Xoliul
1 µW
- Joined
- Feb 4, 2019
- Messages
- 1
Hi,
I just registered here as it feels like the right place to ask, there seems to be a real DIY attitude here and plenty of people wh know their stuff.
My situation:
I have a self-built RV (van) with a (mismatched) lead acid battery bank (200ah), a Victron BlueSolar MPPT 75/15 and a decent 120w solar panel, and a Cyrix Ct smart relay separating the alternator. The lead-acid batteries are now dead due to my own mismanagement/treatment (old, way too strong charger used often).
I want to switch to Lithium and do it right, but on the cheap. I could replace the batteries for about 250-300 euro, but have come across someone selling Winston 100Ah LFP cells from an EV experiment, at 360 euro for 4 cells, saving me nearly 200 from new. That seems worth the risk for second-hand cells, as they were not used very long and were hooked up to an expensive BMS (Emus). I've put down a small deposit since he ahs a lot of demand for them and it seems like a good opportunity.
I understand I will need a BMS and charge solution. I'm pretty sure the Victron MPPT supports charging LiFePo4, so no change but a reconfigure is needed there. As my van would draw 40A or so max (direct to a 500w inverter), and the MPPT Load limits the rest of the house to 10A, I'm under the impression I don't need big expensive solutions for a BMS.
This is where I need advice:
I'm considering a cheap AliExpress BMS around 50 euro, something like this or this. I'd prefer a system with display/logging possibilities, as I think proper monitoring is key. I also think it would be best to go for separate charging and load rails?
Is this stupid, are these things a scam and is a decent BMS at least 200 euro? Or is this stuff good enough for my application?
I really want to keep alternator charging (not enough sun here often), but I understand I need to at least limit alternator current to the battery, and be able to switch it off.
I'm considering a decent DC-DC Lithum charger from the RC world to put between Alternator and BMS charge rail, they can be configurable to LFP often, and I believe this would limit current and switch off when the battery is charged. I'm less certain about this and can find very little info about people attempting this. Would this work together with my BMS choice? Some chargers support charging without balancing (the BMS could handle this), or is that a stupid thing to do? I'd have an ignition-switched relay feed the charger's DC-in, as to not drain the vehicle batteries.
Both of these options would put me under 500 euro for the whole system including battery cells. That seem very good and almost too good to be true, so I'm expecting to be told I'm very wrong...
I hope I can be enlightened a bit here, I've spent many nights googling but have not become much wiser, other than the fact that spending 5000 euro on a full Victron system is the safer and easier choice. I might have to sell the van to afford that option however
TL;DR
Are cheap 50-euro smart BMS's from Aliexpress worth it for a simple 4S LFP setup in an RV?
Can an RC-hobby DC-DC LFP charger be used between vehicle Alternator and BMS charge input, reliably?
I just registered here as it feels like the right place to ask, there seems to be a real DIY attitude here and plenty of people wh know their stuff.
My situation:
I have a self-built RV (van) with a (mismatched) lead acid battery bank (200ah), a Victron BlueSolar MPPT 75/15 and a decent 120w solar panel, and a Cyrix Ct smart relay separating the alternator. The lead-acid batteries are now dead due to my own mismanagement/treatment (old, way too strong charger used often).
I want to switch to Lithium and do it right, but on the cheap. I could replace the batteries for about 250-300 euro, but have come across someone selling Winston 100Ah LFP cells from an EV experiment, at 360 euro for 4 cells, saving me nearly 200 from new. That seems worth the risk for second-hand cells, as they were not used very long and were hooked up to an expensive BMS (Emus). I've put down a small deposit since he ahs a lot of demand for them and it seems like a good opportunity.
I understand I will need a BMS and charge solution. I'm pretty sure the Victron MPPT supports charging LiFePo4, so no change but a reconfigure is needed there. As my van would draw 40A or so max (direct to a 500w inverter), and the MPPT Load limits the rest of the house to 10A, I'm under the impression I don't need big expensive solutions for a BMS.
This is where I need advice:
I'm considering a cheap AliExpress BMS around 50 euro, something like this or this. I'd prefer a system with display/logging possibilities, as I think proper monitoring is key. I also think it would be best to go for separate charging and load rails?
Is this stupid, are these things a scam and is a decent BMS at least 200 euro? Or is this stuff good enough for my application?
I really want to keep alternator charging (not enough sun here often), but I understand I need to at least limit alternator current to the battery, and be able to switch it off.
I'm considering a decent DC-DC Lithum charger from the RC world to put between Alternator and BMS charge rail, they can be configurable to LFP often, and I believe this would limit current and switch off when the battery is charged. I'm less certain about this and can find very little info about people attempting this. Would this work together with my BMS choice? Some chargers support charging without balancing (the BMS could handle this), or is that a stupid thing to do? I'd have an ignition-switched relay feed the charger's DC-in, as to not drain the vehicle batteries.
Both of these options would put me under 500 euro for the whole system including battery cells. That seem very good and almost too good to be true, so I'm expecting to be told I'm very wrong...
I hope I can be enlightened a bit here, I've spent many nights googling but have not become much wiser, other than the fact that spending 5000 euro on a full Victron system is the safer and easier choice. I might have to sell the van to afford that option however
TL;DR
Are cheap 50-euro smart BMS's from Aliexpress worth it for a simple 4S LFP setup in an RV?
Can an RC-hobby DC-DC LFP charger be used between vehicle Alternator and BMS charge input, reliably?