Getting to "Full" with Not Enough Solar
More on camping tactics etc to try to get batts full while off-grid and not enough solar per PT's "rules"
(PT says you need at least 60w solar per 100AH of battery to "equalize" that day sometime before dark, starting from 80% SOC in the morning and still run your 12v stuff per normal daily usage. He says 100w per 100AH is preferred.)
You can achieve those ratios by having more solar for your existing battery bank or keep that much solar and reduce the AH of the bank.
What PT is not saying, is what happens if you can get a kick -start in the morning with your gen/charger and then let solar do the rest. AHA!
EG, (not typical, but exemplary) today I managed to almost get to "full" with only 130w of solar and at least 715AH of battery. That is more like 0.2 vs 0.6 minimum per PT rules. But he is right in that I had to go out of my way to get that done.
First my 130w is on a swivel contraption so it is able to get maybe 90AH per day in- haul. This would be more like 210w solar lying flat.
So let's call my set- up half what PT wants at 0.3 vs 0.6. How did it do?
Yesterday, I was down 160AH with no hope of ever getting back with my measly amount of solar. So I ran the gen/charger for two hours and then went to normal life on solar, ending with max AH on Trimetric of minus 20AH before starting to use a bunch. Then in the morning it was minus 43AH by the time I was done everything (in which I restrained usage by using a stove top pot to heat water instead of the electric kettle etc), and could leave the 12v alone except for the standing 0.8 draw from fridge etc.
So the task was to get to "full" today using the available solar (perfect blue sky day all day) making up that -43AH before supper and the usual draws got started.
By 12:30 pm, solar reached absorption voltage where it stays for two hours as this LS2024 controller has it. By then we are at -14AH, so we have made up 29AH in about five hours.
1:30pm, we are at -6.9AH but SG is only at 1.270 on the two pairs of 6s and 1.250 on the pair of 12s (vs 12.80/85 6s and 1.255 on the beat-up 12s) so keep going, not using the 12v in rig. Go swimming at the lake.
2:07 we are back! (quick dunk) controller has dropped to Float (over the two hours) 13.6v, 2.1a, -0.06AH on Trimetric. BUT SG is still 1.270 on the 6s but has risen to 1.255 on the 12s which is "full" for them.
Next step is to go "panel direct" and try to get the 6s up in SG, and who cares about the 12s? So do that. Now see 14.6v and 7.1a. BUT now that's as high as voltage will go instead of up to 15v or beyond.
Is it like a 120v trickle charger, which has a voltage limit it can get the batts to depending on its own oomph? No idea. Anyway after a while at 14.6, with amps tapering (Isc of panel still at 8.2 or more, pointed, so the low amps is strictly due to battery acceptance reduction at that high SOC at that voltage)
So time to get back to real life, SG has not improved from 1.270 on the 6s and 1.255 on the 12s. Back to controller and now back on Float with 13.6v, + 0.08a. and + 9.95AH. So reset AH to zero and carry on as normal.
So we didn't get the SG of the 6s quite there, but the 12s are up ok.
It looks like we could just do without the controller at all and still stay under 15v before supper knocks voltage down anyway.
The easy solution is left to the student, how much solar you really need for what you are doing, or else just go with PT's rules. Who knows, they might just work!
(PT says you need at least 60w solar per 100AH of battery to "equalize" that day sometime before dark, starting from 80% SOC in the morning and still run your 12v stuff per normal daily usage. He says 100w per 100AH is preferred.)
You can achieve those ratios by having more solar for your existing battery bank or keep that much solar and reduce the AH of the bank.
What PT is not saying, is what happens if you can get a kick -start in the morning with your gen/charger and then let solar do the rest. AHA!
EG, (not typical, but exemplary) today I managed to almost get to "full" with only 130w of solar and at least 715AH of battery. That is more like 0.2 vs 0.6 minimum per PT rules. But he is right in that I had to go out of my way to get that done.
First my 130w is on a swivel contraption so it is able to get maybe 90AH per day in- haul. This would be more like 210w solar lying flat.
So let's call my set- up half what PT wants at 0.3 vs 0.6. How did it do?
Yesterday, I was down 160AH with no hope of ever getting back with my measly amount of solar. So I ran the gen/charger for two hours and then went to normal life on solar, ending with max AH on Trimetric of minus 20AH before starting to use a bunch. Then in the morning it was minus 43AH by the time I was done everything (in which I restrained usage by using a stove top pot to heat water instead of the electric kettle etc), and could leave the 12v alone except for the standing 0.8 draw from fridge etc.
So the task was to get to "full" today using the available solar (perfect blue sky day all day) making up that -43AH before supper and the usual draws got started.
By 12:30 pm, solar reached absorption voltage where it stays for two hours as this LS2024 controller has it. By then we are at -14AH, so we have made up 29AH in about five hours.
1:30pm, we are at -6.9AH but SG is only at 1.270 on the two pairs of 6s and 1.250 on the pair of 12s (vs 12.80/85 6s and 1.255 on the beat-up 12s) so keep going, not using the 12v in rig. Go swimming at the lake.
2:07 we are back! (quick dunk) controller has dropped to Float (over the two hours) 13.6v, 2.1a, -0.06AH on Trimetric. BUT SG is still 1.270 on the 6s but has risen to 1.255 on the 12s which is "full" for them.
Next step is to go "panel direct" and try to get the 6s up in SG, and who cares about the 12s? So do that. Now see 14.6v and 7.1a. BUT now that's as high as voltage will go instead of up to 15v or beyond.
Is it like a 120v trickle charger, which has a voltage limit it can get the batts to depending on its own oomph? No idea. Anyway after a while at 14.6, with amps tapering (Isc of panel still at 8.2 or more, pointed, so the low amps is strictly due to battery acceptance reduction at that high SOC at that voltage)
So time to get back to real life, SG has not improved from 1.270 on the 6s and 1.255 on the 12s. Back to controller and now back on Float with 13.6v, + 0.08a. and + 9.95AH. So reset AH to zero and carry on as normal.
So we didn't get the SG of the 6s quite there, but the 12s are up ok.
It looks like we could just do without the controller at all and still stay under 15v before supper knocks voltage down anyway.
The easy solution is left to the student, how much solar you really need for what you are doing, or else just go with PT's rules. Who knows, they might just work!
