This seems to be the Achilles-heel of the EB240 that i can tell? You want to put as much of the 500W Max charge (from solar) into the unit as possible if using it as a regular power supply, but are limited by the total VOC limit of 60v.
I’ve got my eye on these 200W panels from ‘enjoy solar’ as per this link:
“Puissance nominale (Pmax) : 200 W – max. Tension (Vmp) : 17,6 V. Courant (Imp) : 11,36 A - Tension à vide (Voc) : 20,8 V - Courant de court-circuit (Isc) : 12,05 A - Max. Tension du système : 600 VDC - Température de fonctionnement : : de -40 °C à 80 °C - Dimensions : 1420 x 710 x 2 mm - Poids : 3,63 kg”
So two of those in series should work fine, but what about three? the VOC would be just over the EB240’s 60V limit at 62.4V, but would they just not function or would it be within a limit range that could work?
I’m keeping in mind that all solar panels don’t deliver the full W rating (around 70-80% in best case use) and over-paneling is one way to ensure you get as much into your battery as possible, but the limit is then VOC, which is quite low on the EB240.
So would three of those panels work going on the stats for the EB240 and the panels themselves?
Thanks in advance, as this is all new to me and i’m trying to work out what to spend my hard earned pennies on! ;)
Unfortunately you cannot put three of these panels in series. Don’t forget as well that cold weather can actually increase the Voc.
If you really want to maximize your solar input with those panels, then get 4 of them, and connect two sets of two in series, and parallel the two sets together. You’ll have 800 watts of solar available, the Voc will be at 41.6, the Vmp would be 35.2 volts, and the max current would be a theoretical 22.7 amps (note: I do not know the max current for the EB240). The EB240 will limit the solar input to 500 watts (by limiting the input current) during maximum solar conditions, but still deliver good power during non-optimum conditions.
Thanks for your advice hnymann, this is the info given for the EB240:
“It must meet: 1)Open Circuit Voltage(OCV):16-60V/Max.10A, Max.500W (DC7907 to MC4 Charging cable is included) 2)MC4 Connector Tips: make sure the total OCV(open circuit voltage) is no more than 60V if you connect several solar panels in series!!”
I had read that the amps are less an issue and that will be modulated to take just the 10A needed?
When you say you can’t do three of the panels is this just a general rule for series connections to powerbanks like the EB240? You need to keep the number even etc?
And the parallel connection actually reduces the VOC (for 4 panels) from what would be 83.2V in series (alone) to half at the 41.6V value you gave? I think this would be ideal with the extra Watts from over-paneling giving the best re-charge times for the EB240. So do the amps look like being an issue to you with the new info i found on the EB240?
Yes, the amps are not an issue and the MPPT controller will only take the max 10 amps it is designed for. Panels in series add the voltage and the current remains the same (assuming same panels), and when in parallel the voltage remains the same and the current is added. So the three panels in series would have too high a Voc. With two in series the voltage is the 35.2 volts, and with current maxed at 10 amps the max input wattage is going to be 350 watts (approximately). Adding a second set of two panels in parallel gives a theoretical 22.7 amps, but that is still subject to the 10 amp limit, so the max wattage in is still 350 watts. So, there is not as much an advantage in doing this as one would hope. However, the advantage that it would give is that the 350 watts will be available for a longer period of time on sunny days, and will be attained much more easily in cloudy conditions.
The only reason for not doing three panels in series is strictly due to the voltage input limit. For my AC300, for example, I’m using two sets of three series 250 watt panels that will be paralleled together (3S2P), so six panels in the array, and doing that for each of the MPPT controllers (12 panels total).
Paralleling doesn’t reduce the voltage, rather think of it as just not adding the voltage of the panels.
One other note based on what I have seen on my panels, and if you do this over-paneling I would love to know if you get the same. It is possible that once the MPPT charge controller starts limiting the input current that you will see the voltage increase above the Vmp value and heads towards the Voc level. In that case you could see as much as 416 watts maximum coming in (41.6 volts at the 10 amp max).
Awesome info hnymann, and thanks for taking the time to point me in the right direction
You will be amused to know i had done ‘the math’ for the 4 panels we are talking about above based on your 2xseries in parallel and came to the optimistic (and wrong as you point out above) conclusion i’d see about 540 Watts in that would be limited to the max 500W for the EB240! I had not taken into account the 10 amp limit aspect and had just factored in a baseline -30% to the panels rated 200W. Doh! This is all actually more complex than it seems at first glance for sure, and thanks again for your time and knowledge sharing.
Actually, even though the EB240 was originally rated up to 60V for solar input and the port on the unit also says so, Bluetti Support has since indicated these are good up to 68 volts, and their product page now lists 16-68 volts as the accepted range, too. So three of the panels referenced above should work in relatively warm weather, but may still go over when it’s colder.
Ah yes i found this on the main ‘Features’ section of the product page, under ‘AC & Solar Charging’:
“1)This Power Generator Can be Recharged from the Sun with Solar Panel (Not Include, Input Voltage must be 16V～68V)”
This is the only place that mentions the 68V limit for using solar, it still mentions 60V limit elsewhere for solar info (on both the english language and ‘euro’ sites).
So with that new info (68V VOC max over 60V VOC max) i have a new set of sums that give this for a potential 3 panels in series (for the 200W ones mentioned above):
Total VOC would be 62.4 Volts. (maybe an issue in winter, what happens if over VOC limit?)
Vmp would be 52.8V (3x17.6 V) which with the 10 amp limit would allow upto
528W charge in, but the EB240 unit would limit that to it’s 500W max in. And probably it would be under that as the total 600W in (in series for the 3xpanels) is more likely to be around 450W taking into account general solar panel efficiency vs the ‘on the box’ stated Watt rating etc.
So with the adjusted VOC at 68V max for the EB240, maybe the three panels in series would give the best recharge speed?
Yes, if the 3S option does not work i would get another panel and do a 2S2P system also.
Well i ordered the EB240 (getting hard to find over here!) and the D050S DC charging unit (to give the option of topping up via my vehicles lighter socket output) and next month will look for best panels i can find.
Just curious. I have the exact same setup with bougerv panels and a eb240. Mine seems to be stuck at 365 input. Limiting factor i would assume is also amps. When you say no issues are you getting the full 500w in? Thanks.
Not a solar or computer person-just trying to get EB240 and panels set up No MC4 to DC7909 cable that I can find in box. Can anyone advise me were to obtain one that will handle enough charge power to run 4 (maybe 6 panels) and not fry the system. I have 2 PV120 but need more solar. What I have found on Amazon is using 14AWG or 12 AWG(only1) wire, most specs advised 10AWG for the 500Watt max for EB240. Need to keep a fridge powered for medicine if no power. I will be getting 2 or more of them. One for now and backups. thank you