Hey ya'll,
So I'm helping a friend build a budget solar system for his camper van. It will be using a 2000wh 36v li-ion (NMC) battery bank.
Why 36v??? The best cheap batteries I could find at the moment for this sort of thing are 5s EV batteries, so stringing them into a 10s makes a perfect 36v battery (and only requires one BMS).
However, he wants to be able to charge with the alternator. Through my own tinkering I've found that the cheap MPPT boost modules can safely accept input from a wall charger (at lower voltage than the batteries) or other sources-- I built a pedal powered charger using one. I've been using the MingHe kind but I ordered one of these:
If it doesn't work the same I'll order him a MingHe one (just have to wait for shipping from China).
I haven't tested with an alternator, but I think it should be fine as long as he keeps it disconnected when starting the vehicle and current is limited at 20a.
However, the amount of power these MPPT units can pull is largely dependent on the voltage difference between input and output. I worry that the jump from 13-14v up to 30-42v will not yield much. SO I was thinking adding another boost module inline before the boost MPPT to bump input voltage up to 24-30v might help ease the MPPTs struggles. I got one of these:
I see someone else tried something similar for a 12v system, and it worked (for a week!). Hopefully the boost module I got is higher quality (and actually has working current limiting). Probably not though...
I'm just wondering if anyone has any alternate suggestions, or additions to this (add some diodes for extra protection? a 30a current limiter in case the other stuff doesn't do its job?)? As far as I know they don't make anything designed to charge 36v li-ion NMC off an alternator, so I cant just get a commercial product. If this was a 24v system I'd just get a ISDT Q8 hobby charger to use as the intermediary, but those only work up to 34v (and I cant find a hobby charger with high amps made for anything more than that). 36v AC>DC e-bike chargers are typically limited to 2a, so getting a 12v inverter and plugging that in would be worthless.
I'll be happy if I can get the alternator to charge 150-250w-- that's all I feel safe pulling to not strain the alternator anyway, and the MPPT is limited to 300w too. There is a separate MPPT charge controller for solar so he'll be able to charge with both alternator and solar at once-- I only expect the alternator to be supplemental or useful in a pinch.
So I'm helping a friend build a budget solar system for his camper van. It will be using a 2000wh 36v li-ion (NMC) battery bank.
Why 36v??? The best cheap batteries I could find at the moment for this sort of thing are 5s EV batteries, so stringing them into a 10s makes a perfect 36v battery (and only requires one BMS).
However, he wants to be able to charge with the alternator. Through my own tinkering I've found that the cheap MPPT boost modules can safely accept input from a wall charger (at lower voltage than the batteries) or other sources-- I built a pedal powered charger using one. I've been using the MingHe kind but I ordered one of these:
LED MPPT Boost Solar Panel Battery Regulator Charge Controller 12V-50V CTK300-II | eBay
Find many great new & used options and get the best deals for LED MPPT Boost Solar Panel Battery Regulator Charge Controller 12V-50V CTK300-II at the best online prices at eBay! Free shipping for many products!
www.ebay.com
I haven't tested with an alternator, but I think it should be fine as long as he keeps it disconnected when starting the vehicle and current is limited at 20a.
However, the amount of power these MPPT units can pull is largely dependent on the voltage difference between input and output. I worry that the jump from 13-14v up to 30-42v will not yield much. SO I was thinking adding another boost module inline before the boost MPPT to bump input voltage up to 24-30v might help ease the MPPTs struggles. I got one of these:
1500W 30A DC-DC Boost Converter Step-up Power Supply Module Out 12~90V In 10~60V | eBay
Find many great new & used options and get the best deals for 1500W 30A DC-DC Boost Converter Step-up Power Supply Module Out 12~90V In 10~60V at the best online prices at eBay! Free shipping for many products!
www.ebay.com
I see someone else tried something similar for a 12v system, and it worked (for a week!). Hopefully the boost module I got is higher quality (and actually has working current limiting). Probably not though...
Budget charge from alternator addition to solar
Hi dear community! Thanks administration for creating this forum. Hopefully it will be helpful. Currently my Ford Transit 2016 camper van conversion uses 350W solar only to charge 12V 200AH LiFePO4 battery bank. We have no propane, so it's all electric conversion with some massive loads like...
diysolarforum.com
I'm just wondering if anyone has any alternate suggestions, or additions to this (add some diodes for extra protection? a 30a current limiter in case the other stuff doesn't do its job?)? As far as I know they don't make anything designed to charge 36v li-ion NMC off an alternator, so I cant just get a commercial product. If this was a 24v system I'd just get a ISDT Q8 hobby charger to use as the intermediary, but those only work up to 34v (and I cant find a hobby charger with high amps made for anything more than that). 36v AC>DC e-bike chargers are typically limited to 2a, so getting a 12v inverter and plugging that in would be worthless.
I'll be happy if I can get the alternator to charge 150-250w-- that's all I feel safe pulling to not strain the alternator anyway, and the MPPT is limited to 300w too. There is a separate MPPT charge controller for solar so he'll be able to charge with both alternator and solar at once-- I only expect the alternator to be supplemental or useful in a pinch.
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