Finally found a LiFePO4 BMS with Low-temp Charging Protection

[Dzl]

Allright so I am thinking of ordering this BMS to work together with my 4*200ah cells.
I will be using it in a RV and it will charge through 300 watt victron mppt solar charger and through the vehicle alternator when driving.

Normally it is recommended to use a charge booster (battery to battery charger) to charge using the vehicle alternator. If not, your alternator might be using itself 100% to try to charge the battery asap. Therefore they recommend a 30a charge booster (So that the battery charger at maximum 30a and not using the alternator for 100%).

If you are referring to a DC-DC charger like this one (I've heard devices like this called DC-DC charger, and Battery to Battery charger, but not charge booster so maybe you mean something different than what I'm thinking of) than I think you are understanding correctly that one of its primary purposes is limiting current so as not to overtax the alternator, additionally it will have a charge profile for lithium batteries, and can step up or step down the voltage.

I would respectfully disagree with @HRTKD using a DC-DC charger (or some other form of regulation) between vehicle charging system and lithium batteries is somewhere between strongly recommended and a requirement in most situations from what I've read. From what I've heard, In the olden days of lead acid, the system was naturally self limiting due to the battery chemistry, but this is not the case with lithium, so to prevent a stock alternator from running flat-out and overheating, a DC-DC charger or an external regulator is needed.

Now my question is:
- Can you set the maximum charge rate on this BMS (using bluetooth).
If that would be possible, I guess the charge booster (in this case more limiter) is not needed. Am I right?

I'm pretty sure the BMS can't and shouldn't be used in the way you are hoping. I am only modestly informed on the topic, but I am not aware of any BMS capable of current limiting. Overcurrent protection, even if adjustable is a simple on/off. Further, its not clear (to me) whether BMS overcurrent protection is a battery protection feature or a BMS self protection feature, or both.

 

[Sgt Raven]

I don't know motorhomes. I know pickup trucks. You would have to measure both the amps and the volts going into your house batteries from the alternator feed. Discharge the house batteries as low as you're comfortable with and then fire up the engine while measuring the circuit.

I'm still not convinced that you'll burn out your alternator. I suspect that the motorhome has protections on that circuit to prevent it from pulling too many amps from the alternator.

Maybe, maybe not....

 

[HRTKD]

Maybe, maybe not....

That wasn't quite a real world test. First, there should have been some air flow over the alternator to assist with cooling. Most vehicles will have some natural air flow at highway speeds and the radiator fan kicks in when needed, also providing air flow. Second, connecting the alternator directly to the battery isn't how the system on my truck works. The 7 pin charge circuit is current limited. It will never exceed 30 amps. Very few owners of 2017+ Ford Super Duty trucks are seeing more than 20 amps.

Using a DC-DC charger - especially one that understands the charge profile for a LiFePO4 battery - is never wrong. I'm just not convinced that it's always necessary.

 

[Sgt Raven]

That wasn't quite a real world test. First, there should have been some air flow over the alternator to assist with cooling. Most vehicles will have some natural air flow at highway speeds and the radiator fan kicks in when needed, also providing air flow. Second, connecting the alternator directly to the battery isn't how the system on my truck works. The 7 pin charge circuit is current limited. It will never exceed 30 amps. Very few owners of 2017+ Ford Super Duty trucks are seeing more than 20 amps.

Using a DC-DC charger - especially one that understands the charge profile for a LiFePO4 battery - is never wrong. I'm just not convinced that it's always necessary.

Anyone who is relying on their 7 pin RV cable to charge their trailer battery, doesn't understand how little charge they get from it. Look how they do it in Australia. They use a Anderson SB50 plugs and HD cables to charge their trailer batteries. Lots of them use a DC-DC charger, too. A SB50 is rated for up to 120A. The main purpose of the 7pin charge wire, is to keep the trailer electric brake battery charged up. Any charge sent to the house battery, is a side effect of that.

 

[lmwilco1]

I always wondered why my toyhauler batteries were never charged after either driving or running the truck for a few hours. In my new camper I ran 4G wires to a DC-DC charger to put that problem behind me for good.

 

[Woggs1]

Look what mail-lady (mail-person?) Alejandra brought me today. It has 3 10AWG wires soldered in already. Google tells me that is equivalent to a 5AWG wire, so about 150 Amps.

 

[Woggs1]

Upon closer inspection I see an issue with the middle wire. How does the middle wire conduct negative return power? I don't see any metal connection???? How does this work?


How does that work???

 

[Sgt Raven]

Upon closer inspection I see an issue with the middle wire. How does the middle wire conduct negative return power? I don't see any metal connection???? How does this work?


How does that work??? View attachment 18825View attachment 18826View attachment 18827

From what I've been told, the green is a "solder mask" and there is a copper buss under it. It would be an easy thing to check with a DMM and I can't see anyone working with this stuff that doesn't have a DMM.

 

[Woggs1]

From what I've been told, the green is a "solder mask" and there is a copper buss under it. It would be an easy thing to check with a DMM and I can't see anyone working with this stuff that doesn't have a DMM.

Great idea, I will check it!

 

[Woggs1]

From what I've been told, the green is a "solder mask" and there is a copper buss under it. It would be an easy thing to check with a DMM and I can't see anyone working with this stuff that doesn't have a DMM.

Thanks Raven, you were right!

 

[wvansl]

Thanks for all the comments guys.
Anybody knows how long shipping might take from US to Sweden? (Europe).
And does somebody knows if they are available in Europe?
Here is Sweden we have a really annoying import tax (25% + administration fee of about 10 USD)....

 

[Zil]

They are available in Florida, USA. https://overkillsolar.com/ slight premium over cost from China. Plus, local support is good.

 

[Sgt Raven]

Thanks for all the comments guys.
Anybody knows how long shipping might take from US to Sweden? (Europe).
And does somebody knows if they are available in Europe?
Here is Sweden we have a really annoying import tax (25% + administration fee of about 10 USD)....

Check overkillsolar's Amazon store, it should have prices there.

 

[OverkillSolar]

Check overkillsolar's Amazon store, it should have prices there.

Noooooo check OverkillSolar.com

The center wire does have copper around it. The 120a 3-wire version is a kind of afterthought to the original design.

I am trying to have them tweak the design to better suit our needs. Better connections, more wire size options, more FETs. Im going to have to pay out of pocket for the engineering. Might just redisign the whole thing from scratch in america. But who will manufacture it

 

[Sgt Raven]

Noooooo check OverkillSolar.com

The center wire does have copper around it. The 120a 3-wire version is a kind of afterthought to the original design.

I am trying to have them tweak the design to better suit our needs. Better connections, more wire size options, more FETs. Im going to have to pay out of pocket for the engineering. Might just redesign the whole thing from scratch in America. But who will manufacture it

You have to know going in they will steal your design and undercut you with Clones. Sometimes the Clones are made in the exact same factory. We saw this happen in the Vape world.

 

[OverkillSolar]

You have to know going in they will steal your design and undercut you with Clones. Sometimes the Clones are made in the exact same factory. We saw this happen in the Vape world.

How are they going to undercut me if I already sell their original design

Oh you mean the american version. IDK, we will see.

 

[Sgt Raven]

Better connections, more wire size options, more FETs. Im going to have to pay out of pocket for the engineering.

How are they going to undercut me if I already sell their original design

Oh you mean the american version. IDK, we will see.

What happened in Vaping. Some American Companies took their original designs to be made in China. Their designs were produced and shipped to them here. At the same time, Clones of their designs were made and sold for less, than their MSRP. I'm talking about your special version.

This part of your post

Better connections, more wire size options, more FETs. I'm going to have to pay out of pocket for the engineering.

They will take the Engineering you paid for and sell them through their own systems. Just go in with your eyes wide open.

 

[vtx1029]

Does anyone know if two of these bms’s can be hooked in series to make a 24v battery? I know a 8s bms would have been a better choice but I already have everything

 

[OverkillSolar]

Does anyone know if two of these bms’s can be hooked in series to make a 24v battery? I know a 8s bms would have been a better choice but I already have everything

yes they can, and I also have 8s 100a BMSs available at this time.

 

[vtx1029]

yes they can, and I also have 8s 100a BMSs available at this time.

Awesome thanks much!