timholmesjr
New member
Sweet build. What battery combiner are you using?
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- Thread starter CoyoteThistle
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CoyoteThistle
Adventurer
Thanks!
It's the Victron Cyrix Li-ct. It's specifically intended for lithium batteries. It has different connect/disconnect voltages than the normal Cyrix combiners and has a remote input that can disconnect the batteries with a signal from a BMS. I got the 230 amp version only because I couldn't find the 120 amp version in the states.
calicamper
Expedition Leader
Interesting info on the smart alternator circuits. What truck are you running? I wasnt sure if Auto makers were that fancy/advanced yet with the auto stuff. Interesting.
I skipped the fancy battery idea during a big upgrade project on my boat. The alternator and dumb electrics that had to be upgraded were just to big of an expense. So I built a bigger battery box to upsize to two group 31 lead acid beasts.
Whats the rough footprint of your battery? Very curious how this works out for you. Cool stuff!
I skipped the fancy battery idea during a big upgrade project on my boat. The alternator and dumb electrics that had to be upgraded were just to big of an expense. So I built a bigger battery box to upsize to two group 31 lead acid beasts.
Whats the rough footprint of your battery? Very curious how this works out for you. Cool stuff!
CoyoteThistle
Adventurer
Thanks! That's a 100Ah pack. I used CALB cells. The four cells, balance boards and bus bars came to about $600 shipped. That gives me 80Ah being most conservative with a minimum state of charge (SOC) of 20%. Equivalency to lead acid depends on how much capacity you believe is actually usable. Most say 50% minimum SOC for lead acid so I'm equivalent to 160Ah of lead. Some say that since it's hard (slow) to get the last 20% or so of charge in to lead acid, you should expect to only be operating between 50% and ~80% SOC in "real world" conditions - I don't have enough experience to support or refute this. If it's true, I'm equivalent to 250Ah or something. Either way, that's two or three big AGM's so I'm saving a lot of space and weight.
Yeah, it's been a bit back-breaking working in that space but hopefully, once things are up and running I wont spend much more time with my head down there.
2010 Nissan Frontier 4X4. Not sure what other trucks are using these now (pre-2005 Frontier's didn't have any of this I think). Wouldn't be too surprised if most newer 1/2 ton and smaller trucks aren't using something like this since it seems to be tied to fuel mileage. Might be that the Nissan system is more intrusive than others though? Would be most curious to hear from others running in to this.
I think lead acid still makes since except where space and weight concerns are paramount. The faster charging of lithium is actually a pretty big bonus too for us since we rarely if ever are hooked up to power while camping - their ability to take maximum charging amperage right up to ~99% SOC or so makes solar charging much more efficient.
Footprint is about 10" X 6" and about 11" tall IIRC. Weight it about 35 lbs.
Yes, I'm curious about how this will work out too!
calicamper
Expedition Leader
Good info. My boat project was due to space in original small battery location. I ended up doing fiberglass work. Two group 24's ahh 1986 days..
I started to look into the fancy stuff but the charge nature as you point out can pose interesting challenges. Especially with really dumb basic alternator gear.
The boat is 9000lbs and 12ft wide weight wasnt a problem ha!!
Lead acid old tech is great in some use cases it works and is cheap.
I started to look into the fancy stuff but the charge nature as you point out can pose interesting challenges. Especially with really dumb basic alternator gear.
The boat is 9000lbs and 12ft wide weight wasnt a problem ha!!
Lead acid old tech is great in some use cases it works and is cheap.
CoyoteThistle
Adventurer
Whoa, that's some serious battery capacity! Look forward to seeing your setup.
Kind of surprising how little info there is on how to really make lithium work - boaters are way ahead of the RV crowd it seems but it's still not widely adopted technology. For anyone interested, the most comprehensive discussion (by far) related to using DIY lithium for house batteries is here.
Not too much new to report on the battery. I have been getting the solar panel out and charging it up. It's basically full now (took about 1,100 Watt-hr or 80+ amps). For some reason the solar charger is "seeing" the battery voltage at about 0.2v more than the battery monitor or my multimeter is seeing. Not sure what's going on there. Just as the pack was getting up to full charge and I discovered this, it got cloudy so I shut it down for the day. :squint:
On other fronts, been making some good progress on some interior bits, including covering the battery compartment. Made some slots for all the wires to pass through and a window.
Got it painted and in today.
Not super pretty but it's inside a cabinet so I won't stress it. Window is so I can see the status-indicating LED's on all the stuff down there without opening things up.
Also been having fun with the miter saw and aluminum angle and channel. Using it to cover up the exposed honeycomb on all the cabinets and such inside. It came out pretty good. Here's one of the cabinet doors:
and The cabinet face:
Came out okay. Still need to glue it all in. Guessing I'll use epoxy (maybe the Six10 stuff in a tube).
Got the vents for the fridge in
and a start on the table
Hoping for some weather more conducive to epoxy work to make some progress on the roof and slide-up.
matt
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Anton2k3
Adventurer
Hey matt,
Great build you have going here. I'm really interested in your battery set up, and still trying to get my head around lifepo4 battery requirements. As I understand it, the battery chargers must be turned off once the required voltage is reached, is that correct? If so, how are you controlling all of the charging sources to do this? Are you charging from an alternator too?
What BMS are you using? is it monitor or management system?
So many questions...but i'll start with those!
Cheers,
Anthony
Great build you have going here. I'm really interested in your battery set up, and still trying to get my head around lifepo4 battery requirements. As I understand it, the battery chargers must be turned off once the required voltage is reached, is that correct? If so, how are you controlling all of the charging sources to do this? Are you charging from an alternator too?
What BMS are you using? is it monitor or management system?
So many questions...but i'll start with those!
Cheers,
Anthony
CoyoteThistle
Adventurer
Thanks Anthony!
Yes, there's a lot to get one's head around on this subject and I'm certainly no expert. I have done many, many hours of research and study trying to understand it. Frankly I still don't get it all but I think some experimentation now will help fill in the gaps.
Anyway, yeah, major aspects of the system that are different from lead acid are protecting the battery from overcharging and stopping charging when the battery is full (i.e., no float charge). Undercharge is a concern too because you can permanently kill a lifepo4 if you discharge it to 0% (whereas a lead acid will be damaged but recoverable).
Ultimate protection from over/under charge comes from the BMS. The BMS I'm using is from Clean Power Auto. They focus mainly on electric vehicles but they have a "House Power BMS" that is for house batteries. It is made to work with the sense boards (which they also make) that attach to each cell and thus provides "cell level protection" - that is if any of the four cells hits 3.65v or 2.6v the BMS will drop power to the main solenoid which disconnects everything except the BMS itself. This is the fail safe protection and should only ever kick in if (1) lots of other stuff goes wrong or (2) one cell is at a significantly different SOC than the others.
Those BMS fail safe protection levels (14.6v and 10.4v) are higher and lower than you ever really want to take the battery though. The BMS has warning level triggers too - 3.6v (14.4v) and 2.9v (11.6). These can be used to trigger an alarm or a solenoid which can disconnect chargers (high voltage trigger) or loads (low voltage trigger). In my case I didn't use them though.
For low voltage protection I am using a Victron Battery Protect. All loads (except the BMS and battery monitor) connect through this. I currently have it set to disconnect at 12.0v. I have the low voltage alarm on the battery monitor (Victron BMV-700) set to buzz at 13.0v - which is about 10% SOC - I shouldn't be going below this level really.
The high voltage protection is complicated, lets see if I can describe it. The Victron Cyrix Li-ct battery combiner protects from overcharging from the alternator. With my "smart" alternator circuit disabled, I'm getting a constant ~14.5v from the alternator - high enough to kill the battery if left unprotected. The Li-ct has a BMS trigger circuit that will disconnect from the alternator when given a signal. I'm using the relay built in to the BMV-700 and have it set to disconnect when the lithium battery gets to 14.1v and re-connect at 13.2v (13.3v may be better). This protection circuit also goes to a regular old 30amp relay that the solar charge goes through. So when the lithium battery gets to 14.1v (95%+ SOC), both the combiner relay and solar relay should open and stop all charging. The battery will drop to it's fully charged resting voltage of around 13.3v. If it starts discharging and gets down to 13.2 volts, the relays will close and either the alternator or solar panels will charge it up again. In effect what this is doing is eliminating "float" charging. I haven't seen anyone use the BMV-700 relay for this and I haven't tested it yet but in theory it looks like a good way to charge correctly with a "dumb" alternator.
I have the solar controller (another Victron piece of kit) set to absorption at 14.2v and float at 13.2v (this essentially disables float charging since bulk charging mode will kick in before the battery gets down to 13.2v). With these settings it should safely work without the BMV-700 relay in the loop. I may pull the 30amp relay at some point since it does draw about 0.4amps when closed.
Anyway, hope that kind of makes sense. As you might be able to tell, I'm having fun geeking out on this but I'm still learning and just starting to test it all out. Some of this may not work as expected! At the very least, I may need to tweak some of the voltage cutoffs as I test things out. I'll surely update as I learn more! Happy to answer any other questions or if someone sees a problem with the logic of this setup, I'm all ears!
matt
Anton2k3
Adventurer
wow, great setup...I get all of that. The problem I have is that clean power auto no longer sell BMS modules to joe public! Bit of a nightmare, so i'm trying to figure out if I can do this without a BMS, or try and find one thats as good as the minibms.
Regarding the alternator, are you not concerned about cooking it when charging the bank from low level? The bank will suck in full alternator capacity for hours on end, as the guy points out in his comprehensive tutorial thread. Or, will your design simply cut it in and out enough that it won't be a problem? Did you consider installing an alternator regulator which you could custom programme to lifepo4 settings? I'm not sure how to make it work with a starter battery if I do that...seems its a one or the other solution. Maybe I could ditch the starter battery and run off pure lifepo4 bank.
So reading your piece again, it seems you're not really using the BMS for anything other than for cell voltage issue bank cut off? Is the attainable with anything else?
I've just re-read again, man its a clever solution to utilise the BMV to trigger high voltage relay. Looking forward to seeing if this solution works. Still confused about the alternator charging bit though, will it not just take the bank straight over the 14.1v limit and trip straight away as soon as the engine is started?
Regarding the alternator, are you not concerned about cooking it when charging the bank from low level? The bank will suck in full alternator capacity for hours on end, as the guy points out in his comprehensive tutorial thread. Or, will your design simply cut it in and out enough that it won't be a problem? Did you consider installing an alternator regulator which you could custom programme to lifepo4 settings? I'm not sure how to make it work with a starter battery if I do that...seems its a one or the other solution. Maybe I could ditch the starter battery and run off pure lifepo4 bank.
So reading your piece again, it seems you're not really using the BMS for anything other than for cell voltage issue bank cut off? Is the attainable with anything else?
I've just re-read again, man its a clever solution to utilise the BMV to trigger high voltage relay. Looking forward to seeing if this solution works. Still confused about the alternator charging bit though, will it not just take the bank straight over the 14.1v limit and trip straight away as soon as the engine is started?
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CoyoteThistle
Adventurer
Wow, I just got my stuff from clean power auto a month and a half ago. Must have been one of the last lucky ones. That really sucks as it's a slick and affordable set up. And yes, the BMS as I have it hooked up is only doing the cell level monitoring and super-danger-zone shutdown based on individual cell voltages. All the other monitoring is done at bank voltage.
I've seen arguments that if you very carefully balance the cells in the bank to start with, cell level monitoring isn't critical as long as your charging voltages are well regulated and you don't do any super deep discharges. I tend to buy this argument but getting the setup to do the super careful balancing was more expensive than just getting the (now unavailable) BMS.
Have you looked at Elite Power Solutions? They have cell boards and a BMS. Their website though is light on technical details. Would probably take a phone call to see how it might work.
Have you looked at the Sterling battery-battery chargers? They seem to work for people but I didn't dig too deep in to the details. Neat part of this thing is that it limits current so you don't fry your alternator!
Other thing that might be worth a look is the Victron BMS 12/200. It's made to work with Victron Cells and their BMS but might work as a stand alone too? I couldn't find one for sale in the states a couple months ago but now PKYS sells it (that's where I got most of my Victron stuff). Would be very interested if you learn anything or anyone else has any experience with this. Neat part of this thing is that it limits current so you don't fry your alternator!
Which brings me to your next question - yes, I am worried about frying my alternator!! As of my very early testing, there seems to be a circuit in my truck that is regulating current from the alternator to some set level above what the truck is using (sensor on the ground wire from the battery measures draw). If I leave this circuit/sensor intact it looks like I'll get ~17amps which is pretty slow but at least no fear of alternator damage. I'm going to try disconnecting the circuit and see what happens. Some people claim that most modern alternators have temperature protection built in - they will regulate down their current to keep from overheating. I have some anecdotal evidence to suggest this is true on my truck but 'll have to do some testing. I think temp protection circuits are less common in boat alternators so there is more concern in that arena of frying alternators.
Yeah adding an external programmable regulator does seem problematic for integrating with a vehicles existing system. I would seriously consider going with a single lithium bank and ditching the starter battery if I had a permanently mounted camper. Even almost dead, a lithium battery can provide plenty of juice to turn a starter motor. Carry along one of those little jump start boxes as a backup and be done with it.
I've seen arguments that if you very carefully balance the cells in the bank to start with, cell level monitoring isn't critical as long as your charging voltages are well regulated and you don't do any super deep discharges. I tend to buy this argument but getting the setup to do the super careful balancing was more expensive than just getting the (now unavailable) BMS.
Have you looked at Elite Power Solutions? They have cell boards and a BMS. Their website though is light on technical details. Would probably take a phone call to see how it might work.
Have you looked at the Sterling battery-battery chargers? They seem to work for people but I didn't dig too deep in to the details. Neat part of this thing is that it limits current so you don't fry your alternator!
Other thing that might be worth a look is the Victron BMS 12/200. It's made to work with Victron Cells and their BMS but might work as a stand alone too? I couldn't find one for sale in the states a couple months ago but now PKYS sells it (that's where I got most of my Victron stuff). Would be very interested if you learn anything or anyone else has any experience with this. Neat part of this thing is that it limits current so you don't fry your alternator!
Which brings me to your next question - yes, I am worried about frying my alternator!! As of my very early testing, there seems to be a circuit in my truck that is regulating current from the alternator to some set level above what the truck is using (sensor on the ground wire from the battery measures draw). If I leave this circuit/sensor intact it looks like I'll get ~17amps which is pretty slow but at least no fear of alternator damage. I'm going to try disconnecting the circuit and see what happens. Some people claim that most modern alternators have temperature protection built in - they will regulate down their current to keep from overheating. I have some anecdotal evidence to suggest this is true on my truck but 'll have to do some testing. I think temp protection circuits are less common in boat alternators so there is more concern in that arena of frying alternators.
Yeah adding an external programmable regulator does seem problematic for integrating with a vehicles existing system. I would seriously consider going with a single lithium bank and ditching the starter battery if I had a permanently mounted camper. Even almost dead, a lithium battery can provide plenty of juice to turn a starter motor. Carry along one of those little jump start boxes as a backup and be done with it.
CoyoteThistle
Adventurer
It seems like it would doesn't it! And I have no idea why it doesn't!! Somehow the BMV is really reading the battery voltage and not the charging voltage. This honestly seems like voodoo to me but I'm sure there is an explanation.
Anton2k3
Adventurer
thanks for all the comprehensive replies! So how far have you gone with testing now? Are you happy the system works as it should?
I've looked at orion jr bms, but its pretty expensive for what it does. I've got sterling battery to battery charger in our current van, and had spec'd an alternator to battery charger for the new build. However, there are no Lifepo4 charging profile options, and so far have found no evidence that the charging profiles can be customised with the remote controller. Not sure if anyone as info to confirm or deny this though? It would be an easy way to protect the alternator though.
I've looked at orion jr bms, but its pretty expensive for what it does. I've got sterling battery to battery charger in our current van, and had spec'd an alternator to battery charger for the new build. However, there are no Lifepo4 charging profile options, and so far have found no evidence that the charging profiles can be customised with the remote controller. Not sure if anyone as info to confirm or deny this though? It would be an easy way to protect the alternator though.