other, they must not all the the same, but should be in the green area/band.

what works for me if some cells are a lil low on SG, is to add some quantity of diluted acid to the particular cells, in addition to distilled water....takes experience to get it right., but if you don't want to bother with all this ....--the recommended procedure is to drain all the electrolyte from the battery and refill with fresh electrolyte of the correct SG
 
BobbyP said:
how often should this procedure take place?
Click to expand...
Starting out: look at them weekly for a few months. If no major diff and/or loss of fluid levels go to monthly. Once you get a “feel” for your situation you’ll know what to expect. FWIW I lose the most fluid level in winter…
BobbyP said:
Is it recognizable in loss of storage/power or is there a "tell tale" that one becomes aware of before problems occur in the bank?
Click to expand...
If you find or experience a reduction in charging ability or power output that is a telltale of issues. But you don’t use that as the maintenance indicator- you physically check them regularly.
Hedges said:
After some time maintaining it, you find how fast the cells diverge
Click to expand...
Exactly
 
You must log in or register to reply here.

Similar threads

D
Adding PV to my first Victron SCC 150 / 45 -- Please check my calculations
Replies
3
Views
285
Dinobot248
D
D
Voltage booster?
Replies
4
Views
341
dnuttsr
D
K
Help with Low Amps
Replies
7
Views
390
kfergrocks
K
C
Best Solar Configuration to Charge a 48v Battery Bank?
Replies
6
Views
393
Cloroxbottle
C
wildbillpdx
Adding More Panels to My Setup (EG4 6000ex)
Replies
14
Views
425
wildbillpdx
wildbillpdx
Back
Top